The pilot was conducting a noxious plant inspection and contour flying about 50 ft above hilly terrain at an indicated airspeed of 20kts to 25 kts.

The helicopter struck a single powerline which slide up the bubble and contacted the flying controls before breaking. Although cyclic control was partially lost, the pilot was able to land the helicopter without further incident.

The powerline had a span of approximately 200 metres between supporting poles and was difficult to detect from the air.

When the pilot selected the landing gear down for landing it failed to extend, and the circuit breaker (CB) popped. He reset it, but each time the gear was selected down it popped again.

He decided to return to Broken Hill because of the emergency services availability. On arrival he attempted to extend the gear manually, but he could not turn the handle. He was now committed to a wheels up landing.

An inspection revealed that the "up" limit microswitch attachment bracket had broken, preventing the lever arm making contact with the microswitch. This allowed the gearbox motor to continue running when the landing gear was selected up after take-off. The motor then ran the gearbox pinion and segment gears to the end of their travel, forcing and jamming their teeth together. When the gear was selected down the motor was unable to move the pinion gear and stalled, causing the CB to pop.

The jammed pinion and segment gears also prevented the manual extension handle being turned.

FACTUAL INFORMATION

Sequence of events

The pilot was conducting a visual flight rules scenic flight. These flights were done on a regular basis by the operator and the pilot had flown the DH-82 type on many of these. Commonly, the route flown was from Jandakot to the Fremantle area, north to about Mullaloo Point, then Observation City, Perth City and back to Jandakot. The pilot occupied the rear cockpit seat and the passenger the front cockpit seat. Shortly after passing the Fremantle Golf Course, at an altitude of 1,000 ft, the engine misfired and commenced to vibrate badly. The pilot transmitted a Mayday call to the Perth Radar Advisory Service (RAS). At this stage, the indicated altitude was 900 feet.

The pilot told the RAS controller that he had a partial power failure and said he was going to put the aircraft down in an area near Leeuwin Barracks, on the bank of the Swan River. The pilot was aware of the general details and location of the selected area. He tracked for a left base, while losing altitude, intending to land towards the west. The aircraft was halfway through the turn onto final, at a height of about 300 feet and with everything proceeding as planned, when the pilot suddenly saw a set of high-voltage power lines across his track. A large transmission-line tower for these lines was also now directly in front of him.

The pilot decided to complete a 270-300 degree right turn over the water to avoid the tower and pass under the wires and still land in the selected area. It was a tight, gliding turn and when passing through a heading of about east, at a height of about 150 feet, the aircraft stalled and started to spiral right. The pilot applied left rudder but was unable to prevent the aircraft from diving into the river at a steep angle. After impact, the aircraft floated vertically with the tail out of the water and both cockpits under water. The pilot found himself out of his cockpit swimming on the surface, but the passenger was still in the front cockpit.

Shortly afterwards, assistance arrived, and the passenger was released from his seat by a water-police diver. Both pilot and passenger were then conveyed to hospital.

Wreckage examination

Inspection of the engine showed that the number one connecting rod had failed. Approximately half the rod, including the big end attachment to the crankshaft, was missing. Inspection of the remaining fracture surfaces showed that the fracture was caused by fatigue crack growth. The crack had propagated along the centre of the connecting rod 'I' beam from the region of the connecting rod/crankshaft bearing housing. The reason for the initiation of the fatigue cracking could not be determined, due to the absence of pieces crucial to the investigation. The other three connecting rods were inspected but no cracks were found in any of these. The investigation was unable to trace the history of the failed connecting rod.

Each shoulder harness was attached to a transverse cable which in turn was attached, via a bracket at each end, to the aircraft structure. One of the attachment brackets for the rear seat shoulder harness had failed, with the bolt pulling out of (tearing) the bracket. The rear seat lap strap also failed. This probably happened because the seat moved during the impact sequence and the strap was cut by the metal edge of the seat. Even with the failures the rear seat harness absorbed considerable impact energy before failing although, the pilot did receive some facial injuries. One of the front seat shoulder harness attachment brackets, which was attached by three bolts, sustained a partial failure when two of the bolt heads separated. The harness however, remained intact.

The aircraft was equipped with leading edge slats on the upper wing. These devices have the facility to be locked closed. When unlocked, they open up when the aircraft approaches stalling speed. The slats have the effect of slightly reducing the stall speed and also provide a warning to the pilot that the aircraft is close to the stall. The flight manual for the aircraft included a statement that slat extension provides acceptable visual warning of approaching stall.

There were two placards in the cockpit that stated that the slats were unserviceable and not to be operated. Also, the operator's handling notes for the type included instructions that the slats were not to be used for take-off or landing. The slats were locked closed.

