Incident Overview
A multi-engine aircraft experienced a runway excursion during a full stop landing. The pilot applied the brakes to arrest the landing roll, but the aircraft veered slowly to the left without decelerating. The check pilot applied his brakes to assist, but without any effect. The aircraft continued off the runway, where it sustained substantial damage.
Brake System Condition
The aircraft's braking system had been replaced 140 flight hours prior to the occurrence. The aircraft was used extensively for student pilot training. Examination of the brake system revealed excessive wear on the brake linings. The brake lining pucks exceeded their effective limit, which allowed hydraulic fluid bleed-by.
Conclusion
The investigation determined that the brake lining pucks had exceeded their effective limit, leading to hydraulic fluid bleed-by and loss of braking effectiveness.