What happened
On 9 July 2002, an Airbus A320-211, registration D-AIPX, was performing a public transport flight that landed on Runway 27L at London Heathrow Airport. Shortly after a standard touchdown, the flight crew noted light vibrations coming from the left side of the aircraft. Within four seconds, the Electronic Centralised Aircraft Monitoring (ECAM) displays alerted the crew with 'GEAR NOT DOWN' and 'SYSTEM DISAGREE' messages.
While the aircraft remained fully controllable, the crew vacated the runway and brought the plane to a halt on a taxiway. The Airfield Fire Service and the operator's maintenance team inspected the aircraft, discovering that a significant portion of the tread had detached from the inboard tyre of the left main landing gear. Although the tyre carcass stayed inflated, the debris had caused damage to the trailing edge flaps and a landing gear sensor. There were no fatalities and no injuries to the 112 passengers or 7 crew members on board.
The investigation
The investigation focused on the Landing Gear Control and Interface Units (LGCIUs) and the physical condition of the tyre. Investigators determined that debris from the flailing tyre had struck a sensor on the left main landing gear strut, triggering the cockpit warnings.
Analysis of the tyre revealed that it had been fitted to the aircraft on 18 June 2002 and had completed 131 landings, significantly less than its expected service life. The tyre had undergone one retread process. Examination of the recovered tread pieces showed no signs of foreign object damage but did reveal evidence of 'working separation' and tear lines. This fatigue process was linked to a section of the spiral belt material.
Findings
- The separation of the tread began due to reduced adhesion levels between the tread and the carcass.
- This lack of adhesion likely caused a slight bulge to develop during service.
- The forces experienced during the wheel spin-up upon landing caused the tread to detach from the carcass.
- A review of the post-retread inspection, which uses shearography (a holographic laser imaging technique), identified an anomaly in the exact region where the separation occurred.
- It is believed the tyre was released for service due to a failure in the non-destructive inspection (NDI) process.