What happened
During the approach to Detroit, the pilot observed an unsafe indication regarding the right main landing gear after attempting to lower the gear. In an effort to resolve the issue, the crew cycled the landing gear, but the warning light persisted. Consequently, the crew retracted the gear and diverted to Detroit for an emergency landing.
Upon arrival, the crew executed the landing gear abnormal extension checklist, yet the unsafe indication remained active. Although air traffic control personnel observed that the gear appeared to be in a normal position, the right main landing gear retracted while the aircraft was on the ground during the landing phase. This caused the aircraft to slide sideways, where it subsequently struck a runway marker and exited the runway, eventually coming to a stop in an adjacent field. There were no fatalities or injuries reported during the incident.
Findings
Post-accident investigations determined that the right landing gear downlock mechanism could be bypassed using physical force. A detailed inspection of the right landing gear actuator identified that one of the six shims, which are designed to separate spacers and assist in guiding the safety lock switch, had moved out of its proper position and was resting on top of the lock assembly.