The pilot of the Schweitzer 269CB helicopter reported that during cruise on a repositioning ferry flight, the helicopter's engine misfired and then stopped completely so he completed a power off autorotation to a nearby dam wall. The pilot, the sole occupant, received no injuries and the helicopter was not damaged.

Troubleshooting by maintenance personnel isolated the problem to the engine's carburettor. The carburettor was replaced and the engine test run. No other anomalies were noted and the helicopter was flown back to the maintenance base.

A technical disassembly of the Precision Airmotive carburettor, model HA-6, part number 10-6030, serial number 75060303 was initiated. The examination included fuel flow level checks. During the checks, the throttle linkage was exercised through its full range from idle to full power. Throttle operation was smooth and unhindered. Several rapid accelerations were then carried out to observe the operation of the accelerator pump. No fuel was observed to flow from the accelerator pump discharge tube, positioned in the carburettor venturi, during these tests. Further examination revealed that the accelerator pump plunger mechanism was disconnected at the upper circlip attachment point on the plunger.

In addition, the accelerator pump/economiser linkages were found to have severe wear on the cam lobe face corresponding to the full throttle position and on the linkage plate that the camshaft lobe acted upon. The linkage plate also had severe wear on the cam lobe-mating surface and on the opposite non-cam lobe contact surface. That indicated that the plate had been reversed at some point during its operational life.

Carburettor background

At the time of the occurrence, the carburettor had accumulated 1,668.2 hours time in service (TIS). The carburettor had been removed from the engine at 1,154.7 hours TIS for a discrepancy reported as suspected low engine power. The repair documentation noted an air-metering pin adjustment defect. Following readjustment, the carburettor was bench tested and returned to service.

At 794.4 hours TIS, the carburettor had been removed from the engine, for a discrepancy reported as leaking fuel when in the full lean/cut-off position. The repair documentation noted that a new float needle and seat were fitted. The carburettor was bench tested and returned to service.

The Beechcraft Super King Air 200 aircraft had arrived at Timber Creek NT to conduct an aeromedical flight to Tindal NT. The aircraft had the pilot, a flight nurse and one patient on board.

While on the ground at Timber Creek, the environment had been oppressively hot. Both the pilot and flight nurse reported feeling extremely uncomfortable and had both been perspiring profusely. The aircraft's air conditioning system was not operating properly and had offered little respite from the conditions, either on the ground or in the air. Due to the type of injuries that the patient had suffered, the flight nurse had requested that the pilot maintain "sea level" cabin pressure for the return flight. The flight nurse had also fitted an oxygen mask to the patient. The pilot recalled setting the pressurisation controls to suit the request from the flight nurse.

On the inbound flight, the pilot had been advised by Air Traffic Control to expect a non-standard clearance for the return flight due to RAAF aircraft activity in the area.

Following take-off, at about 2,000 ft, the air traffic controller instructed the pilot to intercept the 173 radial at 120 NM from Tindal, and then to track along that radial to Tindal. That had been necessary to avoid the now active Military restricted area R248(B). The pilot reported that he had then become occupied with re-programming the aircraft's Global Positioning System (GPS). During the climb to the cleared level, Flight Level 130, the pilot reported that he believed that he had actioned all the required checklist items.

As the aircraft climbed through FL125, the flight nurse noticed that the passenger oxygen masks had deployed and conveyed that fact to the pilot. The pilot was unaware of the deployment and had immediately turned around to assess the situation. When he turned his attention back to the instrument panel, the pilot noticed that the cabin ALT WARN caption positioned on the glare-shield mounted Master Warning panel was illuminated. Both Master Warning captions were also flashing. The pilot then contacted Air Traffic Control and received a clearance for an immediate descent to 10,000 ft.

The flight nurse donned the nearest available passenger oxygen mask and re-checked the flow of supplemental oxygen to the oxygen mask worn by the patient. The pilot did not don an oxygen mask during the incident.

Once established at 10,000 ft, the pilot discovered that both the left and right bleed air OFF green advisory annunciators were illuminated, and that both bleed air switches were in the ENVIR OFF position. In that position, no bleed air was available for aircraft pressurisation. The pilot had then selected both bleed air switches to OPEN, and restored normal pressurisation.

The flight was then continued to Tindal at the lower altitude.

The pilot was appropriately licensed for the flight and had approximately 3,600 hours total flying experience, of which 90 hours were on King Air 200 aircraft, with about 50 hours as pilot in command.

The Operator's Pre-Take Off Procedures required the bleed air to be selected to ON (OPEN). When the three-position bleed air switches were selected to EVIR OFF or INST & ENVIR OFF, a green advisory light L or R BLEED AIR OFF annunciator was illuminated. The pilot reported that he could not remember having selected the switches to OPEN prior to take-off.

