A de Havilland Canada Dash 8-102 (northbound Dash 8) was en route from Brisbane to Gladstone at flight level (FL) 140. A second de Havilland Canada Dash 8-102 (southbound Dash 8) was tracking from Gladstone to Brisbane via Maleny (MLY) also at FL140. Those routes placed the aircraft on reciprocal tracks with approximately 1.25 NM lateral displacement. The Keppel (KPL) and Alma (LMA) sectors were combined. The controller was responsible for the airspace that extended from approximately 80 NM north of Brisbane to approximately 70 NM north of Rockhampton and from the coast to approximately 90 NM to the west. The KPL/LMA sector controller received a Short Term Conflict Alert (STCA) between the aircraft when they were approximately 10 NM apart. The STCA was a collision avoidance tool in The Australian Advanced Air Traffic System (TAAATS). The controller instructed the crews of both aircraft to turn 90 degrees to the right and issued traffic information to the crew of the northbound Dash 8 about the southbound Dash 8. The aircraft passed 5.4 NM abeam each other. The radar separation standard was 5 NM. Each crew had the other aircraft in sight. There was no infringement of separation standards.

Traffic levels at the time of the occurrence were considered low. There were two aircraft to the northwest of Brisbane that required the attention of, and coordination between, the KPL/LMA controller and the Burnett (BUR) controller.

The KPL/LMA controller had assigned the crew of the southbound Dash 8 FL190. The crew subsequently requested and was assigned FL150. Eight minutes later, the crew requested "amended non-standard FL140". Use of the standard levels for the track flown would normally provide a degree of separation assurance between aircraft. A non-standard level was a level that was not in accordance with the table of cruising levels detailed in the Manual of Air Traffic Services. The controller approved the crew's request for the level change. Shortly after, the southbound Dash 8 was maintaining FL140. The controller then conducted a handover/takeover and another controller assumed responsibility for the sectors.

The crew of the southbound Dash 8 reported a layer of stratus at FL150 extending from Gladstone almost to Brisbane. The crew requested FL140 to remain beneath the cloud and avoid any associated turbulence; although the crew did not provide a reason to the controller at the time of the request. Flight level 130 was available and was the standard level but was not requested because the crew thought the base of controlled airspace was FL130 in that area and was therefore outside controlled airspace. The base of controlled airspace was FL125. Flight level 130 would have kept the aircraft within controlled airspace and would have provided a minimum of 500ft vertical separation with aircraft operating outside controlled airspace.

The crew of the northbound Dash 8 had been cleared to FL180 on departure from Brisbane. The crew reported on climb to FL180 and requested amended FL140 from the BUR sector controller. That controller re-cleared the crew of the northbound Dash 8 at FL140, a standard level. The controller also re-cleared the crew direct to Gladstone when the aircraft was clear of conflicting traffic in the BUR sector. Local instructions enabled controllers to approve direct tracking subject to a number of conditions. One of those conditions stated that direct tracks were available on "northbound tracks that are east of and will not cross a line MLY-RK [Rockhampton]: landing within the lateral limits of Fraser airspace". The track of the northbound Dash 8 met those requirements.

The BUR sector controller then transferred control responsibility of the northbound Dash 8 to the KPL/LMA controller. A transfer of control responsibility, or hand off, was performed when one controller highlighted the subject aircraft on another controller's Air Situation Display (ASD). The symbol then changed colour to indicate the intention to transfer control responsibility. The symbol changed colour again when control responsibility had been accepted. Crews were instructed to change to the next control frequency following acceptance of the hand off. Following the hand off, the northbound Dash 8 entered KPL/LMA sector. Both the northbound Dash 8 and the southbound Dash 8 were maintaining FL140. Neither the KPL/LMA nor the BUR controllers were required to voice coordinate level changes or changes in tracking. That information was entered into TAAATS by the responsible controller and was updated automatically at all relevant consoles.

The assignment of the non-standard level to the southbound Dash 8 was not considered significant by the first KPL/LMA controller because the aircraft was within radar coverage. There was a general awareness of standard levels among the KPL/LMA controllers interviewed, but none considered the use of standard levels essential for aircraft within radar coverage. The use of standard levels often did not achieve separation assurance because much of the sector's traffic climbed and descended into and out of coastal ports and controllers had to monitor aircraft altitude or levels to ensure vertical separation was maintained. The controller assigned FL140 to the southbound Dash 8 as there were no conflictions at that time and the use of a non-standard level was not uncommon.

