At the time of the accident, weather conditions were fine but it was a very dark night. The stars were obscured by a high overcast and there were only a few ground lights. The horizon was not visible. The take-off was into the southeast. Shortly after becoming airborne the aircraft entered a left turn and then began to descend. This continued until the aircraft struck the surface of a salt lake, in an inverted attitude. No contributory faults could be found with the aircraft or aircraft systems. The pilot was inexperienced in night operations and on this occasion there was a lack of external visual cues available. It is probable that the pilot became disorientated during the turn after take-off and lost control of the aircraft.

Circumstances:

The pilot reported that whilst conducting cattle mustering at about 50 knots and 150 feet above the ground, the engine failed. The pilot considered that the engine failure was caused by a fuel blockage, although the fuel had appeared to be clean during the preflight inspection. The cause of the engine failure has not been established.

The pilot reported that he had made a good approach, but had flared high. The aircraft landed heavily on the mainwheels then nosewheel. Buckling of the firewall and undersurface of the fuselage was discovered after the aircraft had been shut down in the parking area. Prior to the accident, the pilot had occasional difficulties in the landing phase. The airspeed indicator was found to be overreading by five knots at threshold speeds. This reduced the margin above the aircraft stall and is likely to have increased the pilot`s handling difficulties.

The helicopter was hovering at about 100 feet agl when the engine stopped. A heavy landing followed. The pilot reported that he knew the aircraft normally had an endurance of approximately 220 minutes. On this flight he had been operating for 210 minutes, the task was almost completed and the refuelling point was a short distance away. He continued for a short time with the fuel gauges indicating empty in order to complete the task. The engine failed over an area of trees and the subsequent manoeuvring and flight to the closest open area resulted in insufficient rotor RPM being available to complete an autorotative landing.

At the conclusion of the student's first training exercise the instructor positioned the helicopter in a hover at about 3 feet agl and allowed the student to use the controls. The aircraft was headed into the 25 knot gusty wind when sudden sink was experienced. The student instinctively applied full aft cyclic control and the heel of the right skid dug into the ground as the helicopter moved backwards. The aircraft rolled onto its right side, destroying the main rotor blades and distorting the cabin area. The instructor had allowed the student to attempt an operation beyond the level of his current ability and had been unable to recover control when the sink was experienced.

As the pilot reduced power on reaching cruise altitude, he noticed a vibration through the aircraft. The vibration increased in intensity and the aircraft instruments became difficult to read. The pilot was unable to determine the cause of the vibration and decided to carry out a landing in a paddock. The downwind approach was misjudged and the chosen landing area overshot. The pilot then became concerned about the proximity of the trees at the end of the paddock and attempted to force the aircraft onto the ground. The aircraft struck a tree, then the ground, nosed over and came to rest inverted. During the approach the pilot had not used flap as he had been concerned that the vibration may have been airframe induced. However, inspection of the aircraft did not reveal any contributory airframe fault. Evidence was found that the four exhaust valves had been sticking and given the high ambient temperature, high oil temperature and low oil pressure indications subsequently reported by the pilot, it is probable that the vibration was caused by stuck exhaust valves.

As the helicopter was brought to a 20 foot hover, it began to swing to the right. The pilot applied left pedal but the rate of turn continued to increase rapidly until the helicopter impacted the ground. The right skid broke off and the aircraft came to rest on its right hand side. Examination of the tail rotor pitch control system revealed that the bolt which connects the tail rotor pitch control arm to the control rod, below the tail rotor gearbox, was missing. The bolt was never found and the reason for its absence could not be determined. It was evident that the loss of the bolt resulted in the loss of tail rotor control.

The pilot had built the single seat aircraft himself and had previously only flown it on one occasion. After completing the first circuit, the aircraft was taxied back to the threshold and the second take-off commenced. Just after lift-off the aircraft was observed to pitch nose up. The right wing dropped and the aircraft turned to the right before impacting the ground. When the aircraft tail came up during the take-off roll, the pilot became concerned that it was too high and that the propeller might strike the ground. In attempting to avoid this, excessive back pressure was applied to the control column. The aircraft became airborne prematurely and then stalled.

After crossing the threshold at 75 knots power was reduced to idle and a landing flare commenced at about 25 feet agl. The aircraft floated for some distance before the nosewheel contacted the ground heavily 400 metres from the threshold. A bounce ensued followed by a further heavy touchdown on the nosewheel which then collapsed and was torn off as the aircraft slid on its nose for 98 metres.

Circumstances:

The aircraft was conducting cattle spotting operations from an estimated height of between 90 and 150 metres above ground level. The pilot was relatively new to the task and was being guided by the passenger, who was in radio contact with the ground mustering party. The procedure was for the aircraft to spot and then fly directly over cattle as a guide to the ground party. Following the first flight of the day, the aircraft was refuelled from a newly opened 200 litre drum of aviation gasoline. The aircraft then took off normally and flew over one group of cattle before heading north-east towards another area. A short time later, a high revving engine noise was heard followed immediately by the sound of impact. The aircraft had impacted the ground 48 degrees nose down and slightly right wing low on a heading of 158 degrees Magnetic. The fuel tanks ruptured on impact, and the wreckage caught fire. The extent of the fire damage was such that a thorough examination of the wreckage was not possible. However, of the components that were able to be checked, no fault was found which might have prevented normal operation of the aircraft. The engine was operating at impact, and the flaps were at 15 degrees. The steep nose down attitude of the aircraft at impact is typical of what might be expected as a result of the aircraft stalling at low level and the pilot having insufficient height to effect recovery. While there is no proof of this occurring, there were circumstances existing which could have contributed to its development. These included the sun being on a Magnetic bearing of 40 degrees and an elevation of 25 degrees above the horizon at the time of the accident, indicating that the pilot could have been affected by sun glare as the aircraft headed north-east. During the refuelling stop, the passenger remarked on the turbulent conditions at the operating height of the aircraft. If the aircraft was operating at comparatively low speed (and the flap setting probably indicates this), then the turbulent conditions could have upset the aircraft to the extent that it stalled, with the sun glare preventing the pilot detecting the upset.

Factor

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

For reason(s) which could not be positively established, the pilot lost control of the aircraft at a height from which recovery to normal flight could not be effected.