Overview
A flap drive fault experienced by a flight crew after departure from Singapore Changi Airport was caused by the delamination of the number 6 wheel tyre tread during take-off. The incident occurred on runway 20C, where the airport operator subsequently found two debris fields. The delamination likely happened at the southern end of the runway when the tyre was at high speed, providing sufficient energy for the tread to penetrate the left under wing panel and break a flap torque tube.
Tyre Damage and Runway Debris
The tyre manufacturer concluded that the tyre had operated over its life on a grooved runway surface, which generated chevron cutting damage. Prior to the flight, the aircraft tyres were certificated as inspected in accordance with the aircraft manufacturer’s general visual inspection requirements. Although no faults were recorded during the arrival and pre-departure service checks, it was possible that the tyre shoulder was already subject to undercutting of the tread before departure. The arrival inspection likely occurred during daylight hours, but the aircraft may have been parked with the tyre tread positioned such that the initiation site was not visible to the inspector. However, this was not confirmed by the Australian Transport Safety Bureau (ATSB). Additionally, the certification for the pre-departure service check was likely an acknowledgement that the tyre check was not required rather than that it was actually performed.
The northern debris field on runway 20C was likely the result of further tyre delamination on landing, caused by touchdown and wheel acceleration.
Flap Drive System Response
When the flight crew moved the flap selector from the flaps setting of 5 to 1, the left inboard and outboard flaps were unable to move due to the broken torque tube. The right flaps began to move, generating a flap misalignment signal. In response, the flight control electronics cabinets shut down the flap drive system and generated the FLAPS DRIVE fault message. The flight crew then completed the FLAPS DRIVE checklist.
Aircraft Return and Landing
The flight crew were unaware of the tyre damage. However, the aircraft's protective systems and crew actions allowed for a safe return and landing at Singapore Changi Airport, despite the aircraft being overweight and having a higher-than-normal landing speed.