The second controller believed he had missed the significance of the non-standard level because he had not issued the level himself and did not use any scanning techniques after the takeover that may have highlighted the conflict. He advised that he would have normally highlighted the label of an aircraft at a non-standard level using the individual quick look (IQL) function available on TAAATS. The IQL function was used to check hidden track label details but also changed the colour of a label on an individual console. The controller could not recall whether the first controller had drawn his attention to the non-standard level during the handover/takeover. The first controller did not believe he had mentioned the non-standard level during the handover/takeover.

The use of direct tracking by the BUR controller meant that the northbound Dash 8 would require either a different level or radar vectoring to maintain separation with the southbound Dash 8. The flight-planned route for northbound traffic provided a segregated two-way route structure between southbound aircraft on the Gladstone-Maleny track, and northbound traffic. However, the segregated two-way route structure was not usually used because direct tracking provided separation assurance between succeeding northbound aircraft departing Brisbane and facilitated traffic management along the coast.

The southbound Dash 8 had maintained FL140 for approximately twelve minutes prior to the time the KPL/LMA controller received the STCA. The crew of the northbound Dash 8 had reported maintaining FL140 three minutes prior to the time the KPL/LMA controller received the STCA.

The KPL/LMA controller reported that he had maintained radar surveillance, had not been distracted and was aware of both aircraft. The controller was fit for work and all equipment was serviceable. The controller advised however, that he had taken his family on a short trip to relax. He had returned two days before the occurrence but had been unable to relax. He also stated that he usually stayed up late at night and preferred to sleep until mid-morning. The night before the occurrence the controller stayed up until midnight but had awoken in sufficient time to commence duty at 7:00am on the day of the occurrence. He also reported that he had been discussing the inbound sequence with other controllers immediately prior to the occurrence.

The tracks for aircraft operating in non-radar airspace, being monitored by automatic dependent surveillance (ADS) in the Melbourne Air Traffic Control Centre, were not updated at controller air situation displays in the Bight and West Groups. A controller noticed the problem following a missed position report alarm for a foreign registered Boeing 747 aircraft. An Airservices Australia investigation found that controller workstations were not being updated with ADS data after a problem in the air ground data processor (AGDP) of The Australian Advanced Air Traffic Control System (TAAATS). There were no infringements of separation standards.

There were no visual or aural alerts to indicate that the AGDP had failed. The ADS tracks froze for approximately 20 minutes before recovery action was initiated and completed by controllers.

The Airservices' investigation found that an error in address tables, as a result of maintenance by the service provider responsible for transferring data between Airservices and nominated aircraft, stopped the flow of data to TAAATS. A combination of the stopped data flow and an uncommanded switch of the AGDPs caused the ADS tracks to freeze.

Those actions also appeared to have caused the main processor to "loop". Normally, one of the dual processors would have recognised that there was a problem and would have assumed the master role. However, that action did not occur and the standby processor remained in standby mode believing that the other processor was operating correctly in the master mode. Airservices has corrected the looping problem and it will be included in Version 7.3.56 of the TAAATS software. In the interim, Airservices have enhanced the indicator that shows when there has been a AGDP switch to prompt technical and operational staff to check that the system is operating correctly.

The investigation also found that controllers' recovery actions that had worked during previous similar events did not work on this occasion. Controllers were constrained by the lack of appropriate procedures in the Degraded Modes Handbook.

The pilot of a Cessna 172 was conducting a solo navigation flight from Essendon with planned landings at Latrobe Valley and Leongatha. At approximately 1030 EST the pilot broadcast on the Latrobe Valley common traffic advisory frequency (CTAF) of 126.0 MHz his intention to make a full stop landing on runway 03. Witnesses at the airfield heard the sound of engine power increasing and saw the aircraft commence what appeared to be a missed approach from about 100 ft on short final. They reported that the aircraft entered a steep left climbing turn onto a reciprocal heading with flaps fully extended. At an estimated height of about 300 ft the wings were seen to roll level and the aircraft, with a nose high attitude, "fishtailed". Then with the engine noise unchanged, the aircraft pitched nose down and impacted the ground adjacent to the runway. The pilot was fatally injured, and the aircraft was destroyed by impact forces. The reason for the go-around was not determined.

Weather at the time of the accident was clear sky and unlimited visibility with a light north easterly breeze. There was no other aerodrome traffic.

