A Boeing 767-338ER (B767) was maintaining flight level (FL) 370 and had been assigned FL330 to maintain separation with a Cessna Citation 500 (C500), maintaining FL310, that was crossing the track of the B767. The controller entered FL330 into The Australian Advanced Air Traffic System (TAAATS). He subsequently, and unintentionally, assigned the crew of the B767 descent to FL300. The controller received a cleared level adherence monitor alarm (CLAM) when the B767 descended through FL326. Vertical separation between the B767 and the C500 reduced to 700 ft, and horizontal separation reduced to 3.4 NM. The required separation standard was 2,000 ft or 5 NM. There was an infringement of separation standards.

The controller had initially cleared the crew of the B767 to descend from FL370 to FL330. The descent was to be commenced at the discretion of the crew. He then entered FL330 into TAAATS as the new cleared flight level (CFL). The controller reported that he had made the necessary TAAATS entries on receipt of the correct level read back from the crew of the B767. There were no subsequent TAAATS entries required in relation to FL330 being assigned to the crew of the B767.

The B767 crew reported leaving FL370 approximately five minutes after they had been assigned FL330. The controller reported that he had intended to confirm FL330 as the cleared flight level with the B767 crew at that time, but he unintentionally assigned FL300. The crew of the B767 read-back FL300 and continued descent through FL330. The controller did not detect from the read back that he had assigned an incorrect flight level. There were no subsequent opportunities for the controller to realise the error until the CLAM alarm from TAAATS.

The controller indicated that he considered his workload at the time of the occurrence to be light. He was responsible for two sectors of airspace but he did not believe that the increase in workload caused by the combination of the two sectors contributed to the error. The replay of the voice recording indicated that the controller had up to ten aircraft under his control at the time of the occurrence. Three of those aircraft had requested a shorter route. The controller accommodated the requests because some of those aircraft were involved in bush fire fighting operations. When the routes for those aircraft were amended, the associated flight data record in TAAATS also needed to be amended and the changes needed to be coordinated with adjacent sectors. The controller did not believe the extra workload generated by those tasks contributed to the occurrence.

The controller was also the team leader on the shift. He reported that there were no distracting team leader issues at the time of the occurrence. The controller did not believe he was fatigued.

There were five persons on board the Cessna 185 floatplane when the pilot taxied for a charter flight from the wharf at Strahan, Tas. The pilot steered the aircraft out of the cove into more open water to position the aircraft for take-off into the prevailing northerly wind.

The pilot reported that the aircraft had travelled approximately 1 km, and was at the start of the planned take-off run, when he assessed the water state as being marginal for the aircraft. He then began steering the floatplane back towards the wharf when a catamaran cruise boat, travelling in the opposite direction, passed on the left. Waves generated by the accelerating catamaran prompted the pilot to steer the floatplane left to cross the bow-wave head on. After negotiating the wake, the pilot resumed course to the wharf. The pilot then became concerned about the buoyancy of the right float and broadcast his concerns. He increased power and applied left aileron and aft elevator to counter the increasing list to the right but the aircraft nosed over and came to rest inverted.

The pilot and two passengers were able to evacuate quickly from the submerged cabin and were followed a short time later by another passenger. At that time, the pilot was diving to assist the remaining passenger, who eventually surfaced unaided. Three life jackets floating in the water nearby were retrieved by the pilot and were donned by passengers. The pilot and passengers were rescued a short time later by a nearby boat and another floatplane.

The pilot had been tasked to use a floatplane that was positioned in a hangar near the water. While the preflight inspection in the hangar had revealed only a small amount of water in the two float lockers, the pilot intended to pump out the other six float compartments on each float when the floatplane was tied up at the wharf. He was aware that the floats had been prone to taking on water and that pumping out the floats prior to his previous flights in the aircraft had removed substantial amounts of water. It was also standard operating procedure for the operator's pilots to pump out the float compartments as part of their daily preflight inspection. However, the floats were not pumped out, and the aircraft departed the wharf with an unknown amount of water in the floats.

While the pilot could recall being subject to time pressure after the aircraft was positioned at the wharf, he was not able to clearly remember the specific circumstances that contributed to the situation. The pilot reported that he had arrived at work at 0815 Eastern Standard Summer Time and started his duty period at 0830 for a planned 0900 departure.

