Collision with terrain

Circumstances:

The aircraft was conducting a scenic flight over an area of Lake Eyre North, where the surface of the lake is 30-40 feet below sea level. Weather conditions were fine. High cloud and calm conditions resulted in a glassy lake surface with diminished horizon definition. Passengers on the flight reported that the pilot had mentioned the possibility of flying below sea level, and later when approaching the lake, he remarked that it would be "tricky" without a horizon. He gave no indication that the aircraft was experiencing any difficulties which would affect its ability to maintain flight. The aircraft contacted the lake in a near level attitude, and in cruise configuration. The nearest landfall was twelve kilometres distant, and after several hours the passengers were reached and assisted by a rescue party. Rescue attempts by helicopters were abandoned when unable to safely hover due to the illusory effects created by the glassy surface. The passengers had not been provided with the required flotation safety equipment for this particular flight.

Significant Factors:

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

1. The pilot attempted to cross the lake at an extremely low level.

2. The pilot had insufficient experience to recognise the danger of the prevailing conditions.

3. The pilot was unable to maintain an adequate definition of the lake surface, due to visual illusions created by the glassy water surface conditions.

Recommendations:

1. It is recommended that the Civil Aviation Authority publish an article in the Aviation Safety Digest addressing the dangers inherent in low flight, particularly the visual illusions created by areas of water during calm conditions.

2. It is recommended that the Civil Aviation Authority publish an article in the Aviation Safety Digest to emphasise the requirement for the carriage of flotation equipment in accordance with CAR 258 and CAO 20.11 with respect to areas of water other than ocean. This accident was not the subject of an on-scene investigation.

The pilot received a request at 5am from a neighbouring property to fly a seriously ill person to a hospital some 150 kilometres away. During the approach to the property strip the pilot realised that the aircraft was too high and too fast so he attempted a sideslip to lose altitude. The aircraft floated the full length of the strip before the pilot decided to go around. During the go-around the aircraft stalled at about 50 feet above the ground after the pilot had commenced a steeply banked climbing turn to avoid trees.

The pilot was directing cattle through a gate when a cow turned and began to walk back towards the helicopter. It stopped in front of the aircraft before charging. The pilot applied back cyclic and up collective in an attempt to avoid the animal but the tail rotor struck the ground. The helicopter began to yaw and the pilot landed the aircraft immediately. It continued to yaw after the landing and the landing skid assembly was substantially damaged. The pilot was relatively inexperienced on the helicopter type, having the majority of his recent experience on more powerful and responsive types. On this occasion, the rate of cyclic application was too great and not compensated for by the collective input. This accident was not the subject of an on-site investigation.

After take-off from a property strip near the Silvan Reservoir, the aircraft was flown at a low height above the calm, smooth surface of the water. A left turn was completed at low level, but shortly thereafter the aircraft struck the surface near the middle of the dam. On initial contact, water entered the front of the cabin and the engine ceased running. The aircraft then bounced back into the air and the pilot attempted, unsuccessfully, to re-start the engine. The aircraft lost height and skidded along the surface to a halt before the nose began to sink. The three occupants evacuated the aircraft but only one passenger succeeded in reaching the shoreline. The wreckage was recovered, and an examination revealed no evidence of any pre-impact defect or malfunction which might have accounted for the accident. Water impact damage sustained by the engine cowling indicated that the aircraft struck the water at a shallow angle of descent, with the wings level. Damage sustained by the propeller assembly and crankshaft indicated that substantial power was being developed at the time of impact. Impact speed was estimated to be about 100 knots. While flying at a low height above the expanse of calm water, the pilot had very few visual cues to gauge his clearance from the water. It was also determined that the pilot had a blood/alcohol level such that impairment of his visual acuity was possible.

The pilot positioned the helicopter on the downwind leg of the circuit at an altitude of about 300 feet agl. The wind was gusting between 30 and 35 knots. Towards the end of the downwind leg the pilot noticed that the helicopter was yawing to the right and that a high rate of descent had developed. The pilot applied full power and lowered the collective slightly. The helicopter continued to descend and the pilot applied full up collective, but the helicopter struck the ground heavily and bounced. On the second touchdown, the tail rotor struck the ground and broke off. At the point of turning downwind, the helicopter was being flown at an indicated airspeed of 30 knots. On downwind it is probable that the pilot unwittingly allowed the indicated airspeed to decrease well below translational lift because of the rapid increase in groundspeed, resulting from the 30 knot tailwind. Had the helicopter touched down at zero indicated airspeed, when travelling downwind, it would have contacted the ground at 30 knots groundspeed and travelled a considerable distance along the ground. However, the helicopter travelled only about 12 metres after the first point of touchdown. This indicates that prior to touchdown, the helicopter was probably flying backwards in relation to the airmass in which it was operating, and was effected by the downwash from the main rotor blades. In such a situation there would have been insufficient altitude or power available to arrest the rate of descent.

