On 11 October 2006, at approximately 1420 Central Standard Time, a Boeing Co 767-336 was departing from bay 3 at Darwin Airport, NT for Brisbane Airport, Qld. Just prior to taxi, an auxiliary power unit (APU) fire warning activated with associated indications. The crew carried out the APU FIRE checklist items and the APU fire warning message extinguished, and the aural APU fire warning ceased.

Company engineering and Aviation Rescue and Fire Fighting (ARFF) personnel performed an external visual inspection of the APU area and advised the crew that there were no signs of a fire from the APU. The aircraft was returned to the departure gate.

The aircraft was returned to service under the provision of the B767 minimum equipment list item applicable for the operation of the aircraft with an inoperative APU.

During overnight maintenance in Sydney, company engineering staff found the remnants of a significantly charred cloth rag located on top of the aircraft's APU.

A number of safety actions were carried out or proposed by the operator as a result of this incident, including:

• amendments to the maintenance documentation for clearance closure inspections
• action to reinforce the responsibility and importance of the clearance closure inspections and to remind maintenance staff of the company's 'Safety over Schedule' principles
• the review of the suitability of equipment to gain access to all areas of the APU compartment
• a review of relevant licensed aircraft maintenance engineer training.

In addition, as a result of this incident, the ARFF changed its procedures to include that, until an ARFF response was called to a 'STOP', either an aircraft engineer or ARFF member was required to inspect the relevant aircraft compartment or area where a fire had occurred, an aircraft's fire warning system had activated, or an onboard fire extinguisher had been activated.

On 19 October 2006, at about 0635 Eastern Standard Time the crew of a de Havilland Canada DHC 8-200 aircraft, registered VH-TQX, departed from Melbourne Airport, Vic on a scheduled flight to Wollongong NSW. At about 0645, as the aircraft was climbing through flight level 140, the pilot in command (PIC) detected smoke in the aircraft. Soon afterwards a smoke detector warning sounded in the aircraft toilet and the flight and cabin crew observed smoke haze. The flight crew reported the situation to air traffic control (ATC) then diverted the aircraft to Melbourne and carried out the appropriate recall and checklist actions. The aircraft landed in Melbourne on runway 16 at 0658. There were no reported passenger or crew injuries.

The manufacturer's examination of the engine showed that oil had leaked from several compressor bearings into the low-pressure compressor of the engine. The high temperature of the compressed air and the engine components caused the oil to vaporize, contaminating the air extracted from that engine section to the aircraft cabin. The manufacturer had previously issued three service bulletins recommending engine modifications pertinent to this occurrence. Compliance with the bulletins was optional. However, the operator had already modified about 90% of the affected engines in its fleet at the time of the incident. The operator has planned to modify the remaining engines at the next period of scheduled or unscheduled maintenance.

The crew's timely assessment and response to the in-flight emergency reduced the likelihood of an extended exposure to the fumes by the passengers and crew. Also, the initiation of an emergency phase by air traffic control ensured that appropriate services were available to assist the crew after the aircraft had landed.

The engine manufacturer has undertaken to update the Workscope Planning Guide for the PW 123D engine to improve its resistance to internal oil leakage.

On 24 September 2006, during a scheduled passenger service from Darwin, NT, to Denpasar, Indonesia, the left engine of a Boeing Co 737-400 series aircraft sustained a mechanical failure within the first-stage low-pressure turbine (LPT) section. After reducing the engine thrust to minimise vibration and further damage, the flight crew returned the aircraft to Darwin.

Following an analysis overseen by the Australian Transport Safety Bureau, the engine manufacturer found that it was likely that thermally induced microstructural creep damage had contributed to the blade failure and subsequent damage to the turbine stage. An examination of the engine maintenance and operating records did not reveal any instance/s of hot-starting or significant take-off exhaust-gas temperature exceedance that may have contributed to the premature failure.

A total of seven related LPT stage-one failures had been identified by the engine manufacturer, including two from the subject Australian operator. While work by the engine manufacturer to better understand the issue was continuing, a range of stage-1 LPT blade production batches were identified as possibly being predisposed to premature failure. The engine manufacturer has recommended that LPT blades from the identified batches be removed from service and quarantined at the next maintenance opportunity, pending their further investigation and assessment of the issue.

