The pilot had shut down the helicopter to kill and load meat for a stock camp. After starting and completing the after-start checks, the pilot first entered a low hover. The aircraft was then put into a high hover about 10 ft above the tree tops before a climb was initiated into a wind of 15-20 kts. The pilot reported that as he accelerated through about 40 kts, he noticed a substantial reduction in the manifold pressure reading with the engine RPM at about 3000. The aircraft then began to sink into the tree tops. Some 100 metres further on, the main rotor blades struck a large tree trunk and the aircraft fell to the ground on its right side. The pilot was rendered unconscious at impact, but after regaining consciousness he assisted the surviving passenger from the wreckage and freed the other passenger's leg from under the cabin before dragging him clear. A strip inspection of the engine and turbocharger revealed significant defects. These included the density controller was set below tolerance; a cracked and warped wastegate butterfly; and a sticking wastegate actuator. Physical damage to the engine was attributed to poor engine handling. The cumulative effects of these defects would have reduced the available power output from the engine, but do not in themselves explain the symptoms reported by the pilot. In addition, the power available was sufficient for the pilot to execute a towering take-off. A turbocharger failure would have produced the loss of power experienced by the pilot, but no possible cause or result of such a failure was discovered. The pilot reportedly did not make a significant reduction in power after the high hover, so that it is unlikely that a sticking wastegate caused the problem. The cause of the reported loss of power was not determined.

The helicopter approached the "London Bridge" feature from the west along the coastline at about 400 feet above sea level. It then carried out a wide, right orbit of the feature and descended in an easterly direction as if to position the helicopter for the passenger to photograph "London Bridge" or perhaps to land in the car park. While facing east and still descending through an estimated 200 feet, almost above the feature, at slow forward airspeed, the helicopter began turning to the right without banking. The rate of turn accelerated rapidly. At about the same time an increase in engine noise was heard by witnesses who soon saw the aft section of the tail boom, encompassing the tail rotor assembly and stabilisers, separate from the helicopter. With the tail boom off, the helicopter adopted a steep nose down attitude as it rotated and plummeted. Witnesses estimate that the helicopter rotated through about six complete turns before it disappeared over the cliff edge. At the same time pieces were seen falling from the helicopter. In the soft rock on the lip of the cliff, about 65 feet above the sea, three distinctive rotor strikes were found. Two of the four main rotor blades were torn off at the blade grips probably when the blade tips impacted the cliff. These two blades were lost in the sea. At least one rotor blade hit the upper left rear of the fuselage, probably after striking the cliff. The air intake area, the structural members above the engine bay and the tail boom sustained massive impact damage consistent with main rotor strike(s). The outboard one third of the fourth blade appeared to have been broken off when the helicopter finally impacted hard in shallow, surging seas a few metres west of the cliff base. About three metres of tail boom was also lost in the sea. The fuselage, the rotor systems, the engine, the gearboxes, and the drive-train were examined by engineers. All damage was consistent with overload failure. Except for a small portion of the left rear door and remains of hinge assemblies, all four cabin doors were lost in the sea. The left rear door lower hinge pin was not found, nor was any remnant of the lower hinge bracket. It is unlikely that the hinge pin came out during the accident unless it had been inserted improperly. The only other alternative is that the pin was missing. The hinge pin incorporates a spring loaded bead near its tapered end and a safety tang at the top to prevent it working upwards and out. No structural damage was found in the lower hinge cutout in the fuselage. In contrast, the upper hinge bracket on the left rear door failed through overload, consistent with the door having been thrust upwards about the upper hinge without restraint from the lower hinge, while the door was in the open position. A metallurgical study found that the upper hinge had also previously sustained a partial fracture which was probably present for a long time. The tail rotor blades showed evidence of having sustained impact damage in flight. The only portion of the door frame which was found displayed a dent as if it had been hit by a rotor blade. An indentation on the leading edge of one of the tail rotor blades was consistent with it having hit part of the door latching mechanism. Witnesses saw the tail rotor blades at about the same time that the helicopter began rotating to the right. This would suggest that the tail rotor blades had already slowed down considerably because at normal operating RPM the tail rotor is seen as a blurred disc. It is probable that the left rear door came off during the low speed descent and struck the main rotor blades which spin anticlockwise when viewed from above the helicopter. The door, or fragments of it, were probably flung into the tail boom and into the spinning tail rotor. The tail rotor drive shaft broke from overload, probably at the moment the door struck the tail rotor. Then the tail rotor would have slowed down rapidly due to aerodynamic drag plus the stub of drive shaft flailing within the tail boom. The fuselage would have begun rotating to the right because there was no longer any tail rotor thrust to counteract engine torque. Witnesses heard an increase in engine RPM, probably at about the same time as the anti-torque failure. This is consistent with a sudden removal of the engine load needed to drive the tail rotor especially during low speed flight. The aft section of the tail boom showed evidence of having been struck by a main rotor in flight. This could have come about by the affects of the door impacting the main rotors and disturbing their tip path plane or by the pilot losing control during the anti-torque failure. Once the tail boom separated, the change in the helicopter's centre of gravity would have been outside fore and aft cyclic control limits and the pilot would have lost control. After identifying the anti-torque failure, it is probable that the pilot instigated the rapid descent by entering autorotation in an attempt to carry out the emergency drill. A subsequent experiment with the slam shut doors, as were fitted to this helicopter, found that the rear doors could be slammed shut with minor difficulty despite the absence of the lower hinge pin. With all the latches properly adjusted, the door might remain shut in flight but its alignment may be slightly askew and the door would be more prone to open in flight. About twenty-five minutes before the accident, witnesses saw the left rear door open during the hover/taxiing phase at Warrnambool. The pilot landed the helicopter and shut the door before proceeding to "London Bridge".

