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Boeing 767-219ER, ZK-NBC

Summary

Approximately six minutes after take-off from Brisbane, Australia on a scheduled passenger service to Auckland, New Zealand, the Boeing 767-219ER aircraft, registered ZK-NBC sustained an uncontained failure of the left (number-1) engine, necessitating a return to Brisbane.

During the return, the flight crew elected to conduct a prepared emergency landing, however communication misunderstandings between the flight crew and the cabin in-flight service director (ISD) resulted in some crew and passengers not being appropriately briefed. The flight crew's subsequent call for the 'brace' position at 500 ft thus came as a surprise to the unaware cabin crew, some of whom adopted the unprepared emergency landing procedures, calling "Emergency - grab your ankles" to the passengers.

Failure of the number-1 engine (a General Electric CF6-80A high-bypass turbofan engine) resulted from the fracture and liberation of a large segment from the first-stage high-pressure turbine disk. The disk failure initiated from a radial fatigue crack at the base of a turbine blade slot, one of three similar cracks that were found during the subsequent investigation. The loss of the disk segment, the resultant imbalance and rapid engine seizure produced extensive damage to the engine casing, accessory components and the engine pylon. The released disk segment impacted the leading edge flap panel immediately above the engine - damaging a 600mm length and resulting in the flight crew electing not to use the leading edge flaps for the return approach and landing at Brisbane. Because the engine pylon and leading edge flap damage sustained during the engine failure was likely to affect the structural strength of the engine pylon and the performance and flight characteristics of the aircraft, the event was classified as an accident, in accordance with the definition published by the International Civil Aviation Organization (ICAO) in Annex 13 to the Convention on International Civil Aviation.

ATSB laboratory examination found that the disk cracking had originated from the rear break-edge corner of the blade fir-tree slots; an area that had sustained heavy surface microstructural damage as a product of manufacturing and/or repair shot peening processes. While subsequent fatigue testing of other blade slots with similar surface damage did not conclusively identify a loss of fatigue life resulting from the peening processes, it is known that overly heavy or abusive shot peening can prove detrimental to fatigue performance.

As a result of the findings of the investigation, the engine manufacturer has implemented several changes to the manufacturing and repair shot peening processes, to avoid the surface damage found on the failed disk. Other safety action taken included revising the inspection requirements for the CF6-80A disks to include the more thorough examination of the slot bottom and rear break-edge areas, as required for the CF6-80C series engines. The US Federal Aviation Administration (FAA) and the Australian Civil Aviation Safety Authority (CASA) have subsequently mandated the revised requirements. The aircraft operator, as part of its own investigation into the occurrence, has developed a series of recommendations aimed at addressing the crew communication deficiencies experienced during the return to Brisbane after the engine failure.

• Severe mechanical and structural damage to the number-one (left) engine and nacelle.

• Associated distortion and structural damage to the engine pylon.

• Surface damage to the number-five leading edge slat above the engine.

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Occurrence summary

Investigation number 200205780
Occurrence date 08/12/2002
Location 30 km ESE Brisbane, Aero.
State Queensland
Report release date 24/09/2004
Report status Final
Investigation type Occurrence Investigation
Investigation status Completed
Mode of transport Aviation
Occurrence class Accident
Highest injury level None

Aircraft details

Manufacturer The Boeing Company
Model 767
Registration ZK-NBC
Serial number 23328
Sector Jet
Operation type Air Transport High Capacity
Departure point Brisbane, QLD
Destination Auckland, NEW ZEALAND
Damage Substantial

Abnormal engine indications involving Aerospatiale AS.332L, VH-BHY

Safety Action

Local Safety Action

The operator carried out an internal investigation using various techniques, among them the Maintenance Error Management System (MEMS), to attempt to identify any weaknesses in their system. The results of this safety task were forwarded in a report to the ATSB as part of the company's reporting culture. Although the operator's engineers believed they did not overlook correctly tightening the bolts and contested the findings as to why the Bendix shaft attachment bolts could have become loose, the operator nevertheless accomplished the MEMS audit and raised awareness in the engineering department on correct assembly procedures for this task.

This was achieved through issuing a Safety Alert to their engineering department highlighting the need for diligence when assembling Bendix drive shafts and emphasising a four step check list to prevent any future occurrence attributable to incorrect maintenance. A review of the company holdings of specialist equipment that might assist early identification of vibration sources was also undertaken as part of the internal safety management process.

Factual Information

An abnormal noise coming from the left engine of an Aerospatiale AS.332L Super Puma helicopter, registered VH-BHY, was reported by several operating crews over the course of successive charter flights. The noise and vibration was evident at approximately 26,000 rpm during acceleration and deceleration phases, and could be induced by rapid movement of the speed select lever.

Although the engine was operating within the manufacturer's vibration limit, maintenance personnel continued to investigate the cause of the vibration. It was discovered that the six attachment bolts at the engine end of the Bendix driveshaft had worn through approximately 50 percent of their thickness. There was evidence of fretting of the mating surfaces of the Bendix and engine coupling plates. The engine attachment plate for the Bendix also incurred severe elongation of the bolt holes. This condition, if left undetected, would have resulted in the loss of drive from the left engine to the main gearbox. Maintenance personnel could draw no conclusion as to how this damage had occurred. The operator had not seen this type of wear before on other Super Pumas either in Australia, or with its North Sea operation. The Bendix shaft had completed approximately 380 hours in service since installation.

Figure 1: Bolt wear through 50% thickness.

aair200205705_001.jpg

Figure 2: Engine drive adaptor elongated bolt holes

aair200205705_002.jpg

New Bendix attachment bolts, along with several of the damaged bolts were forwarded to the Australian Transport Safety Bureau (ATSB) for laboratory analysis. The examination found no evidence of material deficiencies or other anomalous features of the bolt construction that would have rendered the items susceptible to the type of damage observed. The ATSB concluded that the damage sustained by the Bendix attachment bolts supplied was consistent with the effects of inadequate bolt tightness. Breakaway torque tests conducted at the operator's facilities under ATSB supervision confirmed that the locking nuts had appropriate locking capability to retain torque applied to them.

The engine was shipped to the manufacturer in France for further testing. The tests were conducted under the supervision of the Bureau Enqutes Accidents (BEA) on behalf of the ATSB. The engine was instrumented and run in a test cell, which confirmed the vibration levels reported by the operator. The levels observed were close to the maximum values permitted for this engine type. A disassembly inspection revealed rub damage to the abradable seal of the free turbine front and rear labyrinths consistent with unusual movement of the free turbine bearing. The movement was probably induced by radial loads as a consequence of the lack of torque on the Bendix attachment bolts and nuts. The phonic wheel also exhibited rubbing damage to the circumferential teeth. The damage to the engine, observed by the manufacturer and the BEA, in their opinion was consistent with inadequate torque of the bolts and nuts which secured the Bendix coupling to the engine drive flange connection.

Interviews with the operator's engineering staff established that an oil seal was changed in the vicinity of the shaft attachment bolts approximately 46 flying hours prior to discovery of the bolt wear. The engineers stated that this maintenance activity did not require that the Bendix attachment bolts be disturbed to accomplish the task. The engineers were those that originally fitted the shaft to the helicopter. When queried about the shaft fitment, they could not recall any external factors that may have caused distraction from the task. The personnel were appropriately licensed and experienced on the helicopter type. The task was not classified as difficult or unusual and had been performed on numerous occasions by this engineering team.

The operator noted that between the time the Bendix shaft was fitted and the discovery of the defect, the aircraft had moved location from Karratha to Darwin and return. The aircraft had accumulated approximately 380 hours since the shaft was installed. Engineers suggested that the forward end of the shaft might have been disturbed for fault tracing of the excessive vibration while in Darwin. No maintenance records were found to indicate that the bolts had been disturbed and the Darwin engineers stated that, to their knowledge, the shaft was not disturbed during the vibration fault finding.

The investigation could not determine the factors relating to the loss of torque of the retention hardware.

Summary

An abnormal noise coming from the left engine of an Aerospatiale AS.332L Super Puma helicopter, registered VH-BHY, was reported by several operating crews over the course of successive charter flights. The noise and vibration was evident at approximately 26,000 rpm during acceleration and deceleration phases, and could be induced by rapid movement of the speed select lever.

