Loss of pressurization Serious incident Boeing 737-8Q8 HA-LOK,
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ASN Wikibase Occurrence # 187953
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Date:Wednesday 23 November 2011
Type:Silhouette image of generic B738 model; specific model in this crash may look slightly different    
Boeing 737-8Q8
Owner/operator:Malev Hungarian Airlines
Registration: HA-LOK
MSN: 30669/1479
Year of manufacture:2004
Fatalities:Fatalities: 0 / Occupants: 76
Aircraft damage: None
Category:Serious incident
Location:Budapest (LHCC) FIR -   Hungary
Phase: En route
Nature:Passenger - Scheduled
Departure airport:Budapest Ferenc Liszt International Airport (BUD/LHBP)
Destination airport:Moskva-Sheremetyevo Airport (SVO/UUEE)
Investigating agency: TSB Hungary
Confidence Rating: Information verified through data from accident investigation authorities
Flight MA102 to Moscow departed from Budapest, Hungary.
Having started the engine in Budapest, the flight crew failed to turn on the “Pack” switches of the air conditioning system, thus air was not vented into the cockpit and into the cabin.
During the climb after takeoff, approaching FL150, the cabin altitude horn went off as a result of excessive decrease in cabin pressure (reaching cabin altitude of 10 000 feet). In spite of this, the crew did neither turn on air conditioning nor carried out an emergency descent, thus the cabin altitude kept on decreasing. Triggered by that, passing 14 000 feet cabin altitude, the oxygen masks were automatically deployed in the cabin. The crew turned around the aircraft and landed back at Budapest. There were no personal injuries, but during the turn around, descent, approach and landing, the crew committed several mistakes which might have been provoked by the prior oxygen deficient period.

Causes of the incident
The technical investigation of the IC concluded that the incident happened due to the following provable reasons:
– After engine start, the crew failed to turn the “Pack” switches of the air conditioning system from the “OFF” position to the “AUTO” position.
– The failure to turn on air conditioning was also not recognized while reading out the checklists.
– When the horn indicating dangerously low cabin pressure went off, the crew did not recognize and eliminate the cause of pressure loss.
– The checklist applicable in case of the horn indicating dangerously low cabin pressure going off, does not include checking the air conditioning switches, and turning them on, if necessary.
– In spite of not having been able to eliminate the cause of the loss in pressure in the 3 minutes after the sound warning, the crew did not follow the procedure laid down in the emergency checklist applicable in case of the sound warning going off.
– The Final Report investigating the serious aviation incident of some years ago established that the activities of the crew led by the same commander swerved at several points from the relevant specifications.
– Following the earlier serious aviation incident, the commander did not undergo an unscheduled medical examination, thus his possible medical inadequacies which might have contributed to the occurrence may have remained hidden.

Accident investigation:
Investigating agency: TSB Hungary
Report number: 
Status: Investigation completed
Download report: Final report


TSB Hungary

Revision history:

07-Jun-2016 16:11 harro Added

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