On 15 October 2015, the pilot of an experimental, amateur-built Titan Tornado aircraft, registered N4070F, departed Warrenton-Fauquier Airport, Virginia, United States on a private flight through the local region. Approximately 40 minutes into the flight on the return leg to the departure airport, the aircraft sustained a total engine power loss, which required a forced landing onto a roadway near Mitchells, Virginia. The aircraft was substantially damaged during the landing however, the pilot was not injured.

As the accident occurred in the United States, the National Transportation Safety Board (NTSB) was responsible for investigating this accident. As part of its investigation, the NTSB notified the Australian Transport Safety Bureau (ATSB) as the State of Manufacture of the engine. In accordance with clause 5.18 of Annex 13 to the Convention on International Civil Aviation, the ATSB appointed an Accredited Representative to assist the NTSB liaise with the engine manufacturer and initiated an investigation under the Australian Transport Safety Investigation Act 2003.

The ATSB has concluded its Accredited Representative support to the NTSB investigation, case number ERA16LA016. The NTSB is finalising its investigation report which can be found at www.ntsb.gov.

Any enquiries regarding the investigation and report should, in the first instance, be directed to the NTSB.

Safety summary

What happened

At about 1450, near Rawlinna, WA freight train 5PM9 operated by SCT Logistics derailed during a severe storm. There was a combination of 59 vehicles located immediately behind the locomotives. The train broke into two sections, where 39 vehicles had either derailed or overturned, generally to the south side of the track. A fire started within one refrigerated food van about 500 m from the front of the train and later burned itself out. There were no dangerous goods involved in the accident and no fuel spillage.The derailment damaged approximately 550 m of track. There were no physical injuries to the train drivers, but the two relief drivers were badly shaken when the crew van rolled on its side.

What the ATSB found

The ATSB found that the configuration of multiple PBHY ‘High Cube’ vehicles provided a large side surface area that was susceptible to high wind forces. A localised downdraught of cold air in the form of a microburst on the north side (driver side) of the train produced severe winds that were sufficient to initiate the overturning of eight coupled lightly loaded PBHY vehicles. Other laden vehicles, including another eight PBHY vehicles, the crew van and in-line fuel tanker, had progressively derailed and overturned towards the front of the train. These vehicles had derailed through the transference of the rotating force through the couplers, due to rollover of adjacent vehicles.

What's been done as a result

SCT Logistics advised that on 15 December 2015 a rail safety alert was distributed to operations staff advising drivers to slow trains to speeds no greater than 70 km/h when experiencing severe weather conditions involving strong cross winds.

SCT Logistics is also reviewing and amending their Risk Assessment Register – Mainline Operations to include elements of risk to operations due to adverse weather conditions.

The effects of severe weather on safe train operations will be included in a review of driver training modules.

Safety message

This, and similar previous incidents, highlights how rail operators should consider the effects of severe weather conditions involving strong winds and how this can affect the safety of train operations.

Within the geographical regions of their operations, operators should implement risk management strategies to minimise the likelihood of train derailment when severe weather conditions are forecast.

Derailed vehicles looking east

Source: ATSB

The occurrence

SCT Logistics (SCT) train 5PM9 departed Forrestfield (near Perth) on 3 December 2015 and arrived at Kalgoorlie (Figure 1) at 0952^[1] on 4 December.

Weather information^[2] released at 0523 on 4 December 2015 had forecast that severe storms would extend from Kalgoorlie to Forrest, Western Australia. The forecast included damaging winds with a high potential of ‘microbursts’^[3] and the possibility of small hail. Temperatures for the region ranged from 36 °C to 40 °C.

Figure 1: Location

The map illustrates the key locations relevant to the route of train 5PM9. The derailment occurred about 18 km west of Rawlinna.

Source: Base map copyright Australasian Railways Association, annotated by the ATSB.

Train 5PM9 departed Kalgoorlie at 1010 and about 2.5 hours later stopped at Zanthus for a driving crew change. The new driving crew were advised that the air conditioning on lead locomotive SCT 012 had failed. The train departed Zanthus at 1317. While travelling towards Rawlinna, the second driver telephoned the maintenance help desk seeking assistance to rectify the air conditioning failure that saw SCT 012’s cabin temperature rise to 38.8 °C with the windows open.

After departing Naretha at about 1424, the second driver commented to the driver about the lightning and storm to their north that drew closer as the train headed towards Rawlinna.

About five minutes before the accident, the second driver received a call from the maintenance technician who gave options for repairing the air conditioning in the locomotive cabin. The second driver also advised that when he was required to complete safe working paperwork with the windows closed, the cabin temperature would rise to 39.9°C. While the second driver was analysing the air conditioning fault, a gale force northerly wind with heavy rain struck the driver’s side of the locomotive. The drivers said the locomotive lurched violently to the right and left, and it was very noisy with reduced visibility. At the time, the train was travelling at about 94 km/h.

The intensity of the wind was so strong it was forcing rainwater under the (now closed) left side-sliding window into the driver’s cabin. As the driver was reaching for a cloth to stop the water, he felt a bump in the train. Suspecting that he may have knocked the automatic brake handle while reaching for the cloth, he looked at the driver’s console and noticed a flash of the vigilance light.

Both drivers felt a large pull on the train and thought it may have come apart. When seeing the illuminated sanding light on the console and a loss of air, the driver bailed off ^[4] the independent brake to stretch the train and minimise the risk of derailed trailing vehicles overrunning the crew van and locomotives.

The second driver looked in the rear view mirror, and saw rail vehicles derailing and rolling onto their sides. The first vehicles to derail appeared to be about 10 vehicles behind the locomotives, with subsequent vehicles progressively derailing towards the front of the train. As the train slowed, it jerked backwards and forwards. All the vehicles derailed to the south of the track, including the crew van and in-line fuel tanker coupled immediately behind locomotive SCT 008 (Figure 2).

Figure 2: Leading end of train showing overturned crew van and trailing vehicles.

Looking in the direction of travel, this photo shows how the vehicles progressively derailed towards the front of the train while rolling onto their sides south of the track. Source: ATSB

Data extracted from the locomotives confirmed a steady rise in the airflow volume through the brake pipe indicating that vehicles had separated from the leading end of the train. This lasted for about 26 seconds until the train stopped and the driver moved the throttle to idle. The locomotives had travelled a distance of 472 m from when the airflow volume started to increase. The front of the train came to a stop near the 1420.750 km^[5].

Post occurrence

At about 1451, the second driver made an emergency call on the ICE (In-cab Communications Equipment) radio to the Australian Rail Track Corporation (ARTC) Network Control Officer (NCO) located at Mile End, South Australia. He advised the NCO that train 5PM9 had derailed and that the crew van and in-line fuel tanker had rolled onto their sides and there was a fire in the pileup of vehicles (Figure 3) about 500 m behind the crew van.

At about 1458, the NCO contacted the infrastructure maintainer that was carrying out a track inspection between Rawlinna and Naretha. The NCO requested the maintainer go to the derailment location to assist the train crew. At this time, the maintainer was about 110 km from where the train derailed.

At about 1459, the NCO contacted two signal maintenance workers who were maintaining a point machine at the eastern end of the Rawlinna crossing loop to assist the train crew.

When the drivers alighted the locomotive they described the wind at gale force with heavy rain. They quickly went back with a fire extinguisher to check on the wellbeing of the two drivers that were resting in the crew van. One of the drivers climbed onto the side of the overturned crew van and kicked the jammed doors of the vestibule and kitchen open. He found both drivers were uninjured but badly shaken and assisted their exit onto the ground and to shelter in the cabin of the trailing locomotive.

Figure 3: Panoramic view of derailed vehicles and containers

The second driver moved quickly to shut down the generator set that was still powering appliances in the overturned crew van. He then disconnected the fuel lines on the in-line fuel tanker to ensure there was no spillage of diesel.

It was evident that the fire had started in a refrigerated wagon containing food products, probably initiating at the refrigeration unit. The fire was inaccessible for the crew to safely extinguish. The fire subsequently extinguished naturally without spreading to other freight.

The second driver continued to check the train and contacted the ARTC Train Transit Manager (TTM) to update him of the current situation as well as requesting advice about placing protection at each end of the train. At about 1652, he informed the TTM that the rear of the train was protected. The train control graph shows that at 1754 the drivers placed protection at the front of the train. In the meantime, the driver contacted SCT operations centre providing further information about the derailment and state of all drivers.

The signal maintainers, who had already arrived at the derailment site, confirmed that the train crew were uninjured and later contacted the NCO to provided further details of location, vehicles derailed, and the train crew condition. The maintainer also advised that the weather had abated with occasional light rain and winds.

At about 1707, the infrastructure maintainer arrived on site to assist the train crew and assess track damage. Later, with the assistance of the signal maintainers, the crew of train 5PM9 were transported by road to Naretha. At Naretha, they met with Pacific National train 5PS6 that transported the SCT crew back to Kalgoorlie.

On 6 December 2015, the removal of derailed vehicles and track restoration works commenced. To assist the recovery effort and to reduce the amount of time before the resumption of east-west services, track maintenance crews constructed a deviation track on the northern side of the original track alignment to bypass the derailment site. The deviation track opened for traffic about 4 days later on 10 December 2015. On 10 February 2016, with rehabilitation works complete and the new track laid, the deviation track was removed and services recommenced over the original alignment.

__________

1. The 24 hour clock is used in this report to describe the local time of day, Western Standard Time (WST)
2. Weather information provided by the Early Warning Network (EWN) is an online weather warning subscription service.
3. A microburst is a small column of exceptionally intense and localised sinking air that results in a violent outrush of air at the ground.
4. Bail off is a term used to describe the action of: 1) preventing the locomotive(s) brakes from applying automatically during a train brake application, or 2) releasing the locomotive(s) independent braking during a train brake application.
5. Distance in rail kilometres from the reference point located at Coonamia, South Australia.

Sources and submissions

Sources of information

The sources of information during the investigation included:

• SCT Logistics
• The Australian Rail Track Corporation
• The Australian Bureau of Meteorology
• The Early Warning Network (EWN) weather warning subscription service.
• The drivers of train 5PM9.

References

ATSB Investigation: 2006012 - Derailment of Train 3DA2K – Tarcoola, South Australia, 1 November 2006.

ATSB Investigation: RO-2008-013 - Derailment of train 2PM6 – near Loongana, Western Australia, 11 November 2008.

ATSB Investigation: RO-2010-012 - Derailment of freight train 4DA2 near Cadney Park, South Australia, 25 November 2010.

ATSB Investigation: RO-2014-006 - Derailment of freight train 3MP9 near Malbooma, SA on 10 April 2014.

Australian Standard AS 7509.2, Railway Rolling Stock - Dynamic Behaviour - Part 2: Freight Rolling Stock.

Australian Industry and Skills Committee, TLIC4023 - Operate train with due consideration of route conditions

Australian Industry and Skills Committee, TLIF4110 - Responding to abnormal situations and emergencies when driving a train

Australasian Railways Association, Railways of Australia Map.

Rail Industry Safety and Standards Board (RISSB) – Australian Code of Practice – Loading of Rail Freight – May 2011.

RISSB Glossary of Railway Terminology ver1 December 2010.

RMIT University, An Experimental Investigation of Aerodynamic Properties for Rollover Risk of Double Stacked Container Wagons.

Satellite images from Himawari-8 operated by the Japan Meteorological Agency (JMA) and sourced from the Australian Bureau of Meteorology.

Submissions

Under Part 4, Division 2 (Investigation Reports), Section 26 of the Transport Safety Investigation Act 2003 (the Act), the Australian Transport Safety Bureau (ATSB) may provide a draft report, on a confidential basis, to any person whom the ATSB considers appropriate. Section 26 (1) (a) of the Act allows a person receiving a draft report to make submissions to the ATSB about the draft report.

Submissions were received from SCT Logistics, the Australian Rail Track Corporation and ONRSR. The submissions were reviewed and where considered appropriate, the text of the report was amended accordingly.

Findings

From the evidence available, the following findings are made with respect to the derailment of train 5PM9 near Rawlinna, Western Australia on 4 December 2015. These findings should not be read as apportioning blame or liability to any particular organisation or individual.

Safety issues, or system problems, are highlighted in bold to emphasise their importance. A safety issue is an event or condition that increases safety risk and (a) can reasonably be regarded as having the potential to adversely affect the safety of future operations, and (b) is a characteristic of an organisation or a system, rather than a characteristic of a specific individual, or characteristic of an operating environment at a specific point in time.

Contributing factors

• The PBHY ‘High Cube’ vehicles provided a large side surface area that was susceptible to high wind forces and subsequent wheel unloading.
• It is probable that the downdraught of cold air in the form of a microburst near Rawlinna, WA created wind speeds significantly higher than the winds recorded at the ARTC weather stations located at Rawlinna and Zanthus.
• The combined effects of atmospheric wind, induced wind due to train movement and vehicle body roll, was very likely to have initiated the overturning of the lightly loaded, coupled group of PBHY vehicles.
• It is likely that the transference of rotating force through the couplers, due to rollover of adjacent vehicles, contributed to the rollover of the loaded PBHY vehicles, crew van and in-line fuel tanker.

Other factors that increased risk

• The SCT Logistics Risk Assessment Register – Mainline Operations was not updated in accordance with the SCT safety management system and did not identify and assess extreme weather hazards that could affect safe operations of their intermodal freight train services.
• The SCT Logistics locomotive drivers received no formal training with respect to understanding severe weather events, the associated derailment risk, and mitigation strategies to minimise the likelihood of derailment.

Other findings

• Rail vehicles that are loaded will generally display a greater resistance to wheel unloading and wind induced rollover.

Safety analysis

SCT response to severe weather information

At about 0915 (ESDT) on 4 December 2015, the SCT Operations Centre in Victoria received a EWN weather forecast report from the ARTC Train Transit Manager advising severe weather conditions for the Kalgoorlie to Forrest track section.

The table attached to the EWN weather forecast included severe weather alerts and comments at key locations along the rail corridor commencing at Kalgoorlie and east to Cootamundra, NSW. The table listed four colour-coded properties that included three alert levels ranging from amber (heightened alert) to black (severe network disruption) (Table 3). The green colour code signifies no threats for a given region.

Table 3: Part table showing severe weather warnings between Kalgoorlie and Forrest issued on 4 December 2015 by the Early Warning Network

The EWN weather forecast also contained weather forecasts for the next two days, Saturday 5 December to Monday 7 December 2015. These three days contained high and extreme temperature alerts, however no severe wind alerts were forecast for this period.

The forecast of severe storms on 4 December stating ‘damaging wind gusts are the main threats due to the high potential of microbursts’ was the prompt for SCT to remain vigilant about the weather threats affecting the safety of their trains travelling through those regions.

RISSB Rail Hazard Register

The Rail Industry Safety and Standards Board (RISSB) is owned by its rail industry members and is responsible for the development and management of rail industry standards, rules, codes of practice and guidelines.

The RISSB has developed a Rail Hazards Register for committees and development groups engaged in the process of developing new RISSB standards.

The items within the RISSB hazards register were compiled with the extensive assistance of rail industry member expertise and also notes that the itemised list is not exhaustive.

The RISSB hazards register was published on17 March 2015. For the specific risk of vehicles overturning, 11 related factors were shown for derailment (5.28). The register also contains references to another RISSB document that uses fault tree diagrams to describe foreseeable hazards and controls. (Table 4).

Table 4: RISSB Rail Hazard Register - Section 5: for Rolling stock, Vehicles overturning (extract)

Items listed in Table 4 that were relevant to the derailment of 5PM9 are 5.28.1.1, 5.28.1.4 and 5.28.1.5.

SCT Logistics is a RISSB member and has ready access to the register for guidance in the management and maintenance of their risk assessment documentation.

SCT Logistics assessment of weather risks

The SCT Logistics Risk Assessment Register – Mainline Operations was compiled in October 2009. At this time, SCT was transitioning from an operator that contracted the services of a ‘hook and pull [1]’ provider to one that purchased a new locomotive fleet, and directly employed and trained their own train crews.

The SCT risk assessment register identified nine main groups of hazards and risks including:

• Derailment, Train to train collision, Train to object collision, Train collision with infrastructure, Train to motor vehicle collision at level crossing, Fire on train, Explosion on train, Rolling stock runaway and Worker falls from train.

Considering previous similar derailments investigated by the ATSB (noted above) and the derailment of SCT train 3MP9 near Malbooma, SA [2] in 2014, SCT were aware of the derailments and operational hazards associated with weather related events.

SCT’s awareness of weather event risks were not reflected in the risk register and did not identify, assess or record any weather related hazards that could potentially affect the safety of its train operations.

Additionally, although risk management and mitigation notes in SCT’s risk assessment register state that reviews and updates will occur when required or at least annually, the last recorded update to the register was about three years before the derailment of 5PM9 near Rawlinna, WA.

Driver training

SCT contracts Registered Training Organisations (RTO) for the delivery of training for their train crews. The training packages adopted by the RTO’s are developed by the Transport and Logistics Training Skills Council (TILSC)[3].

A review of qualifications achieved by SCT driving crews show two TILSC modules that were likely to include training elements about the awareness of specific weather conditions that may affect the safety of train operations. The modules were titled Responding to abnormal situations and emergencies when driving a train (TLIF4110) and Operate train with due consideration of route conditions (TLIC4023).

An examination of the TILSC documentation shows them to be a framework of qualifications which generally reference a client organisation’s documented procedures and instructions. For example, TLIF4110 includes two elements referring to the identification and response to abnormal situations.

1. Identify abnormal situations and emergencies when driving a train.

1.2.   Implications of abnormal situations and emergencies are evaluated in accordance with workplace requirements, and safe working requirements and procedures.

1.3.   Hazards are identified, risks are assessed, and risk control measures are implemented.

2. Respond to abnormal situations when driving a train.

2.1.   Abnormal situations are responded to in accordance with organisational procedures, received instructions from relevant personnel, regulatory requirements and emergency response plan, as required.

2.2.   Responsibilities are fulfilled in accordance with organisational procedures, and safe working and/or regulatory requirements.

2.4.   Information is provided to relevant personnel as requested in accordance with regulatory and organisational procedures.

In each case, the performance criteria is generalised and refers to information that should be included within individual organisational procedures. Consequently, the RTO would require the organisational procedures to ensure that specific organisational needs are combined within the driver training modules.

Extreme weather events such as damaging winds, rain and flooding, are conditions that a driver may be required to identify and respond to ensure safety of train operations. Experienced train drivers are generally aware of the effects of wind on their train, however train handling in extreme weather was not included within TLI training or SCT documents.

Before the derailment of train 5PM9, SCT had not developed procedures defining the effects of extreme weather events related to the operation of their freight train services. Consequently, SCT locomotive drivers did not receive formal training with respect to understanding severe weather events, the associated risk of these events, and risk mitigation strategies to minimise the likelihood of train derailment.

