The Taroom aerodrome had recently been equipped with a pilot activated lighting (PAL) system which was due to be commissioned on the evening of 15 October 1988. The pilot, who is a local Council member had flown from his property "Kolane" to Taroom late in the afternoon, to check that the PAL system was functional. He had intended to fly to Taroom the following evening to activate the lights for the official opening celebration, which was planned to be held at the aerodrome. After checking that the system was working the pilot decided to take the opportunity to practice some night circuits and landings before returning to his property. Before departing Taroom he arranged to have two vehicles positioned at his property landing area to illuminate the strip which is 850 metres long, aligned 235/055 degrees magnetic, and 1000 feet above sea level. He apparently intended to check the suitability of the strip for a night landing on his return. The aircraft was observed to fly over the strip in a north-easterly direction and then make a left turn. The aircraft was then seen to descend and the sound of impact was heard by the occupant of a vehicle near the strip. The aircraft had impacted the ground whilst in a descending left turn at a groundspeed of approximately 125 knots. Initial impact was in a clearing near trees. The aircraft slid 91 metres before the left wing struck a large tree and was torn off. The aircraft slid another 45 metres before coming to rest and catching fire. The pilot was thrown from the aircraft while still strapped to his seat and was able to move himself away from the immediate vicinity of the fire before help arrived. The pilot has no recollection of events immediately prior to the accident. There is no indication that the aircraft was not functioning normally at the time of the accident. The weather was fine, there was a light northerly breeze, and there was no moonlight. Indications are that the pilot may have become disorientated whilst attempting to carry out a visual circuit when there was no visual horizon. The landing area did not meet the requirements for night operations published in the Visual Flight Guide.

Circumstances:

The aircraft was being used for dual training and was operating in the circuit, having been airborne for about 45 minutes. During a turn onto the crosswind leg the engine partially lost power. The instructor immediately took control as the power was inadequate to maintain height and initiated a turn for landing on the reciprocal runway. On the approach, the aircraft struck trees bordering the edge of the strip and dived vertically to the ground. The instructor's seat attachment was damaged during the collision with the trees, prior to ground impact. Examination of the engine's spark plugs indicated the front cylinder had ceased to deliver power. The partial loss of power was the result of dirty fuel. Contamination was found in the float bowl of the front cylinder carburettor, in the fuel filter, and in the fuel line between the fuel tank and filter. The contaminated motor vehicle fuel was purchased from a nearby service station on the day prior to the accident. Two stroke oil was mixed with the fuel by the aircraft operator and not adequately filtered before being added to the aircraft fuel tanks.

Significant Factors:

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

1. The engine suffered a partial loss of power during the crosswind turn in the circuit.

2. The engine power output was insufficient to enable to the aircraft to reach the airstrip.

3. The partial power loss was due to fuel starvation as a result of contaminated fuel.

4. The fuel was not adequately filtered before it was added to the aircraft fuel tanks.

Recommendations:

It is recommended that the Australian Ultralight Federation remind all pilots and operators, of the requirements and procedures to maintain stringent fuel quality control.

After landing, as the aircraft turned left into the taxiway, the left maingear collapsed. Inspection revealed that the drag link centrebolt had failed. Examination of the bolt revealed that it had failed due to fatigue, which had initiated from pit corrosion along the shank of the bolt. It also displayed signs of in-service wear which possibly contributed to the failure. This aircraft reportedly operated from rough, uneven dirt strips on a regular basis.

After flying in cloud for 15 minutes of a 17 minute cruise at 18000 feet descent was commenced to the destination aerodrome. As the aircraft was passing 7800 feet on descent in cloud and light to moderate rain the cockpit warnings alerted the crew to a failure of the left engine. However, before any rectification action could be undertaken by the crew, all warnings ceased and power was observed to be restored. The crew reported that although approximately 15 minutes of cruise flight had been in cloud, the only visible ice accretion was a very light rime ice coating on the leading edge of the wings. There was no ice visible on the propellers or the nacelles. The investigation noted that this and all other reported incidents involving uncommanded engine shut down (flameout), occurred either when the aircraft was in moderate to severe icing and free moisture or shortly after exiting those conditions. Tests carried out at certification failed to reveal the source of a critical ice buildup in the intake duct or engine. It was revealed that a propeller was not fitted to the test unit during the ice tunnel tests and subsequent post certification tests have suggested that an unusual swirl which has been detected coming from the propeller may be a contributing factor causing a blanketing effect in the intake duct. Depite early modifications to the Electronic Engine Control Unit, the Handling Bleed Valve and the Fuel Nozzles further cases of uncommanded engine shutdown under similar weather conditions were experienced. It is considered that these modifications by themselves are not sufficient to prevent a recurrence of the flameout problem. Subsequent tests by the manufacturer using video camera equipment installed in the intake duct revealed ice buildups on the unheated flexible seal between the intake duct and the engine flange. The tests confirmed that when a critical mass of ice was reached the buildup would break off and be ingested by the engine resulting in power fluctuations. It is considered that the inflight power fluctuation incidents have been caused by flameouts originating from ice ingestion in the engine. It is considered that the methods adopted to satisfy the certification requirements for icing failed to adequately address the area of intake icing. Had they done so, the formation of ice on the unheated flexible seal between the intake duct and the engine flange would have been discovered prior to certification.

