On 18 April 2015, a Jabiru J250 aircraft, recreational registration 19-7621, collided with terrain near Gympie, Queensland and on 23 May 2015, a Thunderbolt aircraft, recreational registration 19-8601, collided with terrain near Cessnock, New South Wales.
Recreational Aviation Australia (RA-Aus) is responsible for investigating these two accidents. As part of its investigations, RA-Aus requested technical assistance from the Australian Transport Safety Bureau (ATSB) in the examination of data from two multi-function display units recovered from the respective accident sites. To protect the information supplied by RA-Aus to the ATSB and the ATSB's investigative work to assist RA-Aus, the ATSB initiated an investigation under the Transport Safety Investigation Act 2003.
The ATSB successfully recovered data from the avionics devices and provided the data to RA-Aus on 04 May 2016. This completed the ATSB’s support of the RA-Aus investigation.
Any enquiries relating to the accident investigations should be directed to RA-Aus at: www.raa.asn.au.
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The information contained in this web update is released in accordance with section 25 of the Transport Safety Investigation Act 2003.
On 23 June 2015, at about 0638 Western Standard Time (WST), a Bombardier DHC8, registered VHXFQ, departed from Perth, on a charter flight to Darlot, Western Australia. The first officer was the pilot flying, and the captain was the pilot monitoring.[1]
The aircraft arrived in the Darlot area soon after 0800. As they neared their descent point, the crew could see that a layer of low cloud had formed over the Darlot area. Nonetheless, conditions above the low cloud were clear and the crew expected to be able to land. The crew conducted an RNAV (GNSS)[2] approach to runway 14, but contrary to their earlier expectations, they were unable to establish the required visual references, due to the low cloud. The crew conducted a missed approach accordingly.
Rather than make any further attempts to land at Darlot, the crew commenced a diversion to Leinster. Leinster was their planned alternate aerodrome, located about 30 NM west of Darlot. Advice from the crew of another aircraft on the ground at Leinster, suggested that the weather at Leinster was deteriorating. Despite the deteriorating conditions, it still appeared probable that an approach would be successful.
The crew positioned the aircraft for an RNAV (GNSS) approach to runway 28 at Leinster, which required minimal manoeuvring from their inbound track from Darlot. The approach proceeded normally, but the crew were unable to establish the required visual references due to low cloud, and conducted a missed approach.
Based upon what the crew had been able to see during their approach to Leinster, and advice about the conditions from the other crew on the ground, the crew elected to attempt an approach to the reciprocal runway (runway 10). Although there was substantial cloud over the eastern end of the aerodrome, the conditions over the western end appeared to be more favourable.
The crew then conducted an RNAV (GNSS) approach to runway 10. During the later stages of that approach, while the aircraft was still clear of cloud, but approaching wispy low cloud ahead, an EGPWS ‘terrain terrain pullup pullup’ warning triggered (see section titled EGPWS warning). The crew believed at the time that the EGPWS warning was spurious, but commenced a missed approach in response to the warning.
Following the missed approach, the captain assessed that low cloud was continuing to move over the area from the south. Given the increasing extent and low base of the cloud, the captain determined that further attempts to land at Leinster were unlikely to be successful.
Based upon the conditions that the crew had encountered since arriving in the Darlot and Leinster area, the captain had continued to monitor Flight Management System time, distance and fuel information, as it related to other diversion options. The conditions to the north appeared to be clear, with no signs of the low cloud that was apparent over Darlot and Leinster. Clear conditions to the north were consistent with the captain’s interpretation of the weather information reviewed as part of the flight planning process. Accordingly, the crew elected to divert to Wiluna, about 78 NM to the north-north-west of Leinster.
Having commenced a diversion to Wiluna, the crew obtained updated weather information from air traffic control to confirm that the conditions at Wiluna were suitable. Other pilots in the vicinity also advised the crew that conditions in the Wiluna area appeared to be clear. The flight proceeded to Wiluna, and landed uneventfully at about 0925.
The aircraft landed with about 600 lbs of fuel remaining, above the operator’s minimum fixed fuel reserve of 450 lbs. The crew added fuel at Wiluna and the aircraft returned to Darlot later that morning, when the weather at Darlot had cleared sufficiently.