--------

[1]     Rolling stock and locomotives are owned by SCT Logistics however; a third party contracts train crews and train operating functions.

[2]     RO-2014-006 Derailment of freight train 3MP9 near Malbooma, SA on 10 April 2014

[3]     The Transport and Logistics Industry Skills Council is one of 11 independent, not-for-profit Industry Skills Councils established by the Australian Government.

Context

Location

Rawlinna is located on the interstate rail network, approximately 375 rail km east of Kalgoorlie, Western Australia (Figure 1). The derailment occurred about 18 km west of Rawlinna near the 1421 km mark.

Track information

The ARTC manages the railway where the derailment occurred, with the movement of rail traffic controlled from the ARTC’s Network Control Centre West located at Mile End in South Australia.

The standard gauge (1435 mm) track at the derailment location consisted of 47 kg/m rail fastened to concrete sleepers by resilient clips. The track formation comprised sand/clay based soil, topped with a capping layer and overlaid with ballast to a nominal design depth of 250 mm – forming the track bed. The track bed supported prestressed concrete sleepers spaced nominally at 667 mm centres.

Approaching from Kalgoorlie, the track through the derailment site was tangent^[6] and the terrain was slightly undulating. The track gradient leading to the derailment site transitioned from a gentle rising grade^[7], and was level through the location of the derailment. The maximum track speed was 115 km/h.

Train and crew of 5PM9

Train 5PM9 was a freight service operated by SCT between Perth and Melbourne. The train consisted of two locomotives (SCT012 leading and SCT008 trailing) hauling an in-line fuel tanker, a crew van and 57 freight vehicles. The train was 1390.7 m in length and had a trailing mass of 3060 t.

The crew consisted of four qualified drivers who had commenced duty at Forrestfield, near Perth on 3 December. The plan was for the drivers to work the train in pairs, operating in rotating relay shifts through to Adelaide, South Australia.

The driver and co-driver in charge at the time of derailment had extensive operations and train driving experience. They were assessed as fit for duty in accordance with the requirements of the National Standard for Health Assessment of Rail Safety Workers.

On-site inspection and examination of train data found there was no anomaly in the train speed, train handling, rolling stock condition, or operational performance leading up to the derailment.

No dangerous goods were listed on the consignment sheet for train 5PM9, however there was extensive loss of containment of foodstuffs because of the derailment.

Weather

Weather Forecast

Subscribers to the Early Warning Network (EWN) are provided with a daily Weather Condition overview that is based on information sourced from the Australian Bureau of Meteorology (BoM). The EWN overview issued on 4 December 2015 to the ARTC and SCT at 0523 stated:

Yesterday (3/12/2015) across southern Western Australia severe storms produced a gust of 102km/h at Kalgoorlie. Today severe storms will remain likely but will extend east to Forrest from Kalgoorlie. Damaging wind gusts are the main threats due to the high potential of microbursts but some small hail cannot be ruled out. An extreme fire danger is also current today. Tomorrow expect a few showers and storms to continue east of Zanthus with the further chance that some of these may be severe while some showers and rain/thunder may occur around Kalgoorlie tomorrow night.

The forecast also provided a table of warnings at four prime locations, Kalgoorlie, Zanthus, Rawlinna, and Forrest. All locations had forecast wind speeds of between 15-20 km/h and maximum temperatures between 36 °C and 40 °C. The EWN forecast also alerted subscribing organisations about the ‘high chance of severe storms’ for these four locations.

Post event observations

Commencing at about 1230, thunderstorms progressively developed across the forecast area. Radar images had identified strong cells mainly south and southeast of Kalgoorlie. At about 1400, a thunderstorm developed east of the main activity area peaking between 1440 and 1450. The timing of this thunderstorm corresponds with the time that 5PM9 derailed (Figure 4).

Figure 4: Satellite images

Satellite images showing the cloud masses travelling generally in a south-easterly direction near Rawlinna, WA between 2:30 pm and 3:00 pm (WST) Image Source: Satellite images from Himawari-8 operated by the Japan Meteorological Agency (JMA) and sourced from the Bureau of Meteorology.
Annotated by ATSB

At about 1400, the EWN also recorded widespread lightning activity starting at about 40-50 km north of the railway line. The lightning moved slowly in a southerly direction. At about 1440, there was increased intensity near the railway line (Figure 5).

Figure 5: Thunderstorm lightning lifecycle recorded north of Rawlinna, WA – 4 Dec 2015

Lightning strikes are displayed as crosses (ground events) or triangles (cloud events). The strikes are colour coded to indicate changes in the time of strike. Blue indicates 60 minutes prior to the image capture and transition to red indicating 30 minutes prior to the image capture. The image illustrates that lightning strikes had moved slowly in a southerly direction towards the railway line.

Image Source: Map data 2015 Google Imagery 2015 TerraMetrics

The EWN reported ‘lightning tends to occur near the transition between the downdraught and updraught indicating the downdraught would have been close to the railway line. At this time, the likely effect would have been a strong out flow of winds and heavy rainfall that could have caused flash flooding.

Microbursts

Intense local weather conditions can often develop that are difficult to detect on standard synoptic charts. A downdraught of cold air usually causes severe winds in thunderstorms. The BoM describes a localised downdraught as downburst, and if they are less than 4 km across, they are referred to as a microburst (Figure 6). Very severe downdraughts (or microbursts) can produce wind speeds of more than 200 km/h while only affecting areas of up to 1 km wide.

Figure 6: Diagram of thunderstorm downdraught/microburst

Microbursts often have wind gusts in the 90-100 km/h range – but briefly in small geographic areas. The descending air is forced to spread out laterally near the earth’s surface, often creating severe wind squalls with associated dust.

Source: WDRB Meteorologist Jeremy Kappell.

In this instance the EWN reported that: ‘Severe weather produced was most likely microburst winds. Microbursts often have wind gusts in the 90-100 km/h range – but briefly in small geographic areas’.

The descending air is forced to spread out laterally near the earth’s surface, often creating severe wind squalls with associated dust, similar to that experienced by the crew of train 5PM9.

Wind induced lateral forces, especially that acting on the side of a rail vehicle, contributes significantly to body roll and potential vehicle rollover.

The ATSB closely examined the possibility that the severe environmental conditions at the time of the derailment may have led to a vehicle rollover scenario. Similarly, the factors that serve to resist rollover were also examined.

There was no radar coverage in the vicinity of the derailment site however the ARTC have automatic weather stations located at Rawlinna and Zanthus (Figure 1). Data was recorded at both sites, at 10-minute intervals.

Recordings at Zanthus (about 153 km west of the derailment site), showed the maximum wind speed was 72 km/h at 1430 (about 20 minutes before the derailment). The maximum wind speed 10 minutes before and after this time was no greater than 31km/h.

At the time of the derailment (1450), the maximum wind speed recorded at Rawlinna (about 18 km east of the derailment site) was 15 km/h. Twenty minutes after the derailment (1510), the maximum wind speed at was recorded at 43 km/h.

On 4 December 2015, the recorded average wind direction for both locations was NNE.

Considering the weather systems in the area at the time, it is probable that the downdraught of cold air in the form of a microburst created wind speeds significantly higher than those recorded at the Rawlinna and Zanthus weather stations.

Local weather observations

While working about 18 km east of the derailment site, the two signal maintenance workers observed weather squalls approaching from the north and west. After receiving the call from the NCO requesting their assistance for the crew of 5PM9, the maintenance workers stated that the road was ‘very muddy with large puddles from the recent storm, with water still running along the road a couple of kilometres from the derailment site’. When they arrived at the derailment site about 23 minutes later, they said the storm had passed and reported that ‘it was quite still', and later, ‘there was light rain and wind at times, but not strong’.

Track inspections

The ARTC conducts regular on-track inspections by road / rail vehicles. On the 4 December 2015, the ARTC track inspector commenced a routine on-track inspection and travelled west from Forrest, WA.

At about 1200 the inspector travelled through the locality of Rawlinna. About 20 minutes later the inspector passed the 1421 km mark before taking his vehicle off track near the 1427 km mark to allow for the passage of freight train 5PM1.

Following the derailment later that day, the inspector reported that when travelling through the location of the derailment, near the 1421 km mark:

• the temperature was in upper thirties;
• there were no misalignments;
• no track defects or anything unusual was observed.

PBHY ‘High Cube’ vehicles

Figure 7: Diagram of SCT Logistics PBHY ‘High Cube’ class vehicle

Source: SCT Logistics (diagram not to scale)

In 2005, SCT Logistics (SCT) engaged the Royal Melbourne Institute of Technology University (RMIT) to carry out wind tunnel testing on three rail vehicle profiles.^[8] The tests looked at the aerodynamic forces caused by winds that are considered to have a significant influence on vehicle roll-over. Wind tunnel testing determined the relationship between wind angles and the coefficient used to calculate wind force acting on a specific wagon area and shape.

Tests were carried out using 1/15th scale models of a SCT high cube vehicle having a total height of 5590 mm (Figure 7), a ‘high cube’ vehicle with an extra 300 mm added to the roof profile (5890 mm), and a double stacked container well wagon.

The primary objective of the study was to determine if increasing the size of the SCT ‘high cube’ wagon would result in an increased risk of roll-over when compared to commonly used double stacked well wagons. The results of the study also provide the information required for calculating the effects of wind on the wagons involved in the derailment at Rawlinna on 4 December 2015.

Train 5PM9’s consist report shows that the eight PBHY ‘high cube’ vehicles, positioned 13 to 20 behind the locomotive, were unloaded, having a tare weight of 29.60 t each. The total side area of the standard height PBHY vehicle was 105 m² (Figure 8). This configuration is more susceptible to wheel unloading due to wind force. That is, the configuration has a large side surface area, light weight and relatively high centre of side area.

In calculating the percentage of wheel unloading, a simplified method assumes that the vehicle’s centre of mass acts continuously at the centre point between the two rails (that is, the vehicle suspension is rigid and does not permit body roll). For a train travelling at 90 km/h, 100% wheel unloading on a PBHY class of vehicle was calculated to occur when the effective wind speed^[9] is about 80 km/h and acting at an angle of between 60 degrees and 80 degrees relative to the direction of travel.

Figure 8: Vehicle profile and side area showing elements used in the estimation of forces acting on a PBHY vehicle

Consideration of body roll

Under normal operating conditions, a vehicle will oscillate on its bogies and suspension, and external forces such as wind loading can increase vehicle body roll from side to side. The consequence of this movement is the vehicle’s combined centre of mass will also shift from side to side, significantly affecting the calculations for predicted rollover risk due to wind. The magnitude of this movement for the same roll angle will increase as the height of the centre of mass increases above rail level. The critical elements are the roll angle and the height of the centre of mass above the rail level.

In this case, the eight-coupled PBHY vehicles (positioned 13 to 20 behind the locomotive) were not loaded. Considering the PBHY vehicle weights documented in SCT’s manifest report for the train, the combined centre of mass was calculated at 1200 mm above rail level. Table 1 illustrates the calculated results for predicted 100% wheel unloading for different roll angles of vehicle tilt.

Table 1: Wind speed and angle for predicted 100% wheel unloading

Roll angle	Wind speed	Wind Angle[10]
0 degrees	80 km/h	80 – 90 deg
5 degrees	80 km/h	60 – 70 deg
10 degrees	70 km/h	70 – 80 deg
15 degrees	60 km/h	60 – 90 deg

There were also eight loaded PBHY vehicles in the consist at the leading end of the train. These were positioned 5 to 12, immediately behind the crew van and coupled in front of the empty PBHY vehicles mentioned above. The gross mass of these vehicles ranged from 79.33 t to 50.37 t, averaging about 64 tonnes each. The centre of mass for this configuration was calculated as increasing to about 2100 mm above rail level.

As described previously, as the height of the centre of mass above the rail level increases, so too does the lateral shift in centre of mass for the same roll angle.

To identify the influence that centre of mass has on wind induced vehicle rollover, calculations were made with the vehicle’s mass increased to 64 t and the centre of mass raised to 2100 mm above the rail level. All other dimensions remained constant.

Table 2 shows the results for predicted 100% wheel unloading at different roll angles when raising the centre of mass to 2100 mm above rail level.

Table 2: Centre of mass lowered to 2.1 m above rail level

Roll angle	Wind speed	Wind Angle
0 degrees	120 km/h	70 – 80 deg
5 degrees	100 km/h	70 – 80 deg
10 degrees	80 km/h	80 – 90 deg
15 degrees	60 km/h	60 – 80 deg

It is evident from the calculations that higher vehicle mass serves to maintain wheel-rail contact at higher wind speeds. However, if a higher mass vehicle begins to tilt, the higher centre of mass serves to increase the potential for wheel unloading and rollover to occur at lower wind speeds.

Consideration of coupled wagons

The second driver described the first wagons to rollover as appearing about 10 vehicles behind the locomotives, suggesting that the empty wagons were most likely the first to derail. This is consistent with the analysis suggesting that lightly loaded wagons were more susceptible to rollover due to strong wind forces.

In this case however, it was also observed that subsequent wagons progressively rolled over towards the front of the train. That is, the loaded wagons considered less susceptible to rollover also began to roll and derail.

It was noted that the couplers on the PBHY wagons involved in this derailment had a bottom retention shelf. Couplers incorporate a bottom shelf to help prevent a mating coupler from falling to the ground, in the event that it had separated from its wagon due to failure. The intent is to reduce the risk of derailment of the following vehicles due to a dislodged coupler passing beneath a wagon.

However, in the context of this derailment, the bottom shelf coupler ensured the adjacent wagon remained coupled during the rollover sequence. This transferred the rotating force between wagons via the coupler. Consequently, the loaded wagons which may have been less susceptible to rollover from wind induced force, also had a rotating force applied through the couplers. This, in conjunction with the higher centre of mass was likely sufficient to cause the progressive rollover of the loaded wagons towards the front of the train consist.

Similar derailments investigated by the ATSB

In its previous published investigations and reports, the ATSB identified a number of factors that should be considered in reducing a vehicle’s risk of wind-induced rollover. These investigations are:

2006012 Tarcoola, South Australia

On 1 November 2006, the ATSB commenced an investigation into a derailment of a freight train near Tarcoola, South Australia. The final report stated it was possible that the combined effects of strong winds at the time and the vehicles’ natural oscillations while travelling could have been sufficient to initiate overturning and derailment of the vehicles lightly loaded with double stacked freight containers. ATSB Tarcoola Investigation Report – RO2006012

RO-2008-013 Loongana, Western Australia

On Tuesday 11 November 2008, freight train 2PM6 derailed on the Nullarbor Plain approximately 11 km west of Loongana in Western Australia. The investigation found that the combined effects of atmospheric wind and induced wind due to train movement was likely to have been sufficient to initiate the overturning and subsequent derailment of a lightly loaded, double stacked vehicle and other vehicles. ATSB Loongana Investigation Report – RO-2008-013

RO-2010-012 Cadney Park, South Australia

On Thursday 25 November 2010, freight train 4DA2 derailed on the Central-Australia Railway line, about 5 km south of Cadney Park in South Australia. The investigation determined that a severe weather event, with very strong winds associated with thunderstorm activity, were of sufficient magnitude to initiate the rollover and subsequent derailment of a group of lightly loaded double-stacked container vehicles. ATSB Cadney Park Investigation Report – RO-2010-012

Common elements of each investigation found:

• Severe localised wind events generated from the downdraught of cold air in the form of a microburst had created wind speeds significantly higher than forecast,
• the freight vehicles provided large side profiles that were susceptible to high side wind forces,
• the freight vehicles were lightly loaded or carrying empty double stacked containers and,
• the combined effects of atmospheric wind speeds due to train movement and vehicle body roll were most likely sufficient to initiate the overturning of the lightly loaded freight vehicles.

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• 6. Straight track with no applied cant.
  7. A measure of the rate at which the railway is inclined (rising or falling). Gradients are signed +ve (rising) or –ve (falling) in respect of the direction of travel.
  8. Tests were conducted by the School of Aerospace, Mechanical and Manufacturing Engineering at RMIT University for SCT Logistics prior to production of the SCT PBHY High Cube vehicle fleet.
  9. The effective wind speed is a calculation that considers both the speed/direction of the train and the atmospheric wind speed/direction.
  10. Wind angle describes crosswind yaw angle in the direction of train travel. Results were derived from calculations under a range of crosswind yaw angles, from a full head wind to a crosswind (10-degree increments, 0–90 degrees).

 

Safety actions

Additional safety action

Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following proactive safety action in response to this occurrence

Additional safety action taken by SCT Logistics

On 15 December 2015, SCT Logistics issued a safety alert (1215-01) to train crews and rail managers advising that to reduce the risk of a rollover/derailment:

• ‘the combination of high cross winds with trains travelling at track speeds hauling empty wagons may increase the risk of rollover/derailment. These events are extremely difficult to predict with any accuracy in advance of the occurrence’.
• ‘Initial engineering advice is that the risk of rollover/derailment is reduced by decreasing speed’.
• ‘As a precaution, it is recommended that drivers reduce their train speed to 70 km/h when experiencing severe weather conditions involving strong cross winds. Once clear of these conditions normal track speed may be resumed’.

SCT Logistics is also reviewing and amending the Risk Assessment Register – Mainline Operations to include elements of risk to operations due to adverse weather conditions.

The effects of severe weather on safe train operations will be included in a review of driver training modules.

Purpose of safety investigations & publishing information

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2016 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

Discontinuation notice

Section 21 (2) of the Transport Safety Investigation Act 2003 (the Act) empowers the Australian Transport Safety Bureau (ATSB) to discontinue an investigation into a transport safety matter at any time. Section 21 (3) of the Act requires the ATSB to publish a statement setting out the reasons for discontinuing an investigation.

On 19 November 2015, the ATSB was notified of an occurrence involving an Airbus A321, operated by Jetstar Airways. During take-off on 29 October 2015, the flight crew encountered difficulty rotating the aircraft.^[1] A subsequent passenger count found that passengers had not been allocated seats in accordance with the aircraft’s weight and balance requirements, making the aircraft nose heavy.

The ATSB initiated investigation AO-2015-139 on 23 November 2015. Later, the ATSB became aware of three previous events involving the same operator. They were initially investigated as related occurrences as part of AO-2015-139. On 8 September 2017, due to the common factors involved, the ATSB changed the investigation type to a safety issues investigation and it was re‑numbered AI-2015-139. A fifth occurrence, also involving the same operator, was added to the investigation scope in October 2017. A summary of each occurrence is provided at the end of this notice.

On these five separate occasions, and probably others, aircraft were loaded with incorrect passenger distributions or with incorrect passenger numbers used to determine the aircraft's weight and balance. This placed increased operational pressure on flight and cabin crews and, on at least one occasion, adversely affected aircraft performance during take-off. Records show that there were other flights where erroneous passenger loading was discovered before pushback.