Occurrence summary

Investigation number 200205705
Occurrence date 02/12/2002
Location Karratha, Aero.
State Western Australia
Report release date 07/06/2004
Report status Final
Investigation type Occurrence Investigation
Investigation status Completed
Mode of transport Aviation
Aviation occurrence category Abnormal engine indications
Occurrence class Incident
Highest injury level None

Aircraft details

Manufacturer Aerospatiale Industries
Model AS332
Registration VH-BHY
Serial number 2129
Sector Helicopter
Operation type Charter
Departure point Karratha, WA
Destination Oil Rigs on NW Shelf
Damage Nil

British Aerospace Plc BAe 146-100, VH-NJD

Safety Action

Local safety action

The operator has undertaken to raise awareness among flight crew about the risks of possible crew incapacitation from fumes and the importance of not delaying the donning of oxygen masks during emergency checklist actions. This notice should include reiteration of the primacy of any immediate recall emergency checklist actions over other operator documentation. This will be achieved by a re-write of the procedures detailed in the operator OM-2 operations manual.

The ATSB expressed concern to the operator about the lack of advice provided to medical staff as to what medical tests should be carried out on crew after possible exposure to fumes. The operator undertook to introduce a procedure to communicate a list of prescribed minimum tests, published by the airframe manufacturer in SIL 21/45, to medical practitioners whenever crewmembers require testing for fume exposure. This would ensure that the attending doctor would have the latest testing information available at the time of the test. It was agreed that the information should, as a minimum, cover the appropriate medical tests for such exposure as listed on Pages 10 and 11 of BAe SIL 21/45 Issue Number 1 dated January 2001 (or as amended).

With regard to the concern about appropriate use of the diluter type masks and portable oxygen bottles by cabin crew in heavy smoke or fumes situations, the operator has undertaken to issue a flight attendant safety memo (FASM). This FASM will raise awareness among cabin crew of the limitations of the portable oxygen bottle and diluter type masks when used in a fumes contaminated environment.

Analysis

The aircraft type has been the subject of recurring fume incidents throughout its operating life as commented on by the PIC. It has been subject to intense investigations by both operators and the manufacturer. These investigations have resulted in the promulgation of several service information letters, bulletins, airworthiness directives and NOTOP troubleshooting requirements.

Because of this history, the fume events may have become `routine' in the thinking of some operating crew and awareness of the possible risks may have diminished as a result. This familiarity was a concern to the manufacturer as evidenced by the wording in the AOM to the operator. Familiarity may have led the PIC to delay the donning of his oxygen mask. The imperative to ascertain the source of contamination as soon as practicable in accordance with the operator's NOTOP directive may have also influenced the PIC's decision making.

Although the PIC felt that there was no need for him to don his oxygen mask, this action was contrary to the operator's emergency procedures. The completion of the NOTOP diagnostic action should be accomplished after any emergency checklist actions. By choosing to remain exposed to potentially contaminated air, the PIC might have risked degradation of his faculties, which then may have reduced his ability to correctly determine if there was a flight hazard and respond appropriately. This increased exposure may also have long term or cumulative effects that are not yet understood.

If the emergency checklist had been performed first, both pilots should have donned oxygen masks and the subsequent occasional removal of an oxygen mask by one pilot for air sampling would have likely had minimal safety consequences. This is further reinforced by the fact that both pilots experienced some after-effects that required stand down from flight duties even though one, the copilot, had donned an oxygen mask early in the event.

The PIC's request to the FAs and their subsequent actions in opening the flight deck door were contrary to procedures. The smoke/fumes procedures in both cockpit and cabin are safety of flight defences designed to minimise the potential for flight crew incapacitation by isolating the flight deck from cabin hazards. Again the possible perception that fume events are a `routine' part of the environment in which the crews operate may have led both flight and cabin crew to believe that the action was appropriate under the circumstances.

The oxygen bottle used by the cabin crew was fitted with a diluter or therapeutic type mask. This design does not provide protection from smoke or fumes as most of the air mixture provided is ambient air. Under certain circumstances involving heavy contamination by fumes, the use of this type of mask might mislead the user into a false sense of protection and lead to the possibility of being overcome by the fumes. The limited protection afforded by this type of mask should be brought to the attention of cabin crew.

Summary

The crew carried out the take-off in the British Aerospace Plc BAe 146 (BAe 146) with number 4 engine air bleed selected on, and engine numbers 1, 2 and 3 and the auxiliary power unit air bleeds selected off in compliance with an item in the discrepancy log. Shortly after take-off, at approximately 700 ft above ground level, the copilot switched on the remaining engine air bleeds and both air conditioning packs. Shortly after selecting engine anti-ice on, the pilot in command (PIC) asked the copilot if he could smell fumes. The copilot agreed that he too had detected a smell. The engine anti-ice system was then switched off.

A short time after commencing the cabin service, a flight attendant (FA) called the flight deck and informed the PIC of fumes in the cabin and that they were particularly bad near the rear of the cabin where another FA had donned an oxygen mask. This mask was of the diluter type that supplies a mixture of the incoming oxygen with the ambient air that is then delivered to the user. The copilot then indicated to the PIC that `he felt he should go onto oxygen' and donned an oxygen mask, but the PIC did not feel he needed to perform the same action at that time.

The PIC later stated that he did not don his oxygen mask at this time, as he was considering if the fumes were oil related in accordance with a notice to pilots (NOTOP) from the operator. This NOTOP required the PIC to make a diagnosis as to the source of contamination `wherever it is safe and practicable to do so'. The PIC's findings were required by the operator to determine the level of response required to later rectify the problem and return the aircraft to service.

The PIC stated that the aircraft type had a history of fumes related problems and not donning his oxygen mask was a normal practice for himself and, he believed other aircrew employed by the operator. He said `most smells and odours were considered the normal environment of the day to day operation of the BAe 146' and he would have discontinued his NOTOP diagnostic action if he perceived a flight hazard issue and would have reverted to the emergency checklist action. He also stated that the copilot, being on oxygen, could confirm a successful isolation procedure by occasionally removing his mask and comparing pure air with the ambient air of the flight deck.

This was at variance with the emergency checklist for SMOKE/FUMES/FIRE IN COCKPIT/CABIN. This list takes priority over any other action. The first item on the checklist is `Oxgen masks and goggles...Flight crew don, check 100%'. The imperative in relation to fumes events was also highlighted in an all operator message (AOM) from the manufacturer, which states in part `pending the definition of any necessary corrective actions, oil leaks and cabin/flight deck smells must be regarded as a potential threat to flight safety and not just a nuisance'.

The copilot completed fault isolation checks that appeared to improve the air quality on the flight deck. The PIC then asked the FAs if they could come to the flight deck so that he could better assess the situation in the cabin. The FAs came forward in turn, opened the flight deck door and entered. This action was at variance with the operations manual actions for flight attendants in the event of smoke/fumes in the cabin. The manual stated that, in the event of smoke/fumes, the FAs were to inform the PIC via the intercom and were not to open the flight deck door.

In his original report, the PIC stated that `each time when they opened the flight deck door, we noticed that the odour intensified'. The FAs' cabin crew reports to the operator also stated that the odour and fumes were still evident in the passenger cabin during the remainder of the flight. The PIC described the odour to be unlike any odour previously encountered and then decided the safest option was to return to the departure airport.

The incident operating crew underwent medical examinations that evening as directed by the operator after the event. The PIC stated that the medical practitioner they visited told him she knew very little about the effects of odours on crew and was unaware of any specific blood testing requirements for such an event. Medical testing information printed by the aircraft manufacturer in Service Information Letter (SIL) 21/45 Issue Number 1, dated January 2001, details specific test requirements. The PIC stated that it was sometimes difficult to find a medical practitioner at short notice (especially late at night) who was familiar with the required testing procedures.

After advising the medical practitioner that he was unsure if he would be able to work the following day, the PIC was given a medical certificate excusing him from flight duties for the following 24 hours. Even though he donned his oxygen mask, the copilot was similarly affected and was also excused from flight duties for the same period as the PIC. The operator reported that the remaining crew did not exhibit any residual effects from the incident.

A maintenance investigation by the operator included compliance with the latest airworthiness directive and service bulletins. All engines and the auxiliary power unit were checked. The airconditioning regenerative ducting and the delivery ducting to the rear cabin were also dismantled and inspected. That investigation determined that the number-3 engine was the likely source of the fumes and the engine was changed. The aircraft was returned to service with subsequent operating crews reporting no further fumes problems.