Pre-flight planning and forecast weather
About an hour prior to the planned departure time, the captain had reviewed weather information pertinent to the flight, including relevant terminal area forecasts (TAFs).[3] There was no TAF available for Darlot, so the captain was required to nominate an alternate aerodrome, and carry sufficient fuel to safely divert to that aerodrome. The captain reviewed the TAF for Leinster, and was satisfied that Leinster was a suitable alternate aerodrome, so the flight was planned on that basis.
The Leinster TAF (Figure 1) indicated that if the crew diverted there after attempting to land at Darlot, they could expect broken[4] (BKN) cloud to be developing (from 0800), with a base at 2,000 ft above the aerodrome. The visibility was forecast to remain 10 km or more, and the wind was forecast to remain light, from a south to south-easterly direction.
Figure 1: Leinster TAF referred to during pre-flight planning[5]
Source: Aircraft operator
While planning the flight, the captain was mindful that although Leinster was a suitable alternate aerodrome to Darlot, the relatively proximity of the two aerodromes meant that similar conditions could reasonably be expected at both. Accordingly, the captain reviewed the TAFs for other aerodromes in the general area, to provide options in the event that unsuitable weather conditions were encountered at both Darlot and Leinster.
The captain reviewed the TAF for Wiluna (Figure 2), which indicated that Wiluna would be suitable if the crew were unable to land at Darlot or Leinster. The TAF for Wiluna forecast CAVOK[6] conditions, with scattered[7] (SCT) cloud expected to develop from 1000, with a base at 2,000 ft above the aerodrome.
Figure 2: Wiluna TAF referred to during pre-flight planning
Source: Aircraft operator
The captain also reviewed relevant area forecasts (ARFOR)[8] in preparation for the flight, in order to build an appreciation of the overall weather picture. This included the ARFORs for areas 61 and 66 (Figure 3). In broad terms, the ARFORs indicated that the crew could expect low cloud and fog in area 61, and the southern part of area 66, until 0900. Beyond 0900, some cloud was still forecast in both areas, but with a higher base and unlikely to have any operational implications for the flight.
Figure 3: Extract from Planning Chart Australia showing relevant locations and ARFOR area boundaries
Source: Airservices Australia, with additions by the ATSB
Fuel planning
Based upon assessment of the weather, the captain elected to load additional fuel, in excess of the minimum regulatory fuel requirements. This was to ensure that options were available if the crew were unable to land at Darlot or Leinster. Although Wiluna did not appear on the flight plan, the captain elected to load sufficient fuel to divert there if necessary. According to the flight plan, the minimum fuel required for the flight was 2,574 lbs, which included reserve requirements and sufficient fuel for a diversion to Leinster. In view of the conditions, the captain elected to increase the fuel load to the maximum amount that could be carried given the expected payload. This amounted to a fuel load of 3,450 lbs.
Actual weather conditions at Leinster
The actual weather conditions encountered by the crew at Leinster were worse than had been forecast on the TAF. Most notably, while the TAF forecast cloud with a base at 2,000 ft above the aerodrome, the crew encountered cloud with a base around 400 to 500 ft above the aerodrome.
The Leinster aerodrome weather reports reflected the changing conditions that took place during the morning at Leinster (Figure 4). While the 0800 METAR[9] stated no cloud detected (NCD), a SPECI[10] was issued at 0827 indicating that broken cloud had formed, with a base at 400 ft above the aerodrome. This would have been around the time that the aircraft arrived in the Leinster area. The extent of cloud cover had grown by 0900, to become overcast[11] (OVC) with a base at 400 ft above the aerodrome. After 0900, the cloud slowly lifted and cleared. According to the aerodrome weather reports, the visibility remained 10 km or more throughout the morning.
