Circumstances:

The pilot was landing at a property prior to conducting crop spraying. During the landing roll, the aircraft veered off the strip and overturned in a wheat crop. A subsequent investigation established the left mainwheel hub had failed due to a fatigue crack, allowing the wheel to travel up the landing gear leg. A partial collapse of the left leg then resulted when the axle dug into the ground. The crack had originated from corrosion pitting on the inner wheel half interior surface, which was not visible with the wheel in situ.

The approach was made with full flap extended at an indicated airspeed of between 75 and 80 knots. As the pilot closed the throttle in preparation for landing, the handle of the throttle lever came off in her hand. The aircraft struck the runway heavily and bounced several times, collapsing the nose gear leg. The pilot had been distracted when the throttle lever handle separated during the landing flare. The handle had been attached by an unsuitable retaining bolt.

The pilot stated that when braking was applied after touchdown, the aircraft did not decelerate normally. A go around was carried out, and after the aircraft became airborne, the nosewheel struck a fence. As a result the nosewheel became misaligned and the nose gear collapsed during the subsequent landing at Townsville. Upon arrival the pilot had to orbit for 5 minutes to allow a rain squall to pass. Without overflying the strip he assessed that the wind favoured a landing direction which placed him presently in a wide base position. Due to standing water on the grass strip and a tailwind component, deceleration was minimal. By the time a go around was initiated the aircraft had entered an area of long grass. The flaps were left in the landing position during the go around, this further increased drag and added substantially to the ground run.

Shortly after VH-TJS entered the circuit for runway 14, as number three to land behind two light aircraft, the Aerodrome Controller (ADC) commenced vectoring a Boeing 737 aircraft for descent and approach to land on the opposite direction runway 32. On short final the pilot in command of VH-TJS became aware of aircraft lights approaching from the opposite direction. Shortly afterwards the Boeing crew advised that the aircraft was on final for runway 32, and was instructed by the ADC to continue the approach. The pilot in command of VH-TJS initiated a go-around from a height of about 100 feet above the ground. The Boeing 737 was then cleared to land, and VH-TJS carried out a circuit and landing on runway 14. The pilot of VH-TJS subsequently stated that he was not told of the opposite direction traffic, and said he believed the other aircraft to be following him for a landing on runway 14. Investigation revealed that, during the vectoring process, the ADC specifically mentioned that the other aircraft was for runway 32 on three occasions. At the time VH-TJS commenced the go-around the Boeing 737 was about 4 miles (7.5 kilometres) from the end of the runway at about 1000 feet altitude. There was no breakdown in separation standards or Air Traffic Control procedures.

The aircraft was crossing the threshold, about 300 metres behind an Iroquois helicopter, when the right wing dropped. The nose also dropped and the nosewheel contacted the runway heavily and was broken off. The aircraft slid along the runway for some 200 metres on its nose before coming to rest. The aircraft evidently encountered the wake turbulence created by the helicopter.

The pilot reported that the take-off proceeded normally until the point of lift off, when the engine hesitated and lost power for about 3 seconds. Power was then regained, however the pilot was not certain whether full power was developed. He elected to abandon the take-off, but there was insufficient strip length remaining in which to safely stop the aircraft. He then reopened the throttle in an effort to clear a fence at the end of the strip and land in the adjoining paddock. The noseleg struck the fence, and the aircraft then ran through a ditch before coming to rest. The reason for the short term power loss could not be determined

The pilot had been authorised to carry out circuit and landing practice. He had been operating for about 20 minutes when witnesses observed that immediately after lift-off from a touch and go landing, the aircraft assumed a higher than normal nose attitude. At an height of between 100 and 150 feet above the runway, the engine noise ceased and the aircraft pitched forward to a steep nose down attitude. This attitude was maintained until the aircraft impacted the ground, before coming to rest 50 metres to the right of the runway centreline. A subsequent investigation determined that the pilot had probably suffered a heart attack at about the point of lift-off, resulting in incapacitation and loss of aircraft control.

The aircraft departed with a planned fuel endurance of 170 minutes, and an expected flight time of 116 minutes. About 110 minutes after take-off the engine lost power and the pilot was forced to land on unsuitable terrain. The aircraft sustained damage to the wings, landing gear and rear fuselage as it ran through two fences and came to rest after striking several trees. Initial inspection revealed that the spring loaded fuel drain cock for the right tank was in the open position. The aircraft was parked on wet grass when the pilot conducted the fuel drain check and he evidently did not visually check to ensure that the right wing drain cock had resealed. When the engine lost power the pilot switched the electric fuel pump on before changing tanks. This sequence is the reverse of that recommended by the manufacturer and increases the time taken to effectively restore power. Adequate fuel had remained in the other tank to allow completion of the flight, had engine power been regained.

The pilot was landing on a property strip in gusty crosswind conditions. Directional control was lost during the landing roll and the pilot was unable to prevent the aircraft from running off the side of the strip. As he attempted to taxi the aircraft back onto the strip the nosewheel entered an area of soft sand and subsequently collapsed. The particular strip in use was only 20 metres wide, and consequently did not meet the requirements for an Authorised Landing Area. The strength of the crosswind component could not be determined.

During climb, at about 2500 feet, a loud noise was heard from the engine coincident with a power loss and severe vibration. The choice of suitable forced landing areas was restricted by the strong wind and the terrain features. The aircraft touched down 188 metres from a fence and levee banks either side of a narrow irrigation channel. An attempt to avoid the fence and levee banks by overflying to an adjacent paddock was unsuccessful because of low airspeed. The aircraft collided with the levee, catapulted over the channel and came to rest 15 metres beyond. It was determined that the loss of power was due to a spark plug, complete with heli-coil, becoming dislodged from the Number 1 cylinder. The cylinder had been installed on the engine 7 flying hours previously, after being repaired by an approved organization. The most probable cause of the defect was overtorquing of the spark plug during installation, thereby damaging the tapped alloy of the cylinder into which the heli-coil had been screwed. With this thread damaged, the spark plug was able to vibrate to further damage the alloy thread. Exhaust gas escaping between the tapped thread and the heli-coil accelerated the damage process until eventually the spark plug was ejected by engine combustion pressures.