The pilot reported that at the time of the occurrence the aircraft was over water descending through 650 feet at 80 knots for a beach landing on Pelorus Island. Engine power was set at about 70 percent torque. A strong airframe vibration suddenly began, accompanied by a noticeable bang. The helicopter yawed left and the pilot saw the engine out light illuminate and the engine tachometer reading decreasing. He did not recall any other instrument indications. As the pilot corrected the yaw and lowered the collective pitch control, the vibration ceased. He transmitted a mayday call and then, with his left hand, operated the switch on the overhead console to arm the emergency floatation bags. As the aircraft approached the water, the pilot attempted to operate the float inflation trigger at the same time as he returned his hand to raise the collective pitch control to complete the forced landing. The floats did not inflate. However, the pilot was not sure as to whether he had operated the trigger properly. The pilot thought that the helicopter contacted the water in a slightly tail-low attitude. He kicked open his door and was able to egress from the helicopter as it rolled left. The front left seat pasenger and the rear right seat passenger escaped from the cabin without assistance as the fuselage became inverted. The passengers in the left and centre rear seat positions were assisted from the helicopter by the pilot. Attempts to locate and recover the helicopter were hampered by the water depth in the area, strong tidal currents, and an uneven, rocky sea bed. While some possible sonar contacts were identified, the position of the helicopter could not be positively determined. Consequently, the search was called off and the wreckage remains unrecovered. The descriptions of the occurrence provided by the passengers matched that given by the pilot and indicated that the engine probably suffered a complete power loss. However, because the wreckage was not recovered, no positive conclusion can be drawn as to the causal factors involved. The helicopter had flown some 7 hours since undergoing scheduled maintenance, during which a new engine compressor was fitted. The turbine was also removed and refitted to facilitate the compressor change.

The 700 metre long strip was covered with grass approximately 60 centrimetres long. Although the pilot had operated from the strip previously, on this occasion two passengers were carried. The pilot became concerned with the aircraft's rate of acceleration and decided to abort the takeoff. However, the aircraft overran the strip and the nose gear collapsed when it struck a log hidden in the long grass. This accident was not the subject of a formal on-scene investigation.

Circumstances:

Shortly after full power was applied for take-off, the pilot noticed that the aircraft was tracking to the left of the strip centre. He turned gently right to correct the situation, and the nose gear leg collapsed soon after. Metallurgical examination concluded that the nose gear leg mounting trunnions contained fatigue cracks. One trunnion had failed during this take-off. The aircraft had accrued almost 20,000 hours and an inspection recommended by the aircraft manufacturer less than one year prior to the accident had not been conducted. Had the inspection been conducted, the fatigue cracks should have been detected. Some time after this aircraft was manufactured the manufacturer altered the design of the mounting trunnions to make them stronger.

Significant Factors:

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

1. Nose leg mounting trunnions of weaker design than later versions.

2. The operator had not conducted inspections recommended by the manufacturer.

3. The aircraft was frequently operated on rough strips.

4. Fatigue fracture of the nose gear mounting trunnion.

Circumstances:

The left seat pilot was undergoing his second session of endorsement training in the aircraft. After a cross-country exercise under simulated instrument flight conditions, the aircraft returned for a landing on runway 11 Left. The pilots reported that the undercarriage was selected down on the downwind leg and confirmed by three green lights and the left engine nacelle mirror. The approach and landing were reported to be normal, with initial touchdown on the main wheels. Soon after the nosewheel contacted the ground, the nose gear collapsed. Examination of the nose gear down lock mechanism, indicated that it had been subjected to considerable forces which could only be attributed to a heavy landing or landings. These forces had dislodged the down lock roller and stop bolt away from the down lock hook. Subsequent forces then allowed the nose gear to retract and hence collapse.

Significant Factors:

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

1. Nose gear mechanism had been damaged by a heavy landing or landings. This accident was not the subject of an on-scene investigation.

Circumstances:

The student pilot was receiving instruction in the procedures associated with an engine failure after take-off. At 1000 feet above ground level carburettor heat was applied, the throttle retarded to idle, and the aircraft configured for descent. At 800 feet the power was reapplied, carburettor heat was selected off and the aircraft climbed back to repeat the lesson. After the second exercise the engine would only develop 1500 rpm and was running roughly. The instructor took over, exercised the carburettor heat and left it on, but there was no improvement in engine performance. He then carried out a forced landing in a paddock. During the latter part of the landing run the nosewheel dug into the soft surface, and the right wing was damaged. The weather conditions at the time (ambient air temperature 16-17 with a dew point of 11 and overcast) were favourable to the formation of carburettor ice. The engine had recently been overhauled. The operator reported that the aircraft normally gave only a very small drop in rpm when carburettor heat was applied. The spark plugs were found to be heavily sooted with a fresh carbon deposit, which indicated that the engine had suffered a rich cut. This is consistent with the effects of ice accumulating in the carburettor. The carburettor heat box was found to be loosely fitted to the carburettor, and one side of the box had a rubber seal missing. This resulted in a loss of effectiveness of the carburettor heating system.

Significant Factors:

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

1. Inadequate maintenance and inspection of the carburettor heat box.
2. Weather conditions were favourable for the formation of carburettor icing.
3. The operator and pilots did not recognise the significance of the very low drop in rpm when testing the carburettor heat system.
4. The pilot was forced to land on unsuitable terrain.

