The pilot was hovering the helicopter at about 60 feet above ground level and about 30 feet above a large tree, when the engine began to lose power and the aircraft commenced to vibrate. The pilot was unable to maintain height with the power that was available and he lowered the nose and flew clear of the tree. At this stage the rotor RPM began to decrease. The pilot selected the only clear area and attempted to land the aircraft. He used the collective pitch control in an attempt to cushion the landing but overpitched the main rotor blades at approximately 10 feet above the ground. The aircraft landed heavily, bounced forward 5 metres and collided with a large tree. The technical inspection revealed that the most probable cause for the loss of power was the breakdown in performance of the spark plugs of number 4 cylinder, due to a build-up of lead fouling. The reason for the fouling in this cylinder and not in the others was not determined. There is an inherent danger in stock mustering with helicopters in that there could be an engine failure or loss of power at a low altitude which will preclude an autorotational descent. On this occasion there was a narrow safety margin for the operation due to the ambient temperature and the aircraft weight, which meant that any loss of power required a forced landing.

The pilot was departing a confined pad amongst some small trees. He made a vertical take-off to about 20 feet and then commenced forward movement. The aircraft then began to descend and the pilot increased the collective pitch. The blades entered an overpitched condition and during the subsequent attempted landing the main rotor struck a tree. The pilot had flown in and out of the DEPARTURE pad a number of times, on the day of the accident, without encountering any difficulty. Immediately prior to the accident he had refuelled the aircraft to what he believed was approximately half tanks. Subsequent investigation indicated that the tanks were three quarters full. Temperature at the time of the accident was about five degrees above that for the pilot's earlier flights. The pilot was aware that a power check should be carried out at each lift off but he did not check the excess power available on this occasion. When the aircraft moved from the hover into forward flight there was insufficient power available to maintain rotor rpm when the pilot increased the collective pitch angle to stop the descent. It is possible that the terrain and wind conditions may have caused some mechanical turbulence which could have added to the amount of power required to transfer from the hover to forward flight.

Circumstances:

The aircraft was loaded close to its maximum all-up weight and departed from runway 24. The take-off was normal, and the aircraft was airborne within 500 metres. After take-off, a right turn was commenced which is normal procedure to avoid the rising terrain. The aircraft was apparently performing normally and climbing at about 65 to 70 knots. However, approaching a row of pine trees, it began to lose height. Despite the pilot maintaining the aircraft in the climb attitude, and using full engine power, the aircraft continued to lose height until ground impact. Although fire rapidly developed after impact the pilot successfully assisted the passengers to evacuate. No pre accident defects were found with the aircraft which could have contributed to the accident. At the time of the accident, a low pressure of 995 hPa was situated over the area. This combined with the surface temperature of about 28 to 30 degrees Celsius to produce a density altitude of 4650 feet at the airfield which is 1850 feet above sea level. The weather pattern was also producing gusty winds and mechanical turbulence over the surrounding hills. A combination of high-density altitude and high aircraft all-up weight resulted in a best achievable rate of climb of about 400 feet per minute. This was reduced by the effects of downdrafts, turbulence, and the turn, with the result that the aircraft could not outclimb the terrain.

Significant Factors:

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

1. High density altitude.

2. High aircraft all-up weight.

3. Turbulence and downdrafts over the surrounding hills.

4. Pilot's low aeronautical experience level.

The pilot was cooling the engine down at 2500 RPM after completing a circuit and normal landing. Suddenly, a hard, high frequency bounce developed and the helicopter bounced left skid low followed by a 45 degree yaw to the left. The pilot had tightened the control frictions after landing and he attempted to release these as he fought for control of the helicopter. He was unable to release the control frictions and the cyclic control grip was broken during his attempts to restrain the movement of this control. The engine stopped without input from the pilot and the aircraft came to rest. The period of ground resonance had been about 5 seconds. During the preflight inspection the pilot had noticed that the front left landing gear was slightly under-inflated, although he considered it to be within normal limits. However, the correct landing gear damper inflation is critical in the prevention of ground resonance in this type of helicopter and the Pilot's Flight Manual contains a caution to this effect. Incorrect or unequal landing gear damper pressure can markedly alter the resonance response of the undercarriage system of the helicopter. If a rotor head vibration is induced, for whatever reason, and it is in sympathy with the resonance response of the undercarriage system, then ground resonance will occur. The cause of the rotor vibration that initiated this occurrence of ground resonance could not be established.

An unidentified aircraft was heard to depart Kalgoorlie at approximately 0430 hours, and VH-UQR was subsequently reported to have been stolen. Some four hours later the aircraft was sighted, flying at low level, by a number of witnesses in the Margaret River area. The engines were reported to be not operating normally. The aicraft then disappeared from sight behind trees and was heard to crash. The wreckage was located in a heavily wooded area. An inspection of the site indicated that the aircraft had collided with the ground following a high speed descent at an angle in excess of 30 degrees. Neither engine was producing power at the time of impact. The investigation indicated that the fuel supply had been exhausted at the time of the accident. Although the aircraft was almost totally destroyed there was no evidence that aircraft components or systems contributed to the accident. Neither pilot was qualified to fly, or had any known flying experience, on the Cessna 310 or any other multi-engine aircraft type. The factors leading to the theft of the aircraft were not established.

