According to the flight instructor in the multiengine Piper PA-34, he occupied the right seat during the instructional flight. He reported that, during the landing roll, the brakes on his side were inoperative, but the brakes used by the pilot under instruction appeared to function normally.
The flight instructor allowed the pilot under instruction to taxi to parking at the airport in Denton, Texas. During the right turn in the parking area, the pilot under instruction was told to apply both brakes, and the airplane started to “pull left.”
The flight instructor attempted to use differential thrust to arrest the left pull by increasing the right engine speed, but the attempt had no effect.
The flight instructor shut down both engines, however the left wing hit a parked airplane and came to a stop. The airplane sustained substantial damage to the left wing.
The flight instructor reported that the accident could have been prevented if he had stopped on the taxiway and not entered the parking ramp.
A postaccident examination of the brake assembly revealed that the right brake actuator piston “o” ring had failed, which decreased hydraulic brake pressure and prevented proper brake function of the airplane.
Probable cause: The flight instructor’s decision to continue to taxi the airplane to the parking area with a known brake malfunction, which resulted in a loss of directional control and subsequent impact with a parked airplane.
NTSB Identification: GAA17CA093
This December 2016 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.