When the helicopter had not arrived at its destination, a search was commenced. The wreckage was found the following morning close to the intended route for the flight. The main rotor hub with the blades attached was found approximately 140 m from the burnt-out fuselage which had bounced several metres after impacting the ground in a steep nose-down attitude.

There were no witnesses to the accident. The pilot was reported to have been fit and well rested prior to the flight. On ferry flights, he generally flew the helicopter at about 1500 ft above ground level (AGL). The weather in the area on the morning of the accident was reported to have been fine and calm.

The relative positions of the main rotor hub assembly and the fuselage indicated that separation of the main rotor occurred during flight. Examination of the main rotor mast showed that the mast failed in torsional overload between the swash plate and the hub assembly. One of the elastomeric blocks on the teeter stop assembly had been subjected to a compressive force of sufficient magnitude to fracture the elastomeric block retaining strap. However, the area of the mast behind the teeter stop had not experienced any deformation. The damage to the teeter stop and the mode of failure of the mast is the type of damage that might be caused by a mast bump.

Among the causes of mast bump are pilot manipulation of the flying controls and failure of one or more of the control linkages to the main rotor. Examination of the control linkages indicated that they failed in overload, consistent with main rotor assembly separation. Pilot induced mast bump can occur if the main rotor disc loading is reduced to less than 0.5g. Under such conditions, the main rotor can travel outside its normal limits and bump against the mast.

On this occasion the reason(s) for a reduction in g loads could not be determined. There were no known aircraft, with which the helicopter might have conflicted, operating in the area at the time. Information from another local aircraft operator indicated that large concentrations of birds were not uncommon in the area at that time of the year. However, notwithstanding the severe fire damage to the fuselage, no evidence was found in the wreckage of the helicopter having struck a bird. Further, the drive train between the engine and gearbox were inspected on site, and the engine and main rotor gearbox were stripped and inspected in a workshop. No faults which could have contributed to the accident were found.

Factors

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

1. For reasons which could not be determined, a mast bump occurred during flight.

2. The main rotor mast failed due to torsional overload as a result of the mast bump.

The gyrocopter took off from Albion Park aerodrome and was subsequently seen flying very low over local houses before it departed the circuit area on an easterly heading. It was later observed flying low over Lake Illawarra towards a residential area on the eastern shore. After passing low over houses the gyrocopter was seen to enter a steep turn to the left. During the turn it descended and collided with a tree in a nearby reserve. The machine was destroyed by the impact and the pilot was fatally injured.

No defects were found with the gyrocopter that could have contributed to the accident. It is likely that the pilot attempted a manoeuvre beyond his ability on the aircraft type. The reason such a manoeuvre was attempted in the vicinity of a residential area was not determined.

The helicopter had been engaged in spraying operations for more than three hours and was refuelled on several occasions whilst the engine was running. This procedure, which is approved by the Civil Aviation Authority, is known as "hot refuelling".

The pilot reported that he landed the helicopter to the left and rear of a stationary utility vehicle which contained the refuelling equipment. After the helicopter came to rest, and contrary to normal hot refuelling procedure, the driver reversed the utility towards the helicopter and stopped under the main rotor disc. The driver then took a fuel hose from the tray of the utility to the helicopter. Upon returning to the utility, he climbed onto the rear tray to start transferring fuel but was struck on the head by the main rotor blades and received fatal injuries.

The driver had been conducting hot refuelling for more than five weeks. The procedure called for the vehicle to remain stationary after the helicopter landed. The pilot was required to park the helicopter in a position where the main rotor disc was clear of the utility. With the vehicle parked in this position relative to the helicopter, the driver could safely climb onto the rear tray to pump fuel into the helicopter without fear of being struck by the rotor. The reason why the driver departed from this procedure was not established.

The aircraft was observed to taxi from its hangar to the southern end of the airstrip, turn onto the runway and start to taxi north. After taxiing a short distance, the engine power increased and the aircraft took off to the north, becoming airborne about halfway along the strip. At a height of about 150 feet, above the northern end of the strip, the engine was heard to stop and start again. The aircraft turned left with the engine running intermittently. Soon after, it was seen in a steep nose down attitude which continued until it descended into trees.

An investigation failed to determine the reason for the intermittent operation of the engine. No defects were found with the aircraft which were likely to have contributed to the accident.

