What happened
On December 18, 2012, a Boeing 787-8 operated by PLL LOT SA experienced a malfunction of its braking system following a flight at Warsaw Chopin Airport (EPWA). After the aircraft had landed, the flight crew noted an error within the braking system. Subsequent maintenance inspections revealed significant mechanical damage to the electric brake actuator (EBA) of brake assembly number 3. Specifically, the rear cover of the piston had been torn off, the mounting bolts were sheared, and the piston stem had been crushed, with debris found inside the actuator unit.
Additionally, the inspection of the landing gear revealed minor mechanical damage to the surface of the landing gear bogie. This damage was attributed to the movement of the malfunctioning component.
The investigation
The investigation, conducted by the operator, focused on the mechanical integrity of the braking assembly and the landing gear structure. The examination established that the damage to the bogie surface was likely caused by the uncontrolled movement of the third electric brake actuator. The investigation also identified the specific internal destruction within the actuator, including the failure of the piston stem and the loss of mounting hardware.
Findings
- The primary cause of the incident was the uncontrolled operation of the EBA number 3 actuator.
- The movement of the actuator resulted in physical contact with the landing gear bogie, leading to secondary mechanical damage to the bogie surface.
- The EBA number 3 unit suffered severe internal mechanical failure, including the destruction of the piston stem and the loss of mounting bolts.