At 0341 hours EST on 6 July 1989, Beech 70 Queenair aircraft registered VH-XAE collided with high voltage power lines and descended rapidly, contacting the ground three kilometres north-east of Tolmie. The pilot, who was the only occupant, received fatal injuries. There was no fire. The aircraft was on a flight from Sydney to Melbourne cruising at 8000 feet. Persons in the accident area heard an aircraft flying very low over their houses, then observed a flash of light and heard the sound of ground impact. A ground search was commenced but due to falling snow and very poor visibility the wreckage was not found until about 0745 hours in daylight. The elevation of the ground at the accident site was approximately 2700 feet above sea level. The accident site was located at co-ordinates 36`55'south, 146`17'east.

After having inspected a property, the pilot and his passengers returned to the aircraft to prepare for DEPARTURE. A storm was approaching the strip from the north and a 10 to 15 knot crosswind prevailed at the strip. A take-off into the east was commenced, the aircraft became airborne and as it crossed the upwind end of the strip, it was affected by a sudden gust of wind. The aircraft yawed to the right, lost altitude and struck the ground, before coming to rest in a ploughed paddock. At the time of the attempted take-off the location of the approaching storm was conducive to the presence of strong downdraughts or possibly microbursts in the vicinity of the strip. The pilot elected to commence the take-off because he was concerned that heavy rain at the strip would have rendered it unserviceable.

When the pilot arrived at his planned destination, he was unable to obtain a down and locked indication for the nosewheel. Both normal and emergency means of lowering the gear were employed, but without success. A diversion was made to a more suitable aerodrome, where a safe landing was made with the nosegear retracted. It was determined that the hinge on the left door of the nosegear assembly had seized because of corrosion. On the previous retraction, the door linkages had been forced out of position in such a manner that the gear doors were jammed closed. All required maintenance and inspections had been certified as being completed, and it was not possible to determine how the hinge had become corroded.

A series of demonstration flights had been arranged by the aircraft owner. The weather was clear and sunny, with occasional wind gusts up to about 5 knots. Thermal activity was reported in the area. The pilot was the manufacturer of the aircraft, which was sold in kit form. Although he had considerable experience on the aircraft type, he was not familiar with flight in thermalling conditions. After conducting three short demonstration flights with a passenger on board on each occasion, the pilot arranged with the owner to carry out a solo flight to gain thermalling experience. Witnesses reported that the ground roll appeared to be normal, but the aircraft commenced a turn at about 10 feet above the ground while climbing at an unusually steep angle. After the aircraft had reached a height of about 100 feet the climb angle was seen to steepen further, and shortly afterwards the left wing dropped and the aircraft entered a spin. The rotation ceased after one and a half turns with the aircraft then in a steep nose-down attitude. Recovery from this dive was apparently being made when the aircraft struck the ground. No evidence of any mechanical failure or defect was subsequently found. It was considered probable that the unusually steep climb attitude was the result of either the pilot's wish to demonstrate maximum performance, or the unexpected effects of a thermal. The pitch-up which occurred before the stall and subsequent spin was possibly related to the thermal activity.

Shortly after take-off a loud banging noise was heard from the inboard area of the right wing. The pilot elected to fly a low level circuit and land to investigate the noise. On short final approach heavy sink was encountered, and despite the application of power the aircraft touched down about 100 metres short of the runway. It ran through the airport boundary fence and came to rest near the flight strip with the gear collapsed. Investigation revealed that a section of the door seal had become unstuck and had trailed in the slipstream, beating against the door. The pilot had believed that the aircraft had suffered a serious malfunction and was anxious to land as soon as possible. Her husband, who occupied the right front seat, was a more experienced pilot. However, he did not offer to take control of the aircraft. It was probable that the airspeed during the approach was less than the optimum. When sink was encountered, the power and control inputs which were applied were insufficient to prevent the aircraft striking the ground in a semi-stalled condition.

Circumstances:

The pilot said the preflight engine run-up was normal, although the engine seemed to run roughly with a slight RPM drop when carburettor heat was applied. A take-off was commenced but the pilot did not think engine performance was normal. After becoming airborne the engine ran roughly and lost power. The throttle was closed, and the aircraft was landed straight ahead on the strip remaining. However, the aircraft overran the strip end and collided with a fence. The pilot reported that wasps had nested in the intake ducting whilst the aircraft had been idle and uncovered during the previous few days. The nest had apparently dislodged during the preflight run-up causing eventual power loss after take-off. This accident was not the subject of an on-scene investigation.