The pilot reported that he encountered severe turbulence at 1500' and that he reduced power to slow to the turbulence penetration speed. When the aircraft cleared the rough air the throttle was advanced, however, the engine stalled. The aircraft was established in a glide configuration and a paddock was chosen in which to land. The approach was flown at a speed in excess of that normally used for a powered approach resulting in the tailwheel contacting the surface prior to the mains. When the mainwheels contacted the paddock the struts bent and allowed the propeller to strike the ground. The aircraft could not be controlled during the ground roll and it skidded through a fence and onto a roadway. This accident was not the subject of an on scene investigation.

Circumstances:

The aircraft was engaged in a medical evacuation flight carrying an injured crewman from a ship located west of Augusta. During the turnaround at Augusta the pilot noticed that one corner of the polyurethane covering on one tail rotor blade was lifting. After consulting the company engineer in Perth the pilot cut the loose material from the blade and continued with the flight to Perth. Slight vibration was felt after approximately 30 minutes and 15 seconds later the vibration became severe. The pilot carried out a precautionary landing. An inspection of the tail rotor blades indicated that a significant amount of the polyurethane covering on the blade not modified by the pilot had been lost. The blade's polyurethane covering had been replaced approximately 4 hours before the occurrence. The bonding process used, although in accordance with the manufacturer's recommendations, was defective. The manufacturer had developed a new process prior to the occurrence, however, details of this had not reached the Sydney based overhaul facility at the time the cover was replaced.

Significant Factors:

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

1. The design of the polyurethane replacement process used on the failed blade was defective.

The pilot reported that he made a short field approach to the 080 degree strip in a 10 knot easterly wind. He said that on short final approach some sink was encountered which resulted in the aircraft touching down short of the threshold. The pilot believed that touchdown was normal for a short field approach but the wheel marks on the strip suggested that it may have been heavy. When the aircraft touched down, the right main gear tracking arm (P/N 105-810021-4) broke. This resulted in the wheel assembly detaching. The aircraft skidded to a stop after rotating to the right through about 170 degrees. The broken tracking arm was subjected to microscopic examination which determined that it had failed due to overload. There was no evidence of any fatigue or pre-existing damage. In addition, the damage to the wings was also consistent with a heavy landing.

The pilot was landing the aircraft in gusty wind conditions. As the aircraft was flared for landing, it touched down heavily nosewheel first, and bounced. Power was applied to assist in regaining control. During the second touchdown the nose dropped, the nosegear collapsed and the aircraft overturned. After the accident the pitch trim devise was found to be in a nose-down position. The pilot advised that he usually selects a nose-up position for landing. This accident was not the subject of an on-site investigation.

The aircraft was established on final by the pilot under check. A 5 knot downwind component prevailed. The flare was commenced higher than is normal and the airspeed decreased below the optimum. The pilot did not react to prompting by the the check-pilot but, at about 20 feet, retarded the throttles. The aircraft struck the runway heavily in a left wing low attitude and the left main and nose landing gear was torn off. Command responsibility for the flight was not discussed and the check-pilot was under the misapprehension that his role was only that of safety-pilot. Due to flight rescheduling, the pilot under check slept for only two and a half hours prior to commencing duty. The auto-pilot was unserviceable and the pilot under check flew the aircraft by hand for most of the four flight legs. During the last leg the check-pilot twice simulated an engine failure. The second failure was simulated on final approach at about 7 DME. Power was reinstated shortly afterwards and the approach continued normally until close to the threshold. At this time the pilot under check had been on duty for five and a half hours and the check-pilot for over twelve hours. Overseas research has shown that subtle errors in visual perception may be induced by an event which causes stress, and that this condition may persist for several minutes after the event. Fatigue may aggravate the problem. The errors in perception are the result of changes in focal length of the lens of the eye caused by the physiological effects of the stress resulting from the event. The experimental research and information from accident data has provided evidence that the effect of the changes in focal length may cause a pilot on final approach to perceive a runway to be on a higher plane than it actually is. In this case, with the particular combination of factors prevailing at the time, it is possible that the imposition of a simulated engine failure on approach within a few minutes prior to the final landing of a long and fatiguing night's operations caused a stress reaction in the pilot under check. The level of stress induced in this fatigued pilot may have been sufficient to cause the kind of perceptual error described above. The runway would thus appear to the pilot slightly higher than it actually was. His judgement of flare height, being based on this false perception, would therefore be incorrect.

