The DHC-8 was inbound to Lord Howe Island and had made all necessary radio calls on the CTAF frequency. As the aircraft passed overhead the airport prior to landing, a Cessna 172 was sighted about 300 ft directly above. Normal radio communications were subsequently established between the aircraft and both landed without further incident.

The pilot of the Cessna later reported that he had been conducting a local flight around the island and considered that VHF communications may have been adversely affected by the mountainous terrain. He thought that was probably the reason why he had not heard any inbound radio reports by the crew of the DHC-8.

The airways clearance for VH-FKFs departure was runway 16, Strathbogie 1 SID. Soon after VH-FKF became airborne, the Departures radar controller noted VH-FKF turning onto an incorrect heading and queried the pilot. At about the same time the crew realised that they had not selected Fentons Hill VOR but still had Melbourne VOR selected to avail of the international DME. For a short time VH-FKF was intercepting the 200 deg. radial from Melbourne instead of from Fentons Hill. There was no breakdown in separation with other aircraft.

VH-LIH was tracking out of Albury for Sydney and was cleared to climb to flight level 120. VH-FNE was inbound for Albury, from Sydney, initially maintaining flight level 230. Because one of the radar stations was out of service the radar coverage in that area was unreliable and procedural separation was employed. The crew of VH-FNE were given descent to flight level 120, in error. The air traffic controller had intended to descend VH-FNE to flight level 130.

The crew of VH-LIH requested a clearance to climb to a higher level. This was not allowed as the controller mistakenly believed that VH-FNE was at flight level 130. The controller gave both crews traffic information on each other and asked them to report sighting and passing each other. In response the crew of VH-FNE told the controller they had been cleared to flight level 120, were currently at flight level 126 and were climbing back to flight level 130. Following discovery of the error in giving VH-FNE flight level 120, this aircraft was maintained at flight level 130 until it had passed VH-LIH.

Significant Factor

The following factor was considered relevant to the development of the incident:

1. Incorrect level clearance issued by the air traffic controller.

The pilot reported that the accident occurred at the end of the sixth leg for the day. The landing gear had been working normally. He had obtained a safe landing gear indication prior to landing. The right landing gear collapsed as the aircraft slowed after the touchdown. Inspection indicated that the torque link had failed in overload.

Subsequent engineering investigation indicated that a torque link retainer circlip had fallen off. The torque link's action had prevented the oleo piston from falling out until the link itself failed.

A similar problem had been detected during a scheduled inspection completed 20 flying hours prior to the accident. The clip was found to have fallen off and become stuck in the landing gear upper trunnion. The gear was only dismantled sufficiently for the clip to be replaced.

The factors that led to the circlip falling out were not determined at the time of the scheduled inspection and could not be determined after the accident as the circlip was not recovered.

Mariner 398 was tracking from Richmond to Nowra, via Camden and Wollongong. The crew had planned at 8000 ft but due to other traffic the aircraft was restricted to 7000 ft initially. The track took the aircraft close to D595 which is used for parachuting at Wilton. At 1215 the aircraft was approaching Camden.

VH-WRT departed from Wilton at 1210 for parachute operations and requested clearance to climb to flight level 130. The pilot was told by the sector 12 air traffic controller to climb to 7000 ft and remain within 3 miles of Wilton.

The sector 12 air traffic controller co-ordinated details on VH-WRT, including the 7000 ft altitude limit, with Sydney departures south. In response the controller was given identification on Mariner 398 and told that Mariner 398 was at 7000 and would call sector 12, eventually, at 8000 ft.

The sector 12 controller told the pilot of VH-WRT, at 1218, to maintain present altitude. The pilot acknowledged and said he was at 6300 ft. Subsequently the sector 12 controller passed traffic information on Mariner 398 to VH-WRT. The two aircraft passed with 700 ft vertical separation and one mile horizontal separation. The minimum separation required was 1000 ft vertical or 5 miles horizontal.

Significant Factor

The following factor was considered relevant to the development of the incident:

1. A lapse on the part of the sector 12 air traffic controller meant that the required separation was not applied.

At time 1831, 3 minutes after departure, a clearance was issued to the pilot of   VH-AJJ to track via Savoy and planned route with a climb to FL310.

No separation standard, i.e. 10 minutes or 1000 feet in altitude, was established between VH-AJJ and VH-JJQ.

At time 1839, VH-JJQ reported passing T84C at 1839, FL270, estimating Curtin at 1934. This transmission was made on the Perth Sector 2 (134.5) frequency.