The pilot stated that, soon after departure from the wharf, the aircraft `felt odd'. He then radioed a colleague located in the wharf office, who indicated that the right wing was slightly low. At the time the pilot attributed the aircraft attitude to fuel imbalance, passenger loading and the wind effect. Before entering the more open water, the pilot had momentarily turned the aircraft into wind and was satisfied with the level of the wings and water handling. While the pilot attempted to observe the performance of the right float a number of times, he found it difficult to see the float from the left side of the aircraft. During the outbound taxi, the front passenger had advised the pilot that the right float was low in the water and had water breaking over it. The pilot reported that he only became concerned about the ability of the floatplane to stay afloat after the encounter with the wake of the cruise boat. At that stage he considered that beaching the floatplane was impractical due to the unsuitability of the adjacent coastline.

The front passenger later stated that the right float was basically submerged by the time the wake from the catamaran had been negotiated. He also stated that there were two round holes of approximately 30 mm diameter on the top of the right float that allowed water to enter the float. This was likely to have been the access holes for the smaller diameter bilge tubes. The access holes are normally sealed with a removable bung. The pilot stated that one or two bilge tubes were missing from their holes in the right float. Following discussions with the pilot and other company personnel, the investigation was unable to determine the point in time when the right float bungs became separated from the floats.

The passengers stated that the operator's personnel had briefed them on life jacket use when they were checked in for the flight. The pilot had also given the passengers a pre-departure briefing that included the location of the life jackets. A life jacket was stowed under each of the seats.

Civil Aviation Order (CAO) Section 20.11, Parts 5.1.4 and 5.1.5 describe the requirements for the equipping of floatplanes with life jackets. Part 5.1.8 describes the requirements for the wearing of those life jackets and states, in part: `However, occupants need not wear life jackets when the aircraft is taking-off or landing at a aerodrome in accordance with a normal navigational procedure for departing from or arriving at that aerodrome, and occupants of aeroplanes need not wear life jackets during flight above 2000 feet above the water.' Aerodrome is defined in Aeronautical Information Publication Australia, Amendment 33, as `A defined area of land or water (including any buildings, installations and equipment) intended to be used either wholly or in part for the arrival, departure and movement of aircraft.'

A fuel spill of approximately 100 litres occurred during refuelling of the South African registered Boeing 747-312 aircraft on the international terminal apron at Perth airport. Eighty minutes later, the Aviation Rescue Fire Fighting Services (RFFS) observed fuel venting from the right wing of the aircraft as it commenced a take-off roll on runway 21, for a flight to Johannesburg, South Africa.

The fuel spill at the terminal was due to the refuel valve in the number 4 reserve tank failing to shut off. The tank became overfilled because of a faulty quantity indicator at the refuelling station panel. Fuel overflowed from the reserve tank into the fuel tank vent system and then spilt onto the apron from a ram air scoop located near the wingtip. The tank vent system vented the fuel tanks to atmosphere by a series of tubes from the fuel tanks, to a surge tank located in the outboard section of each wing. The surge tank vented to atmosphere through a flame arrester and the ram air scoop.

The aircraft refuelling system included an overfill protection system whereby if 75 mm of fuel overflowed into the surge tank, a float switch operated, which closed all refuel valves. The overfill protection system could be disabled by pulling the appropriate circuit breaker in the main equipment centre within the lower forward fuselage.

During the period from 7 December to 30 December 2001, the Perth RFFS attended six other fuel spills ranging from 20 to 100 litres from aircraft used by the same operator. Those spills involved five B747 aircraft (including ZS-SAJ) and were due to the failure of the refuel valves to shut off during refuelling operations.

In 1998, the United States Federal Aviation Administration (FAA) issued an airworthiness directive, AD 98-20-40, that required the replacement of fuel quantity indication system (FQIS) electrical wiring outside of the fuel tanks and surge tank on older versions of the B747 aircraft. The modification was intended to prevent arcing of the FQIS wiring or probes due to electrical transients induced by electromagnetic interference or electrical short circuit conditions.

The five aircraft involved in the fuel spills at Perth airport had been fitted with a transient suppression device that was approved as an alternate means of compliance with the airworthiness directive. The device had caused problems with the FQIS, including incorrect calibration of the refuelling system that resulted in the aircraft being loaded with an incorrect amount of fuel or the fuel tanks being overfilled.