Figure 4: Selected Leinster aerodrome weather reports from morning of the incident flight
Source: Bureau of Meteorology
Amended TAFs. The Bureau of Meteorology issued amended TAFs for Leinster, one at 0826, followed by another at 0840 (Figure 5). Those TAFs indicated that low cloud could be expected (from the time the TAFs were issued), with a base at 800 ft and 500 ft above the aerodrome respectively. Both amended TAFs forecast that the cloud base would lift to 2,500 ft above the aerodrome, from 1000.[12]
Figure 5: Amended TAFs for Leinster, issued at 0826 (upper) and 0840 (lower)
Source: Airservices Australia
EGPWS warning
During the RNAV (GNSS) approach to runway 10 at Leinster, the crew received an EGPWS ‘terrain terrain pullup pullup’ warning. They responded to that warning by commencing a missed approach. At the time the crew received the EGPWS warning, they were clear of cloud and could see the ground beneath, but there was wispy low cloud ahead, partially obscuring their view of the runway environment. The crew were assessing the conditions ahead, and the feasibility of safely continuing the approach, when the EGPWS warning activated. The crew elected to make a missed approach with go-around power, rather than conduct a terrain escape manoeuvre,[13] given that the missed-approach flight path of the aircraft was visually clear of terrain and obstacles.
Subsequent analysis of the flight data by the operator revealed that during the RNAV (GNSS) approach to runway 10, the crew descended prematurely to the relevant Minimum Descent Altitude (MDA).[14] In doing so, the crew descended beneath the 3,100 ft altitude constraint between the intermediate fix (LSTWI) and the final approach fix (LSTWF) (Figure 3). The crew overflew LSTWF just above the MDA, and then levelled momentarily at the MDA. Soon after, a brief and shallow descent developed, at which time the EGPWS warning was triggered. At the time the EGPWS warning was triggered, the aircraft was about 4.5 NM from the runway, and the radio altimeter indicated that the aircraft was slightly less than 500 ft above the underlying terrain.
Figure 6: Excerpt from approach chart and vertical profile of the aircraft (in part) showing where EGPWS warning was triggered
Crew comments
The crew commented that a number of factors in combination probably contributed to their descent below the altitude constraint between LSTWI and LSTWF. These factors are broadly summarised as follows:
Workload during positioning for the approach was high, particularly noting that this was a third approach in relatively quick succession. Although the workload was high, the crew commented that all checklist procedures were carried out, the approach was briefed, and all relevant radio broadcasts were made.
The circumstances at the time generated a sense of urgency, given that the extent of cloud cover appeared to be growing rapidly. Furthermore, the crew were keen to descend to the MDA expeditiously in an attempt to establish and maintain visual contact with the runway environment, beneath the intervening wisps of low cloud.
Although the captain remained confident that sufficient fuel was available to divert to Wiluna, suitability of the conditions at Wiluna had not been recently confirmed. An element of doubt about the continuing suitability of Wiluna left the captain feeling slightly uneasy about the circumstances, particularly after encountering unexpected low cloud at Leinster.
Management of the approach profile was probably compromised to some extent by the manner in which the approach was conducted in visual conditions, but with the intent of complying with an instrument procedure. The attention of the crew during the approach was probably substantially drawn to ongoing assessment of how to effectively contend with the low cloud ahead.
ATSB comment
Following a small number of safety occurrences where unforecast weather events have led to unforeseen diversions or holding, the ATSB commenced a research investigation (Reliability of aviation weather forecasts) to examine how often weather events are not forecast in enough time allow pilots to make appropriate decisions (carry additional fuel, make a timely diversion or delay departure). Although the research investigation will focus on weather data for major Australian airports, the results should help operators better understand how much reliance can be given to forecast weather at destination airports at the time of pre-flight planning. This research investigation is linked in part to ATSB investigation AO-2013-100 (Weather related operational event involving B737s VH-YIR and VH-VYK at Mildura Airport, Victoria on 18 June 2013). On that occasion, the two aircraft involved diverted from Adelaide, South Australia, to Mildura, Victoria, due to poor weather in Adelaide. Unforecast weather was encountered when the aircraft subsequently arrived at Mildura.
In another weather-related incident, the ATSB found that the onset of fog at Perth Airport at the estimated time of arrival of a flight, was not forecast until after the aircraft had passed the point when it had insufficient fuel remaining to divert to a suitable alternate aerodrome. Before that point, there had been no requirement for the aircraft to carry fuel to continue to a suitable alternate (see ATSB investigation AO-2012-073Weather-related operational event involving Boeing 717, VHNXO, Perth Airport, Western Australia on 01 June 2012). The safety message attached to that investigation report included ‘…pilots should be alert to the fact that the actual weather conditions can differ significantly from forecasts.’