Circumstances:

The aircraft was cruising at 1500 feet above ground level when the engine lost power. As the engine stopped there was a cloud of white smoke and a loud noise. The pilot lowered the collective control and as the aircraft entered autorotation, he turned through 180 degrees to make an approach into the only reasonable area. The surface conditions were rougher than the pilot had expected and whilst attempting to reduce forward speed for the landing he misjudged the altitude, and the tail struck the ground. The pilot had not completed an autorotational approach and landing for approximately two years although he had completed an autorotational approach, with power recovery prior to landing, about four months before the accident. The engine failure was caused by a fractured crankshaft. The fracture followed the growth of a fatigue crack in the No. 4 connecting rod journal. It was apparent that the bearing shells fitted to the big end of the No. 4 connecting rod had rotated in their housing and had moved forward to contact the forward fillet radius of the No. 4 connecting rod journal. Fatigue crack initiation occurred as a result of the damage caused by the contact of the rotating bearing shells. The fatigue cracking had occurred during the fourteen-hour period of operation since the last overhaul. Fretting damage on the mating surfaces of the No. 4 connecting rod big end bearing housing indicates that the clamping force achieved by the connecting rod bolts had been poor thus allowing the bearing shells to move. Other deficiencies, in the way in which the engine was assembled and which were not connected with the engine failure, were found. Although some of the deficiencies may have been caused at the time of the crankshaft failure, others indicated that the engine may have been delivered to the operator, following the overhaul, in a defective condition.

Significant Factors:

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

1. It was possible that the engine overhaul had not been completed correctly. Indicated by the deficiencies found during the post-accident investigation.

2. There was a fatigue failure of the crankshaft causing complete engine failure.

3. The pilot misjudged the aircraft's altitude during the termination of the autorotational descent, and he was unable to prevent the aircraft's tail from striking the ground.

4. The landing area terrain was rough and uneven.

At about 50 knots during the landing roll, the pilot discovered that the right wheel brake had failed. The aircraft had swerved to the left when both brakes had been applied. With the rudder control ineffective at low speed, the pilot intentionally ground looped the aircraft to avoid running into the perimeter drainage ditch. The right main gear collapsed and the right wing was damaged as a result of the ground loop. Examination of the right brake unit revealed that the master cylinder was corroded internally, allowing brake fluid to bypass the seal.

Circumstances:

The pilot had been hired to ferry the aircraft to the operator in Western Australia and had landed to refuel at Elliot. While on the ground, he agreed to deliver a box to the Wave Hill police station and stowed it, unrestrained, on top of a jerry can in the unoccupied seat. The aircraft was reportedly fitted with permanently installed dual controls. On approach to land at Wave Hill Station, the box shifted, fell onto a swag on the floor and restricted the movement of the cyclic control. The pilot was thus unable to manoeuvre to avoid a cattle crate stand and the tail rotor struck one of the rails. The helicopter then landed heavily on its skids.

