The aircraft had been issued with an airways clearance to track from Ballidu to Perth. It was observed on radar to be diverging from this track until queried by Perth Air Traffic Control. The aircraft then turned in the appropriate direction but did not track directly for Perth until radar vectors were supplied. Maximum displacement from the cleared track was about 31 kilometres. The situation was constantly monitored by Air Traffic Control and no confliction occurred with any other aircraft. After landing the Captain advised that the primary navigation aid the Inertial Navigation System was giving erroneous information as to the actual position of the aircraft. Subsequent ground checking of the equipment failed to reveal any serious fault. It was considered that either the original computerised programme loaded into the aircraft system at Djakarta was faulty or the crew might have inadvertently introduced an error. Nevertheless other navigation equipment was apparently operating satisfactorily and would have indicated that the aircraft was not on the desired track. The procedures used by the crew to cross-check navigation information were not established. It was determined that the pilot who was a senior pilot in the company was conducting training to allow a First Officer to be promoted to Captain. It was possible that while concentrating on the training task the Captain allowed his attention to be diverted from the operation of the aircraft.

The pilot reported that he was flying straight and level at 200 feet above ground level(AGL) and about 55 knots when the aircraft sideslipped to the left and nosed over. The nose continued to drop to the almost vertical position and the speed built up to 60 knots. At about 100 feet AGL, the pilot attempted to pull out of the dive but the aircraft did not respond and struck the ground in the almost vertical nose down attitude. Eyewitnesses reported that the aircraft was in the circuit area when they saw a wing drop and the nose of the aircraft fall sharply. The AUF Safety Officer reported that the flying surfaces of the aircraft were undamaged and he suspected that a stall/spin DEPARTURE was experienced by the pilot. In addition to cuts and bruises, the pilot suffered compound fractures to both legs and his right arm. This accident was not the subject of a formal on scene investigation.

The pilot reported that he made a normal approach to land into a 10-15 knot wind. The flare for landing was initiated but the aircraft landed heavily, making first contact on the right mainwheel. The initial touchdown was some 8 metres beyond the boundary fence, 96 metres short of the strip end and 166 metres short of the marked threshold. The aircraft then bounced and touched down again on the strip 220 metres beyond the initial touchdown point. The pilot recalled that at this point he heard the landing gear warning horn sound and noticed that the right main gear safe indication light had gone out. The right wing then collapsed slowly and the aircraft slewed through 180 degrees as it came too rest on the wingtip about 550 metres from the first ground contact. There was some evidence that the approach was lower than usual and that windshear was present on the approach path. The right main undercarriage leg collapsed due to an overload failure of the bellcrank lugs.

The pilot had refuelled the aircraft to full tanks the previous day and then flown a total of 1.6 hours. On the day of the accident he completed a flight from Darwin of 1.1 hours duration. Four minutes after leaving Cooinda, at an altitude of 1000 ft, the engine failed and the pilot's attempts to restart the engine were unsuccessful. A forced landing was attempted into a short clearing but the aircraft over-ran the clearing and collided with trees. Investigation established that the pilot used the left tank but mistakenly recorded flying on the right tank for 1.6 hours the previous day and used the left tank again for 1.1 hours on the trip to Cooinda. On-site investigation established that the intact left tank was empty and right tank, although leaking, contained a significant amount of fuel. Other evidence established that the fuel gauges were not serviceable and the pilot did not select the electric boost pump to ON after changing tanks in his attempt to restart the engine. A series of engine run tests carried out after the accident showed no fault with the engine, and that the engine would recover after fuel exhaustion on one tank if the electric boost pump was selected ON after changing tanks.

As the aircraft became airborne the pilot heard a loud bang and upon inspection noticed that the left flap was holed and buckled. The elevator trim had also been damaged and was immovable. This resulted in the aircraft tending to fly in a nose high attitude. The pilot assumed that one of the mainwheels had been dislodged and decided to fly the aircraft to Townsville where emergency services were available. Enroute he was contacted by radio from Scartwater Station and advised that the aircraft was missing a mainwheel. After the pilot received advice from a flying instructor, the aircraft was successfully landed at Townsville. An inspection of the aircraft revealed that the left landing gear torque link bolt had failed as a result of fatigue cracking which had originated from a poorly machined lubrication groove.