Four of the occurrences followed the introduction of a new type of mobile boarding manager (MBM) device used to scan passenger boarding passes and tally the passengers as they boarded. In each case, technical faults and/or erroneous operation of the MBM led to incorrect passenger loading information being provided to flight crews. On two of those occasions, passenger seating allocations were erroneous after a late change of aircraft type.

The ATSB obtained and analysed a large amount of evidence, mostly information from the operator, and interviewed relevant operational personnel during the initial occurrence investigation. However, there were significant and ongoing difficulties in obtaining documentation associated with the project to introduce then new MBM in 2015 and some related matters.

The ATSB strives to use its limited resources for maximum safety benefit and considers that:

• The operator’s organisational context has significantly changed in the 3 years since the investigation began, likely making some of the organisational aspects of the investigation no longer relevant.
• The operator conducted internal safety investigations into the relevant occurrences, and there is significant overlap between the operator’s findings and the ATSB’s provisional findings. The operator has taken action to address those issues in regular consultation with the Civil Aviation Safety Authority.
• The potential safety issues identified to date provide only limited benefit to the greater aviation industry.
• Significant further investigation work would be required to obtain sufficient information to develop provisional investigation findings into safety issues that meet the ATSB’s standards for rigour and defensibility.
• Based on the available information, the risk controls currently in place and the operating context, the ATSB considers any undetected passenger loading problem associated with the identified limitations were very unlikely to have a significant operational impact.

Consequently, the ATSB has discontinued this investigation, and will communicate all additional provisional safety issues and learnings to the operator to reduce future risk. These included limitations in the management of passenger load discrepancies and late aircraft changes, support for concourse staff, management of the then MBM development project,^[2] and the framework for operational change. The investigation information collected and analysed to date remains available as reference material for future ATSB investigations.

Summary of occurrences

• On 16 June 2015 an Airbus A321 registered VH‑VWY was being prepared for a flight from Sydney, New South Wales (NSW), to Hobart, Tasmania, after the scheduled Airbus A320 aircraft became unavailable. After the passengers had boarded, the flight crew identified that the aircraft was loaded too nose heavy for take-off, because the passenger distribution in the cabin was too far forward. To balance the aircraft, the captain ordered the underfloor cargo to be rearranged in a manner that contravened the aircraft’s loading requirements and then continued the planned flight. It was later established that passenger seating allocations had been determined using the seat map for an A320 instead of an A321.
• While processing passenger data after an Airbus A320 registered VH‑VFQ departed Brisbane, Queensland for Newcastle, NSW on 6 October 2015, ground staff discovered a passenger count discrepancy between the final boarding report and the central check-in computer. The flight crew were contacted and an in-flight passenger count found that 15 more passengers were aboard than accounted for during pre-flight planning. This affected the flight crew’s weight and performance calculations, but the minor effect of the increased weight had not been noticed by the crew on take-off. The flight crew amended the calculations prior to approach and landing.
• During a flight from Brisbane to Melbourne, Victoria on 19 October 2015, the crew of an Airbus A320 registered VH‑VQG identified a passenger count discrepancy after a cabin crewmember mentioned the large number of passengers on board to the flight crew. They found that 15 more passengers were aboard than accounted for during pre-flight planning. This affected the flight crew’s weight and performance calculations, but the minor effect of the increased weight had not been noticed by the crew on take-off. The flight crew amended the calculations prior to approach and landing.
• On 29 October 2015, an Airbus A321 registered VH‑VWT was being operated from Melbourne to Perth, Western Australia, after the scheduled Airbus A320 aircraft became unavailable. During take-off, the pilot flying needed significantly more control input than normal to rotate the aircraft. After conducting a passenger count, the crew found that the passenger distribution in the cabin was too far forward, making the aircraft nose heavy. The crew moved six passengers to the rear zone for the remainder of the flight, and amended the weight and balance calculations prior to approach and landing. It was later established that passenger seating allocations had been determined using the seat map for an A320 instead of an A321.
• While processing passenger data after an Airbus A320 registered VH‑VGR departed Sydney for Melbourne on 23 October 2017, ground staff discovered an unusual discrepancy between the provisional and final boarding reports. The flight crew were contacted and an in-flight passenger count found that 22 more passengers were on board than accounted for during pre-flight planning. This affected the flight crew’s weight and performance calculations, but the minor effect of the increased weight had not been noticed by the crew on take-off. The flight crew amended the calculations prior to approach and landing.

 

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[1]     Rotate: lift an aircraft’s nose on take-off.

[2]     The operator reported to the ATSB that it has subsequently introduced a fully redesigned MBM without these issues.

What happened

On 19 November 2015, at about 1455 Eastern Standard Time (EST), a Jabiru J430 aircraft, registered VH-SZQ (SZQ), departed Kingaroy for Goondiwindi, Queensland (Qld). The pilot was the only person on board the private flight.

Earlier that day, the pilot had departed Bundaberg, Qld, where the aircraft engine had undergone maintenance that involved the installation of six new engine cylinder barrels and new piston rings. To ensure that the new cylinders barrels and rings would wear together to form a good seal, the pilot adjusted the engine RPM about every 15 minutes and closely monitored the engine oil pressure, oil temperature, cylinder head temperature (CHT) and exhaust gas temperature (EGT) gauges. Each of the six cylinders had a CHT and EGT sensor installed.

During the cruise at about 6,500 ft, and about 40 minutes after departing Kingaroy, abeam Dunmore, the pilot heard a noise coming from the aircraft engine, which then started to vibrate. The pilot moved the engine throttle control to the idle position, and about 8 seconds later the pilot heard a metallic noise and the engine stopped.

The pilot established the aircraft in a glide and looked for a suitable forced landing area. An airstrip was identified on an electronic world aeronautical chart (WAC), about 4 NM to the left of track, which the pilot initially navigated towards. The pilot was unable to locate the strip and subsequently turned towards a property where they could see people, houses, sheds and a highly visible white road (Figure 1).

Figure 1: Map showing the relevant features of the landing area

Source: Google earth, modified by the ATSB

At about 4,000 ft, the pilot selected a landing area on the road between the houses and a cattle grid (landing area A in Figure 2). SZQ entered on the downwind leg for a left circuit with the final approach towards the west. The pilot identified power lines close to the road (landing area A) and as they were unsure if they crossed the road, selected the road beyond the cattle grid as the land area (landing area B in Figure 2). The pilot completed the downwind and forced landing checks, and left the electrical master switch on to adjust the flap position when required.

At about 50 feet on final approach, the pilot was able to see that the power lines were far enough away from the road of landing area A that they would not be a hazard, and elected to land on the initial landing area selected. The pilot selected full flap and selected the electrical master switch off. The pilot side-slipped^[1] the aircraft to descend quicker. Consequently, the pilot realised that the aircraft’s speed was too fast to land on landing area A and extended to the second landing area, landing area B, and climbed slightly to clear the cattle grid.

The left main landing gear collided with the grid and failed, partially remaining attached to the aircraft. The pilot flared for a landing and the left landing gear dug into the ground and swung the aircraft to the left. The aircraft subsequently collided with a fence and came to a stop about 100 m beyond the cattle grid. The pilot exited the aircraft. The pilot was not injured. The aircraft was substantially damaged.

Figure 2: Diagram representing the circuit pattern and landing areas

Source: Google earth, modified by the ATSB

Pilot comment

The pilot reported that there was thick smoke in the area from fires some distance away. The smoke only affected the horizontal visibility, which was reduced to 6 km. The wind was light with no obvious signs to determine the local wind direction. The temperature was about 28 ⁰C.

The pilot indicated that there was about 12 minutes from when the engine stopped to landing so they had time to analyse the situation. The pilot felt prepared for the forced landing due to the quality of the flight instruction they had received over the years. The pilot reported that no distress call was broadcast to air traffic control.

The pilot reported that prior to the departure from Bundaberg, three circuits were conducted in SZQ. After landing, maintenance personnel inspected the engine and no defects were reported. The pilot did not notice any issues with the engine prior to the failure.

The pilot indicated that the engine total time in service since new was about 756 hours and the time since a bulk strip/rebuild was about 187 hours.

Engine certification

The aircraft was an amateur-built Jabiru J430 and was operated as an experimental aircraft, issued with an experimental certificate. The original equipment manufacturer (OEM) (Jabiru Aircraft) manufactured the aircraft engine. The engine was installed on the aircraft in 2006 at the time of the aircraft build. In 2013 during an engine bulk strip/rebuild, part of the engine was modified with the installation of non-OEM parts resulting in the engine having a unique configuration. As the aircraft was an amateur-built aircraft, the original owner/builder certified for the installation of those parts. The annual inspection of the engine that was conducted prior to the most recent maintenance was conducted at an aircraft maintenance organisation.

Examination of the failed engine at the engine OEM

The failed engine was first examined at the engine OEM, and the Civil Aviation Safety Authority (CASA) was present at the examination. The engine examination identified the reason for the engine failure as a defect in the valve train where the valve head had made contact with the piston, resulting in significant secondary damage to the number 6 piston and cylinder. The three most likely reasons for the failure were identified by CASA as:

• The most recent maintenance event introduced a foreign body or dislodged existing deposits (of carbon) into the system, allowing debris to enter the valve guide/stem resulting in a sticking valve with the subsequent resulting damage of piston to valve contact.
• A sticking number 6 exhaust valve due to reduced clearances between the valve guide/stem. The effect of thermal expansion with non-OEM parts suggests that there is a possibility that original design clearances were not maintained.
• Incorrect clearances within the valve train, resulting in overheating of the valve stem and subsequent necking and cracking at the base of the stem, releasing the valve head into the cylinder. This was assessed as the least likely failure mode, as the levels of observed blackening (overheating) under the rocker covers was considered to be of a degree that would not result in this type of failure.

The examination concluded that the damage observed had the hallmarks of a sticking valve as opposed to a burned valve. Due to the substantial secondary damage destroying most of the evidence, an absolute conclusion could not be made.

Engine examination at the organisation that assisted in the last maintenance on the engine

The organisation that assisted the original owner/builder to bulk strip/rebuild the engine in 2013, and assisted in the most recent maintenance, conducted a second separate examination of the failed engine and noted the following:

•  
  • In 2013, the original owner/builder was provided assistance to bulk strip/rebuild the engine (builder assist bulk strip/rebuild), and some CAMit Aero Engine (CAE) components were installed. This did not include replacing the pistons.
  • The maintenance immediately prior to the engine failure was to fit new CAE cylinder barrels and rings and engine oil inhibiting jets to the intake ports. The new owner (not the original owner/builder) advised that the engine EGT was too high and a different carburettor main fuel jet was installed.
  • The number 6 cylinder failed resulting in the engine stopping.
  • The head of the number 6 exhaust valve was separated from the stem. The valve stem fracture area had severe mechanical damage after its separation but there was no sign of a fatigue fracture. The valve stem was ‘S’ bent in the semi-closed position which would indicate that the valve was not fully open when a possible mechanical collision with the piston was encountered. There was no evidence of significant heat damage to the valve stem (Figure 3).
  • The number 6 piston had completely dis-integrated (Figure 4).

Figure 3: Failed valve head and valve stem

Source: Organisation that assisted in the last maintenance, modified by the ATSB

Figure 4: Recovered parts of the number 6 piston

Source: Organisation that assisted in the last maintenance

• No damage was observed in the valve train such as bent pushrods or damaged rocker arms and adequate clearance was evident in the valve guide.
• It is possible that this engine had been run at a high EGT during maximum power settings since the engine bulk strip/ rebuild.
• Four small pieces of piston skirt were identified and showed signs that they were fractured before the failure. The shiny, peened surface of the fracture faces appeared to indicate cyclic compressive forces to a crack surface during engine operation.
• An inspection of the remaining pistons for evidence of cracks revealed that the five other pistons were also cracked before the engine failed (Figure 5). The cracks all initiate at a stress raiser between the piston skirt and the piston-pin boss web. This stress raiser is machined into the piston during original manufacture for jigging purposes.
• It is most likely that an initial partial failure of the number 6 piston skirt allowed piston debris to lodge between one side of the head of the valve and the valve seat. The next stroke of the piston would then collide with the partially closed valve bending the valve head about the obstruction and generating enough leverage to fracture the head off the valve stem; initiating the final destruction of the cylinder components.
• The high EGTs reported would indicate that detonation^[2] could have been encountered on multiple occasions, which would apply excessive stress at the stress raisers on the piston skirts.

Figure 5: Location of crack detected in all five pistons and example of crack location shown on a piston assembly

Source Organisation that assisted in the last maintenance and CASA, modified by the ATSB

Engine fuel type

The owner reported that the aircraft’s engine had been operated for a period of time on Australian premium unleaded motor spirit (MOGAS) of 95 RON (Research Octane Number). A little while prior to the accident, the owner identified a Jabiru service letter Alcohol, Lead, Compression Ratio: Fuel Guidance JSL007-6 effective date 12 August 2015 and has since only been using Australian aviation gasoline (AVGAS). The service letter is applicable to experimental models, in all models and variants of Jabiru engines and is available from the Jabiru website.

The service letter discussed that when burning a fuel in a piston engine, one of the most important characteristics of the fuel is how much load it can take without detonation. Detonation results in excess temperature and pressure in the engine and in extreme cases can break pistons or cause other damage very quickly. The service letter notes that operators use MOGAS at their own risk and recommends where possible the use of AVGAS. AVGAS is a fuel specifically designed for aircraft use and is subject to very strict documentation and quality assurance. The vast majority of MOGAS blends have lower octane ratings and are therefore less resistant to detonation than AVGAS blends. Many automotive MOGAS blends rely on highly volatile components. During storage, those volatiles can be lost rapidly and the fuel’s performance can degrade significantly in a relatively short period. The service letter notes that it is possible for MOGAS to lose several points from its octane rating while stored, leaving the engine vulnerable to detonation.

The organisation that assisted in the last maintenance indicated that it is possible that light detonation on previous flights may have overstressed the piston at the stress raiser and initiate a fatigue failure of the number 6 piston. The examination of the engine pistons and cylinders did not extend to analysing the combustion deposits for evidence of detonation from previous flights.

Safety action

Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following proactive safety action in response to this occurrence.

Organisation that assisted in the last maintenance

As a result of this occurrence, the organisation that assisted in the last maintenance has advised the ATSB that they are taking the following safety actions:

• All CAE pistons will be modified to minimise the stress raiser that was found in the non-CAE pistons installed on SZQs engine, which will reduce the detonation sensitivity of the pistons.
• A survey of CAE engine owners will be conducted asking questions relating to their engine EGTs to gauge the risk of similar failures.
• Maintenance advice to check all reused pistons for cracks and to modify the stress raiser will become standard practice.
• A test engine has been subjected to similar conditions to enable more accurate failure mode analysis in the future.

Safety message

Pilots should consider the effect an in-flight engine failure at different altitudes has on the time available to manage that failure and identify a suitable forced landing area. In this instance, the pilot had about 12 minutes from the engine failure to landing and was able to consider the options, with enough time to manoeuvre towards a different area (road on property) when the first was not suitable. Regularly updating forced landing options during a flight is particularly important in the event of a time critical situation.

CASA Flight Safety Australia magazine July-August 2007 article Emergency: staying in control is available from the CASA website. The article discusses that reporting an emergency is important when time permits, just in case not everything goes to plan. It is not an inconvenience: it’s what air traffic controllers are trained and qualified to do. They are skilled in dealing with emergencies and providing professional appropriate assistance. Where emergency situations arise, an early in-flight emergency notification will assist in expediting the desired outcome – a safe landing.

The accident also highlights the importance to owners and operators to remain aware of information published by the aircraft and engine manufacturer.

The ATSB has recently published an analysis of reported engine failures: Engine failures and malfunctions in light aeroplanes (AR-2013-107) and is available from the ATSB website. That report found that over the six years between 2009 and 2014, there were 322 engine failures or malfunctions involving single-engine piston aeroplanes up to 800 kg maximum take-off weight. Valve train related fractures were one of the most common failures found.

Aviation Short Investigations Bulletin - Issue 49

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2016 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

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1. Flight manoeuvre where the flight path is inclined downwards and there is a steady loss of height without significant change in airspeed. The longitudinal axis of the aircraft is markedly displaced from the flightpath.
2. Detonation is the uncontrolled explosion of the fuel/air mixture in the combustion chamber of a piston engine cylinder, as distinct from an even and progressive burning. Light to medium detonation may result in some mechanical damage.

 

On 11 November 2015, a Jabiru J160 aircraft, Recreational Aviation Australia (RAAus) registration 19-7549, sustained a partial loss of engine power while enroute from Gunnedah to Cessnock, NSW. Unable to maintain altitude, the pilot elected to divert to Scone aerodrome. However, due to an increasing rate of descent, the pilot conducted an emergency landing into an open field near Scone. The aircraft landed without incident.

Blockage of the wing fuel tank filler vent cap was found during the subsequent inspection of the aircraft fuel system. Partial disassembly of the engine also identified that the number-four cylinder had sustained a broken inlet valve spring.

The Civil Aviation Safety Authority (CASA) commenced an investigation into the circumstances surrounding the engine power loss. CASA requested the technical assistance and oversight of the Australian Transport Safety Bureau (ATSB) in conducting a detailed examination of the occurrence aircraft and its engine. To facilitate this assistance, the ATSB initiated an external investigation under the provisions of the Transport Safety Investigation Act 2003.

A report detailing the examinations and ATSB's findings was provided to CASA, RAAus and the aircraft manufacturer, on 30 May 2016. Enquiries relating to the investigation should be directed to CASA on 131 757.

Figure 1: The engine from Jabiru J160 aircraft, RAAus registration 19-7549

Source: ATSB

 

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The information contained in this web update is released in accordance with section 25 of the Transport Safety Investigation Act 2003 and is derived from the initial investigation of the occurrence. Readers are cautioned that new evidence will become available as the investigation progresses that will enhance the ATSB's understanding of the accident as outlined in this web update. As such, no analysis or findings are included in this update.

 

What happened

Early on the morning of 11 November 2015, a Watco freight train, 4K26, was travelling southbound on the Frenches to East Northam rail line in Western Australia. The train was travelling at about 60 km/hr along a section of track as it approached a left corner, approximately 3 km north of Northam (Figure 1). As the train rounded the corner, the driver saw a hot air balloon in close proximity to the rail tracks. The driver observed that the balloon was low to the ground and inside the rail corridor,^[1] to the left side of the track (Figure 2).