Pilots are also encouraged to make an Air-Report (AIREP) as soon as possible after encountering meteorological conditions that they believe may affect the safety of other operations. AIREPs contribute to the timely distribution of significant weather information that may assist with the operational decision making of other flight crews. More information about AIREPs is available in the Airservices Australia Aeronautical Information Publication.
Safety message
This incident highlights the importance of lateral thinking during flight planning, particularly where operations to remote areas are planned, and when an alternate aerodrome is close to the planned destination. In this case, the captain assessed the broader weather picture, and added fuel above the minimum requirements on the basis of that assessment. That additional fuel ultimately provided the crew with a safe option, despite encountering unexpected conditions that prevented a landing at the planned alternate aerodrome.
The circumstances leading to the EGPWS warning provide a reminder of the complications that can arise while endeavouring to follow an instrument procedure in visual conditions, particularly where significant attention is focussed on marginal conditions ahead that appear likely to affect the outcome of the approach. The circumstances can be further complicated when surrounded by a sense of urgency, and doubt about the suitability of other diversion options.
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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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 8 June 2014, a Aeromoragon M-1 aircraft, Spanish registration EC-EI3, departed La Morgal Aerodrome, Asturias, Spain for a private flight in the region. While returning to the aerodrome, the aircraft engine sustained an in-flight failure, requiring the pilot to conduct an emergency landing in an open field. During the landing sequence the aircraft struck a tree, damaging the left wing, tail and fuselage. There were no injuries to the pilot and passenger that were on board.
As the accident occurred in Spain, the Comisión de Investigación de Accidentes e Incidentes de Aviación Civil (CIAIAC) is responsible for investigating this accident. As part of its investigation, the CIAIAC notified the Australian Transport Safety Bureau (ATSB) as the State of Manufacture of the engine. The aircraft was fitted with a Jabiru 2200 engine.
In accordance with clause 5.18 of Annex 13 to the Convention on International Civil Aviation, the ATSB appointed an accredited representative to liaise with the CIAIAC and Jabiru, and initiated an investigation under the Australian Transport Safety Investigation Act 2003.
The ATSB has concluded its support of this investigation. On 2 February 2017 the CIAIAC released the final investigation report into this occurrence and it is available at www.fomento.gob.es.
Any enquiries regarding the investigation and report should, in the first instance, be directed to:
On the evening of 23 June 2015, a home-built Jabiru J430 aircraft, registered F-PFAJ, was being flown on a transfer flight from Aachen, Germany to an airfield near the town of Oehna, France. The aircraft was being operated at night in instrument meteorological conditions. Thunderstorms and heavy precipitation were recorded along the flight path. At around 2200 that evening, local residents identified aircraft wreckage and debris within and surrounding the township of Mühlenberg, Germany. The aircraft had sustained an in-flight break up. Both occupants, a pilot and passenger, were fatally injured.
The German Federal Bureau of Aircraft Accident Investigation (BFU) was primarily responsible for investigating this accident. As part of its investigation, the BFU notified the ATSB as the State of Manufacture of the aircraft. In accordance with clause 5.18 of Annex 13 to the Convention on International Civil Aviation, the ATSB appointed an accredited representative to liaise with the BFU and the Australian aircraft manufacturer. In order to facilitate that liaison, an investigation under the Transport Safety Investigation Act 2003 was initiated.
The BFU completed their investigation and concluded that:
The accident was caused by the pilot flying into instrument meteorological conditions which resulted in an uncontrolled flight attitude, which in turn resulted in structural failure due to overstress.
Contributory factors were the lack of qualification of the pilot to control an aircraft in IMC and the aircraft equipment geared to visual flight rules. In addition, both occupants were under mental pressure to reach the aerodrome of destination on direct course.
Since the trim tabs were not installed on the elevator, it was possible to perform a flare with higher load factors due to a greater deflection of the elevator.
The final report, BFU 15-0764-CX, is available on the BFU website at www.bfu-web.de/reports.
Any enquires relating to the investigation should be directed to the BFU at: www.bfu-web.de.
