Circumstances:

The pilot had flown to his property during the morning to find that his airstrip had a herd of cattle grazing on it. He had previously inspected an adjoining paddock on a neighbour's property, as an alternate airstrip and he considered that it met all the requirements for an ALA. He elected to use it rather than attempting to frighten the cattle off his own airstrip by "buzzing" them. That afternoon the pilot prepared to depart. The airstrip situated 2800 feet above sea level, and 390 metres in length was marginal. He believed that he would not have any trouble because the aircraft was lightly loaded, the airstrip had a slight downhill slope with short grass, and the take-off would be into a 10-15 knot headwind. The density altitude at the time was almost equivalent to the pressure altitude. The pilot had only recently purchased the aircraft and was not completely familiar with its operation and performance. He had not studied the performance graphs in the Flight Manual until some time after the accident. As some plug fouling had been experienced on previous flights, he carried out a thorough pre-flight check and engine run-up. During the take-off run the pilot thought that the engine did not appear to be developing full power, but it was running smoothly. The aircraft became airborne in 320 metres, accelerated to about 60 knots, but was unable to climb out of ground effect before colliding with the fence along the boundary of the paddock. A witness reported that the wind strength had decreased to almost calm conditions when the pilot commenced the take-off run. The aircraft struck the fence with the right hand wing, slewed to the right and came to rest on the other side of the fence, with substantial damage. This accident was not the subject of an on-site investigation.

During the circuit, the pilot and passenger were discussing fires near their property. The aircraft was subsequently landed with the gear up. The gear and its warning systems were serviceable. The pilot's attention was diverted from the operation of the aircraft by the fires and the pre-landing checks were not correctly completed.

The aircraft was cruising at 500 feet above some Sydney area beaches. Following an ATC instruction, the pilot applied full power in order to climb to 2000 feet. The engine ran roughly for a short period then lost all power and the pilot was committed to a forced landing in shallow water. Touchdown occurred about 5 metres from the shore-line and the aircraft came to rest inverted in the water. No pre-existing fault could be found with the aircraft engine or ancillaries. Atmospheric conditions were conducive to the formation of moderate carburettor icing. Carburettor heat had not been applied when the engine began to run roughly and lose power.

Following a report of engine rough running a section of an exhaust valve was found to have broken away. A new cylinder assembly including an exhaust valve was fitted, but on take-off for a test flight the engine suddenly suffered a substantial loss of power. During the subsequent forced landing the aircraft ran through a fence and came to rest in a ditch. Two cylinder assemblies were found to have suffered internal damage and pieces of the missing section of the previously replaced exhaust valve were found within the induction system. Although the engine had been ground run by the engineers it had not been tested to full power. As the pilot was asked to limit taxiing and idling times to avoid overheating the new cylinder, engine run-up and pre-flight checks were conducted whilst taxiing. Take-off was commenced 230 metres along the 1900 metre runway and this was the first full power demand made on the engine since its repair. At about 250 feet agl a power loss was experienced, full flap was not used for the forced landing attempt and the aircraft struck the ditch which was 274 metres past the end of the runway.

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.