Occurrence summary

Investigation number 200205307
Occurrence date 11/01/2002
Location Perth, Aero.
State Western Australia
Report release date 20/08/2003
Report status Final
Investigation type Occurrence Investigation
Investigation status Completed
Mode of transport Aviation
Aviation occurrence category Fumes
Occurrence class Incident
Highest injury level Minor

Aircraft details

Manufacturer British Aerospace
Model BAe 146
Registration VH-NJD
Serial number E1160
Sector Jet
Operation type Air Transport High Capacity
Departure point Perth, WA
Destination Paraburdoo, WA
Damage Nil

Cessna 207, VH-EHL

Summary

The Cessna 207 aircraft (C207) was engaged on a sight-seeing flight from Cradle Mountain to Lake St. Clair and return. On board were the pilot and 4 passengers. The flight departed Cradle Mountain at approximately 1310 ESuT and tracked direct to Lake St Clair at 7000 ft due to turbulence. The aircraft then returned to Cradle Mountain.

At approximately 1404, as the aircraft was approaching the airfield, the pilot configured the aircraft for a straight in approach to strip 02. The pilot had selected two stages of flap, and had reduced power to approximately 19 inches of manifold pressure. He reported that at approximately half a mile from the airfield the engine stopped without any prior warning. After completing trouble checks, the pilot became aware that the aircraft would not reach the airfield. He then manoeuvred the aircraft towards an open area on his right while broadcasting a MAYDAY call. Melbourne air traffic control acknowledged this call. The pilot then completed additional trouble checks and changed the fuel tank selection, but the engine failed to respond.

The aircraft touched down heavily on the main wheels and slid approximately 40 metres before coming to a stop. During the touchdown and subsequent ground slide, the nose wheel detached from the aircraft, the propeller was damaged and the right wing was partially separated from the airframe. After the aircraft stopped the pilot checked the passengers and discovered that two of them had suffered serious injuries. As fuel was leaking from the damaged right wing, the pilot and uninjured passenger assisted the injured passengers from the aircraft. The pilot was then able to make his way to the airstrip to raise the alarm. The Australian Transport Safety Bureau did not attend the site but conducted the investigation relying upon information provided by the pilot, the operator, and the Bureau of Meteorology.

The pilot reported that he had completed a daily inspection of the aircraft earlier in the morning. That inspection included assessing the fuel quantity on board the aircraft and completing a fuel drain and water check. Both of these checks did not reveal any problem with the fuel. The pilot estimated that there was approximately 185 litres of fuel on board the aircraft, 90 litres in the right tank and 95 litres in the left tank. The aircraft had last been refuelled the day previously from drum stock. The aircraft had completed two flights since that refuelling with no problems being reported. The engineers that recovered the aircraft reported that there was approximately 30 litres of fuel in the left tank and approximately 100 litres of fuel in the right tank.

The C207 aircraft has a fuel selector in the cockpit that allows the pilot to supply fuel to the engine from either the right tank or the left tank, but not from both tanks simultaneously. The pilot reported that he conducted the flight with the fuel selector switched to the left tank. He also reported that he did not move the selector during the flight and only moved it to the right tank as part of his trouble checks when the engine failed.

The pilot reported that he did not complete flight or fuel plans for the flight, but operated on previous knowledge from other flights. A post occurrence analysis of the weather indicated that the winds at 7000 feet were as forecast. Post flight analysis of the flight revealed that the aircraft would have required 57 litres of fuel to complete the flight, which included allowances for taxi and climb.

The engine was sent by the owner to an engine overhaul facility for testing. The ATSB did not attend the testing of the engine. The engine was fitted to the test cell in the condition as removed from the aircraft. The engine was started and test run in accordance with the engine manufacturer's overhaul manual. The engine ran normally and all temperature and pressure limits were within normal ranges.

The investigation was unable to determine why the engine failed to operate normally in the latter stages of the flight.

Occurrence summary

Investigation number 200205223
Occurrence date 07/11/2002
Location 4 km S Cradle Mountain (Valley)
State Tasmania
Report release date 22/07/2003
Report status Final
Investigation type Occurrence Investigation
Investigation status Completed
Mode of transport Aviation
Aviation occurrence category Forced/precautionary landing
Occurrence class Accident
Highest injury level Serious

Aircraft details

Manufacturer Cessna Aircraft Company
Model 207
Registration VH-EHL
Serial number 20700141
Sector Piston
Operation type Charter
Departure point Cradle Mountain (ALA), TAS
Destination Cradle Mountain (ALA), TAS
Damage Substantial

Cessna 441, VH-VEM

Summary

Shortly after take-off from Gawler SA, the crew of the Cessna 441 Conquest heard a loud air noise. The pilot in command recognised this as the emergency pressurisation system operating. The pressurisation selector switch was checked and found to be in the BOTH position. Selection was made between LEFT and RIGHT, however the air noise continued and there was no activation of the emergency pressurisation warning light. At this point the crew elected not to proceed to Essendon but to divert to Adelaide, where engineering staff were available.

Subsequently, a passenger noticed that the air by his feet was getting hot and advised the crew. Light grey smoke was noticed by the co-pilot in the mid cabin area. The crew conducted the emergency checklist for smoke removal and donned their oxygen masks as a precaution. The storm window was opened to assist with removal of smoke from the aircraft as it was stinging the co-pilot's eyes.

The pilot declared a PAN, and, at this point, the aircraft was 2 km abeam Parafield. The crew elected to divert to Parafield, the nearest airfield where emergency services were available. An uneventful landing was carried out and no injuries were reported.

An engineering examination of the aircraft found that the activation of the emergency pressurisation system was initiated by a faulty emergency pressurisation valve. It was also found that, in the process of fitting new side wall trim carpet to the aircraft, the edge of the carpet had not been trimmed around the rear conditioned air duct. This duct supplies air for the emergency pressurisation system and the faulty emergency pressurisation valve allowed hot air to flow unmetered into the cabin. The carpet covering the duct had been exposed to excessive heat, which led to the fumes and smoke in the cabin.

The faulty emergency pressurisation valve was replaced, the carpet trimmed, and the aircraft was returned to service.

Occurrence summary

Investigation number 200205216
Occurrence date 06/11/2002
Location Parafield, Aero.
State South Australia
Report release date 26/08/2003
Report status Final
Investigation type Occurrence Investigation
Investigation status Completed
Mode of transport Aviation
Aviation occurrence category Air/pressurisation
Occurrence class Incident
Highest injury level None

Aircraft details

Manufacturer Cessna Aircraft Company
Model 441
Registration VH-VEM
Serial number 4410174
Sector Turboprop
Operation type Charter
Departure point Gawler, SA
Destination Essendon, VIC
Damage Nil

Boeing 737-476, VH-TJG

Safety Action

As a result of this occurrence, the following safety actions were initiated:

The operator of Canberra International Airport requested Airservices Australia to include a caution note in Canberra aerodrome information contained in the ERSA, as follows:

`During strong westerly winds down stream of buildings, severe turbulence may be experienced in the touch down area while landing Runway 35.'

The operator also requested Airservices Australia to issue a Notice to Airmen (NOTAM) to reflect that cautionary advice until the ERSA was amended, and to give consideration to making:

`…necessary caution announcements on the ATIS during similar strong wind conditions.'

Airservices Australia issued a local instruction to air traffic controllers at Canberra Tower. The instruction contained information that when the crosswind component (including gusts) from the west equals or exceeds 12 kts and runway 35 or 17 is nominated, the following shall be included on the ATIS:

`Expect turbulence over runway south of runway intersection.'

The instruction included information that controllers were to make a directed broadcast to aircraft operating on runway 35, or departing runway 17, when this crosswind condition exists and runway 35 or 17 were not nominated on the ATIS.

Airservices reported that it did not consider the issue of a NOTAM providing cautionary advice of turbulence was warranted, as directed broadcasts would provide pilots with information of the meteorological phenomenon.

Airservices Australia also reported that it would conduct a survey of the turbulence phenomenon until 1 July 2003 to determine the extent of the condition, including:

a. occasions when the westerly crosswind component, including gusts, equals or exceeds 12 kts,

b. pilot reports of turbulence / shear at touch down or take-off, including aircraft type,

c. pilot comments, and

d. pilot reports of turbulence when the crosswind is less than 12 kts.

