Emirates B773 near Mumbai on Nov 7th 2012, engine shut down in flight

Last Update: March 14, 2016 / 16:57:24 GMT/Zulu time

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Photo of Emirates Airlines A6-EBO, Boeing 777-300 — Emirates Airlines A6-EBO, Boeing 777-300 (Photo credit: 7mag / Flickr / License: CC by)

Incident Facts

Date of incident
Nov 7, 2012

Classification
Incident

Cause
Engine shut down in flight

Airline
Emirates Airlines

Flight number
EK-373

Departure
Bangkok, Thailand

Destination
Dubai, United Arab Emirates

Aircraft Registration
A6-EBO

Aircraft Type
Boeing 777-300

ICAO Type Designator
B773

An Emirates Airlines Boeing 777-300, registration A6-EBO performing flight EK-373 from Bangkok (Thailand) to Dubai (United Arab Emirates) with 190 passengers and 16 crew, was enroute near Mumbai (India) when the crew received an engine (GE90) fire indication, shut the engine down and activated the fire suppression. The aircraft diverted to Mumbai for a safe landing on runway 09. Responding emergency services found no fire.

A replacement Airbus A330-200 registration A6-EAI positioned from Dubai to Mumbai as flight EK-7372, resumed flight EK-373 and reached Dubai with a delay of 9 hours.

On Mar 14th 2016 India's DGCA released their final report concluding the probable cause of the serious incident was:

Separation of the VBV actuator fuel supply line outside the 'shroud can' to the VBV actuator extend port was caused by high N2 vibrations during flight resulting from damage of HPT.

The DGCA reported that the crew noticed the exhaust gas temperature (EGT) of the right hand engine was 30 degrees C above the left hand engine's EGT while approaching the top of climb, in addition the crew noticed high N2 vibrations of about 4.5 units, all other engine parameters were normal. The crew contacted their maintenance center, which could not offer advice. Later during the flight the crew received an EICAS message indicating the right hand EGT was now 200 degrees C above the left hand engine's EGT, the fuel consumption was 500kg higher than the left hand engine's, and the right hand N2 was 2% above the left hand engine. The crew reduced the engine thrust to decrease the demand, maintenance was again contacted but could not offer advice but to continue, the crew noticed a fuel imbalance was developing and concluded there was a fuel leak. But before the crew was able to start reading the fuel imbalance checklist the crew heard 2-3 bangs from the right hand engine, vibrations, N1 spikes and indications of an engine surge followed by a fire warning for the right hand engine. The captain took control of the aircraft and commanded the engine fire memory items to be worked, the right hand engine was shut down and one fire bottle was discharged into the engine. While working the memory items cabin crew informed the flight crew about sparks being observed from the right hand engine. The crew declared emergency and decided to divert to Mumbai reporting that they had an engine fire, the fire appeared to be out. The crew requested runway 09 (runway 27 was active) prompting ATC to activate the ILS transmitters for runway 09. The aircraft landed safely on runway 09, vacated the runway and stopped for an inspection by emergency services. Emergency services determined that there was no active fire and it was safe to tow the aircraft to the apron, where passengers disembarked normally.

A post flight inspection revealed paint blistering and sooth around the right hand engine's thrust reverser cowls, a fuel leak was observed from the variable bleed valve (VBV) actuator head end fuel line which had sheared throughout 360 degrees at a weld line.

The DGCA analysed the sequence of events were:

During takeoff the N2 vibration began to increase due to high pressure turbine (HPT) distress/damage when stage 1 blades received a mid chord burnout causing deterioration of the HPT.

Reaching the top of climb the engine parameters were stable at 4.4 units of vibrations and EGT about 30 degrees above the left hand engine.

The flight continued for 2.5 hours at FL320 with the crew constantly monitoring the right hand engine parameters.

The status message indicating EGT 200 degrees C above the left hand engine and +500kg of fuel consumption occurred, followed by EICAS messagw that the VBV actuator no longer followed commands, the VBV went fully open causing a further EGT shift by 140 degrees. The fuel consumption further increased.

Stage 1 blades of the high pressure compressor suffered blade tip rubs and liberation of blade tip material as result of the N2 vibrations.

Rubbing occurred between stage 1 HPT blades and nozzles, indications of rubbed induced metal fire occurred. The engine could no longer sustain normal operation with the HPT distress resulting in 3 engine surges. 13 seconds after the first surge the fire warning activated. During the engine stalls the stall front flame went forward of the high pressure compressor and passed through the opened VBV to the VBV cavity and into the under cowl area. Fuel was sprayed from the separated VBV fuel supply line, the stall front flame ignited the air entrained with fuel in the VBV cavity/cowl area, the thrust reverser over pressure doors opened as result of the surge front.

The DGCA analysed that a likely scenario was: "the abnormal operating conditions during the last flight caused twelve consecutive aft inner rails to crack and move aft into the stage 1 HPT blades. This would create the conditions necessary to sustain a nickel-fire. The twelve rails would be of sufficient mass to confine the metal spray of the high speed mechanical rub inboard around the bolt cover causing them to burn then release the mass of molten material onto the leading edge root of the stage 1 HPT blades."