The pilot indicated that he had not noticed the green L or R BLEED AIR OFF annunciators during the climb. He reported that that was partly due to him being accustomed to seeing the green L and R AUTOFEATHER advisory captions illuminated on the lower centre instrument console during the take-off. The pilot was also unsure if the ALT WARN and Master Warning caption had been illuminated prior to him being aware of the passenger oxygen mask deployment.

The operator's After Take Off Procedure included a requirement to turn the Auto Feather "OFF not below 1500ft". The pilot reported that the task was often left until after the transition altitude, when the cockpit routine was "less busy". That meant that the green L or R AUTOFEATHER advisory captions would remain illuminated until the checklist was completed, sometimes up to FL 150. The operator's After Take Off Procedure included a note, which indicated that the checklist only needed to be completed when workload permitted.

The After Take Off Procedures also required the pressurisation to be checked. That task involved the pilot checking that the bleed air valve switches were OPEN (up) position. The pressurisation gauges were also to be checked to ensure that the aircraft was pressurising normally. The Transition Altitude Procedures stated that "pressurisation checks should be made at least every 10,000 ft during climb and again when stabilised in the cruise".

The operator's Phase One Emergency Procedures, for a loss of pressurisation with the cabin altitude above 10,000 ft, directed the pilot to don the crew oxygen mask. The pilot reported that he had not performed that task as he had quickly descended the aircraft to 10,000 ft.

The aircraft's air conditioning system had a history of operating problems, with six instances of maintenance recorded since January 2001. The flight nurse said that the air conditioning system had been malfunctioning for some time prior to the incident, and that the aircraft had been to Darwin several times for repair. The crew also indicated that on the flight from Tindal to Timber Creek the interior of the aircraft had been hotter than normal and that it had not operated at all on the incident flight.

The maintenance record entry following the flight indicated that the air conditioning system high-pressure switch had tripped. Maintenance troubleshooting found that the system gas pressure was incorrect, and the pressure had been subsequently adjusted.

The aircraft's cabin altitude warning system and the passenger emergency oxygen mask system were both designed to operate at a cabin pressure altitude of 12,500 ft. The two systems were separate and operated in response to electrical signals received from individual pressure switches. The cabin altitude warning system illuminated both the glare-shield mounted flashing red Master Warning annunciators and the red ALT WARN annunciators on the warning annunciator panel. The passenger emergency oxygen mask deployment system activated a green PASS OXY ON annunciator on the aircraft's Caution/Advisory panel.

The operator had installed an aural warning device that operated in conjunction with the cabin altitude warning annunciator, into this aircraft on the 30 November 2000. That device had been installed under a CAR 35 engineering approval. On the 23 February 2001, following an instruction from the Civil Aviation Safety Authority that the device had to be removed because it had not been manufactured in accordance with current legislation, the unit was removed from the aircraft.

The sun's azimuth was 282 degrees true, which meant that the sun's light came from behind and to the left of the aircraft. The sunlight glare from the West may have occluded the red master warning and the altitude alert on the pilot's side and centre of the instrument panel glareshield.

A text by Thomas Turner, titled "Checklists & Compliance", written on the use of checklists in aircraft operations, pointed out the problem with operating equipment such as global positioning system units in "altitude critical areas". Such areas were defined as within 1,000 ft of the ground or within 1,000 ft of levelling off from a climb or descent. The textbook went on to say "Concentrate on what it takes to establish the new level flight attitude, trim the aircraft for level flight, and check to make sure critical items are complete before turning to less crucial tasks".

A Civil Aviation Safety Authority booklet "The Global Positioning System" stated that:

"GPS may relieve the mental task of computing the aircraft's position and speed in relation to maps of the terrain, but it may increase the workload of programming and accessing the desired information from the machine and interpreting it.

"Piloting an aircraft requires continuous monitoring and reacting to events both inside and outside the cockpit.

"The amount of information we can deal with at any one time is limited....

"Don't allow the operation of the GPS to interfere with your primary task of flying the aircraft".

Prior to descent into Coolangatta, the crew of the Boeing 717 aircraft noticed a low right hydraulic quantity warning. After following the abnormal checklist and turning off the right hydraulic system, the pilot in command decided that, due to the rudder reverting to manual mode and the loss of operation of two ground spoilers, he would divert the aircraft to Brisbane where a longer runway was available. After advising Brisbane Air Traffic Control of the hydraulic failure, and that a faster than normal landing would be carried out, the airport's emergency services were placed on standby.

With the right hydraulic system turned to the OFF position, the aircraft's landing gear had to be manually lowered using the emergency gear extension lever. That operation did not close the main landing gear doors after the landing gear was extended. In accordance with the abnormal check list an attempt to close the doors was conducted by the crew after receiving the green down and locked indication for the landing gear. However, following the selection of the right hydraulic system to ON, a rapid drop in hydraulic fluid quantity was noticed so the OFF position was immediately re-selected before the doors had closed.

