B742, en-route, Mount Galunggung Indonesia, 1982

Summary: 

On 24 June 1982, a British Airways Boeing 747-200 lost power on all four engines while flying at night at FL370 en route from Kuala Lumpur to Perth. During the ensuing sixteen minutes, the aircraft descended without power from FL370 to FL120, at which point the flight crew were able to successfully restart engines one, two and four after which an en route diversion was made to Jakarta.

Event Details
When: 
24/06/1982
Event Type: 
Day/Night: 
Night
Flight Conditions: 
IMC

18907

Flight Details
Aircraft: 
Operator: 
Type of Flight: 
Public Transport (Passenger)
Intended Destination: 
Take-off Commenced: 
Yes
Flight Airborne: 
Yes
Flight Completed: 
Yes
Phase of Flight: 
Cruise
Location
Approx.: 
near Mount Galunggung, Indonesia
LOC
Tag(s): 
Loss of Engine Power
WX
Tag(s): 
Volcanic Ash Effects
Outcome
Damage or injury: 
Yes
Aircraft damage: 
Major
Non-aircraft damage: 
Yes
Non-occupant Casualties: 
No
Occupant Injuries: 
None
Occupant Fatalities: 
None
Off Airport Landing: 
Yes
Ditching: 
Yes
Causal Factor Group(s)
Group(s): 
Aircraft Operation
Safety Recommendation(s)
Group(s): 
Aircraft Operation
Investigation Type
Type: 
Independent

Description

On 24 June 1982, a British Airways Boeing 747-200 lost power on all four engines while flying at night at FL370 en route from Kuala Lumpur to Perth. During the ensuing sixteen minutes, the aircraft descended without power from FL370 to FL120, at which point the flight crew were able to successfully restart engines one, two and four after which an en route diversion was made to Jakarta.

Investigation

On-site inspection of the airframe and engines found a generally “sand-blasted” appearance to the leading edges of the wing, the externally visible air intake surfaces, the radome and the cockpit windows. Boroscope inspection of the engines did not disclose any mechanical damage or any evidence of a fuel flow problem but did show heavy deposits of an unknown material on the concave surfaces of the high pressure turbine blades and the associated guide vanes.

The flight crew reported that an “acrid electrical” smell had become apparent in the flight deck shortly before the engine malfunctions accompanied by what appeared to be very fine dust or smoke coming from the air conditioning system. St. Elmo’s fire had been observed on the leading edge of the engine nacelles and around the flight deck windows and a “search light” effect had been visible shining from within the engines through the fan blades. When preparing for the diversion landing, it had become apparent that the flight deck windows had become almost completely opaque and the landing had to be completed by the handling pilot looking through a small side section of the flight deck window that had remained relatively clear.

Since a large Indonesian volcano in the vicinity of the flight path, Mt. Galunggung, had been erupting explosively at the time of the incident, it was quickly established than penetration of the dense ash plume from this eruption was likely to have been the cause.

Subsequent strip-down inspection of the engines found general evidence of “sand-blasting”, erosion of compressor rotor paths and rotor blade tips, erosion of the leading edges of high-pressure rotor blades and fused volcanic debris on the high pressure nozzle guide vanes and turbine blades. It was concluded that the engines on the aircraft had all stalled following the ingestion of a significant quantity of volcanic ash and that a restart had only been achieved because the aircraft, in descending without power, emerged from ash cloud into clear air with sufficient terrain clearance.

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