On 1 February 2015, at about 0800 Western Standard Time (WST), a Cessna 210 aircraft, registered VH-SMP (SMP), departed from Kununurra Airport, Western Australia, for a scenic flight over King George falls with the pilot and five passengers on board.
The pilot returned to Kununurra after about 2 hours. During the approach, the pilot selected the landing gear selector to the down position. However, the green landing gear down indicator light did not illuminate. In addition, the landing gear pump continued to operate until the landing gear pump circuit breaker popped. The pilot observed that the right and left main landing gear appeared to be in the down and locked position. However, the pilot was unable to observe the nose landing gear.
As he was unable to verify the position of the nose landing gear, the pilot conducted a missed approach and held at about 1,500 ft above the ground level to investigate the reason for the malfunction. The pilot also broadcast on the common traffic advisory frequency (CTAF) his intentions and briefed the passengers.
The pilot selected the landing gear down and up another two times. However, in the down selection, there was no green landing gear down light and the landing gear pump continued to operate until the circuit breaker popped. The pilot inspected the landing gear down light globe and determined it was operational.
The pilot then used the ‘landing gear fails to extend’ and ‘manual gear extension’ checklists, and conducted a manual gear extension. The main landing gear was observed to be in the down position, but there was still no landing gear down green light.
The pilot contacted the operator first via a text message using a mobile phone, and then on the company radio frequency. After consulting with the operator, the pilot conducted a low-level pass over the runway to enable the operator to observe the landing gear position from the ground.
During the low-level pass, the operator observed the landing gear and reported to the pilot that the landing gear appeared to be in the down position. The operator told the pilot that it was likely to be an indication problem. The pilot returned SMP for a landing on runway 12 and briefed the passengers for the landing.
At about 1020, SMP landed, with the main landing gear wheels touching down first. The pilot held full back pressure on the elevator controls to hold the nose wheel off the runway for as long as possible. After about 100 m, the nose of the aircraft sank on to the runway. At this point, the nose wheel collapsed, the propeller struck the runway, and the aircraft came to a stop. Once the aircraft was stationary, the pilot completed the shutdown checks. The pilot and passengers then exited the aircraft through the two front doors.
The pilot and five passengers were uninjured. The aircraft sustained minor damage, including damage to the propeller, nose wheel, and engine cowling.
Pilot comment
The pilot reported that when the manual gear extension hand pump was used to pump the gear down, and was pumped until it could not be pumped further, it felt just like when the gear is in the down and locked position.
The pilot indicated that SMP last flew on 12 January 2015, about 3 weeks before the incident flight, and that there was no outstanding maintenance.
Owner investigation
The owner of the aircraft conducted an investigation into the incident. As part of their investigation, they determined that one of the nose landing gear down lock pins had failed. The pin had failed in the area of the machined groove for the pin retention roll pin (Figure 1). The failed down lock pin migrated out and interfered with the nose landing gear actuator. This movement prevented the nose landing gear down lock mechanism from engaging in the down and locked position (Figure 2). The other down lock pin was serviceable.
Figure 1: Failed nose landing gear downlock pin
Source: Aircraft owner
Figure 2: SMP nose landing gear downlock assembly, showing the failed downlock pin preventing actuator movement to the locked position
Source: Aircraft owner, modified by the ATSB
Cessna Service Bulletin
Cessna Service Bulletin SEB95-20Nose Landing Gear Actuator Downlock Inspection dated 29 December 1995, recommended the inspection of the nose landing gear downlock actuator pins to determine the security of the pins.
Cessna had introduced the service bulletin as they had received reports that the nose landing gear actuator downlock pins had cracked and failed. It was found that the pins had failed at a circumferential groove that was used to secure the pin in the actuator bearing end. The service bulletin indicated that non-compliance could result in failure of the nose landing gear to lock in the down position and possibly collapse.
The recommended inspection was to be carried out initially within the next 200 hours operation or 12 months, whichever occurred first. Subsequent inspections at each landing gear retraction check were not to exceed 200 hours of operation thereafter. After the installation of the downlock actuator pin replacement, the repetitive inspection was not required.
Aircraft maintenance
SMP was manufactured in 1976 and, at the time of the incident, the aircraft had 9,965 hours total time in service. The aircraft was maintained under the Civil Aviation Safety Authority (CASA) maintenance schedule (Civil Aviation Regulations 1988 (CAR) Schedule 5). As the nose landing gear was inspected in accordance with Schedule 5, the operator reported that they did not need to comply with Cessna SEB95-20.
The periodic (100 hourly or 12-month) maintenance inspections were carried out in August 2014 at 9,871 hours total time in service (94 hours prior to the accident). This maintenance was conducted in accordance with the CASA maintenance schedule (Schedule 5). Schedule 5 did not include a specific inspection requirement to determine the security of the down lock pins.
NTSB investigation into similar failures
The US National Transport Safety Board (NTSB) investigated an accident involving a Cessna R182 aircraft, registered N6149S at Allegheny County Airport, West Mifflin, Pennsylvania on 18 May 2005 where the nose landing gear collapse during the landing.[1]
The NTSB determined that one of the downlock actuator pins (the same part number as SMP) on the nose landing gear actuator had failed and migrated out. The pin contacted the actuator arm piston, and prevented the full travel of the nose landing gear to the down and locked position. The NTSB examined the downlock pin and found that it had failed due to a fatigue crack. The investigation also found that the Cessna Service Bulletin SEB95-20Nose Landing Gear Actuator Downlock Pin Inspection had not been carried out. The investigation found over 30 other nose landing gear collapses that were attributed to the actuator down lock pins on similarly equipped Cessna aircraft.
The NTSB also investigated another similar accident involving a Cessna R182 aircraft, registered N5274S, at Ames Municipal Airport, Ames, Iowa, on 22 October 2006 where the nose landing gear collapse during the landing.[2]
The NTSB determined that one of the downlock actuator pins (the same part number as SMP) on the nose landing gear actuator assembly bearing end had failed and migrated out. The pin contacted the actuator arm piston, and prevented the full travel of the nose landing gear to the down and locked position. Both downlock pins were found to have fatigue cracks. Again, there was no evidence that Cessna Service Bulletin SEB95-20 had been complied with.
ATSB comment
On 12 September 2011, a flight control system event occurred involving Cessna 210N, VH-JHF, 48 km West of Bourke Airport, NSW. The ATSB investigation (AO-2011-115) found that reported elevator control input difficulties resulted from the fracture of the aircraft’s two horizontal stabiliser rear attachment brackets. The nature of the failures was typical of the damage sustained by aircraft as they age and move beyond the manufacturer's originally intended design life.
The investigation identified that maintaining class B aircraft in accordance with the Civil Aviation Safety Authority (CASA) maintenance schedule, without due regard to the manufacturer’s or other approved data, does not adequately provide for the continuing airworthiness of those aircraft.
As a result of the investigation the ATSB issued CASA a Safety Recommendation AO-2011-115-SR-050:
The Australian Transport Safety Bureau recommends that CASA proceed with its program of regulatory reform to ensure that all aircraft involved in general aviation operations are maintained using the most appropriate maintenance schedule for the aircraft type.
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.
Aircraft owner
As a result of this occurrence, the aircraft operator has advised the ATSB that the aircraft owner has taken the following safety actions:
Aircraft maintenance
Subsequent to the incident, the aircraft owner replaced the landing gear down lock pins with updated pins on two other aircraft that the owner is responsible for, and found no abnormalities with the removed pins or the nose landing gear actuator bearing ends.
Safety message
This accident highlights the importance of comprehensive, periodic maintenance inspections and the role manufactures continuing airworthiness instructions in maintaining ageing aircraft. As aircraft age, the original maintenance schedules may not be sufficient to ensure the aircraft’s ongoing safety. As a result of investigation report AO-2011-115 the ATSB encourages registration holders of class B aircraft to review their aircraft’s maintenance schedule to determine if it is the most appropriate for their aircraft and to ensure that it adequately provides for the continuing airworthiness of the aircraft.
In 2007, the ATSB released research report B20050205 - How Old is Too Old? The impact of ageing aircraft on aviation safety and is available from the ATSB website. The report found that some aircraft manufacturers have recognised that the original maintenance schedules may not be sufficient to ensure the aircraft’s (ongoing) safety. Those manufacturers have developed additional continuing airworthiness information. The report concluded that adequate maintenance of ageing aircraft requires the participation and ongoing cooperation of aircraft manufacturers, regulatory authorities, owners, operators, and maintainers.
In 2012, in recognition of the Australian general aviation aging aircraft fleet, CASA released a discussion paper Ageing Aircraft Management Plan (AAMP). The discussion paper makes the following relevant points:
As an aircraft ages up to and beyond its original design assumptions, the nominated maintenance program needs to be modified to take into account ageing issues. In particular, inspections of key areas or components not usually accessed.
CASA and Authorised Persons are obliged to take into account all relevant maintenance data or information pertinent to a particular aircraft type. This includes manufacturer’s data, Airworthiness Directives, Service Bulletins and other continuing airworthiness information.
