Circumstances:

The pilot had not landed at the airstrip previously. He made his approach to the 650 metre long airstrip which had a slight uphill gradient in the landing direction. On final approach the aircraft was undershooting and the pilot applied power. Touchdown occurred at the start of the airstrip and the wheel marks showed that all three wheels had touched down together. Immediately after touchdown, the nose gear collapsed, and the aircraft overturned. The distance from the touchdown point to where the aircraft came to rest was 25 metres. The nose gear collapse was caused by an overload failure of part of the downlock mechanism. In addition, the left main gear leg was bent upwards. This damage was consistent with a heavy landing.

Significant Factors:

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

1. The pilot misjudged the final stages of the approach.

Circumstances:

Nearing the completion of a survey flight over a mining prospect, the pilot asked the passengers if they would like to see a crop-dusting manoeuvre. As the passengers had no objection, the pilot flew the helicopter through a steep 180 degree climbing turn to the left from a height of about 300 feet. During recovery from the ensuing dive, the aircraft struck the ground heavily and came to rest inverted. The surviving passenger was thrown from the aircraft after the initial impact. There was no evidence of any mechanical defect in the helicopter which may have contributed to the accident.

Significant Factors:

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

1. The pilot attempted a manoeuvre at a height from which he was unable to recover safely.

Circumstances:

The pilot did not submit flight plan details, but departing Dubbo he advised tracking for Goulburn. No further communication was received from the aircraft, although there was evidence to suggest an intention to proceed to Bega with an intermediate landing at Wollongong. Approximately 80 minutes later, witnesses in the Fitzroy Falls area observed an aircraft fitting the description of VH-MCO, flying very low in various directions, at times obscured by cloud which had enveloped much of the area's higher terrain. Witnesses later heard a noise which caused them to believe that the aircraft had crashed. The area at the time was under the influence of a moist south easterly air mass, with cloud and showers along the coast and adjacent ranges extending to the western slopes of the Great Divide. An extensive air and ground search located the aircraft almost 48 hours later, approximately 100 feet below the level of a ridge. The aircraft had struck trees, which removed the right wing and outer left wing, before coming to rest under a large over-hanging rock ledge. The aircraft was reduced to non-survivable dimensions. There was no evidence of any pre-impact defect affecting the aircraft, and the damage sustained was consistent with the aircraft being in controlled flight at impact. No evidence was found to indicate that the pilot was either qualified or experienced in the conduct of flight in Instrument Meteorological Conditions.

Significant Factors:

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

1. The pilot exercised poor judgement by continuing flight into weather conditions in which he was not able to maintain the visual reference necessary to ensure adequate terrain clearance.

The flight was to survey stock and cull buffalo in an area south-west of the station homestead. After the helicopter failed to return by nightfall, the authorities were notified and a search initiated. The wreckage was located three days later. On-site investigation revealed that the main rotor blades had clipped some small upper branches on a 14 metre high tree before contacting the ground 19 metres further on. The helicopter impacted the ground while banked about 35 degrees to the right and in a nose down attitude of about 35 degrees, but with a flight path substantially closer to horizontal. It then rolled to the right and came to rest against a tree. A severe fire destroyed the cabin/fuselage area. A detailed examination of the engine was not possible because of the extent of fire damage. However, no indication of failure of any major component was noted. Damage to the main rotor blades and ground impact marks from the blades indicated that the blades were being driven by the engine at impact. The state of the tail rotor system indicated that it was intact and also under power at impact. The branches struck by the main rotor blades prior to impact were of insufficient size to have affected the blades or their flight characteristics. The attitude of the helicopter at impact was uncharacteristic for a rotary winged aircraft and indicated that it might not have been under control during the final stages of the flight. This could have been caused by a flight control problem or by some form of pilot incapacitation. Post-impact fire damage to the cockpit/fuselage section precluded a complete examination of the flight control system. No assessment could be made as to the likelihood of pilot incapacitation. A broken engine cooling fan drive belt was found between the tree struck by the main rotor and the initial ground impact point. The other belt was located within the wreckage in its correct position. It could not be established whether the belt was broken and thrown from the helicopter during the impact sequence or whether the belt fell from the helicopter prior to impact. In another recent accident involving the same type of helicopter, the blades on the engine cooling fan had failed. One blade had been thrown against the collective pitch control rod, almost completely severing the rod. Had fan blade failure occurred in the subject accident, (the broken drive belt could indicate this), and a collective pitch or cyclic control rod been struck and severed by a blade, loss of control of the helicopter could have resulted.

During the approach to land at Ord River Station the Pilot in Command (PIC) discovered that throttle movement was restricted within the range 18 to 23 inches of manifold air pressure. After considering the various alternatives the PIC elected to return to Kununurra and attempt a landing. The PIC sought advice from the company Chief Pilot before attempting a landing. Following a practice circuit, to determine the minimum approach speed obtainable, the Chief Pilot instructed the PIC to repeat the circuit and to close the mixture at 300 to 400 feet on final approach. The PIC flew a slightly modified circuit, which involved a longer, flatter final approach and closed the mixture, as instructed, at 300 feet on final approach. Shortly after closing the mixture the PIC realised that the aircraft would not reach the runway and she attempted a landing in a grass area short of and to the left of the threshold. During the landing the aircraft collided with a ditch which had been hidden from the PIC's view by the grass. Movement of the throttle was restricted because a throttle linkage pin, which had been fitted incorrectly, was binding against a loose induction air box. The bolts holding the induction air box in place had not been secured correctly at the last servicing. Three of the four retaining bolts were found lying in the engine bay. The PIC was inexperienced in commercial operations and the Chief Pilot was known to exercise "positive" supervision over the company's operations.