Figure 1: Location of incident with rail line (white) showing direction of travel of the train, the approximate width of the rail corridor (yellow), the direction of travel of the hot air balloon (orange dashed line) and the approximate position of the hot-air balloon (red mark)

Source: Google maps. Modified by ATSB

Figure 2: View from train driver’s cabin as the train rounded the corner with the approximate position of the fences (yellow) either side of the rail line marking the rail corridor

Source: Watco driver’s video, modified by ATSB

The driver estimated that the balloon was approximately 200–300 m in front of the train and applied full service brakes. However, the driver realised there would be insufficient distance for the train to come to a complete stop before passing the balloon. At the same time as applying the brakes, the driver also sounded the train’s horn to warn the balloon that the train was approaching. The driver slowed the train to about 20 km/hr as it passed the balloon.

Figure 3: Picture from the train driver’s cabin just before the train passed the balloon’s position with the approximate position of the fence on the left side (yellow)

Source: Watco driver’s video, modified by ATSB

The Kavanagh Balloons E-300, registered VH-LPG, had taken off east of Northam earlier in the morning for a scenic flight, with the pilot and 16 passengers on board. The pilot’s initial intention was to land in a paddock to the west of the rail line. However, the prevailing wind meant that this was not an option. Instead, they elected to land in the paddock east of the railway line, as the pilot judged it to be the most suitable location in the area. Also, flying to an alternative landing site may have unnecessarily impinged on fuel reserves with the prevailing winds and weather conditions on the morning.

The pilot crossed the rail line from the south-west to the north-east at a height of approximately 50–60 ft, and then descended to around fence top height. The pilot’s intention was to land inside the paddock, just after the fence line at the edge of the rail corridor. As the train came around the corner, the hot air balloon was on descent to the paddock. When the train passed the balloon, the pilot reported the basket was just above fence height and moving away from the rail tracks. The balloon crossed over the fence and landed in the paddock without incident.

Pilot comments

The pilot of the balloon made the following comments in relation to the event:

• Crops in the centre of the paddock and a powerline limited the available landing space, which meant the pilot was landing close to the fence.
• The pilot had landed in the same paddock on many occasions without problems.
• The pilot did not recall hearing the train horn or brakes until the train passed the balloon.

Train driver and observer comments

The train driver and observer made the following additional comments:

• The driver and observer saw the balloon in the distance, however due to the winding track it was not possible to see the location of the balloon relative to the track, until the train came around the bend.
• They were unable to discern the direction of travel of the balloon.
• When they saw the balloon, they believed a collision was likely.
• They suggested that an awareness of the train schedule by balloon operators may avoid a similar event.

Proactive safety action

Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following proactive safety action in response to this occurrence.

Balloon operator

The balloon operator is amending the Low Flying Operations section of their Operations Manual to include the following:

A minimum height of 50 feet shall be maintained when the flight path of the balloon will cause it to cross over a road reserve or rail corridor.

Safety message

Rail corridors are areas where access is strictly controlled as the presence of non-authorised or unexpected personnel and/or vehicles may pose a danger to the safety of rail operations and personnel. Trains require significant distance to come to a complete stop and may not be able to avoid colliding with an obstruction that is on, or near, the tracks.

Operators of balloons or other aircraft that may fly at low-level in the vicinity of rail tracks should consider and minimise risks when operating in these environments.

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2016 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

__________

1. Rail corridor: The rail corridor is defined ‘fence line to fence line’ either side of the rail tracks. Where there is no fence line, the corridor may be defined as a specified distance either side of the outside rail of the rail track. Any person/vehicle inside the rail corridor is considered to be in close proximity to the rail tracks

Safety summary

What happened

On 9 November 2015, Pacific National train 9150 was travelling from Carwarp in north-western Victoria to Melbourne. The train consisted of two locomotives and 20 wagons, of which 19 were loaded with grain.

At about 1532, the train was travelling through Nunga, 8 km south of Ouyen, at about 80 km/h. The train had almost cleared the Janiels Road level crossing when the trailing bogie of the last wagon derailed. The train was brought to a stand about 1,400 m beyond the crossing with no injuries. The track sustained damage from the derailed wagon.

What the ATSB found

The ATSB found that the derailment was a result of the track buckling during the passage of train 9150. Instability in the track was the result of the rails creeping over time and bunching at the crossing, increasing their vulnerability to lateral misalignment in the hot conditions of that day.

It was found that the asset management systems used to identify problematic levels of rail creep (the longitudinal movement of rail over time) did not incorporate algorithms to flag creep that had accumulated over an extended period. There was a reliance on these systems by track maintenance staff, and in the absence of flags for the identification of cumulative creep, the potential for lateral instability at this location was not identified. General inspections did not provide an effective supplementary means of detecting the potential instability.

It was also found that creep management procedures did not ensure that creep defects were identified and managed in a timely manner and prior to the onset of hot weather.

What's been done as a result

V/Line has updated the network standard for the inspection and assessment of lateral stability. It has also included algorithms within the asset management system for the accurate assessment and generation of remediation work orders for cumulative creep, and to correct for fixed points within track, such as level crossings.

In addition, V/Line has amended its procedures to include a requirement to assess and correct rail creep prior to 1 November each year.

Safety message

Asset management systems that provide the primary triggers for rail creep management should consider all criteria that can affect the creep condition and ensure corrective action prior to the onset of extreme weather conditions.

Sources and submissions

Sources of information

• V/Line Pty Ltd
• Pacific National

Submissions

Under Part 4, Division 2 (Investigation Reports), Section 26 of the Transport Safety Investigation Act 2003 (the Act), the Australian Transport Safety Bureau (ATSB) may provide a draft report, on a confidential basis, to any person whom the ATSB considers appropriate. Section 26 (1) (a) of the Act allows a person receiving a draft report to make submissions to the ATSB about the draft report.

A draft of this report was provided to V/Line Pty Ltd, Pacific National and the Locomotive Drivers.

Submissions were received from V/Line Pty Ltd. The submissions were reviewed and where considered appropriate, the text of the report was amended accordingly.

The occurrence

On 9 November 2015 at about 1205, train 9150 loaded with grain departed Carwarp in north-western Victoria destined for Kensington in Melbourne (Figure 1).

Figure 1: The route from Carwarp to Nunga and derailment location relative to Melbourne

Source: Google Earth annotated by Chief Investigator, Transport Safety (Vic)

The train proceeded to Hattah where it was held for about two hours and then to Ouyen where there was a crew change at about 1520. The train departed Ouyen at about 1525. The driver reported that after leaving Ouyen they conducted a successful ‘running test’ of the air brake.

The train was travelling at about 80 km/h as it approached the Janiels Road^[1] level crossing in Nunga, about 8 km south of Ouyen. The crew did not observe anything unusual as they approached and passed over the crossing.

The train had almost cleared the crossing when, at about 1532, the trailing bogie of the last wagon derailed. Following the derailment, the track was observed to be laterally displaced just prior to the crossing (Figure 2).

The derailed wagon disturbed the continuity of the brake pipe, with a reported minor loss of air pressure. Alerted by this, the driver looked back and saw dust and ballast coming from the rear of the train. In response, he made a brake application and the train stopped about 1,400 m beyond the crossing (Figure 3).

Figure 2: Laterally displaced track just prior to the Janiels Road level crossing, looking in the train’s direction of travel.

Source: V/Line annotated by Chief Investigator, Transport Safety (Vic)

Figure 3: The derailed trailing wagon and track damage

Source: Chief Investigator, Transport Safety (Vic)

__________

1. The level crossing accesses Dunkley Road.

Safety issues and actions

The safety issues identified during this investigation are listed in the Findings and Safety issues and actions sections of this report. The Australian Transport Safety Bureau (ATSB) expects that all safety issues identified by the investigation should be addressed by the relevant organisation(s). In addressing those issues, the ATSB prefers to encourage relevant organisation(s) to proactively initiate safety action, rather than to issue formal safety recommendations or safety advisory notices.

Depending on the level of risk of the safety issue, the extent of corrective action taken by the relevant organisation, or the desirability of directing a broad safety message to the rail industry, the ATSB may issue safety recommendations or safety advisory notices as part of the final report.

Descriptions of each safety issue, and any associated safety recommendations, are detailed below. Click the link to read the full safety issue description, including the issue status and any safety action/s taken. Safety issues and actions are updated on this website when safety issue owners provide further information concerning the implementation of safety action.

Rail creep

Safety issue number: RO-2015-022-SI-01

Safety issue description: Asset management systems that were used to identify problematic levels of rail creep did not evaluate nor assess cumulative creep.

Other track inspections

Safety issue number: RO-2015-022-SI-02

Safety issue description: There was no supplementary system of inspection that was effective in identifying rail creep in jointed track. The network placed a high reliance on the asset management system to initiate closer inspection of track potentially affected by creep.

Timeframe for addressing identified rail creep

Safety issue number: RO-2015-022-SI-03

Safety issue description: The procedures for measuring, assessing, and remediating rail creep in spring did not ensure creep defects were addressed in a timely manner and prior to the onset of hot weather. A creep defect identified by the spring measurements was not corrected before the derailment.

Correcting rail creep for fixed points

Safety issue number: RO-2015-022-SI-04

Safety issue description: Asset management systems used to identify problematic levels of rail creep did not correct for fixed points between creep monuments.

Context

Location

Nunga is a sparsely populated area with a mostly flat landscape. The derailment occurred immediately north of the Janiels Road level crossing located 501.142 km^[2] from Melbourne.

Weather

The forecast maximum temperature issued for the area was 35 °C. The maximum recorded temperature at Ouyen on the day of the derailment was 36.1 °C with 12.1 hours of sun, and it is probable that conditions at Nunga were similar.

Track infrastructure

Classification and traffic

The regional rail network, that includes the section of track from Carwarp to Nunga, is managed by V/Line. The track was classified Class 3 meaning it could service freight traffic travelling up to 80 km/h. Freight trains generally travelled empty heading north, and returned loaded travelling south. Passenger traffic was not using this line.

Track construction

Approaching the level crossing, the track was tangent (straight) over flat terrain. It was constructed using 47 kg/m rails supported on base plates and fixed to timber sleepers by dog spikes. Rails were welded into lengths of about 82 m that were joined using fish-plated connections (Figure 4).

Figure 4: Typical track condition at Nunga showing joints, rail fixtures and ballast

Source: Chief Investigator, Transport Safety (Vic)

Site track inspection

On the morning after the derailment an inspection was conducted of about 400 m of track on the approach side (by train 9150) of the Janiels Road level crossing. The weather conditions were similar to the day of the derailment.

Sleepers were in fair condition and the ballast condition and shoulder profile was generally good. Mechanical joints on both rail legs were closed.

Recent track maintenance

The most recent works in the area were conducted in August 2015. Records indicated that tamping was conducted between 496 and 502.5 km on 23-24 August and ballast resurfacing from 28 August. The scope of these works did not include rail adjustment.^[3]

Janiels Road level crossing

The Janiels Road level crossing was unsealed and consisted of a dual-gauge 11 m track panel that incorporated concrete sleepers supporting 47 kg/m rail affixed using resilient fasteners^[4] (Figure 5). Records indicate that the panel was installed in October 2008 as part of the Mildura Rail Corridor upgrade.^[5]

Figure 5: Janiels Road level crossing, upgraded to dual-gauge rail configuration supported on concrete sleepers and affixed using resilient fasteners.

Source: Chief Investigator, Transport Safety (Vic)

Local operational conditions

There was no speed restriction on this section of track at the time of the derailment. This meant that the maximum permitted line speed for train 9150 was 80 km/h.

Lateral stability and the installation of jointed track

Jointed track

Jointed track made of 82 m welded lengths of rail has expansion gaps that provide a nominal range of 12 degrees in rail temperature in which the rail is stress free.

Construction

V/Line standard NIST-2650 Use and Laying of Rail specified procedures to ensure that rail stress remained within the prescribed limits at the extremes of rail temperature. For jointed 82 m lengths of rail, the network standard specified that the gap between rail ends should be fully open (11 mm) when laid at a rail temperature between 25-27 °C, and fully closed (rail ends butted together) when laid at a rail temperature between 37-38 °C. Gap requirements were specified for installation temperatures between these limits, and other procedures prescribed for temperatures outside the 25-38 °C range.

Correctly installed rails would therefore be effectively stress free within the working limits of the expansion gap at rail temperatures of between about 26 and 38 °C. At temperatures below about 26 °C, the contracted rails would be in tension, and at temperatures above 38 °C joints would be expected to be fully closed and the rails in compression.

The temperature range at which jointed rail is stress free can be affected by rail creep, the longitudinal movement of rail over time. Creep can result in rail bunching in some areas and being stretched in others. Bunching results in excess rail through a location, and the lowering of the stress free temperature range.

Rail stress in hot conditions

Rail temperatures in excess of 50 °C in the region are not uncommon. Rail temperatures can typically be 50 per cent more than ambient^[6] or higher, depending on several environmental factors including solar radiation. As a result, in hot weather rail temperatures will normally exceed 38 °C, the nominal upper limit of the stress free temperature range, resulting in rails being in a longitudinally compressed condition. Track stability then relies on rail fastenings and track supporting formations, including ballast, to resist the forces that induce rails to buckle (move laterally) when in compression.

Where there has been creep resulting in the bunching of rail, the rail will enter a state of longitudinal compression at a lower temperature to that intended at installation. The result is that in hot weather these compressive forces will be greater and lateral buckling forces on fixings and track support higher. The potential for the lateral misalignment of rail is therefore increased.

Inspection and other measures for managing lateral stability

Regimes

The condition of track to withstand hot weather is managed in a number of ways, including:

• general inspections
• the management of rail creep
• heat related speed restrictions (WOLO^[7]) and heat patrols.

General inspections

Track inspection requirements and their frequencies are specified in V/Line procedures. For Class 3 track, V/Line procedures specified that track patrols should be conducted weekly. Track patrols could be conducted by road-rail vehicle or front-of-train and were expected to identify the following defects and conditions that may relate to lateral stability:

• lateral misalignments
• poor track geometry
• sharp or flat areas in curves
• track movement.

On this line, track patrol inspections were predominantly by road-rail vehicle.

The most recent track patrol through this location prior to the derailment was conducted by road-rail vehicle on 3 November 2015; no defects were identified.

For Class 3 track, V/Line procedures also specified annual walking inspections that included in their scope the following observable conditions related to lateral stability:

• longitudinal movement (creep) through fastener assemblies
• lateral movement of track and track geometry issues
• rail, weld or joint misalignment
• joints that were frozen or had incorrect gaps
• deficient ballast profile
• poorly consolidated ballast
• wet and/or contaminated ballast
• poor ballast quality
• pumping sleepers, or other signs of poor track support
• poor sleeper/fastening condition.

The most recent walking inspection was recorded as being conducted on 30 September 2015. This inspection did not identify any conditions at the derailment location requiring remedial action.

Management of rail creep

V/Line procedures defined creep as the longitudinal movement of rails in the track, caused by the action of traffic on the line. They described rail creep as typically occurring:

• on grades
• at location where trains brake
• in the direction of predominant track tonnage
• in track with poor condition sleepers, fasteners and anchors.

Rail creep changes the stress condition of the rails and therefore its management over time is a critical part of ensuring track stability. Creep that results in the bunching of rail at a particular location will result in higher compressive forces within the rail. These forces may become extreme in hot weather, and increase the potential for a rail to buckle. This is most likely to occur on the approaches to fixed points, like turnouts and level crossings, against which rail can bunch.

Creep is monitored using permanent trackside points called creep monuments that are typically 1 km apart. V/Line procedures required each creep measurement at each monument to be compared with the previous measurement and also to be assessed for long term accumulation since the creep point was last reset (Figure 6).

Figure 6: V/Line limits for rail creep

	Change in creep since previous measurement	Cumulative gain or loss of rail between adjacent monitoring points (extrapolated to 1000 m)
Priority 1 (C1 Defect)	50 mm or more	100 mm or more
Priority 2 (C2 Defect)	30 mm or more	50 mm or more

Source: V/Line network standard NIPR- 2708

The track maintenance group responsible for the section measured rail creep in the autumn and spring of each year. These measurements were recorded in a centralised asset management system and creep exceedance reports generated. These exceedance reports were then assigned to the section track supervisors for remediation.

The asset management system used by V/Line changed on 1 July 2015. Both the previous and new system had been tailored by V/Line to meet its business requirements. The rules for creep management were the same in each system. Both systems included algorithms for evaluating the ‘creep since previous measurement’ but neither evaluated cumulative creep. When transitioning from the old to new system, the previous two creep measurements (autumn 2015 and spring 2014) were transferred to the new database. Creep data prior to autumn 2014 was not transferred to the new system.

Additional heat-related controls

In hot weather the risk of rail misalignment is elevated. Additional controls to manage this risk took the form of reduced train speeds (WOLO) and heat patrols. For this section of line, WOLO precautions were implemented when temperatures were forecast to exceed 36 °C. This temperature was consistent with or lower than other Australian regional networks and was established in the context of the condition of the network and other network measures for controlling track lateral stability.

The WOLO train speed for this section of track was 65 km/h and generally applied between 1200 and 2000 unless otherwise specified. Notices could also be utilised to prohibit trains from operating.

The forecast temperature on 9 November 2015 was 35 °C and as a result, heat-related controls were not applied. The actual temperature was not significantly different to that forecast. The maximum temperature recorded at Ouyen was 36 °C and the maximum temperature reached at Nunga was likely similar.

Train

Crew

The train crew of two were both based at Maryborough and on this day were rostered to work Train 9150 from Ouyen to their home depot. Both were qualified for their respective duties and had met the medical requirements for their roles.

Consist

Train 9150 consisted of two locomotives, G548 and X44, and 20 grain hopper wagons coded either VHGF or VHHX with a total length of 340.228 m. The X class locomotive (116 t) was being hauled dead (shut down).

The total trailing mass was 1,576 t with 19 wagons loaded and one (the 12th) unloaded due to a defect with its discharge doors. Of the loaded wagons, five wagons were recorded as having a gross mass of 75 t and the remaining wagons being 76 t. The derailed wagon, VHHX 00712D, had a recorded gross mass of 75 t. All recorded wagon masses met the network load restriction requirements.

Post-derailment inspection of the derailed bogie found that, apart from consequential damage related to the derailment, the bogie was in good condition. There were no indications of bogie hunting (instability).

Train operation

The train was being operated at about 80 km/h, consistent with the permitted maximum speed for this section. There was nothing identified in the handling of train 9150 that may have contributed to the derailment.

Similar occurrences

The ATSB has investigated two other train derailments on the Mildura line that occurred in years 2014-2015.

RO-2014-003 – Derailment of grain train 9130 at Emu, Victoria on 12 February 2014

On 12 February 2014 at around 1400, 10 wagons of a loaded grain train travelling south from Birchip to North Geelong derailed at Emu in North Central Victoria. Emu is located about 223 km south of Nunga between Dunolly and St Arnaud. The derailment occurred on the approach to a set of trailable points at the Melbourne end of Emu Loop that was also a short distance from the Emu Road level crossing.

