Hughes Lightwing LW-02, 25-0081, Oakdale, New South Wales, on 25 February 1989

Circumstances:

About twelve minutes after departure and while cruising at 1200 feet above the ground the engine speed reduced from 5200 to 2000 rpm. This was accompanied by a mechanical knocking noise and severe vibration. The pilot immediately shut down the engine down to prevent possible damage. He carried out an emergency landing into the most favourable area within gliding distance. On touchdown the aircraft decelerated rapidly nosed over and came to rest inverted. It was not apparent from the air that the grass in the paddock was about half a metre high. The crankshaft had fractured at the centre pin between the bearing and the helical gear. The fracture was caused by fatigue attributed to extensive cracking. It was not possible to determine if the cracking had been present since manufacture or initiated from a propeller strike event some 60 hours prior to the failure when the engine was installed in a different aircraft. No logbooks are required for this type of engine hence the complete history of the engine could not be determined. This accident was not the subject of an on-scene investigation.

Significant Factors:

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

1. Engine crankshaft failed due to fatigue.

2. Long vegetation in emergency landing field.

Recommendations:

It is recommended that the Civil Aviation Authority consider a requirement for airframe and engine logbooks for this category of aircraft particularly those with the potential for commercial operations such as flying training.