The spillage of fuel from the tank vent system during the eight occurrences indicated that the overfill protection system circuit breaker was pulled during the refuelling operation to work around the calibration problem. The work around enabled refuelling operations to continue and prevent any delay to the departure of the aircraft. If some fuel remained in the surge tank after completion of refuelling operations, it could vent to atmosphere from the ram air scoop during the take-off roll, as was observed on 17 December 2001.

Following the fuel spills, the operator carried out rectification work on the five aircraft, including the checking and changing of fuel system components, the replacement of FQIS wiring harnesses, and the re-calibration of the system. The operator also implemented the local safety actions listed below and no further fuel spills were reported.

The pilot of the Cessna 185 Floatplane, with five passengers on board, was making a water departure for a charter flight. The pilot positioned the floatplane for a take-off into a north easterly wind of 15 kts that was gusting to over 20 kts. The take-off path was over a sand spit, approximately 50 ft above the water level. To the north, and left of the take-off path, was a steep, rocky headland that rose to a height of approximately 300 ft above mean sea level.

The pilot reported that he had selected 20 degrees of flap and applied maximum power for take-off. The aircraft became airborne after a short run and the pilot climbed it at an indicated airspeed (IAS) of 70 kts. At about 200 ft the pilot reduced engine power to 25 inches of manifold pressure and 2,500 RPM. The pilot reported that just after he reduced power, the aircraft encountered turbulence and started to descend rapidly. He turned the aircraft left, away from the spit, with the intention of regaining altitude over the water before he attempted to cross the spit. However, the aircraft continued to descend, and the pilot decided to land straight ahead. The aircraft contacted the water and bounced, then ran aground on the beach and overturned.

The pilot reported that he exited through a window and instructed the passengers to evacuate quickly, as there was a possibility of fire. The passengers reported that they were entangled in their seat belts and had difficulty releasing the buckles. A small child was being held by a passenger and another passenger was temporarily restrained by clothing that became caught on the right control yoke.

The load chart for the flight showed that the aircraft was 31 kg below its maximum take-off weight. The pilot commenced the take-off with a take-off distance of approximately 1,100 m, which exceeded the minimum take-off distance of 1,000 m stipulated by the aircraft's flight manual. However, this take-off distance was less than the 1,300 m pilots were directed to use by the operator's Authorised Landing Area (ALA) register. The pilot reported that he had not used the full length available as previous take-offs that day, from the same point in lighter winds, had been uneventful. He considered that the increased headwind component would have improved the take-off performance and climb gradient of the aircraft.

The ALA register also stated that a north-easterly wind required a climb over the spit to avoid turbulence in the lee of the adjacent headland. Another warning in the operator's ALA survey report cautioned "Dumping will be encountered on the lee side of the headland especially in the north easterly winds".

A fact sheet on mountain wave turbulence that accompanied a recent ATSB report (Occurrence 200104092) involving mechanical turbulence stated, in part:

"Flowing air near the ground is forced up the windward side of any elevated barrier and then sinks down the leeward side. Air flowing at speeds greater than 20 kts produces seriously turbulent air and significant downdrafts on the leeward side."

That situation was referred to as "dumping" in the operator's ALA survey sheet. The pilot reported that he hadn't encountered severe "dumping" during any previous take-offs.

The fact sheet also stated, in part:

"In addition to generating turbulence that has demonstrated sufficient ferocity to significantly damage aircraft or lead to loss of aircraft control, the more prevailing danger to aircraft in the lower levels in Australia seems to be the effect on a aircraft's climb rate. General aviation aircraft rarely have performance capability sufficient to enable the pilot to overcome the effects of a severe downdraft generated by a mountain wave, or the turbulence or windshear generated by a rotor."

The Cessna 185 Pilot's Operating Handbook (POH) procedures for both normal take-off and short field take-off recommend that once clear of any obstacles, the pilot retract the wing flaps and select full throttle and 2,700 RPM. Operations manual data produced by the operator listed the climb power setting as 25 inches manifold pressure and 2,700 RPM, with a footnote that the information be used as a guide only and that the user refer to the POH and Flight Manual. The aircraft's flight manual did not provide guidance on take-off procedure or associated power settings. The climb power setting of 25 inches manifold pressure and 2,500 RPM, selected by the pilot when the aircraft reached approximately 200 ft, delivered only 81 per cent of the available power.

