On May 21, 1985, a Mitsubishi MU-2B-20 (registration N711LL) was involved in an aviation accident near San Angelo, TX. Investigators recorded the probable cause as: The nose landing gear failed to extend due to an obstruction caused by equipment that was not properly secured during previous maintenance, which shifted due to aircraft vibration. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
An aircraft landed with its nose gear retracted after unsecured maintenance equipment shifted due to vibration, blocking the extension mechanism.
What happened
A landing was executed with the main landing gear down and locked, while the nose gear remained in the fully retracted position. The incident occurred because the nose gear failed to extend prior to touchdown.
The investigation
Investigation revealed that a piece of unidentified equipment had not been properly secured during previous maintenance work. This loose component was mounted immediately above the nose wheel extension and retraction mechanism. During flight, aircraft vibration caused the unsecured equipment to shift position. The displaced object physically obstructed the mechanical linkage, preventing the nose gear from extending.
Findings
The primary factor contributing to the event was the failure of the nose landing gear to extend. This malfunction was directly caused by an obstruction in the retraction mechanism. The obstruction consisted of equipment that had been inadequately secured during prior maintenance activities. Vibration during flight moved this loose item into a position where it blocked normal gear operation.
Safety message
Proper securing of all components during maintenance is critical to prevent foreign object debris or loose items from interfering with flight control systems and landing gear mechanisms.
Probable cause
The nose landing gear failed to extend due to an obstruction caused by equipment that was not properly secured during previous maintenance, which shifted due to aircraft vibration.