Circumstances:

The aircraft departed with full fuel tanks and had been airborne for approximately 25 minutes when the engine lost power. The pilot sustained back injuries in the subsequent forced landing. The investigation revealed that a threaded union which connected a drain line to the bottom of the carburettor fuel bowl had unwound, causing the bowl to drain. The engine then lost power due to fuel starvation.

Significant Factors:

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

1. For reason(s) which could not be established, a drain line connected to the bottom of the carburettor fuel bowl had become loose, allowing fuel to leak from the bowl.

2. The engine lost power due to fuel starvation.

Circumstances:

The pilot reported that he was positioning for a pickup of passengers, and he had completed a visual circuit and approach to the strip. He achieved a gentle touchdown within 100 metres of the threshold of the 1065 metre strip on both main wheels. Coincident with lowering the nosewheel onto the strip, the pilot reported feeling the aircraft lurch which he first took to be symptomatic of a flat tyre on the left main gear. He had no trouble maintaining directional control. A little later, the left wing dropped further, and the gear warning horn sounded. The pilot was able to keep the aircraft within the defined width of the strip and, on coming to rest, he shut down the aircraft before egressing. A post flight inspection by the pilot showed that the left main gear oleo leg had swung rearwards and the lower surface of the flaps had been dented by the tyre. The reduced ground clearance had allowed the left propeller to strike the ground, but the left main gear doors were out of contact with the ground. A detailed inspection of the main gear components showed that the left main gear drag link centre bolt had failed in fatigue. Furthermore, all the landing gear components showed signs of wear beyond tolerances, and this condition was evident of inadequate maintenance and inspection.

Significant Factors:

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

1. Fatigue failure of the left main gear drag link centre bolt.

2. Probable inadequate maintenance and inspection. This accident was not the subject of an on-scene investigation.

The pilot reported the following The right main landing gear collapsed, soon after touch down at Maggieville Station airstrip, at the completion of a two hour flight from Massacre Inlet. The aircraft had been configured for a short field landing, however, it had floated for a short distance along the airstrip before the main wheels touched down. As a result the pilot applied "full braking" as soon as the aircraft had settled on to the runway. At the same instant that the brakes were applied the right main landing gear folded backwards and collapsed. Investigation revealed that two of the three bolts which support the right main landing gear (including the main locating bolt) had sheared off, and the cast sections of both channel supports had been damaged. The pilot could find no evidence on the runway of an obstruction or pothole and has no recollection of any previous hard landings or wheel contacts, which might explain the damage. However, he did report that two of the right main wheel hub bolts, had failed and were replaced approximately one week prior to this accident. After carrying out temporary repairs, at Maggieville Station, the aircraft was flown to an approved maintenance facility in Mount Isa to have the right landing gear replaced.

The chief engineer, a Licenced Aircraft Maintenance Engineer (LAME), at the maintenance facility in Mount Isa, inspected the damaged section of the landing gear. He reported that both halves of the right main wheel hub had been damaged in a manner which indicated impact with a large object. Examination of the remainder of the landing gear supported this premise. Two of the three landing gear attaching bolts, had sheared off as a result of excessive side loads, and the remaining bolt was bent. Damage to the channel support was caused by the shearing action of the main landing gear exiting the fuselage attachment recess. The LAME stated that there was no evidence of corrosion, or any pre-existing cracks, found on any of the damaged components. The failure was totally consistent with an overload failure.

The investigation did not determine conclusively when the damage to the landing gear was sustained, but it may have been the reason the two wheel hub bolts had to be replaced the previous week.

The aircraft was cruising at 9500 feet when the oil filter adaptor became detached from the engine, causing complete loss of oil pressure. As a result the number two big end failed and the number two connecting rod punctured the crankcase. During the ensuing forced landing, on a road, the pilot was unable to fully manually lower the landing gear. After touchdown the right main gear leg collapsed, causing the aircraft to strike a dirt bank. The oil filter adaptor thread had been damaged by overtightening and this allowed the adaptor to detach from the housing on the oil pump casing. Following the failure of the engine it became necessary to lower the landing gear by using the emergency system. Hydraulic power to lower the gear is normally provided by the engine driven hydraulic pump. It was determined that the pilot was unable to fully extend the gear with the emergency gear extension handle as the handle had apparently inadvertently been moved slightly inward. Any inward movement of the handle jams the pump action making the handle difficult to move thus giving the impression that the gear is fully extended.

Circumstances:

The helicopter was engaged in cattle mustering operations. Whilst in level flight at an altitude of 200 feet, the pilot heard a loud noise and felt severe vibration from the engine, which subsequently failed. Following autorotation to ground impact, the aircraft rolled onto its side. The semi-conscious pilot was assisted from the wreckage by the passenger who had evacuated the cockpit unassisted. Strip examination revealed that the engine had failed due to broken conrod bolts and a separated conrod big-end cap from the No. 4 cylinder conrod assembly. This had resulted in internal mechanical damage sufficient to stop the engine.

Significant Factors:

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

1. Conrod bolt failure.

2. Loss of control during the landing. This accident was not the subject of an on-scene investigation.