Weather data

The surface wind at Jandakot on departure was from the south-west at about 12 knots.

Forced Landing Options

The power loss occurred over a built-up area. There were very few forced landing areas available within gliding range. The Fremantle Golf Course, which was behind the aircraft when the engine malfunction occurred, was probably one option. Another was the area, near Leeuwin Barracks selected by the pilot. This latter area was aligned approximately east-west and had a set of high-tension power lines across the eastern end, aligned approximately north-south. The pilot was not previously aware of the power lines. The power lines and associated tower were not particularly obvious when looking down on them from above, and the restricted visibility from the rear cockpit of the DH-82A was another inhibiting factor.

ANALYSIS

The major reason for the accident was the engine malfunction which forced the pilot to attempt an emergency landing in a built-up area. The location of the engine malfunction meant that the pilot's options were limited. His choices were the golf course, which by then was behind the aircraft and out of sight, or the Leeuwin Barracks area.

To use the golf course the pilot had to execute a 180-degree turn. To reach the Leeuwin Barracks area the pilot only had to make a right turn of about 90 degrees. As a result, he opted for the site near the Leeuwin Barracks.

The pilot was satisfied all was going well until late in the approach when he suddenly saw the power lines and tower. This late sighting caused him to rapidly change his plans and attempt to avoid them. The aircraft was in a poor position, at a height of about 300 feet, for the pilot to attempt a large turn. However, this appeared his only option. During this attempted turn through 270-300 degrees, the pilot allowed the airspeed to reduce to stalling speed and he lost control of the aircraft. There was insufficient altitude to recover control before impact.

The fact that the slats were unserviceable and locked closed possibly deprived the pilot of an important stall warning indication. Had they been available and unlocked, they may have assisted in preventing the loss of control.

SIGNIFICANT FACTORS

The following factors were considered relevant to the accident:

1. Fatigue cracking of the engine's number one connecting rod caused it to fail. The factors which led to the fatigue crack could not be determined.
2. The failure of the connecting rod caused significant vibration and loss of power. These led to a forced landing.
3. There was a lack of suitable landing areas.
4. The pilot did not detect a power line and its associated tower until very late in the approach.
5. The pilot's attempt to avoid the power line led to a significant loss of airspeed.
6. The loss of airspeed led to a stall followed by loss of control at a height that was too low to effect recovery before impact.
7. The unserviceable slats may have been a factor in the pilot's failure to recognise the impending stall in time to prevent loss of control.

The pilot flew the aircraft with an instructor on the day before the accident flight. The instructor said that the pilot had not flown recently, and the pilot had not previously flown a Beechcraft Debonair. The next day the pilot proceeded to Caloundra with two passengers as planned. Witnesses at Caloundra airport saw the aircraft approaching to land. The aircraft was very high over the runway, and when it was obvious a landing could not be accomplished, the pilot carried out a go-around. The aircraft was seen making a second approach which was also very high, but not as high as the first. The pilot continued the approach, and the aircraft was seen to flare high and fast. The aircraft then landed nosewheel first and "wheelbarrowed" along the runway. The witnesses said it appeared that the engine had not been throttled back, as the aircraft did not slow down until it ran off the end of the runway into soft ground causing the nose gear to collapse.

The pilot was contacted and said that he had submitted a report, however, no report has been received. A check with the operator and the insurance loss assessor revealed that they had not received a report.

FACTUAL INFORMATION

Following a normal climb, the pilot dropped two parachutists over Hamilton Island. A power-off descent to circuit height followed. The pilot did not select Carburettor Heat during the descent. When on a long final approach, the pilot attempted to arrest a high descent rate with the use of engine power. The engine failed to respond. The pilot found that the aircraft was outside gliding range of the runway and he decided to ditch the aircraft in shallow water. Engine trouble checks failed to restore power to the engine.

The aircraft was ditched in shallow water and after a successful escape from the cabin, the pilot was picked up by an island launch.

The aircraft's engine was transported to a maintenance facility at Archerfield where it was examined. The engine was extensively corroded by salt water. No fault was found as far as could be determined.

The Bureau of Meteorology data showed that the relative humidity at ground level was 65%. The Carburettor icing - probability chart showed that serious icing at descent power was to be expected at such a humidity level.

ANALYSIS

Although there are other possible reasons for the power loss, it is most likely that the engine failed to produce power due to carburettor icing.

