The pilot of a Cessna 210 Centurion was tasked to fly three passengers from Kalgoorlie WA to Rawlinna WA and return.

The aircraft departed Kalgoorlie at 0804 Western Standard Time for Rawlinna with the flight proceeding without incident. The trip fuel log showed that the pilot believed that the aircraft arrived in Rawlinna with approximately 106L remaining in the left tank and 130L remaining in the right tank. The aircraft was not refuelled at Rawlinna.

Two passengers watched the pilot prepare for the return journey from Rawlinna. They reported that the pilot appeared to do a walk around the aircraft and one passenger stated that although he saw the pilot `check things at the front, wingtips and tail', the pilot did not check the fuel tanks in the wings. At approximately 1250, the flight departed for Kalgoorlie. One of the passengers recalled that, shortly after reaching a cruise altitude of about 4,000ft, the pilot appeared to become agitated and was checking something on the floor between the seats. This concerned the passenger, but after a few minutes, the pilot settled down and the passenger assumed that whatever had been a concern, was resolved. The fuel selector is located on the floor between the two front seats.

One passenger with recollection of the remainder of the flight from Rawlinna, stated that it appeared routine up until the engine lost power while the aircraft was approaching Kalgoorlie. (Due to the serious nature of the head injuries sustained in the accident by all of the passengers, their recollections of the flight prior to the engine power loss were very fragmented.)

At approximately 1413, the pilot was heard to broadcast a distress call including the aircraft altitude of 2,000 ft above sea level and his intention to land on a road. During the landing attempt, the passenger in the right front seat observed a car appear in the landing path. The passenger reports of what occurred after the car appeared were consistent with the pilot attempting to climb the aircraft to avoid the car and subsequently losing control of the aircraft during the manoeuvre.

The driver of the car and his wife saw the aircraft pass silently overhead as it crossed the road in a southerly direction. When it impacted the ground, the car driver's wife said that it appeared to `really bury in' before it was obscured by a large cloud of dust.

The driver immediately called emergency services and then he and his wife attempted to render assistance to the occupants. The pilot was fatally injured while the passengers were seriously injured.

Wreckage information

The aircraft impacted the ground in a left wing low, nose-down attitude. Examination of the aircraft found the left and right fuel tanks intact, but the fuel system plumbing was disrupted by cabin distortion at the fuel tank selector valve under the floor. The fuel line to the firewall mounted filter strainer and engine was broken and the strainer was destroyed during the accident impact sequence. The forward door pillar had been severed on the right side of the aircraft by hydraulic cutters used during the rescue effort to free the trapped front seat passenger. The examination of the fuel tank selector revealed that the right fuel tank was selected at impact.

Fuel had poured on to the right front seat occupant during the rescue and had continued for a considerable amount of time after the accident. No fuel remained in the right tank when it was examined by the investigation team on site. The rescuers said that they had not observed fuel to leak from the left wing onto the ground at any time. The aircraft's left wing low attitude uncovered the engine fuel supply lines at the inboard end of the tank and, as a result prevented the remaining left tank contents escaping through the damaged connections to the fuel selector. Less than half a litre of clean fuel remained in the outboard section (lowest point) of the left tank compartment and was considered to approximate the unusable amount for the tank. A sample of the Avgas, which was normal green colour, was taken from the aircraft and inspected at the accident site. It was free of any water or particles in suspension and visible contaminants. The fuel uplift for the flight was from the Kalgoorlie aerodrome. This fuel supply was tested by the supplier and found to be within correct specification.

The left-wing vent line was also clear of the remaining contents and did not appear to have been capable of allowing the remaining contents to drain off through the left-wing tip vent due to the syphon effect. The fuel contractor's log showed that there were multiple deliveries from the same batch of fuel to other aircraft operating from Kalgoorlie airport coincident with the delivery to VH-LMX. The bureau found no reports of fuel related problems with any of these other aircraft.

The fuel system components were bench tested and found to be capable of normal operation within the manufacturer's parameters. The wreckage, engine and component examinations found no evidence of pre-existing mechanical defects with the aircraft or its systems, that would have prevented normal operation of the aircraft prior to the accident.

Fuel pump switch

The auxiliary fuel pump switch is a two-segment split rocker type mechanism. The right half was colour-coded yellow and the left half red. The yellow half was marked START, with the upper position as ON and was used for normal start and some minor vapour purging if required. It was usually selected OFF for normal flight. In the event of an engine driven fuel pump failure in cruise flight, the yellow switch selected to ON should have provided, through a micro-switch arrangement, sufficient fuel for normal engine operation. The red half of the switch was marked EMERG (emergency) with its upper position marked as HI. This red switch was used in the event of an engine driven fuel pump failure during take-off or high-power operation and also extreme vapour purging. When the auxiliary fuel pump switch was removed and examined the yellow segment was found in the ON position.