The left turn was consistent with the pilot attempting to turn back to the airfield for a landing, after the engine malfunctioned at a critical stage of flight over heavily timbered terrain, with no suitable areas for a forced landing. During the turn the aircraft apparently stalled and entered a steep nose down attitude at a height which was insufficient for the pilot to regain control.

Significant factors

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

1. The engine malfunctioned at a critical stage of flight.

2. The aircraft was over terrain unsuitable for a safe forced landing.

3. The aircraft stalled during an attempted turnback with insufficient altitude for recovery.

On 1 July 1992, SAAB SF-340A, VH-EKT, was engaged on a scheduled passenger service from Melbourne, Victoria to Devonport, Tasmania. During the flight, the crew experienced difficulty in controlling the right propeller RPM. When the aircraft landed at Devonport, directional control was lost.

The aircraft departed the runway and ran through a ditch in soft, muddy ground. The aircraft sustained substantial damage but there were no injuries to passengers or crew. The investigation revealed that a severe asymmetric thrust condition developed after landing when reverse thrust was selected but the right propeller remained at a positive blade angle.

The report concludes that the right propeller control unit was defective, due to internal oil leakage across the feathering solenoid valve. As a result, the propeller failed to respond normally to pilot control input.

The pilot departed Moorabbin with one passenger on board and flew to the designated Moorabbin aerobatic training area with the probable intention of practising aerobatic manoeuvres. The pilot was approved to perform aerobatic manoeuvres down to 500 feet. The passenger was an experienced flying instructor who also held an approval for low level aerobatics down to 500 feet, but he was not experienced on the Pitts S2A aircraft.

Only one known witness saw the aircraft in the last few seconds before impact. Her attention was attracted to the aircraft by its loud engine noise. She briefly observed the aircraft performing an aerobatic manoeuvre while descending towards the ground at an angle of about 45 degrees. The aircraft was travelling in a westerly direction when it disappeared behind a row of Cyprus trees and impacted the ground about 300 metres north-west of her location. Subsequently the witness was shown a video of Pitts aircraft performing various aerobatic manoeuvres. The manoeuvre she identified as what she saw VH-SZA perform was a descending snap roll to the left.

Airframe and engine damage indicated that the aircraft was rotating to the left when it impacted the ground in a steep nose down attitude. Propeller damage indicated that the engine was at a low power setting at impact. No fault has been detected with the engine.

The right rudder cable attachment to the rudder horn was found to have pulled out of the Nicopress copper sleeve/swage thereby disconnecting the right rudder cable from the rudder. A similar disconnect was found with the left rudder cable at the pilot-in-command's left pedal. It was determined that the correct copper sleeves were used on the correct one eighth inch diameter rudder cables but that the swaging had been carried out with the Nicropress jaws that were appropriate for a five thirty second inch cable. Four Nicopress copper sleeves were under swaged. Specialist examination subsequently concluded that the improperly constructed rudder cables probably failed at impact and not in flight.

The reason why the two pilots failed to recover the aircraft from an aerobatic manoeuvre could not be determined.

Significant Factor

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

1. The aircraft was engaged in low level aerobatics and struck the ground for undetermined reasons.

The pilot indicated prior to departure that his intention was to track from Launceston directly across Bass Strait to Tyabb, rather than via the Bass Strait Islands. The aircraft departed Launceston with an air traffic control clearance appropriate to that intention.

After being airborne for about one and a half hours, the aircraft approached over Cape Barren Island, although the pilot had not indicated that he was diverting from the planned track. Two very low circuits were flown in the vicinity of the airstrip and while still flying low, the pilot asked the front seat passenger to tell him what he could see below the aircraft.

The survivor, who was sitting in the right rear seat, gained the impression that the pilot could not see and that he was unwell, although apparently not in pain. He did not respond when she spoke to him. She undid her seat belt, leant over the pilot and asked if the passengers could do anything to assist. The pilot did not reply and his eyes appeared glazed. She shook him, but almost immediately the aircraft descended steeply to the ground.

From the damage sustained by the aircraft and the lack of any significant ground slide, it was assessed that the aircraft had stalled from probably no higher than 150 feet and had impacted the ground in a steep nose down and left wing low attitude. Both wing flaps were found to be extended, suggesting that the aircraft was in a landing configuration.