After departing Hamilton Island, A320 aircraft VH-HYJ tracked via Mackay to Emerald, and then airway route W82 towards Roma at flight level (FL) 370. Boeing 767 VH-OGE departed Brisbane and tracked via Taroom and airway route A464 towards Longreach, also at FL370. The aircraft were being controlled by the Brisbane Sector 5 Procedural Controller. The controller was undergoing a routine periodic performance check by a check controller. Sector 5 airspace covers the greater portion of southern Queensland and extends to 150 nm west of Mount Isa. During the 30 minutes leading up to the occurrence, the Sector 5 controller had been engaged in coordination with Darwin, Townsville, Brisbane Sectors 2 and 3, Adelaide, Alice Springs, and Mount Isa. During that time, he had 12 Regular Public Transport (RPT) jet aircraft which required separation, coordination, and frequency change instructions. Sector 5 airspace has 6 discrete VHF frequencies, which allows continuous VHF communication to be maintained within the Sector. Frequency change points do not coincide with reporting points thus increasing controller workload, particularly when instructions have to be repeated, or communication with aircraft is temporarily lost. For traffic management purposes, each aircraft is assigned a Flight Progress Strip for each position reporting point. The controller had approximately 60 strips on the flight progress console which required surveillance during the period. When it became apparent that there was a potential confliction between VH-OGE and VH-HYJ, the controller offered VH-HYJ FL390 for separation but this was not acceptable to the flight crew. The controller then offered VH-OGE FL390 for separation but this was also unacceptable. The alternative was then to descend VH-HYJ to FL350 but this could not be accomplished until this aircraft had reported sighting and passing a Boeing 737, VH-TAW, which was on the same track, but heading in the opposite direction at FL350. A passing time was calculated, but the aircraft did not sight and pass each other until two minutes later than expected. When the sighting and passing was reported, the controller immediately instructed VH-HYJ to descend to FL350, but it then became apparent that the requisite vertical separation standard (two thousand feet) would not be achieved before VH-HYJ had entered the area of conflict with VH-OGE. The area of conflict is a defined area based on navigation tolerances, within which there can only be one aircraft, unless the prescribed non-lateral separation standard exists. It was determined by reference to a diagram which showed distances from Taroom and Longreach on the airway route A464, and Emerald and Roma on the airway route W82. The aircraft were estimated to be no closer to each other than 30 nm, whilst at the same flight level. The investigation revealed that the incident occurred during a period of extremely high workload. There were no personal or physiological circumstances or conditions that may have contributed to the development of the incident. The traffic was displayed in an efficient manner, however, the ability of the controller to appreciate the potential conflict at an early stage was reduced due to the high workload. The problem was recognised by the check controller and he brought it to the attention of the controller, who did not immediately respond, as his attention was on other tasks. When the potential conflict was recognised, the controller's options became extremely limited, and this resulted in an infringement of the separation standard. To reduce the possibility of a recurrence of this nature, the Civil Aviation Authority has placed an additional controller at the Sector 5 position, to coordinate traffic during identified periods of high workload."
At 1025 hours Eastern Summer Time on 14 February 1991, Gulfstream Aerospace AC 681 aircraft VH-NYG was entering the downwind leg of the circuit for a landing on runway 30 at Tamworth, New South Wales, when the pilot requested a clearance to land on a cross-runway, runway 18. When the aircraft was about 300 ft above the threshold of runway 18 the pilot advised that he was going to conduct a left orbit. During the orbit, a high rate of descent developed. The aircraft crashed in a wings-level attitude 350 m short of the threshold of runway 18. The aircraft was destroyed by impact forces and the pilot its sole occupant was killed.
Findings
1. The pilot was medically fit correctly licensed and qualified to undertake the flight.
2. Meteorological conditions and sun angle at the time of the accident were not significant.
3. The fuel planning figure given by the endorsing pilot was incorrect.
4. Neither the company nor the pilot established the correct fuel usage rate for the aircraft.
5. The engines' fuel flow indications were incorrect.
6. The fuel quantity gauge indications may have been erroneous.
7. The 'fuel level low' warning system was probably not functional.
8. The aircraft was not loaded with sufficient fuel to complete the flight.
9. Both engines failed due to fuel exhaustion.
10. The pilot probably did not realise that the fuel was exhausted.
11. The initial impact with the ground was not survivable.
Recommendations:
Early in the investigation the Civil Aviation Authority was advised of certain apparent operational irregularities. Consequently, no new recommendations arising from the investigation were considered necessary.