The ATSB investigation concluded that the derailment was the result of the lateral misalignment of the track that developed during the passage of the train in the hot conditions of that day. The points had provided a fixed point against which the rails bunched. It was found that V/Line’s processes for responding to identified rail creep defects did not ensure remedial action before the onset of warmer seasonal conditions.

In response to the safety issue identified in the ATSB investigation, V/Line advised that it had completed its review and update of its track standard for the inspection and assessment of lateral stability and indicated that a plan for implementation of the standard would be completed by October 2016.

RO-2015-029 - Derailment of freight train 9156 at Ouyen, Victoria on 29 December 2015

On 29 December 2015 at around 1700, 12 wagons of a loaded grain train travelling south from Carwarp to Geelong derailed on the north (approach) side of the William Street level crossing in Ouyen. This derailment occurred about 8 km north of Nunga, was heat-related and the subject of an ATSB investigation.

__________

2. Rail-kilometres from a reference point in Melbourne.
3. Rail adjustment is the process of adding, removing or adjusting rail to reduce the risk of track fracturing or buckling at temperature extremes.
4. Pandrol fastclips and e-clips.
5. Upgrade works were conducted in the region during 2008-2009 and included:
   • the installation of dual-gauge level crossing panels with concrete ties
   • tie renewal
   • mud spot removal
   • ballast shoulder rehabilitation
   • rail joint rehabilitation, welded and jointed
   • track surfacing works
   • rail stress and lateral stability management works.
6. Wu Y., Munro P., Rasul M.G., Khan M.M.K., A review of Recent Developments in Rail Temperature Prediction for use in Buckling Studies, RTSA Conference on Railway Engineering, Wellington, 2010.
7. WOLO was a railway telegraph code to notify of heat-related restrictions, and continues to be used in the industry.

Findings

From the evidence available, the following findings are made with respect to the derailment of train 9150 at Nunga, Victoria on 9 November 2015. These findings should not be read as apportioning blame or liability to any particular organisation or individual.

Safety issues, or system problems, are highlighted in bold to emphasise their importance. A safety issue is an event or condition that increases safety risk and (a) can reasonably be regarded as having the potential to adversely affect the safety of future operations, and (b) is a characteristic of an organisation or a system, rather than a characteristic of a specific individual, or characteristic of an operating environment at a specific point in time.

Contributing factors

• Rail creep over a prolonged period resulted in the bunching of rail on the north side of Janiels Road level crossing. This rendered the rails vulnerable to lateral instability in the hot weather of 9 November 2015 and a lateral misalignment developed during the passage of train 9150.
• Asset management systems that were used to identify problematic levels of rail creep did not evaluate nor assess cumulative creep. [Safety Issue]
• There was no supplementary system of inspection that was effective in identifying rail creep in jointed track. The network placed a high reliance on the asset management system to initiate closer inspection of track potentially affected by creep. [Safety Issue]
• The procedures for measuring, assessing and remediating rail creep in spring did not ensure creep defects were addressed in a timely manner and prior to the onset of hot weather. A creep defect identified by the spring measurements was not corrected before the derailment.[Safety Issue]
• The track underwent works in August 2015 that probably made it more susceptible to creep.

Other factors that increased risk

• Asset management systems used to identify problematic levels of rail creep did not correct for fixed points between creep monuments. [Safety Issue]

Safety analysis

Based on available evidence, the ATSB concluded that the derailment originated at a lateral track misalignment (buckle) just north of the Janiels Road level crossing.

The following analysis is focused on the management of rail creep. Rolling stock and driver performance (train handling) were not factors that contributed to the derailment.

Rail creep

Rail is prone to creep in the direction of predominant traffic tonnage, bunching at fixed points such as level crossings and turnouts. This was the scenario present at the Janiels Road level crossing.

The nearest creep monument to the north of the Janiels Road level crossing (501.142 km) was at the 502 km post. The measured values of creep at this monument are shown at Figure 7, with a correction also included to account for the distance to the crossing fixed point.^[8]

Figure 7: Creep measurements for monument at 502 km

	Up (eastern) rail			Down (western) rail
	Creep reading (mm)	Change since previous	Corrected for 1,000 m (mm)	Creep reading (mm)	Change since previous	Corrected for 1,000 m (mm)
2009 autumn[9]	0	0	0	0	0	0
2009 spring	5	5	6	5	5	6
2010 autumn	-10	-15	-12	5	0	6
2010 spring	15	25	17	25	20	29
2011 autumn	15	0	17	50 (25)[10]	25[11]	58 (29)
2011 spring	35	20	41	65 (70)	40[]12]	76 (82)
2012 autumn	33	-2	38	83 (86)	13[13]	97 (100)
2012 spring	30	-3	35	85	-1[14]	99
2013 autumn	50	20	58	95	10	111
2013 spring	45	-5	52	95	0	111
2014 autumn	45	0	52	100	5	116
2014 spring	50	5	58	110	10	128
2015 autumn	55	5	64	120	10	140
2015 spring	95	40	111	150	30	175

Source: Tabulation of V/Line supplied data

In the period from 2011 autumn to 2012 autumn, two creep defects were flagged in the Down rail. As a result and following the 2012 autumn measurements, 40 mm of rail was cut from the rail at the 502.05 km point. There is no record of how the rail was adjusted either side of this point to accommodate the removal of rail and the effect on the rail at Janiels Road is unknown.

By the spring of 2015, cumulative creep on both rails had significantly exceeded defect criteria. However, the system did not flag this exceedance to track supervisors. Neither the previous nor the new asset management systems included algorithms to identify and assess creep that had accumulated since the last creep reset. The asset management systems only compared creep measurements with the previous two readings. As a result, the slow but regular rail creep southward towards the Janiels Road level crossing was not identified for remedial action.

The 2015 spring measurement for the Up rail was sufficient to flag a C2 defect when compared to the previous two readings. However, this measurement had not been processed by the time the derailment occurred.

The system also did not correct the creep measurements to take account of the Janiels Road level crossing acting as a fixed point. Given that the monument was 858 m from the crossing, this correction would not have been significant in this instance. However, in other scenarios, this could result in significant underestimation of potential lateral instability at a fixed point.

Other track inspections

The scope of annual walking inspections included checking that joints were not frozen or had incorrect gaps. However, the consistent assessment of gaps requires inspection within a specific (and known) rail temperature range and it was unlikely that the annual walking inspection would provide a reliable assessment of rail stress condition. The most recent walking inspection through Nunga was undertaken on a warm day with a maximum temperature of about 34 °C. As a result, the rail joints were probably closed during that inspection.

There was no other inspection regime that might have consistently identified changes in rail stress condition at high risk locations. The network placed a high reliance on the asset management system to initiate closer inspection of track potentially affected by creep.

Timeframe for addressing identified creep

The 2015 spring creep measurement in the Up rail met the criteria of a priority 2 defect when compared to the 2015 autumn measurement. The spring creep measurement was made in the days leading up to 27 October 2015 and supplied to the asset management team prior to the procedural deadline of 30 October. Records indicated that this measurement was up-loaded into the asset management system after the derailment and a work order to assess the defect raised on 20 November 2015. The work order specified a ‘latest completion date’ of 29 December 2015 (60 days from 30 October) and under the Job Plan Details it was noted that ‘The assessment must be undertaken within 60 days and in any case prior to 31 October in same year as inspection’. The work order deadlines were contradictory and the 31 October date unachievable given the deadline of 30 October for taking the creep measurements.

Due to lag in the system and the timeframes for completion of each phase, the requirement to complete creep measurements by 30 October meant that remedial action would extend into November and potentially December.

The processes used for responding to a creep defect included:

• checking the creep measurement for accuracy
• if the creep defect was confirmed, checking joints 1 km either side of the creep monument
• as required, releasing rail and making rail adjustments
• recording any rail adjustments and creep resets in the asset management system.

If the full process of creep measurement, assessment, and remedial action had been completed before the 9 November, the derailment would probably have been avoided.

Climate statistics for Ouyen indicate a mean maximum temperature (Figure 8, green graph) for November of 27.4 °C and a maximum recorded temperature (Figure 8, red graph) for November comparable with the summer months of December-February. This suggests that in this district creep related defects should be addressed prior to November.

The ATSB investigation into the derailment at Emu on 12 February 2014 raised the issue of timeliness of response to creep defects.

Figure 8: Climate statistics for Ouyen, showing mean maximum temperatures (green) and highest recorded temperatures (red) by month.

Source: Bureau of Meteorology

Track works

The track between 496 and 502.5 km underwent tamping and ballast resurfacing works in August 2015. This disturbance probably made the track more susceptible to creep. There was an acceleration in rail creep that year leading to the creep between 2015 autumn and 2015 spring (Figure 7) exceeding the C2 (priority 2) defect limit.

Track lateral instability

Rail creep over a long period had led to bunching of rails on the north side of the Janiels Road level crossing. While cumulative rail creep was excessive at the 502 km post, the movement between this post and the crossing was unlikely to have been uniform. It is probable that bunching was most severe closer to the fixed point, the level crossing. The concrete-sleepered dual-gauge panel installed in 2008 would have been a stronger anchor point than the previous timber installation.

The rail creep had led to joint gaps closing at lower temperatures reducing the rail stress free temperature and resulting in higher compressive forces in the rails in hot conditions.

In the ambient and solar conditions of the afternoon of the 9 November 2015, the rail temperature was probably in the mid-50s °C and the rails in a state of severe longitudinal compression. The track-train dynamics generated by the passage of 9150 at 80 km/h, in combination with this compression, resulted in lateral loads that could not be contained by the rail and track support, and the rails buckled.

__________

8. The V/Line standard prescribed that creep measurements be corrected to a nominal 1000 m rail length. For the 502 km, the distance to the level crossing (501.142) is 858 m, resulting in a correction to creep readings of 1000/858.
9. Creep was reset to zero in 2009 at the completion of major rail works.
10. Second readings are shown in brackets.
11. Difference between 2010 spring and first reading in 2011 autumn.
12. Difference between second reading 2011 autumn and first reading 2011 spring, identified in the system as a C2 defect.
13. Difference between second reading 2011 spring and first reading 2012 autumn. The system evaluated the difference between the second reading 2011 autumn and first reading 2012 autumn as 58 mm and flagged a C1 creep defect.
14. Difference between second reading 2012 autumn and the reading 2012 spring.

Purpose of safety investigations & publishing information

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2017 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

What happened

On 12 November 2015, a pilot was mustering cattle in a Robinson R22 helicopter, registered VH-HWJ, at a property about 90 km south of McArthur River Mine, Northern Territory.

At about 1400 Central Standard Time (CST), as the helicopter approached the cattle yards, it descended rapidly and collided with a tree and terrain. The helicopter landed on its side and sustained substantial damage (Figure 1). The accident occurred about 200 m prior to the cattle yards. The pilot sustained serious injuries and was unable to recall the sequence of events.

Figure 1: Accident site showing damage to VH-HWJ

Source: Helicopter operator

Analysis of fractured yoke

The yoke connecting the clutch shaft to the rearward flex plate was found to have fractured at the connection to the shaft (Figure 2). The ATSB conducted analysis to determine whether the yoke failure may have contributed to the accident, or occurred as a result. The analysis found no evidence of fatigue damage in the yoke, and no other signs of pre-existing damage. The helical fracture was consistent with torsional overstress inducing failure in the yoke.

Figure 2: Fracture surfaces

Source: ATSB

Weather

The weather at McArthur River mine was recorded at 1200 and 1530. At 1200, the wind was from 340° at 5 kt and the temperature was 36 °C. At 1530, the wind was from 160° at 4 kt and the temperature was 38 °C. The direction of the helicopter relative to the wind at the time of the accident could not be determined. The ambient temperature at the time of the accident was about 37 °C. Although the influence of the temperature on the accident is unknown, high ambient temperatures adversely affect helicopter performance.

Operator comments

Subsequent to a previous accident, the operator mandated the wearing of helmets for all pilots. The operator commented that although the pilot sustained head injuries, the outcome might have been worse if the pilot had not been wearing a helmet.

ATSB comment

The ATSB was unable to determine the cause of the accident.

Safety message

US military research^[1] analysed helicopter accidents that were at least partially survivable. It found that occupants not wearing a protective helmet were significantly more likely to sustain severe and fatal head injuries. The US National Transportation Safety Board (NTSB) also acknowledged that the use of head protection can reduce the risk of injury and death. The NTSB issued Safety Recommendation A-88-009, recommending that crewmembers of emergency medical services helicopters wear protective equipment including helmets.

The ATSB investigation report (AO-2014-058) into an accident involving a Robinson R22 helicopter where the pilot sustained a serious head injury, reminded pilots and operators to consider the benefit of occupants wearing helmets to reduce the risk of head injury in the event of an emergency landing.

Aviation Short Investigations Bulletin - Issue 48

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2016 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

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1. Crowley, J.S. (1991) Should Helicopter Frequent Flyers Wear Head Protection? A Study of Helmet Effectiveness. Journal of Occupational and Environmental Medicine, 33(7), 766-769.

What happened

On 10 November 2015, at 1200 Eastern Standard Time (EST), a Cessna 208B aircraft, operated as regular public transport Flight 525 by West Wing Aviation, departed Palm Island Airport for Townsville Airport, Queensland. On board were the pilot and eight passengers.

At about 1250 pm, as the aircraft neared Townsville in instrument meteorological conditions (IMC)^[1], air traffic control (ATC) issued the pilot with a runway 07 area navigation (RNAV) instrument approach. The pilot configured the aircraft, and commenced the instrument approach. The pilot reported that approaching the final approach fix,^[2] the aircraft was configured with the second stage (20°) of flap, and a power setting of about 1200 ft/lb of torque, resulting in an airspeed of about 125 kt.

Shortly after, at about 1,000 ft above ground level (AGL), the pilot broke visual,^[3] and selected the third stage of flap (30°) in preparation for landing. However, this selection of flap resulted in a ‘muffled bang’ from outside the aircraft, which the pilot described as sounding like a tyre blow out. The pilot also reported that the aircraft banked ‘violently’ and steeply to the left.

The pilot immediately attempted to reduce the steep angle of bank and regain control by applying opposite (right) aileron. However, the aircraft continued to roll left, with the subsequent secondary aerodynamic effect of yaw to the left.^[4] Descending through about 700 ft, and with the aircraft now travelling at about a 45° angle left of the extended runway centreline and still not responding, the pilot applied full opposite rudder. There was some response from the aircraft to this control input, but the pilot reported it was still not ‘under control’.

The pilot immediately retracted the flaps from 30° to 20°, which resulted in them being able to reduce the angle of bank and regain partial control. The pilot alerted ATC that assistance on the ground might be required after landing.

During this sequence of events, the aircraft had travelled so far off course that the pilot was unable to see the runway even though the aircraft remained in visual conditions. The pilot was able to manoeuvre the aircraft onto an oblique approach and land without further incident. Emergency services followed the aircraft as it was taxied clear of the runway to parking. There were no injuries to those on board, and no damage to the aircraft.

Pre-flight and pre-take-off checks

The pilot reported conducting a thorough daily inspection prior to the first flight of the day. This included fully extending the flaps to check all the eyelets, rods and flap travel. During the pre-take-off checks, the pilot also individually checked each stage of flap to check for correct operation. There were no abnormalities.

Initial post-incident inspection

During the taxi to parking, the pilot fully retracted the flaps. With the flaps flush against the trailing edge of the wing, initially, neither the pilot nor the aircraft maintenance engineer could pinpoint the reason for the control issue. However, when the engineer gave the left flap a shake, it fell freely down, unattached on the inboard side. After removing some wing access panels, the engineering inspection discovered a loose flap bell crank retaining bolt.

The Cessna 208B Flap System

The operator provided the following information (modified by the ATSB).

The Cessna 208B flap system is comprised of both mechanical and electrical components. The cockpit flap control selection lever, operated by the pilot, provides input to the flap switch actuator, which controls the primary flap motor. Allowing the pilot to select any flap position between 0 and 30 degrees, with detents at UP, 10, 20 and FULL down settings. The flap actuator assembly drives a bell crank, through a series of pushrods, connecting rods, interconnecting rods, and other bell cranks.

In the event that the primary flap system fails, there is an independent standby switch and motor.

Figure 1: VH-WZJ inboard aft flap bell crank assembly

Source: Operator, modified by the ATSB

Operator report

The operator conducted both a ‘hard / overweight landing’ inspection and a ‘severe air turbulence or severe manoeuvres’ inspection after the incident. The operator also sought maintenance guidance from the aircraft manufacturer.

The operator advised that a flap bolt had come loose allowing the lower part of the rear aft bell crank to move free. An inspection indicated that the pivot bolt may not have been lubricated for a long period of time.

The aft bell crank as referenced to in (Figure 2) showed that the assembly is secured into location with a single bolt securing into an anchor nut assembly on the bottom. According to the operator, there was no secondary locking system.

Figure 2: Diagram showing the location of the left wing flap inboard aft bell crank assembly

Source: Cessna 208 illustrated parts catalogue, modified by the ATSB

Manufacturer’s (Cessna) recommended maintenance schedule

Reference was made to the Cessna 208 maintenance manual (maintenance manual), chapter 27-50-01 ‘removal and installation procedures' for this component. However, the instructions did not include a recommended torque setting for any hardware in the flap system. Engineers were required to reference a torque setting in chapter 20 of the maintenance manual – the ‘standard practices’ section. The procedures also advised on the requirement for Loctite 242 to be applied to the component.

As a safety measure, the operator checked all other Cessna Caravan aircraft in the fleet. All were found to have the hardware in the flap system correctly torqued.

Independent audit

An independent audit of the operator’s maintenance system did not find any anomalies. All maintenance, relevant airworthiness directives (AD’s) and Cessna service bulletins (SB) had been correctly complied with. All upcoming inspections were also correctly scheduled.

The independent audit noted that there was no maintenance error. However, the audit concluded that there was a causal combination of both the design of the part, and the limitations of the maintenance schedule instructions.

The Civil Aviation Safety Authority’s (CASA) Service Difficulty Report (SDR) system

The ATSB contacted CASA and requested information regarding reports of any similar occurrences to Cessna 208B aircraft. CASA advised that there have been no similar flap hardware failures reported on these aircraft in the last five years (involving Australian aircraft).

Pilot experience and comments

The pilot has in excess of 4,000 hours flying Cessna 208 aircraft.

Once the left flap mechanism had failed, the aircraft was unresponsive to any control input, and it felt like being in a massive crosswind from the right. The right wing was generating a large amount of lift.

The pilot was not aware of the asymmetric flap situation until sometime after landing. The flap indicator had travelled to 30°, so there had been no reason to doubt it.

The pilot suspects that with the right flap extended to 30°, the dynamic pressure generated by the propeller wash must have pushed the broken left flap back up close to the zero flap position, resulting in the asymmetric flap situation.

Safety action

Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following proactive safety action in response to this occurrence.

