Piper PA 34 N2844T accident near Denton, Texas

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 analysis

According to the flight instructor in the multiengine airplane, he occupied the right seat during the instructional flight. The flight instructor 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. 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 struck 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.

Text from the NTSB. Open the NTSB docket for GAA17CA093 for the full record.