After landing on runway 34R in light rain, the aircraft vacated to the right, via taxiway 'T', continuing to decelerate, with the flaps still in the landing configuration. As the aircraft turned left onto taxiway 'J', the aircraft ran off the paved surface to the right of the taxiway and became bogged in soft wet ground. The crew reported they felt minor slipping during the turn but were unable to regain directional control by braking action or the application of reverse thrust. The wind was reported as 050/10-15 and there were patches of standing water on the taxiway. A subsequent engineering investigation found no fault with the aircraft or its steering system.

The taxiways were constructed with a slight camber, designed to assist water runoff. Photographic evidence indicated that the aircraft had commenced the left turn whilst on the right side of the centreline. A replay of the recorded surface movement radar indicated that the aircraft entered the turn faster than preceding aircraft, at about the maximum design speed for the taxiway.

It is considered likely that the north-easterly wind, acting upon the vertical surfaces of the aircraft, reduced the steering effectiveness of the nose gear in the slippery wet conditions as the aircraft turned from a northerly to a westerly heading on the right side of the cambered taxiway. Corrective action by the crew could not prevent the aircraft leaving pavement.

When the landing gear was selected down the left main landing gear did not extend. All efforts to extend the gear were unsuccessful. When the aircraft was landed the left wing settled to the ground and the aircraft swung to the left. Preliminary investigations disclosed that the left main landing gear door had failed to open.

Because the aircraft was new, having only been in operation for 330 hours, the manufacturer dispatched an investigation and repair team to assist the local maintenance organisation.

It was found that the left main landing gear fuselage door up hook pivot had seized. The initial function of the gear down sequence is to release the hook to allow the door to open. With the hook seized the gear remained in the up and locked condition.

The pivot pin and bush are both steel and were found corroded due to lack of lubrication. As well as the poor design of steel on steel, there was found to be no lubrication period or lubrication method detailed in the aircraft maintenance manual.

The manufacturer's immediate action was carry out a fleet modification to remove all main landing gear doors except for the gear leg mounted door. Subsequent assessment has found the door pivot mechanism to be inadequate and a fixed landing gear fairing has been introduced on a fleet wide basis.

Prior to departing Bankstown, the pilot detected bubbles of water in a sample of fuel that had been drained from the fuel tank sump. A further three samples were taken and, as the pilot considered these showed no signs of water he elected to commence the flight.

The pilot reported that as he reduced power during the approach to Goulburn the engine began to run roughly, prompting him to land the aircraft as soon as possible. A fuel sample taken, by the pilot, from the fuel tank sump showed evidence of further water contamination.  He subsequently drained several litres from the sump and considered there was no more water present in the fuel. The aircraft was then refuelled. However, a sample of fuel from the fuel tank again indicated the presence of a small amount of water. A further six samples, as well as a sample taken direct from the fuel bowser, failed to reveal any additional evidence of water contamination. After carrying out a ground-run and flight test, the pilot considered the engine was operating satisfactorily and continued his flight to Bankstown.

Whilst on final approach to runway 29R the engine suffered a complete loss of power when the pilot reduced power below 2,000 RPM. The aircraft landed heavily, pitched forward and overturned, coming to rest 270 m before the runway threshold.  The pilot was able to evacuate without injury. A subsequent inspection of the fuel system indicated there was water in the carburettor float bowl, fuel tank, and the inter-connecting lines.

The fuel tank of the Jabiru has a flat bottom with the sump located to the right and forward of centre. It is considered possible that any water in the tank may have pooled in one area away from the tank sump, particularly if the aircraft had been parked on a surface which was not level. During flight, as a result of flight attitude changes previously undetected water may have shifted within the tank and flowed into the sump and associated fuel line outlet, thence to the carburettor. The investigation was not able to determine the reason for the presence of water in the fuel system.

SAFETY ACTION

As a result of the investigation, the Bureau of Air Safety Investigation makes the following recommendation to the Civil Aviation Safety Authority:

R960063

The Bureau of Air Safety Investigation recommends that the Civil Aviation Safety Authority reviews the Jabiru fuel system design to ensure that any water contamination of the fuel can be drained from the system prior to flight.

A Jetstream 31 aircraft was inbound to Sydney runway 34, on descent from 6,000 ft to 4,000 ft, when severe turbulence was encountered. Whilst being subjected to sustained buffeting, the aircraft experienced uncommanded pitch and roll events. Both pilots responded on the controls, in an attempt to minimise the excursions. At the crew's request, the air traffic controller advised that their separation from a preceding Airbus A300, also tracking for runway 34, was six miles.

Examination of recorded radar information confirmed that the required wake turbulence avoidance separation standard had been maintained. At the time at which the Jetstream 31 had experienced the upset, the A300 was 6.3 NM ahead. However, when closest to the point at which the upset occurred, the A300 had been 600 ft higher than the Jetstream, and the flight path of the A300 had been about 1 NM upwind of that of the Jetstream.