Examination of the wreckage found no evidence to suggest that the aircraft was not capable of normal operation. The ancillary controls were configured for the approach; that is, flaps set to approximately 40 degrees, elevator trim at a position corresponding to the position for that flap setting, approach speed and power, and carburettor heat ON.

Although there was wear to the rollers, seat rails and the locating holes, the pilot seat locking mechanism was capable of normal operation. The pilot seat stops were fitted to the inboard rail and were of inverted "U"-shaped metal design. They were placed over the rail and secured by a split pin that passed through a slot in the rail. They were similar to seat stops used in many Cessna aircraft.

An inspection of the Cessna 172 parts manual revealed that the seat stop locations were specified differently, depending on aircraft serial number. The stops specified in the parts manual consisted of a flat metal section with a threaded hole in the centre that passed through the slot in the seat rail and secured by a screw inserted through the locating hole in the rail, and screwed into the stop. The forward stop was secured through the most forward slot in the rail and, unlike the specified part, was able to lie forward over the front end of the rail. That installation permitted the seat to be adjusted forward beyond the first locating hole. Marks on the left seat rail indicated that the pin of the pilot's seat might have been incorrectly secured forward of the end of the seat rail. There would have been no indication to the occupant of the seat that the locking mechanism had engaged in that manner, or that the seat was not properly locked into position, other than by close visual inspection.

The rear stop of the pilot's seat was located at a point 410 mm forward of the door rear pillar. The seat of a similar aircraft was set to a corresponding position and when seated at that distance from the controls, a pilot of similar stature to the accident pilot, was unable to reach the flap switch, carburettor heat or elevator trim controls. That pilot was unable to apply any significant forward elevator control and only by pulling back on the control wheel was the pilot able to lean forward sufficiently to reach the throttle in the fully open position.

Flight tests were conducted using a similar aircraft. The aircraft was configured for an approach with a flap setting of 40 degrees and the aircraft trimmed to an approach speed of 60 kt. After applying full power and then using limited elevator and full aileron control inputs only, it was possible to fly a manoeuvre similar to that described by witnesses.

The accident pilot held a Student Pilot Licence and was appropriately qualified to undertake the flight. He held a valid Class 2 medical. Instructors who had trained the pilot reported that although his flying did not reflect the level of skill commensurate with his flying experience, he had satisfactorily demonstrated missed approach manoeuvres in the Cessna 172. They reported that he was able to achieve full control input with the seat adjusted well forward despite his short physical stature.

History of the flight

The Airbus A330-341 aircraft was operating a scheduled international fare-paying passenger service from Adelaide to Melbourne and the pilot in command was the handling pilot for the flight. During the initial descent into Melbourne, the crew configured the auto flight system to the approach mode. That action armed the auto flight system localiser and glideslope modes for the runway 16 instrument landing system (ILS), and permitted the crew to engage the second autopilot for the approach. As the aircraft descended through 2,500 ft, the crew placed the ground spoiler handle to the armed position. Shortly after, the radio altimeter indications disappeared from both pilots' electronic flight instrument displays. Both autopilots then disengaged. About 20 seconds later, both flight directors disengaged from the localiser and glideslope modes but re-engaged in the basic modes of current vertical speed and heading.

The pilot in command elected to continue the approach and to manually fly the aircraft, because he considered that he would be able to control the aircraft without auto flight system approach commands or radio altimeter information. The autothrust was unaffected by the disengagement of the autopilots, and remained engaged.

At the completion of the landing approach, the pilot in command flared the aircraft for the landing, and retarded both thrust levers, which disengaged the autothrust system. The aircraft landed on the left and right main landing gears, bounced, and became airborne for four and a half seconds before touching down again on both main landing gears. The aircraft bounced again, became airborne for one second, and then touched down for a third time on both main landing gears. The right main landing gear then lifted off the runway for about one second, after which the aircraft settled onto both main landing gears. Two seconds later, the thrust levers were advanced to go-around power, and after a further five seconds, the aircraft became airborne again. The nose landing gear remained airborne throughout this sequence. Additionally, the ground spoilers did not deploy, and the thrust reversers did not activate.

The pilot in command repositioned the aircraft for another approach onto runway 16. During the second landing, the aircraft again bounced following the touchdown, then settled onto the runway. Four seconds later, the ground spoilers deployed; however, the thrust reversers did not activate when selected by the crew. The landing rollout was completed without further incident, and the aircraft was taxied to the terminal.

There were no injuries to any persons on board the aircraft.