Analysis

At the time of the occurrence, the wind direction and speed at Canberra aerodrome was 280 degrees T at 18 kts, with gusts exceeding 20 kts at times. The wind direction was therefore 80 degrees removed from the runway direction, providing a left crosswind of about 18 knots.

It is probable that the prevailing wind conditions at the time of the occurrence resulted in turbulent downwind wake eddies from the hangar located adjacent to, and to the west of, the touchdown zone of runway 35.

The downwind convergence of those turbulent wake eddies was probably in the vicinity of the touchdown zone of runway 35, and was likely to have been the source of the turbulence encountered during the landing flare.

Summary

At 1718 ESuT On 5 November 2002, VH-TJG, a Boeing 737-476 aircraft, encountered turbulence 1718 ESuT during the landing flare on runway 35 at Canberra International Airport. The aircraft was operating a scheduled fare-paying passenger service from Melbourne, Victoria to Canberra, ACT. The pilot in command was the handling pilot for the flight.

At 1700, the wind direction and speed at Canberra was 280 degrees T at 18 kts, gusting to 23 kts. At 1730, it was 280 degrees T at 18 kts, gusting to 26 kts. Runway 35 was aligned on magnetic heading 348 degrees, which was equivalent to 360 degrees T.

The automatic terminal information service (ATIS) at Canberra airport provided information on the prevailing weather conditions. At the time of the occurrence, information "Sierra" was current. It included information that runway 35 was in use, and that the wind direction and speed was 270 degrees M, with a minimum speed of 15 kts and maximum speed of 25 kts.

The aircraft was equipped with a solid-state digital flight data recorder (SSFDR). The flight data plots revealed that the pilot in command applied left control wheel to achieve a left wing low attitude of about 3 degrees as the aircraft descended through a radio altitude of about 60 ft. At about 6 ft radio altitude, the aircraft suddenly rolled left to a left wing low attitude of about 6 degrees, and the pilot in command rapidly applied right control wheel input to arrest the roll to the left. The aircraft landed about one second later in a slightly right wing low attitude.

The landing was completed without further incident, and there were no reported injuries to any of the 34 occupants of the aircraft.

The pilot in command subsequently reported that the turbulence encountered during the landing flare appeared to have resulted from a hangar located adjacent to, and to the west of, the touchdown zone of runway 35.

Construction of the hangar was completed in April 2002. The airside (eastern) face of the hangar was located 283.5 metres from the centreline of runway 35, and the roof height on the airside face of the hangar was 21.7 metres.

Turbulent wake eddies may be generated downwind of obstacles by wind flowing over and around them. The turbulent effects will depend on the size and location of an obstacle or group of obstacles, such as a cluster of buildings, as well as the direction and speed of the wind. If obstacles are located close to runways, turbulent wake eddies from those obstacles may have the potential to affect safety of flight if they result in aircraft experiencing difficulties during takeoff or landing.

The International Civil Aviation Organization (ICAO) has published standards and recommended practices that relate to aircraft, personnel, airways and auxiliary services. Those standards and recommended practices are contained in various Annexes to the Convention on International Civil Aviation, which was signed at Chicago on 7 December 1944 (the Chicago Convention). Australia is a contracting State to the convention. It is obliged under Article 37 of the convention to conform to standards and to endeavour to conform to recommended practices unless a difference has been filed with ICAO.

Annex 11 contained the standards and recommended practices that relate to the provision of air traffic services to the aviation sector. Paragraph 4.3.7 of Annex 11 detailed the information to be included in ATIS messages, and paragraph 4.3.7 k) required that messages contain:

`…other essential operational information.'

Paragraph 4.3.7 s) required ATIS messages to contain:

`…any available information on significant meteorological phenomena in the approach, take-off and climb-out areas including wind shear, and information on recent weather of operational significance.'

ATIS "Sierra" contained no information regarding the likelihood of turbulence in the touchdown zone of runway 35 at the time of the occurrence.

Canberra International Airport is a licensed aerodrome, and particulars about the aerodrome are required to be published in the Aeronautical Information Publication (AIP) Enroute Supplement Australia (ERSA).

The Civil Aviation Safety Authority (CASA) publishes Civil Aviation Advisory Publications (CAAPs) which provide guidance on the preferred method for complying with the Civil Aviation Regulations. CAAP 89O-1 (2), issued in November 2000, related to publishing aerodrome information and reporting changes to that information. That information included any event that affected the safety of aircraft using the aerodrome.

At the time of the occurrence, both the ERSA and the location briefing material for Canberra aerodrome contained no information to caution pilots of the likelihood of turbulence from the hangar located adjacent to, and to the west of, the touchdown zone of runway 35.

There have been two similar events of building-induced turbulence in the UK. One resulted in a B747 leaving the runway at London Heathrow airport, and was described in the UK Air Accident Investigation Branch (AAIB) Bulletin No. 5/2002. The other involved an A300 that sustained a podstrike at London Gatwick airport, and was described in AAIB Bulletin No. 6/2002.

The National Transportation Safety Board (NTSB) of the USA has had no reported occurrences of building-induced turbulence, nor has the NTSB identified that condition as a safety concern.

There are presently no building codes or standards in Australia that address the phenomena of building-induced turbulence with respect to proposed buildings to be located on or adjacent to aerodromes.

Occurrence summary

Investigation number 200205179
Occurrence date 05/11/2002
Location Canberra, Aero.
State Australian Capital Territory
Report release date 13/03/2003
Report status Final
Investigation type Occurrence Investigation
Investigation status Completed
Mode of transport Aviation
Aviation occurrence category Turbulence/windshear/microburst
Occurrence class Incident
Highest injury level None

Aircraft details

Manufacturer The Boeing Company
Model 737
Registration VH-TJG
Serial number 24432
Sector Jet
Operation type Air Transport High Capacity
Departure point Melbourne, VIC
Destination Canberra, ACT
Damage Nil

British Aerospace Plc BAe 146-300, VH-NJL

Safety Action

Issues associated with improving cabin air quality are the subject of ongoing efforts by the aircraft manufacturer, engine manufacturer, aircraft operators and some aviation regulatory authorities including the Australian Civil Aviation Safety Authority.

The Civil Aviation Safety Authority issued an airworthiness directive on 28 November 2002 (AD/BAe 146/102) requiring operators of BAe 146 type aircraft to action requirements of a manufacturer's Inspection Service Bulletin (ISB) 21-156. This related to the recurrent inspection of air conditioning ducts for traces of possible contamination and inspection of the ducts following a cabin air quality event.

The aircraft operator has also commenced replacing the noise-attenuating material that lines the air conditioning ducts across their entire BAe 146 fleet. This action exceeded the manufacturer's requirements outlined in its ISB 21-156.

The engine manufacturer is developing a redesigned bearing seal to improve the component's reliability and consequently reduce the frequency of incidents where cabin air is contaminated by engine lubricating oil.

Analysis

The investigation considered that the intermittent deterioration in cabin air quality was consistent with other similar occurrences during which the cabin air was contaminated by engine or APU lubricating oil. Due to the intermittent nature of contamination the source of the fumes was difficult to positively identify.

It was not possible to identify the substance(s) that had apparently contaminated the crew's drinking water while it had been left standing in the cups. However, the investigation could not discount the possibility that the drinking water had been contaminated by water-soluble compounds from cabin air contaminated by engine lubricating oil.

Summary

The co-pilot of the BAe146-300 reported that he noticed both cockpit side windows were open as he entered the flight deck to commence his pre-flight preparations and almost immediately detected the presence of fumes. He stated that these fumes had a distinctive odour that he recognised as being consistent with the contamination of the cabin air supply by lubricating oil from the aircraft's engines. This typically occurs when a faulty bearing seal allows lubricating oil to escape and contaminates one of the sources of cabin air for the aircraft.

The auxiliary power unit (APU) was operating and air conditioning Pack 1 and 2 were supplying air to the flight deck and passenger cabin. As Pack 1 supplies most of the air to the flight deck and because fumes were not apparent in the passenger cabin, the co-pilot immediately suspected that the contamination was associated with Pack 1. He de-selected Pack 1 and noticed an immediate improvement to the quality of the air.

