Incident
On 18 May 2005 at 1143 hrs UTC, an Airbus A320-211, registration JY-JAR, operated by Jordan Aviation, was landing on Runway 14 at Leeds Bradford International Airport. The aircraft touched down just beyond the end of the marked touchdown zone with low autobrake selected. Manual wheel braking commenced shortly after mainwheel touchdown. At a groundspeed of around 70 kt, the brakes ceased operating for approximately 17 seconds. A pronounced dip in the runway surface prevented the pilots from seeing the runway end until late in the ground roll.
When it became apparent to the commander that the aircraft could not stop before the end of the runway, he deliberately did not select alternate braking to avoid loss of nosewheel steering. Instead, he used nosewheel steering to turn the aircraft sharply to the right. The aircraft skidded sideways and came to a halt with its nosewheels off the runway, shortly before the end of the paved surface and the start of a steep down slope. Damage was limited to slight distortion of the nose landing gear caused by overload while running on the grass.
Investigation
The Air Accidents Investigation Branch (AAIB) conducted the investigation. The flight crew were properly licensed and rested. Neither pilot had landed at Leeds Bradford before, and they were unfamiliar with the line-of-sight characteristics of Runway 14. The aircraft was below maximum landing weight and its centre of gravity was within limits. The speed over the landing threshold was consistent with scheduled performance.
The Normal braking system malfunctioned at around 70 kt groundspeed, causing loss of almost all braking effect. Automatic reversion to Alternate braking did not occur. There was no flight deck warning of the brake malfunction, which likely delayed the crew's recognition of the loss. The Flight Crew Operating Manual (FCOM) procedure for loss of braking was not completed. Analysis showed that if the commander had followed the remaining actions after selecting max reverse thrust, the aircraft could have stopped on the paved surface using at least 252 m of the remaining 280 m, but the commander could not have known this.
Cause
The cause of the braking loss could not be positively established but was consistent with excessive noise in electrical signals from the mainwheel tachometers used to sense groundspeed. Two tachometer driveshafts were found bent, which probably encouraged a resonant condition causing signal errors above the monitored speed range. Should the condition affect both main landing gears simultaneously, the brake control system logic could generate an erroneous aircraft reference speed, activating the anti-skid system and releasing the brakes. Fluctuation in the signal errors prevented detection and correction or crew warning.
Additionally, a number of other known anomalies with the brake control and monitoring system were identified, some of which had resulted in previous incidents and accidents. The aircraft manufacturer had defined corrective actions, including redesigned tachometer driveshafts and updated software, but these had not been incorporated on a substantial number of aircraft, including JY-JAR. The investigation raised concerns about procedures for design quality and continued airworthiness. Seven Safety Recommendations were made, addressing tachometer driveshaft replacement, software updates, runway marking, and flight crew warnings.