Loss of cabin pressure in large transport mandates emergency descent to 10000 ft.

Attributes
ACN	228980
Time
Date	199212
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : elp
State Reference	TX
Altitude	msl bound lower : 10000 msl bound upper : 37000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zab artcc : zse
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other descent other other
Route In Use	enroute airway : j86
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : second officer
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 210 flight time total : 5500 flight time type : 600
ASRS Report	228980
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 210 flight time total : 11000 flight time type : 2000
ASRS Report	228965
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : exited adverse environment flight crew : overcame equipment problem flight crew : declared emergency other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

At FL370 left duct trip on an large transport, right pack unable to hold the cabin and indicated a need for emergency descent. Cabin altitude exceeded 15000 ft, masks dropped. Regained pressurization of cabin in the high teens but descended to 10000 ft for safety and continued to iah uneventfully. All passenger fine and cabin attendants performed well. Aircraft had a long history of pressure and air conditioning problems. Now my crew is being questioned about why we flew an airplane with this history to FL370, when they should have taken aircraft OTS. Same old thing -- company shoves their problems down the line pilot and when it blows up, they throw their hands up and blame it on us. Supplemental information from acn 228965: at 37000 ft, a bleed trip occurred in the left air conditioning system. Right pack could not hold the cabin. Cabin altitude reached 13500 ft. Dropped masks in cabin and performed emergency descent. Right pack had a failure of 35 degrees switch causing right pack to freeze, which led to the bleed trip in the left system.

Original NASA ASRS Text

Title: LOSS OF CABIN PRESSURE IN LGT MANDATES EMER DSCNT TO 10000 FT.

Narrative: AT FL370 L DUCT TRIP ON AN LGT, R PACK UNABLE TO HOLD THE CABIN AND INDICATED A NEED FOR EMER DSCNT. CABIN ALT EXCEEDED 15000 FT, MASKS DROPPED. REGAINED PRESSURIZATION OF CABIN IN THE HIGH TEENS BUT DSNDED TO 10000 FT FOR SAFETY AND CONTINUED TO IAH UNEVENTFULLY. ALL PAX FINE AND CABIN ATTENDANTS PERFORMED WELL. ACFT HAD A LONG HISTORY OF PRESSURE AND AIR CONDITIONING PROBS. NOW MY CREW IS BEING QUESTIONED ABOUT WHY WE FLEW AN AIRPLANE WITH THIS HISTORY TO FL370, WHEN THEY SHOULD HAVE TAKEN ACFT OTS. SAME OLD THING -- COMPANY SHOVES THEIR PROBS DOWN THE LINE PLT AND WHEN IT BLOWS UP, THEY THROW THEIR HANDS UP AND BLAME IT ON US. SUPPLEMENTAL INFO FROM ACN 228965: AT 37000 FT, A BLEED TRIP OCCURRED IN THE L AIR CONDITIONING SYS. R PACK COULD NOT HOLD THE CABIN. CABIN ALT REACHED 13500 FT. DROPPED MASKS IN CABIN AND PERFORMED EMER DSCNT. R PACK HAD A FAILURE OF 35 DEGS SWITCH CAUSING R PACK TO FREEZE, WHICH LED TO THE BLEED TRIP IN THE L SYS.

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.