MD80 flight crew has loss of pressurization while climb to altitude; declares emergency and diverts ...

Attributes
ACN	698395
Time
Date	200605
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl single value : 27000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zzz.artcc
Operator	common carrier : air carrier
Make Model Name	MD-81
Operating Under FAR Part	Part 121
Flight Plan	IFR
Aircraft 2
Flight Phase	climbout : intermediate altitude
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
ASRS Report	698395
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude
Independent Detector	aircraft equipment other aircraft equipment : cabin controller other flight crewa other flight crewb
Resolutory Action	controller : provided flight assist flight crew : landed as precaution flight crew : overcame equipment problem flight crew : declared emergency flight crew : diverted to another airport
Consequence	other
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance
Primary Problem	Aircraft

Narrative:

After departing ZZZ; climbing through 17000 ft; the 'pressurization flow' light illuminated. We began the associated QRH procedure. Selecting a warmer temperature to slow the cabin climb rate. This worked for a short time; but passing FL270 the cabin began to climb unctlably. Outflow valve was fully closed and both packs indicated normal pressure. As the cabin altitude was climbing at an alarming rate and approaching 8000 ft; I instructed the first officer/PF to begin a descent even though we did not have clearance to a lower altitude. Frequency congestion made it difficult to get a clear call to ATC; so I was exercising my emergency authority/authorized. I was soon able to declare an emergency with ATC for the descent and do not believe there was any loss of separation with other aircraft. We were able to stabilize the cabin at FL240 for the return to ZZZ would not allow cruise at FL240 by my quick calculation. Priority handling was no longer necessary after that point; so we flew a normal approach profile to an uneventful landing.

Original NASA ASRS Text

Title: MD80 FLT CREW HAS LOSS OF PRESSURIZATION WHILE CLB TO ALT; DECLARES EMER AND DIVERTS FOR LNDG.

Narrative: AFTER DEPARTING ZZZ; CLBING THROUGH 17000 FT; THE 'PRESSURIZATION FLOW' LIGHT ILLUMINATED. WE BEGAN THE ASSOCIATED QRH PROC. SELECTING A WARMER TEMP TO SLOW THE CABIN CLB RATE. THIS WORKED FOR A SHORT TIME; BUT PASSING FL270 THE CABIN BEGAN TO CLB UNCTLABLY. OUTFLOW VALVE WAS FULLY CLOSED AND BOTH PACKS INDICATED NORMAL PRESSURE. AS THE CABIN ALT WAS CLBING AT AN ALARMING RATE AND APCHING 8000 FT; I INSTRUCTED THE FO/PF TO BEGIN A DSCNT EVEN THOUGH WE DID NOT HAVE CLRNC TO A LOWER ALT. FREQ CONGESTION MADE IT DIFFICULT TO GET A CLR CALL TO ATC; SO I WAS EXERCISING MY EMER AUTH. I WAS SOON ABLE TO DECLARE AN EMER WITH ATC FOR THE DSCNT AND DO NOT BELIEVE THERE WAS ANY LOSS OF SEPARATION WITH OTHER ACFT. WE WERE ABLE TO STABILIZE THE CABIN AT FL240 FOR THE RETURN TO ZZZ WOULD NOT ALLOW CRUISE AT FL240 BY MY QUICK CALCULATION. PRIORITY HANDLING WAS NO LONGER NECESSARY AFTER THAT POINT; SO WE FLEW A NORMAL APCH PROFILE TO AN UNEVENTFUL LNDG.

Data retrieved from NASA's ASRS site as of January 2009 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.

MD80 flight crew has loss of pressurization while climb to altitude; declares emergency and diverts for landing.