The pilot reported that he had been encouraged by the operator to reduce power as soon as possible after take-off as a noise reduction technique. The Chief Pilot stated that a power reduction early in the climb was demonstrated during training to reduce the noise impact and to reduce engine wear. The Chief Pilot also stated that, during training it was emphasised that power reductions should only be made when clear of obstacles and when terrain had been cleared. It was also stressed that when required, full power should be used, at the pilot's discretion.

The Boeing 737-33A aircraft, registered VH-CZQ, departed Townsville at 1805 EST on a scheduled passenger service to Brisbane. Soon after levelling at flight level (FL) 330, the flight crew observed that the master caution light, the cabin pressurisation auto-fail light and the pressurisation standby light had illuminated. The crew completed the non-normal procedure and, as cabin pressurisation was being maintained, they decided to continue the flight to Brisbane.

At about 1909, the flight crew experienced physiological sensations, which indicated that the flight deck was depressurising. The crew donned their oxygen masks and the copilot noticed that the cabin rate of climb indicator was displaying a rate of climb of 4,000 fpm. Shortly afterwards, as the cabin altitude climbed through 10,000 ft, the crew observed that the master caution light and passenger oxygen `on' light had illuminated and heard the cabin altitude warning horn. The flight crew completed the non-normal procedure for a rapid depressurisation and emergency descent and advised air traffic control that the aircraft had left the cruising level due to a depressurisation. The pilot in command advised the cabin crew on the public address system (PA) of the descent.

The cabin in-flight service had been completed and the four flight attendants were at the front of the aircraft when the oxygen masks dropped from overhead passenger service units (PSU) throughout the cabin. When the oxygen masks dropped, the cabin supervisor returned to his seat at the forward left entry door, donned an oxygen mask and removed the PA handset from its receptacle. Another flight attendant also returned to his crew seat at the forward left door and donned an oxygen mask. The two remaining flight attendants, standing at the front of the aircraft when the oxygen masks dropped, returned to their crew seats at the rear left entry door.

Some passengers were assisted by a flight attendant as she walked to the rear cabin. When the flight attendant reached the rear crew seat she found that the crew oxygen masks had not automatically deployed from the overhead stowage. She released the masks by activating the manual release on the overhead panel, and was seated just as the second flight attendant reached the crew seat.

The flight attendants reported that the floor angle during the emergency descent seemed no different than a normal descent and they did not notice any movement of cabin or galley items. One flight attendant reported that she did not feel in danger. Her ears were `popping', but there were no indications of depressurisation such as those taught in emergency procedures training. The flight attendants reported that they `weren't short of breath, felt [they] had time, there were no objects flying in the cabin or cabin misting'.

The flight data recorder information showed that at 09:08:55, while in cruise at FL330, the cabin altitude warning activated indicating that the cabin altitude had exceeded 10,000 ft. Thirty-six seconds later at 09:09:31, the emergency descent was initiated with the thrust levers being closed and the autopilot level change mode being selected. The pitch attitude then decreased from 3.2 degrees nose up to 4.4 degrees nose down and the aircraft began to descend at a rate of 4,600 feet per minute. At 09:11:01, the speedbrake was deployed as the aircraft descended through FL276 at a rate of 4,500 feet per minute, with a pitch attitude of 3.7 degrees nose down.

The maximum nose-down pitch attitude during the emergency descent was 4.4 degrees for a 6-second period as the aircraft descended through FL 285 at 5,000 feet per minute. By the time the aircraft reached FL199, the pitch attitude had reduced to 1.4 degrees nose down, with a rate of descent of 3,400 feet per minute. By way of comparison, the pitch attitude during a normal descent of a B737-300 series aircraft is about 2 degrees to 3 degrees nose down above FL260, reducing to about 1 degree nose down during the latter part of the descent.

