Circumstances:

The aircraft was approximately 40 minutes into the flight when the pilot noticed a substantial loss of oil pressure. He initiated a diversion to the nearest suitable aerodrome, but several minutes later, following an increase in RPM, the engine failed. A small quantity of oil appeared on the windscreen and the cabin filled with smoke. The propeller continued to windmill during the descent, causing moderate to severe vibration from the rotating engine. A successful wheels-up forced landing was carried out into a cleared area. Inspection of the engine revealed a hole in the top of the crankcase adjacent to and rear of the oil filler neck which was caused by the failure of the number four connecting rod. The screws attaching the oil filler neck flange to the crankcase were found to be excessively loose, allowing a gap between the flange and the crankcase. There were no other apparent oil leaks. The aircraft had undergone a major inspection and top overhaul 108 hours prior to the accident and had flown 5 hours since the last periodic inspection. There was no reason to remove or loosen the oil filler neck at either of these inspections or during the salvage operation. Before further inspection of the engine could be carried out, it was discovered that the filler neck had been retightened. This caused metal fragments which had been suspended in the oil to become embedded into the gasket material. This confirmed that contaminated oil had exited the engine through this aperture. The pilot stated that he had checked the oil level and the security of the oil cap prior to the flight without noticing any looseness of the filler neck. The oil filler neck may have been loose during the earlier part of the accident flight but was held in position by the screw threads catching and interfering with the holes in the filler neck flange. The pilot's twisting action on the cap, as well as vibration and crankcase pressure may have caused the filler neck flange to lift off the crankcase, probably with the gap between the flange and crankcase being positioned in such a way that a capillary action was created by the airflow, causing the hot oil to be drawn from the crankcase. The oil then flowed with the cooling air between cylinders number four and five to both the underside and lower left-hand surfaces of the fuselage via the nose wheel well, all of which were thickly coated in oil. There was an insignificant amount of oil, with relatively dry carbon and sludge deposits in the crankcase breather outlet and associated plumbing, indicating that the oil had not escaped from the engine via that route. As the oil level in the engine decreased, oil pressure also decreased, and with insufficient oil flow and pressure to operate the propeller governor, normal rotational loads on the propeller moved the blades towards the fine pitch position increasing the engine RPM. Oil starvation caused overheating of the crankshaft, allowing the babbit alloy of the connecting rod bearings to melt. The number four connecting rod bearing was the first to fail, with separation of the bearing cap allowing the rod to flay about, causing the hole in the top of the crankcase. The small amount of oil thrown onto the windscreen indicated that most of the oil had already escaped from the engine prior to the failure.

Significant Factors:

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

1. The engine developed a serious oil leak.

2. The oil filler neck to crankcase attachment screws were excessively loose, probably allowing oil to escape from the engine through the gap between the oil filler neck and the crankcase. The reason why the screws were loose could not be determined.

3. The number four connecting rod failed due to oil starvation. This accident was not the subject of an on-scene investigation.

Circumstances:

The left hand fuel filler cap locking tongue had been replaced during the periodic servicing 20 hours prior to the accident. The new tongue did not have a positive feel when pushed to the closed position and the cap did not seal correctly. The pilot was aware that the bladder type fuel cells could trap water which might not be apparent during a normal fuel drain. About one week before the accident and following heavy rain, the pilot rocked the aircraft, during his fuel drain check, to remove all the trapped water. On the day of the accident the pilot refuelled the aircraft, to full tanks, from an un-opened 200 litre drum. A subsequent check of the drum disclosed some water although in insufficient quantities to enter the standpipe of the hand pump during refuelling operations. The pilot carried out a normal fuel drain check which indicated that the system was free of water. He did not rock the aircraft as there had not been any significant rainfall since his previous check. At 150 feet above ground level, shortly after take-off and following flap retraction and power reduction, the engine stopped. The pilot carried out a turn through 170 degrees in an attempt to land in the only reasonable area. The nosewheel collapsed on touchdown and the aircraft overturned. An inspection of the aircraft's fuel system disclosed water contamination in the main fuel filter bowl, in the fuel lines to the carburettor and in the carburettor. No other defects found which may have been factors in the accident. It is probable that water entered the fuel tanks, via the defective fuel cap and remained trapped in the tank despite the checks carried out by the pilot. Water subsequently entered the engine fuel system during the manoeuvers following take-off.