Medical tests and examination were unable to substantiate any cardiac or cerebral event which might have accounted for the pilot's incapacitation. There are indications, however, which suggest that the incapacitation was as a result of an insulin related condition. The pilot had successfully passed his last Civil Aviation medical examination in December 1991.

Significant Factors

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

1. The pilot apparently suffered a subtle form of incapacitation which progressively reduced his ability to control the aircraft.

On 5 June 1992, the pilot received a one hour checkout in the aircraft from an instructor. On 12 June the pilot flew the aircraft from Coldstream to Lilydale, where his passengers were waiting. While the pilot was checking the weather forecasts an instructor commented that they indicated that the weather conditions were unfavourable. However, the pilot decided to commence the flight and assess the actual enroute weather conditions.

Melbourne Air Traffic Control Radar recorded the track and groundspeed of the aircraft from Lilydale to the area of the accident. The aircraft had passed close to Mangalore Aerodrome, where the cloud base was about 1,500 ft above ground level (agl). It then deviated from the planned track and subsequently penetrated an active military restricted area. Soldiers on the range heard the aircraft approaching and ceased all firing. The aircraft was observed to be flying at about 300 ft agl and clear of cloud. There was no rain in the immediate vicinity and the visibility was reported to be good.

After flying through this and an adjacent restricted area, the track of the aircraft became erratic. During the final minutes of the flight, the recorded groundspeeds varied from 148 kts to 75 kts. The last speed recorded was 138 kts. No radio transmissions were recorded from the aircraft.

Witnesses near the accident site observed the aircraft flying at about 300 ft and reported that the engine noise was particularly loud. Weather conditions were overcast, with the cloud base at about 500 ft and patches of rain and drizzle in the area but not near the accident site. The aircraft was then seen to bank progressively to the left and descend. Impact marks indicated that as the aircraft passed about 140 degrees of bank angle, it clipped the tops of gum trees and then struck the ground. The impact marks and degree of disintegration indicated that the aircraft impacted the ground at high speed.

A detailed examination of the wreckage did not reveal any fault or malfunction with the structure, engine and associated systems of the aircraft which might have led to the accident. The landing gear and flaps were retracted and there was ample fuel on board the aircraft. The weight and centre of gravity were estimated to have been within the prescribed limits.

The area in which the accident occurred was open and relatively flat, with several sites suitable for precautionary or forced landings. Tests conducted in the area indicated that radar coverage existed down to about 250 ft above ground level, with radio communications possible almost to ground level.

The postmortem examination revealed that the pilot had coronary artery disease, but it was not possible to determine whether this had led to an in-flight incapacitation. In addition, the pilot had a history of hypertension, which was controlled by medication. He was also on a weight loss program, which involved taking fenfluramine as an appetite suppressant. Common adverse reactions from fenfluramine include mild sedation, lethargy and giddiness.

The investigation was unable to determine the precise circumstances leading to the apparent navigation difficulties experienced by the pilot, although the weather conditions may have contributed. The behaviour of the aircraft and pilot in the vicinity of the accident site, erratic airspeed, excessive bank angle and failure to take advantage of suitable landing areas, may have been related to the physical problems suffered by the pilot. The onset of any such problems may have been too sudden to permit the pilot to conduct an emergency landing.

Significant Factors

1. Weather conditions were marginal for visual flight.

2. The pilot was probably uncertain of his geographical position.

3. It is possible that the pilot became incapacitated in flight

4. Loss of control occurred at a low height above the ground.

The aircraft was on a scheduled domestic passenger service flight from Karratha to Perth at Flight Level 310 (31,000 ft). As the aircraft entered cloud white diverting around a large thunderstorm, there was a sudden and significant rise in the outside air temperature. A short time later, all four engines progressively lost power and the aircraft was unable to maintain altitude.

During the next 17 minutes, numerous attempts to restore engine power were made without success until, approaching 10,000 ft altitude, normal engine operation was regained. The aircraft diverted to Meekatharra where a normal landing was completed. The investigation determined that during high altitude cruise, the aircraft entered an area of moist air significantly warmer than the surrounding air.

This resulted in a need to select engine and airframe anti-ice which in turn placed high bleed air demand on the engines. Under these conditions the fuel control units were unable to schedule sufficient fuel to the engines, thereby causing them to lose power, a phenomenon known as 'roll-back',