Loss of control

The pilot intended to position a beacon on the roof of the Perth Control Tower. The task was to be accomplished by sling loading the beacon, which weighed 199 kilograms, below the helicopter. The aircraft was positioned about 40 metres to the north and about 25 feet above the tower. The pilot carried out an approach to the roof and hurriedly deposited the load. The load was then released from the sling, which was left attached to the helicopter. The aircraft was then manoeuvred across the roof with the sling being dragged over the surface. The hook on the sling became snagged on the tower guard rail and halted the helicopter's progress away from the tower and causing it to pitch nose down and roll to the right. With the cable being tensioned by the pull of the helicopter the hook freed itself from the railing and the sudden relaxation of the load on the cable caused it to spring towards the helicopter. The cable flew up around the tail boom and became entangled in one of the main rotor blades. The other main rotor blade severed the tail boom which fell free of the helicopter striking the side of the tower on its way to the ground. The major section of the helicopter then fell to the ground at the base of the tower, caught fire and was burnt out. The tower roof was 90 metres above the ground and the baseplate, onto which the beacon was to be positioned, was triangular in shape with sides of about 60 centimetres long. Specialist opinion was that such a task would be difficult even under ideal conditions but there is evidence that a wind shear was present at about 300 feet at the time of the accident. The pilot's licence was not endorsed for sling loading operations and he was not sufficiently current on the aircraft type, considering its handling characteristics and suitability for sling operations, to undertake such a job. The ground crew were inadequately briefed about the job and their duties, and an inappropriate communication system between the ground crew and the pilot was used. The electric quick release for the lifting hook fitted to the helicopter was unserviceable although the alternate manual system was checked and found to be working. The pilot had recently been retrenched from his permanent employment and had not found other work. It is likely therefore, that he was excessively motivated to complete the task even though he was experiencing difficulty in accurately controlling the helicopter.

It was the student's fourth flying lesson and the effects of power were being revised. The student turned the aircraft 90 degrees to the left onto downwind but when he attempted to level the wings after the turn, the bank angle increased from about 30 to 50 degrees. The instructor took over the controls and attempted to recover by applying right aileron, full power and holding the nose up briefly. When the aircraft did not immediately recover, the instructor lowered the nose but the aircraft struck the ground, in a left wing, nose low attitude, before full control could be regained. After revising the effects of power, the engine speed was set too low for the aircraft to sustain a level turn. The student maintained altitude by progressively applying up elevator and the instructor did not notice the incorrect setting because speed was assessed with reference to the ground in a 20 knot tailwind. The instructor delayed taking over the controls, because he thought that the aircraft was being subjected to mechanical turbulence generated by trees, over which they had flown.

The pilot was conducting cattle mustering operations. Weather conditions at the time were very hot, with a 10 to 15 knot wind. The pilot advised that while flying downwind at 30 knots and 80 feet above the ground, he commenced a pedal turn to the right. After some 90 degrees the turn suddenly stopped and the aircraft sank rapidly to about 35 feet above the ground. The main and tail rotors struck trees, but the pilot was able to maintain control and fly the helicopter to a clear area, where a safe landing was made. No defect was found with the helicopter or its systems which may have contributed to the occurrence and the reason for the loss of control, reported by the pilot, was not determined. This accident was not the subject of an on-site investigation.

The aircraft had been parked in the open and was exposed to a heavy frost. The pilot and his son attempted to clear ice accumulations from the top surfaces of the aerofoils by throwing warm water over them. Some 20-25 minutes elasped between the ice clearing operation and the takeoff attempt, during which time the aircraft was taxied to the airstrip and a second passenger emplaned. No further checks were made for new accumulations of ice. Following lift off, the aircraft commenced an uncommanded turn to the right. By the use of full left aileron and left rudder, the pilot was able to regain some directional control, but could not prevent the aircraft from striking boulders on the side of the strip. During the subsequent ground slide, the fuel system was broached and the aircraft was destroyed in the resulting fire. Post crash inspection of the aircraft revealed that the rudder had been fouling the elevator control, thereby preventing adequate control travel, for continued flight under the existing conditions.