Circumstances:

The pilot was commencing a practice flight in preparation for a 600-kilometre soaring competition task. The weather was fine with a north-easterly wind of 15-20 knots and a temperature of approximately 40 degrees Celsius. Following line-up, the pilot was delayed for approximately fifteen minutes before his aero-tow became available. He then advised the tug pilot that a climb speed of 65 knots was acceptable. The subsequent tow initially appeared normal although observers at the airfield noticed some apparent roll instability. At approximately 1000 feet above ground level (agl) the tug pilot detected thermal activity and began a left orbit to regain the area of lift. With the turn almost completed the right wing was violently "kicked-up" as the aircraft re-entered the area of lift. The tug pilot corrected the upset checked that the glider was not affected and continued the left turn. Approximately five seconds after the upset at about 1300-1500 feet agl the glider released. Observers reported that the glider had banked steeply to the right while apparently still under tow. Following the tow release the angle of bank increased past the vertical the nose dropped steeply, and the glider entered a spiral dive from which it did not recover. It struck the ground in an almost vertical nose-down attitude. The investigation was unable to find evidence of any pre-existing structural or system defect. Pilot medical evidence is inconclusive. The reason the aircraft entered an abnormal flight manoeuvre at an altitude from which recovery should have been possible could not be determined.

Significant Factors:

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

1. Control of the aircraft was lost following tow release. The cause of the loss of control was not able to be determined.

The aircraft was cruising normally at 7000 feet when the engine failed without warning. The pilot carried out checks and attempted to restart the engine without success. During the ensuing forced landing the pilot prematurely turned off the master switch, therefore, the wheels did not extend when he selected gear down. The engine failure was caused by the separation of crankshaft idler gear teeth due to high cycle low stress fatigue which had initiated from pre-existing overload cracks at the base of the teeth.

The pilot was requested to conduct an aerial survey in the Mount Bundey area, however, he evidently misunderstood the instructions and flight planned to Mt Bundey Station. This strip was 74 kilometres south-west of the passengers' expected destination. During the flight the front seat passenger, who was also a pilot, became concerned and questioned the pilot at length as to their route. Because of the confusion, and deteriorating weather conditions, the pilot decided to continue and land at the Station strip. A normal landing was subsequently carried out. The pilot then discovered that although the strip was 1100 metres long, a washaway had reduced the usable length to about 700 metres, and this was covered by long grass. After ascertaining the passengers' exact requirements, the pilot prepared for take-off. Acceleration was sluggish because of the long grass, and the stall warning was sounding continuously as the aircraft became airborne near the end of the strip. It failed to climb away, and collided with trees and fences before coming to rest. The aircraft Performance Charts indicated that a strip length of 840 metres was required for a safe take-off. It is likely that the pilot's performance was degraded because he was suffering the effects of a cold. The task had been allocated to him at short notice, and he was under some pressure from the passengers.

While conducting parachute dropping runs from 5000 feet the pilot heard a loud bang from the engine and saw an object ejected through the top engine cowling. The windscreen was immediately covered with engine oil and the engine lost power. The parachutists abandoned the aircraft, and the pilot made a forced landing in a field of young wheat. The field sloped downwards in the direction of the landing roll, and the aircraft nosed-over when the mainwheels intersected a shallow ditch while wheel brakes were being applied. Investigation revealed that the number 4 connecting rod had failed in fatigue across a big end arm. The fatigue had multiple origins on both the outside and inside of the arm, and propagated through approximately 95% of the cross- sectional area. The fatigue initiated from the inside of the big end bore revealed characteristics indicative of high cycle low stress fatigue, while the fatigue commencing from the outside of the arm propagated through high stress low cycle fatigue. The join between the two lines of propagation ran parallel with the bore. The other big end arm had 4 distinct fatigue initiations, one con-rod bolt had failed in overload with distinct signs of necking, while the other bolt remained attached to the cap and remaining part of the big end arm. The No.4 slipper bearing was reduced to a large quantity of severely deformed cold-worked fragments. Detailed metallurgical examination of the failed bearing did not disclose the cause of the failure. The oil filter was clogged with deposits and oil sludge. The bypass and pressure relief valve cavities contained similar deposits. The engine oil had the appearance of dirty used oil. However, laboratory analysis suggested that the oil had changed very little when compared with unused oil. The spark plugs were found to be oily, fouled and heavily deposited by carbon and lead. The aircraft had only flown 6 hours since the previous 100 hour inspection. This inspection should include the inspection of the oil filter, changing of the engine oil and servicing of spark plugs. The condition of the spark plugs was inconsistent with 6 hours of flight time. Approximations of the length of time for which the oil and plugs had been in use was not determined. Examination of the stripped engine disclosed that the oil passages were free, and no components showed signs of oil starvation. The cause of the bearing failure was not established. The aircraft had flown approximately 16 hours between a periodic inspection on 24.6.85 and the next periodic inspection on 1.10.87, and approximately 6 hours between the latter inspection and the accident on 3.10.87.

An aircraft maintenance engineer, who assisted the gliding group with maintenance aspects, was making a video movie of the glider operations. He was seen to be standing to the right-hand side, and well clear of the strip, near to the point where takeoffs were commenced. During the circuit by the particular glider, he moved to the edge of the strip to film the approach and landing. The colour of his clothing blended in with the high clumps of grass and general colour of the terrain, and the pilot did not detect his presence. When looking through the viewfinder of the camera, the photographer would have been led to believe that the glider was well clear of him. While panning the camera to film the landing run, he was struck on the neck by the wing of the passing aircraft.