Loss of control

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.

The pilot landed the helicopter to allow his passenger to alight. The engine was left running, the cyclic frictioned and collective held fully down. The pilot then felt a low frequency vibration begin and almost immediately the left side of the helicopter lifted and the tail swung to the right. Control imputs by the pilot had no effect and the helicopter rolled onto its side. One of the four belts providing drive to the transmission had jumped off the sheave, for reasons which could not be established. The belt had become wrapped around the clutch shaft and had caused a sudden braking action to the main rotor blades. This braking force was of such a magnitude that the fuselage yawed in an inertia reaction. The right skid dug into the soft ground and a dynamic roll-over resulted.

The pilot was carrying out a cattle-spotting operation prior to the commencement of the muster. He descended the aircraft to 500 feet above the ground to get a better view of some animals amongst the trees. The pilot reported that as the aircraft was being returned to level flight it was affected by severe turbulence and the pilot's door became unlatched. While attempting to close the door he noticed that the indicated airspeed had reduced and that the aircraft was continuing to sink. A turn to the right, to clear the area of turbulence, was commenced but during the turn the aircraft stalled and entered a spin. Attempts to recover from the spin were unsuccessful and the aircraft struck the ground in a nose down attitude while turning to the right.

The pilot had intended carrying out a flight around the property. When he had not returned by nightfall his parents rang neighbours before commencing a search. The wreckage of the aircraft was found two kilometres north-east of the homestead. It had struck the ground while in a steep nose-down attitude, in a paddock with no obstructions in the immediate vicinity. Investigation revealed that the engine throttle cable was broken, however it was not established whether this had occurred before or after the impact. The wreckage distribution was typical of that which follows a stall with insufficient height remaining in which to effect recovery. However, the reason the aircraft apparently stalled could not be determined.

The pilot was conducting a series of circuits and touch-and-go landings. Both three-point and wheel landings were carried out without problem. On the final landing, touchdown was made in a three-point attitude at a speed of about 45 knots. After the aircraft had rolled for about 100 metres, the pilot applied even braking to both mainwheels. The aircraft immediately veered to the left, and the pilot was unable to stop the swing before the right maingear collapsed. No fault was subsequently found with the braking system of the aircraft, and there was no sudden wind gust or other meteorological condition which might have contributed to the accident. Although the pilot had a reasonable amount of tailwheel aircraft experience, he lacked currency in the Cessna 180. It was likely that on the final landing of the exercise he had unconsciously relaxed his level of concentration.

On arrival at his destination, the aircraft overflew the homestead. This was the pilot's normal practice, to indicate to persons on the ground that transport from the nearby strip was required. The aircraft was then seen apparently following a gully containing a sunflower crop in which the pilot and passenger were partners. Shortly afterwards the sounds of an impact were heard. The aircraft was found to have struck the side of the gully while in a steep nosedown attitude and probably rotating to the right. No pre-impact defect or malfunction of the aircraft was found which might have contributed to the development of the accident. However, about 12 months previously, the pilot had applied tape over the stall warning vane, thus depriving him of aural warning of an impending stall. The wreckage distribution was consistent with that which follows a stall at low level where control of the aircraft is not regained before impact. It was likely that the aircraft stalled while the pilot was manoeuvring above the crop, but the precise reason for the stall and subsequent loss of control was not established.