On July 28, 1995, a North American AT-6F (registration N3173L) was involved in an aviation accident near Long Beach, CA. Investigators recorded the probable cause as: the failure of the left main landing gear locking mechanism to fully seat in the 'down' position due to loose attachment bolts. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During a crosswind landing, the left main landing gear collapsed after touchdown, causing the aircraft to veer right and exit the runway, striking a sign. Investigation found the mechanical down lock broken and displaced due to improperly seated bolts.
Accident Sequence
As the pilot rolled out on final approach, he recognized a crosswind condition and initiated a crab into the wind in preparation for a crosswind landing. Following touchdown, the aircraft experienced a sudden veer to the right. The left main landing gear subsequently collapsed. The aircraft continued off the right side of the runway and collided with a sign mounted on a concrete base.
Pilot Control Inputs
During the landing, the pilot was applying right aileron and left rudder to compensate for the crosswind.
Landing Gear Examination
Post-accident inspection revealed that the mechanical down lock for the left main landing gear was broken and dislodged. The mechanical gear position indicator did not show that the left main gear was in the down and locked position. The bolts securing the down lock were found not properly seated, which allowed the down lock to shift from its correct mounting position.