What happened
On April 19, 2011, an ATR 72-200, registration EI-REJ, operated by Air Contractors, landed at Paris Charles de Gaulle airport following an international cargo flight from Cork, Ireland. After vacating runway 09 L via taxiway Z5, the crew was instructed to proceed via taxiway K6.
During the taxi, the crew noticed that significantly more engine power was required to maintain taxi speed, though they initially decided to continue the taxi and investigate the issue later. Shortly after, a "BRK TEMP HOT" alarm activated on the flight deck. The commander noted that the parking brake had not been applied. As the aircraft continued toward taxiway B, the pilot observed an unusual tilt in the left wing. At approximately 21:50 UTC, the crew decided to stop the aircraft. The presence of fire was actually first reported to air traffic control by the crew of a following aircraft. Following the decision to shut down the engines and cut electrical power, the crew evacuated the aircraft, and airport fire services extinguished the fire.
The investigation
The investigation focused on the braking system and the cause of the thermal event. The aircraft's left main gear sustained heavy damage from the fire, necessitating the replacement of both brake units and associated fairings. Technical examination revealed that the external brake unit (number 1) was more severely damaged than the internal unit (number 2).
Investigators found that the wear on the number 1 brake unit had exceeded the manufacturer's limits. However, the "spreader plate" used to monitor brake wear was deformed, which masked the true level of wear during routine maintenance inspections, making the component appear within limits. Furthermore, the aircraft lacked a dedicated fire detection sensor near the main landing gear, meaning the crew only became aware of the fire through the observations of another pilot.
Findings
- The fire was likely caused by a piston seizure within the brake unit, which created enough friction to raise temperatures significantly.
- A hydraulic leak, which may have been pre-existing or caused by the heat, allowed hydraulic fluid to spray onto hot components, triggering the fire.
- The excessive wear on the brake unit could not be detected during daily maintenance because a deformed spreader plate prevented an accurate reading of the indicator pin.
- There was no established procedure from the manufacturer or operator for handling a brake temperature alarm specifically during the taxi phase.
- The aircraft's systems were unable to alert the crew to the fire internally due to the absence of sensors in the landing gear area.