The co-pilot briefed the pilot in command of these observations when he arrived on the flight deck. The crew used engine bleed air to provide cabin air conditioning as the aircraft taxied for take-off and Pack 1 remained de-selected. This was on the basis of the tailwind conditions encountered while taxiing, to reduce the possibility of ingesting fumes from the APU's exhaust into the aircraft cabin and the co-pilot's observations of air quality from Pack 1. The take-off was performed with all air conditioning packs selected off and number 4 engine supplying bleed air for pressurisation control of the aircraft cabin.

The co-pilot was the handling pilot for the sector from Perth to Karratha. After take-off, the crew selected engine bleed air sources from all engines and Pack 1 and 2 were used to provide air conditioning to the passenger cabin and flight deck. No fumes were evident in either the passenger cabin or the flight deck and the flight proceeded normally.

About 10 minutes prior to the top of descent, the co-pilot recalled starting to experience symptoms of a headache. He was able to continue his duties as handling pilot and completed the descent to the Karratha circuit area. The aircraft was on final approach to land, when strong oil-type fumes were again detected on the flight deck. As the aircraft cabin had already stabilised at sea-level atmospheric pressure and the source of fumes appeared to be either the air conditioning packs or one of the engine bleed air supplies, all air conditioning packs and all sources of engine bleed air were selected off. The intensity of the fumes quickly dissipated and the co-pilot completed the landing. Fumes were not detected in the passenger cabin by any of the flight attendants. The co-pilot reported that supplemental oxygen was not used on this occasion due to the critical phase of flight (short final approach to land) and the prompt action taken to isolate the source of fumes.

During the taxi to the passenger terminal, the co-pilot became aware that he was experiencing symptoms of an unusually strong headache, nausea and irritated eyes, nose and throat. His symptoms quickly improved as he conducted the external turnaround duties and he felt capable of performing his duties on the return sector as pilot not flying.

The pilot in command was satisfied that the source of fumes experienced on short final was associated with contamination of the cabin air supply by engine lubricating oil. The return flight was conducted without using APU air and with Pack 1 de-selected to minimise the possible recurrence of fume contamination. The flight was completed without incident.

Subsequent to the incident, the co-pilot recalled that during the outbound sector his bottled drinking water, which had been poured and left standing in his cup, had acquired a rank swampy, slightly metallic taste. The pilot in command was also reported to have made a similar comment about the taste of his drinking water. The cups were resting in the flight deck cup holders adjacent to the air outlet vents. This was noticed prior to the co-pilot reporting symptoms of a headache and fresh cups of water from the bottle tasted normal with no apparent sign of contamination. The ATSB were not able to test the water for contaminants as it had been discarded following the flight.

Following entry of the fume report in the aircraft's defect log, company engineering personnel applied the requirements of Airworthiness Directive AD BAe 146/86, issued 30 March 2001 that required inspection of various components associated with the aircraft's cabin air supply. This inspection revealed no apparent defects or source of contamination to the cabin air.

The operator received subsequent Operating Crew Reports associated with poor cabin air quality on 23 and 26 October 2002. The aircraft commenced a period of heavy maintenance on 28 October 2002. During this maintenance the APU was removed from the aircraft, cleaned, inspected (with nil defects found) and refitted. Air conditioning Pack 1 was also cleaned. The operator received subsequent reports of flight deck odours with respect to this aircraft on 5 and 8 December 2002 and the requirements of the Airworthiness Directive were again applied. On this occasion the inspections revealed slight leakage of engine lubricating oil from a bearing seal on the number 4 engine.

Occurrence summary

Investigation number 200204912
Occurrence date 20/10/2002
Location 6 km E Karratha, Aero.
State Western Australia
Report release date 20/08/2003
Report status Final
Investigation type Occurrence Investigation
Investigation status Completed
Mode of transport Aviation
Aviation occurrence category Fumes
Occurrence class Incident
Highest injury level None

Aircraft details

Manufacturer British Aerospace
Model BAe 146
Registration VH-NJL
Serial number E3213
Sector Jet
Operation type Air Transport High Capacity
Departure point Perth, WA
Destination Karratha, WA
Damage Nil

de Havilland Canada DHC-2 MK 1, VH-BVA

Safety Action

Local Safety Action

Civil Aviation Safety Authority

On 1 December 2002, the Civil Aviation Safety Authority revised the chief pilot's instrument of approval, specifying a condition that required the employment of a full-time senior float pilot.

On 20 August 2003, CASA provided the following information with respect to guidelines for aeroplane landing areas: 'As there are several levels of jurisdiction over waterways, CASA has raised with State Governments, through the Commonwealth/States/Territories Aviation Working Group, the question of whether there should be a joint review of the existing arrangements.'

Operator

In a letter to the Australian Transport Safety Bureau dated 11 June 2003, the operator advised that it had amended the company operations manual to reflect the appointment of a senior float pilot and revised the floatplane operations section of the operations manual. The operations manual stipulated that the senior float pilot was responsible to the chief pilot for the overall conduct of company floatplane operations.

The operator advised that it had appointed a new chief pilot.

An experienced floatplane pilot provided a report to the operator regarding company floatplane operations. Recommendations from that report included:

  1. additional theoretical and practical training and checking for company floatplane pilots;
  2. development of a company-specific pilot training guide; and,
  3. review and amendment as required of the company floatplane authorised landing area guide.

The floatplane pilot who wrote the report for the company has been retained to implement the changes recommended.

The company also advised that it intended to upgrade the facilities at its floatplane base to allow pilots improved access to weather, flight planning and operational reference information.

The company advised that it planned to implement a fatigue management system for pilots, including modifying the daily work schedule to allow adequate rest periods.

Factual Information

History of the flight

The pilot of the de Havilland Beaver floatplane registered VH-BVA was conducting a charter positioning flight from Hamilton Island Marina to Chance Bay, Whitsunday Island. He had landed at Chance Bay seven times in the previous two days. Weather conditions in the area were good. At 1700 Eastern Standard Time the Hamilton Island automatic weather station recorded a 7 - 10 knot wind from the northwest. Witnesses in Chance Bay said that the surface wind in the bay was 2 - 5 knots. The water surface in Chance Bay was smooth, but not glassy.

The pilot said that he commenced a straight-in approach to Chance Bay but elected to go around due to the increased number of vessels moored in the bay since the previous flight. He flew a left circuit at 500 feet and assessed that the area for landing was adequate. He said that on final approach, the flight path was higher than he would have preferred. His intention was to touchdown before passing abeam the vessels. He recalled that the floatplane speed shortly before touchdown was about 80 knots, rather than the target speed of 70 knots. He said that his response at this time was consistent with flying a landplane in that he reduced the back pressure on the control column and allowed the floatplane to contact the water at a lower nose attitude, and at a higher speed, than was ideal. Upon touchdown, the floatplane yawed sharply left 50 - 60 degrees and headed directly towards the anchored ketch 'Seark', about 300 m away. The pilot said that the water rudders (at the rear of each float) were retracted, so all the yaw control he had available was via the conventional aerodynamic rudder. As the aircraft yawed, it felt as though the rudder was stuck at full left deflection, but he thought that this was due to hydrodynamic drag. When the floatplane was an estimated 100 m from the 'Seark', it swung right so that it was heading slightly to the east side of the 'Seark'. However, the outer portion of the floatplane's left wing subsequently collided with the rear mast of the 'Seark'.

A video recording of the event showed that the floatplane touched down with a lower nose attitude than was ideal. It also showed that the left float touched the water first. The sharp left yaw followed immediately. The aircraft became airborne momentarily, shortly after initial touchdown.

The left wing of the floatplane and the rear mast of the ketch were substantially damaged. There were no injuries to the pilot or the three occupants of the ketch.

Landing area

Witnesses estimated that landing floatplanes (including this accident floatplane prior to touchdown), were passing about 50 m abeam the anchored yachts.

Civil Aviation Advisory Publication (CAAP) 92-1(1) 'Guidelines for aeroplane landing areas' stated that "a minimum width water channel of 60 m ... is recommended" for single-engine and centreline thrust floatplanes not exceeding 2,000 kg maximum take-off weight (MTOW). There were no diagrams or other guidance material provided for floatplanes greater than 2,000 kg MTOW or for multi-engine floatplanes. The MTOW for the accident floatplane was 2,313 kg. The Transport Operations (Marine Safety) Regulations (Queensland) 1995 s95 (1)(a)(ii) required that vessels operating at speeds greater than 6 knots must not approach within 30 m of a moored vessel.