On 19 September 2006, at approximately 1630 Eastern Standard Time, the pilot of a Boeing Stearman, registered N-73410, experienced a control problem while taxiing. The pilot reported that while conducting engine and power checks the aircraft inadvertently became airborne after hitting a bump on the airstrip that coincided with a gust of wind. He decided to continue with the take-off intending to complete a circuit and return the aircraft to the airstrip. The pilot reported that after banking to the left, he lost aileron control and the aircraft impacted the ground, flipped over and came to rest in an inverted position. The passenger received minor injuries and the pilot was uninjured. The aircraft was substantially damaged.

The pilot stated that prior to the accident he had engaged the flight controls lock on the aircraft while it was stationary on the airstrip. He reported that during the taxi runs he discovered that the flight controls lock was still engaged so he unlocked it. He subsequently believes that this action was unsuccessful and was why he was unable to control the aircraft during the take-off.

Five witnesses, who had earlier in the day assisted the pilot to move furniture, reported that they understood from the pilot that if the weather conditions were suitable, three of them would get a flight in the Stearman. The aircraft did not have a current maintenance release and was not airworthy.

The investigation was unable to reconcile the discrepancies between the pilot and witness reports.

The crew of a SAAB SF340B reported that shortly after take-off from Sydney Airport, NSW, they observed a zero reading on the left torque gauge and advised air traffic control that they were returning to land. During the approach, the crew made a PAN broadcast and advised that the left engine had been shut down. After landing the crew reported that they experienced airframe vibration and suspected a tyre had blown on landing. An inspection by emergency services personnel did not find any damage to the tyres and the crew taxied the aircraft to the terminal apron.

An examination of the aircraft systems could not find any reason for the zero reading on the left torque gauge, but the left digital engine control unit was replaced. A review of the crew's actions after they observed the loss of torque indication on the left torque gauge, found that they had selected the 'auto coarsen' switch to ON, prior to landing. That was contrary to directions in the flight crew operations manual that required the switch to be selected OFF when torque gauge indications read zero or were erratic. Consequently, the left propeller blades were automatically coarsened, effectively feathering the left propeller and resulted in an asymmetric landing.

The operator issued a notice to its aircrew reminding them of the requirement in the flight crew operations manual to not select 'auto coarsen' in these circumstances.

On 18 September 2006, at 1417 Eastern Standard Time, a Boeing Co 777-2H6 aircraft, registered 9M-MRM, departed Brisbane Airport, Qld for Kuala Lumpur, Malaysia. The flight crew reported that, at approximately 1422, when the aircraft was 74 kms west-north-west of Brisbane Airport and climbing through 10,300 ft, they felt a 'sudden jerk' followed by an Engine Indication and Crew Alerting System message 'ENG FAIL R'. The crew informed Brisbane Air Traffic Control of the right engine failure and performed the relevant checklist items to successfully restart the right engine.

After dumping fuel to reduce the landing weight, the crew returned the aircraft to Brisbane Airport. The company's ground handling agent's engineering personnel replaced the right engine Fuel Metering Unit (FMU) and the aircraft was returned to service.

The investigation found that there had been a loss of damping fluid in the turbine overspeed servo valve, adversely affecting the operation of the servo valve. As a result, the turbine overspeed servo valve became de-latched, and the engine shut down in flight.

A number of safety actions were carried out as a result of this incident, including by the:

• manufacturer of the turbine overspeed servo valve, who will check the servo valve when the units are returned for overhaul; and
• manufacturer of the FMU, who mandated a check of the torque setting of the turbine overspeed servo valve retaining bolts when the units are returned to their repair bases.

In addition, the engine manufacturer:

• is investigating the feasibility of the development of a test to confirm the serviceability of the turbine overspeed servo valve damping fluid in installed engines; and
• has published non-Mod Service Bulletin NMSB73-F408. That bulletin recommended the on-wing torque inspection of the turbine overspeed servo valve bolts in all installed engines or engines in overhaul shops where the life of the FMU is greater than 5,000 hours.

On 16 September 2006 at 0038 Western Standard Time, an Airbus Industrie A330 landed on runway 21 at Perth Airport in weather conditions that were below the applicable landing minima. The aircraft, registered VH-QPJ, was being operated in accordance with the instrument flight rules (IFR) on a scheduled passenger flight from Singapore to Perth, WA.

