What happened
The aircraft had previously exhibited an unsafe indication for the right main landing gear several days before the incident. Maintenance personnel identified a damaged micro switch mounting plate and performed a temporary repair sufficient to hold the component in place until a new part could be ordered and installed.
On the day of the accident, the pilot received an unsafe right main gear indication during approach. Upon initial touchdown, the pilot applied a side load to the gear to verify its security. This action resulted in a loud bang from the right main gear area, causing the gear to begin collapsing. A balked landing was executed. During the second landing attempt, the right gear collapsed again.
The pilot returned the aircraft to the departure airport. Upon final landing, the right main gear fully collapsed, resulting in substantial damage to the airframe.
The investigation
Post-crash inspection revealed that the right gear overcenter brace had failed along with its mounting bolt. A metallurgical examination of these components indicated failure due to overstress. There were no signs of pre-existing cracks or corrosion on the failed parts, suggesting the damage was acute rather than progressive.
Findings
The temporary repair of the micro switch mounting plate likely altered the load path or alignment of the gear indication system, but the critical failure was mechanical. The pilot's action of placing a side load on the gear during the first landing attempt initiated the collapse sequence. The overcenter brace, designed to lock the gear in the down position, failed under the stress of this maneuver.
Safety message
Temporary repairs on landing gear systems must be evaluated for their impact on structural integrity and operational safety. Pilots should avoid placing lateral loads on landing gear unless specifically instructed by the manufacturer or maintenance procedures.