Float alignment

Another company floatplane pilot reported that the aircraft required greater than normal right rudder input to maintain a constant heading during flight. During an inspection after the accident, maintenance personnel established that the floats were aligned slightly left of the aircraft's longitudinal axis. The aircraft manufacturer commented that the reported flying characteristics were consistent with the float alignment. The aircraft had been flown 23.8 hours since the last maintenance inspection, including about 10 hours by the accident pilot. No record had been made in the aircraft maintenance release regarding the 'in-flight' or 'on-water' handling characteristics.

Floatplane stability on the water

The ideal landing attitude for a floatplane is nose high, so that the rear portion of the float contacts the water first. If a floatplane lands at too high a speed (lower nose attitude than ideal), the point of contact of the floats with the water (that is, the centre of rotation of the floatplane) is at a position on the floats that is forward of the aircraft's centre of gravity and the aircraft's directional stability is reduced. If the loss of directional stability is not too severe, the pilot may be able to regain control if nose-up elevator is applied very rapidly to move the centre of rotation aft, behind the centre of gravity.

Pilot information

The pilot was the chief pilot of the company. Of his 11,256 hrs total flight time, 34 hrs were in floatplane operations, and included 79 water landings.

The pilot commenced floatplane endorsement training in October 2001. The endorsement was issued on 12 February 2002, after four sessions of training in Cessna 206 floatplanes involving 4.1 hrs and 16 water landings. Between 15 March and 25 July 2002, the pilot conducted four sessions in command under supervision in de Havilland Beaver floatplanes, involving 7.3 hrs and 23 water landings. On 25 July 2002 the company floatplane training pilot authorised the pilot to conduct solo commercial operations to specific destinations but noted that he was to be closely monitored in marginal conditions until he was more experienced.

The accident flight was the last flight of the day for the pilot. He had completed five flights with a total of 3 hrs flight time and 10 hrs duty time before the accident. The day before the accident the pilot had completed 10.2 hrs duty, including 4.8 hrs flight time during eight flights. The day prior to that was a rostered day off. He reported that neither fatigue nor any other personal issues had impaired his ability to safely operate an aircraft on the day of the accident.

The pilot's work/rest history for the 14 days prior to the accident was examined using a computerised fatigue algorithm developed by the Centre for Sleep Research, University of South Australia. The results indicated that the pilot was not experiencing significant levels of fatigue in the week leading up to, and on the day of, the accident.

Organisational information

At the time of the accident, the company employed an experienced floatplane pilot who conducted all the accident pilot's floatplane endorsement and in command under supervision training. The authority, duties and responsibilities of this floatplane pilot were not established or formalised in either the Civil Aviation Safety Authority (CASA) issued instruments of approval for key company personnel, or in the company operations manual.

The company operations manual stated that pilots with less than 250 water landings were subject to the direct supervision of the chief pilot who was to take into account the wind strength, wind direction, turbulence, tide and sea state at the origin and destination of the flight before approving a flight. There was no provision in the operations manual for when the chief pilot did not have the minimum 250 water landings experience. (Other companies required up to 300 water landings in command under supervision and 50 hours total floatplane flight time before solo commercial flight operations were permitted.)

For VFR charter in single-engine aircraft, CASA required that a pilot hold a commercial licence and the applicable aircraft special design feature endorsement, for example float alighting gear. CASA did not specify additional minimum experience requirements on the aircraft type or the special design feature.

Chief pilot appointment

Civil Aviation Order 82.0 required that a chief pilot hold licences, endorsements and ratings that permit command of all company operations. CASA had approved the pilot's appointment as chief pilot for the operator on 19 April 2002. At that time, he had obtained a float alighting gear endorsement but had not been authorised by the company to conduct solo commercial floatplane operations.

Analysis

The video recording supported the pilot's description of the event. Together they indicated that the landing technique employed by the pilot was likely to have established the centre of rotation forward of the centre of gravity with respect to the left float when it contacted the water. Under such conditions, the floatplane would have been directionally unstable and a sharp left yaw was likely. The pilot may have applied up elevator after touchdown but did not regain sufficient directional control to prevent the aircraft from colliding with the yacht.

The evidence indicated that company floatplane pilots were selecting a landing direction that provided about 50 m lateral separation from moored vessels. This separation is greater than the minimum required under marine regulations but was insufficient to prevent a collision on this occasion. The minimum separation required under marine regulations was clearly inadequate to provide a safe margin, particularly given the benign environmental conditions that existed at the time of the accident. Aviation regulations and supporting advisory material do not provide any guidance for de Havilland Beaver aircraft operators and pilots regarding appropriate lateral separation from moored vessels or other obstacles during take-off and landing operations.

The technique employed by the pilot to achieve the intended touchdown was not appropriate for floatplane operations. Its use indicated shortcomings in the floatplane endorsement training received by the pilot and reflected the pilot's low level of experience in floatplane operations. The number of water landings under supervision completed by the pilot was considerably less than that required by other floatplane operators.

It was inappropriate for the chief pilot, given his limited floatplane experience, to be responsible for company floatplane operations, with no formalised support from appropriately experienced floatplane pilots.

Analysis of the pilot's flight and duty time records suggested that fatigue did not play a role in the development of the accident.

The contribution of the misaligned floats to the development of the accident could not be determined. The lack of any maintenance release record concerning the handling characteristics of the aircraft suggests that pilots who flew the aircraft may not have considered that any aspect of the aircraft's handling characteristics warranted rectification.

Summary

The pilot of the de Havilland Beaver floatplane registered VH-BVA was conducting a charter positioning flight from Hamilton Island Marina to Chance Bay, Whitsunday Island. He had landed at Chance Bay seven times in the previous two days. Weather conditions in the area were good. At 1700 Eastern Standard Time the Hamilton Island automatic weather station recorded a 7 - 10 knot wind from the northwest. Witnesses in Chance Bay said that the surface wind in the bay was 2 - 5 knots. The water surface in Chance Bay was smooth, but not glassy.

The pilot said that he commenced a straight-in approach to Chance Bay but elected to go around due to the increased number of vessels moored in the bay since the previous flight. He flew a left circuit at 500 feet and assessed that the area for landing was adequate. He said that on final approach, the flight path was higher than he would have preferred. His intention was to touchdown before passing abeam the vessels. He recalled that the floatplane speed shortly before touchdown was about 80 knots, rather than the target speed of 70 knots. He said that his response at this time was consistent with flying a landplane in that he reduced the back pressure on the control column and allowed the floatplane to contact the water at a lower nose attitude, and at a higher speed, than was ideal. Upon touchdown, the floatplane yawed sharply left 50 - 60 degrees and headed directly towards the anchored ketch 'Seark', about 300 m away. The pilot said that the water rudders (at the rear of each float) were retracted, so all the yaw control he had available was via the conventional aerodynamic rudder. As the aircraft yawed, it felt as though the rudder was stuck at full left deflection, but he thought that this was due to hydrodynamic drag. When the floatplane was an estimated 100 m from the 'Seark', it swung right so that it was heading slightly to the east side of the 'Seark'. However, the outer portion of the floatplane's left wing subsequently collided with the rear mast of the 'Seark'.

A video recording of the event showed that the floatplane touched down with a lower nose attitude than was ideal. It also showed that the left float touched the water first. The sharp left yaw followed immediately. The aircraft became airborne momentarily, shortly after initial touchdown.

The left wing of the floatplane and the rear mast of the ketch were substantially damaged. There were no injuries to the pilot or the three occupants of the ketch.

Occurrence summary

Investigation number 200204857
Occurrence date 19/10/2002
Location Chance Bay, Whitsunday Island
State Queensland
Report release date 21/08/2003
Report status Final
Investigation type Occurrence Investigation
Investigation status Completed
Mode of transport Aviation
Occurrence class Accident
Highest injury level None

Aircraft details

Manufacturer De Havilland Canada/De Havilland Aircraft of Canada
Model DHC-2
Registration VH-BVA
Serial number 245
Sector Piston
Operation type Charter
Departure point Hamilton Island, QLD
Destination Chance Bay, Whitsunday Island, QLD
Damage Substantial

Boeing 727-277, VH-TXH

Technical Analysis Report

Technical Analysis Report: Examination of the Main Landing Gear Wheel Bearings

During a routine departure from Melbourne aerodrome, the inner left main landing gear wheel separated from a B727 aircraft (registration VH-TXH) and was later recovered near the aerodrome perimeter fence. Preliminary examination showed that the outer axle bearing had failed, allowing the wheel hub to move axially outward over the retaining nut and off the stub axle (figure 1).

