|Title:||Electrical smoke on climb, Boeing 777-236, G-VIIE|
|Micro summary:||This Boeing 777-236 experienced electrical smoke in the cabin on climb.|
|Event Time:||1999-08-08 at 2000 UTC|
|Publishing Agency:||Aircraft Accident Investigation Board (AAIB)|
|Publishing Country:||United Kingdom|
|Diversion Airport:||London Heathrow Airport, London, England|
|Site of event:||En route over Bristol|
|Departure:||London Heathrow Airport, London, England, United Kingdom|
|Airplane Type(s):||Boeing 777-236|
|Type of flight:||Revenue|
|Diverted to:||London Heathrow Airport, London, England|
|Executive Summary:||During the climb after departure from London Heathrow (LHR), whilst passing FL260, a blue/grey haze and acrid fumes were noted in both the flight deck and the passenger cabin. An emergency was declared as a 'PAN' and a return to LHR commenced. The flight crew went onto oxygen immediately and actioned the smoke removal and fuel jettison checklists. A normal autoland was completed, the runway was cleared, and after the fire services confirmed that there were no signs of smoke, the aircraft was taxied to the stand for a normal disembarkation. |
During diagnosis on the ground the engines and their associated air-conditioning packs were run, as well as the Auxiliary Power Unit (APU). The defect was not reproduced. Engine and APU pneumatic ducting were found to be free of signs of oil residue or contamination. However, further inspection of the APU buffer air circuit revealed that its vent tube was blocked.
As a result of several previous experiences of oil contamination resulting from the APU buffer air system, which supplies air pressure to the back of the carbon seal at the rear of the APU load compressor, it was decided to replace the APU as a precaution. The left air-conditioning pack dual heat exchanger was also changed for suspected oil contamination. On completion of this work, engine and APU ground runs were carried out and no odours were noted. The aircraft has re- entered service with re-occurrence of the problem.
The APU was returned to the manufacturer for investigation under warranty.
|Learning Keywords:||Operations - Cabin or Cockpit Smoke|
|Systems - APU|
|Systems - Electrical|
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