Event Details

Title:Air conditioning misconfiguration resulting in cabin depressurization, Ryanair Boeing 737-204 (ADV), EI-CJE
Micro summary:Inadvertent turning off of the packs on this Boeing 737 results in a pressurization crisis.
Event Time:2002-09-28 at 0820 UTC
File Name:2002-09-28-IE.pdf
Publishing Agency:Air Accident Investigation Unit (AAIU)
Publishing Country:Ireland
Report number:2003/010
Site of event:During climb out from Derry Airport
Departure:City of Derry Airport, Derry, Northern Ireland
Destination:London Stansted Airport, Essex, England
Airplane Type(s):Boeing 737-204 ADV
Flight Phase:Climb
Type of flight:Revenue
Serious Injuries:0
Other Injuries:0
Executive Summary:The scheduled passenger flight departed Derry (EGAE) at 08.10 UTC with 108 passengers and 6 crew for Stansted (EGSS). The Captain who was the pilot flying (PF), elected to perform a “Bleeds Off” take-off for which the First Officer (FO), the pilot not flying (PNF), configured the air conditioning panel for “Bleeds Off” at the pre take-off holding point.

After take-off, the PNF reconfigured the air conditioning panel while performing the after take-off checks and turned the air conditioning packs OFF, in error. The flight then continued up to Flight Level (FL) 270, during which both pilots recall hearing warning horns.

At this level the PF levelled the aircraft, passenger oxygen masks had already deployed, and, in a panel scan, he noticed that the packs were selected to OFF and immediately switched them to ON. Cabin pressurisation returned to normal, aural warnings shortly ceased and the flight continued to Stansted, where it landed without further incident. ATC were not made aware of any onboard problem with this flight.

(b) Causes
The initial misconfiguration of the air conditioning and pressurisation system, the non-adherence to SOP’s and the failure of both pilots to monitor the pressurisation system resulted in the aircraft being operated unpressurised up to FL 270, at which level the diagnostic capability of both pilots may have been impaired by the onset of hypoxia. A contributory factor may also have been the Captain’s recollected feeling of fatigue as a result of his poor sleeping pattern over the previous days.
Learning Keywords:Systems - Pneumatics
Systems - Pressurization
Systems - Pressurization - Bleeds-off Pressurization Emergency
Other - Crew Fatigue


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