Safety Action

Local safety action

Following discussions with the ATSB, the operator amended the company maintenance control manual (MCM) introducing into the "Component and Material Control" section, a Shelf Life reference applicable to the storage of wheel assemblies. This shelf life has been set at a maximum of twelve months. These amendments will be incorporated at the next revision (revision 14) of the MCM.

As the operator's maintenance control monitoring of wheel change requirements generally resulted in wheel storage periods, in house, of no more than three months prior to their use in the fleet, the operator feels that the nine-month additional shelf life buffer is adequate.

In addition, the Australian overhaul facility for the operator's wheels also introduced a twelve-month shelf life limit for its stored assemblies, after which all bearings are disassembled, inspected for corrosion and re-greased.

The amendment to both the operator's MCM and its overhaul facility procedures will minimise the possibility of wheels being returned to service with bearing integrity compromised by corrosion or grease lubrication qualities degraded through prolonged storage periods.

Significant Factors

  1. The condition of the wheel bearings and the lubricating grease was degraded during the extended storage.
  2. There was no required re-inspection maintenance procedure for lubrication quality or bearing corrosion prior to fitment of the wheel to the aircraft.
  3. The number 2 wheel outer bearing failed, resulting in the inability of the wheel retention nut to retain the wheel on the axle.

Factual Information

While on approach to land at Perth, the crew of the Boeing 727 notified air traffic control (ATC) that they required runway 21 instead of 24. This was in consideration of the wet runway conditions and as a possible precaution should they experience antiskid problems. They also advised ATC to expect a normal approach.

After parking the aircraft, the crew reported the loss of the inner left main wheel and requested rescue fire-fighting services to attend while the aircraft was secured (see Figure 1.). An inspection of the Perth runway did not find any debris.

aair200204836_001.jpg

Figure 1. Left main landing gear missing number 2 wheel.

A search conducted at Melbourne airport, the point of departure, resulted in the recovery of debris from runway 34. The wheel had impacted the perimeter fence past the runway 34 overrun area and was recovered from that location.

Inspection of the landing gear revealed that the outer bearing had failed, which allowed the wheel assembly to migrate over the locked retaining nut and depart from the axle. Landing gear damage was confined to the sacrificial alloy axle sleeve (see Figure 2).

After completion of the Boeing Conditional Inspection following bearing failure, the alloy sleeve and main wheel were replaced. As a precaution, the operator also replaced the remaining three wheels of the main landing gears. As the nose landing gear wheels were from a different overhaul facility, it was not considered necessary to replace them prior to the aircraft returning to service. The line engineers who removed the main wheels verified that bearing dust seals were present on all the remaining wheel bearings.

aair200204836_002.jpg

Figure 2. Left main landing gear axle damage.

The inner bearing cone of the lost wheel was recovered from the aircraft landing gear and, along with the wheel bearings from the remaining three wheels, was sent to the ATSB for further technical analysis. The separated main wheel and bearing cone debris recovered in Melbourne were also forwarded to the ATSB.

Main wheel assemblies

The operator had recently acquired the aircraft on lease after it had been in long term storage in the USA. During the process of transfer to the Australian register, the American owner sourced a serviceable set of main wheel assemblies to standardise the aircraft with the rest of the Australian operator's fleet. The wheels carried release to service documentation after overhaul from an approved American maintenance facility.

The incident wheel (number 2) had been overhauled in accordance with approved data and released for service with the correct documentation on 14 November 2000. The wheel was subsequently fitted to the Boeing 727 on 31 August 2002. The wheel was in storage for all the intervening period between release to service and fitment to the aircraft. The remaining wheel (number 1) on the left landing gear had been overhauled in accordance with approved data and released for service with the proper documentation on 7 December 2001. The wheel was subsequently fitted to the aircraft on 31 August 2002.

Wheel numbers 3 and 4 on the right landing gear were overhauled in accordance with approved data and released for service with the proper documentation on 17 and 22 August 2001 respectively. The wheels were subsequently fitted to the aircraft on 29 August 2002. Although still a lengthy storage period, wheel numbers 1, 3 and 4 had been in storage for a significantly shorter period than wheel number 2.

The quality assurance inspector for the overhaul facility stated that, although not mandated, the company recommended to customers to re-inspect stored wheels every twelve months. He also stated that, after overhaul, all wheels were returned to their owners, and the company did not hold any wheels in long-term storage. As part of the shipment preparation, the overhaul company routinely packed the wheel bearings in grease and sealed them in plastic bags before they were placed in the wheel assemblies. The plastic bags were to be removed before the wheel re-entered service. With no wheel assemblies stored at the overhaul facility, the company had no requirement for a repetitive storage inspection procedure to be in place. This meant that the wheels fitted to the aircraft had been returned after overhaul to their owner (the aircraft owner) and were placed in storage at a site other than the overhaul facility. The aircraft owner had then supplied the wheels to the Australian operator for fitment to the Boeing 727.

At the time of the incident, the aircraft operator's maintenance control manual did not include a section relating to wheel storage and tracking procedures, which specifically mandated a storage life expiry interval and re-inspection procedure for wheels. The maintenance personnel who fitted the wheels to the aircraft stated that the wheels were received from the USA with the bearings in place. There were no reports of the bearings being received in plastic bags as described by the overhaul facility. There was also no paperwork supplied to the Australian operator to suggest that the wheels had been fitted to another aircraft after overhaul.

ATSB laboratory component examination

While damage to the failed bearing prevented the determination of specific factors that contributed to the failure of the particular unit, the evidence found during the investigation suggests that the development of corrosion damage over the contact surfaces of the wheel bearings was a major factor contributing to the failure. This was evident in the bearings examined from the remaining wheels. The corrosion led to insipient contact fatigue spalling, which is well understood can lead to catastrophic bearing failure consistent with the circumstances of this occurrence. The bearing lubricating grease was found to be congealed, hardened and in a dry state. A foreign material identified as brake dust was also found in the grease. The inclusion of this foreign material may also have contributed to the failure.

Summary

While on approach to land at Perth, the crew of the Boeing 727 notified air traffic control (ATC) that they required runway 21 instead of 24. This was in consideration of the wet runway conditions and as a possible precaution should they experience antiskid problems. They also advised ATC to expect a normal approach.

After parking the aircraft, the crew reported the loss of the inner left main wheel and requested rescue fire-fighting services to attend while the aircraft was secured. An inspection of the Perth runway did not find any debris.

Occurrence summary

Investigation number 200204836
Occurrence date 18/10/2002
Location Melbourne, Aero.
State Victoria
Report release date 23/06/2003
Report status Final
Investigation type Occurrence Investigation
Investigation status Completed
Mode of transport Aviation
Occurrence class Incident
Highest injury level None

Aircraft details

Manufacturer The Boeing Company
Model 727
Registration VH-TXH
Serial number 20549
Sector Jet
Operation type Air Transport High Capacity
Departure point Melbourne, VIC
Destination Perth, WA
Damage Minor

Cessna 182B, VH-PDK

Significant Factors

  1. The weather conditions at the time of the accident were favourable to the development of lee waves and strong downslope winds in the vicinity of the airstrip.
  2. The aircraft banked steeply out of wind, while at low airspeed and a low height.
  3. The aircraft stalled at an altitude from which recovery by the pilot was not considered possible and control of the aircraft was lost.



 

Analysis

Witnesses observed the C182 at low altitude on approach to Turalla. Their reports that the wings were rocking from side to side were consistent with the turbulence that may have been produced in the lee of the escarpment by the strong wind. Down draughts and rotor turbulence could have resulted from the vigorous airflow at right angles to the escarpment, immediately to the west of the airstrip, and existed for a considerable distance downwind of the escarpment.

An approach to land in those conditions should not have placed any exceptional demand on the pilot's skill. The strip was aligned nearly into wind and the pilot was familiar with both the airstrip and the aircraft. The pilot had probably flown from the airstrip in similar conditions previously and should have been aware of the potential for turbulence and down draughts. The landing distance available was more than adequate for the aircraft type.