At time 1843.5, the pilot of VH-AJJ reported maintaining FL310 and requested a higher level. VH-AJJ was now vertically separated from VH-JJQ.

The Controller was preoccupied with a separation problem in the vicinity of Karratha and did not fully assess the situation between VH-JJQ and VH-AJJ. It was also moderately busy at the time and a number of transmissions took place around the time of the incident. As a consequence of the workload, the Controller took the advice of the Sector 2 Controller who advised her to assign VH-AJJ FL310 due to SIA7220.

The Sector 2 Controller also entered a time when VH-AJJ would leave lateral conflict with SIA7220 on the flight progress strip for the Sector 1 Controller. This led the Sector 1 Controller to think that the Sector 2 Controller had looked at the entire scenario and offered a solution that would separate all the conflicting traffic.

The Sector 1 controller then issued a clearance to the pilot of VH-AJJ to climb through the level of VH-JJQ without fully assessing the traffic situation.

Factual Information

During cruise at FL250 in instrument meteorological conditions with light to moderate icing, the crew reported that the aircraft yawed to the left and the left engine ran down to about 4% torque then recovered in about 2 seconds. About 1 minute later the same problem occurred to the right engine. The pilot requested a descent to FL180 and disconnected the autopilot to hand fly the aircraft. About 30 seconds later both engines almost simultaneously suffered the same problem again. The crew carried out checks for erratic engine behaviour and requested a descent into Sydney for a precautionary landing. The remainder of the flight was uneventful.

Extensive ground checks revealed that neither engine had sustained damage as a result of the event. Flight Data Recorder information indicated that the first event occurred on the left engine when the torque fell to 26.4% with a loss of 1.8% RPM which recovered in about 4 seconds. One minute 24 seconds later the left engine again suffered a torque loss to 18.6% with a loss of 3% RPM recovering in about 3 seconds. About 30 seconds later the right engine suffered a similar event. Torque dropped to 18.7% with an RPM loss of 3.8% recovering in 3 seconds. These events occurred at FL250, and no further events were recorded.  Propeller and engine anti-icing were on at the time and continuous ignition was selected.

Information from the Bureau of Meteorology indicated that the aircraft was in light rain at the time and the water droplets were probably supercooled.

Analyses

Visual inspection of the aircraft revealed that both engines had an into-wind step where the inlet cowl fairs with the spinner (the engine cowl protrudes below the line of the spinner). The step on the left engine was more pronounced than the right. The manufacturer is of the opinion that an into-wind step in this location can result in the formation of ice which can interfere with inlet airflow and subsequently lead to ice ingestion. To rectify this problem the manufacturer has raised modifications and maintenance instructions.

Power recovery under these conditions is dependent on a fully serviceable ignition system. Either auto re-ignition or, if that system is unserviceable, continuous ignition must be selected.

The operator's Minimum Equipment List (MEL) provides for the aircraft to be dispatched with the auto re-ignition system inoperative. The system is then placarded inoperative and a procedure testing the continuous ignition system is carried out. This procedure requires observation of the flight deck lights for the L-IGN and R-IGN to ensure they illuminate. However, this procedure does not guarantee that the respective engine ignitors are operating.

CONCLUSION

Significant Factors

The following factors were considered relevant to the development of the incident.

1. The aircraft encountered an area of supercooled rain.
2. Both engines have into-wind steps at the inlet cowl to spinner fairing which allowed the formation and probable ingestion of ice.
3. Engine power recovery was effected by the ignition system.

SAFETY ACTION

As a result of this investigation, it was determined that the integrity of the ignition system is paramount for instantaneous power recovery to the engine.

The Bureau has made the following recommendation R950102:

The Bureau of Air Safety Investigation recommends that the Civil Aviation Safety Authority amend all Jetstream J 4100 Minimum Equipment Lists to include an audible test of the engine ignitors to ensure correct operation prior to despatch with the auto re-ignition system inoperative.

At the time of taxi out, for a runway 03 take-off, ATIS Delta was current. This advised the surface wind was from 090 degrees, with a wind speed of 20 kts, gusting to 30 kts. The crew arrangements were that the first officer would fly the aircraft from the right hand seat.

Take-off clearance was given to the aircraft and then the tower controller advised the crew that the crosswind was 22 kts. On the take-off roll rotation was commenced as normal. However, the captain sensed the rotation rate then increased and put the palms of his hands on the wheel to try and reduce the rotation.

