Loss of pressurization Incident Airbus A330-302X OH-LTO, Saturday 11 December 2010
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Date:Saturday 11 December 2010
Time:
Type:Silhouette image of generic A333 model; specific model in this crash may look slightly different    
Airbus A330-302X
Owner/operator:Finnair
Registration: OH-LTO
MSN: 1013
Year of manufacture:2009
Fatalities:Fatalities: 0 / Occupants: 3
Other fatalities:0
Aircraft damage: None
Location:300 km NE of Arkhangelsk -   Russia
Phase: En route
Nature:Ferry/positioning
Departure airport:Osaka-Itami International Airport (ITM/RJOO)
Destination airport:Helsinki-Vantaa Airport (HEL/EFHK)
Confidence Rating: Information is only available from news, social media or unofficial sources
Narrative:
The aircraft, registration OH-LTO, was on a scheduled flight from Osaka, Japan to Helsinki-Vantaa airport. Apart from the three crew members in the cockpit, the aircraft was empty.
The aircraft experienced a loss of pressurisation due to dual engine bleed air system failures. The flight crew donned their emergency oxygen masks because of the decrease of cabin pressure.
The flight crew then initiated an emergency descent from cruise level about five minutes after the loss of pressurisation and about two minutes after the excessive cabin altitude warning which is a master warning. OH-LTO diverted to Kuopio, its alternate aerodrome.

This serious incident was caused by malfunctioning of the engines’ bleed regulated pressure transducers' (Pr). The malfunctioning was caused by freezing of water that had accumulated in the bleed regulated pressure transducers' pressure cell rooms, extremely confined by design. This being the case, the transducers provided faulty pressure information to bleed monitoring computers. Due to the erroneous information the computers closed both engines’ bleed air systems which resulted loss of pressurisation in cabin, i.e. an increase in cabin air pressure altitude. The extremely cold air mass enroute during a long time period contributed to the fact that the water froze in the pressure cell rooms. Furthermore, the relatively rapidly increasing ambient temperatures enroute may have contributed to the engine’s bleed air system faults.

Sources:

http://www.turvallisuustutkinta.fi/en/Etusivu/Ajankohtaista/1342536842578

Revision history:

Date/timeContributorUpdates
31-Jul-2012 13:36 harro Added

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