The pilot had only recently regained flying currency and was inexperienced on type. He had suffered some frustration in gaining dispensation to return to Alice Springs without radio, and in having to vary his plans to stop off en route with his passengers who were also disappointed at the change in itinerary. On arrival at Alice Springs, the pilot joined the circuit for the non-duty runway which was out of wind. During the attempted cross-wind landing, the aircraft bounced and ballooned and the pilot did not take the correct recovery action. The aircraft landed heavily on the right wheel and then onto both main wheels. The pilot reported that he did not attempt to go-around off the bounced landing because he lacked the confidence to execute this manoeuvre with the aircraft configured with full flap. A subsequent inspection revealed damage to the right maingear leg which required replacement.

The aircraft was being used to spread urea. The day's operations had commenced late because of morning fog. On becoming airborne on this particular occasion the pilot commenced a low-level shallow right turn to avoid a stand of trees and to track to the nearby treatment area. However, on entering the turn the pilot noticed that he was tracking towards a solitary small tree so he rolled the aircraft to wings level to avoid this obstacle. He was aware that this track would take him towards a strand of trees, but he was unable to determine his distance from them because of sun glare on he windscreen. The aircraft struck trees on the edge of the strand at a height of about 10 feet above ground level then impacted the ground. The left main gear leg was torn off and the aircraft slid to a halt. The flight was the pilot's sixteenth takeoff from the strip for the day. He was aware of all the obstructions, but was evidently affected by a number of factors which can be associated with agricultural operations. These included a build-up of urea dust on the windscreen; high workload; the need to pre-plan the next stage of the operation etc. These factors probably led the pilot to temporarily forget the locations of the various obstructions in the area.

The pilot reported that he was mustering in a creek bed when one of the cattle ran at the helicopter. As he manoeuvred to avoid the beast, the tail rotor contacted a tree, destroying the tail rotor and associated gearbox. The aircraft was landed without further damage. This accident was not the subject of an on-site investigation.

The pilot had arrived back at his ALA late in the afternoon, when the sun was low in the western sky. Recent heavy rain had made the surface of the 900 metre long ALA wet and soft, and only 300 metres at the eastern end of the strip was considered to be serviceable. He was reluctant to land to the east as the strip was down hill in that direction and a slight westerly wind was blowing at the time. He was concerned that braking would be ineffective on the wet grass, and also cause problems with directional control. Because he noticed cattle moving towards the ALA, the pilot, who had been waiting for the sun to sink below the horizon in order to land to the west, decided to make an immediate landing in that direction. The pilot landed near his aiming point along the strip, but because the sun was in his eyes obscuring his vision he failed to line up along the centre line. The aircraft touched down on the soft edges to the left of the strip, and during the landing roll the mainwheels sunk into the soft ground causing the aircraft to roll over onto its back. This accident was not the subject of an on-site investigation.

Circumstances:

The aircraft was being flown on an air test after a previous flight incurred a defect with the emergency gear extension system. The test was conducted in the Bankstown training area and all gear extensions both normal and emergency worked correctly. On return to Bankstown for landing on runway 29 Right the landing gear was lowered on downwind in the circuit and the normal three green indication was noted. The approach and landing was normal until just as the nosewheel touched the runway the right main gear collapsed, and the aircraft skidded to a halt to the right of the centreline. Subsequent investigation revealed the right main gear jury strut pin had separated from the attach bracket on the rear spar. The strut pin retaining circlip had been incorrectly fitted during the last installation.

Significant Factors:

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

1. Improper maintenance.

Recommendations:

The jury strut spar bracket P/N TB20.43.013.000 L/H or .001 R/H is supplied as an assembly ex-factory consisting of the bracket and two bushes. Unless the bushes are fully inserted in the bracket the locking characteristics of the circlip on the pin may be compromised. The jury strut pin retaining circlip cannot be inspected in-situ on MSTB20 aircraft. It is therefore recommended that the Civil Aviation Authority consider notification to owners and operators of MSTB20 aircraft that a defect may exist and detail a procedure to check the integrity of the circlip and jury strut pin.