<< >> NASA ASRS Report 248250, July 1993

Flight crew of an medium large transport air carrier aircraft experienced a short failure of the aircraft cabin pressurization system during descent.

Attributes
ACN	248250
Time
Date	199307
Day	Sat
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : jfk
State Reference	NY
Altitude	msl bound lower : 14000 msl bound upper : 14000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : n90
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : flight engineer pilot : cfi
Experience	flight time last 90 days : 40 flight time total : 6915 flight time type : 1967
ASRS Report	248250
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	aircraft : equipment problem dissipated flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

During idle steep descent into jfk, we received an intermittent warning horn. Unsure at first of the origin of the horn, we decided I would fly the aircraft while first officer trouble-shot the cause of the horn. The horn continued for a min or 2 and when our ears popped due to the relief valves at about 10000 ft we were aware that the cabin was at 10000 ft. Prior to this, we had no evidence of pressurization problem, and crew, who dropped aircraft off in pit did not mention anything reference a pressure problem. At 10000 ft, aircraft on autoplt, we switched to standby mode since pressurization outflow valve was indicating open. Manual air conditioning modes also worked fine, and then automatic was selected. It too worked fine. The cabin altitude came down to intended setting after that without any further occurrence of anything out of the ordinary.

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Original NASA ASRS Text

Title: FLC OF AN MLG ACR ACFT EXPERIENCED A SHORT FAILURE OF THE ACFT CABIN PRESSURIZATION SYS DURING DSCNT.

Narrative: DURING IDLE STEEP DSCNT INTO JFK, WE RECEIVED AN INTERMITTENT WARNING HORN. UNSURE AT FIRST OF THE ORIGIN OF THE HORN, WE DECIDED I WOULD FLY THE ACFT WHILE FO TROUBLE-SHOT THE CAUSE OF THE HORN. THE HORN CONTINUED FOR A MIN OR 2 AND WHEN OUR EARS POPPED DUE TO THE RELIEF VALVES AT ABOUT 10000 FT WE WERE AWARE THAT THE CABIN WAS AT 10000 FT. PRIOR TO THIS, WE HAD NO EVIDENCE OF PRESSURIZATION PROB, AND CREW, WHO DROPPED ACFT OFF IN PIT DID NOT MENTION ANYTHING REF A PRESSURE PROB. AT 10000 FT, ACFT ON AUTOPLT, WE SWITCHED TO STANDBY MODE SINCE PRESSURIZATION OUTFLOW VALVE WAS INDICATING OPEN. MANUAL AIR CONDITIONING MODES ALSO WORKED FINE, AND THEN AUTOMATIC WAS SELECTED. IT TOO WORKED FINE. THE CABIN ALT CAME DOWN TO INTENDED SETTING AFTER THAT WITHOUT ANY FURTHER OCCURRENCE OF ANYTHING OUT OF THE ORDINARY.

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.