Aircraft information

The aircraft was a fly-by-wire type. Three flight control primary computers and two flight control secondary computers controlled the flight control system. The computers processed crew and autopilot inputs to provide appropriate electrical output signals to the hydraulically powered flight control surfaces.

Crew input to the flight control computers was made via electrical signals from either of the two side stick controllers, and autopilot input was made via an interface with the aircraft's Flight Management and Guidance System.

The inputs to the flight control computers were processed in accordance with respective flight control 'laws'. Regardless of the pilot's inputs, the control computers will prevent excessive manoeuvres and/or exceedance of the safe flight envelope. Those laws were dependent on whether the aircraft was in the ground, flight or flare mode of flight. In the ground mode, there was a direct relationship between sidestick deflection and the flight control surfaces. In the flight mode, deflection of the flight control surfaces was governed to achieve a load factor proportional to sidestick deflection, independent of speed. Flight mode provided 3-axis control of the aircraft, and provided flight envelope protection and manoeuvre load alleviation.

In the flight mode, the normal laws were:

• Nz law for pitch control, including load factor protection. (Nz law is vertical acceleration in the normal axis of the aircraft);
• lateral normal law for lateral control (roll and yaw), including bank angle protection; and
• protection against high speed (VMO), pitch angle (theta), and stall (angle of attack).

In flare mode, the normal laws were:

• flare law in place of Nz law for pitch control to allow for conventional flare;
• lateral normal law for lateral control (roll and yaw) including bank angle protection; and
• protection against stall.

Flare mode permitted crews to use the same landing technique as for non-fly-by-wire aircraft. Transition from flight mode to flare mode occurred when the aircraft's radio altimeters sensed that the aircraft altitude was less than 100 ft above ground level.

If faults were detected in both radio altimeters, switching from flight mode to flare mode would occur when the landing gear was extended, provided the autopilot was off. If the autopilot was engaged, switching from flight mode to flare mode would occur when the autopilot was disengaged, provided the landing gear was extended.

The manufacturer reported that flight tests for the A330 type included landing in flight mode. ie without transition to flare mode. Landing in that condition was not considered difficult, however, it required a different handling technique than would otherwise apply for non-fly-by-wire aircraft. In such circumstances, a pilot would need to apply back pressure on the sidestick to initiate the landing flare, then release that back pressure to maintain the desired pitch attitude until touchdown.

The aircraft was equipped with two radio altimeter systems that provided information about the aircraft height above ground level. Data from the radio altimeters was also used by many of the aircraft systems' logic sequences to determine whether certain operating parameters had been met to permit operation of a particular system. The radio altimeter antennas were located along the keel of the aft fuselage of the aircraft, and were connected to the aircraft electronic system by coaxial cables. Inspection of the radio altimeter system antennas subsequent to the occurrence revealed that they had sustained water ingress at the antenna coaxial cables. The water ingress into the radio altimeter antennas resulted in the radio altimeter signals being interpreted as out of range signals, rather than as a failure of the radio altimeters.

During the period 11 June 2001 to the date of the occurrence, there were 19 entries in the aircraft's maintenance log reporting problems with the radio altimeters fitted to the aircraft. Repairs had been carried out on the radio altimeters, including replacement of a transceiver unit and cleaning of components due to water ingress.

The aircraft was equipped with autoflight and flight director systems. Radio altitude signals from the aircraft radio altimeters were used to engage the autoflight system into the LAND mode when the aircraft altitude was 400 ft above ground level. The loss of valid radio altimeter signals in LAND mode would result in the loss of both autopilots and the flight directors reverting to the basic modes of vertical speed and heading. The autopilot also used radio altitude signals to adapt the autopilot gains during an ILS approach, with the required gain being dependent upon the distance of the aircraft from the runway threshold. Any involuntary disconnection of the autopilot triggered an AP OFF INVOLUNTARY warning message to the crew.

The aircraft was equipped with wing mounted ground spoilers. The ground spoilers would arm when the crew placed the speed brake control lever to the armed position, and would activate after landing provided certain parameters had been met. Those parameters included both main landing gears transitioning from flight to ground ('weight on wheels'), and a radio altitude of less than 6 ft or a wheel speed higher than 72 kts on the front and rear wheels of the main landing gears.

The aircraft's engines were equipped with thrust reversers. Deployment of the thrust reversers would not occur unless the aircraft was on the ground with the ground spoilers extended, radio altitude less than 6 ft, and the engine thrust levers in the reverse position.

