What happened
On 19 May 2023, an Etihad Airways Boeing 777-300ER, registration A6-ETP, arrived at Abu Dhabi International Airport from Sydney, Australia. Following a routine landing on runway 13R, the aircraft proceeded to taxi toward its parking stand. During the taxi process, the flight crew implemented a single-engine taxi procedure by shutting down the right engine.
While maneuvering on taxiway Foxtrot, the crew observed flames emerging from the left main landing gear via the ground maneuver camera system. Although the flames self-extinguished quickly, smoke continued to emanable from the area. The crew immediately halted the aircraft, declared a MAYDAY, and requested emergency assistance from airport firefighting services.
Airport responders arrived shortly after, noting smoke and hydraulic fluid leakage. To mitigate the risk, the fire commander instructed the crew to shut down the left engine. Ground operations teams also discovered metal and carbon fiber fragments on both the taxiway and the runway centerline, leading to a temporary suspension of operations on runway 13R. The aircraft was eventually towed to a parking stand, where passengers and crew disembarked without injury.
The investigation
An investigation by the UAE Air Accident Investigation Sector (AAIS) focused on the mechanical failure of the braking system. Investigators examined the aircraft's maintenance history, flight data, and the physical condition of the landing gear. The inspection revealed that brake assembly number 2 had suffered significant damage, specifically a leak from one of the pistons and damage to the axle sleeve due to overheating.
Findings
- The fire was caused by the failure of the brake stators, which led to the shearing of pressure plate lugs.
- This mechanical failure allowed the pressure plate to rotate freely, which subsequently damaged a piston.
- The damaged piston released hydraulic fluid into the heat sink; the fluid reached its flashpoint due to heat, creating the brief flame and subsequent smoke.
- While routine transit and exterior inspections could have identified brake wear or leaks, the specific failure of the internal stators was not visible from the outside of the wheel assembly.
- The investigation could not definitively determine the original cause of the initial stator lug damage.