B738, en-route, southern Austria, 2010
B738, en-route, southern Austria, 2010
Summary
On 9 May 2010, Boeing 737-800 being operated by Swedish operator Viking Airlines on a public transport charter flight from Sharm el Sheikh, Egypt to Manchester UK and which had earlier suffered a malfunction which affected the level of redundancy in the aircraft pressurisation system, experienced a failure of the single air conditioning pack in use when over southern Austria and an emergency descent and en route diversion to Vienna were made. There were no injuries to any of the 196 occupants.
Flight Details
Aircraft
Operator
Type of Flight
Public Transport (Passenger)
Flight Origin
Intended Destination
Actual Destination
Take-off Commenced
Yes
Flight Airborne
Yes
Flight Completed
Yes
Phase of Flight
Cruise
Location
Approx.
near Graz, Austria
General
Tag(s)
Flight Crew Training
EPR
Tag(s)
Emergency Descent,
MAYDAY declaration
AW
System(s)
Air Conditioning and Pressurisation,
Fire Protection
Contributor(s)
Component Fault in service
Outcome
Damage or injury
Yes
Aircraft damage
Minor
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 Technical
Safety Recommendation(s)
Group(s)
None Made
Investigation Type
Type
Independent
Description
On 9 May 2010, Boeing 737-800 being operated by Swedish operator Viking Airlines on a public transport charter flight from Sharm el Sheikh, Egypt to Manchester UK and which had earlier suffered a malfunction which affected the level of redundancy in the aircraft pressurisation system, experienced a failure of the single air conditioning pack in use when over southern Austria and an emergency descent and en route diversion to Vienna were made. There were no injuries to any of the 196 occupants.
Investigation
An Investigation was carried out by the UK AAIB. It was established that the flight was a line training detail for the Captain occupying the left hand seat who had been designated as PF for the flight with the Line Training Captain occupying the co pilots seat.
It was eventually found that a left WING-BODY OVERHEAT annunciation which had occurred at 6500ft in the climb had been false. However, this was not known to the crew who had carried out the applicable Quick Reference Handbook (QRH) drill which required that the left hand air conditioning pack be shut down. Since there were no restrictions on continued flight with just a single pack, it was decided to continue the flight as planned.
Then, approximately 3.5 hours into the flight, in the cruise at FL360, the right air conditioning pack failed and cabin pressurisation was lost. The flight crew donned their oxygen masks, declared a MAYDAY and performed an emergency descent. An uneventful diversion to Vienna followed.
Following a ferry flight unpressurised to a UK maintenance base, a full engine engineering investigation was carried out during which various individually minor faults were found with the air conditioning and pressurisation system. It was concluded that the initial annunciation of an overheat had occurred because of a fault in the related firewire and that the subsequent pack failure which precipitated complete loss of pressurisation had resulted from the sudden failure of a flexible air hose for reasons which it was not possible to determine.
The Final Report of the Investigation was published on 9 September 2010 and may be seen at SKYbrary bookshelf: AAIB Bulletin: 9/2010 EW/C2010/05/01
No Safety Recommendations were made.