The aircraft was equipped with an Allied Signal solid state digital flight data recorder. The recorded data was examined and revealed that each of the flight control primary and secondary computers had operated normally throughout the flight. The recorded data revealed that during both approaches, the autopilots oscillated in the lateral and longitudinal axes.

Both autopilots disconnected simultaneously, but an AP OFF INVOLUTARY warning did not accompany the disconnection. The LAND mode engaged at 400 ft radio altitude. One second later, both flight directors disengaged from the localiser and glideslope modes, then re-engaged in the basic modes of current vertical speed and heading. The recorded data also revealed that the signals from both radio altimeters were invalid throughout most of both approach sequences into Melbourne.

The investigation was unable to determine the relevant experience and training of the crew.

The Bell Jetranger 206B (III) helicopter was engaged in aerial firefighting operations utilising an external water bucket and staging out of a nearby national park campground. The pilot reported that he started flying at approximately 0750 EST after completing a pre-flight check of the helicopter which included draining the fuel sump, inspecting the fuel and confirming 106 L or 27.9 United States Gallons (USG) of total indicated fuel. At approximately 0825, while engaged in water bucket operations, he discussed his fuel status with other company pilots on a common radio frequency and noted 38 L (10 USG) of indicated fuel remaining. He finished a swath run of the fire area, dropping water and then decided to complete one more swath run before returning to refuel.

Approaching the fire line, the helicopter entered a left turn at approximately 200 ft above ground level (AGL). The pilot reported that the helicopter was buffeted by strong turbulence, which caused the helicopter to yaw left and go out of trim. He reported that the engine power then began surging and, subsequently, an engine flameout occurred. He continued the left turn, jettisoned the water and initiated a power-off autorotation to a heavily wooded area.

During the autorotation, the helicopter's main rotor blades contacted nearby trees, damaging the blades and displacing the main rotor transmission. The helicopter then came to rest on its right side, on a 45 degree slope. The pilot exited the helicopter and was picked up by another company helicopter and transported to hospital for observation. The pilot suffered minor injuries and the helicopter was substantially damaged. There was no evidence of any in-flight or post-accident fire.

The pilot reported that he had no recollection of any illuminated caution advisory lights during or prior to the event, or of the position of the switches and circuit breakers of the fuel boost pumps. He stated that he followed flight manual checklists when starting the helicopter and preparing for takeoff.

Wreckage examination

The helicopter sustained damage to the main rotor blades and controls, main rotor transmission, transmission to engine driveshaft, tail rotor driveshaft, pilot's perspex and right side forward fuselage. Examination of the engine revealed no external damage or damage to the compressor.

Fuel system examination and background

After the helicopter was repositioned upright, the fuel gauge indicated approximately 19 L (5 USG). The fuel in the fuel tank was examined and appeared to slightly cover the base of the fuel boost pumps. Examination of the airframe fuel filter revealed full fuel in the filter bowl and no contamination. Examination of the engine fuel filter revealed a small amount of fuel and no contamination. The forward fuel boost pump circuit breaker was noted as disengaged.

Unusable fuel was defined as, `Fuel that cannot be used in flight with wings level and at cruise angle of attack (or nose 3 degrees up)'. Of the total fuel on board, 4 L (1 USG) were unusable. Upon removal from the accident site, the helicopter's fuel system was drained and 23.5 L (6.2 USG) of fuel were removed. The fuel correction card annotated, `gauge indicates 38 L (10 USG) for an actual of 45.6 L (12 USG)'. The fuel correction card values were verified by adding measured amounts of fuel.

An option on that model helicopter was a FUEL LOW caution advisory light that illuminated with approximately 76 L (20 USG) of total fuel remaining. The helicopter was not equipped with that advisory light. It was equipped with two electrically operated submerged fuel boost pumps located in the fuel cell and connected in parallel to the engine's fuel supply line. Those pumps were located on the helicopter's centre-line. Both boost pumps were examined following the accident and they were determined to be serviceable.

Fuel consumption

According to the operator's operations manual, the fuel consumption rate of the Bell 206B (III) helicopter was 110 L (28.9 USG) per hour. In the 35 minutes of operating time that the pilot reported prior to the accident, approximately 64 L (16.8 USG) of fuel should have been consumed, leaving approximately 30.8 L (8.1 USG) of useable fuel remaining. That amount should have been sufficient for approximately 17 minutes of engine operating time.

Engine auto-reignition

The helicopter was not fitted with an optional engine auto-reignition system. Because of the low height AGL at the time of the engine surging and flameout, the pilot did not have an opportunity to attempt a manual restart of the engine.