Significant Factors:

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

1. The fuel filler cap was still unserviceable following replacement of the locking tongue.

2. Water in the fuel system that was not detected during the pre-flight inspection.

3. Engine stoppage caused by water contamination of the fuel system.

4. Unsuitable terrain for a forced landing.

The pilot conducted a daily inspection of the helicopter prior to meeting another company pilot to fly two helicopters to a mustering camp. After start he reported by radio to the pilot of the lead aircraft that he was ready to depart. Ground witnesses saw the two helicopters depart in company. The lead pilot proceeded to Hell's Gate and landed but the second aircraft did not arrive. The second helicopter was found one day later about 7 km from Doomadgee and on the extended centre-line of the runway. Examination of the wreckage indicates that the helicopter struck the ground inverted and with a high rate of descent. No pre-existing defects were found in the helicopter. No evidence to indicate that the pilot was other than healthy or suffered from any incapacitation was found during a post-mortem examination. While the factors associated with the cause of this accident were not determined, one possibility is that the pilot suffered a flicker induced seizure. This phenomenon can be caused by the passage of sunlight through the main rotor creating a strobe effect in the cockpit. It may have resulted in control inputs, by the pilot, which could have caused the helicopter to become inverted and crash.

Circumstances:

The aircraft had been refuelled from drums at a refuelling point located at one end of the lagoon. The refuelling point was surrounded by tall trees, so the pilot decided to hover taxi out over the lagoon and to execute a take-off from a more open area. The take-off had to be initiated with a slight tailwind, and the pilot intended to turn and to depart upwind after the aircraft had obtained translational lift. As the pilot initiated the take-off, the aircraft experienced a tailwind gust and began to lose height. In an attempt to check the descent, the pilot overpitched the main rotor. The right skid contacted the water surface and the aircraft simultaneously pitched forward and rolled to the right before coming to rest on the lagoon bed. The two occupants evacuated the aircraft without injury.

Significant Factors:

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

1. The aircraft experienced a tailwind gust as the pilot initiated the take-off.

2. The pilot overpitched the main rotor while attempting to counter height loss from the gust.

3. Loss of lift resulted in the right skid contacting the lagoon surface. This accident was not the subject of an on-scene investigation.

Circumstances:

The aircraft was established in normal cruise flight when the pilot thought he could smell burning oil. A check of the engine instruments did not indicate any problem, but he elected to return to Essendon. The Essendon Terminal Information Service recording advised runway 35 was in use wind from the north at 15-30 knots and a temperature of 28 degrees. The flying conditions were moderately turbulent, and the pilot made the approach with 10 degrees of flap and at 75 knots. Observers in the Tower reported the aircraft touched down well into the runway heavily nosewheel first and bounced two or three times before coming to rest. Subsequent ground inspection of the aircraft revealed that the bolt attaching the upper portion of the nose gear leg to the aircraft had been sheared by straight overload forces. This had allowed the upper part of the nose leg to be forced into the engine bay under pressure. The engine firewall was also buckled.

Significant Factors:

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

1. Strong gusty wind conditions.

2. The pilot misjudged the landing flare and touchdown.

3. The pilot was possibly distracted by the perceived engine problem.

Circumstances:

A night take-off was initiated from runway 21. The runway was wet, with patches of standing water on the surface. Light rain was falling, with a south-easterly surface wind of 10 to 15 knots. The crosswind component was close to the maximum specified for this type of aircraft. Just prior to reaching rotation airspeed the left mainwheel apparently entered a pool of standing water, and the pilot reported that at the same time the aircraft was subjected to a strong wind gust. The aircraft swung to the left and the pilot was unable to maintain directional control. The pilot thought that the aircraft may have commenced to aquaplane, and he closed the throttle immediately. There was no attempt made to apply brakes. The aircraft departed the runway to the left, crossed the grass flight strip, and continued for approximately 85 metres, before colliding with a levee bank and coming to rest in a drainage ditch. No evidence of aquaplaning was subsequently found. This accident was not the subject of an on-scene investigation.

Significant Factors:

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

1. Patches of standing water on the runway which were not visible to the pilot.
2. Loss of directional control following penetration of standing water and/or sudden wind gust.
3. The pilot did not apply braking in an attempt to slow the aircraft prior to the collision with a ditch.

Circumstances:

The pilot had hired the aircraft to conduct a flight to a destination 240 kilometres from the DEPARTURE airport. The aircraft had been operating that day on a charter flight and was late returning. This caused the pilot to become anxious as the weather was forecast to deteriorate. He was informed by the operator that fuel had been arranged for the aircraft on its arrival, and it would be replenished to the indicator tabs in the fuel tank filler necks. This would give the aircraft an endurance of 240 minutes, the return flight time being estimated as 110 minutes. The pilot duly submitted a flight plan indicating this endurance. When the aircraft landed the refueller set out to refuel it, but the tanker broke down. When the pilot arrived at the aircraft, he assumed that it had been refuelled. He carried out a rushed pre-flight inspection including a check of the fuel tanks, although he did not consciously notice if the level was up to the tabs. The flight to the destination was uneventful, but at no time did the pilot seriously consult the fuel gauges in the aircraft. The next morning the pilot prepared for DEPARTURE, but as the airstrip was located on a claypan and there was a chance of further rain that would render the area unserviceable, he again rushed the pre-flight inspection. He was still able to see a level of fuel in the tanks but again failed to cross reference this with the fuel gauges. Approaching Alice Springs, the engine began to run roughly and lose power. The pilot was unable to restore power and carried out a forced landing in the only suitable area. On landing the aircraft bounced heavily then collided with a tree. The pilot believed that the aircraft had suffered a fuel blockage and was surprised to learn that the aircraft had not been refuelled before his DEPARTURE. He then accepted the fact that he had run out of fuel. This accident was not the subject of an on-scene investigation.

