What aircraft was involved and where did it happen?

The accident on 2005-07-11 involved a Boeing B767-3YO ER, registration ZS-PBI, at London Gatwick Airport, GB.

What was the probable cause of the accident?

The primary cause of the rejected takeoff was an intermittent, erroneous signal from the low-pressure rotor (N1) sensor on the number one engine, which led to erratic engine performance readings.

Engine Signal Fault Triggers Rejected Takeoff on Boeing 767

A Boeing 767-300ER operating a scheduled flight to Johannesburg experienced an engine anomaly during takeoff at London Gatwick, leading to a rejected takeoff and brief landing gear fires.

What happened

On 11 July 2005, a Boeing 767-300ER, registration ZS-PBI, was performing a scheduled passenger flight from London Gatwick Airport to Johannesburg. The aircraft was departing Runway 08R at a gross takeoff mass near its maximum allowable limit.

As the aircraft accelerated toward its decision speed (V1), the flight crew detected an issue with the number one engine. The co-pilot observed a visual flash and heard a loud bang, accompanied by a leftward yaw. Simultaneously, the commander noted erratic behavior on the N1 gauge, which showed a significant drop in speed followed by an unstable reading. Because the aircraft was still below V1, the commander initiated a rejected takeoff.

During the high-energy deceleration, the aircraft' and the crew experienced intense braking. The airport fire service arrived quickly and identified small fires involving the left and right main landing gear wheel assemblies. The crew and 207 passengers were not injured, and the passengers were safely evacuated via bus to the terminal after the aircraft was secured.

The investigation

The AAIB examined the aircraft and the engines. The number one engine was subsequently sent to Singapore for a detailed examination. Investigators also reviewed flight data recorder (FDR) and cockpit voice recorder (CVR) data, though the CVR data was limited as it had been overwritten before it could be isolated.

Engine inspections revealed no physical damage or permanent anomalies within the engine itself. However, the data suggested the performance fluctuations were caused by an intermittent error in the low-pressure rotor speed (N1) signal. Regarding the landing gear, investigators found that the application of water mist by the fire service prevented the wheel fusible plugs from melting, despite the intense heat generated by the braking action.

Findings

The rejected takeoff was prompted by an erroneous N1 signal from the left engine, which caused unstable engine parameters.
The brief fires on the main landing gear were contained and did not cause structural damage to the wheels or brakes.
The aircraft's high takeoff mass contributed to the high energy levels during the rejected takeoff.
The loss of critical CVR audio was due to the failure to pull the circuit breaker to preserve the data immediately following the event.