After about four hours flying, the pilot decided to return to Corryong to land. Because the aircraft was too low he tracked towards a valley in an attempt to find lift. The attempt was unsuccessful and the pilot selected a sloping area on which to carry out an outlanding. Shortly after touchdown one wing struck a small bush and the aircraft groundlooped. The pilot was inexperienced in mountain soaring. He had been operating in the vicinity of a suitable landing area, but left this area with insufficient altitude available to glide to the next suitable landing area.

Superphosphate spreading was being carried out, with the aircraft uplifting one tonne loads about every 6 minutes. Fuel endurance with both tanks full was approximately 2 hours. The pilot was conducting his 25th takeoff for the day, about one hour after refuelling. Witnesses observed that the aircraft did not become airborne at the usual point, two-thirds of the way along the 675 metre strip. Lift-off finally occurred at the end of the strip, but almost immediately afterwards the aircraft clipped a fence. It was seen to sink slightly, before climbing at a steeper than normal angle until some 250 metres beyond the fence. At this point the nose dropped suddenly and the aircraft dived into rising ground in a steep nosedown attitude. Fire broke out on impact and consumed much of the wreckage. Preliminary investigation revealed that the fuel selector was in the "off" position. This had been the first occasion that the pilot had flown this particular aircraft. The fuel selector in this aircraft was different to that in the other Beaver the pilot had operated. In the previous aircraft, rotating the fuel selector through 180 degrees anti-clockwise changed the selection from the rear to the forward fuel tanks. In the accident aircraft, a similar movement of the selector changed the selection from the rear tank to the "off" position. This difference had not been brought to the pilot's attention, and it was possible that he had not thoroughly familiarised himself with the aircraft prior to commencing operations. It was considered likely that the takeoff had been commenced with the fuel selector positioned to the almost empty rear tank. During the takeoff roll, the fuel low quantity bell and associated light had activated, and the pilot had changed the fuel selector by feel, while continuing with the takeoff. With the fuel supply turned off, the engine had failed from fuel starvation, and the aircraft had subsequently stalled at too low a height above the ground to permit recovery before impact.

The helicopter, on a sightseeing flight, had completed a circuit of Cairns Harbour before climbing-out towards Green Island. A noise was heard from the rear of the helicopter, accompanied by a rotation to the right. An autorotation was initiated and the helicopter landed on the nearby mudflats. The right skid-legs collapsed on touchdown, which resulted in the helicopter rolling onto its right side. The occupants evacuated and were rescued by a fishing boat. The tail rotor and part of its associated gearbox had separated from the helicopter. The pilot regained directional control when an autorotation was commenced. However,as the helicopter was over water he attempted to carry out a zero forward speed landing, rather than a "run on" type which is the procedure recommended by the manufacturer when loss of tail rotor effectiveness occurs. Thus, when collective pitch was applied to reduce the rate of descent prior to landing, the helicopter again commenced to rotate and touchdown occurred whilst turning to the right. The components which had become detached in flight were not recovered, thus the reason for the failure of the assembly could not be positively determined. However, specialist examinations indicated that the fracture was due to a limited number of high stress cycles, this is not consistent with normal in service loads.

The pilot was preparing to depart from a strip which was only marginally longer than the minimum length required. He reported that when take-off power was applied, an overboost warning light illuminated. Although a considerable power reduction was required on the right engine before the light extinguished, the pilot continued with the take-off attempt. He advanced the right throttle to match the position of the left lever, but as the aircraft became airborne it struck the boundary fence and the left mainwheel was dislodged. The pilot elected to return for a landing at the strip. During the landing roll, the left gear leg collapsed and the aircraft ran off the side of the strip. No fault was subsequently found with the engines and associated systems of the aircraft. The overboost warning light system fitted to the aircraft type is characterised by a significant lag during power reduction. The normal method of re-setting power under these circumstances is by reference to the manifold pressure gauges. Although the strip was marginal for the intended operation, the engines were not advanced to a high power setting before the brakes were released.

The pilot was making a night landing approach. Late in the flare a thump was heard, and shortly after touchdown the nosegear collapsed. The aircraft came to rest on the strip 390 metres further on. It was discovered that a large kangaroo had struck the nosegear, and that a number of other kangaroos were in the immediate vicinity.