West wing Aviation

As a result of this occurrence, West Wing Aviation has advised the ATSB that they are taking the following safety actions:

Type of safety action

The reason for the pivot bolt working loose could not be established. However, as a preventative measure the operators approved Maintenance Program has been amended. This amendment included new maintenance actions and new replacement intervals for the affected bell crank, that are additional to the maintenance requirements in the Cessna maintenance schedule tasks.

This included life limits similar to those mandated by Cessna for the primary flap bell crank assembly and replacement at 10,000 landings for:

• bearings fitted to all four aft flap bell cranks
• bearings fitted to the left inboard forward flap bell crank
• all four aft flap bell crank attaching parts and bolts
• left inboard forward flap bell crank attaching parts and bolt.

Aviation Short Investigations Bulletin - Issue 48

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2016 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

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1. Instrument meteorological conditions (IMC) describes weather conditions that require pilots to fly primarily by reference to instruments, and therefore under Instrument Flight Rules (IFR), rather than by outside visual references. Typically, this means flying in cloud or limited visibility.
2. Final approach fix (FAF) is a specified point on a non-precision instrument approach, which identifies the commencement of the final segment.
3. The pilot was able to maintain visibility along the intended flight path within the published circling area.
4. With a lowered wing and no balancing rudder input the aircraft will begin to slip in the direction of the lowered wing, which leads to a yawing motion in the same direction.

Safety summary

What happened

At about 1730 AEDT^[1] on 7 November 2015, the owner-pilot of an Airbus Helicopters (Eurocopter) EC135 T1, registered VH-GKK, departed Breeza, New South Wales, on a private flight to Terrey Hills, New South Wales. The flight was conducted under the visual flight rules and there were two passengers on board.

About 40 km to the south-west of the Liddell mine, the pilot diverted towards the coast, probably after encountering adverse weather conditions. Witnesses in the Laguna area observed the helicopter overfly the Watagan Creek valley in the direction of higher terrain. The helicopter was then observed to return and land in a cleared area in the valley.

After 40 minutes on the ground, the pilot departed to the east towards rising terrain in marginal weather conditions. About seven minutes later and approximately 9 km east of the interim landing site, the helicopter collided with terrain. A search was initiated about 36 hours later. The helicopter wreckage was found at about 1840 on 9 November 2015. The pilot and two passengers were fatally injured.

What the ATSB found

The ATSB found that the pilot departed an interim landing site under the visual flight rules in marginal weather conditions. The pilot likely encountered reduced visibility conditions leading to loss of visual reference leading to the collision with terrain.

The ATSB also found that the fixed, airframe-mounted emergency locator transmitter had been removed and that personal locator beacons which required manual activation were carried instead. While in this accident it did not affect the outcome for the occupants, the lack of activation, combined with the absence of flight notification information, delayed the search and rescue response.

Safety message

Weather-related general aviation accidents remain one of the most significant causes of concern in aviation safety and the following safety messages are key:

• Avoiding deteriorating weather or instrument meteorological conditions (IMC)^[2] requires thorough pre-flight planning, having alternate plans in case of an unexpected deterioration in the weather, and making timely decisions to turn back or divert.
• Pressing on into IMC conditions without a current instrument rating carries a significant risk of encountering reduced visual cues leading to disorientation. This can easily affect any pilot, no matter what their level of experience. In the event of inadvertent entry into IMC, pilots are encouraged to contact air traffic control for assistance.
• ELTs and PLBs are key safety devices that may become inhibited in a crash. In light of their respective limitations, it is worth considering the use of both.

EC135 T1, registered VH-GKK

Source: Supplied. Copyright: Not to be reproduced

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1. Australian Eastern Daylight-saving Time is used in the report and is 11 hours ahead of Coordinated Universal Time (UTC).
2. ‘Instrument meteorological conditions’ (IMC) describes weather conditions that require pilots to fly primarily by reference to instruments, and therefore under Instrument Flight Rules (IFR), rather than by outside visual references. Typically, this means flying in cloud or limited visibility.

 

The occurrence

On 7 November 2015, the owner-pilot of an Airbus Helicopters EC135 T1,^[3] registered VH‑GKK, made arrangements to fly from a private helipad at Terrey Hills, 17 km north of the Sydney Harbour Bridge, to Breeza, 44 km south-west of Tamworth, New South Wales. Based on a direct track, the distance was 146 NM (270 km). The flight was originally intended for the day before, but was reportedly postponed due to severe storm warnings for the Hunter Valley, which was on the direct track.

This was a private flight under the visual flight rules (VFR)^[4] for the pilot and his wife to attend an event near Breeza (Figure 1). They indicated that they might return to Terrey Hills later that day, or possibly the next. The pilot’s wife was also a qualified helicopter pilot.

Figure 1: Area of operation with dashed line representing nominal return track

Source: Background image Google Earth, annotated by ATSB.

The pilot did not submit a flight notification to Air Traffic Services and, as the flight was conducted under the VFR and outside controlled airspace, there was no requirement to do so. There was no record that the pilot accessed aviation-specific meteorological forecasts and reports in preparing for the flight. Given that there were multiple means of access to those products and other sources of weather information, the pilot may have obtained the weather through these sources.

There was limited recorded data available for the flight from Terrey Hills to Breeza. VH-GKK departed Terry Hills sometime after 0940 and arrived at Breeza at about 1100. It was arranged for an acquaintance, who was a documentary filmmaker, to join the pilot and his wife for the return flight. Their return track would take them over the Werris Creek coal mine where their intent was to film the mine and surrounds.

It appears that the pilot was hoping to leave at about 1700 but there was a delay associated with the event. Witnesses recalled that the helicopter lifted off at about 1730 and headed in a south-easterly direction, toward the general location of the mine. The weather at Breeza was warm and sunny, with predominantly clear skies and light winds.

Based on photos recovered from the filmmaker’s camera, the pilot departed at 1735 and tracked to Werris Creek coal mine then southward in the general direction of Terrey Hills. At 1800, air traffic control radar detected the helicopter in the vicinity of the Liddell mine in the Hunter Valley, which was about the halfway point. On initial detection, the helicopter was at 2,800 ft above mean sea level,^[5] before climbing to 3,500 ft as it approached higher terrain. It had an average groundspeed of 116 kt and the pilot was maintaining a consistent track in the general direction of Terrey Hills (The radar data recorded between 1800 and 1821 is depicted in Figure 3).

From 1811, the radar data shows a descent and at 1812, the pilot made a turn to the left to track in a more easterly direction. Shortly after, the radar return dropped out when the helicopter was at 2,700 ft with a groundspeed of 125 kt.

Three minutes later, the helicopter reappeared on radar 13 km south-east of the last position, at 1,900 ft with a groundspeed of 146 kt. The pilot then maintained a consistent south-easterly track in the general direction of Warnervale, located near the coast. A photo taken from inside the helicopter at 1817 (Figure 2), shows that low clouds and darkening skies were being encountered during this time.

The south-easterly track continued for about 6 minutes and covered 25 km until the pilot made a left turn onto an easterly track. At this point the helicopter was at 1,800 ft and in the vicinity of the eastern end of the Watagan Creek valley. The radar return dropped out soon afterwards.

Figure 2: Image of weather conditions recorded at 1817 looking towards the Watagan Mountains

Source: Recovered camera. Copyright: Not to be reproduced.

Figure 3: Radar data (in solid blue line) of the helicopter track on 7 November 2015 before the interim landing with times and accident site

Source: Background image Google Earth, annotated/modified by ATSB

Witnesses reported that the helicopter crossed the valley and continued in an easterly direction, in conditions they described as overcast with low clouds and rain.

At about 1830, witnesses observed the helicopter return to the valley from the east. The pilot landed the helicopter in an open area within the valley in conditions that witnesses reported as including low cloud, reduced visibility and moderate to heavy rain. One of the passengers took photos of this interim landing site, with two pictures showing the weather conditions at 1901 and 1910 respectively (Figure 4 and Figure 5). During the period that the helicopter was on the ground, the available ambient light varied with the overcast conditions and there was low cloud and drizzle in the area.

Figure 4: Image of VH-GKK at the interim landing site at 1901, facing eastward with obscured, rising terrain in the background

Source: Image retrieved from passenger camera. Copyright: Not to be reproduced.

Figure 5: Image of VH-GKK at the interim landing site at 1910

Source: Image retrieved from passenger camera. Copyright: Not to be reproduced.

The witnesses noted that the helicopter remained on the ground for about 40 minutes before departing at about 1915. By 1920, the helicopter was observed over a property to the east of the Watagan Creek valley, tracking east toward timbered, rising terrain. The witness reported that the heavy rain had abated to drizzle and the visibility remained low.

The helicopter reappeared on radar for a couple of returns at 1919:40 and 1919:45, about 2 km east of the interim landing site. Nothing more is known about the helicopter flight path until 1921:41, when it reappears on radar a further 6 km to the east (Figure 6). The pilot then made consecutive right turns to reverse track from a north-easterly to north-westerly direction while climbing from 1,700 ft to 2,100 ft. Radar detection was lost after 1922:50 and there was no further available data about the flight path.

While the flight was intended to reach Terrey Hills that day, it was also understood by relatives of the passengers that it might not return that evening. As a result, the following day, no immediate concerns were raised with authorities despite the fact the pilot and passengers had not arrived at Terrey Hills. The alarm was raised about 36 hours later, after it became apparent that they were overdue. The pilot of the helicopter had not logged a search and rescue time (SARTIME)^[6] with Airservices Australia, nor was a flight note^[7] left with a nominated other.

An aerial search for the missing helicopter began at 0930 on 9 November 2015. The wreckage was located in heavily timbered, hilly terrain within the Watagans National Park later that day. The pilot and the two passengers were fatally injured.

The helicopter had collided with terrain near the top of a ridge on a south-easterly heading and close to the last recorded radar detections at an elevation of 1,340 ft. The time of the accident could not be precisely established but was estimated to have occurred by 1925.

Figure 6: Radar data (solid red line) of the helicopter track after the interim landing with nominal intermediate tracks (dashed white lines) and times

Source: Background image Google Earth, annotated/modified by ATSB.

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3. Since the helicopter was manufactured, the type certificate of the helicopter type was changed from Eurocopter Deutschland GMBH to Airbus Helicopters Deutschland GMBH.
4. Visual flight rules (VFR) are a set of regulations which allow a pilot to operate an aircraft only in weather conditions generally clear enough to allow the pilot to see where the aircraft is going
5. The reported heights are above mean sea level unless otherwise advised.
6. Time nominated by a pilot for the initiation of Search and Rescue action if a report from the pilot has not been received by the nominated unit.
7. Depending on the type of the flight, a formal or informal note that provides basic information in relation to the aircraft, its intended route, destination, occupants and SARTIME.

Context

Pilot information

The pilot was issued with an Australian Private Pilot (Helicopter) Licence in January 1989, following acceptance of a licence issued in the United Kingdom in 1988. At the time of the accident, the pilot held endorsements for two types of piston-engine helicopter and three types of turbine-engine helicopter, including the EC135 type that the pilot was operating.

In 1991, the pilot was issued a Night VFR^[8] Helicopter rating and in 1992, the pilot completed low flying training. Between 2005 and 2008, the pilot was approved by the Civil Aviation Safety Authority (CASA) to give endorsement or conversion training in EC-135 helicopters. The pilot did not hold an instrument rating^[9] and there was no indication that he had sought to obtain one. This limited the pilot to visual flight operations.

The pilot’s logbook recorded a total aeronautical experience of 2,654 hours, which included 1,256 hours on the EC135 helicopter type. This included a total of 5 hours of simulator experience, 7.5 hours instrument flight time, and 8.1 hours in command at night. No night experience was logged since September 2010, so the pilot did not appear to meet the night-VFR recency requirements.

The most recent helicopter flight review was conducted by a CASA Flying Operations Inspector (FOI) in March 2014. This included a pre-flight assessment of the pilot’s interpretation and application of meteorological reports. It also included a bad weather navigation exercise and diversion. The FOI assessed that the pilot performed to a satisfactory standard overall, and displayed average flying skills and a high level of technical knowledge about the helicopter.

The pilot held a Class 2 Civil Aviation Medical Certificate that was due to expire in May 2016. He was required to wear distance vision correction and to have vision correction available for reading. Post-mortem and toxicological examination found no underlying medical disorder likely to lead to incapacitation of the pilot, however the medical examiner could not exclude hypertension as contributing to the accident.

A search of the ATSB database yielded notifications regarding two significant occurrences involving the pilot and VH-GKK: a weather-related event in December 2004 and a wire strike in November 2012. This earlier event is described in a book published by the pilot. As the book relates, the pilot became caught in cloud at low level over water then climbed to a safe altitude to continue in cloud with reference to a GPS^[10] moving map. The pilot advised air traffic services of the situation and sought information about the extent of the weather. Approaching land displayed on the moving map, the pilot slowed down and gradually descended until the coastline became visible. According to the book, to cope with this type of situation the pilot was night-rated and regularly practised flying on instruments, and the helicopter was equipped with an autopilot and instrumentation.

In the wire strike event, the helicopter was damaged and was subsequently operated in that condition for a short duration. This was investigated by CASA, as were other events:

• August 2006: main rotor blade contact with trees resulting in main rotor damage
• May 2012: operations at an aerodrome in close proximity to aircraft on the ground with risk of collision or damage from downwash

Although the pilot disputed the investigation findings, CASA undertook counselling in 2006 and licence suspension in 2013. Following the flight review conducted by a CASA FOI in March 2014, CASA reinstated the pilot’s licence.

The ATSB did not identify a connection between the incident history and the flight into terrain.

Visual flight rules

The basic principle for VFR operations is for pilots to ensure that the flight is conducted in visual meteorological conditions (VMC), which provides for sufficient flight visibility and clearance from cloud. In non-controlled airspace (Class-G) and for operations at/below 1,000 ft above ground level (AGL), the general requirement is for 5,000 m visibility and clearance from cloud.

In the case of helicopters operated below 700 ft AGL, the minimum required visibility can be decreased to 800 m if certain conditions are met. The pilot must be operating during the day only and at a speed that allows adequate opportunity to see any obstructions or air traffic in sufficient time to avoid a collision.

Unless a pilot holds a current instrument or night visual flight rules rating, a departure must not take place unless the estimated time of arrival for the destination (or alternate destination) is at least 10 minutes before last light.^[11] However, the presence of cloud cover or poor visibility, may cause daylight to end at a time earlier than the time stated.

For a night-VFR flight, a pilot must be at or above the lowest safe altitude in conditions that provides at least 5,000 m visibility and specified clearance from cloud. In this case, the weather conditions were not suitable for night VFR so the pilot was restricted to daylight conditions.

Calculations based on an average groundspeed of 120 kt, taken from the approximate departure time from the interim landing site, indicated that an arrival at the Terrey Hills base would have occurred about 15 minutes before last light.

Aviation-specific meteorological forecasts and warnings

Overview

The Bureau of Meteorology (BoM) produces observations, forecasts, warnings and advisories that are essential for safe and efficient aviation operations. For flight planning, aviation users were advised to obtain the applicable aviation meteorological products from Airservices Australia, the official provider of the Aeronautical Information Services. These products could be obtained through:

• Airservices NAIPS Internet Service (free registration required)
• Airservices AVFAX (free registration required)
• Airservices Pilot Briefing Services (free-call telephone)
• Third party websites and apps with access to NAIPS.

In addition, the BoM provided an unofficial copy of aviation meteorological products on their website and nominated a phone number on some forecasts for users requiring more information.

The pilot was not registered to access NAIPS or AVFAX directly and there was no indication that the pilot utilised the Airservices Pilot Briefing Service to obtain weather forecasts or reports on the day of the accident. The pilot did have mobile devices with internet access and was registered to use at least one app that provided aeronautical information sourced from NAIPS. That app did not record any details of the data obtained by a user.

On a ‘Useful data’ sheet dated 2013, the pilot noted the BoM website address and phone numbers as the only entries under the heading of weather. The ATSB did not have information about the pilot’s internet use and there was no record of the pilot calling the BoM on the day of the flight to Breeza.

Before departure from Terrey Hills, the pilot could have used a home computer or mobile device to access aviation forecasts and reports through the app or the BoM website. From then on, wherever there was mobile internet data available, the pilot could have used a mobile device to access weather information.

At the time of the occurrence, the BoM produced three general types of routine forecasts applicable to general aviation: an area forecast for a defined geographical region and aerodrome forecasts (TAF) ^[12] and trend forecasts (not relevant to the occurrence flight) for specified aerodromes/airports. The bureau generally issued these forecasts for a set validity period but would issue an amended forecast if there was a change to the expected weather conditions during the validity period.

The bureau also issued warnings if they became aware of un-forecast deterioration (AIRMET) and if there was significant weather expected (SIGMET). In addition to being available on demand from aeronautical information providers, these warnings were broadcast on relevant air traffic service frequencies.

It is noted that at the time of the occurrence, aviation meteorological forecasts were presented in a textual format. In November 2017, the area forecast was replaced with a Graphical Area Forecast and Grid Point Wind and Temperature Forecasts to make it easier to interpret and use the information.

Following is a summary of the decoded text of the relevant aviation-specific forecasts and warnings issued by the BoM. The times have been converted from UTC to AEDT.^[13]

Area forecasts 7 November 2015

The direct track from Terrey Hills to Breeza and return was within the eastern half of Area 20 which covers north-eastern NSW. On the day of the flight, the initial Area 20 forecast was issued at 0253 and was valid from 0400 to 1600. This was the forecast valid in the period before the pilot’s departure from Terrey Hills.

Between 0400 and 1600, in the eastern half of Area 20, isolated thunderstorms were forecast from 0700 and isolated showers from 1000. There would be areas of broken low cloud and isolated fog/mist but these were expected to clear by 1100. As a surface trough moved up the coast from near Williamtown during the period, broken low cloud and light showers/drizzle were expected to form behind it. This low cloud would be between 1,000 and 3,000 ft AMSL but would lower to 500 ft in showers/drizzle. (There was also other cloud forecast at or above 3,000 ft but this was not relevant to the occurrence.)

For the critical locality of Murrurundi Gap, 53 km south-east of Breeza and close to the direct track, there would initially be broken cloud on the ground but in the period from 0900 to 1100 this would become scattered cloud at 6,000 ft (3,700 ft above ground) with light showers of rain.

The initial area forecast was superseded by an amended forecast issued at 0828, which was itself superseded by an amended forecast issued at 1439. Another amended forecast was issued at 1549, which was the forecast valid for the return flight from Breeza.

In the overviews of all three amended area forecasts, isolated thunderstorms and rain showers were still forecast in the eastern half of the area throughout the period. The areas of broken low cloud that had been forecast to clear by 1100 were now forecast to redevelop after 1700. In the amended forecasts issued at 1439 and 1549, broken low cloud would be expected from the start of the respective validity periods over the sea/coast south of Williamtown Airport (near Newcastle) and in rain showers, and this would extend inland from 1600. From 2100, isolated fog and mist would be expected over land. From 2200, broken cloud would be on the ground at Murrurundi Gap.

