Collision with terrain

The helicopter was being used for feral animal culling with the pilot and a shooter on board. Weather conditions at the time were hot, and the helicopter was operating close to its maximum all up weight. While flying downwind the helicopter began to sink and the pilot overpitched the main rotor system while attempting to recover. The resultant loss of rotor RPM caused the helicopter to descend rapidly and strike a tree. Both occupants escaped with minor injuries, but the helicopter was destroyed.

The pilot was mustering sheep on his property and had handed off two mobs to ground handlers. He was on his fourth pass and was in a 45-degree left turn, descending from 100 to 50 ft at about 70 kts when he realised that he was too close to the sheep and applied left rudder to slip the aircraft away from the sheep. He then attempted to bring the wings level with aileron and arrest the descent without releasing the left rudder pressure. As the aircraft approached 50 ft, the pilot realised he could not recover and closed the throttle. The aircraft struck the ground with the left wing. The propeller then contacted the ground and the aircraft cartwheeled, coming to rest in a distance of about 40 m facing 180 degrees from the direction of flight.

Whilst returning from an aerial agriculture task, the Chief Pilot for the company elected to conduct some low flying over a lake. During this exercise, he misjudged his height, and the wheels contacted the water. The pilot lost control of the aircraft and it tipped over and came to rest inverted in the water. The pilot escaped without injury.

The aircraft was to carry out insecticide spraying operations at a rice farm. The pilot made an approach to the airstrip from the south, with a tail wind of about 3 kts. The pilot said that, shortly after touchdown, he observed cattle straying near the edge of the strip and elected to go-around. As the aircraft became airborne the right main landing gear struck an adjacent levee bank. The impact detached the gear leg which then struck the right horizontal stabilizer, detaching the elevator. The pilot said that, by remaining in ground effect, he was able to complete a right circuit and land the aircraft back on the strip. On touchdown, directional control was lost and the aircraft ground looped, colliding with large water pipes and associated equipment.

The pilot was en-route when he decided to land the helicopter in a clearing, near the edge of a small dam. The wind was from the north-east and gusting to about 25 knots. Temperature was about 25 degrees Celsius. As the aircraft was about to enter a hover the pilot noticed that the ground near the edge of the dam had too much slope to permit a landing into wind. He turned the aircraft slightly downwind so that the tail would be facing down the slope. At a height of about 15 feet the low RPM warning horn sounded.

The pilot attempted to reject the landing. He applied power, at the same time lowering the collective slightly and moving the cyclic forward to gain speed. The helicopter had insufficient forward speed or height to recover and landed in scrub, skids level, about 200 feet beyond the dam. It bounced twice, rolling onto its side after the second impact, severing the tail cone and destroying the main rotor blades.

The aircraft had been operating normally except for a report that the airspeed indicator was under-reading in cruise and the engine had been difficult to start for a number of days. On the morning of the accident the aircraft was flown from Karratha to Nanutarra in support of another aircraft. The pilot had been told that the Nanutarra strip was in good condition. However, this proved not to be the case as the surface was covered with brush up to one metre in height and the landing area was only ten metres wide.

The landing was uneventful, but the pilot had to remove some brush from the landing gear after landing. Prior to departure on the accident flight the pilot discussed the condition of the strip with the pilot of the other aircraft. This second pilot, who owned VH-WMV, paced out 500 metres of reasonable strip and indicated the pilot should use this for take-off. The pilot, still concerned, paced out a further 150 metres giving 650 metres in all. Although neither pilot referred to it, the take-off distance chart in the Pilots Operating Handbook (POH) indicated that 426 metres of ground roll was required in the prevailing conditions.

The pilot was also concerned about a shed at the end of the strip and decided that, in the event of an emergency during the take-off, he would steer the aircraft to the left of the shed. The aircraft was again difficult to start, and the owner's assistance was needed. During the taxy for take-off, the pilot had to use the auxiliary fuel pump, on several occasions, to keep the engine running. Although he completed the pre-take-off checks the pilot did not complete a magneto function check as he believed the strip surface was inadequate and he wanted to keep the use of high-power settings to a minimum.

The pilot did run the engine up to full power, against the brakes, before commencing the take-off roll. At that point all engine indications appeared normal. During the take-off roll the pilot concentrated his attention on keeping the aircraft in the centre of the very narrow section of reasonable strip. At the end of the 650 metres, he selected the normal climb attitude and lifted off at, what he believed was, about 75 knots. Immediately after liftoff the stall warning sounded and the pilot lowered the nose slightly, at the same time turning left to avoid the shed.