Before departure from Singapore, the aerodrome forecast (TAF) for Perth Airport predicted a 30% probability of fog after 0200. The aircraft was due at Perth at 0020 so in accordance with the operator's fuel policy; fuel was not specifically carried for a diversion from the destination to an alternate aerodrome. While the aircraft was in cruise, the TAF was revised to forecast fog from 2400, but the trend type forecasts (TTF) which superseded the TAF trended fog from 0030.

At about 2350, when the flight crew commenced descent, the aircraft passed the point where it had the fuel to divert to Learmonth, WA. About 10 minutes later, the TTF was amended to forecast fog to occur before the aircraft's arrival time. The fog occurred at about 0015. The crew attempted two Instrument Landing System (ILS) approaches before they used auto land to land on runway 21 in weather conditions that were below the prescribed landing minima for the ILS

The ILS at Perth (and other Australian airports) was approved to the Category I standard that did not allow landings where the visibility was less than 800 m. The Perth runway 21 ILS glide path critical area was not fully protected from multipath effects during low visibility operations.

Perth and Learmonth were the only aerodromes in Western Australia that could be classified as suitable for the A330, and Learmonth was 599 NM (1,110 km) from Perth.

As a result of this occurrence, the operator implemented an interim flight planning fuel policy specifically for Perth.

On 7 September 2006, a Boeing 717-200 aircraft, registered VH-NXI, was being operated on a scheduled service from Perth to Port Hedland, WA. Approximately 10 minutes after takeoff, the crew became aware that both the pilot in command's and copilot's computed airspeed displays had become erratic. The pilot in command's computed airspeed rapidly dropped, while the copilot's airspeed gradually increased. During the event, the pilot in command's displayed airspeed dropped as low as 115 kts, while the copilot's computed airspeed reached a maximum of 348 kts. Both the stall warning and overspeed warning sounded. The crew assessed the accuracy of the Integrated Standby Instrument System (ISIS) and used it for air data information.

The crew carried out the non-normal checklist from the Quick Reference Handbook. As part of the checklist, the crew cycled the air data heat switch. Approximately 15 minutes after the first signs of irregularities, both the pilot in command's and copilot's airspeed displays returned to normal and both airspeeds matched. The aircraft returned to Perth and conducted a normal approach and landing.

Analysis of the recorded data indicated that both the pilot in command's and copilot's pitot probes had iced up, which resulted in erratic airspeed indications and erroneous altitude and Mach numbers. The accuracy of the ISIS could not be determined from the recorded data.

The air data heat switch was removed from the aircraft and examined by the switch manufacturer. The switch manufacturer concluded that the latching mechanism in the switch was damaged, when the lamp capsule was forcibly opened while the switch was in the latched position.

It is possible that a piece of the broken latching mechanism jammed the switch in the OFF position, which resulted in no heat being supplied to the air data sensors, including the pitot probes.

Preliminary report released 2 November 2006

The pilot with four passengers on board, was conducting a private flight within the station property. The aircraft was later discovered destroyed after it had impacted the ground. Two of the passengers were fatally injured.

On 6 September 2006, a Boeing Co 717-200 (717) aircraft, registered VH-NXI, departed Perth, WA on a scheduled passenger service to Karratha. Approximately 100 NM (185 km) from Karratha, there was an automated thrust reduction, and the aircraft commenced the descent into Karratha.

Shortly after leaving the top of descent, the flight crew observed that the right engine had failed. During the completion of the relevant non-normal checklist items, the crew noticed that the main fuel switch for the right engine was selected to OFF. The engine failure checklist was carried out and a successful restart made as the aircraft continued to Karratha.

An examination of the throttle module and main fuel switches by the aircraft operator found no fault with their operation.

As a result of this incident, the aircraft operator issued a Safety Alert to all of its 717 operating crew advising of the possibility of selecting the aircraft's main fuel switches to ON without their correctly engaging the locking detent. That alert also warned flight crew of the possibility of inadvertent in-flight selection of the switches to OFF by catching wristbands or long sleeve shirt cuffs. In addition, flight crew were advised to not pass technical manuals or other similar items across the throttle quadrant in the vicinity of the main fuel switches.

The operator is evaluating the possible fitment of a physical guard to protect the main fuel switches against their inadvertent unlock from the ON position.