CASA Maintenance Schedule 5 was originally conceived as a minimum schedule of maintenance activities, to be undertaken on a very limited range of relatively simple, ‘orphan’ aircraft
CASA Maintenance Schedule 5 was not originally intended to address ageing aircraft related issues. The literal application of this schedule on its own was not intended to replace the manufacturer’s instructions for continued airworthiness, where available.
The adequate maintenance of ageing aircraft requires the participation and ongoing cooperation of aircraft manufacturers, regulatory authorities, owners, operators, and maintainers.
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
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.
On 29 January 2015, the student pilot of a Cessna 172S aircraft, registered VH-EOP, taxied for a solo training flight at Moorabbin Airport, Victoria. The student was cleared by air traffic control (ATC) to taxi via taxiway ‘A’ (Figure 1) to the holding point on taxiway ‘G’ for a departure from runway 13 Left (13L).
Figure 1: Extract of Moorabbin Airport En Route Supplement Australia entry
Source: Airservices Australia
As EOP passed the ‘A2’ taxiway, the right wingtip struck the rudder of another Cessna 172S aircraft, registered VH-EOT, which was stationary at the holding point for runway 13 Right (13R) on the ‘A2’ taxiway, and less than half a metre behind the marked holding line (Figure 2). The student pilot of EOP was unaware of the collision and continued to taxi to the holding point for runway 13L. A flight instructor on board EOT advised ATC of the collision and the controller directed the pilot of EOP to taxi back to the run-up bay. He was then advised of the collision and the instructor of EOT inspected both aircraft for damage. EOP was undamaged and EOT sustained minor damage to the rudder.
Pilot comments
The student pilot of EOP reported that he taxied on the yellow marked taxi line and assumed that this would provide adequate clearance from the stationary aircraft.
He subsequently had a taxi lesson focused on maintaining adequate clearance from other aircraft and obstacles, which he believed would be valuable training for all student pilots.
Figure 2: Moorabbin Airport, EOP taxi route and location of EOT
Source: Google earth
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.
Moorabbin Airport operator
As a result of this occurrence, the airport operator is taking the following safety actions:
Taxi line repaint
A work order has been raised to extend the left turn taxiway line to join the northern apron right side taxi line (Figure 3). This will increase the distance between an aircraft taxiing via taxiways ‘A’ and ‘G’ and an aircraft holding at the ‘A2’ holding point.
Figure 3: Taxiway line to be extended
Source: Google earth
Safety message
This incident highlights the importance of maintaining a good lookout when taxiing. Practice in taxiing an aircraft assists pilots to develop an awareness of where the extremities of the aircraft structure are going to track during ground manoeuvring.
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
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.
On 23 January 2015, the pilot of a Robinson R22 helicopter, registered VH-ZBH, prepared for a private flight to inspect a property at Herbertvale, Queensland, with one passenger on board. Nothing abnormal was found during the pre-flight inspection of the helicopter. About 35 L of fuel was on board the helicopter, and the pilot conducted a fuel drain with nil contaminants found. At about 0600 Eastern Standard Time (EST), the pilot started the engine. All indications were normal throughout the run-up checks.
The pilot then increased the power to 104% for take-off and the helicopter lifted off into a low hover. The pilot reported that the helicopter responded normally and he turned the helicopter 90° to the north to depart. The helicopter transitioned from the hover to forward flight, moving about 10 m forwards and climbed to about 20 ft above ground level. The engine then lost power and the pilot detected vibration. He observed the rotor rpm decreasing and the low rotor rpm warning sounded.
The pilot immediately wound on throttle and lowered the collective[1] in an attempt to increase the rotor rpm and to ensure the helicopter cleared a fence. He then prepared for an emergency landing. The rear of the skids touched down first and the helicopter skidded forwards. As the helicopter still had forward momentum, the pilot then pulled back on the cyclic[2] to prevent the helicopter rolling over forwards, and it became airborne, moved forwards and yawed right, and bounced again before coming to rest upright (Figure 1).
The helicopter was substantially damaged due to the impact on the skids, and the pilot and passenger were uninjured.
Engineering inspection
A post-accident engineering inspection did not reveal any cause of the engine loss of power.
Figure 1: Damage to VH-ZBH
Source: Owner
Safety message
The pilot in this incident had recently completed a check flight including practice autorotations. The avoidance of injury and handling of the autorotation highlights the benefits of practice. The following links provide information regarding practice autorotations:
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
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.
On 16 January 2015, at about 0930 Eastern Standard Time (EST), the pilot of a Robinson R22 helicopter, registered VHSSD, was conducting aerial mustering operations on a property 23 km north-east of Roma, Queensland.
The helicopter was about 100 ft above ground level (AGL), with a low forward airspeed of about 5-10 kt and the cattle moving slowly uphill, when the pilot observed the cattle start to move back down the side of the hill towards a creek. The wind was light and blowing across the path of the helicopter from the left. The pilot elected to descend along the side of the cattle and turned the helicopter towards the right.
As he did that, the helicopter turned downwind with a high-power setting and low forward speed. The pilot realised he had turned downwind and started to raise the nose of the helicopter and raise collective.[1] He then detected a high rate of descent and an incipient vortex ring state, as the helicopter started to settle into its own downwash. He attempted to fly out of the situation, lowered the collective and wound the throttle on, but had insufficient forward speed and low rotor rpm. The low rotor rpm horn sounded at about 15-20 ft AGL. The pilot tried to regain rotor rpm but the helicopter sank quickly.
The pilot then ensured the skids were level and the helicopter collided with the ground. Due to the rough surface, the helicopter bounced into the air. The pilot pulled back on the cyclic[2] control, which resulted in the tail of the helicopter being chopped off by the main rotor. The helicopter then spun around and came to rest on its side (Figure 1). The helicopter was substantially damaged, and the pilot was uninjured.
Figure 1: Damage to VH-SSD
Source: Operator
Vortex ring state
The United States Federal Aviation Administration (FAA) handbook www.faa.gov/regulations_policies/handbooks_manuals/ describes the vortex ring state or settling with power, as an aerodynamic condition in which a helicopter may be in a vertical descent with 20% to maximum power applied and little or no climb performance.
The following combination of conditions is likely to cause settling in a vortex ring state in any helicopter:
1. A vertical or nearly vertical descent of at least 300 feet per minute (fpm). The actual critical rate depends on the gross weight, rpm, density altitude, and other pertinent factors.
2. The rotor system must be using some of the available engine power, between 20-100%.
3. The horizontal velocity must be slower than effective translational lift.
A fully developed vortex ring state is characterized by an unstable condition in which the helicopter has uncommanded pitch and roll oscillations, little or no collective authority, and a descent rate that may approach 6,000 fpm, if allowed to develop (Figure 2).
Figure 2: Vortex ring state
Source: FAA
Safety message
The pilot involved in this incident was highly experienced, with over 10,000 hours total flying (helicopter) time and over 6,000 hours in Robinson R22 aircraft. He stated that the fundamental message was to always have forward airspeed before turning downwind.
This incident highlights the importance of continually assessing and reassessing the prevailing conditions and their effect on aircraft performance. The Airbus Helicopters (formerly Eurocopter) publication, Decision Making for Single-Pilot Helicopter Operations, explains some of the factors that affect pilots’ decision making.
In the ATSB investigation AO-2013-099, the pilot of the helicopter lost situational awareness during a night approach and the helicopter developed a high rate of descent with a low forward airspeed. This resulted in the onset of an incipient vortex ring state in the final stages of flight.
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
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.
During the morning of 9 January 2015, the pilot of VH-YMD was operating in support of the Northern Territory Police. As part of the operation, the pilot conveyed two passengers to a site on the Todd River, just north of Alice Springs. The pilot landed on the sandy surface of the river bed where the passengers disembarked, then flew the helicopter from that location to a local landmark known as the Telegraph Station, about 3 km away. The pilot then conveyed another two passengers from the Telegraph Station to the site, and again landed on the sandy surface of the river bed, facing in a westerly direction (Figure 1).
Figure 1: VH-YMD landing site on the river bed
Source: Northern Territory Police
Soon after, the pilot was asked to convey three passengers back to the Telegraph Station, as a continuing part of the police operation. When all three passengers had boarded the helicopter, the pilot lifted off from the river bed. Lift-off was normal, and the pilot commenced departure in a southerly direction over the river (Figure 2) to follow what he assessed to be the most clear and suitable departure route from the river bed. As the helicopter climbed away from the river bed, the pilot became aware that the main rotor RPM was decaying. In response, he overrode the governor and applied full throttle.
The pilot needed to maintain height to clear the rocks and shrubs on the southern side of the river, but was acutely aware that rotor RPM would be further compromised by the application of more collective.[1] The pilot carefully managed the collective and the helicopter cleared the rocks and shrubs, but with decaying rotor RPM, he realised that continued climb was not possible. The pilot steered the helicopter toward a flat area, just above the river bed on the southern side of the river, and conducted a run-on landing[2] (Figure 3).