Based on the forecast issued at 1549, by the time the pilot departed Breeza at 1730, there would be broken cloud between 1,000 ft and 8,000 ft over the sea and coast south of Williamtown Airport and extending. There would also be broken cloud between 2,000 ft and 5,000 ft with higher scattered cloud over the ranges and slopes that pilot intended to fly over in the latter part of the flight. Thunderstorms and rain showers may also have developed on or near the intended track with associated visibility down to 2,000 m and severe turbulence in the thunderstorm.

Aerodrome forecasts 7 November 2015

The pilot was operating between his private helipad at Terrey Hills and a private property at Breeza, neither of which are served by aerodrome forecasts (TAFs). In the case of such flights, pilots can refer to TAFs for aerodromes in the vicinity of the intended route. As well as providing a more localised forecast, these TAFs can inform contingency planning. The heights referenced in TAFs are heights above the aerodrome reference point (ground).

Although Sydney International Airport is the closest airport to Terrey Hills with a TAF (or equivalent), the TAF for RAAF Base Richmond, located 40 km to the west of the pilot’s helipad, would be a useful reference. Other TAFs of interest for this flight would be for Maitland and Scone aerodromes for the en route phase and Tamworth Airport for the arrival and departure at Breeza.

The TAFs issued early in the day for Richmond forecast light showers of rain and few cloud at 1,000 ft and broken at 2,000 ft. Although the cloud was due to lift after 1300 to 2,500 ft and 3,000 ft respectively, intermittent periods of broken cloud at 1,000 ft with rain showers up to 1500 and after 2000 were forecast.

Amended Richmond TAFs were issued at 1030, 1544, 1609 and 1734. Based on the 1544 and 1609 TAFs that were valid about an hour before the pilot’s intended departure from Breeza, the weather in the Terrey Hills local area could have been light showers of rain with scattered cloud at 1,500 ft and broken cloud at 2,500 ft. From 1700 onwards, there would be temporary periods up to 60 minutes duration where the cloud would be broken at 1,000 ft with rain showers.

The initial TAF for Maitland was issued at 0450 and was valid from 0600 to 1900. The cloud was scattered at 2,000 ft with rain showers. From 1100 onwards, there would be intermittent periods where the cloud would be broken at 1,000 ft with drizzle and visibility reduced to 4,000 m.

An amended Maitland TAF was issued at 1137 and was valid from 1300 to 0100 the next day. The conditions were the same as the initial forecast until 1900 when the intermittent periods would extend to temporary periods. Another amended TAF was issued at 1919 to include a 30% probability of a thunderstorm.

The TAF for Scone was issued at 0451 and was valid from 0600 to 1900. For the periods that the pilot was airborne, the cloud was forecast to be scattered at 1,000 ft and 4,000 ft with light showers of rain.

The TAFs for Tamworth were issued at 0942 and 1535. These were essentially the same and advised of scattered cloud at 5,000 ft and rain showers until 2300, when the cloud would change to ‘few’ at 1,000 ft.

Warnings 7 November 2015

An AIRMET^[14] issued at 1543 indicated that isolated thunderstorms were observed at Richmond, NSW. An amended area forecast was subsequently issued at 1549 as described above.

Forecasts and warnings 6 November 2015

Given it was reported to the ATSB that the pilot intended to conduct the flight the day before but cancelled due to warnings of storms in the Hunter Valley, the ATSB reviewed the relevant forecasts and warnings issued by the BoM for the day before.

The area forecast for Area 20 issued early in the day forecast isolated thunderstorms throughout the area until 1600 when they were expected only in the Hunter Valley and northward. Broken low cloud would be on the ranges/slopes and sea/coast but would clear by 1300. Any isolated fog and mist was to clear by 0900.

For the critical locality of Murrurundi, broken cloud was forecast to be on the ground with light showers of rain until it improved between 1000 and 1200. From 1000 onwards, there would be temporary periods up to 60 minutes duration of thunderstorms with broken cloud on the ground.

The TAFs issued for Richmond forecast possible foggy conditions that would clear by 0900 followed by benign conditions for the rest of the day. For Maitland, Scone, and Tamworth, the morning conditions included a risk of fog, and scattered low cloud with light showers of rain. By late morning, intermittent or temporary periods of thunderstorm activity could be expected at the three locations until evening.

Assessment of the weather conditions

7 November 2015

To assess the weather conditions encountered by the pilot on the return flight to Terrey Hills, the ATSB obtained and integrated the following data:

• helicopter position from radar data
• forecast for Area 20
• weather radar imagery and observations from the BoM
• witnesses in the vicinity of the interim landing site
• private weather station data in vicinity of the interim landing site.

Weather radar images from Lemon Tree Passage (located on the southern shores of Port Stephens) recorded significant rainfall returns over Richmond at 1548. As the thunderstorm moved to the north-east, the weather radar images showed that it developed from a single isolated return into a wide band of rainfall extending 50 km in a north-west / south-east direction.

By 1812, the rain/storm band had moved north-east to be evident 100 km west and south-west of Williamtown Airport. At the same time, the helicopter was identified at a position that is just north of the weather band (Figure 7).

As the rain/storm band continued to move to the north-east, the helicopter moved to the southeast and was identified at 1818 at a position that correlates with the leading edge of the rain/storm band.

By 1822, the leading edge of the rain/storm band had encircled the identified position of the helicopter. At 1830, the rain/storm band was over the Watagan Creek valley location where the pilot landed the helicopter (Figure 8).

Figure 7: Composite weather image and position of VH-GKK at 1812

Source: Background image Geoscience Australia, Weather image Bureau of Meteorology, annotated/modified by ATSB.

Figure 8: Composite weather image and position of VH-GKK at 1830

Source: Background image Geoscience Australia, Weather image Bureau of Meteorology, annotated/modified by ATSB.

Witnesses in the Watagan Creek valley area recalled that on the afternoon of the accident, a storm had approached from the south-east with dark clouds and rain moving in. By 1600 the weather had started to deteriorate further, with low cloud in the valley. Between 1830 and 1845, around the time when the helicopter landed in the valley, the witnesses reported that there was heavy rain and reduced visibility in the area. One witness, who advised he was a pilot, later reported that the conditions did not appear conducive to VFR flight.

By 1912, the intense elements of the rain/storm front had moved away from the interim landing site but there was still light activity to the east and south-east. When the helicopter was last identified at 1922:50, it was in the vicinity of the light precipitation activity that had moved up the coast and adjacent ranges (Figure 9).

Figure 9: Composite weather image 1922-1924 and position of VH-GKK

Source: Background image Geoscience Australia, Weather image Bureau of Meteorology, annotated/modified by ATSB.

The data recorded by a local private weather station situated at the eastern end of the Watagan Creek valley reflected conditions that were conducive to cloud and fog, including fluctuations in ambient light and rainfall throughout the afternoon and early evening. That recorded data also indicated that there was a change in the ambient lighting. Between 1852 and 1909, the ambient lighting improved but by 1915 the lighting had returned to previous, darker conditions and no further improvements in ambient lighting up to, and beyond, the time of the accident were recorded.

Last light for Terrey Hills was calculated as 1954, although the presence of cloud cover or poor visibility will cause daylight to end at a time earlier than the time stated. Pilots are advised to make allowance for this when flight planning or when confronted with such factors when an estimated time of arrival nears the end of daylight. It should be noted that the parameters used in compiling times of last light do not include the nature of the terrain surrounding the location, or the presence of other than a cloudless sky and unlimited visibility at the destination location.

Aircraft and maintenance

The helicopter was powered by twin Turbomeca engines and was configured for seating five people. The helicopter was manufactured in 1999 and was registered in Australia the same year. Since new, the helicopter had been operated for about 1,400 hours.

The aircraft was equipped with all of the required instrumentation for flight under the VFR, Night VFR, and IFR, but was not being maintained to IFR specifications. Since manufacture, the helicopter had been fitted with a 3-axis autopilot and Garmin GNS^[15] 430 and GNS 530 units. These avionics were integrated and provided the capability to navigate IFR conditions in various autopilot modes. The GNS 530 could display terrain information or provide a Terrain Awareness and Warning System (TAWS), depending on the installed hardware and configuration. The status of the unit fitted to VH-GKK was not established.

The helicopter was also equipped with an auxiliary battery providing ground power for camping and photography equipment.

The helicopter was maintained primarily by the owner-pilot who held a CASA instrument of approval to perform and certify specific aspects of maintenance. There were no anomalies identified in the maintenance records.

Following a 12-monthly inspection, the owner-pilot issued a maintenance release in April 2015 for a period of 12 months and 200 hours of operation. No defects were recorded and maintenance due during the validity period was signed off. Since April 2015, some minor work had been recorded in the logbook, including removal of the fixed Emergency Locator Transmitter (ELT).

Two personal locator beacons (PLBs) were on board and both were found at the accident site within their respective cases. The PLBs were an appropriate regulatory substitute for the fixed unit that had been removed prior to the accident. Neither of the PLBs demonstrated evidence of manual or attempted activation.

At the time of the accident, the aircraft had been operating below its maximum gross weight and the centre of gravity was within the flight manual limits.

Wreckage and impact information

Accident site assessment

The helicopter wreckage was distributed in a linear pattern along a distance of approximately 90 m on a heading of 143 degrees magnetic. The first items in the trail were parts from the tail, which indicated that the helicopter entered the tree canopy in a slightly nose up attitude. Tree upper limb damage about 40 metres from the start of the wreckage trail indicated that the helicopter was not banking during entry.

Along the wreckage trail, the trees were about 34 m high and a number of these had upper trunks and branches that were damaged, which was indicative of a relatively level trajectory. As the helicopter passed through the tree canopy, the helicopter cockpit and cabin progressively disintegrated.

All of the helicopter major subassemblies were identified at the accident site. A fragment of one of the main rotor blade tips was found 80 m to the west of the main wreckage along with remnants of tree-top foliage and light branches. There was insufficient evidence to determine how the foliage was dislodged.

The ATSB examined the wreckage and did not identify any pre‑existing aircraft defects that may have contributed to the accident sequence.

Data download

The ATSB recovered various aircraft components with recorded data stored from the accident site. The helicopter was not equipped with a flight data recorder or cockpit voice recorder, nor were they required to be fitted in accordance with Australian regulations. The Garmin GNS 430 and 530 units did not record flight parameters.

The two engine control units recovered from the accident site recorded engine power parameters and related parameters such as collective pitch. To establish the functionality of the engines, the ATSB arranged for the Bureau d'Enquêtes et d'Analyses (BEA) to work with the engine manufacturer in France to download data from the engine control units. This data showed that the engines were operating normally up to the time of the accident. A failure message, typically generated as a result of this type of accident, was recorded at the same time by both units, approximately 7 minutes after electrical power was turned on, prior to departure from the interim landing site.

The warning unit recovered from the accident site monitors the status of critical operating systems and provides warnings in case of abnormalities such as engine fire, fuel low level, battery malfunction, and low main rotor RPM. The ATSB downloaded data from the warning unit and arranged for the data to be decoded by the BEA and another independent agency. There were no anomalous recorded warnings from engine start until the end of the recorded data. At that point, the warning unit recorded autopilot and main rotor RPM decay warnings that were attributed to the collision with terrain.

The data recorded by the engine control units and the warning unit was not as comprehensive as that recorded by a flight data recorder and does not provide sufficient evidence that all of the helicopter systems were operating normally. However, based on the available data, it is almost certain that the engines were operating normally.

Mobile electronic devices

The ATSB recovered three mobile phones, three cameras, and one iPad from the accident site. The pilot’s iPhone was undamaged and had logged the last phone call at 0828 on the morning of the flight. A weather app was installed, but no data was available to indicate usage.

Another iPhone, belonging to the pilot’s wife, was undamaged and logged the last phone and text activity at 0935 on the morning of the flight. The phone belonging to the other passenger was too damaged to recover any data.

The stored data on the cameras was reviewed and images recorded during the return flight were retained and used in developing the sequence of events and weather information. The iPad did not have a SIM card and no information useful to the investigation was identified.

Emergency locator transmitters

Civil Aviation Regulation (CAR) 252(A) requires the carriage of an emergency locator transmitter (ELT) on most flights in Australian airspace. This requirement can be satisfied by an ELT that is mounted on the helicopter and activates automatically when it senses an excessive force, such as a ground impact. An alternative means of compliance is the carriage of a portable personal locator beacon (PLB) that is activated manually.

On activation, an ELT or PLB transmits on two frequencies, one of which can be detected by orbiting satellites that transmit a signal to search and rescue coordinators. The other frequency can be picked up by overhead aircraft for detection and homing in on the activated beacon, or can be used by crews to alert relevant authorities.

The ATSB research report AR-2012-128: A review of the effectiveness of emergency locator transmitters in aviation accidents states that search and rescue personnel were alerted to aviation emergencies in a variety of ways including radio calls and phone calls and that ELT activation accounted for the first notification in only about 15 percent of incidents. To the date of the research report reference, ELT activations have been directly responsible for saving an average of four lives per year.

The research report noted that both fixed ELTs and personal portable beacons have limitations that include degraded signalling capability when the ELT aerial is damaged in a serious accident, and lack of activation when the impact force is not aligned with the orientation of the ELT or when the occupant is unable to activate a PLB due to injury. GPS-equipped ELTs significantly increase the accuracy of positional information and newer ELTs, incorporating 3-axis g-switches may improve the likelihood of activation upon impact. Carriage of a PLB in place of, or as well as a fixed ELT will be of most safety benefit if it is carried on the person.

Additionally, developments in tracking technology now allows for GPS supported or combined GPS/cellular network supported products enabling real time monitoring of an aircraft’s movements, with the provision of scheduled updates to nominated parties and immediate notification in case of an emergency. Automatic alert signals can also be provided in the event of loss of power or sudden change in altitude with the ability to manually activate in the event of an emergency.

Visual flight into Instrument Meteorological Conditions

Accident data

The safety risks of VFR pilots flying from VMC conditions into instrument meteorological conditions (IMC)^[16] are well documented. This has been the focus of numerous ATSB reports and publications, as VFR pilots flying into IMC represent a significant cause of aircraft accidents and fatalities. In 2013, the ATSB Avoidable Accidents series was re-published. One of these publications, the booklet titled Accidents involving Visual Flight Rules pilots in Instrument Meteorological Conditions outlined that:

In the 5 years 2006–2010, there were 72 occurrences of visual flight rules (VFR) pilots flying in instrument meteorological conditions (IMC) reported to the ATSB…About one in ten VFR into IMC events result in a fatal outcome.

Additionally, a study conducted by the United States National Transportation Safety Board (2005) found that ‘about two-thirds of all general aviation accidents that occur in instrument meteorological conditions (IMC) are fatal’.

Wiggins and O’Hare (1995) explained that when pilots are not trained or qualified to fly in IMC and find themselves in these conditions, ‘the result will almost inevitably involve loss of control of the aircraft resulting in a fatal crash’.

Loss of visual cues and spatial disorientation in low visibility conditions

In a discussion of spatial disorientation, Benson (1999) defined the experience as follows:

Spatial disorientation is…[where] the pilot fails to sense correctly the position, motion or attitude of the aircraft or of him/herself [resulting in] errors in perception by the pilot of their position, motion or attitude with respect to their aircraft...

Gibb et al. (2010) explain that seeing the horizon is ‘crucial for orientation of the pilot’s sense of pitch and bank of the aircraft.’ In conditions of low visibility, the horizon may not be visible to the pilot, during which time they can become rapidly disorientated.

Extensive research on spatial disorientation indicates that loss of control will likely occur between 60 seconds (Benson, 1983 in Gibb et al., 2010) and 178 seconds (Newman, 2007) after the loss of visual reference. This is the case even when the aircraft is in straight and level flight at the time vision is lost, and is shorter still if the aircraft is in a turn. Gibb et al. (2010) state that ‘spatial disorientation accidents have fatality rates of 90–91 percent, which indicates how compelling the misperceptions can be’.

Related occurrences

ATSB investigation AO-2008-063 Controlled flight into terrain – Scone, New South Wales on 14 September 2008

On 14 September 2008, a Cessna Aircraft Co. U206A aircraft, registered VH-JDQ, with a pilot and two passengers on board, was on a private flight under the visual flight rules (VFR) from Bankstown, NSW to Archerfield, Qld with a planned stop at Scone, NSW. The aircraft was reported missing when it did not arrive at Archerfield as expected later that day.

Australian Search and Rescue were notified and, during the subsequent search, the wreckage of the aircraft was located the following day on top of a 3,800 ft ridge in rugged terrain, approximately 56 km (30 NM) north-north-east of Scone Airport. All three occupants were fatally injured and the aircraft was destroyed.

The weather in the area at the time of the occurrence was not suitable for VFR flight and included low cloud, rain showers and high winds. Inspection of the accident site indicated that the aircraft was tracking towards Scone prior to impact with terrain.

ATSB investigation AO-2009-077 Visual flight into instrument meteorological conditions – Dorrigo, New South Wales on 9 December 2009

On 9 December 2009, at about 1120 Eastern Daylight-saving Time, the pilot of a Bell Helicopter Company 206L-1 LongRanger, registered VH-MJO, was conducting a visual flight rules fire‑fighting support flight in the area of Dorrigo, New South Wales with one passenger on board. Shortly after takeoff, the pilot encountered reduced visibility conditions due to low cloud. Subsequently, all visual reference with the horizon and the ground was lost. The pilot attempted to land, but the helicopter impacted the ground in an uncontrolled state and with significant vertical force. The passenger was fatally injured and the pilot was seriously injured. The helicopter was seriously damaged.

The investigation found that after the pilot established the hover, the helicopter entered the rapidly fluctuating cloud. The pilot lost visual reference and became spatially disoriented and the helicopter impacted the ground in an uncontrolled state. The at times rapidly-moving fog or low cloud in the vicinity of the helicopter landing area (HLA) increased the risk of visual operations encountering instrument meteorological conditions at the HLA.

ATSB investigation AO-2011-100 VFR flight into dark night conditions – Horsham, Victoria on 15 August 2011

On 15 August 2011, the pilot of a Piper PA-28-180 Cherokee aircraft, registered VH-POJ, was conducting a private flight transporting two passengers from Essendon to Nhill, Victoria under the VFR. The flight was arranged to return the passengers to their home location after medical treatment in Melbourne.

Global Positioning System data recovered from the aircraft indicated that when about 52 km from Nhill, the aircraft conducted a series of manoeuvres followed by a descending right turn. The aircraft subsequently impacted the ground at 1820 Eastern Standard Time, fatally injuring the pilot and one of the passengers. The second passenger later died in hospital as a result of complications from injuries sustained in the accident.

