The aircraft was being flown by the pilot under supervision. Touchdown was made 450 metres beyond the threshold of the strip. The pilot applied heavy braking and the aircraft began to skid and slide sideways down the strip. About 560 metres after touchdown, the right hand main gear over centre-lock released due to the side loads imposed. These loads were transmitted to the braze rod which failed, causing the gear to collapse. The right wingtip and propeller struck the ground.

Circumstances:

The pilot was conducting an agricultural seeding operation into a cleared paddock which was heavily timbered along its western boundary. The swath runs were in an east/west direction, with a left hand procedure turn at the completion of each run. The pilot reported that during the procedure turn at the western end of the paddock, the stall warning sounded, and the aircraft commenced to sink. The pilot attempted to dump the load but was unable to activate the hopper dump door. The aircraft stalled from a height of approximately 100 feet above ground level, impacting the ground in a nose and left wing low attitude. The pilot could not recall a loss of engine power during the procedure turn. The investigation did not reveal any airframe deficiency which could have contributed to a loss of performance. A subsequent bulk strip of the engine revealed that the number six cylinder exhaust valve pushrod was bent, and the associated valve was sticking. It is considered likely that these defects would have contributed to a loss of power. However, the precise reason for the loss of performance could not be determined. The reason why the pilot was unable to dump the hopper load could not be determined.

Significant Factors:

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

1. The aircraft lost performance during the procedure turn.

2. The number six cylinder exhaust valve pushrod was bent, and the valve was sticking. This accident was not the subject of an on-scene investigation.

The pilot reported that he had made five spray runs and was completing a procedure turn when the aircraft began to sink. He immediately applied full throttle and maximum RPM but the aircraft did not respond. The pilot stated that while his attention was on avoiding some tall trees, he was unable to grab the dump cable handle. The aircraft impacted the ground, nosed over, and came to rest inverted. The cockpit was immediately engulfed in flames, but the pilot was able to free himself and escape through the left side hatch. The aircraft exploded shortly after the pilot had vacated. The engine was torn out by impact and was thrown clear of the fire. The engine was later test run satisfactorily and was considered to be capable of developing full power.

Shortly after reaching the cruising level of flight level 310, the aircraft encountered a severe downdraft. The seat belt sign had been on since DEPARTURE. However, one passenger was thrown into the overhead panel and fell back on to the seat arm rest, receiving five broken ribs. No fault was found with the seat belt or its buckle. The reason the passenger was not strapped in at the time of the occurrence could not be determined. Although the aircraft was in cloud at the time, no weather radar returns had been received. Severe turbulence had been forecast for the area.

Circumstances:

The pilot intended to conduct spreading operations on nearby sugar cane fields. During the latter part of the first take-off of the morning, the aircraft failed to lift off as anticipated and entered a sugar cane field at the end of the airstrip. The pilot discontinued the take-off, but the aircraft was substantially damaged when it ran into a ditch, in which lay several disused telegraph poles. The pilot reported the aircraft encountered an isolated tailwind gust during the take-off. He said he attempted to dump the load but was unsuccessful due to the damp condition of the fertiliser.

Significant Factors:

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

1. The aircraft encountered an isolated tailwind gust during the critical stage of the take-off.
2. The load did not dump due to its damp condition.

Circumstances:

The aircraft was engaged on a scheduled international passenger flight. Between Narita and Guam, the aircraft weather radar was used to avoid unforecast, isolated cumulonimbus cloud formations. Approaching Guam, the flight conditions were smooth with the aircraft flying through cirrus cloud. The Captain and Second Officer, who were on duty on the flight deck, were monitoring the weather radar. A heading change to the right of track was required to avoid weather activity observed by radar over the island. Whilst regaining track, the aircraft encountered an area of severe turbulence lasting for approximately 30 seconds and resulting in vertical accelerations of +1.8G and -0.4G. Forty passengers and two cabin attendants were injured. At the time of the encounter the seat belt signs were off and most of the injured passengers were asleep with their seat belts undone. The Captain illuminated the seat belt sign immediately the turbulence was noticed. The injured were treated by the cabin crew and a passenger who was a qualified medical practitioner. The Captain was advised that none of the injured required immediate specialised treatment and, as the aircraft did not sustain any significant damage, he decided to continue the flight to Sydney. The airline company was notified, and the aircraft was met by medical staff on arrival. Twenty-eight passengers and cabin crew were conveyed to hospital for further treatment. It was determined the aircraft had encountered an area of turbulence associated with cumulonimbus cloud which was not detected by the aircraft weather radar. Although the seat belt signs were not illuminated, passengers were advised during an after-take-off announcement, to keep their seat belts fastened when seated. These announcements were made in English and Japanese languages.

Significant Factors:

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

1. The aircraft encountered an area of turbulence undetected by the aircraft weather radar.

2. The seat belt sign was not illuminated.

3. Many passengers who were sleeping, did not have their seat belts fastened.

4. The cumulonimbus cloud formations in the vicinity of Guam were not forecast.

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.