On April 11, 2007, a Cessna 170A (registration N1258D) was involved in an aviation accident near Watkins, CO. Investigators recorded the probable cause as: The uneven brake shoe wear caused the caliper pins to engage misaligned, contacting the rotor, locking and shearing the caliper assembly (as surmised by the FAA airworthiness inspector). This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A pilot practicing touch-and-go landings experienced a swerve on final landing. The right wing struck the ground, bending the spar, and the airplane departed the runway. FAA inspection revealed severely worn brake shoes with uneven wear.
Accident Details
The pilot had been practicing touch-and-go landings. During the final landing, the airplane swerved to the right. The right wing struck the ground, bending the spar. The airplane then departed the runway.
Examination Findings
An FAA airworthiness inspector examined the airplane following the incident. The inspector noted that the right brake caliper assembly had severely worn shoes with uneven wear. The inspector surmised that the uneven brake shoe wear caused the caliper pins to engage misaligned. This misalignment resulted in the pins contacting the rotor, which led to locking and shearing of the caliper assembly. No other factors were identified in the source material.
Probable cause
The uneven brake shoe wear caused the caliper pins to engage misaligned, contacting the rotor, locking and shearing the caliper assembly (as surmised by the FAA airworthiness inspector).