In turbulent conditions a pilot can elect to use less than maximum flap, or even no flap for the approach and landing. In a strong headwind, this would not significantly increase the aircraft's landing distance. Using less than full flap on the C182 can improve aircraft handling in turbulence. However, using less flap at lower airspeeds and higher angles of bank, significantly increases the aircraft stall speed.

Although the reason the approach was discontinued was unable to be determined, it was possible that the approach became unstable in the turbulence with airspeed fluctuations. The pilot appeared to have turned right to initiate a low-level circuit. Familiarity with the airstrip and anticipating turbulence in the lee of the escarpment may have been the reason that the pilot initiated a right turn rather than climbing straight ahead, which could have placed the aircraft into an area of increased turbulence. The direction of turn was consistent also with the pilot turning away from the glare of the setting sun. The pilot's memory of his siblings' accident may have influenced the decision-making process to make a rapid escape from the area of turbulence.

Witnesses reported that the aircraft's angle of bank was between 60 and 80 degrees when the approach was discontinued. There was no apparent reason for a steep turn to be made. There was no necessity for the pilot to rapidly make another approach and landing. There were adequate margins for both daylight and fuel.

The altitude at which the aircraft was seen to be operating would probably not have been sufficient to allow recovery from a stall, even with a pilot proficient in the technique. It was also possible that at the extreme angles of bank, a sudden loss of lift resulting from windshear or turbulence, or a rapid retraction of the manually operated flaps, could have placed the aircraft in a stalled condition from which recovery would have been unlikely at such a low height.

Factual Information

History of the flight

The pilot of the Cessna 182B Skylane (C182), with one passenger on board, departed Leongatha aerodrome in Victoria at about 1530 Eastern Standard Time (EST). The pilot planned the private flight in accordance with the visual flight rules to track coastal to Moruya and then via the Araluen Valley to 'Turalla', a private property located approximately 3 km northwest of Bungendore, NSW. The aircraft carried sufficient fuel for the flight.

Witnesses reported that, at about 1755, the aircraft overflew a property belonging to a relative of the pilot 3 km to the southeast of Bungendore, at about 500 ft AGL. That relative had been nominated as the responsible person to hold and cancel the nominated SARTIME of 1820. The aircraft was then observed to track west towards the Kings Highway, at a low level, and make a right turn to join a wide left base for the grass airstrip located at 'Turalla'. The airstrip was aligned approximately 305 degrees M. The aircraft was observed to turn left onto final approach at about 50-80 ft AGL. Witnesses reported that all turns were made using about 45 degrees angle of bank. Witnesses also observed the aircraft to be buffeted by gusting winds.

The weather at the time was reported by witnesses to be clear conditions with some upper level cloud. Winds were strong and blustery, from the west and northwest. A Bureau of Meteorology assessment of the weather indicated gusty north-westerly winds backing to the west after the passage of a front, which had occurred earlier in the day. The general wind structure lent itself to at least moderate turbulence and the strong possibility of lee waves and strong downslope winds.

While on short final, the aircraft was observed to make a steep climb towards a downwind position, turning to the right using 60-80 degrees angle of bank. It was then observed to lose altitude rapidly. It turned through about 295 degrees before impacting the ground approximately 300 m east-north-east of the airstrip threshold. The aircraft struck the ground at a 60-80 degree nose down, left wing low, attitude on a heading of about 240 degrees M. The aircraft was destroyed by impact forces and post-impact fire.

Injuries to persons

The passenger was fatally injured. Autopsy and toxicological tests conducted on the passenger revealed a low level of carbon monoxide in the blood. Medical opinion indicated that death occurred prior to the commencement of the post-impact fire. The pilot was seriously injured and survived the accident for 68 days before succumbing to the effects of his injuries.

Annex 13 to the Convention on International Civil Aviation, Aircraft Accident and Incident Investigation, defined a fatal injury as an injury that resulted in death within 30 days of the date of an accident.

Wreckage and impact information

A post-impact fire consumed the cockpit area. The extent of the fire damage precluded a productive examination of the cockpit, controls and instruments. Many of the alloyed components had been reduced to a molten state. Examination of the wreckage indicated that at the time of impact the aircraft was not configured for landing. The wing flaps were set to the retracted position. The engine was removed from the accident site for technical examination. The examination determined that the engine was capable of normal operation prior to impact and that it was producing power at the time of impact. Nothing was found during the investigation to suggest that mechanical failure of any part of the aircraft could have contributed to the accident.

Personnel Information

The pilot held a current private pilot's licence, was endorsed on the aircraft type and familiar with the landing area. A review of the pilot's personal flying logbook indicated that he had accumulated in excess of 340 hours total time, most of which were accrued on the occurrence aircraft. Four days prior to the accident, the pilot had satisfactorily completed a biennial flight review. The pilot held a valid Class 2 Aviation Medical Certificate. The pilot had just completed a short hiking holiday and there was no evidence to indicate any physical or psychological conditions that may have adversely affected his ability to pilot the aircraft.

Landing area

The landing area at Turalla was inspected after the accident. With the exception of a centrally located windsock, there were no aerodrome markings to detail the exact location and dimensions of the airstrip. There was evidence of recent aircraft use on the grass strip. The landing distance available was approximately 800 m, orientated approximately 305 degrees M. There was no evidence to indicate that livestock had been grazing on the paddock that contained the airstrip in the past month. A north-south ridgeline was located approximately 1 km to the west of the airstrip. At the time of the accident, the sun was setting in the west and was visible above the horizon.

Previous occurrence at the airstrip

One of the pilot's brothers and a sister were fatally injured in a separate aircraft accident (Bureau of Air Safety Investigation Report No. BO/199603734) in the vicinity of the same airstrip in 1996, when similar wind conditions were experienced. On that occasion, the Cessna U206F (C206) aircraft was climbing on departure from Turalla when the pilot turned left onto downwind. The C206 stalled at a height from which it was not possible to recover.

Summary

The pilot of the Cessna 182B Skylane (C182), with one passenger on board, departed Leongatha aerodrome in Victoria at about 1530 Eastern Standard Time (EST). The pilot planned the private flight in accordance with the visual flight rules to track coastal to Moruya and then via the Araluen Valley to 'Turalla', a private property located approximately 3 km northwest of Bungendore, NSW. The aircraft carried sufficient fuel for the flight.

Witnesses reported that, at about 1755, the aircraft overflew a property belonging to a relative of the pilot 3 km to the southeast of Bungendore, at about 500 ft AGL. That relative had been nominated as the responsible person to hold and cancel the nominated SARTIME of 1820. The aircraft was then observed to track west towards the Kings Highway, at a low level, and make a right turn to join a wide left base for the grass airstrip located at 'Turalla'. The airstrip was aligned approximately 305 degrees M. The aircraft was observed to turn left onto final approach at about 50-80 ft AGL. Witnesses reported that all turns were made using about 45 degrees angle of bank. Witnesses also observed the aircraft to be buffeted by gusting winds.

The weather at the time was reported by witnesses to be clear conditions with some upper level cloud. Winds were strong and blustery, from the west and northwest. A Bureau of Meteorology assessment of the weather indicated gusty north-westerly winds backing to the west after the passage of a front, which had occurred earlier in the day. The general wind structure lent itself to at least moderate turbulence and the strong possibility of lee waves and strong downslope winds.

While on short final, the aircraft was observed to make a steep climb towards a downwind position, turning to the right using 60-80 degrees angle of bank. It was then observed to lose altitude rapidly. It turned through about 295 degrees before impacting the ground approximately 300 m east-north-east of the airstrip threshold. The aircraft struck the ground at a 60-80 degree nose down, left wing low, attitude on a heading of about 240 degrees M. The aircraft was destroyed by impact forces and post-impact fire.

Occurrence summary

Investigation number 200204663
Occurrence date 13/10/2002
Location 2 km W Bungendore
State New South Wales
Report release date 18/07/2003
Report status Final
Investigation type Occurrence Investigation
Investigation status Completed
Mode of transport Aviation
Aviation occurrence category Collision with terrain
Occurrence class Accident
Highest injury level Fatal

Aircraft details

Manufacturer Cessna Aircraft Company
Model 182
Registration VH-PDK
Serial number 51673
Sector Piston
Operation type Private
Departure point Leongatha, VIC
Destination Turalla, NSW
Damage Destroyed
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