Cessna 150-G, VH-KOK, Redcliffe Aerodrome, Queensland, on 25 July 1989

Circumstances:

The aircraft had been fitted with a tailwheel conversion prior to being imported from the USA. During a touch and go landing, the aircraft was decelerating in the three point attitude through about 20 knots, when the pilot lost control in a violent swing and wing drop to the right, followed by an immediate reversal to the left. The right main gear had separated from the fuselage during the landing roll. The main gear locating bolt and saddle bolts had been fitted incorrectly and were thread bound, allowing the gear leg to place abnormal loads on the saddle. It failed progressively until final overload failure during this particular landing. The aircraft had flown only 13 hours since being placed on the Australian Register. It was imported with the main gear undisturbed. The progressive mode of failure suggests that evidence of impending failure of the saddle should have been apparent for some considerable time.

Significant Factors:

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

1. Improper fitment of Tailwheel Conversion Kit by USA maintenance organisation.

2. Overlength bolts holding right main gear were thread bound before the correct clamping tension was achieved.

3. One of the two cast metal saddle sections which locate the gear leg laterally in the fuselage had failed due to fatigue and overload.

4. During the inspection for the issue of a Certificate of Airworthiness, the maintenance organisation did not discover the incorrect installation of the tailwheel kit.