On touchdown following a superphosphate spreading operation, the pilot heard a loud cracking noise from the left side of the aircraft. Shortly afterwards the left mainwheel detached, the aircraft swung sharply and tipped onto its nose, before coming to rest in an upright attitude. The left mainwheel axle was found to have fractured. The left axle had been in service for 7452 flight hours, and was estimated to have been involved in about 70,000 landings. The failure was determined to have initiated from fatigue cracking, which had propagated through about 60 percent of the axle diameter before the axle ultimately failed from overload forces.

During take-off, with the first officer at the controls, the captain noticed that the aircraft cabin was being affected by pressure surges. He selected the airconditioning automatic shutdown switch to "override" and also selected manual operation of the outflow valves, to control the cabin altitude. The cabin altitude was controlled successfully at 7000 feet until, with the aircraft at 20,000 feet on climb, the cabin altitude began to climb without pilot control input. An emergency descent was carried out, at an average of 4200 feet per minute, and the aircraft levelled at 7000 feet. During the descent the cabin altitude reached a maximum height of 12,000 feet and when the aircraft had levelled at 7000 feet, the cabin altitude was some 2000 feet below sea level. This change of cabin altitude is estimated to have occurred over a period of three minutes. The cabin altitude was raised to 2000 feet above sea level and the aircraft was depressurized for landing. The failure at take-off was caused by a faulty pressure switch in a system intended to shutdown the airconditioning systems in the event of an engine failure on take-off. Later in the climb a clamp failure in the airconditioning cooling air duct led to the shut-down of at least one airconditioning pack. During a period of high cockpit workload the pressure and temperature gauges associated with the airconditioning systems were not closely monitored. The selection of manual cabin altitude control aggravated the fluctuations in cabin altitude experienced during the flight.

After lift-off at 85 knots, the pilot noted a positive rate of climb before retracting the landing gear and flaps. He then felt the aircraft sink and noted a high indicated rate of descent. Although full power was applied the descent continued until the aircraft struck the runway in a slightly nose-up attitude. The aircraft slid across the overrun area and through a fence before coming to rest. Fire broke out and engulfed the wreckage. At the time of the accident the aircraft weight was more than 200 kg above the maximum allowable and the centre of gravity was 142 mm forward of the forward limit. The pilot had been unable to retain control of the aircraft during the initial climb phase when the flaps were retracted at a relatively low airspeed.

Severe turbulence had been encountered on final approach but smooth air was entered on short final. After flaring to land, the aircraft rolled left rapidly and the landing was made on the left main wheel, followed by the right and nose wheels. The pilot subsequently inspected the aircraft but did not detect any damage. After two further flights the pilot noticed that the left wing appeared to be low. Distortion of the left main gear support frame was found.

As the pilot was attempting to locate the airstrip at his destination, he noticed some of the aircraft's electrical equipment had failed. He decided to proceed to Bourke and land. On arrival over Bourke the pilot selected the gear down but did not obtain any indication of the gear position. He then manoeuvred the aircraft in an effort to assist gear extension but did not attempt to use the manual override system. The aircraft was landed with the gear retracted. The alternator and engine pulleys were out of alignment resulting in the drive belt becoming detached. The handling notes were carried in the rear luggage locker, out of reach of the pilot and because the operation of the emergency gear lowering system could not be remembered a wheels up landing was made.

The student pilot was undergoing a conversion onto the aircraft type. As part of the conversion, the instructor closed the throttle and requested the student to demonstrate a forced landing. At about 600 feet, the instructor, being satisfied with the exercise, advised the student to go-around. The throttle was opened but the engine did not respond. The instructor took control but was unsuccessful in his attempts to restart the engine. The aircraft was landed in a paddock and ran through a fence. The exercise was carried out conforming to the checklist requirements, one of which was to switch the fuel boost pump on. Investigation revealed that the engine would not idle with the pump on. The engine had been out of service, unpreserved, for 17 months and the fuel regulator diaphragm was sticking to its guide and seal assembly causing the engine to run rich at idle and stall. Although the instructor took control at 600 feet, attention was diverted from the forced landing to restarting the engine.

After arriving in the area the pilot was unable to locate the destination strip. He decided to land on a gravel road near a house to seek directions. Shortly after a normal touchdown the nosegear collapsed and the aircraft came to rest in a drain beside the road. The pilot reported that there had been nosewheel shimmy during the previous take-off and just prior to the nose leg collapsing. The pilot had not previously operated into the strip at his intended destination. The nose wheel tyre was found to be deflated, and it is likely that it had become deflated during the previous take-off. However, due to the extent of the damage caused to the tyre during the landing, it was not possible to determine the reason the tyre had become deflated.

During spraying operations the engine suffered a partial power loss. The pilot initiated dumping of the hopper load but was unable to prevent the aircraft from striking the ground heavily. The landing gear collapsed and the aircraft slid for about 50 metres before coming to rest. The reported power loss had occurred during a procedure turn, the latter portion of which was downwind. No fault was subsequently found with the engine, however it was considered likely that the aircraft was affected by downdraughts in the lee of a hill. When dumping was initiated, the pilot's left sleeve had probably caught on the throttle lever and pulled it towards the closed position.

Circumstances:

The pilot reported that he was spraying a crop with the runs oriented in a racetrack pattern across the wind, which was south-easterly at 15 knots. This resulted in a turn into wind at one end and a turn downwind at the other end. He experienced difficulty in preventing the aircraft drifting away from the paddock during the downwind turns and was widening the turns in an attempt to correct the problem. During the third downwind turn the aircraft stalled but the pilot was unable to level the wings due to trees in the path of the aircraft. The right wing struck a fence and cartwheeled into a paddock.

Circumstances:

The pilot reported that on arrival at Dunk Island he made a normal approach for runway 14, and on final approach at a height of about 50 feet he encountered a sudden downdraft. The aircraft landed heavily on the left main gear before he could reduce the sink rate. The pilot stated that he subsequently examined the aircraft but did not notice any signs of damage. The damage was discovered after the pilot had returned to Townsville and reported that he had made a heavy landing to the operator. The landing impact had damaged the gear attachment by displacing it vertically upwards, a rib was bent, and rivets were pulled on the lower wing skin. The spar was bent but returned to its normal shape when damaged skin was removed. The pilot stated that the wind at the time of the accident was southeasterly at about 10 -15 knots, and that he had not previously landed at Dunk Island.