A fuel dipstick with graduated markings on it was found in the baggage compartment of the aircraft. It was marked C210M VH-WXC and had the following graduations: LEFT FULL, 140, 100, 60, 30 with identical graduations and the word RIGHT on the reverse side of the stick. A check of the type certificate data sheet revealed that the C210N (accident aircraft) was fitted with identical type and capacity fuel tanks to the C210M.

Emergency locator transmitter

The aircraft was fitted with an emergency locator transmitter that activated upon impact. The transmission was received and logged by the Australian search and rescue organisation (AUSSAR) for 2hrs 39 mins before local police disabled the transmitter.

Pilot information

The pilot held a valid Australian commercial pilot licence and command instrument rating. He held a valid Class 1 medical certificate and did not require vision correction while operating an aircraft. At the time of the accident the pilot had accrued a total of 1,087 hours flying experience with 317.5 hours on the Cessna 210. From interviews and postmortem results, no evidence was found that the pilot had any personal or medical problems that may have adversely impinged on his ability to conduct the flight.

Survival

The nose-down, left wing low attitude of the aircraft as it impacted the ground exposed the left front seat occupant (the pilot) to the full force of the impact.

The passengers sustained numerous serious injuries in the form of fractures to legs, upper bodies and heads as well as injuries to internal organs. The leg injuries probably occurred when the floor was forced in an upward direction during the impact sequence. The floor movement also released the anchor points for the front seats. The middle row right seat remained fixed to its mounts. The middle left seat remained fixed by its rear mounts and forward left mount but with the front right mount partially released. There were no upper body restraint systems fitted to the passenger seat row positions in the aircraft, nor were any required to be. The upper body and head injuries sustained by all occupants were probably due to upper torso flailing contact with interior structure and objects. The front seat positions were fitted with upper body restraints. The effectiveness of the front seat restraint systems was compromised by the loss of integrity of the seat to floor attachments. The rearward movement of the engine firewall during the impact sequence may also have reduced the front seat survival space between front seat occupants and control panel structures; which would have increased exposure to injury.

Weather

The weather forecast for the day was for fine conditions, but with thunderstorm activity expected in the Kalgoorlie area during the afternoon after the flight. Other pilots reported experiencing some heavy turbulence in the area during the day and the operator's Chief Pilot remarked it was, `the first really rough day of the season'. The passengers recalled that, for the portions of the flight that they could remember, there was some turbulence but remarked that it was not unusually rough.

Aircraft fuelling

The afternoon before the charter flight, the aircraft operator requested the fuel contractor to fill the aircraft tanks (capacity 160L in each of two tanks) `to the tabs', which equated to a fuel quantity of approximately 120L in each fuel tank. The fuel request form was normally faxed to the fuel depot during the afternoon, but as no request had been received by the time he was due to commence fuelling tasks, the fuel contractor obtained the request sheet by walking to the aircraft operator's office and retrieving the original. The contractor noted that the sheet had been amended by the use of white-out correction fluid and that the original request entered had been for full tanks. It could not be positively determined if the pilot had sighted this fuel quantity request sheet.

Company pre-flight briefing

Some months after the accident, a director of the company stated that he spoke to the pilot in the afternoon prior to the accident flight. This conversation covered the task briefing for the following day and included the fuel load as being `to the tabs'. If this was so, the weight and balance calculations made by the pilot for the flight, in which a `full fuel' quantity was used and showed that the aircraft was close to maximum take-off weight, did not reflect any knowledge that he had received the `fill to tabs' fuel information. The director could not confirm whether the pilot assimilated this information at the time he talked to him.

Aircraft service history

The aircraft had been maintained in accordance with the relevant Civil Aviation Regulations and Orders. The aircraft had a valid maintenance release at the time of the accident with no maintenance overdue. Because a fuel quantity system calibration was required by the Civil Aviation Safety Authority (CASA) every three years as part of an airworthiness directive (AD), a calibration had been carried out six months prior to the accident in accordance with the AD. The gauge calibration results recorded in the aircraft logbook were as follows:

Left 10/46, 20/83, 30/117, 40/167, F/169 (Gallons/Litres)
Right 10/38, 20/65, 30/100, 40/145, F/164 (Gallons/Litres)

The aircraft fuel gauges, calibrated in US Gallons, were within the required parameters but the quantities differed between the left and right tanks for a given scale marking. This was compensated for by having a calibration correction card fitted to the aircraft. The calibration recordings in the logbook did not include a value for E (empty). However, the calibration card fitted to the aircraft stated that for E indication on the gauge, the tanks were to be read as empty.