The aircraft had been engaged in mustering cattle in flat, open country. The pilot elected to land near a utility to obtain further instructions from stockmen in the vehicle. Approaching the vehicle, the aircraft suddenly commenced to vibrate severely and to lose height. The pilot was unable to avoid a collision with the utility, following which the aircraft struck the ground heavily and overturned. No fault was subsequently found with the helicopter which might have contributed to the development of the accident. The symptoms described by the pilot suggested that the vibration experienced was associated with a main rotor blade tracking problem. It was likely that while manoeuvring to reduce speed prior to landing, the aircraft was placed in a position where the lead and lag action of the rotor blades temporarily exceeded the capacity of the blade dampers. Because of the low height above the ground at which this occurred, there was insufficient time or height in which the pilot could effect recovery.

The pilot was conducting sheep spotting operations on behalf of a friend. These operations had been carried out during the previous day, and the pilot had also assisted with mustering after flying for the day had been completed. On the following morning, the pilot commenced further spotting at about 0830 hours, and the aircraft was last seen about one hour later. The wreckage was discovered at about 0945 hours. The aircraft had impacted the ground while in a steep nose-down attitude, probably after stalling at a low height above the ground. No fault or defect was subsequently found with the aircraft or its systems which might have contributed to the accident. Remains of a cake and an apple were found in the wreckage. Medical tests revealed that the pilot had been eating immediately prior to the accident, and had choked when food became caught in his throat. It was probable that this incapacitation resulted in the pilot losing control of the aircraft.

On the day preceding the accident the station manager was informed that the pilot hired to carry out the muster would be late in arriving. He asked a stockman, who was a station employee, if he would carry out spotting duties until the other pilot arrived. About 20 minutes after the operation had commenced, the ground party heard the sounds of an aircraft impact. The pilot stated that he had been flying at between 400 and 500 feet above the ground when he lost control of the aircraft in a turn. The aircraft was discovered to have struck the ground while in a nose-low, stalled condition. The engine was not developing power at the time of impact, however no defect was subsequently found with the engine or systems of the aircraft. The pilot did not hold a mustering endorsement and had apparently not received formal training in low level operations.

The pilot arranged for a check flight in the aircraft, as it was a type he had not flown for some time. The instructor commented that as the pilot made rudder corrections during the takeoff roll, he also inadvertently applied light braking. After a period of general flying, the aircraft was returned to the circuit for a landing in moderate crosswind conditions. Touchdown was made in a three-point attitude, but shortly afterwards the aircraft commenced to swing to the right. Corrective measures by both pilots were unable to arrest the swing and the left gear subsequently collapsed. The pilot had used left aileron and right rudder inputs to align the aircraft at touchdown, and had possibly inadvertently applied braking to the right mainwheel.

The pilot was approaching to land in 10 knot crosswind conditions. Turbulence was encountered in the circuit area, and the pilot elected to approach at 80 knots with 20 degrees of flap selected. After a normal flare, the aircraft floated for half the 610 metre strip before touching down. The pilot applied heavy braking, but was unable to stop the aircraft within the confines of the strip. Damage was sustained as the aircraft passed through three drains. The approach speed was higher than required for the existing conditions. The strip sloped down in the direction of landing and it is probable that a tailwind existed at the time of landing.

The pilot was mustering a herd of cattle across a tree lined dry creek bed, when the mob scattered. He positioned the helicopter at tree top height to block the escape of the cattle from the creek. The rotor RPM rapidly decayed and the pilot was unable to prevent the aircraft sinking and landing heavily on the bank of the creek. The pilot attempted to bring the helicopter to a hover in a 15 knot downwind. At the time the helicopter was being operated near to the maximum all up weight in ambient temperatures of about 45 degrees celcius. Insufficient power was available to maintain flight in these conditions.