|37000 Feet||Browse and search NASA's
Aviation Safety Reporting System
|Local Time Of Day||0601 To 1200|
|Locale Reference||atc facility : den|
|Altitude||msl bound lower : 35000|
msl bound upper : 35000
|Controlling Facilities||artcc : zdv|
|Operator||common carrier : air carrier|
|Make Model Name||Medium Large Transport, Low Wing, 2 Turbojet Eng|
|Flight Phase||cruise other|
|Affiliation||company : air carrier|
|Function||flight crew : captain|
oversight : pic
|Qualification||pilot : atp|
|Experience||flight time last 90 days : 250|
flight time total : 18300
|Function||controller : radar|
|Qualification||controller : radar|
|Anomaly||aircraft equipment problem : critical|
|Independent Detector||aircraft equipment other aircraft equipment : unspecified|
|Resolutory Action||flight crew : overcame equipment problem|
|Air Traffic Incident||other|
We were at 35000' when I decided to adjust the cabin temperature to a lower setting. The right air conditioning pack tripped. Normally the remaining left pack will hold the pressurization system. However, this time it didn't. The cabin started up at a rapid rate and I was finally able to regain control of the cabin at 12000'. Automatic, standby or manual control was fruitless until I could get the right pack back on the line. I then requested and got a clearance from ATC to descend to a lower altitude. Center was very helpful and passed on information to the next sectors on our situation. We received additional lower altitudes in order to get our cabin to field elevation altitude. Because our forward outflow valve wouldn't close we could not get full pressure differential. I just want to say again that cooperation with ATC was excellent. The approach and landing came off fine and we didn't drop the masks.
Original NASA ASRS Text
Title: ACR MLG HAD PRESSURIZATION PROBLEMS AT CRUISE ALT FL350.
Narrative: WE WERE AT 35000' WHEN I DECIDED TO ADJUST THE CABIN TEMP TO A LOWER SETTING. THE RIGHT AIR CONDITIONING PACK TRIPPED. NORMALLY THE REMAINING LEFT PACK WILL HOLD THE PRESSURIZATION SYS. HOWEVER, THIS TIME IT DIDN'T. THE CABIN STARTED UP AT A RAPID RATE AND I WAS FINALLY ABLE TO REGAIN CTL OF THE CABIN AT 12000'. AUTO, STANDBY OR MANUAL CTL WAS FRUITLESS UNTIL I COULD GET THE RIGHT PACK BACK ON THE LINE. I THEN REQUESTED AND GOT A CLRNC FROM ATC TO DSND TO A LOWER ALT. CENTER WAS VERY HELPFUL AND PASSED ON INFO TO THE NEXT SECTORS ON OUR SITUATION. WE RECEIVED ADDITIONAL LOWER ALTS IN ORDER TO GET OUR CABIN TO FIELD ELEVATION ALT. BECAUSE OUR FORWARD OUTFLOW VALVE WOULDN'T CLOSE WE COULD NOT GET FULL PRESSURE DIFFERENTIAL. I JUST WANT TO SAY AGAIN THAT COOPERATION WITH ATC WAS EXCELLENT. THE APCH AND LNDG CAME OFF FINE AND WE DIDN'T DROP THE MASKS.
Data retrieved from NASA's ASRS site as of August 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.