The student pilot was attempting a full stop landing while under instruction. The wind was light and variable with occasional gusts producing 6 knots of crosswind from the left on runway 23. The approach, flare and touchdown were reported to be uneventful. About two seconds after touchdown the aircraft was hit by a wind gust and swung suddenly to the left. The student pilot immediately applied full right aileron which pitched the aircraft on to the right wingtip. It then pivotted heavily onto the nose gear which collapsed. The aircraft skidded to a halt on the sealed surface.

Circumstances:

The Facet Opal ultralight aircraft was of a tailless, flying wing design. This unique aircraft was designed, constructed, and operated under the provisions of Civil Aviation Orders, Part 95, Section 95.10. The aircraft arrived in the Lake Munmorah area after completion of the 300 nm flight at an average ground speed of about 100 knots. Upon arrival, the aircraft was observed to circle near Norahville and Lake Munmorah to alert relatives of the pilot's arrival. The aircraft took up a SW heading near Doyalson at the completion of the orbit. Witnesses reported sighting the aircraft at about 300 ft agl and travelling at about 100 kts. As the aircraft approached the Pacific Highway from the NE, it was observed to enter a level turn to the left. The angle of bank was estimated to be 20`-30` Almost immediately after the turn was commenced, the aircraft broke into three major sections as a result of structural failure. The wing, which broke into two parts at the centre section, tumbled to earth on a property on the E side of the highway. The cockpit and engine trajectories carried them over the highway, some 200 m beyond the wing ground impact points. The pilot received fatal injuries. One witness reported the aircraft's wing had flapped 'like the wings of a bird' immediately before the in-flight break-up. Weather conditions at the time were reported as overcast at 1500 ft, wind light and variable and visibility in excess of 10 km in fine drizzle. The conditions were suitable for flight under visual flight rules and not conducive to the formation of significant turbulence. It is therefore highly improbable that weather conditions were a factor in this accident. An examination of the wreckage revealed the main carry-through spar had failed in overload from an upward bending force. No evidence was found of any fault in manufacture or of pre-existing deterioration to the spar structure. The aircraft was designed and manufactured for an ultimate strength of approximately 8g+. A level turn of 20`-30` angle of bank would normally apply a loading of 1.06 to 1.16g. The wing was capable of producing aerodynamic loads in excess of 6g at an estimated cruising speed of 100 kts. The witness evidence concerning the flapping of the wings is consistent with the aircraft having entered an oscillating manoeuvre in pitch. Wing loads capable of causing structural failure could be generated in such a manoeuvre. The evidence indicated the aircraft entered an uncontrollable oscillating pitch manoeuvre during which the aerodynamic loads exceeded the structural strength of the wing. The reason(s) for the onset of such a manoeuvre, and the inability of the pilot to minimise the effects of the oscillation, could not be positively established. However, it is recognised that an aircraft with a tailless flying wing configuration that incorporates no sweepback has little damping in pitch and is therefore susceptible to overcontrolling in pitch.

Significant Factors:

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

1. For reasons undetermined, the aircraft oscillated severely in pitch.

2. The severity of the oscillation resulted in a structural failure of the main spar of the wing.

3. The pilot encountered circumstances beyond his control.

Circumstances:

Whilst conducting mustering operations at low speed and altitude over trees, the engine began to run rough. The helicopter was unable to sustain continued flight and the pilot elected to land. During the landing, the rotor blades struck trees and the helicopter landed heavily coming to rest on its side. The pilot was able to crawl to safety after switching the magnetos off, but he was unable to reach the fuel mixture control. The engine subsequently oversped to destruction. The investigations found that the left magneto had suffered an internal failure. The bush supporting the distributor rotor gear had become loose in its housing, allowing the rotor to become mis-timed. During the impact sequence, the magneto earthing wires were fractured which allowed the engine to continue to run despite the pilot switching off the magnetos.

Significant Factors:

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

1. Failure of distributor rotor block bush.

2. Mistiming of one magneto.

3. Forced landing in unsuitable terrain.

As the first student parachutist climbed out on the wheel strut for his parachute descent his main chute deployed prematurely. The parachute risers became entangled with the horizontal stabiliser causing increased drag damage to the stabiliser and a locked elevator. The entangled student and the other student and instructor safely evacuated the aircraft by parachute. The pilot who was also prepared to evacuate the aircraft carried out a series of handling checks and was able to establish a means of controlling the aircraft. He was able to land the aircraft safely on a salt lake with the parachute still attached. The parachutist was using a type of equipment which only requires a 10lb pull to activate the pilot chute. The static line to the pilot chute is tucked under an elastic band to prevent it trailing in the slip stream. If the line becomes loose from the band the slipstream can deploy the pilot chute which in turn will deploy the main chute. The instructor did not see the line work loose but it is probable that this is what occurred. This accident was not the subject of an on-scene investigation.

The pilot was conducting a local flight in the training area. He reported that while in cruise at 3500 feet above sea level, the oil pressure and RPM dropped. He carried out a trouble check but was unable to restore power. He carried out emergency landing procedures. During the landing, with a tailwind component, and only 10 degree flap selected, the aircraft overran the intended touchdown area, struck a fence and the nose gear folded under. The aircraft came to rest at the edge of a swamp. No fault was found with the engine. It was suspected that the loss of power was due to carburettor icing.