What happened
On 29 May 2008, an Airbus A3/330-323X, registration N270AY, was preparing for a commercial passenger flight from Manchester to Philadelphia. During the takeoff roll, the crew observed an ECAM caution indicating an engine pressure ratio (EPR) mode fault on the number one engine. After an initial attempt to continue the takeoff by selecting maximum thrust, the commander decided to reject the takeoff. The aircraft decelerated from a groundspeed of approximately 130 kt, reaching taxi speed before exiting the runway.
Following the high-energy braking event, the crew noted extremely high brake temperatures and a loss of hydraulic fluid from the Green system. While taxiing toward a parking area, the crew observed a tyre deflation. The aircraft eventually came to a stop near an engine test bay, where the Airfield Fire and Rescue Service attended. There were no fatalities and no injuries among the 12 crew members or 250 passengers on board.
The investigation
The AAIB investigation focused on the mechanical failures that occurred during the deceleration phase. Investigators examined the aircraft's flight data recorder and cockpit voice recorder, which confirmed the sequence of engine thrust fluctuations and the crew's decision-making process.
Physical examination of the landing gear revealed that the brake unit on the number five wheel had disconnected from its brake reaction rod. This detachment was caused by the failure of the attaching torque pin. The resulting rotation of the brake unit damaged hydraulic lines and electrical harnesses, leading to the loss of Green system hydraulic fluid and the deflation of a tyre. Additionally, investigators found debris on the runway, including fragments of the brake pin flange and parts of the brake rod assembly.
Findings
- The primary cause of the engine thrust issue was the failure of a sensing tube supplying pressure to the FADEC, which resulted from fatigue due to thermal expansion differences.
- The rejected takeoff was a high-energy event that placed extreme stress on the braking system.
- The torque pin failure was the critical factor in the landing gear damage; the pin had been previously weakened by an unidentified earlier event, causing the flange to fracture under the heavy braking loads of the RTO.
- The disintegration of two brake stator discs occurred due to the high torque associated with the maximum autobrake setting and the worn condition of the discs.
- The loss of hydraulic fluid was exacerbated by the rupture of brake hoses, which the hydraulic fuse failed to contain.