Significant Factors:

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

1. Pilot anxiety/apprehension at deteriorating weather conditions.

2. Inadequate pre-flight inspection on two occasions.

3. The pilot did not monitor the fuel gauges during flight.

4. Fuel exhaustion, resulting in the pilot being forced to land on unsuitable terrain.

Circumstances:

The purpose of the flight was for the pilot-under-instruction to gain endorsement for constant speed propeller and retractable landing gear operations. This was only the second flight on type for the pilot-in-command and the first for the pilot-under-instruction. The pilots stated that the pre-landing checks had been completed and that the landing gear down and locked light was illuminated. The light was rechecked on final approach to the runway. The pilots reported that the touchdown seemed normal, but the aircraft soon adopted a left wing low attitude. The propeller then contacted the runway surface and the aircraft settled on to its underside before skidding to a halt. A thorough examination of the landing gear system revealed no fault. The type and location of abrasion damage to the nosewheel doors, and the lack of damage to the main gear fairings and brake assemblies, indicated that the doors were closed when the underside of the aircraft contacted the runway, i.e. the landing gear was in the retracted position. It was noted that the red and green post lights on the instrument panel which indicate high and low vacuum pressure were of the same type as the landing gear position lights. The green vacuum light was seven centimetres from the green landing gear down light in approximately its two o'clock position. It was considered possible for the crew to have mistaken one light for the other.

Significant Factors:

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

1. Neither pilot was familiar with the aircraft type.

2. The landing gear was not extended.

3. The pilots possibly mistook the green vacuum light for the green landing gear light on the instrument panel.

4. The aircraft landed with the landing gear retracted.

Circumstances:

The aircraft was being prepared for a normal push-back DEPARTURE from the Sydney freight apron position V2. A towing tug was connected to the nose gear and number two engine was running at idle power. The aircraft was cleared to be pushed back to taxiway GOLF where the other engines would be started. The aircraft brakes were released but as the tug took the weight for the push back, there was a loud report, and the nose of the aircraft collapsed onto the cabin roof of the tug. The nose wheels folded back under the fuselage and arrested its fall, saving the tug cabin from further collapse. The engine was immediately shut down and the crew departed the aircraft to assess the damage. Investigation revealed the nose landing gear oleo outer cylinder, fabricated from 7079-T6 alloy, had failed at the upper end of the cylinder bore. The failure was initiated by a fatigue crack in the radius at the bore end forward quadrant. The radius in the vicinity of the crack was found to be .039 inches, marginally less than the manufacturer's minimum dimension of .040 inches. Extension of the crack due to stress corrosion was extremely rapid and may have occurred whilst the aircraft was parked at Sydney. Because of numerous reports of cracking in this area, the manufacturer issued a service letter recommending that operators consider replacement of nose landing gear cylinders fabricated from 7079-T6 alloy with cylinders of 7075-T3 or 7049-T73 alloy at overhaul.

Significant Factors:

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

1. A fatigue crack developed in the bore top radius of the nose landing gear cylinder.

2. The marginal dimension of the bore top radius may have contributed to the development of the initial fatigue crack.

3. Stress corrosion then developed the crack at a rapid rate to final failure.

Recommendations:

A recommendation to improve the strength of towing tug cabins is being prepared.

After selecting gear up on DEPARTURE, the pilot noticed the gear unsafe light did not go out. He assessed that it was probably a false indication and continued with the local flight. On return for landing, the right main landing gear leg would not extend by the normal or the emergency systems. The pilot elected to land with the landing gear retracted. After conducting a trial approach and overshoot on runway 31, he made a shallow approach for the same runway from 6 to 7 km out. The wind was from the north-west at 10 to 15 kts. His intention was to touch down near the threshold. Full flap was selected on long final, and airspeed was reduced to 60 kts, 15 kts below the normal approach speed. On late final sudden sink was experienced and the aircraft struck the ground about 120 m short of the runway. It then slid into a large drainage ditch along the airfield boundary. The right landing gear leg failed to extend because the bolt joining the upper and lower torque links had fractured. This bolt had become corroded and seized in the bushes through lack of lubrication. Bolt failure allowed the upper torque link to catch on a section of the landing gear bay, thereby preventing the gear leg from being extended. The pilot indicated that he elected to conduct the approach at a lower-than-normal airspeed because he wished to minimise the resulting ground slide.

Significant Factors:

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

1. Mechanical failure to the right main gear torque link bolt, due to lack of lubrication.

2. Landing approach conducted at a lower than recommended airspeed.