Beech A36, VH-WMK, Lightning Ridge, New South Wales, on 6 October 1989

Circumstances:

The aircraft was involved in local flying. On the final landing and during touchdown, the landing gear collapsed, and the aircraft slid to rest on the runway. The pilot advised that the landing gear selector switch had been accidentally bumped to the ‘UP' position by the knee of the front seat passenger. Inspection of the landing gear selector switch revealed that the plastic identification knob had been screwed too far onto the switch arm. This rendered the locking function of the switch ineffective.

Significant Factors:

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

1. Poor design of the plastic identification knob of the landing gear selector switch.

2. Screwing the plastic identification knob too far onto the landing gear selector switch rendered the locking function ineffective.

Recommendations:

1. That the Civil Aviation Authority publish an Airworthiness Advisory Circular article to advise maintenance personnel that the safety lock function of the landing gear selector, (as used in many general aviation aircraft) will be compromised if the plastic switch knob is screwed on too far.

2. That an article be published in the BASI journal to advise pilots of retractable landing gear general aviation aircraft, not to attempt to tighten the landing gear selector switch knob if it ever comes loose. This action may render the locking function inoperative, as it may only need one half turn for this to happen.