On April 16, 1984, a Swearingen SA226TC (registration N163MA) operated by Midstate Airlines, Inc. was involved in an aviation accident near Milwaukee, WI. Investigators recorded the probable cause as: the binding of the right main gear door due to a slightly bent aft hinge bolt and a dry, unlubricated bushing, which the hydraulic cylinder could not overcome; the lack of recent inspection and lubrication was attributed to the difficult access of the bushing. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 2 related events involving the same aircraft type or operator are linked below.
A gear-up landing occurred when the crew could not extend the right main landing gear. Examination revealed a bent hinge bolt and dry bushing that had not been recently lubricated due to difficult access.
Incident Overview
A gear-up landing was performed after the flight crew was unable to extend the right main landing gear through normal and emergency procedures. The aircraft touched down with the landing gear retracted.
Examination Findings
A post-incident examination of the aircraft disclosed that the right main landing gear door aft hinge bolt was slightly bent and difficult to rotate in its bushing. The bushing and bolt were dry and had not been lubricated recently. The hydraulic cylinder was not capable of supplying enough pressure to overcome the binding door.
Maintenance Context
Investigators determined that the bushing had not recently been inspected or lubricated by maintenance personnel because of its location being difficult to access.
Probable cause
the binding of the right main gear door due to a slightly bent aft hinge bolt and a dry, unlubricated bushing, which the hydraulic cylinder could not overcome; the lack of recent inspection and lubrication was attributed to the difficult access of the bushing.