On January 18, 1986, a Boeing A75N1 (registration N4935N) was involved in an aviation accident near Yukon, OK. Investigators recorded the probable cause as: The breaking of the left brake shoe return spring, which caused the left brake to lock during the landing roll and resulted in the aircraft flipping inverted. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
Aircraft flipped inverted after the left brake locked during landing roll due to a broken return spring, bringing the plane to a stop.
What happened
The aircraft experienced a mechanical issue shortly after touchdown. As the plane rolled along the runway, the left brake became locked. This sudden resistance caused the aircraft to slow down rapidly until it reached a forward speed of approximately 20 mph. The uneven braking force then caused the aircraft to flip onto its back, coming to a complete stop in an inverted position.
The investigation
A post-accident examination was conducted to determine the cause of the incident. Investigators found that the brake shoe return spring on the left brake assembly was broken. This failure prevented the brake from releasing properly, leading to the lock-up during the landing roll. The specific reason for the spring's failure could not be determined from the available evidence.
Probable cause
The breaking of the left brake shoe return spring, which caused the left brake to lock during the landing roll and resulted in the aircraft flipping inverted.