Event Details

Title:Decompression at altitude, Boeing 757-236, G-BIKL
Micro summary:This Boeing 757-236 experienced a decompression at altitude.
Event Time:1999-05-22 at 1245 UTC
File Name:1999-05-22-UK.pdf
Publishing Agency:Aircraft Accident Investigation Board (AAIB)
Publishing Country:United Kingdom
Report number:EW/A99/5/1
Site of event:Cruise between Stockholm and London
Departure:Stockholm-Arlanda Airport, Marsta, Sweden
Destination:London Heathrow Airport, London, England
Airplane Type(s):Boeing 757-236
Flight Phase:Cruise
Operator(s):British Airways
Type of flight:Revenue
Serious Injuries:0
Other Injuries:0
Executive Summary:A new crew had taken over the aircraft for the flight from Stockholm to London Heathrow. The only unserviceability was that the right air conditioning pack had been inoperative for the last two sectors that day. In accordance with the Dispatch Deviation Manual (DDM), G-BIKL had been cleared to continue the series of flights but not to exceed three flight days before completion of repairs; the crew were required to confirm that high flow was operating normally on the remaining pack and were to limit altitude to FL 350 or below.

Following a normal take off and climb, the commander, as handling pilot, established the aircraft in the cruise at FL310. Then, between 'AMRAN' and 'DANDI' reporting points, the 'L ENG BLEED OFF' message illuminated on the Engine Instrument Crew Alert System (EICAS) and the associated light went off. The commander checked the pressurisation and noted that the cabin altitude was climbing at approximately 2,000 feet/min. He instructed the first officer to ask Copenhagen ATC for an immediate descent and the aircraft was immediately cleared to FL250. As they descended, the controller asked if they would require a further descent and the crew declared a 'PAN', requesting descent to FL100 and a diversion to Hamburg. During the descent, the commander gave the handling duties to the first officer and he then reviewed the non-normal checklist for 'Engine Bleed Off' in the Quick Reference Handbook. The final action in the checklist is for the 'Isolation Switch' to be selected 'On'. When this was selected, the pressurisation began to recover to normal. The crew recalled that this occurred at approximately FL140 and that the maximum displayed cabin altitude was 9,000 feet. By now, the aircraft was under the control of Bremen ATC and the crew cancelled the 'PAN' call but stated that they would continue with the diversion into Hamburg.

The commander briefed the cabin staff and the passengers and continued with the diversion into Hamburg, asking for priority when ATC advised that aircraft were being held prior to approach. An uneventful approach and landing was made at Hamburg.
Learning Keywords:Systems - Pneumatics
Systems - Pneumatics - Air Conditioning Packs
Systems - Pressurization


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