When the aircraft levelled at 10,000 ft, the pilot in command advised the passengers by PA that oxygen masks would no longer be required, and instructed the cabin crew to commence follow-up actions. The cabin supervisor went to the flight deck to confirm instructions and advise the pilot in command of the conditions in the cabin. The flight attendants reported that, although all passengers were calm, three or four passengers needed reassurance, but additional oxygen was not required. The flight crew continued the flight to Brisbane at 10,000 ft and landed at 1953 without further incident. There were no injuries.

The flight crew later reported that they felt a slight movement on the rudder pedals on two occasions during the descent into Brisbane. The crew considered the rudder pedal movements to be minor and did not take any further action. About the same time, the crew also noticed that the map display on the Electronic Horizontal Situation Indicator (EHSI) was incorrect. The aircraft position depicted on the EHSI differed from the position indicated on the other navigation instruments.

Operator's Operations Manual

Volume B3 of the operator's Operations Manual contained information about the safety equipment and procedures. Section 5.1 included information about cabin depressurisation and actions to be taken by the flight crew and cabin crew following a depressurisation event. The manual used the term decompression when referring to depressurisation.

The manual stated that there were two types of decompression, gradual and rapid (explosive). The information provided in section 5.1 related primarily to the rapid type of decompression. The manual stated that `the angle in the cabin will become very steep as the aircraft descends at an approximate rate of 6000 ft per minute (normal rate of descent is approximately 2000 ft per minute)'. The manual also contained a warning that required the immediate use of oxygen by all crewmembers following the deployment of drop out oxygen masks in the passenger cabin. The manual advised cabin crew that the effects of a decompression event on the aircraft were:

1. Sudden boiling of liquids;
2. Loud noise as air escapes;
3. Air becomes thin, cold and dry;
4. Fog forms in cabin (should not be confused with smoke);
5. Dust and objects blown about;
6. Smoke alert devices in toilets may be activated; and
7. Flight crew may initiate an emergency descent causing the angle in the cabin to become very steep.

Aircraft examination

Following the incident, the electrical/electronic (E/E) bay was inspected and water was found to be dripping from the forward galley floor into the bay. There was also evidence of moisture leakage under the forward passenger door and service door. Moisture stains were found on the racks and ducting within the bay. The inspection also revealed that the moisture shroud was missing from above the E1 rack in the forward part of the bay.

A number of avionics units were removed from the aircraft, including the pressurisation controller, yaw damper coupler, auto-throttle computer and two stall warning computers. These units exhibited evidence of water damage, including moisture staining of component casings and corrosion of connector pins. There was no record of the maintenance staff finding moisture contamination in the E/E bay prior to the incident.

The operator stored beverages in polystyrene ice containers that were stowed in the forward galley. The containers were partially filled with crushed ice that melted during flight. The flight attendants on the incident flight did not recall any water spillage occurring from the ice containers, nor did they recall any turbulence that may have caused a spillage. The flight attendants reported that on previous flights on various aircraft there had been spillage from the ice containers, usually during landing.

Component testing

The manufacturer of the pressurisation controller inspected the unit and subjected it to a series of tests. A visual inspection of the outer case of the unit and the circuit boards did not find any damage or anomalies and a series of functional tests did not reveal any faults. Although there were indications of moisture staining on the outer case, there was no evidence of any residual damage to the unit due to water contamination. The manufacturer was aware of other instances where water had entered pressurisation controllers and caused problems in one or more of the operational modes.

An inspection of the yaw damper coupler found that the electrical filter was shorting out. After the filter was replaced the unit operated satisfactorily. A dent was also found on the top cover of the outer housing of the coupler, but it did not affect the operation of the unit. An inspection of the rudder power control unit found that the transfer valve was unserviceable due to an open electrical circuit.

Aircraft information

The aircraft was acquired from another Australian operator during October 2001 and underwent a pre-delivery inspection prior to commencing passenger operations on 1 November 2001. The operator's contracted maintenance provider conducted the inspection that was intended to ensure compliance with airworthiness directives and service bulletins.

The previous operator had purchased the aircraft from the United Kingdom and it was entered onto the Australian civil register on 3 December 2000. Between December 2000 and January 2001 the aircraft underwent modification and heavy maintenance work at an overseas engineering facility before entering revenue operations in Australia. The modifications included the removal of an airstair from under the forward passenger entry door. During that work the airstair drip pan and the cloth moisture shroud were removed from the E/E bay.