As the aircraft touched down, the main landing gear doors contacted the runway surface. Although the doors were fitted with non-sparking polyurethane rest bumpers, the runway centerline lights were contacted creating sparks that were observed by ground personnel. The aircraft was then brought to a halt on the high speed taxiway where an engineer was requested to manually close the main landing gear doors. Following closure of the doors the aircraft taxied to the terminal. The abnormal checklist stated that the aircraft is not to be taxied but may be towed after landing gear safety pins had been fitted and main landing gear doors closed.

An inspection of the aircraft by the operator revealed that a hydraulic pipe from the right engine driven hydraulic pump had failed at its brazed fitting, resulting in the loss of hydraulic fluid from the right hydraulic system. As this was not the first time that the operator had experienced such a failure of hydraulic pipes, the aircraft manufacturer was contacted. It was determined that the pipes in the area of the rear fuselage were being subjected to vibration from the engine driven hydraulic pump, which in some cases resulted in the fracturing of the pipe fittings.

While at 8,000 ft on descent for a landing at Melbourne Airport, the crew of the Fairchild Industries Inc SA227-AC, Metro aircraft heard a loud bang from the left engine together with associated aircraft yaw. The pilot carried out the initial engine failure actions, noting that the left engine torque had dropped to 15%. The flight continued to Melbourne with the engine still operating. The pilot then carried out an uneventful approach and landing, shutting down the engine at the end of the landing roll.

An examination of the left engine, commissioned by the operator, found evidence of heat and burn damage in the turbine assembly, with one of the first-stage turbine nozzle vanes almost completely burnt away. A first-stage turbine blade had also detached from the first-stage turbine rotor assembly. That blade had then passed through the subsequent stages of the turbine section, extensively damaging the turbine components. The engine failure was fully contained.

The first-stage turbine blades and first-stage turbine nozzle assembly were forwarded to the ATSB's Technical Analysis section laboratory for further investigation. That investigation (see ATSB Technical Analysis Report, BE/200200024) found that many of the nozzle vanes had developed thermal fatigue cracking in the leading edges during operation. That cracking had led to the perforation of the internal cooling air galleries in one vane, resulting in the partial interruption to the flow of cooling air through it. The interrupted flow of air through the vane had resulted in its overheating and complete burn through. The burnt-through nozzle vane had subsequently disturbed the downstream flow of the combustion gas through the turbine and excited a once-per-revolution vibration of the first-stage turbine blades. The investigation concluded that the vibration contributed to development of fatigue cracking within the root of a single blade from the stage-one turbine, and the subsequent liberation of the cracked blade from the turbine rotor.

Maintenance issues

The engine was last overhauled on 20 January 1997 and had completed 2,327.9 engine hours and 2,473 cycles since that time. The operator's system of maintenance required that the turbine section be inspected at 3,500 hr intervals. To accomplish that inspection, the turbine section had to be removed from the engine. The forward end of the turbine was not normally examined outside of those inspection intervals.

During the 20 January 1997 overhaul, all 36 first-stage turbine blades were replaced with new items of part number 3108125-1. The 12 first-stage turbine nozzle segments were also replaced.

The 12 first-stage turbine nozzle segments were divided into two part number groups. Eight were of part number 3103820-4. Two of the ` - 4' segments were new, with the six remaining segments having been overhauled in January 1997. The remaining four nozzle segments were of part number 3103820-2 and included the failed segment. All of the ` - 2' segments had been overhauled in December 1996.

During the overhaul process the manufacturer required that the turbine nozzle segments be inspected for missing sections of vane material.

A 'Caution' note in the engine manufacturer's maintenance manual stated:

'CAUTION: MISSING MATERIAL (BURN THROUGH) AT VANE LEADING OR TRAILING
EDGE RESULTS IN IMPULSE (CYCLIC) LOADING OF BLADES.'

The engine manufacturer indicated that similar turbine blade failures had been observed in engines with clogged or streaking fuel burner nozzles.

The manufacturer further indicated that there was a `Hot Gas Path Inspection' borescope inspection procedure that could be carried out to determine the in-service wear of the first-stage turbine nozzle and first-stage turbine rotor. That inspection could be accomplished through the fuel nozzle body ports in the engine's combustion case, and was recommended if `fuel nozzle induced distress is suspected'. Fuel nozzle distress could be indicated to a pilot by an engine running hotter than normal or had reduced performance. The fuel nozzles were required to be serviced every 450 engine hours as part of the operator's system of maintenance. That maintenance had been carried out 197 hours prior to the incident.

Post-incident examination of the nozzles in the engine, carried out on behalf of the operator, did not reveal any nozzle clogging.

The operator carried out in-flight engine trend monitoring. That monitoring did not reveal any ongoing problem with the operation of the engine.

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.