What happened
On 2 March 2001, an Embra and EMB-145, registration G-EMBP, was performing a scheduled public transport flight from Paris to Edinburgh. Upon landing on Runway 24, the crew heard an audible high-speed noise, which the commander initially suspected might be a tyre burst. While the aircraft was stationary on the runway, an airport fire service inspection noted that the left nose wheel appeared under-inflated.
During a subsequent attempt to taxi the aircraft forward to allow an engineer to inspect the wheel, a loud bang occurred, and the left nose wheel detached from the aircraft. The passengers and crew were able to deplane safely without injury, though the incident caused a significant disruption, resulting in the closure of the runway for approximately one hour.
The investigation
The AAIB investigation focused on the structural failure of the nose landing gear (NLG) axle. Metallurgical analysis revealed that the axle had suffered a complete fracture due to severe overheating, with temperatures in the affected area estimated to have exceeded 800°C. This heat had caused the paint to blister and the metal to become brittle.
Examination of the wheel bearings showed that the left inner bearing (Bearing 2) had reached a state of extreme distress, with the inner race having seized onto the axle. The investigation also scrutinized the maintenance history and the installation of the wheel components. It was discovered that the bearing assembly had been fitted with incorrect, overlapping seals. Specifically, double seals had been installed on the thrust side of several bearings, which included both the older Type A seals and the newer Type C integrated seals.
Findings
- The nose landing gear axle fractured because of extreme overheating caused by the failure of the left inner wheel bearing.
- The bearing failure was driven by the incorrect installation of multiple seals, which created abnormal loads and likely allowed dirt and water to contaminate the bearing grease.
- The presence of grit and dry, powdery grease around the bearing indicated a loss of lubrication and effective sealing.
- Ambiguity in maintenance documentation and part numbering likely contributed to the confusion regarding which seal and water deflector configurations were appropriate for use.