What happened
On 19 August 2003, a Piper PA-34-200T Seneca II, registration G-BEAG, was conducting a training flight at Oxford (Kidlington) Airport. The purpose of the flight was to familiarise a student pilot with the aircraft type. During the takeoff roll on Runway 1s, the aircraft initially accelerated normally. However, upon reaching 60 kt, the aircraft began to yaw to the right, accompanied by a noticeable reduction in acceleration and an unusual noise from the right side.
The commander, perceiving a potential power loss and noting the diminishing runway remaining, elected to abort the takeoff. Despite applying the toe brakes, the aircraft failed to decelerate effectively. In an effort to avoid a boundary hedge, the commander utilised left differential braking to steer the aircraft. The aircraft subsequently departed the runway and struck the hedge at approximately 30 kt. The impact caused significant damage, including a ruptured right fuel tank, a crushed nose cone, and the collapse of the left main landing gear. Both occupants were uninjured during the event.
The investigation
Investigators examined the aircraft's braking system and engines following the accident. While the engines showed no pre-existing defects, the braking system exhibited signs of extreme heat. The left brake unit had overheated to the point that the brake pads had welded to the disc, and a fire had ignited around the left main landing gear. The right brake also showed evidence of overheating due to dragging pads.
Further inspection of the brake master cylinder revealed that the parking brake lever resisted full movement upon release, though cleaning and resealing the system restored its functionality. The investigation also noted that during a flight on the preceding day, the pilot had reported the wheels 'skipping' during the takeoff roll, suggesting a recurring issue with the brakes.
Findings
- The primary cause of the runway excursion was the failure of the brakes to provide effective deceleration.
- Evidence indicates that dragging brakes likely caused both the loss of acceleration during the takeoff roll and the subsequent inability to stop the aircraft.
- The overheating of the left brake unit, resulting in a fire, was consistent with the heavy application of differential braking used to avoid the hedge.
- While a specific mechanical defect in the braking system could not be definitively identified, the resistance in the brake master cylinder suggested that the brakes may not have been fully released after the parking brake was disengaged.