The effect of the prevailing wind, and the descent of the Jetstream to an altitude of less than 1,000 ft below that of the A300, placed the significantly smaller aircraft in the wake turbulence generated by the wide-bodied aircraft.

1. FACTUAL INFORMATION

1.1 History of the flight

The aircraft was the second to take off in a stream of six on a night flight from the Tangalooma Resort strip to Coolangatta aerodrome. Shortly after take-off it struck the ground, nosed over, and was consumed by a fuel-fed fire.

The take-off run appeared normal, but the initial climb was shallow according to the witnesses, some of whom were pilots waiting their turn to take off. At about 150 ft above ground level the aircraft entered a descent which continued until ground impact, 164 m beyond the departure end of the strip. The nose gear collapsed at impact, but the aircraft remained upright and skidded along the ground on its main gear and front fuselage. It traversed a low sand dune, fell 10 ft to the beach and overturned. The aircraft came to rest 112 m beyond the first ground contact. All four passengers were able to evacuate the aircraft which had started to burn. The pilot was rescued by her passengers.

1.2 Weather and visibility

The weather was fine with some cumulus cloud over Moreton Bay to the west of the strip. It was a dark night with only stars visible. The wind was almost calm but slightly favoured a take-off towards the north. The northern take-off path extended over north-eastern Moreton Bay. Except for a possible light from a fishing trawler or house at Cowan township, there was no surface illumination and no discernible horizon. A take-off to the south on the other hand was available with a distinct horizon reference due to an illuminated Tangalooma Resort some 5 km south and the very bright lights of the Brisbane Port facilities at Fisherman Islands some 40 degrees to the right of runway heading.

1.3 Personnel information

1.3.1 Pilot in command

The pilot was a Grade 2 instructor, employed by the flying school where she learnt to fly. She had a current command multi-engine instrument rating and was endorsed to fly the aircraft type. The pilot was required to wear spectacles when flying and she did on this occasion.

On 14 September 1995, the pilot was checked on the route by the chief pilot. The route check included a night take-off at Tangalooma strip. Her most recent flights in the aircraft were on 15 October and 2 November 1996. Both flights were return flights between Coolangatta and Tangalooma, with a night take-off from the Tangalooma strip. The night take-off on 2 November was conducted towards the south.

1.3.2 Previous 72-hours history

The weather on the two days before the accident precluded any flying duties. During this period, the pilot worked at the flying school office and brought her book-keeping duties up to date. On the two nights prior to the accident, she had retired to bed at 2030 hours and 2130 hours local time, respectively. Prior to then she had been off duty for 9 days. On the day of the accident, the pilot commenced duties at 1400 hours, planning the afternoon flight to Tangalooma and the night return. Between her arrival at Tangalooma and the night take-off, she rested and had dinner at the resort.

1.3.3 Information from the pilot

The pilot was hospitalised with serious leg injuries. She had also suffered a blow to the head. She was interviewed in hospital and said that she could not remember the take-off and subsequent flight into terrain. The pilot said that the aircraft carried a printed checklist on a single sheet of paper which her employer required company pilots to use in normal aircraft operations. However, for reasons not established, the pilot did not use the checklist after landing at the island strip or during the subsequent night departure.

1.4 Passenger action

The four passengers were foreign nationals and were seated in rows 2 and 3. They were not injured in the crash and were able to crawl out through the open cabin doorway. A fuel-fed fire had started almost immediately, and the aircraft was well alight by the time they cleared the aircraft. They soon realised that the pilot was still in the cockpit. Some of the passengers crawled back inside and pulled the semi-conscious pilot clear of the aircraft. Other people arrived on the scene soon afterwards and moved the passengers and pilot further away from the burning aircraft.

1.5 Wreckage examination

The aircraft had come to rest upside down on a beach. The front of the cockpit was crushed during the nose-over. The cabin was completely destroyed by a post-impact fire which also damaged the right engine.

Examination of the wreckage found that the flaps were retracted and that the elevator trim was set about halfway between the take-off setting and the fully forward position. Both engines were removed for specialist bulk strip examination. This examination did not discover any defect which could have prevented the engines from developing rated power. This evidence supports witness information that the engines' note did not change during the entire flight sequence. Due to the high wing configuration, neither propeller contacted the ground until the aircraft nosed over. Examination showed significant torque twisting and bending to both propellers indicating that the engines were still developing significant power when the aircraft nosed over.