Figure 2: Photograph taken from left side of VH-YMD as it crossed the river
Source: Northern Territory Police
Figure 3: Take-off and landing area
Source: Northern Territory Police (two photographs joined and edited by the ATSB)
During the run-on landing, the left skid sank into mud and struck a rock. The left skid was substantially damaged by the impact (Figure 4) and the helicopter tipped precariously. As the helicopter came to a stop, it was on a substantial lean. The pilot reported that he considered the situation to be unsafe, so he immediately lifted off again and repositioned the helicopter on the ground with a level attitude. During the second lift off, a passenger recalled that the main rotor of the helicopter struck the limb of a tree, and that this was when damage to the tail boom occurred[3] (Figure 4). The pilot then shut down the engine and the passengers evacuated the helicopter.
Figure 4: Damage to VH-YMD skid (left) and tail boom (right)
Source: Northern Territory Police (edited by the ATSB)
Weather conditions
At the time of the accident, weather conditions were overcast, with showers in the area and a temperature of about 25 ºC. The wind at Alice Springs Airport (about 18 km to the south) was from the north-west at about 15 kt, and the QNH[4] was about 1003 hectopascals. While the pilot was aware that the wind was generally a north-westerly, he assessed the wind at the site as relatively light and variable. The relative humidity at Alice Springs Airport was around 80 per cent, and the pilot reported humid conditions at the accident site.
Pilot comment
The pilot commented that he believed that the accident resulted from a combination of a relatively heavy take-off weight, the prevailing conditions, and limited departure options because of surrounding terrain and obstacles. The pilot indicated that, with the benefit of hindsight, he should have taken two trips to move the three passengers, rather than attempt to take off with three passengers on board. He believed that he would have been able to complete the departure safely at a lower take-off weight.
Power required and power available
A number of factors related to the power required and the power available warrant consideration in understanding the probable reasons for which the pilot experienced decaying main rotor RPM during departure from the river bed, as the helicopter moved out of ground effect[5] and transitioned into forward flight. These factors include density altitude, take-off weight and the wind component.
Density altitude. Increasing density altitude adversely affects helicopter performance through the combined effects of reducing the power available and increasing the power required. Considering elevation and temperature, and barometric pressure in the area, the density altitude at the accident site would have been around 4,000 ft. High relative humidity would have had the effect of further increasing the density altitude.
Take-off weight. Increasing the take-off weight increases the power required. The greater lifting force demanded of the main rotor, and the requirement to counter the associated increased torque effect[6] with the tail rotor, both contribute to an increased power requirement. The pilot estimated the weight of the helicopter at the time of the accident to be less than the maximum permitted take-off weight, however subsequent calculations by the operator using actual data, indicated that the take-off weight was marginally above the maximum permitted take-off weight.
Wind component. Taking off with a tailwind component increases the power required because of the diminished or delayed influence of translational lift.[7] Additionally, a tailwind or crosswind component may require greater tail rotor force to maintain directional control during departure, which places an increased power demand on the engine. Although the pilot commented that the wind seemed light and variable prior to departure, the helicopter may have encountered a tailwind component as it climbed away from the river bed during the accident flight.
The following references discuss factors affecting helicopter performance, and provide some guidance to pilots regarding the associated considerations:
A ‘Good Aviation Practice’ booklet titled Helicopter Performance, produced by the Civil Aviation Authority (CAA) of New Zealand. The booklet is available via the
The Federal Aviation Administration (FAA) Helicopter Flying Handbook(chapter 7 deals with helicopter performance). The handbook is available on the FAA website.
Safety message
The Robinson R44 Pilot’s Operating Handbook includes a number of important safety tips and notices. Pilots (particularly those who fly Robinson helicopters) are encouraged to carefully reflect on these safety tips and notices – the tips are suggestions intended to improve safety, while the notices have been issued as a result of various accidents and incidents. The safety tips and notices are available in the R44 Pilot’s Operating Handbook on the Robinson Helicopter Company website under the Publications tab. Two Safety Notices with relevance to this accident are Safety Notice 10 (Fatal accidents caused by low RPM rotor stall) and Safety Notice 24 (Low RPM rotor stall can be fatal). One safety tip with particular relevance to this accident is:
Never allow rotor RPM to become dangerously low. Most hard landings will be survivable as long as the rotor is not allowed to stall.
Three other ATSB investigation reports that identified helicopter performance and low main rotor RPM as possible factors include AO-2013-203, 200600979 and 199900833. These investigation reports are available on the ATSB website.
This accident provides a reminder of the effect on helicopter performance of density altitude, weight, and possibly wind. Pilots are encouraged to carefully and accurately assess these factors before committing to any departure. Careful assessment of these factors is essential to ensure that an adequate performance margin is maintained, particularly under high density altitude conditions, when the helicopter is near its maximum take-off weight, or where the direction of departure is downwind. When performance is likely to be adversely affected by a combination of these factors, extreme caution is warranted.
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
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.
On 9 January 2015, a pilot in-command-under-supervision (ICUS), and a supervising pilot, operated a Piper PA-31-350 aircraft, registered VH-TXK, on a charter flight from Palm Island to Townsville, Queensland, with seven passengers on board. At about 1630 Eastern Standard Time (EST), air traffic control (ATC) cleared the aircraft to conduct a visual approach via a left base, to runway 07 at Townsville Airport.
When about 4 NM from the runway, the pilot ICUS performed the pre-landing checks, but omitted to extend the landing gear. The supervising pilot confirmed the mixture, fuel pumps and landing lights had been set correctly, and assumed the rest of the checks had been similarly completed. As the aircraft turned from base to final for runway 07, the supervising pilot alerted the pilot ICUS that the aircraft was too high, which the pilot ICUS immediately corrected by selecting full flap and a lower nose attitude. As the aircraft was then slightly higher and faster than for a normal approach, the pilot ICUS reduced the throttle to idle slighter earlier than normal. As he flared the aircraft to land, he anticipated the landing gear touching down on the runway, but as it did not occur when he expected, he commenced a go-around. At the same time, the supervising pilot expected the landing gear to touch down and called ‘go around’. Neither of the pilots heard an aural gear warning horn sound.
As the pilot ICUS commenced the go-around, a VHF antenna fitted to the underside of the aircraft fuselage contacted the runway and both pilots heard a scraping sound. The pilots broadcast ‘going around’ and did not receive a response. After a second call to ATC also did not elicit a response, the supervising pilot selected the second VHF radio (COMM2) and was then able to communicate with ATC. When at about 50 ft above ground level (AGL), the pilot ICUS observed the landing gear lever in the UP position, and was then unsure whether he had omitted to select the landing gear DOWN during the pre-landing checks, or whether a technical fault had occurred.
The supervising pilot assumed that there was a technical fault with the landing gear and prepared to perform a manual gear extension. The pilot ICUS established the aircraft in a slow cruise configuration at about 1,400 ft (AGL), extended flap and, when the aircraft was below the maximum gear extension speed, selected the landing gear lever to the extended position. The landing gear extended and locked and three green lights indicated a safe extension. The pilot ICUS confirmed visually that the nose landing gear was extended. The pilots discussed the option of conducting a fly-by to verify the landing gear had extended fully, but elected to return for a landing. The aircraft subsequently landed on runway 07 without further incident.
The VHF antenna was found on the runway, having broken off from the underside of the aircraft after striking the runway (Figures 1 and 2). Two aerodynamic fins also sustained minor scrapes from the runway. The pilots and passengers were uninjured in the occurrence and a subsequent engineering inspection found that the landing gear warning horn was serviceable.
Figure 1: Broken antenna
Source: Aircraft operator
Figure 2: Photo of new antenna fitted to VH-TXK
Source: Aircraft operator
Pilot comments
The pilots provided the following comments:
The pre-landing and finals checks were conducted from memory, rather than a written checklist. With a pilot ICUS and supervising pilot, the pilot may have vocalised the checks as they were being performed, but on this flight the pilot ICUS could not recall vocalising the checks and the supervising pilot did not recall hearing them. The company did not have standard procedures for ICUS flights.
Neither pilot completed checks when on final to confirm the landing gear indicated three green lights. The supervising pilot reported that when landing on runway 07 late in the afternoon, the position of the sun often made the cockpit display, including the landing gear indication, appear to be illuminated.
The stall warning would normally sound during the landing phase in that aircraft. Neither pilot recalled hearing the aural stall warning or landing gear warning horn. As the aircraft was on a slightly higher and faster approach than normal, the pilot ICUS reduced the throttle to idle earlier than for a normal landing. This should have activated the landing gear warning, unless the throttle levers were not retarded to a position fully against the idle stops.
The pilot ICUS had used written checklists when operating other aircraft, but had been trained to perform checks from memory for the PA-31.
Aircraft operator comments
The pilot ICUS held the appropriate endorsements for the aircraft and had 47.7 hours experience on the aircraft type. His total flying time was 319.5 hours. The aircraft insurer required a pilot to hold a minimum of 600 hours total time to operate the aircraft as pilot in command, hence the pilot was operating under supervision.
As they do not normally conduct two-pilot operations, they did not have a training program in place for such operations.
Department of Defence investigation
The Department of Defence conducted an internal investigation into the incident and reported that, during normal operations, the Tower controller was required to scan an aircraft during critical stages of flight. This included monitoring that the aircraft was on the appropriate track, level and positioned for the correct runway. They were also required to scan for any abnormalities with the aircraft. It was normal process for all Townsville air traffic controllers to visually scan the undercarriage status of all aircraft on final approach.
