11th of August 1992, Blog #503
With 163 passengers and a crew of 12, a Boeing 767-200ER took off from London Heathrow (England) on a scheduled passenger flight to New York (USA) on this date in 1992. During the take-off, a ground observer noted that the lefthand engine was emitting smoke, similar to the first generation of jet aircraft.
The hole burned into the right-hand engine cowling. (Source & © AAIB, annotated by V2 Aviation)
During the take-off and the initial climb in the flight deck, all indications were normal. As the aircraft climbed through FL180 the engine fire warning for the left engine operated twice for very short periods, while all engine indications were still normal. The captain requested a cabin crew member to take a look at the engine from the cabin and report back. Prior to the return of the cabin crew member, as the aircraft was climbing through FL210, the engine fire warning system for the left engine operated again, this time it remained on and an increase in engine Exhaust Gas Temperature was also observed. The flight crew completed the necessary memory items and shut the engine down, followed by the completion of the required emergency checklist. ATC was informed and a return to London Heathrow was initiated in coördination with ATC. A single-engine landing was completed without further problems. Immediately after landing the fire brigade checked the engine and confirmed that there was no sign of fire. Afterwhich the aircraft was taxied to a parking stand where the passengers disembarked normally.
An investigation by the airline maintenance staff revealed that a hole had been burned into the right-hand side of the N0. 1 (Lefthand) engine cowling. Some small fragments of metallic debris were found in the engine's tailpipe.
Damaged shroud of the 3rd stage Nozzle Guide Vanes (Source & © AAIB)
The engine (a Pratt and Whitney JT9D-7R4D) was replaced and sent to the airline's engine maintenance facility in San Francisco (USA). Here the engine was stripped in the presence of representatives from the operator, Pratt and Whitney, the Federal Aviation Administration (FAA) and the Air Accident Investigation Branch (AAIB). A boroscope inspection of the engine revealed that the compressor was undamaged. The condition of the Low-Pressure turbine was also good. Signs of intense heat were found between the second stage High-Pressure Turbine and the first stage Low-Pressure Turbine. It was also found that a carbon seal between turbine stages had failed. This caused 15th stage compressor air (hot air) to enter the #3 bearing housing. The present oil mist from the lubrication in the bearing housing was ignited by the hot compressor air. Apparently, the fire then progressed into the breather ducting of the oil system. Damage to more seals of the turbine section would have allowed hot gases to enter the gas path of the engine.
FDR data from the incident flight, related to the engines. (Source & © AAIB)
The AAIB report (which was used as reference material for this blog) is available for the readers' reference, by clicking on the .pdf file below;