The Air Tractor, VH-OMC, and an Ayres SR2 aircraft were operating in company. The spraying operation had been completed, and both aircraft were loaded with water in order to flush the hoppers and spray equipment during the return flight to St George. After departing the strip, the aircraft deposited the water onto a disused field and then headed for St George, flying at approximately 50 feet above ground level and about 30 metres apart. The pilot of the Ayres S2R saw VH-OMC, which was on his left, suddenly pull up into a climb. He then lost the aircraft from view but moments later saw a cloud of dust rising where it had impacted. Ground witnesses saw both aircraft flying level, approximately line abreast, when the Air Tractor suddenly pulled up steeply, as if to make a turning manoeuvre at the end of a spray run. However, at the top of the pull up the aircraft became inverted and fell to the ground. An inspection of the wreckage revealed no mechanical defects which might have contributed to the accident. The engine was operating at impact.
Significant Factors:
The factors relating to the development of this accident could not be determined.
The Boeing 737 (B737) had been cleared from Cowes direct to Launceston via the 320 radial of Launceston VOR and to leave flight level 330 (33 000 ft) descending initially to 7000 ft before receiving further descent clearance to 6000 ft. The Fokker F28 (F28) had departed Launceston runway 32, followed by a left turn to intercept the 314 radial of the VOR with an altitude restriction of 5000 ft. At about 16 nm from Launceston, the B737 reported at 6000 ft, inbound on the 320 VOR radial in visual flight conditions. The Launceston Aerodrome Controller (ADC) advised the B737 to expect further descent shortly and to track to enter the circuit on a right downwind leg for runway 32. The F28 had become airborne about 2 min earlier with an amended clearance to intercept the 314 radial outbound instead of the normal 325 radial as specified in the Launceston Standard Instrument Departure procedure. At 13 nm from Launceston, the B737 was cleared by the ADC to continue descent to 5000 ft. The pilot undergoing command training in the B737 unintentionally veered slightly right of the 320 inbound radial towards the F28 tracking on the 314 outbound radial. The F28 was about 9 nm from Launceston on the 314 radial, breaking through broken cloud tops at about 4200 ft, when the aircrew first sighted the B737. The F28 veered slightly left to increase separation from the B737. Readout of the Digital Flight Data Recordings from both aircraft indicated that at 9.5 nm from Launceston, the B737 and the F28 had passed with a horizontal separation of 0.7 nm (i.e. 1.3 km) without vertical separation when both aircraft were at approximately 5000 ft. There were two qualified air traffic controllers performing ADC functions at Launceston at the time of the incident. One officer was a current controller monitoring familiarisation of the second experienced officer who had recently returned from leave. The monitoring ADC had sighted the B737 at approximately 20 nm from Launceston and verified that it was inbound on the 320 radial. He also visually assessed that the F28 was tracking outbound on the 314 radial in accordance with instructions. The monitoring ADC then discontinued visual surveillance of the B737 and the F28 for a short time. He became occupied with surveillance of two other aircraft departing towards the NE to ensure that the sequence planned by the training ADC would ensure separation from the approaching B737. By this time, neither ADC was maintaining surveillance of the B737 or the F28. Neither sighted the B737 again until shortly after both aircraft had passed and the crews had exchanged comments on their proximity. The controllers then noticed that the B737 had unexpectedly veered slightly right of the 320 radial.
Significant Factors:
The following factors were considered relevant to the development of the incident
1. The use of visual separation standards may have been inappropriate at the time of application due to cloud and aircraft positions.
2. Vertical and lateral separation standards were replaced by visual separation standards without confirmation that the aircraft had safely passed.
3. Neither aircraft had been alerted of the proximity of the other. This incident was not the subject of an on-scene investigation.