1.6 Aircraft flight characteristics and flight test

1.6.1 Flap retraction

Discussions with pilots experienced on the aircraft type indicated that during initial climb, the take-off flap must be retracted in stages, trimming the elevator at the same time. Their opinion was that if the flap was retracted in one movement instead of stages, the nose-down trim change would be significant.  This would result in a lower nose attitude unless the pilot held back pressure on the control column.

1.6.2 Flight test

At the Bureau's request a flight in a Partenavia was undertaken by a Grade 1 instructor with the view to establishing elevator control forces under specific conditions. The aircraft was flown on a final approach with full flap selected. The elevator was trimmed so that there was no residual force on the elevator control. This resulted in a trim indication halfway between neutral and a fully nose-down position. A take-off was conducted with the elevator trim and flap in the previous position. The pilot reported that a medium-to-heavy rearward elevator force was required to rotate the aircraft and establish a positive rate of climb. At a safe height, the flaps were retracted. This procedure was accomplished twice with the following result:

1. If the indicated airspeed and rate of climb were maintained the elevator force increased to the point of being very heavy.
2. If the elevator force was not increased, the aircraft settled into a 400 ft per minute rate of descent.

The pilot conducting this test commented that unless a pilot was prepared, the high elevator force required to maintain a positive rate of climb was excessive and well outside the normal experience range of an average pilot.

1.7 Dark night take-off research

Bureau research has shown that dark night take-offs can present a number of special problems for pilots, particularly when departing from aerodromes in areas with little or no ground lighting. Specifically, the somatogravic illusion has been suggested as being a contributing factor in the majority of these accidents. A somatogravic or false climb illusion occurs when a pilot who is deprived of outside visual cues attempts to maintain a desired pitch attitude without reference to instruments whilst the aircraft is accelerating. Under such conditions, pilots can experience a sensation of excessive pitch-up. The sensation is thought to exist primarily at take-off, go-around and during visual flight into cloud. At take-off, pilots who attempt to correct for this sensation by relaxing the backward pressure on the elevator control, may fly the aircraft into the ground.

2. ANALYSIS

2.1 The checklist

The pilot said that she did not use the checklist following the daylight landing at the Tangalooma strip, nor did she use it prior to the night take-off. The pilot could not give an explanation for this omission. A checklist written on loose paper can be difficult to handle during busy periods of operation such as circuit work or in low-light conditions, specifically at night. This could explain the lack of use in this case. If a checklist is not used, the pilot must commit all checks to memory.

2.2 Elevator trim

The elevator trim was found in a position consistent with the trimmed position for a full-flap landing. It is highly likely that the pilot missed the trim item off her memorised checklist both following the daylight landing and during pre-take-off checks at night.

2.3 Evidence from the test flight

The test flight pilot reported that the elevator force induced by an incorrectly set elevator trim would overpower a pilot who was not prepared for this predicament. The shallow take-off witnessed by others was probably the result of the pilot encountering such an unexpected down-elevator force. The pilot probably retracted the take-off flap in one movement rather than in a staged retraction since she would have needed both hands on the control column. Such an action could only have exacerbated the downward force on the elevator.

2.4 Dark night take-off

In addition, the pilot was faced with a dark night take-off. Unless the pilot's attention was focussed almost solely on the correct climb attitude, it was likely that the nose attitude would be lowered inadvertently. Because of the unexpected elevator force, she was probably distracted from her proper instrument scan. Under these circumstances, an illusion of a false climb would have resulted in her not maintaining the high load needed on the control column. This would have resulted in the aircraft descending back onto the ground. That this came as a totally unexpected event is borne out by the lack of any action in correcting the aircraft attitude, reducing descent, or reducing power.

The collective decision by the pilots to conduct take-off operations towards the north was unwise, considering that a useful visual horizon was available for take-offs towards the south.

3. CONCLUSIONS

3.1 Findings

1. The pilot was fully qualified to undertake the flight.
2. The night was dark and the area beyond the departure end of the runway was devoid of any useful lighting.
3. A southerly take-off direction was available, with a visible horizon.
4. The pilot did not make use of the written checklist carried in the aircraft.
5. The elevator trim was set halfway between neutral and fully forward.
6. The flaps were fully retracted at impact.
7. The aircraft impacted wings-level and in a shallow descent.
8. Full power was maintained throughout the take-off and accident sequence.

3.2 Significant factors

1. The take-off direction was dark and had no visible horizon.
2. The elevator trim was not set for take-off.
3. The elevator load on take-off was high.
4. The pilot did not monitor the aircraft attitude after lift-off.
5. The flap was retracted in one movement, increasing the elevator load.
6. The pilot may have been affected by somatogravic illusion to the extent that she thought the climb attitude was adequate.