The Tower controller could not recall specifically observing the position of the aircraft’s landing gear when scanning the aircraft on final approach, but the position of the sun at the time of the incident may have affected the Tower controller’s ability to observe the aircraft’s landing gear.
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.
Aircraft operator
As a result of this occurrence, the aircraft operator has advised the ATSB that pilots will henceforth require a minimum of 600 hours total aeronautical experience prior to operating that aircraft type. Company pilots will receive additional experience and training prior to operating as supervising pilots.
Department of Defence
As a result of this occurrence, the Department of Defence has advised the ATSB that they are taking the following safety actions:
A safety awareness poster was created and displayed in prominent locations for Townsville based controllers to view, describing an ‘effective scan’.
Townsville controllers were briefed on the importance of proper scan technique during the critical stages of an aircraft’s flight. Particular mention was made of the importance of checking the status of the landing gear when an aircraft is cleared to land.
Safety message
This incident is a reminder for pilots and operators of the limitations of human performance and highlights the need to follow procedures and complete checklists diligently.
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
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On the morning of 9 January 2015, a Regional Express operated SAAB 340B aircraft, registered VH-OLM struck a flock of birds during its landing roll at Moruya, New South Wales. Inspection of the aircraft by the flight crew found bird impact marks but no visually identifiable damage. The crew continued their schedule to Merimbula, New South Wales. At Merimbula, the first officer noticed the tip of one propeller blade was missing, and the aircraft was subsequently grounded.
What the ATSB found
The blade tip failure was almost certainly a result of the birdstrike during the landing roll of the previous flight, weakening the internal structure of the blade.
The flight crew conducted a visual inspection in accordance with the operator’s procedures, and this inspection did not find any damage. However, the propeller manufacturer’s birdstrike inspection procedure was deemed a maintenance task. As such, it was not suitable for flight crew.
What's been done as a result
The operator changed its birdstrike procedures to ensure aircraft remained on the ground until a maintenance inspection was carried out in accordance with appropriate documented inspection procedures. In addition, pilot and engineering notices were issued clarifying these requirements.
Safety message
Adherence to regulations and company procedures is essential for the ongoing airworthiness of aircraft. Therefore, it is vital that procedures are clear and do not lead to ambiguity or misinterpretation. Where uncertainty exists, seeking clarification from the relevant authority can reduce the risk of an unserviceability affecting flight safety.
Safety analysis
Introduction
During the landing roll at Moruya Airport, a number of birds were struck. On the following flight, the left propeller blade tip failed. This analysis examines the actions of the flight crew, the failure mechanism of the blade, inspection requirements following a birdstrike, and factors that may have identified the potential risk of blade failure.
Flight crew actions
The presence of galahs to the right of the runway during the landing roll presented a high risk of impact to approaching aircraft. The captain followed appropriate actions to maximise aircraft deceleration while minimising potential impact damage through effective use of reverse thrust and aircraft wheel braking. Despite the crew’s best efforts, the subsequent impact with the birds was considered unavoidable.
The birdstrike inspection carried out by the flight crew was in accordance with the operator’s procedures. The crew reported performing a thorough visual inspection of the individual blades on both propellers, including rotation of the propellers to sight along each blade surface for damage or deformation. Despite the lack of visible damage associated with the bird impacts, the captain sought further advice from the operator’s engineering department before determining the aircraft was serviceable. The engineering department reportedly advised the captain to follow the flight crew’s documented procedures, and if no damage was evident, continue with the flight schedule.
Blade failure mechanism
Review of the blade’s service history showed it had undergone numerous non-destructive tests (NDT) and inspections, including an ultrasound inspection in 2011. None of those inspections revealed evidence of internal delamination. As there were no previously reported incidents of impact to the blade, it is unlikely that a pre-existing defect below the blade surface existed or influenced the blade’s failure.
Examination of the blade found that the failure mode was consistent with a bird impact. Consequently, given the failure occurred on the flight following the birdstrike, it is almost certain that impact with one or more galahs initiated the internal delamination of the blade. This led to a rapid decay of its structural integrity and subsequent separation of the tip, as the blade was subjected to aerodynamic loads during the following flight.
The propeller manufacturer indicated that the buckling of the blade guard would probably have occurred as a result of the impact rather than due to subsequent aerodynamic loading, and the damage to the guard would have been evident when the blade was inspected by the flight crew at Moruya.
The ATSB agrees it is plausible that the birdstrike resulted in cracking of the leading edge of the guard. However, the extent to which the damage to the guard would have been readily detectable when the blade was inspected at Moruya is unclear. Once the leading edge guard lost structural integrity, together with internal delamination damage, it is difficult to determine the nature of the subsequent loading conditions during flight.
Inspection requirements
The flight crew were not familiar with the propeller manufacturer’s inspection procedure, however, there were specific propeller inspection instructions in their normal procedures following a birdstrike, and the captain and first officer reported carrying out a thorough visual examination of the propeller blades in line with these procedures. Regardless of the nature of the flight crew’s inspection, both CASA and the propeller manufacturer considered the inspection to be a maintenance task, and required it to be carried out by qualified maintenance personnel.
The ATSB could not determine if an engineering inspection would have highlighted any possible damage. However, if an appropriately qualified person inspected the multiple bird impacts on the blades, they may have sought further advice from the propeller manufacturer in accordance with the documented propeller manufacturer’s maintenance procedure ‘if there is doubt concerning secondary impact damage…’ As the flight crew did not have this document, they would not have been aware of this procedure. Despite this, the captain did seek further advice from the operator’s engineering department. As an on-site engineering inspection was not carried out, the operator’s engineering department may not have had a full appreciation regarding the multiple birdstrikes.
The discussion between engineering and the flight crew focused on the presence of visible damage to the blade, and the documented flight crew inspection procedures. Consequently, the reported blade condition did not raise concerns with the engineering department about potential secondary damage or reduced structural integrity. That determination presented a missed opportunity to undertake an engineering inspection of the aircraft prior to take off. Consequently, the potential to detect sub-surface damage was also missed.
The Civil Aviation Safety Authority (CASA) provided the operator with advice on interpreting regulations for situations where pilots may or may not undertake birdstrike inspections. That advice included that if specific birdstrike inspection procedures within instructions for continuing airworthiness (ICA) deemed the inspection task as being a maintenance requirement then they were not suitable for flight crew. It is apparent the operator misinterpreted the advice from CASA as only referring to the aircraft manufacturer’s procedures and not also the propeller manufacturer’s procedures. As a result, the operator’s procedures allowed flight crew to undertake visual inspections after a birdstrike (beyond confirmation of whether there was a strike).
Moruya Airport bird and animal control
The frequency of bird and animal (wildlife) strike incidents over a 10-year period did not indicate that an increasing wildlife problem existed at Moruya Airport. The presence of galahs was common, however the galahs were typically in small numbers, and contained to around the buildings and treed areas.
According to the Moruya 2014 bird and animal report, and along with the birdstrike statistics for Moruya, the airport’s reliance on the maintenance of the grass adjacent to the runway as a pre-emptive means of bird management generally appeared to work for maintaining low wildlife strike incidents. On the day of the occurrence, the grass around the runway was long, and was scheduled for cutting later in the day. The ATSB bird information sheet indicates long grass can deter galahs. However, in this instance, the presence of grass seeds on the long grass may have contributed to their increased numbers and proximity to the runway. Consequently, when birds are located in the grass adjacent to the runway, an increased risk of aircraft strikes existed.
Context
Personnel information
Both the captain and first officer held valid Class 1 medical certificates, and were appropriately qualified to conduct the flight. The captain had a total aeronautical experience of approximately 7,000 hours with 4,300 hours flying Saab 340 aircraft. The first officer had a total aeronautical experience of around 5,400 hours with 4,200 hours flying Saab 340 aircraft.
A review of the crew’s recent history indicated that fatigue was not a factor, with both crew reporting they had an average to good sleep during the previous 72 hours.
Aircraft information
The aircraft, a Saab Aircraft CO 340B-2, was manufactured in 1990 and entered the Australian aviation register in October of that year. The aircraft is a twin engine turbo-prop and configured to carry 36 passengers and three crew. The aircraft was maintained under Civil Aviation Safety Regulation Part 42, which detailed the continued airworthiness requirements for regular public transport aircraft.
Aircraft damage information
The majority of the bird remains were found on the right side of the fuselage behind the forward right door, which was consistent with birds contacting the lower half of the right propeller disc. Small items of debris were also observed on both engine nacelles. There was no evidence of debris entering either engine. All of the blades on the right propeller showed evidence of impact with birds. Only one blade on the left propeller displayed evidence of bird contact.
Data from the aircraft’s flight data recorder for the flight from Moruya to Merimbula was examined. That data did not show any anomalies that would have identified the point when the propeller blade tip separated.
Propeller blade
Propeller blade construction
The propeller blades were manufactured by Dowty Propellers. They were made of composite construction with a polyurethane foam core, carbon fibre spars, glass fibre skin, and a polyurethane coating. A braided metal strip between the glass fibre and polyurethane coating ran from the tip of the blade to its root, providing lightning protection (Figure 3).