Engine testing

The Rolls-Royce Allison model 250-C20B engine, serial number CAE 840551, was removed from the helicopter and transported to an engine test cell for testing. Following motoring and priming, the engine started on the first attempt with Turbine Operating Temperatures, N1 (gas generator speed) and N2 (power turbine speed) values within normal operating parameters. Engine deceleration and acceleration tests were conducted in order to simulate power changes experienced during flight. The results of the testing indicated that the engine was serviceable at the time of the accident.

Helicopter manoeuvring in turns and flight manual requirements

During coordinated turns, centrifugal force acting on the helicopter and fuel tank causes the fuel to collect evenly in the bottom of the fuel tank. It is then available for pick up by the fuel boost pumps at the boost pump inlets and through to the inlet of the main fuel supply line and to the engine. During uncoordinated turns, centrifugal force may not displace the fuel to the bottom of the tank evenly and instead fuel sloshing may take place.

The helicopter's flight manual contained a warning regarding flight with one fuel boost pump inoperative. It stated, `Due to possible fuel sloshing in unusual attitudes or out of trim conditions and one or both fuel boost pumps inoperative, the unusable fuel is ten [US] gallons'.

Component testing

The forward fuel boost pump circuit breaker was removed and tested. Aircraft system 28 DC voltage was applied and varying amperes were introduced to the circuit breaker in an attempt to determine its serviceability. The circuit breaker operated normally up to its rated 10 ampere rating with no anomalies noted.

Pilot's shoulder harness

The pilot's left shoulder harness had broken and separated at a point just forward of and below the pilot's shoulder. The manufacturer's date stamped on the harness belt was March 1973. The pilot's seat belt had an inspection tag attached with the inspection date 11/99 annotated. Details of the inspection were not annotated in the helicopter's documentation.

Pilot shoulder harness testing

The pilot's left shoulder harness was sent to an independent belt and harness testing and repair organisation for testing. The webbing was identified as MIL-T-50368 Type IV, 2 inch Nylon Webbing, rated at 2,000 pounds strength. The rated assembly strength of the harness assembly was 1,500 pounds. Testing revealed that the webbing failed at a value of 391 pounds, or less than 20 percent of the original strength of the material. Factors contributing to the loss of original strength were ageing related to ultraviolet light exposure, abrasion damage and contamination by turbine oil.

Seat belt and shoulder harness standards

Australian Civil Aviation Order (CAO) Part 108, Section 108.42, contained specifications for aircraft safety belts (seat belts), harnesses (shoulder harnesses) and inertia reels manufactured in Australia. Contained within CAO Part 108, Section 108.42 was a reference to Technical Standard Order (TSO)-C22g, which specified minimum performance standards of aircraft seat belts when new.

CAO Part 108, Section 108.42, also contained a reference to British Air Registration Board (ARB)/Civil Aviation Authority (CAA) Specification Number four (issue two). That document specified minimum performance standards for British manufactured aircraft shoulder harnesses when new and was not applicable to equipment manufactured in the United States of America (USA) such as the separated harness in this occurrence.

The Australian Civil Aviation Safety Authority (CASA) Airworthiness Directive, AD/RES/29 amendment 1, mandated identification of aircraft seat belts to indicate that the part was an item approved by the manufacturer. Part of that directive mandated appropriate identification to demonstrate compliance with CAO Part 108, Section 108.42.

The helicopter was manufactured in 1979 in the US under the requirements of the US Federal Aviation Administration (FAA), Federal Aviation Regulations. FAA Technical Standard Order (TSO)-C22g (amended 1993) outlined minimum performance standards for aircraft seat belts when new. TSO-C114 (initial issue 1987) outlined minimum performance standards for aircraft torso restraints (shoulder harnesses) when new. Prior to 1987, there were no requirements for shoulder harnesses. Only TSO-C22 was in effect when the occurrence helicopter was manufactured.

At the time of the occurrence, there were no requirements to confirm compliance to applicable design standards of shoulder or seat belt harnesses while in service, or to specifically identify shoulder harnesses.

An Aero Commander Division 500-S (Shrike) had departed runway 35 at Essendon aerodrome. The pilot had been issued a clearance to overfly Melbourne airport and then track to Fentons Hill Very High Frequency Omni-direction Radio Range navigation (VOR) beacon, 10 NM north of Melbourne, and to climb to 3,000 ft. A Boeing 767-336 (B767) was on final approach to runway 27 at Melbourne and passing 1,400 ft on descent, when the crew received a Traffic Alert and Collision Avoidance System (TCAS) traffic advisory (TA) with an aircraft 600 ft below. The TCAS then issued a resolution advisory (RA) indicating an aircraft 300 ft below. The B767 crew initiated a TCAS climb and conducted a go around in accordance with company operating procedures.