The documentation covering the removal of the airstairs specified that the moisture shroud was to be replaced following the modification work. However the shroud was not installed because the kits were temporarily unavailable from the manufacturer. One of the operator's engineers, authorised by the Civil Aviation Safety Authority to approve a design modification or repair, assessed that the absence of the moisture shroud would not affect the safety of the aircraft. On 29 January 2001, the engineer approved an amendment to the engineering release that permitted the installation of the shroud within 12 months of receipt of the parts.

The aircraft was subsequently operated on Australian domestic passenger services between February and September 2001 without the moisture shrouds being fitted. An order was placed with the manufacturer for the shroud kits and the delivery of the kits was due in November 2001. The moisture shrouds were not fitted to the aircraft when it was delivered in October 2001 to the current operator, who was unaware that the shrouds had not been fitted to the aircraft.

During the investigation, the aircraft manufacturer provided the following advice:

`Boeing advises that these shrouds are required in order to ensure the airworthiness of the airplane. 737 airplanes should not be used for revenue flight with these moisture shrouds not installed.'

`The 737 MMEL/DDPG does not provide any relief for these items to be removed from the airplane. Furthermore, the purpose of these shrouds is to protect the electronic equipment from moisture ingress. There have been several reports of 737 airplanes experiencing uncommanded flight movement due to moisture ingress into certain electronic components in the E/E Bay.'

On 18 April 2002, another Australian registered Boeing 737-33A, VH-CZR, sustained a depressurisation incident during a scheduled passenger service from Auckland to Christchurch, New Zealand. The incident occurred soon after top of descent when the crew selected the pressurisation system to the standby mode. The aircraft had a history of pressurisation controller problems when being operated in the AUTO mode, until approximately three weeks prior to the incident when the controller was replaced. The pressurisation controller fitted to the aircraft at the time of the occurrence failed during post incident testing, as the selection of standby mode resulted in the cabin outflow valve moving to the fully open position.

VH-CZR had a similar service history as CZQ, having been purchased by the same previous operator and undergoing similar airstair removal modifications at the overseas engineering facility prior to entering service in Australia. The aircraft also had not been fitted with moisture shrouds following the removal of the airstairs and the moisture shield over the E1 rack was not installed on the aircraft at the time of the occurrence in New Zealand.

The pilot of the Piper PA 32-260 was conducting the return sector of a charter flight for five passengers from Rottnest Island to Jandakot, WA.

The pilot reported that a strong and gusty southerly wind was blowing almost directly across the runway, but favoured a departure from runway 27. He used the indications from the aerodrome's windsock to assess the wind strength and determined that it was within acceptable limits for his aircraft.

Shortly before 1600 WST, the pilot taxied the aircraft to the threshold of runway 27. The pilot reported that he used a conventional crosswind technique for the take-off, with full aileron deflection into wind and use of rudder to maintain the aircraft on the runway centreline. The pilot reported that the airspeed indicator was reading about 65 - 70 kts when he positively rotated the aircraft nose for the initial climb. However, the aircraft did not respond to these control inputs and started drifting to the right. Despite applying full deflection of the rudder and aileron controls, the pilot reported that he was unable to maintain directional control of the aircraft.

The aircraft continued to diverge from the runway centreline, departing to the right of the runway strip and passing over a sealed taxiway and sandy scrub terrain. The right main landing gear collided with a tree stump on the edge of a shallow salt-water lake adjacent to the aerodrome. The aircraft briefly became airborne before coming to rest in the lake, in water that was less than 1 m deep. The pilot and passengers were not injured and vacated the aircraft without assistance. Although the aircraft was carrying an inflatable life jacket for each person on board, nobody was wearing one at the time of the accident and nor was this required by regulation.

Examination of the aircraft did not reveal any defect that could have affected its normal operation. Damage to the propeller blades was consistent with the engine operating at a high-power setting on impact with the water. Marks on the lower surface of the right wingtip were consistent with the tip of the right wing dragging across a hard sealed surface. The outboard portion of the right aileron also exhibited evidence of contact with a hard sealed surface.

The passengers recalled that the aircraft started to become airborne at a ground speed that seemed slower than the speed achieved during take-off from Jandakot earlier that day. They also reported that the ground roll along the runway seemed shorter. One of the passengers also described seeing a flashing red light on the instrument panel during the take-off attempt.

