What happened
On 3 August 2003, an Airbus A3/20-200, registration C-FTDF, was landing at Cardiff International Airport following a flight from Tenerife. During the final approach, the crew observed a 'STEERING' warning on the ECAM display. In an attempt to reset the Brake and Steering Control Unit (BSCU), the crew cycled the anti-skid and nosewheel steering switch. While this cleared the warning, it also caused the aircraft to lose its autobrake arming status.
Upon touchdown on Runway 30, the aircraft failed to decelerate as expected. The commander applied the brake pedals with increasing pressure, but there was no effective braking response. The crew subsequently applied maximum reverse thrust and again cycled the steering switch. Eventually, the commander switched the anti-skid and nosewheel steering to the OFF position to access alternate braking via the hydraulic accumulator. While this restored braking pressure, the sudden application of force caused three main landing gear tyres to burst. The aircraft came to a halt approximately 40 metres from the runway end. No injuries were reported among the 162 passengers or 7 crew members.
The investigation
Technical analysis of the flight data recorder (FDR) confirmed that the braking system was ineffective for a significant portion of the landing roll. The investigation established that the initial application of the pedals took between 10 and 13 seconds to reach full deflection. During this period, the aircraft's deceleration was primarily provided by idle reverse thrust and spoilers, which was only slightly higher than the target deceleration rate of the LOW autobrake setting.
Engineers examined the BSCU and, while unable to replicate the exact fault, identified a potential issue with the power supplies for both channels via a 'micro-cut' test. The investigation also noted that the crew's decision to cycle the steering switch on the ground, rather than following the established memory items, added a brief delay to the restoration of braking.
Findings
- The primary cause of the near-overrun was the lack of an effective warning from the Flight Warning Computer regarding the BSCU malfunction, which prevented the crew from immediately recognising the loss of braking.
- The crew's recognition of the braking failure was delayed by several factors, including the end of a long duty day, a desire to maintain passenger comfort, and the lack of a compelling ECAM alert.
- The delay in applying maximum reverse thrust contributed to the increased runway distance required.
- The sudden application of braking pressure, once the switch was turned OFF, led to the rupture of three tyres.
Safety action
- Safety Recommendation 2004-82: Airbus should improve automated warnings to flight crews regarding the loss of braking effectiveness after touchdown or during a rejected takeoff.
- Safety Recommendation 2004-83: Airbus should update Flight Crew Operating Manuals to advise the immediate application of maximum reverse thrust as soon as braking performance is suspected to be inadequate.