Circumstances:

The pilot was expecting to make an early morning DEPARTURE but was confronted with adverse weather conditions and low cloud. He was advised by another pilot that these conditions were expected to improve later that morning, but he decided to depart immediately and assess the weather as the flight proceeded. After flying in a westerly direction for several minutes it became obvious to the pilot that visual flight could not be maintained, so he elected to return for a landing. Re-entering the circuit area the low cloud and poor visibility required the flight to continue close to the ground, and the pilot misjudged the turn onto final. He abandoned the landing and joined a low left hand circuit for the reciprocal runway. While turning onto a close final leg, the left hand wing contacted a six metre high telephone wire located across the approach path approximately 300 metres from the runway threshold, causing the aircraft to lurch violently to the left and impact the ground heavily.

Significant Factors:

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

1. The flight was initiated and continued in adverse weather conditions. This accident was not the subject of an on-scene investigation.

The pilot was to conduct a charter with passengers from Sydney to Wollongong, Nowra, Canberra and return to Sydney, departing Sydney at about 10.00am. Earlier that morning he positioned the aircraft at Sydney and had it refuelled. When the passengers arrived he explained that the weather in the various destinations was very poor and that there was a possibility they may not be able to land. However, he was prepared to give it a try. As the passengers were pressed for time, they could not afford to take a chance with the weather and so they decided to drive. They told the pilot that if he could land at Wollongong later that day they would continue the flight with him. However, they impressed on him that there was no pressure for him to depart immediately as they would not be in Wollongong for several hours. After driving for a short time, the passengers decided that the weather did not appear as if it would improve, and believed that it would be better to complete the journey by car. They contacted the charter company by phone to cancel the charter, but the pilot had already departed. The flight to Wollongong appears to have proceeded normally where the pilot reported commencing an NDB approach, and would call again at a specified time. This was the last message received from the pilot. Witnesses on the ground at Wollongong, and on a yacht 20 nautical miles to the east of Wollongong reported hearing an aircraft flying at approximately 1000 to 2000 feet in the low cloud and rain. There were no other known aircraft in the area. Later that day a helicopter discovered wreckage debris in the sea, which was confirmed as being from the aircraft. The search was discontinued due to very poor weather and visibility, and cancelled two weeks later when further efforts failed to locate any trace of the aircraft.

Circumstances:

The pilot reported that following a normal landing, as the aircraft turned left onto the taxiway, the right main landing gear collapsed. Subsequent inspection revealed the right main down lock bell crank pivot bolt had failed in shear, and the forward pivot lug had failed in bending overload. This is consistent with what would be likely to result from excessive down lock tension. After repairs had been effected, an engineering report determined that the down lock tension was significantly higher than specification. However, the engineering report was not conclusive as the original components could not be used for testing.

Significant Factors:

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

1. Probable misrigging of the right main gear down lock. This accident was not the subject of an on-scene investigation.

The aircraft struck a bird while cruising at 1500 feet. The bird shattered the windscreen and struck the occupants of the aircraft before coming to rest in the rear of the cabin area. The pilot reported that loss of the windscreen reduced aircraft performance to the extent that, while flying at about 1000 feet with cruise power set, the indicated airspeed was 65 knots compared to the normal 90 knots. The bird was later identified as a wedge tailed eagle. It had a wingspan of almost two metres.

The aircraft is a prototype designed for long distance and altitude record attempts. The pilot reported that after touchdown the nosegear retracted and this also resulted in the maingear collapsing. The gear collapse resulted from undetected stiffness in the nosegear downlock mechanism. A number of modifications to the system are to be incorporated.

The pilot was engaged on his third solo flight and had been authorised to conduct a series of circuits and landings. During the first landing the aircraft bounced and subsequently struck the ground in a nose-low attitude. The nosegear collapsed and the aircraft came to rest on the grass to the left of the sealed runway.

The pilot had recently obtained a Commercial Helicopter Pilot Licence, and had been undergoing training for the issue of a cattle mustering endorsement. He had obtained permission from his employer to use the helicopter for a local flight. The approval was given on the understanding that operations were confined to normal procedures, and were not to include low flying. It was the pilot's intention to conduct two short flights, carrying two other persons on each occasion. The helicopter was given additional pre-flight inspections, following reports of vandalism to other helicopters in the area. No evidence of any vandalism was found and the pilot carried out a short solo flight to further verify the serviceability of the aircraft. The first two passengers then boarded the aircraft. About 30 minutes after DEPARTURE, the aircraft was observed operating, apparently normally, in a designated low flying area. It was then observed flying towards the south east at about 10 metres above the ground. The aircraft then entered a steep turn to the left, but after turning through some 200 degrees the main rotor blades struck the ground. The aircraft subsequently struck the ground heavily and cartwheeled around the rotor arc. A fierce fire broke out and engulfed the wreckage. A detailed technical investigation did not reveal any pre-impact defect or malfunction of the helicopter which might have contributed to the accident. There was also no evidence that the pilot had suffered any sudden illness or incapacity which might have affected his ability to control the aircraft. There was no known operational reason for the aircraft to be flown close to the ground, and it was possible that the pilot was demonstrating mustering techniques to his passengers. The wind at the time of the accident was from the south east at between 11 and 18 knots. The helicopter had been loaded near to the maximum allowable weight, and had not possessed sufficient performance to maintain level flight during the turn towards the downwind direction. The pilot had only limited experience in operations at high all-up-weight levels, and had evidently not realised the effect the increased weight had on the aircraft performance, particularly when turning downwind.

The student pilot was returning from her second solo flight to the training area. The aircraft bounced on touchdown and the pilot attempted to recover, but the aircraft bounced a second time and the nose gear failed. Wind was reported as nil. This accident was not the subject of an on scene investigation.

At his destination, the pilot reported a gear malfunction and use of the emergency gear extension system was unsuccessful. The pilot returned to Darwin and carried out a wheels up landing. Investigation revealed that the left hand nose steering cable had worn through the hydraulic gear extend line. This cable had been routed too close to the hydraulic line during the repair of damage from a prior occurrence.

The pilot was conducting a flight from Diamond Beach to Cooma. Approaching Hoskinstown the aircraft's rear engine suffered a loss of power and smoke appeared in the cabin. The pilot immediately shut down the rear engine and feathered the propeller. Because the symptoms indicated that a fire was burning in the rear engine compartment, the pilot decided to land as soon as possible, and prepared for an emergency landing into a paddock. During the approach the smoke disappeared from the cabin, so the pilot concluded that the fire had extinguished itself and discontinued the landing. He then diverted to Canberra, using the front engine only, where he landed safely. An examination of the rear engine compartment revealed that a large section of the left-hand exhaust stack had separated in flight. Hot exhaust gases, now directed into the rear engine compartment, burnt a hole through the lower cowl, distorted the firewall and burnt the insulation from electrical wires including the low tension ignition leads. The bare ignition leads then "shorted out" causing the engine to fail. The source of heat having been removed prevented the fire from becoming self-sustaining. Cracks of about 18 cm in length had occurred along either side of the lower welded seam from the muffler attachment flange. The forward crack propagated around the exhaust stack, through 180 degrees, and returned back to the muffler attachment flange, paralleling the lower seam. This allowed the section of exhaust stack to separate. Expert opinion suggests that the cracks should have been evident for a considerable period of time, having originated from normal thermal fatigue and exhaust gas flow erosion. The aircraft had been subject to a major inspection a short time prior to the flight. The organisation which performed this inspection advised that there had been no evidence of exhaust gas leakage, or cracks visible to the naked eye at that time.