The pilot reported that following the accident he returned to the terminal building and was watching the aerodrome's windsock. During this period, he reported that the wind direction occasionally seemed to favour a departure from runway 09.

Examination of the runway revealed marks that indicated the aircraft commenced diverging from the runway centreline approximately 270 m from the threshold of runway 27. The aircraft's ground track was evident as it departed the runway strip and crossed the sealed taxiway. The ground track included abrasion marks from the tip of the right wing and the trailing edge of the right aileron, together with the track of the right main wheel. The marks on the right wingtip indicated that the aircraft was in a sideslip at the time and the nose was displaced right of the actual track across the ground. The aircraft came to rest about 530 m from the runway threshold and 120 m to the right of the runway centreline.

The aerodrome forecast issued by the Bureau of Meteorology (BoM) and current at the time of the accident forecast a wind from 190 degrees true (T) at 25 kts. BoM also issued routine half-hourly weather reports of the recorded conditions at the Rottnest Island automatic weather station (AWS). The report issued at 1530 indicated that the wind was 190 degrees T at 30 kts, gusting to 38 kts. These conditions were consistent with other reports issued on the afternoon of the accident.

The AWS for Rottnest Island is situated approximately 2 NM to the west of the aerodrome, on higher terrain about 160 ft above the aerodrome elevation. The site for the AWS is an exposed part of the island, and consequently, the recorded wind speeds could be expected to exceed those that would be experienced at the aerodrome.

Information from the AWS was not broadcast on either a discrete very high frequency radio or the Rottnest Island non-directional beacon navigation aid. The half-hourly reports issued by BoM could be obtained by pilots during pre-flight briefing and on request in-flight from air traffic services' Flightwatch frequency.

Minute by minute data from the Rottnest Island AWS indicated that during the 5 minutes prior to the accident, the maximum recorded wind speed was 38 kts, minimum wind speed 25 kts, from directions between 181 and 198 degrees T.

The east-west orientation of the runway at Rottnest Island and a series of sand hills to the south of the runway can significantly influence operations at the aerodrome, particularly at times when strong southerly winds prevail. This can include the effects of low-level wind shear, low-level turbulence in the lee of the sand hills and other conditions due to the behaviour of strong winds as they flow over and around the terrain.

Climatology studies of Rottnest Island conducted by BoM indicate that the runway is not aligned with the prevailing winds, and consequently, pilots can expect to frequently encounter crosswind conditions when operating at the aerodrome. In general terms, the strongest southerly crosswind components are more prevalent during the afternoons of the summer months. Strong northerly crosswinds appear to be more prevalent during the afternoons of the winter months. Records indicate that the runway crosswind component regularly exceeds 20 kts.

The pilot reported that he did not obtain a weather forecast for the day of the accident, but had received an operational briefing by telephone from the company chief pilot, prior to departing Jandakot on the first flight of the day. This briefing had included information obtained by the chief pilot on the weather conditions forecast for the day. The pilot did not obtain additional information or update the briefing received from the chief pilot during the course of the day.

The investigation calculated that the aircraft's operating weight at the time of the accident was below the maximum permitted take-off weight, with the centre of gravity in the vicinity of the published aft limit.

Forces acting on the aircraft during the initial stages of its take-off roll would cause the nose to yaw to the left as engine power was applied. In addition to this effect, at low speed during a crosswind take-off, the stability of the aircraft was such that the fuselage had the tendency to weathervane into wind. Control of the aircraft in those conditions required the application of a crosswind take-off technique to safely control the aircraft. From the perspective of aircraft controllability, a crosswind from the left (as was the case for the accident flight) was the more significant. This was due to the tendency of the aircraft nose to yaw left due to the crosswind, combining with the tendency of the aircraft nose to yaw left due to the application of engine power. The tendency of the aircraft nose to yaw is counteracted by the pilot applying right rudder, with the required amount of rudder input generally reducing as the aircraft accelerates and the rudder becomes more effective. During the later stages of the take-off roll, some left rudder input may have been required to maintain the aircraft on the runway centreline.

The investigation could not positively determine the airspeed of the aircraft at the time the pilot attempted to rotate the aircraft's nose to initiate the climb from the runway.

