What happened
On 5 February 2009, an Avro RJ100, registration G-BZAW, was operating a scheduled passenger service from Glasgow to London City Airport. Following a routine landing on Runway 10, the crew performed a 180-degree turn in the turning circle to vacate the runway. During this maneuver, the flight crew felt a vibration through the nosewheel. As the aircraft back-tracked along the runway, an intermittent judder continued, which the crew initially suspected was caused by a deflating tyre skidding on wet runway markings.
Upon reaching Taxiway C, the aircraft was stopped to allow for a visual inspection of the nose landing gear. This inspection revealed that the left nosewheel was no longer properly attached to the aircraft. The 24 passengers and 5 crew members were disembarked safely, and there were no injuries.
The investigation
The AAIB investigation focused on the mechanical integrity of the nosewheel assembly and the maintenance history of the components. Engineers examined the damaged parts, which included the left nosewheel, its bearings, and the nosewheel axle assembly. The investigation included an analysis of the Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR).
Data from the FDR showed that the landing was within the manufacturer's limits for a hard landing, although the de-rotation rate during the landing was higher than usual. The investigation also reviewed the maintenance records for the wheel, which had been fitted to the aircraft 16 cycles prior during a routine overnight inspection. The engineers performing the installation were found to have followed the required procedures, using a calibrated torque wrench to secure the axle nut.
Findings
Technical examination of the damaged components at the manufacturer's premises determined that the outer bearing of the left nosewheel had failed, subsequently causing the inner bearing, wheel, and axle to sustain damage. The failure was characterized by the roller cage becoming trapped. While the exact trigger for the cage becoming trapped could not be definitively identified, the investigation considered two possibilities: excessive wear in the roller pockets or insufficient pre-load on the bearings.
Analysis of the bearing showed that the failure occurred rapidly, as the rollers still retained much of their original surface finish and had been sufficiently lubricated. The investigation concluded that the landing attitude and descent rate were not the cause of the failure, as the aircraft was operating within normal parameters.