<< >> NASA ASRS Report 149803, July 1990

Air carrier large transport experiences loss of 1 of 2 air conditioning packs, forced to descend to maintain cabin pressure.

Attributes
ACN	149803
Time
Date	199007
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : cty
State Reference	FL
Altitude	msl bound lower : 23000 msl bound upper : 26000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zjx
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	climbout : intermediate altitude cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 30 flight time total : 14000 flight time type : 1800
ASRS Report	149803
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : commercial pilot : flight engineer pilot : cfi pilot : instrument
Experience	flight time last 90 days : 250 flight time total : 8000 flight time type : 250
ASRS Report	149888
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : overcame equipment problem flight crew : declared emergency
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

At approximately FL260 climbing, the cabin altitude exceeded 10000', to a maximum of 10500'. Alerted by warning horn. Immediately requested a lower altitude, and received clearance to FL240. Asked for clearance to FL210. Was denied clearance by ATC below FL240. I declared an emergency and descended to FL230, at which point control of the cabin altitude was regained. Continued to destination, ord at FL240 west/O further incident. Failure of adequate pressurization due to failure of adequate performance of right air conditioning pack, caused by apparent failure of #3 engine bleed. No warning lights were illuminated. Cabin altitude warning horn sounded when cabin exceeded 10000'.

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Original NASA ASRS Text

Title: ACR LGT EXPERIENCES LOSS OF 1 OF 2 AIR CONDITIONING PACKS, FORCED TO DESCEND TO MAINTAIN CABIN PRESSURE.

Narrative: AT APPROX FL260 CLBING, THE CABIN ALT EXCEEDED 10000', TO A MAX OF 10500'. ALERTED BY WARNING HORN. IMMEDIATELY REQUESTED A LOWER ALT, AND RECEIVED CLRNC TO FL240. ASKED FOR CLRNC TO FL210. WAS DENIED CLRNC BY ATC BELOW FL240. I DECLARED AN EMER AND DSNDED TO FL230, AT WHICH POINT CTL OF THE CABIN ALT WAS REGAINED. CONTINUED TO DEST, ORD AT FL240 W/O FURTHER INCIDENT. FAILURE OF ADEQUATE PRESSURIZATION DUE TO FAILURE OF ADEQUATE PERFORMANCE OF RIGHT AIR CONDITIONING PACK, CAUSED BY APPARENT FAILURE OF #3 ENG BLEED. NO WARNING LIGHTS WERE ILLUMINATED. CABIN ALT WARNING HORN SOUNDED WHEN CABIN EXCEEDED 10000'.

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.