What happened
Following takeoff, the pilot of the aircraft selected the landing gear-up position, but noted that the corresponding position light failed to illuminate. Upon checking the landing gear motor circuit breaker, the pilot discovered it had tripped. Subsequent attempts to extend or retract the landing gear were unsuccessful.
After attempting an emergency landing gear extension, the destination airport control tower verified via a fly-by that the landing gear remained not fully extended. Consequently, the pilot decided to retract the gear as much as possible and execute a wheels-up landing in a grass area adjacent to a runway. The aircraft sustained substantial damage to a fuselage bulkhead during the landing.
The investigation
An inspection of the aircraft revealed that the right main landing gear was partially extended, with the wheel and lower strut assembly rotated within the wheelwell. Investigators found that the bolt attaching the upper and lower portions of the torque link assembly had sheared in half. This failure caused the lower torque link to jam against the wheelwell structure, which restricted the movement of the entire landing gear assembly.
Analysis of the bolt fracture features indicated they were consistent with shear overstress resulting from torsion during the action of the torque link assembly. No evidence of fatigue cracking was found on the fracture face. Additionally, the separated sections of the bolt were found to be seized within the upper and lower torque links due to surface corrosion.