What happened
On 13 December 2006, a DHC-8-311, registration G-WOWD, was performing a commercial passenger flight departing from St Mawgan, Cornwall. Shortly after takeoff, air traffic controllers notified the flight crew that a main wheel had fallen from the aircraft. The crew reported that the takeoff had felt normal and that no unusual vibrations or noises had been detected by the flight or cabin crew.
Following the notification, the crew contacted their operating company for guidance and prepared the cabin for an emergency landing. The aircraft returned to St Mawgan and landed without further incident. The aircraft came to a stop on the taxiway, where passengers were evacuated as a precaution before the aircraft was towed to a stand.
The investigation
Investigators recovered the missing wheel, along with pieces of the retaining nut and wheel bearing, from the runway. An examination of the aircraft's landing gear revealed damage to the main wheel stub axle, but the rest of the gear remained intact.
Technical analysis of the recovered components showed that the retaining nut had failed due to extreme loads on its inner face. While fragments of the bearing cage and one roller were found, the severity of the secondary damage made it impossible to determine the specific initial failure mode of the bearing. Maintenance records indicated that the wheel assembly had been serviced and re-greased following a tyre replacement less than a month prior, with no defects noted during that process.
Findings
- The loss of the main wheel was caused by a failure of the wheel bearing.
- The aircraft manufacturer noted that several similar wheel loss events had occurred due to bearing failures.
- Potential contributing factors for such failures include inadequate grease levels, incorrect installation, or the accumulation of brake dust.
- The manufacturer has since implemented measures to enhance bearing durability, including the approval of new greases and recommendations for bearing replacement during every wheel change under harsh conditions.