Figure 3: Propeller blade construction
Source: Dowty Propellers modified by ATSB
Left propeller blade damage
The left propeller blade presented with white powder impact marks toward the trailing edge, about 300–400 mm from the blade tip; about one third up the blade’s length. A section of blade was missing from the tip. Within the tip damage region, splitting at the trailing edge was identified (Figure 4). Damage to the leading edge erosion strip near the tip was also identified, with kinking on the back, and a corresponding crack on the front of the blade.
Figure 4: Left propeller blade damage showing tip separation, kinking, crack, and splitting of trailing edge
Source: ATSB
Blade history
A review of the damaged blade’s service history showed it was installed on the propeller as a new item in 2000. The propeller had also undergone a number of inspections since that time, including overhaul in 2011. The overhaul facility advised that during the 2011 propeller overhaul, ultrasonic NDT was carried out on the propeller’s blades. All of the blades were found to be serviceable. There were no reported incidents of impact to the blade prior to this occurrence.
Blade examination
The damaged blade was sent to the ATSB for in initial assessment. A visual inspection, and a ‘tap test’ using a metallic object were conducted on the blade. That test revealed a potential area of delamination or disbond under the surface extending from the tip separation point.
The blade was subsequently sent to a third-party laboratory for NDT and destructive testing under the supervision of the ATSB. A dual probe ultrasonic tester was used over the entire surface of the blade. Disbond was detected in a region extending from the spar through to the tip of the blade (Figure 5A). Further destructive testing in the form of surface grinding was carried out to determine at which layers the disbond had occurred. That action showed disbonding at the carbon fibre spar tips. The disbond had also propagated along the glass fibre layer of the blade beyond the spars (Figure 5B).
Figure 5: Region of disbonding shown
Source: ATSB
The propeller manufacturer determined the damage was consistent with the effects of impact on the blade from the birdstrike. The most likely failure mechanism was considered to be delamination between the blade’s foam core and spar barrier membrane. The delamination then progressed outboard into the fibreglass layer beyond the spar resulting in the subsequent tip failure.
The propeller manufacturer concluded that the kink in the erosion strip on the back of the blade (Figure 4) was consistent with an impact on the front of the blade near the tip, bending the blade tip rearwards rather than forwards. The manufacturer considered this damage was consistent with a bird or other hard object impact. It also stated that it considered that the buckling of the guard would probably have occurred as a result of the impact rather than due to subsequent aerodynamic loading. Therefore, it believed the kink would most likely have been present at the time the blade was inspected at Moruya.
Propeller and blade maintenance requirements
Birdstrike procedure
The operator’s policy and procedures manual included a section on birdstrikes, which stated:
Following a known or suspected Bird Strike the Flight Crew must complete the External Inspection (Crew Change) in its entirety in accordance with the Saab 340 Flight Crew Operating Manual [FCOM].
Generally, blood and/or feathers are noticeable in the impact area of a bird strike. In low light conditions a torch must be used.
Any defect, major damage or evidence of ingestion into an engine or airframe intake (include AC & DC Generator intakes) must be entered in an AML [aircraft maintenance log] and an engineering inspection must be performed prior to any subsequent flight.
If the inspection does not reveal the existence of a defect or damage, and there was no effect on the aircraft’s performance following the event, the aircraft may continue to operate.
Prior to the next flight, the Ice Protection must be checked in accordance with the Saab 340 Flight Crew Operating Manual.
Flight crew inspections
The operator’s Saab 340 flight crew operating manual (FCOM) included procedures for three types of external aircraft inspections by flight crew:
daily inspection, conducted prior to the first flight of the day
crew change inspection, conducted prior to the next flight when a flight crew accept an aircraft previously flown by another crew that day, if the aircraft has been taken off-line for maintenance during the day, or the aircraft is left unattended and not under continuous surveillance of the flight crew
post flight inspection, conducted at the conclusion of each flight.
The FCOM procedures for a daily inspection and a crew change inspection both included a detailed list of items required to be checked by a flight crew. The only propeller specific items were:
Inspect propeller assembly for oil or grease leakage from hub assembly
Inspect propeller de-icer boots…
The FCOM procedures for a post-flight inspection included a smaller list of items. In terms of propellers, the items included:
Propellers – including freedom of rotation and each blade front and back for obvious damage.
Maintenance procedures
The operator’s system of maintenance was conditional on the inclusion of the relevant manufacturer’s maintenance manuals. Consequently, birdstrike inspection procedures were derived from the aircraft manufacturer’s aircraft maintenance manual (AMM) for airframe inspections, and the propeller manufacturer’s component maintenance manual (CMM) and an aircraft specific propeller maintenance manual (PMM) for propeller inspections.
The CMM and PMM provided the primary source of information on maintenance requirements and serviceability limitations of the propeller and its blades. Contained within the introduction chapter of the CMM was the statement:
Use qualified personnel and good engineering practice for all procedures and standard practices used in this manual.
The PMM inspection and check section included the following requirements in a section titled ‘Bird Strike or other Impact Damage’:
1. Propellers which have had, or are thought to of had a bird strike or other impact must be examined immediately.
2. Refer to propeller blade damage limits for allowable damage limits and repairs. Refer to CMM 61-10-39 Check. If the damage is within the allowable limits the propeller can stay in service.
3. If the damage is more than the allowable limits, but within the repair limits, a ferry flight may be allowed. The operator should write a ferry flight request on a concession form and send it to Dowty Propellers. Refer to Service Letter E340.
4. Equipment sent for repair must be clearly identified with the reason why.
The CMM 61-10-39 check section described the procedure of examination as a two-level process, consisting of a general check of all parts and a special check of specific parts. The section also contained non-destructive testing (NDT) techniques to be used on the blade assemblies and it provided blade damage limits relevant to blade location.
The CMM general check procedure included a section titled ‘Impact Damage’, which applied to birdstrikes. This section stated:
1. If the propeller has had impact damage, do the applicable visual and NDT inspection procedures given for the area of impact.
2. If the position of the impact will cause impact damage to other propeller components, do the applicable visual and NDT inspection procedures given for ‘secondary’ area of impact…
3. If it is not clear where the damage is, or if there is doubt concerning secondary impact damage contact Dowty Propellers.
The ATSB found ambiguity in the CMM procedures for assessing blades following a birdstrike impact. It was not readily apparent from the procedures whether the bird contact alone would constitute damage or whether subsequent blade NDT was required. As a result, the ATSB sought clarification from the manufacturer. The manufacturer advised:
Generally, the intent is that there must be signs of damage before NDT is required.... Not many impacts leave no trace at all and generally, anything that is going to cause structural damage will have an associated visual indicator…
Dowty would not consider evidence of animal matter as damage however it would be an indication that there had been an impact and that further investigation may be needed, again we would always recommend caution if there was any doubt.
Therefore, according to the manufacturer, the presence of feathers and dust marks (a visual indicator), while not displaying visible damage, may require further investigation.
Additional information
In 2011, the operator applied to the Civil Aviation Safety Authority (CASA) for approval to allow flight crew to undertake birdstrike inspections of aircraft. The CASA response (9 February 2012) highlighted the requirements of the Civil Aviation Safety Regulation Part 42 and the associated Part 42 Manual of Standards. Guidance on the continuous airworthiness requirements was provided,[3] including examples of situations that would exclude flight crews’ ability to undertake inspections, as well as situations where flight crew inspections would be allowed.
CASA determined that where a specific birdstrike inspection was required by a manufacturer, that inspection would be deemed an engineering maintenance task and outside the scope of flight crew approved maintenance. Where specific inspection requirements did not exist and where there had been no effect on the aircraft’s performance, external inspection by flight crews to determine if damage had been sustained was acceptable. CASA stated that the operator needed to submit its proposed procedures to CASA’s oversighting office for the operator.
Based on the CASA advice, and believing there was no manufacturer specific inspection, the operator developed a draft birdstrike inspection procedure for flight crew. The draft procedure (and associated external inspections) was submitted to CASA’s oversighting office for the operator and, following minor amendments, was issued to flight crew in an operations notice on 24 February 2012, and incorporated into the operator’s policy and procedures manual in April 2012.
Following the 9 January 2015 occurrence, the operator advised the ATSB that it had misinterpreted the requirements in the CASA letter. The operator also advised that when it developed its birdstrike procedure, it relied on the aircraft manufacturer’s AMM and information from the aircraft manufacturer. It inadvertently did not consider the propeller manufacturer’s PMM. As noted in in the previous section, the PMM documented a birdstrike inspection.
The operator advised the ATSB that it had approached the propeller manufacturer to include tap testing of the blade surface as part of the engineering birdstrike inspection procedure. The manufacturer indicated that a tap test of the blade is of very limited value because it did not give a sufficiently definitive result and risked not detecting blade delamination, except for the blade erosion strip.
Wildlife hazard management requirements and guidance
General requirements and guidance
A number of regulations, standards, and guidelines apply to wildlife hazard management at airports. The International Civil Aviation Organization established the standards for the management of collisions between wildlife and aircraft. It also provides guidance on effective wildlife management programs.
