What happened
On 12 January 2021, a SOCATA TB-10, registration EC-FTJ, was performing a solo instructional flight at Salamanca Airport, Spain. After completing a routine training flight under visual flight rules, the student pilot landed on runway 03 and followed air traffic control instructions to perform a U-turn and exit via taxiway C5.
While stationary at the taxiway C5 holding point, the pilot was alerted via radio by another aircraft that his plane was on fire. The fire had originated in the left main landing gear leg. Shortly after the pilot realized the situation, the aircraft's brakes suddenly failed, causing the aircraft to begin an uncontrolled forward movement along the taxiway. Following emergency instructions to shut down the engine and electrical systems, the pilot observed black smoke entering the cockpit and subsequently abandoned the aircraft while it was still in motion. The aircraft eventually came to a stop at the end of the taxiway, and the fire was extinguished by the airport fire brigade. The pilot was unharmed, but the aircraft sustained significant damage to the left main landing gear, tire, brake, and various sections of the wing and fuselage skin.
The investigation
The CIAIAC examined the aircraft's braking system and maintenance history. The investigation focused on the mechanical state of the left brake calliper and its interaction with the landing gear leg. Investigators analyzed the condition of the anchor bolts and the torque plate bushings to determine if a mechanical seizure or drag had contributed to the overheating and subsequent fire.
Findings
- There was a significant transfer of heat between the brake pads and the brake disc, leading to high temperatures.
- The left brake calliper anchor bolts were not parallel, which compromised their ability to slide through the torque plate bushings.
- Material loss, including grooves and corrosion, was found on the inner surfaces of the torque plate bushings, which prevented the anchor bolts from sliding freely.
- The aircraft manufacturer's maintenance instructions did not require checking if the brake calliper slides smoothly through the bushings, although the brake manufacturer's instructions did include this check.
- The investigation was unable to determine the definitive cause of the accident.