The ATSB found that the pilot landed at Bendigo and accessed a weather forecast before continuing towards Nhill. After recommencing the flight, the pilot probably encountered reduced visibility conditions while approaching Nhill due to low cloud, rain and diminishing daylight, leading to disorientation, loss of control and impact with terrain.

ATSB investigation AO-2016-031 Collision with water – Cape Tribulation, Queensland on 7 April 2016

On 7 April 2016, the pilots of two Robinson R22 helicopters flew from Mossman, Queensland to various fishing locations to the north with a passenger in each helicopter. Late in the afternoon, the pilots commenced the direct return flight to Mossman.

Shortly after passing Cape Tribulation, in dark night conditions, one of the helicopters registered VH-YLY, collided with the sea. The passenger was injured in the accident but was able to reach the shore and notify emergency services. The pilot’s body was not located.

The ATSB found that the pilot, who was only qualified to operate in day-VFR conditions, departed on a night flight and continued towards the destination in deteriorating visibility until inadvertently allowing the helicopter to descend into water.

__________

8. A Night VFR rating permits a pilot to operate a suitably equipped aircraft at night in visual meteorological conditions.
9. Instrument Flight Rules (IFR) permit an aircraft to operate in instrument meteorological conditions (IMC), which have much lower weather minimums than visual flight rules. Procedures and training are significantly more complex as a pilot must demonstrate competency in IMC conditions, while controlling the aircraft solely by reference to instruments. IFR-capable aircraft have greater equipment and maintenance requirements
10. The Global Positioning System (GPS) is a space-based global navigation satellite system (GNSS) that provides location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites.
11. Last light is the time when the centre of the sun is at an angle of 6° below the ideal horizon following sunset. At this time large objects are not definable but may be seen and the brightest stars are visible under clear atmospheric conditions. Last light can also be referred to as the end of evening civil twilight.
12. TAF: a statement of meteorological conditions expected for a specific period of time in the airspace within a radius of 5 NM (9 km) of the aerodrome reference point.
13. Australian Eastern Daylight-saving Time is 11 hours ahead of Coordinated Universal Time (UTC).
14. An AIRMET advice provides pilots with information on the occurrence or expected occurrence of specific meteorological phenomena not included in the area forecast.
15. Global Navigation System incorporating a communications radio, navigation radio and GPS (Global Positioning System) receiver.
16. IMC: weather conditions that require pilots to fly primarily by reference to instruments, and therefore under Instrument Flight Rules (IFR), rather than by outside visual reference. Typically, this means flying in cloud or limited visibility.

Safety analysis

The ATSB did not have access to recorded data that showed the helicopter flight path or key operational parameters, at, or immediately before the collision with terrain. There were no witnesses to, or video of, the accident sequence. As such, the ATSB was reliant on recorded engine parameters and system warnings along with interpretation of aircraft wreckage, the accident site and weather data, to determine the characteristics of the collision with terrain.

The following analysis examines the known flight path and considers elements that may have influenced the decision to depart the interim landing site and continue the flight. The analysis also examines safety considerations associated with VFR pilot decision making and the carriage of emergency locator transmitting devices.

Pre-flight weather assessment

Although the pilot did not have a NAIPS account for access to aviation weather forecasts/reports, the pilot might have accessed equivalent weather information from other sources or referred to available non‑aviation weather information.

Based on the Area 20 forecast and aerodrome forecasts (TAFs) available before the pilot’s departure from Terrey Hills, it would have been apparent that the flight to Breeza and return could be affected by isolated thunderstorms, and low cloud with light showers/drizzle near the coast south of Williamtown. Although the weather for the flight to Breeza was not reported to have presented a problem, the return flight was later in the day and the type of forecast weather was associated with a moist, unstable air mass.

If the Area 20 forecast issued about an hour before the intended departure from Breeza was taken into consideration, it would be apparent that the flight could be affected by isolated thunderstorms, and low cloud south of Williamtown that would have extended inland. The TAFs for aerodromes adjacent to the route were relatively benign, but the TAF for Richmond indicated that the weather in the Terrey Hills area could have temporary periods of low cloud and rain.

The forecasts were generally consistent with the conditions that developed in the area. The thunderstorm-related activity on the pilot’s intended route was more extensive than the isolated descriptor in the forecast might indicate. However, this type of weather was not precluded by the forecast and local conditions across a forecast area will vary.

Collision with terrain

Data downloaded from the engine control and warning units indicated that there was no problem with the operation of the engines or other monitored helicopter systems up to the point of collision with terrain. There was also no radio transmission from the pilot, either heard or recorded, to advise of any problem. This was consistent with examination of the helicopter wreckage and review of the helicopter logbooks that did not identify any airworthiness concerns. Although these items of evidence are not conclusive, it is unlikely that there was a problem with the helicopter.

The ATSB accessed and analysed a variety of sources of meteorological data to ascertain the weather at the time of the accident. There was low cloud, drizzle and reduced visibility in the area. Although the conditions were marginal for VFR, there was likely to be some variability and it was not possible to establish if the weather in the latter stages of the flight allowed the pilot to operate clear of cloud and with a minimum of 800 m visibility, as per the helicopter visual meteorological conditions (VMC) requirements.

The last recorded radar data showed that the pilot conducted a series of right turns with a change of direction from south‑east to north-west. During the turns, the pilot climbed from 1,700 to 2,100 ft, which correlated to an increase in height above terrain from about 350 to 750 ft.

It is almost certain that the pilot made the right turns in response to the weather conditions and it is possible that the pilot lost visual contact with the ground and climbed to ensure that he maintained terrain clearance. Given the weather conditions, at the point the radar returns dropped out, it is unlikely that the pilot was able to remain in VMC. It is possible that pilot was reversing track to return to the interim landing area.

Nothing more is known about the helicopter’s flight path until it collided with terrain shortly afterwards on a south-easterly bearing and close to the last recorded radar position. This bearing and position are consistent with a continuation of the original flight track; however, the ATSB could not determine if that was the pilot’s intention.

In the period from the last recorded radar return prior to the collision with terrain, the pilot descended about 700 ft. The ATSB was unable to determine if the pilot was taking advantage of a break in the cloud to descend visually or trying to descend through cloud to establish visual reference to the ground.

If the pilot had been descending through cloud in order to establish visual reference to the ground, this behaviour may have been consistent with the pilot’s experience in 2004, as related in the book published by the pilot. Although the book related the pilot’s descent in cloud until visual reference was established at low altitude, the context in this case was different. Instead of flying over water and coastline, the pilot was contending with terrain that was undulating, uniformly textured, and relatively high.

To fly visually in this environment with low visibility is difficult, as the situation requires that the pilot maintain reference to the ground to maintain control, avoid terrain, and avoid low cloud and other areas of reduced visibility. The pilot had GPS receivers and moving map displays to assist with navigation, and flight instruments and autopilot with IFR capability, but that equipment was of limited use if the pilot was attempting to maintain visual reference. Based on the data available to the ATSB, it was not possible to determine whether the accident was a result of controlled flight into terrain or loss of control due to spatial disorientation.

Assessment of local conditions

It was not possible to establish if the manoeuvring before the collision with terrain indicated the pilot was attempting to return to the previous landing area or attempting to find a way through to the destination. Whatever the pilot’s intentions, at the time of the accident the pilot probably found himself in a situation where he was unable to negotiate the weather conditions with visual reference to the ground. In that context, the ATSB considered the pilot’s decision to lift off from the interim landing site and to continue the flight.

The ATSB was unable to identify all of the aspects relevant to the pilot’s decision to depart from the interim landing site but it is likely that the pilot was influenced by the following situational factors:

• an apparent improvement in the local weather
• the expected flight time to the destination meant that the expected time of arrival was getting increasingly closer to last light
• the distance from the interim landing site to lower terrain was relatively short
• the pilot may have been unaware of the actual weather along the prospective route or had reasonable expectations of navigating the weather conditions.

In considering a departure from the interim landing site, the pilot was able to assess the weather visible from the location and had the capability to access forecast and actual weather information via mobile devices. Although the pilot’s phone was not used, there were other devices available, and internet use for those devices could not be established.

The pilot’s decision to depart the interim landing site can be interpreted as likely taking advantage of a break in the severity of the local weather to proceed as far as the weather would allow. If the pilot had reached the lower terrain near the coast, there was a greater likelihood of being able to continue the flight to the destination or land at an airport with access to accommodation.

Once airborne, the pilot would have been in a position to assess the in-flight visibility and cloud and rain in the intended direction of travel. In another occurrence investigation,^[17] the ATSB has found that the ‘continuation of flight towards an area of low cloud and rain was likely influenced by the inherent challenges of assessing low visibility conditions, particularly without instrument flying proficiency.’ This finding was based on the following references.

The United States National Transportation Safety Board (2005) found that ‘reduced-visibility weather represents a particularly high risk to [general aviation] operations’ and that ‘weather may…test the limits of pilot knowledge, training, and skill to the point that underlying issues are identified.’

Wiegmann and Goh (2000) explained that:

One reason why pilots may decide to continue a VFR flight into adverse weather is that they make errors when assessing the situation. That is, pilots are seen to engage in VFR flight into IMC [instrument meteorological conditions] because they do not accurately assess the hazard (i.e., the deteriorating weather conditions).

The previously mentioned United States National Transportation Safety Board report (2005) added that in these cases, pilots who might appear to intentionally engage in risky behaviour may actually be making choices that they mistakenly believe to be safe:

Even if pilots are able to correctly assess current weather conditions, they may still underestimate the risk associated with continued flight under those conditions, or they may overestimate their ability to handle that risk.

Wiggins and O’Hare (1995) further explained how errors in assessment can take place, acknowledging that weather-related decision making can be highly complex and therefore more prone to errors:

Because of the variable nature of operations in the aviation environment, weather-related decision making is often considered a skill that cannot be prescribed during training. Rather it is expected to develop gradually through practical experience. However, in developing this type of experience, relatively inexperienced pilots may be exposed to hazardous situations with which they are ill‑equipped to cope.

ATSB Aviation Research and Analysis Report B20070063, An overview of spatial disorientation as a factor in aviation accidents and incidents, stated that pilots should not attempt to fly into instrument meteorological conditions under the VFR. Pilots should develop a plan prior to take-off on what to do if the weather en route is different from that expected, or deteriorates. This plan should consider a requirement to divert or turn back prior to entering instrument meteorological conditions. However, this depends on a pilot correctly assessing the weather conditions. The United States National Transportation Safety Board (2005) noted that targeted weather-related training programs have had some success in teaching pilots to recognise and respond to deteriorating weather conditions.

Additionally, Wiggins and O’Hare (2003) evaluated the effectiveness of a cue-based training system called Weatherwise, which was designed to equip VFR pilots with the skills to recognise and respond to the cues associated with deteriorating weather conditions during flight. VFR pilots were more likely to use the cues following the training, with subsequent improvements in their weather-related decision-making. The Weatherwise program was made available to pilots by the Civil Aviation Safety Authority (CASA). Additionally, CASA produced a Weather to Fly education program which focuses on topics such as the importance of pre-flight preparation, making decisions early, and talking to ATC.

The ATSB was unable to determine the pilot’s understanding of the weather conditions ahead of him prior to entering an area of low visibility conditions. However, the pilot had demonstrated an awareness of the risk posed by the weather and the need to maintain visual reference by diverting from the original track from Breeza then turning back from the first attempt to cross the high terrain.

Until the conditions improved, the only safe option available to the VFR pilot was to leave the helicopter at the interim landing site or transit to another landing area in the valley as the conditions permitted.

Safety considerations

VFR pilot decision-making

One of the ATSB’s SafetyWatch priorities concerns in-flight decision making in relation to VFR flight in environments with reduced visual references. As Avoidable Accidents No. 4 - Accidents involving Visual Flight Rules pilots in Instrument Meteorological Conditions relates:

Weather-related general aviation accidents remain one of the most significant causes for concern in aviation safety; the often-fatal outcomes of these accidents are usually all the more tragic because they are avoidable.

In the 5 years 2006–2010, there were 72 occurrences of visual flight rules (VFR) pilots flying in instrument meteorological conditions (IMC) reported to the ATSB. Seven of these resulted in fatal accidents, causing 14 fatalities. That is, about one in ten VFR into IMC events result in a fatal outcome.

Flying into IMC can occur in any phase of flight. However, a 2005 ATSB research publication General Aviation Pilot Behaviours in the Face of Adverse Weather concluded that the chances of a VFR into IMC encounter increased as the flight progressed, with the maximum chance occurring during the final 20 per cent of the flight distance.

The dangers of flying VFR into IMC have been recognised for a long time, yet VFR pilots still fly into deteriorating weather and IMC. This publication describes recent weather-related general aviation accidents and incidents that show that weather alone is never the only factor affecting pilot decisions that result in inadvertent IMC encounters. It has been produced solely with the intention of encouraging all pilots, no matter what their experience level, to develop the knowledge and skills required to avoid unintentional operations in IMC.

One of the key messages is for pilots to avoid deteriorating weather by conducting thorough pre-flight planning and to have alternate plans in case of an unexpected deterioration in the weather and making timely decisions to turn back or divert.

This principle applies to all aircraft operations, even though helicopters are inherently more flexible in terms of availability of landing areas and manoeuvrability. All pilots need to have a relevant and effective contingency plan that is based on the best available information in weather forecasts and reports.

Location of aircraft in an emergency

The pilot was operating with two Personal Locator Beacons (PLBs) and no fixed Emergency Locator Transmitter (ELT). Unlike a fixed ELT, the PLBs were not fitted with a ‘g’ switch and would require manual activation to transmit information. In this case, the occupants were fatally injured in the accident and no position information was transmitted from the beacons.

ATSB report AR-2012-128: A review of the effectiveness of emergency locator transmitters in aviation accidents references an Australian Maritime Safety Authority (AMSA) recommendation that occupants of an aircraft proactively activate an ELT (or PLB in this case also) when flying in dangerous weather conditions. This would greatly increase the likelihood of establishing the exact position of the aircraft if required. AMSA would need to be notified once the dangerous phase of the flight was complete and the ELT/PLB has been switched off. Activating a beacon under such circumstances requires an active decision on the part of the pilot. Additionally, in the event of inadvertent entry into IMC, pilots are encouraged to contact air traffic control for assistance, however on this occasion, no radio calls from the pilot to air traffic control were on record.

The severity of an accident potentially restricts fixed or portable ELTs to be reliably activated due to impact forces that can render the units inoperable, with research noting that they save about four lives a year. Furthermore, search and rescue operations also place others at risk and a degree of uncertainty exists until a missing aircraft is located. The removal of the fixed ELT with the potential for self-activation, for manually operable PLBs was in accordance with the regulatory requirements. On this occasion, the absent transmission coupled with the uncertainty of when the group would return to Terrey Hills, delayed the search and rescue response.

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17. AO-2016-006 Loss of control and collision with water involving Piper Aircraft Corp PA-28-235, VH-PXD. A copy of this report is available from www.atsb.gov.au

Findings

From the evidence available, the following findings are made with respect to the collision with terrain involving Airbus Helicopters EC 135 T1, VH-GKK, that occurred near Cooranbong, NSW on 7 November 2015. These findings should not be read as apportioning blame or liability to any particular organisation or individual.

Contributing factor

• The pilot departed an interim landing site for Terrey Hills under the visual flight rules with a high risk of encountering forecast cloud and reduced visibility. Due to the likely presence of cloud, the pilot probably experienced a loss of visual reference leading to a collision with terrain.

Other findings

• The personal locator beacons carried in lieu of a fixed emergency locator transmitter were required to be activated in the case of an accident. While in this accident it did not affect the outcome for the occupants, the lack of activation, combined with the absence of flight notification information, delayed the search and rescue response.

Sources and submissions

Sources of information

The sources of information during the investigation included:

• the Civil Aviation Safety Authority
• the Bureau of Meteorology
• Airservices Australia
• the French Bureau d'Enquêtes et d'Analyses
• the German Federal Bureau of Aircraft Accident Investigation
• SAFRAN – Turbomeca
• a number of witnesses.

References

Australian Transport Safety Bureau, 2011, Avoidable Accidents No. 4 Accidents involving Visual Flight Rules pilots in Instrument Meteorological Conditions, Aviation Research and Analysis publication AR-2011-050.

Australian Transport Safety Bureau, 2012, A review of the effectiveness of emergency locator transmitters in aviation accidents, Aviation Research and Analysis publication AR-2012-128.

Australian Transport Safety Bureau, 2017, Loss of control and collision with water involving Piper Aircraft Corporation, PA-28-235, VH-PXD, AO-2016-006.

Benson, AJ, 1999a, “Spatial disorientation – general aspects”, in J Ernsting, AN Nicholson & DJ Rainford (Eds.), Aviation Medicine (3rd ed.), Oxford, England, Butterworth Heinemann, pp. 419-436.

Gibb, R, Gray, R and Scharff, L, 2010, Aviation Visual Perception: Research, Misperceptions and Mishaps, Ashgate Publishing Limited, Surrey, United Kingdom.

Newman, DG, 2007, An overview of spatial disorientation as a factor in aviation accidents and incidents, Australian Transport Safety Bureau, Aviation Research and Analysis Report B2007/0063.

National Transportation Safety Board 2005, Risk Factors Associated with Weather-Related General Aviation Accidents, National Transportation Safety Board Safety Study NTSB/SS-05/01, Washington DC, United States.

Wiegmann, D and Goh, J, 2000, Visual Flight Rules (VFR) Flight into Adverse Weather: An Empirical Investigation of Factors Affecting Pilot Decision Making, Federal Aviation Administration research DTFA 00-G-010, Illinois, United States.

Wiggins, M and O’Hare, D, 1995, “Expertise in Aeronautical Weather-Related Decision Making: A Cross-Sectional Analysis of General Aviation Pilots”, Journal of Experimental Psychology: Applied Vol. 1 No. 4, pp. 305-320.

Wiggins, M and O’Hare, D, 2003, “Weatherwise: Evaluation of a cue-based training approach for the recognition of deteriorating weather conditions during flight”, The Journal of Human Factors and Ergonomics Society, pp.337-345.

Submissions

Under Part 4, Division 2 (Investigation Reports), Section 26 of the Transport Safety Investigation Act 2003 (the Act), the Australian Transport Safety Bureau (ATSB) may provide a draft report, on a confidential basis, to any person whom the ATSB considers appropriate. Section 26 (1) (a) of the Act allows a person receiving a draft report to make submissions to the ATSB about the draft report.

A draft of this report was provided to the Civil Aviation Safety Authority and the German Federal Bureau of Aircraft Accident Investigation.

Submissions were received from both organisations. A review of those submissions did not result in any amendment to the text of the report.

Purpose of safety investigations & publishing information

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through:  identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2018 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.