The aircraft continued to descend until it collided with trees. The aircraft came to a stop 150 metres to the left of the strip centreline and 1400 metres from the start of the take-off roll. The pilot reported that after liftoff he felt that the aircraft was not performing to expectations and that the engine had lost power. A post-accident inspection of the engine disclosed that the compression on two cylinders was probably below serviceable limits at the time of the take-off.

Also, the bottom plugs in two other cylinders may have been contaminated and not been working efficiently. The engine had been serviceable during the periodic inspection completed 87 hours prior to the accident. The reports that the airspeed indicator under-read in cruise, the engine was difficult to start, and the difficulty encountered by the pilot in keeping the engine running during taxy may also have been indications of poor engine performance.

The lack of normal acceleration, during the take-off roll, was probably the result of the less than optimum performance from the engine. The drag caused by the brush on the runway may have also been a factor. The pilot was forced to liftoff at the 650-metre mark as the condition of strip, after that point, was poor. Although the pilot reported that liftoff speed was 75 knots, the onset of a stall immediately after liftoff indicates that the speed was below this figure. The POH gives a power-off stall speed of 62 knots.

The power-on stall speed would have been something less than this. Once the aircraft had encountered the onset of the stall condition the pilot was left with no alternative other than to lower the nose and accept a forced landing. Although the pilot had a valid reason for not completing a magneto function check prior to take-off, the contamination of the spark plugs would have shown up during this check had one been carried out.

An aero club fly-in was organised at a property strip. One of the activities organised was a session of assessing skill and judgement in the form of flour bombing. The target was placed near the southern threshold of the north/south strip, and the contestants were to fly at 60 -65 knots, at 200ft AGL, drop the flour bomb and land straight ahead on the remaining section of the strip.

The passenger in the accident aircraft was a private pilot whose licence was not current. He sat in the left control seat whilst the pilot flew the aircraft from the right control seat. After take-off into the north, the pilot flew a left circuit followed by a level approach at about 200ft AGL towards the target. The passenger dispensed one flour bomb out of the left window and the aircraft then descended as if to land straight ahead but then entered a climb.

As the aircraft climbed, it was observed to drift left of the strip before commencing a teardrop turn to the right with increasing angle of bank. During this manoeuvre, the aircraft suddenly adopted a nose-low attitude and dived into the ground from a height estimated by witnesses to have been 130-150 feet AGL. The flaps were in the retracted position at impact. The passenger reported hearing the stall warning horn operate during the turn shortly before impact.

The pilot landed the helicopter in an easterly direction on a landing platform on the side of a hill. The helipad was at a drilling site in a rain forest area. As the wind was a light northerly, the pilot decided to reposition the helicopter by turning it to face into wind. As he manoeuvred the helicopter, he did not see an upright stick which contacted the spinning tail rotor.

Significant Factor

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

1. The pilot did not to see an obstacle prior to manoeuvring the helicopter.

The pilot, accompanied by an observer, was involved in the search for a missing child. While tracking along the Buchannan Highway, about 14 km west of the Stuart Highway intersection, footprints were noticed on the road, so it was decided to land and investigate. During the later part of the approach the pilot noticed that the GPS aerial, which is normally attached to the lid of the GPS unit, had fallen down into the area adjacent to the tail rotor anti-torque control pedals.

As the pilot brought the helicopter to a hover, he was unable to move the left pedal forward to overcome the torque from the increased power. With the pedals jammed the helicopter commenced to rotate to the right. The pilot attempted to fly forward in order to gain some airspeed for a run-on landing, but the helicopter continued to rotate rapidly to the right, completing three turns before impacting the ground. A thorough inspection of the helicopter failed to reveal any pre-impact faults or malfunctions which may have restricted the operation of the flight control system.

However, three separate items were found which could have jammed the tail rotor control pedals. These were: the detached GPS aerial, three rifle cartridge shells, and a plastic water bottle. Although all indications were that a foreign object had obstructed the tail rotor anti-torque control pedals, examination of these items did not reveal any tell-tale marks that would indicate they had been trapped between the pedals and the adjacent structure.

The pilot was flying to a strip he knew well. On arrival he assessed the wind and chose the strip direction for use. He noted that there were sheep in the same paddock, so elected to conduct a short field approach. On short final, the aircraft suddenly developed a sink from which the pilot could not recover.

The aircraft hit a fence at the threshold of the strip and landed heavily. After the pilot disembarked from the aircraft, he noted that the wind was gusting and that this may have contributed to the sudden sink. He did not add any margin to his approach speed to allow for the gust factor of the wind.