Within Australia, CASR 139 required a certified aerodrome to have an aerodrome manual, which must include details regarding bird and animal hazard management. The Manual of Standards (MOS) for Part 139 provides more detailed requirements. These included a requirement that, where regular monitoring confirmed the existence of a bird or animal hazard, or at the direction of CASA, the aerodrome operator must develop a bird or animal hazard management plan. The plan had to be developed by a suitably qualified person such as an ornithologist or biologist, and had to address the following factors:
hazard assessment, including monitoring action and analysis;
pilot notification [reporting];
liaison and working relationships with land use planning authorities;
on-airport bird and animal attractors which provide food, water or shelter
suitable harassment methods; and
an ongoing strategy for bird and animal hazard reduction, including provision of appropriate fencing.
Advisory Circular (AC) 139-26(0) Wildlife hazard management at aerodromes provides further guidance information about managing wildlife hazards at aerodromes. It states that that once a wildlife hazard is identified, appropriate and effective treatment should be employed. Treatment methods fall into two categories:
pre-emptive (such as removal of food sources, maintenance of grass, etc.) and where necessary
active (such as scare tactics using horns, siren, or dogs).
, refers to the galah (reproduced in the Appendix). The information sheet advises that all bird management strategies should seek to make an airport as undesirable as possible to birds through habitat modification. With regard to galahs, amongst various suggestions, it recommends that:
a tall grass policy (30 cm) be maintained as galahs find it difficult to see approaching predators
manage grasslands to limit production of seeds.
Additional active management strategies that can be used to disperse and control the birds include:
use of pyrotechnics (cracker shells), portable distress callers, sirens, lights and vehicles
use of trained animals (birds of prey, dogs, etc.), and where necessary, and permitted, culling may be required.
Airport information
Moruya was a certified, uncontrolled, two runway airport situated close to the coastline (Figure 1).
The airport had a bird and animal (wildlife)[4] management program. This includes daily inspection of the airport with reporting on wildlife activity, low level harassment with a vehicle to disperse wildlife, and maintenance of grass areas to minimise or deter habitation. The airport coordinator advised that the local galahs tended to stay close to the buildings and trees, but it was not usual for them to be in the runway area. The grass around the runway was long and had been scheduled for cutting that day. The airport coordinator considered the longer grass may have attracted the galahs to feed on the grass seeds.
The airport’s records of wildlife strikes indicated they were not seasonal, with birdstrikes occurring throughout the year, over the previous five years. In 2014, however, the only three reported birdstrikes were confined to the first quarter of the year (January to March). None of these involved galahs.
A review of the 2014 annual report revealed a consistent number of galahs resided at the airport, with between two and 10 birds observed regularly. Their activity was predominantly around the terminal area in the early morning, usually departing before 0800. There was only one instance of flocking behaviour by galahs in the 2014 report. That occurrence was in February 2014 when large groups of about 32 galahs were observed coming in from a nearby camping area to graze near the terminal building, and departing by about 0800.
The presence of birds at Moruya Airport was frequent and significant enough for the aeronautical information package, En Route Supplement Australia, to include an additional information note that a bird hazard exists.
The ATSB compared birdstrike rates per 10 000 aerodrome movements for Moruya against other regional aerodromes, and the birdstrike rates for Moruya were considerably lower than most.
Other occurrences
A review of the ATSB occurrence database for the period 1977 to 2014 did not reveal any additional blade failures or in-flight blade tip failures for the propeller type due to a birdstrike.
On the morning of 9 January 2015, the crew of a Regional Express operated Saab 340B aircraft, registered VH-OLM, and were conducting a series of scheduled passenger flights between Sydney, Moruya and Merimbula, New South Wales. The first officer was the pilot flying on the Sydney to Moruya sector.
At about 0955 Eastern Daylight-saving Time, a visual, straight-in approach was conducted to land on runway 18[1] at Moruya. The aerodrome forecast for arrival at Moruya showed a 7 kt wind from the north-east, good visibility and cloud from 2,000 ft above the aerodrome.
After touchdown, as the aircraft slowed through 80 kt, the captain took control of the aircraft for the taxi to the terminal in accordance with normal company operating procedures. The crew reported that, shortly after the captain took control, a large flock of galahs[2] took off from the grass to the west (right) of the runway and flew at a low height over the runway eastbound (Figure 1). In anticipation of a birdstrike, the captain increased wheel braking and applied reverse thrust on both engines. Prior to reaching the galahs forward thrust was selected. Despite that action, about halfway down the runway the first officer observed birds had impacted the aircraft.
Figure 1: Moruya Airport showing aircraft and galah flock direction of travel and approximate impact point
Source: Google maps (Modified by the ATSB)
On reaching their designated parking area, and in accordance with the operator’s birdstrike procedures, the flight crew carried out testing of the ice protection system before the engines were shut down, with no issues identified. Once the passengers who were disembarking at Moruya had left the aircraft, the first officer commenced an external inspection of the aircraft. The captain notified the airport reporting officer of the birdstrike. The airport safety officer subsequently found around 10 bird carcases on the runway.
The first officer found clear evidence of multiple birdstrikes on the right side of the fuselage, and the right engine and propeller, in the form of blood staining and bird carcass debris. One of the left engine propeller blades also displayed blood staining and white powder marks, consistent with a birdstrike. Despite the bird impacts, no evidence of ingestion into the engines or physical damage to the aircraft or propeller blades was observed.
The captain and the first officer reported that they subsequently carried out a detailed visual examination of the birdstrike-affected blades. The examination included rotating the propellers so that the forward and aft blade surfaces could be inspected for cracking, buckling, chips, dents or deformation along each affected blade’s leading edge. When no damage was identified, the captain contacted the operator for further technical advice and the crew were subsequently cleared to continue with the flight schedule.
The crew then operated the aircraft from Moruya to Merimbula. After engine shutdown at Merimbula, the first officer opened the forward left door and observed that the tip of one of the left propeller blades had detached (Figure 2). The aircraft was declared unserviceable and grounded.
There were no reported injuries to the crew or passengers. No damage to the aircraft structure was identified as a result of the loss of the blade tip.
Figure 2: Left engine propeller showing damaged blade tip on arrival at Merimbula
The sources of information during the investigation included the:
flight crew
aircraft operator (Regional Express)
propeller manufacturer
propeller overhaul organisation
Moruya airport operator
United Kingdom Air Accidents Investigation Branch
Swedish Accident Investigation Authority
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.
A draft of this report was provided to the captain, first officer, Regional Express, Moruya airport operator, Civil Aviation Safety Authority (CASA), Dowty Propellers, and the United Kingdom Air Accidents Investigation Branch.
Submissions with comments were received from the operator, CASA and the propeller manufacturer. The submissions were reviewed and, where considered appropriate, the text of the report was amended accordingly.
Safety issues and 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.
Regional Express
As a result of this occurrence, Regional Express advised the ATSB that it had undertaken pro-active safety action through issuing the following:
Notice to aircrew NOTAC 091/15, REPORTING OF BIRD AND WILDLIFE STRIKES - REISSUED. Which stated:
If there is any evidence of impact (blood/feathers/dust) on the propellers following wildlife strike the aircraft must not depart until an engineering inspection is complete. In addition to the requirements of PPM 13.1 1-Bird Strike, an AML [aircraft maintenance log] must be raised for wildlife impact with the propeller. All bird and wildlife strikes or suspected strikes encountered on approach/departure, take-off/landing should be reported to the Network Ops Centre (NOC) as soon as practicable following a strike. The NOC will then inform the aerodrome operator to enable immediate dispatch of the ARO [aerodrome reporting officer] to inspect the runway and vicinity of the airport in the effort to locate and remove any animal remains, as well as assisting in the identification of the species for wildlife management within the region. The SMS requirements remain unchanged.
Notice to engineers NOTEM 83, Bird Strike Inspections. Which stated:
Until further notice if a bird (wildlife) strike is reported and there is evidence of impact (blood/feathers/dust) on the propeller then the aircraft must not be released to service until both the CAM [continued airworthiness manager] and Chief Pilot have given approval. AML is required to be raised for any event where there is evidence of impact on the propeller.
Engineering technical notice TN-SAAB-6100-008-15, Propeller Bird Strikes. Which stated:
1. Introduction
This Technical Notice is issued to provide information for engineers dealing with aircraft bird strikes involving contact with propeller or any other impact experienced by the propeller whilst installed.
2. Content
When an aircraft is reported to have experienced a bird strike and there is evidence of contact with the propeller an AML must be raised and an engineering inspection of the propeller must be conducted IAW the applicable maintenance manual.
For Dowty propellers refer to the applicable Maintenance Manual and Component Maintenance Manual, a flow chart is provided on page 2 of this TN to help engineers perform the required inspection and make airworthiness assessment for Dowty propellers.
For the Hamilton Sundstrand propeller refer to the Maintenance Manual P5199, CHECK, Inspection After Impact procedure. A copy of this procedure is included on page 3 of this TN. Note: It is a requirement to check the blade track as part of this procedure.
The same procedures should be used for any report of impact experienced by the propeller while it is installed.
These notices were subsequently included in relevant manual updates.
Appendix A: ATSB Bird Information Sheet No 6
Findings
From the evidence available, the following findings are made with respect to the damage and subsequent propeller blade tip separation associated with the birdstrike occurrence involving a Saab 340B, registered VH-OLM, at Moruya Airport, New South Wales on 9 January 2015. These findings should not be read as apportioning blame or liability to any particular organisation or individual.