A review of the aircraft's history revealed that, when being operated by its previous owner on the east coast, it had been involved in a similar accident in 1995 when it was force landed due to engine power loss. The aircraft had also taken off with the fuel tanks filled `to the tabs', and on that occasion it was estimated that the pilot had operated the aircraft for approximately 1 hour and 40 minutes when the engine lost power. The left fuel tank was used for the entire flight and when examined at the accident site, it was found to be empty.

Flight trip log

A company trip fuel log for the flight was found at the accident site. This log was being used by the pilot to record flight times and fuel usage from each tank for the flight. It had the following annotations:

The trip fuel log noted that the fuel tanks contained 160L in each tank on departure from Kalgoorlie.

The take-off from Kalgoorlie had been conducted using fuel from the left tank. The trip fuel log indicated that the aircraft had consumed 54 litres from the left tank and 30 litres from the right tank during the flight to Rawlina. Additionally, the log indicated that the pilot elected to remain on the left tank for the taxi, pre-take-off checks, take-off and departure from Rawlinna thereby carrying out both take-offs using fuel from the left tank. The pilot recorded an initial use of 15L from the left tank on departure from Rawlinna, followed by 40L from the right. At 13:45 WST he changed the selection to the left tank. About 28 minutes later, the engine lost power.

Pilots Operating Handbook (POH)

The aircraft was fitted with a placard that provided information in the form of a checklist in the event of major fuel flow fluctuations and/or engine power surges. Additionally, the POH provided expanded procedures for inflight engine restarts and excessive fuel vapour in the fuel system. The POH also noted that if the propeller is windmilling, the engine will start automatically within a few seconds. If the propeller has stopped (possible at lower speeds), turn the ignition switch to START, advance the throttle slowly from idle, and (at higher altitudes) lean mixture from full rich.

The POH went on to indicate that with fuel quantities of less than a quarter tank, prolonged uncoordinated turns or slips should be avoided as it might uncover the fuel tank supply outlets and starve the engine of fuel.

Engine out glide distance

The MAYDAY transmission made by the pilot placed the aircraft at a height of 800 ft above ground level. This height, according to the Maximum Glide graph in the POH, equated to approximately 1.2 NM, or approximately one minute of glide time from the time at which the engine lost power to the impact point.

History of the flight

On 6 November 2001, as the Boeing 747-400 aircraft was approaching flight level 360 en-route from Sydney to Singapore, the flight crew observed a CABIN ALT AUTO message and an increase in cabin altitude. The crew carried out the non-normal checklist, which included manually closing the outflow valves and turning off one of the air conditioning packs. However, the cabin altitude continued to rise and could not be controlled. The pilot in command (PIC) decided to conduct an emergency descent. The flight crew donned their oxygen masks and manually deployed the passenger oxygen masks.

As the aircraft commenced descent, one of the flight crew noticed the PIC's primary flight display screen go blank, with its data transferring to the PIC's navigation display screen. At that point a number of messages momentarily flashed onto the centre, Engine Indicating and Crew Alerting System (EICAS) screen, before all the display screens that are referred to as integrated display units (IDUs) blanked. The crew continued the emergency descent using standby instruments for reference, levelling at 10,000ft. The IDU system circuit breakers (CBs) were checked with all CBs found to be in their normal configuration. Manual selection between alternate system controllers was made but the IDUs remained blank.

After the post decompression drill announcement was made to the cabin crew, the PIC was advised that one passenger had sustained an injury in the form of bleeding from the ear. The PIC was also advised that there appeared to be no oxygen flowing through any of the passenger cabin oxygen masks, however this did not seem to have had any ill effect on the passengers. After the PIC cycled the passenger oxygen switch, a momentary surge of oxygen through the passenger masks was observed.

With Melbourne Air Traffic Control Centre providing vectoring assistance and using the standby flight instrumentation, the flight crew returned the aircraft to Sydney. Due to the loss of the display screens monitoring information, dumping of excess fuel was not possible. Information regarding the position of the landing gear or flaps was also not available. On approach to Sydney, the flight crew requested that the tower controller visually confirm that the landing gear was down and after receiving that confirmation, the crew conducted an uneventful, but overweight landing.

An inspection of the aircraft by engineers revealed that a cabin pressure relief valve had operated, indicating that the cabin had been over-pressurised at some stage during the flight. After a number of system CBs were cycled, the flight deck display screens returned to normal operation. An engine ground run and system check was then carried out, but the inflight faults could not be reproduced. The primary components of the aircraft's pressurisation and flight deck display systems were removed for further testing.

Cabin crew survey

The Australian Transport Safety Bureau carried out a survey of the cabin crew, which revealed the following:

Some cabin crew were concerned about the lack of oxygen flow through their masks during the descent and opted to use the emergency bottled oxygen. A number of cabin crew were observed removing their mask and later stated that they "could feel the presence of air" in the cabin. Some cabin crew were moving about the cabin during the descent assisting passengers. The majority of the cabin crew described the cabin floor angle as being less steep than their emergency decompression training had led them to expect. There was no evidence that any passengers or cabin crew showed signs of suffering from the effects of decompression sickness.