The clearance issued to the Shrike pilot was in accordance with an overhead Melbourne departure procedure. That procedure had been implemented to facilitate departures from either runway 26 or 35 at Essendon aerodrome when there were arrivals to runway 27 or 34 at Melbourne. A letter of agreement between Melbourne tower and terminal, and Essendon tower detailed the procedure, including coordination requirements and separation responsibilities. The procedure relied upon the application of either radar, visual, or procedural separation being applied by the Melbourne or Essendon Aerodrome Controller subject to a number of conditions. The procedure was limited to a few approved Essendon operators.

The Shrike pilot had planned a flight from Essendon to Shepparton, about 80 NM north-northwest of Melbourne. The pilot reported that he had selected the transponder code and switched the unit to "On" prior to departing. Once airborne, and after transferring to the Melbourne Aerodrome Control frequency, he was advised that the transponder was not operating. The pilot was sure that the indicator light on the transponder was operating. He recycled the transponder.

The B767 crew first saw the Shrike on their aircraft's TCAS as they passed 3,000 ft on final approach. After the RA, it disappeared from the TCAS as the B767 passed 2,000 ft on climb. The crew was subsequently vectored for a landing on runway 34 via a left base. During the go around, cabin crew in the B767 saw the Shrike pass below and make a right climbing turn.

After the B767 pilot reported going around, the Melbourne Aerodrome Controller instructed the Shrike pilot to turn right and to pass behind the B767. The Melbourne Aerodrome Controller was not required to issue the B767 crew with traffic information on the Shrike.

The Melbourne Aerodrome Controller was using visual separation procedures to separate the aircraft. Visual separation enabled controllers to provide less vertical or lateral displacement between the aircraft than what would be required using a radar or vertical separation standard. Aerodrome controllers regularly used visual separation procedures to separate aircraft in the vicinity of aerodromes.

The TCAS is an independent on-board collision avoidance system that continually surveys the airspace around an aircraft, seeking replies from other aircraft in the vicinity via their transponders. The system determines the range, relative bearing, and relative altitude of other aircraft and uses that information to predict flight paths. If a flight path is predicted to penetrate the collision area surrounding the TCAS fitted aircraft, the system informs the crew by visual and aural annunciations. Depending on the closure speed TCAS issued either a RA or a TA alert.

Analysis of recorded radar data during the investigation revealed an inconsistency in the altitude readout from the Shrike. As the B767 descended between 1,500 ft and 1,400 ft, the Shrike's altitude changed from 1,250 ft to 736 ft and then to 1,650 ft over a 35 second period. A second altitude inconsistency was recorded after the RA alert. The investigation did not establish the reason for the inconsistent altitude readout. The operator of the Shrike reported that transponders could require up to five minutes warm-up prior to operation.

The recorded radar data showed that, at the closest point of approach, the Shrike was about 1.5 NM to the south and 300 ft below the B767. That was just as the B767 commenced the go around. At about the same time, the track of the Shrike changed from north-westerly to northerly.

The Agusta/Bell 47G-2A1 helicopter departed from Maroochydore airport at about 1420 Eastern Standard Time (EST) on a solo navigation exercise. The pilot intended to track via Somerset Dam, Kenilworth, Nambour and return to Maroochydore under the Visual Flight Rules (VFR), with an expected enroute flight time of about 1.9 hours. A flight plan was not submitted to Airservices Australia by the pilot. However, a flight notification form was retained by the company for search and rescue (SAR) purposes. Shortly before take-off, the pilot was cleared by the Maroochydore Tower controller to track direct to Somerset Dam via The Big Pineapple initially at 1,500 ft above mean sea level (AMSL).

Air Traffic Services (ATS) primary radar intermittently tracked the helicopter at a position 7 NM northeast of the accident location about 40 minutes after departure. The primary "paint" ceased about that time and location. A witness reported seeing the helicopter near the northern side of Mount Archer at about 1515 EST and flying in a manner consistent with the pilot experiencing controllability difficulties. A subsequent aerial search located the wreckage at a position about 1 NM right of the direct track from Maroochydore to Somerset Dam and on the north-north-eastern slope of Mount Archer. The helicopter sustained severe impact damage. The pilot received fatal injuries.

