A B737-300 flight crew lost pressurization on departure from den.

Attributes
ACN	438648
Time
Date	199905
Day	Sun
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : den.vor
State Reference	CO
Altitude	msl single value : 19000
Environment
Flight Conditions	VMC
Weather Elements	Thunderstorm
Light	Night
Aircraft 1
Controlling Facilities	artcc : zdv.artcc
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	climbout : intermediate altitude
Route In Use	enroute other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : multi engine pilot : commercial pilot : cfi pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 145 flight time total : 3700 flight time type : 2700
ASRS Report	438648
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : multi engine pilot : commercial
Experience	flight time last 90 days : 240 flight time total : 2750
ASRS Report	439083
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : diverted to alternate
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

The left air conditioning pack was deferred inoperative. Prior to the flight, I consulted with dispatch and maintenance about the deferral and the history on the right pack which had tripped off previously. I was told by maintenance the right pack had not failed in 10 days and that a valve and sensor had just been replaced prior to my flight. During climb out at approximately FL190, the right pack tripped off, resulting in a loss of pressurization. The cabin altitude began to rapidly increase. I instructed the first officer to level off and I asked ATC for a lower altitude and a clearance back to our departure station. I received both. It was obvious the cabin altitude was going to exceed 10000 ft. Oxygen masks were donned and the quick reference emergency checklist for cabin altitude warning was accomplished. The maximum cabin altitude was 12500 ft. The passenger oxygen masks did not deploy. The irregular procedure for pack trip-off was also accomplished, but the right pack remained inoperative. I turned on the deferred inoperative left pack and it worked. Some pressurization was restored. I again pushed the trip reset button and the right pack reset. The left pack failed a short time later.

Original NASA ASRS Text

Title: A B737-300 FLC LOST PRESSURIZATION ON DEP FROM DEN.

Narrative: THE L AIR CONDITIONING PACK WAS DEFERRED INOP. PRIOR TO THE FLT, I CONSULTED WITH DISPATCH AND MAINT ABOUT THE DEFERRAL AND THE HISTORY ON THE R PACK WHICH HAD TRIPPED OFF PREVIOUSLY. I WAS TOLD BY MAINT THE R PACK HAD NOT FAILED IN 10 DAYS AND THAT A VALVE AND SENSOR HAD JUST BEEN REPLACED PRIOR TO MY FLT. DURING CLBOUT AT APPROX FL190, THE R PACK TRIPPED OFF, RESULTING IN A LOSS OF PRESSURIZATION. THE CABIN ALT BEGAN TO RAPIDLY INCREASE. I INSTRUCTED THE FO TO LEVEL OFF AND I ASKED ATC FOR A LOWER ALT AND A CLRNC BACK TO OUR DEP STATION. I RECEIVED BOTH. IT WAS OBVIOUS THE CABIN ALT WAS GOING TO EXCEED 10000 FT. OXYGEN MASKS WERE DONNED AND THE QUICK REF EMER CHKLIST FOR CABIN ALT WARNING WAS ACCOMPLISHED. THE MAX CABIN ALT WAS 12500 FT. THE PAX OXYGEN MASKS DID NOT DEPLOY. THE IRREGULAR PROC FOR PACK TRIP-OFF WAS ALSO ACCOMPLISHED, BUT THE R PACK REMAINED INOP. I TURNED ON THE DEFERRED INOP L PACK AND IT WORKED. SOME PRESSURIZATION WAS RESTORED. I AGAIN PUSHED THE TRIP RESET BUTTON AND THE R PACK RESET. THE L PACK FAILED A SHORT TIME LATER.

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.