The operator's decompression drill detailed in the non-normal procedures of the operations manual stated that "When there is a loss of cabin pressure and the cabin altitude exceeds 14,000 feet the oxygen masks will drop. The pre- recorded announcement (where fitted) will start playing automatically".

The cabin crew were then required to immediately "Put on a drop mask as quickly as possible" and "Sit down at nearest available seat and fasten seat belt". The procedure then stated that after the aircraft had levelled off, the cabin crew were to "transfer from drop mask to portable oxygen bottle and mask" and to "assist the passengers".

The procedures also contained supplementary information regarding the symptoms and "effects of decompression sickness". The manual stated that at 10,000 feet cabin altitude, the cabin crew and passengers could experience headaches and fatigue. At 14,000 feet the effect may cause sleepiness, headaches, dizziness, impaired vision, personality changes and cyanosis-bluing of fingernails.

Subsequent occurrences involving this aircraft

On 11 November 2001, the flight crew reported that during climb there were large erratic oscillations of both outflow valves, causing large changes in the cabin altitude. The flight crew reported discomfort to their ears and observed significant rates of change in cabin altitude. The system returned to normal operation when the cabin pressure controller (CPC) was manually selected to position B.

On 16 November 2001, during taxi to the terminal, the flight crew observed the advisory message OUTFLOW VALVE L indicating a failure of the left outflow valve. After a ground test of the CPC was carried out, the message disappeared. During the next flight the message again appeared and again was cleared on completion of a ground test of the CPC.

Subsequent fleet occurrence

On 24 January 2003, all six IDUs blanked on another of the operator's Boeing 747-400 aircraft during a flight from Singapore to Sydney, while at FL350. After discussion with the operator's maintenance control personnel, the flight crew were advised to cycle selected CBs. On reset of the CBs, all the IDUs returned to normal operation and the flight continued on to Sydney. The Civil Aviation Administration of Singapore (CAAS) in conjunction with the United States National Transportation Safety Board (NTSB) are investigating the occurrence.

Component testing

The IDUs and EIUs¹ removed after the 6 November flight were subjected to examination and testing by their manufacturers, under the supervision of the NTSB. One of the EIUs was found to have an internal IOP #1 card 'soft'² fault. This fault should not have led to the IDU failure during the incident flight. No faults were found with the IDUs.

Testing of the pressurisation system components following the initial occurrence did not reveal any faults. After the subsequent flights on 11 and 16 November, further testing was conducted, which revealed that the CPC that had been fitted after the 6 November flight had a faulty pressure sensor that was giving erratic signals. One of the system's relays also displayed evidence of failure. The remaining pressurisation components were considered to be serviceable.

Oxygen system

The aircraft was fitted with two separate oxygen systems; one dedicated flight crew system and one dedicated passenger system. The crew system provided a continuous supply of oxygen to each of the flight deck regulators. Removal of the oxygen mask from the stowage box initiated the flow of oxygen. The passenger system had both manual and automatic deployment. Automatic deployment activated when the cabin altitude reached the "equivalent of 13,250 to 14,250 feet", with manual deployment available at any cabin altitude. This was a free-flow oxygen system with oxygen flow being controlled through flow control units (FCU) located downstream of the oxygen cylinders. During the first few seconds of operation, a surge of oxygen was released to open the panels above the passenger seats, allowing the masks to fall within easy reach of the passengers. The quantity of oxygen supplied was then controlled by altitude compensation mechanisms in the FCUs. The higher the cabin altitude, the greater the flow. Chapter 35-21-00 of the operator's aircraft maintenance manual stated: "Passengers are not required to receive [supplemental] oxygen below 10,000 feet, except for medical reasons".

On-board recorders

Data retrieved from the aircraft's on-board recorders revealed the following:

6:47:22 The first officer's IDUs switched from right to left EIU control, at the same time the pressurisation/air-conditioning system data stopped recording correctly.
6:47:44 The CABIN ALT AUTO message was observed.
6:48:09 The right and left EIU's were recorded as inactive.
6:52:58 Highest cabin altitude was recorded at 8553 feet.
6:54:10 Cabin altitude recorded at 6033 feet.
6:54:15 Numerous systems stopped recording data correctly and the Centre EIU became inactive.

(Note: Times refer to Coordinated Universal Time)

[1] The electronic interface units that transfer data from the electronic flight instrument (EFIS) and engine indicating and crew alerting (EICAS) systems to the IDUs.

[2] A fault that is internally logged but does not result in a complete EIU shut down.

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.