Some notes containing pre-flight navigation planning calculations and small pieces of the perspex cockpit bubble were found several hundred metres before the accident site. The notes contained navigation calculations that did not take into account the forecast enroute winds. Personnel at the flight training school did not recall discussing at length the forecast weather conditions with the pilot and, in particular, they did not recall briefing the pilot about the forecast mountain waves prior to the navigation exercise. The personnel at the flight training school also reported that helicopter pilots had been flying throughout the day in the Maroochydore region without experiencing any controllability difficulties induced by the forecast and actual strong winds.

The ATSB investigation team did not attend the accident site but viewed video footage and police photographs of the wreckage. The video footage had been recorded by the search and rescue helicopter crew at the time the wreckage was located. Damage to the helicopter structure was extensive and the tail boom was severed. According to the search and rescue helicopter crew, the helicopter's emergency locator transmitter (ELT) did not activate. The pilot also carried a portable ELT but it was damaged during the impact and did not activate.

The pilot held a Student Pilot Licence and a Restricted Private Pilot (Aeroplane) Licence. At the time of the accident the pilot had accumulated a total of 72.5 flying hours in helicopters, including 21.5 hours on Bell 47G helicopters. The pilot's aeroplane flight time records were not available to the investigation.

At the time the accident report was compiled, the pilot toxicology and autopsy results were not available. Consequently, the investigation was unable to comment on whether the pilot's performance was adversely affected by any pre-existing physiological condition.

There were no known maintenance deficiencies and the helicopter was considered capable of normal flight prior to the accident.

A Bureau of Meteorology (BOM) area forecast, issued at 1338 EST on the day of the accident, indicated isolated severe turbulence and mountain waves below 9,000 ft. The BOM examination of the available data indicated that the wind between 1,000 ft and 5,000 ft above ground level (AGL) in the Mount Archer area was constant with height at about 250 degrees True in the range 25 to 30 kts. The surface wind speed was estimated to be around 15 to 20 kts with frequent gusts in the range 25 to 30 kts. The relative orientation of the ridge and wind direction were conducive to mountain waves and possible rotor effects (see Attachment A) to the northeast of Mount Archer. The helicopter impacted terrain on the north-north-eastern slope of Mount Archer. The search and rescue helicopter pilot's report of actual meteorological conditions in the vicinity of the accident site was consistent with the BOM forecast.

Initial video and photographic evidence indicated that the helicopter probably encountered severe turbulence from mountain waves or rotors in flight while approaching the lee of Mount Archer. The evidence suggested that the main rotor blades may have severed the tailboom approximately 1 m forward of the tail rotor assembly. This accident signature is consistent with excessive blade flapping. The evidence indicated that a divergence of the main rotor blade from its normal plane of rotation probably occurred as a result of severe turbulence generated by mountain wave or rotor activity, and a main rotor blade contact with the tailboom and cockpit area ensued, resulting in a loss of control of the helicopter.

It is also possible that the collective lever friction may have been overcome by the severe turbulence that caused the non-powered collective lever to suddenly drop. The collective lever drop would have induced a sudden nose down attitude and this may have caught the pilot by surprise. The pilot may have instinctively and rapidly applied aft cyclic to correct the aircraft's attitude. The rapid application of aft cyclic in this situation may have been sufficient to induce main rotor blade contact with the tailboom.

A further discussion of mountain wave phenomena is provided in Attachment A.

Shortly after landing at Perth and taxiing clear of the runway, the crew of the Metroliner observed smoke accumulating and increasing in intensity in the cockpit. The crew stopped the aircraft on the taxiway, shutdown the engines, notified air traffic services of the problem and commenced disembarkation of the aircraft. After the passengers had safely disembarked, the pilot in command re-entered the aircraft and observed that, with the engines stopped, the smoke had begun to dissipate from the cabin and cockpit.

The operator's maintenance investigation found that the right air cycle machine (ACM) had leaked oil into the air conditioning system, that had then entered the cabin as smoke and fumes. The ACM turbine had seized. The Chief Engineer reported that the company conducted a fleet wide analysis to see if a failure trend could be identified for the ACM units. They determined that the Metro fleet had used a total of ten ACM's since 1999, with six being used by the incident aircraft alone. The usage was evenly distributed between left and right installations of the units. The conclusion was that the air delivery system to the ACM's might have a partial blockage leading to the premature failures.