Contributing factors
The impact from multiple galahs almost certainly reduced the structural integrity of a propeller blade, resulting in the separation of its tip during the subsequent flight.
Other factors that increased risk
The permitting of flight crew to carry out post birdstrike inspections was outside the approval of the regulator and propeller manufacturer, and reduced the likelihood of identifying serviceability issues.
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
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.
On 4 January 2015, the pilot of a Beechcraft 76 aircraft, registered VH-ZUA (ZUA), commenced a ferry flight from Archerfield to the Gold Coast, Queensland. The private flight was conducted under the visual flight rules (VFR), and the pilot was the sole person on board. The aircraft departed Archerfield at about 1200 Eastern Daylight Time (EDT), and climbed to a planned cruising level of 1,500 ft above mean sea level.
Figure 1: Gold Coast VTC
Source: Airservices Australia: Visual Terminal Chart modified by the ATSB
At about 1210, as ZUA approached the change of frequency boundary (Figure 1) just north of Dreamworld, the pilot changed to the area frequency (119.5 MHz) on COMM 1[1] with the Southport CTAF frequency (119.0 MHz) in the standby section of the Garmin 530. As he approached Southport airport, the pilot moved the standby frequency (119.0 MHz) into the active box and as required, broadcast the aircraft’s position and intentions. The CTAF frequency is common to both Southport Airport and the nearby Sea World helipad (Figure 1).
At about 1212, the pilot of an AS350 helicopter, registered VH-SWX (SWX) prepared to depart from Sea World, Queensland, for a 15 minute local commercial scenic flight. The first sector was from Sea World to overhead the Robina shopping centre (Figure 2). On board were the pilot and 5 passengers.
The pilot obtained the Gold Coast automatic terminal information service (ATIS) prior to becoming airborne at about 1215 and broadcasting his intentions on the Sea World CTAF frequency of 119.0 MHz (the same frequency as the Southport CTAF). As a small sector of the scenic flight was to be conducted in the Gold Coast control Zone, the pilot obtained a transponder code from Gold Coast Ground air traffic control soon after the helicopter had departed.
At about 1220, as ZUA neared the Q1 VFR reporting point (Figure 1), the pilot requested and obtained a clearance from the Gold Coast tower controller to enter the control zone. The pilot acknowledged and read back the clearance, which was to track from his present position direct to the Gold Coast airport at 1,500 ft. Soon after, the tower controller issued the pilot a Safety Alert, advising of traffic in his 10 o’clock position[2], 2 NM and tracking west (toward ZUA) at an unverified level of 1,400 ft (Table 1). The pilot acknowledged the Safety Alert, advising the tower controller that the traffic was in sight.
Figure 2: Approximate flight path of ZUA and SWX
Source: Airservices Visual Terminal Chart modified by ATSB
Table 1: Summary of radio communication by ZUA and SWX
Time
Action
Frequency MHz
Content
1215
SWX departed helipad for a 15 minutes scenic flight
CTAF 112.3 CTAF 119.0GC Ground (SMC) 121.8
COMM 2 (Obtained ATIS from Gold Coast)COMM 1 Airborne Sea World; on climb to 1,500 tracking for Robina.(COMM2 was tuned to Gold Coast Ground to obtain a transponder code for the sector of the flight which transited through controlled airspace).
1219.58
Approaching Q1, ZUA to TWR
118.7
Advised TWR that ZUA was approaching Q1, 1,500 inbound and in receipt of the current ATIS and requested a clearance to enter the Control Zone.
1220.14
Gold Coast TWR to ZUA
118.7
Cleared ZUA direct to the Gold Coast, 1,500 with an expectation for a straight in approach to RWY 14.
1220.22
ZUA to TWR
118.7
Pilot read back the clearance
1220.28
TWR to ZUA
118.7
Issued ZUA with a SAFETY ALERT for traffic in their 1000 position, 2 NM and tracking west unverified level 1,400 ft
1220.51
ZUA to TWR
PIC reported traffic sighted
1221.18
Centre to ZUA
119.5
Issued ZUA with a SAFETY ALERT for traffic in their 10 o’clock position same level, and half a mile. Centre called twice but did not receive a response from the PIC of ZUA.
1221.29
Centre to TWR
Issued a SAFETY ALERT to TWR. TWR advised that the pilot of ZUA had been issued a SAFETY ALERT for traffic
1221.42
Near Collision
1221.57
ZUA to TWR
118.7
Reported to TWR that he had just taken evasive action to avoid the helicopter, and was now tracking to the Gold Coast again
1223.40
SWX to TWR
118.7
PIC obtains clearance to enter the Gold Coast control zone and also requests further information about ZUA
1224.00
SWX to TWR
118.7
PIC advised TWR that a fixed wing aircraft [ZUA] had passed from behind about 30 ft over the top of the helicopter. He had made two calls on 119.0 to make contact with the pilot but had not received a reply
Source: Airservices Australia
Also noticing the short-term conflict alert (STCA) (Figures 3 and 4) on the air situation display, the Brisbane Centre controller twice attempted to make contact with ZUA which was still in uncontrolled airspace; but there was no response. The controller then contacted the Gold Coast tower controller via the internal coordination line, to confirm that a safety alert had been issued. The tower controller advised the Brisbane Centre controller that a safety alert had already been issued and the situation was under control.
Soon after, while distracted by entering and changing frequencies on both COMM 1 and COMM 2, the pilot of ZUA had lost sight of SWX and turned his attention to visually re-acquire the helicopter. The pilot then realised that the helicopter was not flying parallel to his course as he had initially thought; but was on a collision course with ZUA and at a similar altitude. The pilot initiated a short climb and a steep right turn in ZUA. He did not see SWX during this evasive manoeuvre, so turned left and continued to the Gold Coast as cleared, and advised the tower controller of the conflict and subsequently landed.
Figures 3: Radar surveillance data
Time: 2.21.37 ZUA at 1,500 ft; SWX 1,500 ft; about 100 m horizontally STCA – Short term conflict alert
Source: Airservices Australia
Figures 4: Radar surveillance data
Time: 2.21.42 Near collision ZUA at 1,500 ft; SWX 1,500 ft; Nil horizontal distance showing on radar
Source: Airservices Australia
The traffic collision avoidance system (TCAS) on board the helicopter did not alert the pilot to the potential conflict, possibly because ZUA overflew the helicopter from behind, which may have shielded the TCAS aerial.
VH-ZUA radio equipment
ZUA had Garmin 530 and Garmin 430 units installed.
VH-SWX radio equipment
SWX had two communication navigation (COMM NAV) units installed, also allowing the pilot to have two active and two standby radio frequencies selected. SWX also had a terrain collision avoidance system (TCAS) fitted.
VH-ZUA pilot experience and comments
The pilot had around 270 hours total time, with about 38 hours on the B76 type aircraft. He had been undergoing training for a multi-engine command instrument rating (MECIR), and this positioning flight was his first solo flight in the aircraft.
He recalled being advised about conflicting traffic by the Gold Coast tower controller, and recalled having responded ‘traffic sighted’. He reported when he first sighted SWX, he incorrectly thought it was tracking parallel to ZUA, and did not appear to be getting any closer. Hence, he turned his attention to trying to reset the CTAF of 119.0 MHz on COMM1, to enable him to communicate with the helicopter. At this stage, he had changed the selected frequencies to having the Gold Coast tower frequency on COMM 1, and the ATIS and CTAF on COMM 2. Then he changed COMM 2 to have the Gold Coast Ground frequency selected in preparation for taxi after landing.
During the process of entering, changing and selecting frequencies on the two COMM sets, his attention had shifted from keeping the helicopter in sight, to attempting to communicate with it and arrange clearances.
He reported that at this stage SWX appeared to have ‘turned toward him’[3] and as he watched it he realised it was heading directly at ZUA. He commenced evasive action by initiating a brief climb and a steep turn to the right. His intention was to parallel the track of the helicopter and keep it in sight.
Additionally, he reported that his sleep the night before had been disturbed.
VH-SWX pilot experience and comments
The pilot held a Commercial licence (Helicopter) and had around 6,500 hours flying experience. The pilot commented that the first awareness of ZUA was when it passed over the helicopter from behind.
Safety message
This incident highlights the importance of having the correct radio frequencies planned and correctly set up prior to and during flight and the need for vigilance when keeping conflicting traffic in sight. Pre-flight preparation is an essential part of safe flying operations and can prevent a loss of situational awareness and avoid the pilot’s attention being focused for long periods inside the cockpit.
CASA has developed the Look out! Situational awareness DVD for pilots to learn more about the safety-critical skills that makes up situational awareness. There is a strong emphasis on the need to prepare and plan for every flight. The DVD gives a definition of situational awareness of “what’s happened, what’s happening and what might happen”.
The CASA DVD is available from the CASA online store.
Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, a limited-scope, fact-gathering investigation was conducted in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.
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
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.
On 28 December 2014, at about 1312 Eastern Daylight-saving Time, the pilot of a Robinson R44 helicopter, registered VH-JKF (JKF), departed for a scenic flight from Essendon Airport, Victoria. The helicopter travelled as the lead helicopter ‘in-company’ with another helicopter and the pilot of JKF was responsible for making all radio calls on behalf of both helicopters.
