<< >> NASA ASRS Report 224717, October 1992

Widebody transport descends from 33000 ft to 10000 ft because of a cabin pressurization problem. Crew solved problem and proceeded to destination.

Attributes
ACN	224717
Time
Date	199210
Day	Tue
Place
Locale Reference	atc facility : las
State Reference	NV
Altitude	msl bound lower : 10000 msl bound upper : 33000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zab
Operator	common carrier : air carrier
Make Model Name	Widebody, Low Wing, 3 Turbojet Eng
Navigation In Use	Other
Flight Phase	cruise other descent other other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : flight engineer pilot : instrument pilot : private pilot : cfi pilot : commercial
Experience	flight time last 90 days : 200 flight time total : 5000 flight time type : 200
ASRS Report	224717
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : overcame equipment problem flight crew : declared emergency
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Cabin pressure exceeded 10500 ft after level off. Descended to 10000 ft MSL. Regained controller and pressurization. Elected to continue to destination (jfk). Pressure normal for remainder of flight. Contributing factor, insidious loss of pressure. Discovered when warning horn and warning light alerted crew. I was given/assigned the job of flying the plane and coordinating with ATC for possible air interrupt to las. I did not participate in the checklist abnormal procedures of determining the problem and corrections. Callback conversation with reporter revealed the following: reporter explained that they had climbed to and were level at 33000 ft before the cabin climbed to 10000 ft. He is sure the problem was mechanical. They orbited east of las until they cleared up the problem. They were then reclred to jfk. Their alternate had to be removed due to the fuel they burned while solving this problem. Reporter insists he does not know what caused it.

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Original NASA ASRS Text

Title: WDB DSNDS FROM 33000 FT TO 10000 FT BECAUSE OF A CABIN PRESSURIZATION PROBLEM. CREW SOLVED PROBLEM AND PROCEEDED TO DEST.

Narrative: CABIN PRESSURE EXCEEDED 10500 FT AFTER LEVEL OFF. DSNDED TO 10000 FT MSL. REGAINED CTLR AND PRESSURIZATION. ELECTED TO CONTINUE TO DEST (JFK). PRESSURE NORMAL FOR REMAINDER OF FLT. CONTRIBUTING FACTOR, INSIDIOUS LOSS OF PRESSURE. DISCOVERED WHEN WARNING HORN AND WARNING LIGHT ALERTED CREW. I WAS GIVEN/ASSIGNED THE JOB OF FLYING THE PLANE AND COORDINATING WITH ATC FOR POSSIBLE AIR INTERRUPT TO LAS. I DID NOT PARTICIPATE IN THE CHKLIST ABNORMAL PROCS OF DETERMINING THE PROBLEM AND CORRECTIONS. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: RPTR EXPLAINED THAT THEY HAD CLBED TO AND WERE LEVEL AT 33000 FT BEFORE THE CABIN CLBED TO 10000 FT. HE IS SURE THE PROBLEM WAS MECHANICAL. THEY ORBITED E OF LAS UNTIL THEY CLRED UP THE PROBLEM. THEY WERE THEN RECLRED TO JFK. THEIR ALTERNATE HAD TO BE REMOVED DUE TO THE FUEL THEY BURNED WHILE SOLVING THIS PROBLEM. RPTR INSISTS HE DOES NOT KNOW WHAT CAUSED IT.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.