Narrative:

Loss of pressurization at FL310 with 4 passenger on board. Had been level at FL310 for approximately 5 mins when we heard a pop, felt a little surge in the ears and checked the cabin pressurization and saw the cabin altitude rising. We placed our masks on and requested a descent to a lower altitude. We were initially cleared to FL180 where we leveled off for approximately 1 min while requesting lower. We were then cleared down to 10000 ft where we remained. We did not declare an emergency and only stated that we were unable to maintain pressurization. It took several mins for the cabin altitude to reach 10000 ft and the warning light to come on. The passenger oxygen masks eventually automatically deployed and the passenger put them on. We got down to 10000 ft and removed our masks and checked on the passenger. The depressurization was not explosive and no one seemed affected. Everyone's ears felt fine so we continued the flight to our destination at 10000 ft, which was about 45 mins to 1 hour. We continued on because the loss of pressurization had not been drastic and everyone felt fine, we were at an altitude where we didn't need to be pressurized so we felt it was ok. We failed to consider why the pressurization failed, other than the door seal, might have failed and that we should probably have landed at the nearest suitable field and have it investigated.

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Original NASA ASRS Text

Title: CESSNA 550, CITATION II, ACFT HAD DEPRESSURIZATION. FLC AND PAX USED OXYGEN MASKS, BUT FLC DID NOT DECLARE EMER.

Narrative: LOSS OF PRESSURIZATION AT FL310 WITH 4 PAX ON BOARD. HAD BEEN LEVEL AT FL310 FOR APPROX 5 MINS WHEN WE HEARD A POP, FELT A LITTLE SURGE IN THE EARS AND CHKED THE CABIN PRESSURIZATION AND SAW THE CABIN ALT RISING. WE PLACED OUR MASKS ON AND REQUESTED A DSCNT TO A LOWER ALT. WE WERE INITIALLY CLRED TO FL180 WHERE WE LEVELED OFF FOR APPROX 1 MIN WHILE REQUESTING LOWER. WE WERE THEN CLRED DOWN TO 10000 FT WHERE WE REMAINED. WE DID NOT DECLARE AN EMER AND ONLY STATED THAT WE WERE UNABLE TO MAINTAIN PRESSURIZATION. IT TOOK SEVERAL MINS FOR THE CABIN ALT TO REACH 10000 FT AND THE WARNING LIGHT TO COME ON. THE PAX OXYGEN MASKS EVENTUALLY AUTOMATICALLY DEPLOYED AND THE PAX PUT THEM ON. WE GOT DOWN TO 10000 FT AND REMOVED OUR MASKS AND CHKED ON THE PAX. THE DEPRESSURIZATION WAS NOT EXPLOSIVE AND NO ONE SEEMED AFFECTED. EVERYONE'S EARS FELT FINE SO WE CONTINUED THE FLT TO OUR DEST AT 10000 FT, WHICH WAS ABOUT 45 MINS TO 1 HR. WE CONTINUED ON BECAUSE THE LOSS OF PRESSURIZATION HAD NOT BEEN DRASTIC AND EVERYONE FELT FINE, WE WERE AT AN ALT WHERE WE DIDN'T NEED TO BE PRESSURIZED SO WE FELT IT WAS OK. WE FAILED TO CONSIDER WHY THE PRESSURIZATION FAILED, OTHER THAN THE DOOR SEAL, MIGHT HAVE FAILED AND THAT WE SHOULD PROBABLY HAVE LANDED AT THE NEAREST SUITABLE FIELD AND HAVE IT INVESTIGATED.

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.