A B727 flight crew loses cabin pressure at FL270 on their climb out and return land at msp, mn.

Attributes
ACN	513240
Time
Date	200105
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : pnm.ndb
State Reference	MN
Altitude	msl bound lower : 27000 msl bound upper : 28000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zmp.artcc artcc : zoa.artcc
Operator	common carrier : air carrier
Make Model Name	B727 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 240 flight time total : 9000 flight time type : 3000
ASRS Report	513240
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : multi engine pilot : flight engineer pilot : cfi pilot : atp
Experience	flight time last 90 days : 140 flight time total : 14000 flight time type : 6000
ASRS Report	512398
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	aircraft equipment other aircraft equipment : alt wng horn other flight crewa
Resolutory Action	flight crew : diverted to another airport flight crew : landed as precaution other
Consequence	other
Factors
Maintenance	contributing factor : engineering procedure performance deficiency : inspection performance deficiency : testing performance deficiency : fault isolation
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

At FL270, cabin altitude warning horn sounded. Leveled the aircraft at FL280 and tried to gain control of cabin pressurization. Went to standby mode on electronic pressure system with no effect. Used manual AC and dc modes to close outflow valves with no effect. Couldn't control cabin so we started a rapid descent to 10000 ft. An emergency was not declared because there was no other traffic in the area and ATC was able to accommodate our descent request immediately. We returned to the minneapolis airport without further incident. As trained, the first officer took over the flying and radio communications of the aircraft and the captain worked with the flight engineer on the problem. The flight engineer was also performing IOE on a new student at the time. The cabin reached an altitude of 13500 ft as the aircraft descended through 14000 ft. The crew had masks on until 10000 ft and the passenger masks were never deployed. Supplemental information from acn 512398: climbing through FL280, our so advised the cabin was climbing rapidly. Troubleshooting efforts stabilized the rate of climb to 300 FPM while the cabin was at 13000 ft. ATC cleared us for descent to 10000 ft where we flew depressurized and returned to msp uneventfully. It appeared the right air conditioning pack mix valve was frozen in the full cold position allowing very little air into the cabin. We coordinated with dispatch, maintenance and our flight attendants throughout the event. Communications were effective while on oxygen. The crew each contributed ideas on how to troubleshoot the problem.

Original NASA ASRS Text

Title: A B727 FLC LOSES CABIN PRESSURE AT FL270 ON THEIR CLBOUT AND RETURN LAND AT MSP, MN.

Narrative: AT FL270, CABIN ALT WARNING HORN SOUNDED. LEVELED THE ACFT AT FL280 AND TRIED TO GAIN CTL OF CABIN PRESSURIZATION. WENT TO STANDBY MODE ON ELECTRONIC PRESSURE SYS WITH NO EFFECT. USED MANUAL AC AND DC MODES TO CLOSE OUTFLOW VALVES WITH NO EFFECT. COULDN'T CTL CABIN SO WE STARTED A RAPID DSCNT TO 10000 FT. AN EMER WAS NOT DECLARED BECAUSE THERE WAS NO OTHER TFC IN THE AREA AND ATC WAS ABLE TO ACCOMMODATE OUR DSCNT REQUEST IMMEDIATELY. WE RETURNED TO THE MINNEAPOLIS ARPT WITHOUT FURTHER INCIDENT. AS TRAINED, THE FO TOOK OVER THE FLYING AND RADIO COMS OF THE ACFT AND THE CAPT WORKED WITH THE FE ON THE PROB. THE FE WAS ALSO PERFORMING IOE ON A NEW STUDENT AT THE TIME. THE CABIN REACHED AN ALT OF 13500 FT AS THE ACFT DSNDED THROUGH 14000 FT. THE CREW HAD MASKS ON UNTIL 10000 FT AND THE PAX MASKS WERE NEVER DEPLOYED. SUPPLEMENTAL INFO FROM ACN 512398: CLBING THROUGH FL280, OUR SO ADVISED THE CABIN WAS CLBING RAPIDLY. TROUBLESHOOTING EFFORTS STABILIZED THE RATE OF CLB TO 300 FPM WHILE THE CABIN WAS AT 13000 FT. ATC CLRED US FOR DSCNT TO 10000 FT WHERE WE FLEW DEPRESSURIZED AND RETURNED TO MSP UNEVENTFULLY. IT APPEARED THE R AIR CONDITIONING PACK MIX VALVE WAS FROZEN IN THE FULL COLD POS ALLOWING VERY LITTLE AIR INTO THE CABIN. WE COORDINATED WITH DISPATCH, MAINT AND OUR FLT ATTENDANTS THROUGHOUT THE EVENT. COMS WERE EFFECTIVE WHILE ON OXYGEN. THE CREW EACH CONTRIBUTED IDEAS ON HOW TO TROUBLESHOOT THE PROB.

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.