Circumstances:

The pilot reported that he made a normal approach to land on a large claypan. As he raised the nose to enter the hover prior to touching down, the tail rotor struck the ground, and the pilot was unable to prevent the aircraft from rolling over.

The pilot reported that during a mustering operation he had descended to tree top height to force out a mob of cattle. He then turned downwind towards some other animals, and increased power. The helicopter did not respond as he had expected and began to lose height. The pilot stated that that there was insufficient room to recover and he guided the helicopter into the only clearing available. The aircraft landed heavily, and the main and tail rotor blades struck trees. The pilot reported that the wind was gusting to 15 knots at the time of the accident. The pilot stated that he did not notice any symptoms of engine malfunction and was unsure if the sink was due to insufficient power or overpitching. No engine defects were evident during examination after the accident. The reaction of the helicopter was most likely due to the combined effects of turning downwind and possible overpitching.

The pilot was operating the aircraft from the top of a gently sloping ridge in light and variable wind conditions. He lifted the aircraft into a hover one metre above ground level and began to accelerate forward. At about translational lift speed, the helicopter lost height and the tail rotor struck the ground. The pilot was able to land the aircraft straight ahead. Damage was sustained to the tail rotor drive, gearbox, and blades. The pilot had started work at 0445 hours on the day of the accident. He had flown 4.5 hours and had sprayed five chemical loads prior to the accident. This was the first concentrated period of flying he had undertaken in more than three weeks. Also, it was his first early morning start in that time. Both these aspects could have led to the pilot suffering a degree of transient fatigue. This might have been sufficient to cause a slight degradation in his performance sufficient for him not to compensate fully for the nose-up pitch as the helicopter passed through translational lift. This accident was not the subject of an on-site investigation.

Circumstances:

The pilot flew alongside a vehicle travelling along a gravel road. The two occupants of the vehicle knew the pilot well and they were not surprised to see the aircraft. The aircraft was then flown across the road in front of the vehicle at an approximate height of 250 feet. Whilst continuing their progress along the road, the occupants observed the aircraft perform a "wing over" manoeuvre. The aircraft failed to recover from the resultant steep dive, striking the ground at approximately 65 degrees nose down. The two occupants of the vehicle extracted the pilot from the crushed cabin. Detailed examination of the wreckage failed to reveal any abnormalities.

Significant Factors:

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

1. The pilot performed an aerobatic manoeuvre at a low height.

2. In all probability, the pilot inadvertently flew the aircraft into a high-speed aerodynamic stall from which he was unable to recover in the height available.

The aircraft was engaged in dual instructional circuit training. On what was probably the fourth circuit, the aircraft was observed to land heavily on runway 35 and then to climb away to the N. When the aircraft reached a height of 400-500 ft a witness heard the engine noise cease abruptly and saw the aircraft enter a nose-high, yawing turn to the left. The left wing dropped as the aircraft approached a W heading and the aircraft entered a spiral dive which continued until it collided with the ground. There was no apparent attempt to recover from the spiral. The weather conditions at the time of the accident were fine and cool with a light wind blowing from the N. An examination of the wreckage failed to reveal any pre-existing damage or fault which might have contributed to the accident. However, the left ignition switch was found to be in the 'off' position and propellor damage was consistent with the engine being stopped at the time of impact. This evidence suggested the left ignition switch may have been inadvertently knocked to the 'off' position during emergency actions following a simulated engine failure, resulting in the engine stopping. The initial heading change after the abrupt cessation of engine noise, was consistent with an attempt to turn back towards the runway. There was no evidence found of either pilot having been incapacitated during the flight. It could not be determined who was controlling the aircraft at the time of the power decrease, or why the aircraft was handled in a manner which led to a loss of control. Recovery action may have been impeded by the shoe of one of the pilots fouling the rudder pedal control mechanism.

Significant Factors:

The following factors were considered relevant to the development of the accident

1. A loss of engine power during the climb after take-off was consistent with a simulated engine failure.