The US Federal Aviation Administration approved flight manual for the PA32-260 indicates that the demonstrated take-off or landing crosswind component is 20 miles per hour (17 kts). The Civil Aviation Safety Authority approved flight manual for the aircraft type stipulates a maximum permissible crosswind component of 20 kts.

The DHC-8-201 (Dash 8) aircraft was being operated on a scheduled passenger service from Sydney to Lord Howe Island. Overhead Lord Howe Island, when the flight crew was preparing for landing, the main landing gear failed to extend following normal selection. The crew then broadcast a PAN (radio code indicating uncertainty or alert), notified air traffic services (ATS) of a main landing gear problem, and requested a diversion to Port Macquarie. Radio transmissions between the aircraft and ATS were intermittent and radio relays from other aircraft in the area were employed. The request for diversion was granted and the aircraft tracked, first for Coffs Harbour, then Port Macquarie while the crew reassessed their fuel reserves. Enroute to Port Macquarie, the flight crew estimated that there was sufficient fuel on board for a diversion to Sydney, so they requested and received a clearance to track direct to Sydney.

Enroute to Sydney, when within very high frequency radio range, the flight crew contacted the operator on the company radio frequency and attempted to troubleshoot the main landing gear anomaly. Maintenance personnel suggested a check of the position of the landing gear inhibit switch. The switch was found to be in the INHIBIT position, rendering the gear unable to extend. The flight crew repositioned the switch to the NORMAL position and normal landing gear operation resumed. The aircraft continued to Sydney and completed an uneventful landing.

Prior to the flight, maintenance personnel replaced contact pins on the main hydraulic pressure transmitter connector to resolve a number 2 hydraulic system low pressure indication. During that maintenance, the landing gear inhibit switch had been placed in the INHIBIT position. Following maintenance, the maintenance engineers completed a hydraulic system operational check to return the aircraft to flight status. The check did not include a cycling of the main landing gear system, nor was there a requirement to do so. The number 2 hydraulic system retracted and extended the main landing gear.

Landing gear inhibit switch

The two-position (NORMAL and INHIBIT) landing gear inhibit switch was guarded (plastic cover to confirm position) to the NORMAL (OFF) position. The INHIBIT position provided an open electrical circuit to the landing gear down solenoid of the gear selector valve, preventing normal operation of the gear and also preventing illumination of the LDG GEAR INOP caution advisory light. Selecting the landing gear inhibit switch to the INHIBIT position idled the normal landing gear extension system actuators to ensure unhindered operation during alternate extension. Alternate extension of the landing gear used the freefall characteristics of the landing gear, and was used for emergency extension of the gear. The landing gear inhibit switch was also selected in flight crew training to provide the crew with realistic practice in using the alternate landing gear extension system.

Aircraft return to service and flight crew checklists

The operator reported that the maintenance procedures for returning the aircraft to service after maintenance included a requirement to check the landing gear inhibit switch position. They reported that the post-maintenance checks were not thoroughly completed because the maintenance personnel were interrupted by the flight crew during the task.

The operator checklists for the aircraft type were required to be conducted using the challenge and response method. The aircraft manufacturer's NORMAL PROCEDURES checklist, required that the landing gear inhibit switch was checked for selection to the NORMAL position. The operator's Civil Aviation Safety Authority approved ORIGINATING BEFORE START/ BEFORE START and NORMAL (originating) checklists included a check to confirm that the landing gear inhibit switch was in the NORMAL position. The BEFORE START checklist used by the crew, did not have such a requirement. The operator required that the ORIGINATING BEFORE START/ BEFORE START checklist be actioned following maintenance, other than ramp activity, of the aircraft. Under existing requirements, the ORIGINATING BEFORE START/ BEFORE START checklist was not required to be completed by the flight crew prior to take-off.

The manufacturers ALTERNATE LANDING GEAR EXTENSION/ LANDING GEAR MALFUNCTION (with illumination of landing gear inoperative caution light or loss of number 2 hydraulic system pressure) checklist included a check of the landing gear inhibit switch for the INHIBIT position. That checklist was not actioned as the landing gear inoperative caution light did not illuminate, nor was there a loss of number-2 hydraulic system pressure indicated during the flight. The operator reported that the crew decision to not use the alternate landing gear extension system once overhead Lord Howe Island was based on operational considerations.