Significant Factors:

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

1. Inadequate preflight preparation - improperly stowed cargo.

2. Unrestrained cargo moved and caused restricted movement of the flying controls. This accident was not the subject of an on-scene investigation.

The pilot reported that shortly after establishing cruise at 300 feet above ground level the aircraft suddenly began to shake as if something had been thrown into the propeller. The engine stopped shortly afterward and, after establishing a glide and making a radio call, the pilot attempted to restart the engine. The engine would not turn over. A landing amongst scattered scrub and clumps of grass was made. Examination of the propeller disclosed that one blade had failed due to a large fatigue crack adjacent to the mounting holes in the blade root. The blade had then severed a bracing wire running between the wing trailing edge and the fuselage behind the propeller. The wire had become entangled in the other propeller blades. The propeller blades were constructed of fibreglass strands in a resin matrix covered with a layer of carbon fibre cloth. Visual and x-ray examination of the blades indicated that the strands were not uniform in direction in the area of the blade roots, some sections had no strands at all, and there were voids in the matrix. These faults reduced the strength of the blades in that area. All blades showed evidence of fatigue cracking near the mounting holes. The holes had been made by multiple drilling. The blade manufacturer advised that he was aware of the faults and had altered the production method. He had advised all owners of similar blades of the deficiencies. This accident was not the subject of a formal on-scene investigation.

Circumstances:

On DEPARTURE from Bankstown, the landing gear retracted normally. On selection of gear down in the circuit at Hoxton Park, the pilot could not obtain a green gear down light. He observed that the main gear appeared to be fully extended. He carried out the manual extension procedures as set out by the manufacturer but was still unable to obtain a green light. He returned to Bankstown where an inspection from the tower and engineering advice indicated that all three legs appeared down and locked, although the nose gear forward doors had not closed. The pilot made a normal landing on the mainwheels, holding the nosewheel off for a short distance, and then gently lowering it as speed reduced. Soon after contact with the runway, the nose gear collapsed. The investigation disclosed that the retractable step hinge point was rusty with no sign of lubrication, and the retract cable was found to be tight in its outer cable. The retraction cable had also formed a loop within the nosewheel well, and it was this loop which had fouled the down lock mechanism, preventing the nose gear from locking down. During retraction tests it was noted that the step remained in the retract position even with the gear down and locked. The step should normally extend and retract with the nose gear. The aircraft had a history of landing gear defects and maintenance organisations which had worked on the aircraft seemed unaware of the correct performance and operation of the retractable step. The overall standard of landing gear maintenance and lubrication was inadequate. This accident was not the subject of a formal on scene investigation.

Significant Factors:

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

1. Inadequate maintenance of the landing gear system.

2. Inadequate preflight inspection of aircraft by pilot.

Circumstances:

The pilot reported that he was making an adjustment to the fuel selector, at the top of climb, when he noticed a lower-than-expected reading on the right outboard fuel quantity gauge. Suspecting a loose fuel cap, he advised the co-pilot to carry out a visual inspection of the right wing area with a torch. Although the fuel cap appeared to be seated properly, the decision was made to return to the DEPARTURE runway and carry out a more thorough investigation. During the landing roll the right engine lost all power, and the pilot attempted several unsuccessful restarts. At the end of the runway the aircraft was turned tail into wind, and another restart was attempted. As the engine started the co-pilot observed flames under the right wing area and activated the engine fire extinguisher. The co-pilot then exited the aircraft to investigate and returned immediately to inform the pilot that the aircraft was on fire. Both engines were shut down and the pilots exited the aircraft. The investigation showed that the rubber fuel cells inside the right wing had collapsed upward towards the fuel filler inlet. The fuel drain fitting located directly behind the right engine exhaust was missing. Rubber fuel cells are known to collapse in this manner when a fuel filler cap comes loose in flight. The fuel is then sucked out through the filler neck into the low-pressure area above the wing. This occurs faster than the vent system can cope, causing the inner cell to collapse. In this case, the fuel caps were found properly secured. However, the rubber sealing ring on the right fuel cap was perished and cracked in several places. The steel mating ring around the filler neck, which accepts the fuel cap, was also badly corroded over the entire sealing surface area. It is probable that the fuel syphoning began as a result of the poor seal around the cap. The syphoning would have been assisted by the tanks having been filled to the top of the filler neck for the flight. (The tanks had not been filled to this level for at least two years.) The outboard fuel (water) drain fitting attaches to a section of the fuel cell which protrudes through the lower wing surface. This fitting is located immediately behind the right engine exhaust outlet. When the fuel cell collapsed inside the wing, the fitting was unable to pass through the wing cut-out and was pulled from its attachment point on the cell. This then allowed fuel to flow freely into the airstream directly behind the engine exhaust. When the engine start was attempted with the aircraft tail into wind, the stream of fuel was blown directly back against the exhaust outlet. The investigation confirmed the right outboard exhaust as the ignition source for the fire.

