What happened
Following takeoff, the pilot observed that the nose gear unsafe indicator light remained illuminated despite initiating the gear retraction sequence. Subsequent attempts to confirm the nose gear was safely locked in the extended position were unsuccessful. The aircraft continued its flight and landed with the nose landing gear in a partially retracted state, resulting in the strut settling onto the runway.
The investigation
Post-accident examination of the airframe revealed that the nose gear strut had not achieved full extension prior to the landing impact. During the retraction cycle, the nose gear tires made contact with the nose gear doors, physically preventing them from opening fully. This obstruction caused the gear to retract against the closed doors, leading to a mechanical failure of the retract jackscrew.
Further inspection identified that a critical microswitch, designed to cut power to the gear motor when such an obstruction occurs, was found out of adjustment and failed to operate. The investigation determined that the mechanics performing the last gear retraction test had utilized a maintenance manual for an earlier aircraft model. This older manual did not include procedures for checking this specific safety switch, resulting in the oversight.
Findings
The failure to extend the nose gear fully was attributed to a combination of mechanical obstruction and inadequate maintenance procedures. The primary contributing factors included:
- Failure of the retract jackscrew due to retraction against closed doors.
- Misadjusted microswitch that failed to stop the gear motor during the obstruction.
- Use of an incorrect maintenance manual by mechanics, which omitted the necessary check for the safety switch adjustment.
No mechanical reason was found for why the nose gear strut initially failed to fully extend. The root cause lay in the maintenance error and the subsequent failure of the safety mechanism to detect the jammed condition.