The aircraft was engaged in glider towing operations. After a normal glider release at 3 300 ft, the tug aircraft was seen to enter a left descending turn at about 45 degrees angle of bank. At about 2 000 ft, the direction of turn rapidly reversed and the right wing was observed to have collapsed in the vicinity of the wing strut's attachment points. The rate of turn and rate of descent increased rapidly before the aircraft impacted the ground in a high-speed spiral. Examination revealed that the right wing of VH-SUT had failed at the rear spar inboard of the lift strut attachment point between rib numbers 8 and 9. The failure had commenced at a weathered compression shake area. There was no evidence that the aircraft had been used in aerobatic flight or had been subjected to excessive flight loads immediately prior to the failure. The aircraft was in a steady left, descending turn when the wing collapsed. VH SUT had suffered minor damage to both wings in an overturn accident in late 1987. As a result, the wings were subjected to inspections in accordance with Airworthiness Directive AD/CHA/23 which required inspection of the wing spars for compression failures. No spar damage was found. Shortly after this accident, another Bellanca Scout wing became available for examination, and a number of compression failures were found. The aircraft logbook indicated that the wing had previously sustained minor damage. A study of foreign accident reports and articles in aircraft magazines also indicated that what was often perceived as minor, superficial wing damage from a main landing gear collapse, overturn, or wind gust on the ground, could cause extensive internal damage to the wing spars. It was evident that compliance with AD/CHA/23 would not guarantee that all existing compression shakes would be found.
Significant Factors:
The following factors were considered relevant to the development of the accident
1. Forces applied during a previous accident probably initiated a compression failure in the timber of the rear spar.
2. Maintenance inspections in accordance with Airworthiness Directive AD/CHA/23 did not detect the failure because the AD did not require the area of the failure to be inspected.
Recommendations:
The Bureau made a recommendation to the Civil Aviation Authority in the early stages of the investigation that Airworthiness Directive AD/CHA/23 should be revised to incorporate an inspection of the the whole spar. The Civil Aviation Authority issued an Airworthiness Advisory Circular article on 21 March 1991 and Amendment 1 to AD/CHA/23 on 16 May 1991.
The flight was scheduled as a Supplemental Airline (SAL) flight number 421S, but due to the unavailability of a SAL qualified pilot, the flight was rescheduled as a charter flight. Both passengers were booked on airline flights out of Brisbane, one of which was scheduled to depart at 0905. When the pilot and passengers walked out to the aircraft it was raining, and the passengers put their umbrellas and a brief case in the right wing locker. The pilot then closed the locker door before boarding the aircraft. The pilot transmitted a taxiing call to Brisbane Flight Service at 0801 local time. Seven minutes later, he reported lining up on runway 11 and requested an airways clearance. After the aircraft became airborne, witnesses saw it make a left turn and proceed downwind, close to the runway, at about 150 feet above ground level. The landing gear was down, and there was a heavy rain shower in progress at the time at the aerodrome. When the aircraft was abeam the downwind end of the runway, it was seen making a steeply banked turn to the left. As the turn progressed through south, the bank angle became steeper and was estimated by witnesses to be approximately 90 degrees. The aircraft then became inverted and descended into trees. A piece of cleaning rag, found later on the runway, was identified as having been in the left wing locker when the aircraft returned from the previous flight. The rag had apparently fallen from the wing locker after the aircraft became airborne. It could not be determined if the door was incorrectly secured before flight or if it came open of its own accord as the aircraft became airborne. However, it does appear that the pilot noticed the open door soon after take-off and was returning to land and fasten the door when the accident occurred. The resultant delay would have caused the aircraft to arrive in Brisbane late and could explain the pilot's apparent haste to land. Witnesses near the accident site said it was raining very heavily at the time of the accident. This could have caused the pilot to temporarily lose sight of the runway. The aircraft had passed through the extended runway centreline by approximately 200 metres, when the aircraft stalled and struck the trees. There were no mechanical defects found which may have contributed to the development of the accident.
Significant Factors:
The following factors were considered relevant to the development of the accident:
1. The left wing locker door was open in flight for reasons which could not be determined.
2. The pilot was making a close low level circuit and misjudged the turn onto final approach.
3. The pilot used excessive bank during the turn onto final approach and the aircraft stalled.
