Aircraft equipment problem malfunction creates need for lower altitude. Emergency not declared.

Attributes
ACN	266053
Time
Date	199403
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : mci
State Reference	MO
Altitude	msl bound lower : 10000 msl bound upper : 31000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zkc tracon : sat
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise other descent other other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 14000 flight time type : 5000
ASRS Report	266053
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : critical non adherence : published procedure
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : exited adverse environment other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

In cruise, FL310 had uncontrolled cabin climb. Went to manual cabin control and checked out flow valve full closed. Received descent clearance to FL240 at this time, and started descent as cabin continued to climb. Requested and received clearance to 10000 ft and regained cabin control below FL200. Cabin climbed to 9500 ft before starting down. Had flight attendants secure cabin and be seated as descent was started, and cockpit crew went on oxygen. Continued to mci at 10000 ft. Maintenance found blown duct on right pack system and I believe loose ducting on left side. Of course there is no specific procedure in our cockpit operating procedures book covering this event, but after reviewing procedures (in the hotel) it seems that the engine cabin pressure loss checklist basically covers what needed to be done. Unfortunately, I believe the mind set for this procedure is to use it after cabin pressure loss, and not as a preventive measure, which would have saved me a lot of confusion as to what really needed to be done.

Original NASA ASRS Text

Title: ACFT EQUIP PROB MALFUNCTION CREATES NEED FOR LOWER ALT. EMER NOT DECLARED.

Narrative: IN CRUISE, FL310 HAD UNCTLED CABIN CLB. WENT TO MANUAL CABIN CTL AND CHKED OUT FLOW VALVE FULL CLOSED. RECEIVED DSCNT CLRNC TO FL240 AT THIS TIME, AND STARTED DSCNT AS CABIN CONTINUED TO CLB. REQUESTED AND RECEIVED CLRNC TO 10000 FT AND REGAINED CABIN CTL BELOW FL200. CABIN CLBED TO 9500 FT BEFORE STARTING DOWN. HAD FLT ATTENDANTS SECURE CABIN AND BE SEATED AS DSCNT WAS STARTED, AND COCKPIT CREW WENT ON OXYGEN. CONTINUED TO MCI AT 10000 FT. MAINT FOUND BLOWN DUCT ON R PACK SYS AND I BELIEVE LOOSE DUCTING ON L SIDE. OF COURSE THERE IS NO SPECIFIC PROC IN OUR COCKPIT OPERATING PROCS BOOK COVERING THIS EVENT, BUT AFTER REVIEWING PROCS (IN THE HOTEL) IT SEEMS THAT THE ENG CABIN PRESSURE LOSS CHKLIST BASICALLY COVERS WHAT NEEDED TO BE DONE. UNFORTUNATELY, I BELIEVE THE MIND SET FOR THIS PROC IS TO USE IT AFTER CABIN PRESSURE LOSS, AND NOT AS A PREVENTIVE MEASURE, WHICH WOULD HAVE SAVED ME A LOT OF CONFUSION AS TO WHAT REALLY NEEDED TO BE DONE.

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.