At about 1315, the student pilot and instructor of a Cessna 172 aircraft, registered VH-EVR (EVR), taxied for a training flight to Point Cook. At about 1323, EVR was cleared to track direct to Point Cook and subsequently cleared for take-off from runway 17. The pilot of JKF heard the communications with EVR while he was briefing passengers for landing and he did not hear the runway direction in the instructions issued to EVR. He had observed the wind over the city coming from a northerly direction, and assumed EVR would be taking off from runway 35.
At about 1325, the controller instructed JKF and company to track towards the runway 17 threshold and to report sighting the Cessna in the take-off roll. The pilot of JKF read back the instruction, but inadvertently tracked towards the 35 threshold. After reporting the Cessna in sight, JKF was directed to pass behind it.
About 16 seconds later, both helicopters were asked to confirm they had the aircraft in sight and the instructor of EVR observed JKF in close proximity. The pilot of JKF then realised that he was tracking to the incorrect threshold and slowed the helicopter to pass about 75 m behind and 100 ft below EVR.
This incident serves as a reminder to keep a good lookout at all times, including in Class C airspace.
On 2 January 2015, at about 1400 Eastern Daylight-saving Time, the pilot of a Starduster SA300 aircraft, registered VH-XRS (XRS), commenced pre-flight preparations for a local private flight at Tyabb Airport, Victoria (Figure 1). The pilot of XRS observed the windsock indicating calm conditions. The pilot elected to follow the airport operator’s procedures for nil wind, and use the preferred runway, runway 17. During the next 30 minutes, no aircraft operated in the circuit. The pilot did not hear any broadcasts on the common traffic advisory frequency (CTAF) during that time.
Figure 1: VH-XRS
Source: Aircraft owner
At about 1430, a Cessna 152 aircraft, registered VHNKL (NKL), conducted pre-taxi checks prior to a dual training flight. The instructor and student pilot planned to conduct circuits at Tyabb. During the pre-taxi checks, the student pilot selected Tyabb common traffic advisory frequency (CTAF) on the radio, and checked the squelch,[1] to verify that the radio was operating. The instructor reported that the wind was less than 5 kt and from the east-northeast. Although the preferred runway in those conditions was runway 17, they elected to use runway 35. This runway selection provided an opportunity for the student to practice backtracking on the runway. The student pilot broadcast taxiing for runway 35 and commenced taxiing south from the apron towards the threshold of runway 35.
The pilot of XRS did not hear the taxi broadcast from the pilot of NKL, or sight NKL at that time, and commenced taxiing from the hangar to the apron area. At the apron, the pilot of XRS conducted engine run-ups, then broadcast taxiing for runway 17 and commenced taxiing north towards the threshold of runway 17. Neither the student pilot nor instructor of NKL heard the taxi broadcast from the pilot of XRS.
The student pilot of NKL then broadcast entering and backtracking runway 35, and NKL entered the runway and taxied to the southern threshold. After reaching the threshold, the student pilot turned the aircraft, broadcast lining up and departing runway 35 for circuits. The pilot of XRS did not hear that broadcast, but was by then at the threshold of runway 17 and broadcast lining up and departing runway 17. The pilots of NKL did not hear that broadcast.
The pilot of another Cessna aircraft, then at the apron, heard both ‘lining up’ broadcasts on the CTAF. This pilot immediately attempted to broadcast a conflict alert, to advise the pilots that the aircraft were on opposing runways. The pilots of XRS and NKL did not hear that broadcast. The student pilot of NKL broadcast ‘rolling runway 35’ at the same time, which may have over-transmitted the other call.
When about 500 m along the runway and at rotate speed, the instructor of NKL pointed out the airspeed to the student and the aircraft lifted off. The instructor then sighted XRS in the take-off run on the opposite runway. The instructor immediately took control of the aircraft from the student and commenced a left climbing turn, while keeping XRS in sight (Figure 2).
When about 300 m along the runway, XRS lifted off. When at about 10 ft above ground level, the pilot of XRS sighted NKL, about 300 m ahead and banking to the left. He also commenced a left turn to increase separation between the two aircraft, which then passed about 50 m from each other, with NKL slightly higher than XRS. The pilot of XRS then joined the circuit for runway 35 on the crosswind leg, and broadcast that he was joining the circuit to return to land at Tyabb.
Figure 2: Tyabb Airport and aircraft tracks
Source: Google earth
The instructor of NKL then requested a radio check, which the pilot of the other Cessna operating in the area heard and responded to.
Radio broadcasts
The CTAF at Tyabb was not recorded and the ATSB was unable to verify broadcasts made, other than those reported by the pilot of another aircraft operating at the airport at the time. The CTAF did not have an aerodrome frequency response unit (AFRU). An AFRU assists in indicating selection of the correct VHF frequency at non-towered aerodromes, by automatically responding with either a pre-recorded voice message, if no transmission has been received in the last five minutes or otherwise a ‘beep-back’, on the CTAF.
Preferred runway in nil wind conditions
The En Route Supplement Australia (ERSA) for Tyabb,[2] indicated under noise abatement procedures, that the preferred runway was 35/17 and that runway 08/26 was only to be used when operationally required. The page layout may have been considered to be misleading with 35 printed above 17, but that was not designed to imply that runway 35 was the preferred runway in the event the wind did not favour either direction.
The Chief Flying Instructor at Tyabb provided the ATSB with a copy of the runway diagram and local instructions. He reported that this was issued to pilots operating at the airfield. In the notes section, it stated ‘Preferred runway in nil wind conditions, Runway 17’. Both the pilot of XRS and the instructor of NKL were local pilots and aware of the local instruction for the preferred runway in nil- or crosswind conditions.
Pilot comments
Pilot of XRS
After the incident, as XRS was returning to land, the pilot of XRS heard the second Cessna aircraft pilot broadcast lining up and departing. He was able to hear broadcasts from aircraft on the ground while XRS was in the air, but is unsure whether an aircraft at one end of the runway could hear a broadcast from an aircraft at the opposite end. The VHF radio requires line-of-sight, and a pilot in an aircraft at the threshold at one end of the runway is unable to see an aircraft at the opposite threshold, due to a slope in the runway.
Pilot of other Cessna
The pilot of the Cessna at the apron reported that the radio transmissions from XRS were of poor quality.
Instructor of NKL
The instructor provided the following comments:
He held a formation endorsement, and during formation flying there was an emphasis on keeping the other aircraft in sight. When he sighted XRS, he conducted a left turn to maintain visual contact with XRS.
He did not hear any broadcasts from the pilot of XRS. After the incident, he heard the pilot of the other Cessna make the standard broadcasts.
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.
Aero club
As a result of this occurrence, the local aero club has advised the ATSB that they are taking the following safety actions:
Communication
The incident will be discussed at a monthly meeting, emphasising the use of the preferred runway in nil wind conditions. Pilots and instructors will be reminded that operating outside of the normal and expected procedures, requires higher levels of alertness.
ERSA
The ERSA entry for Tyabb will be amended as the layout may have been misleading.
AFRU
They will review the installation of an AFRU and possible means of recording the CTAF.
Accident emergency plan
The emergency management plan will also be reviewed.
Safety message
As detailed in the booklet A pilot’s guide to staying safe in the vicinity of non-towered aerodromes, ATSB research found that, between 2003 and 2008, there were 709 airspace-related events at, or in the vicinity of non-towered aerodromes. This included 60 serious incidents and six accidents (mid-air and ground collisions). Most of the 60 serious incidents were near mid-air collisions.
Issues associated with unalerted see-and-avoid have been detailed in the ATSB research report Limitations of the See-and-Avoid Principle. The report highlights that unalerted see-and-avoid relies entirely on the pilot’s ability to sight other aircraft. Broadcasting on the CTAF is known as radio-alerted see-and-avoid, and assists by supporting a pilot’s visual lookout for traffic. An alerted search is more likely to be successful as knowing where to look greatly increases the chances of sighting traffic.
11.5 Pilots should be mindful that transmission of information by radio does not guarantee receipt and complete understanding of that information. Many of the worst aviation accidents in history have their genesis in misunderstanding of radio calls, over-transmissions, or poor language/phraseology which undermined the value of the information being transmitted.
11.6 Without understanding and confirmation of the transmitted information, the potential for alerted see-and-avoid is reduced to the less safe situation of unalerted see-and-avoid.
In this incident, the instructor of NKL diverged left on sighting XRS. When the pilot of XRS sighted NKL, it was already banking to the left and therefore he was able to also conduct a left turn to increase separation. However, the Civil Aviation Regulations 1988 – Reg162, Rules for prevention of collision,[3] stated:
When two aircraft are approaching head-on or approximately so and there is danger of collision, each shall alter its heading to the right.
The risk of reduced separation events can be minimised through good communication by pilots. Most importantly, a good visual lookout should be maintained at all times, particularly when operating at aerodromes where the carriage of a radio is not mandatory.
A local procedure that improves safety, such as a preferred runway, should be well-documented, and communicated to all pilots operating at the aerodrome.
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
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.