A brief tail skid strike occurred during lift off. After take-off the tail skid retracted normally. Crew radio discussion with maintenance staff followed and it was considered safe to continue with the flight.

Company policy was that first officers are subject to limitations on the strength of crosswind allowed for them to perform a take-off. In the first year of operations the first officer was limited to 15 kts. The first officer flying the aircraft had been approved to take-off with 20 kts of crosswind.

The captain reported that he had looked at the windsock and assessed the wind strength and considered it did not exceed 20 kts at the time of take-off. Following the incident, it was not possible to determine whether the crosswind had exceeded 20 kts. However, senior company flight personnel considered that the tower report of 22 kts crosswind should have been used for the captain's decision on who should have done the take-off.

Significant Factors

The following factors were considered relevant to the development of the incident:

1. Significant crosswind component present during the take-off.

2. The captain probably made a judgement error in allowing the first officer to do the take-off.

3. An excessive rotation rate occurred during the take-off.

VH-NMA was en route from Perth to Meekatharra at 27,000 feet (FL270) and had passed position Mount Magnet at time 0810 and was estimating Meekatharra at 0831.

VH-FMQ departed Readys for Perth at time 0801 and was estimating Mount Magnet at 0819 and had planned at FL260.

In addition, VH-LBX was en route between Peakhill Mine and Perth. This aircraft had planned via Meekatharra (estimate 0825) and Mount Magnet (estimate 0848). VH-LBX was issued with a requirement to Reach FL240 by Meekatharra to facilitate separation with the other traffic.

At time 0813.5 a clearance was issued to the pilot of VH-FMQ to transit via planned route, to climb to FL220, and to expect higher levels at Mount Magnet.

At time 0816 an instruction was passed to the pilot of VH-NMA to leave control area on descent with a requirement to reach FL230 by time 0820. This was done to ensure separation with VH-LBX.

The pilot of VH-NMA queried the requirement and was told it was due to traffic. VH-NMA then commenced descent.

At time 0819.5, the pilot of VH-NMA reported leaving FL230 and requested the traffic.

The Perth Sector 4 Controller advised the pilot of VH-NMA that he could expect a short delay at FL230. The pilot queried this, stating he had just left FL220. The Sector 4 Controller then told the pilot of VH-NMA to report leaving FL210.

At time 0821, the pilot of VH-FMQ reported passing over Mount Magnet at time 0819, maintaining FL220.

The aircraft were now established on opposite sides of a Navaid and adequately separated.

The Sector 4 Controller had predetermined how to separate the aircraft involved, but gave the pilot of VH-NMA an

instruction to leave control area on descent, instead of limiting decent to FL230 to remain separated from VH-FMQ.

Prior to issuing the descent clearance, the Controller did not advise the pilot of VH-NMA of the plan to enable him to descend into Meekatharra without experiencing extensive delays. Had this been done it is likely the pilot of VH-NMA would have realised the error when he was given descent below FL230.

VH-FMQ passed over Mount Magnet at time 0819 which was the time that NMA reported leaving FL230, so although separation existed, the Controller was unaware of the fact.

The Controller was experienced and, at the time was also performing Team Leader duties.

A review of the flight strips indicated that no times of passing between the aircraft were recorded on the flight progress strips and other details missing indicated that the Controller was not performing at the required technical level at the time.

The traffic levels in Sector 4 when it is busy, particularly in the vicinity of Mount Magnet, may warrant a separate flight progress board bay designator for Mount Magnet. This would make it much easier to visualise conflictions than the current method where the Mount Magnet position is located adjacent to the Mount Singleton designator.

Safety Action

The Civil Aviation Authority are reviewing the possible use of a Mount Magnet designator on the flight progress board.

VH-TFB was inbound to Sydney from Canberra and had been instructed to descend to 5,000ft for an approach to runway 16R. At the same time, VH-WMY was inbound to Bankstown from the north, maintaining 3,000ft. VH-TFB was subsequently observed by radar to descend to 3,200ft, about 1 NM from VH-WMY. The pilot of VH-TFB was given traffic on the other aircraft and instructed to immediately turn left and climb to 5,000ft. This instruction was complied with promptly. The pilot of VH-WMY was visual between cloud layers and became aware of VH-TFB as it turned and climbed.

The pilot of VH-TFB later reported having been distracted whilst flying through a line of thunderstorms, associated with heavy rain and turbulence, and had inadvertently descended below his assigned altitude.