History of the Flight
On 11 July 2005, a Boeing B767-3YO ER, registration ZS-PBI, was preparing for a scheduled flight from London Gatwick Airport (LGW) to Johannesburg. The aircraft had a gross takeoff mass of 183,981 kg, close to the maximum allowable of 184,612 kg. A reduced Engine Pressure Ratio (EPR) of 1.53 was selected for the takeoff. The takeoff roll on Runway 08R proceeded normally until an indicated airspeed (IAS) of about 150 kt.
At that point, the co-pilot, who was the flying pilot, noticed a 'flash' out of his left eye and heard a bang, followed by the aircraft yawing to the left. He observed the engine gas temperatures (EGTs) were normal and returned his attention to the flight instruments. The commander also felt the yaw and heard a 'dull thump'. He noted that the left engine (No 1) N1 gauge indicated about half full scale deflection and was increasing, with no digital reading. After a second 'thump', the N1 needle dropped well below half scale. Since the IAS was still below V1 (161 kt), the commander called "stop", took control, and executed a rejected takeoff procedure. Reverse thrust and automatic RTO braking were applied. The crew reported the engines behaved correctly during deceleration.
The co-pilot advised ATC of the rejected takeoff and requested the Airport Fire and Rescue Service (AFRS). After slowing to a walking pace, the aircraft exited the runway via taxiway BR and halted on Runway 26R, as instructed by ATC.
AFRS Response
The aircraft stopped in block 42S, approximately 300 metres from the fire station. The AFRS responded very rapidly, with the first appliances arriving within one minute. They informed the flight crew over radio frequency 121.6 MHz of a fire in the left main wheel assembly, which they were engaging. The crew were advised that no evacuation was necessary. After one minute, the AFRS reported extinguishing the left main landing gear fire and requested both engines be shut down. The crew shut down the engines after starting the APU and released the parking brake. The AFRS then engaged a brief fire on the right main wheel assembly.
Two minutes after arrival, the AFRS told the crew the fires were extinguished but brakes were extremely hot. They continued cooling the brakes with a water mist. Twenty-two minutes after the rejected takeoff, passengers disembarked via the forward left door and were bussed to the terminal. A videotape showed fire crews applying mist to the tyres and brakes correctly positioned ahead of and behind the wheels. None of the protective fusible plugs melted. The aircraft was towed to a stand one hour after the rejected takeoff. No injuries were reported.
The AFRS used three major appliances and one light tender, applying 15,000 litres of water as a mist. Firefighters described the larger fire around wheel Nos 2 and 6 (inboard wheels of the left main gear) as "yellow-orange", extinguished "within seconds", briefly extending above the tyre height.
Meteorology
Weather conditions recorded from ATIS prior to takeoff: surface wind 060°/10 kt, visibility >10 km, 1-2 octas cloud at 4,000 ft, temperature 24°C, dew point 10°C, QNH 1031 mb.
Recorded Information
The aircraft was equipped with a Cockpit Voice Recorder (CVR) and Flight Data Recorder (FDR), both successfully downloaded.
CVR
The CVR recorded 30 minutes of audio, but due to extraneous noise, the recording began after the event because the circuit breaker had not been pulled when the engines were shut down. Thus the CVR provided no assistance. The takeoff started at 1950 hrs and both engines were shut down by 1957 hrs, indicating an opportunity to preserve the data in accordance with ICAO Annex 6.
FDR
The FDR covered over 29 hours. Some data anomalies made N1 and computed airspeed unreliable below 5.25% and 30.5 kt respectively; values below these were set to zero. Recording started at 1935 hrs. The left engine consistently ran cooler than the right by about 20°C. After brakes were released at 1942 hrs, the aircraft taxied. At 1950 hrs, it turned onto Runway 08R and accelerated. Approximately 27 seconds after turning, left engine N1 sharply dropped from 100% to just over 70%, then recovered to 97% but N2, EPR, and fuel flow dropped. Over the next four seconds, N1 remained erratic with decreasing N2, EPR, and fuel flow, at which point the thrust levers were retarded and brakes applied. The highest calibrated airspeed recorded was 157.5 kt. No rotation was initiated. After the RTO, engine parameters converged. Braking was briefly relaxed then re-applied with reduced pressure. The autobrake was armed in RTO mode, and no master warnings or cautions were triggered. Oil pressure, temperature, and quantity showed no anomalies, nor did engine fire or bleed overheat warnings. The EEC system parameters appeared normal.
A brake energy chart for the aircraft, considering the high RTO speed, indicated the highest temperatures likely achieved were in the 'brake temperature monitor' range of 8, within the wheel 'Fuse plug melt zone'. The manufacturer's Maintenance Manual warns not to apply coolant to brakes, but the water mist likely removed sufficient heat to prevent fuse plug melting and tyre deflation.
The CVR data loss led to three safety recommendations regarding recorder standards.