Significant Factors:

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

1. Inadequate maintenance of the fuel filler cap.

2. The fuel tanks had been filled to the top of the filler neck.

3. Fuel from the right wing tanks had siphoned overboard, causing the inner fuel cells to collapse.

4. The pilot attempted to start the right engine with the tail of the aircraft into wind.

5. Exhaust gases from the right engine ignited the fuel draining from the tank.

Whilst on a training flight, the pilot attempted to turn the aircraft through 360 degrees as part of an autorotative descent that was commenced at 470 feet above ground level. During the turn the pilot looked inside the aircraft to check the rotor RPM, and on looking outside again he noticed that an excessively high rate of descent had developed. A roll was initiated to bring the aircraft out of the turn, and power was applied. However, the main rotor blades began making the sound characteristic of low rotor RPM and, as ground impact appeared imminent, the pilot attempted a run-on landing. On impact the aircraft was not aligned with the intended landing direction and after sliding approximately 10 metres the right skid collapsed. The main rotor blades impacted the ground, and the upper area of the bubble canopy and the aircraft rolled to a halt on their sides. The pilot had had a lay-off from flying for 4.5 months. He then completed a check flight with the Company Chief Pilot three days before the accident flight. This check flight included a 360 degree practice autorotation from below 500 feet above ground level. Expert opinion was that a person who had not regularly practised this manoeuvre would have difficulty completing it successfully every time, if commenced from below 500 feet above ground level. When the pilot attempted the manoeuvre it was 15 minutes before last light and the eastern sky was losing its definition. As the aircraft rotated in its turn, the pilot would have been presented with a rapidly changing quality of visual cues being presented to him which would have added to the difficulty of accurately flying the manoeuvre. The pilot was too late in his attempt to recover from the manoeuvre.

Circumstances:

The accident flight was intended to recover the aircraft which had been force landed that morning, due to a massive oil loss accompanied by a propeller overspeed. After take-off, the pilot left the landing gear down and climbed the aircraft over land to 1500 feet as he checked the engine instruments. He reported an initial increase in cylinder head temperature, but this was attributed to the landing gear-down climb by the engineer who was following in a helicopter. A short time later, the pilot reported rough running and then the engine vibrated and seized. An attempt was made to reach a clear area on an island, but despite retracting the landing gear, the pilot was forced to land the aircraft in a mangrove-covered tidal plain. The pilot levelled the aircraft over the tree-tops and stalled before cutting through the trees. A heavy ground contact was felt, and the aircraft came to rest in about 13 metres. The pilot egressed unaided after closing down the aircraft. The engine was recovered for inspection. Massive internal damage from a progressive failure of components, due lack of lubrication, is considered to have been the most probable cause of the engine failure. This is traceable to the previous occurrence that day when a massive oil loss and overspeed occurred. Inadequate inspection of the aircraft following the previous unserviceability including a failure to comply with the manufacturer's recommendations, allowed the aircraft to depart on the recovery flight in an unairworthy condition.

Significant Factors:

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

1. Inadequate inspection of the aircraft following a previous major oil loss and propeller overspeed.

2. Forced landing over unsuitable terrain following engine seizure. This accident was not the subject of an on-scene investigation.