Narrative:

The start up taxi and takeoff were normal. At approximately 4000' MSL, climbing to 10000' in a left turn to join J121, the master caution lights illuminated indicating a 'select flap limit override', light was activated. The captain instructed me to take the controls and continue to work the radio's while he monitored the second officer and myself. I acknowledged and took the controls. During the next 5 mins I received and complied with several step climb clrncs. A few mins later, I heard the second officer announce that the flap limit override checklist was complete. Immediately after that the, 'avionics flow off' light came on. I continued to fly and work the radios. At approximately 18000' MSL the 'cabin altitude' warn light and horn came on. First the captain told me to level off at FL210, I recieved clearance from ATC and did so. The captain instructed everyone in the cockpit to 'go to oxy'. At the same time he told me to get us a descent to 14000' (note: this was not an explosive decompression, however the second officer could not control the cabin in automatic mode). When I asked ATC for a clearance back down to 14000' he told me to 'standby'. The captain again asked me to get a descent clearance to 14000' (he and the second officer were still trying to control the cabin pressurization), I again asked for descent to 14000' and got no reply. The captain finally asked the second officer if he could control the cabin. The second officer said no. The captain then took the controls and said 'I'm initiating an emergency descent'. I gave up the controls and transmitted over the center frequency that we were making an emergency descent to 14000'. The descent went as checklist requires and with no conflict with other traffic (the controller did acknowledge my emergency transmission). We, after talking to the company, elected to fly over the atlantic and dump fuel and return to chs. We did so with no more problems. Captain showed excellent crew coordination by utilizing us and assigning us to specific tasks so that while the multiple problems came up, the aircraft continued to be flown on course and all clrncs were adhered to. As of the date of this letter the cause of the decompression was still not known to me.

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Original NASA ASRS Text

Title: ACR WDB ON MILITARY CHARTER EXPERIENCES PRESSURIZATION AND OTHER PROBLEMS ON CLIMB OUT FROM CHS.

Narrative: THE START UP TAXI AND TKOF WERE NORMAL. AT APPROX 4000' MSL, CLBING TO 10000' IN A L TURN TO JOIN J121, THE MASTER CAUTION LIGHTS ILLUMINATED INDICATING A 'SELECT FLAP LIMIT OVERRIDE', LIGHT WAS ACTIVATED. THE CAPT INSTRUCTED ME TO TAKE THE CTLS AND CONTINUE TO WORK THE RADIO'S WHILE HE MONITORED THE S/O AND MYSELF. I ACKNOWLEDGED AND TOOK THE CTLS. DURING THE NEXT 5 MINS I RECEIVED AND COMPLIED WITH SEVERAL STEP CLB CLRNCS. A FEW MINS LATER, I HEARD THE S/O ANNOUNCE THAT THE FLAP LIMIT OVERRIDE CHKLIST WAS COMPLETE. IMMEDIATELY AFTER THAT THE, 'AVIONICS FLOW OFF' LIGHT CAME ON. I CONTINUED TO FLY AND WORK THE RADIOS. AT APPROX 18000' MSL THE 'CABIN ALT' WARN LIGHT AND HORN CAME ON. FIRST THE CAPT TOLD ME TO LEVEL OFF AT FL210, I RECIEVED CLRNC FROM ATC AND DID SO. THE CAPT INSTRUCTED EVERYONE IN THE COCKPIT TO 'GO TO OXY'. AT THE SAME TIME HE TOLD ME TO GET US A DSNT TO 14000' (NOTE: THIS WAS NOT AN EXPLOSIVE DECOMPRESSION, HOWEVER THE S/O COULD NOT CTL THE CABIN IN AUTOMATIC MODE). WHEN I ASKED ATC FOR A CLRNC BACK DOWN TO 14000' HE TOLD ME TO 'STANDBY'. THE CAPT AGAIN ASKED ME TO GET A DSNT CLRNC TO 14000' (HE AND THE S/O WERE STILL TRYING TO CTL THE CABIN PRESSURIZATION), I AGAIN ASKED FOR DSNT TO 14000' AND GOT NO REPLY. THE CAPT FINALLY ASKED THE S/O IF HE COULD CTL THE CABIN. THE S/O SAID NO. THE CAPT THEN TOOK THE CTLS AND SAID 'I'M INITIATING AN EMER DSNT'. I GAVE UP THE CTLS AND XMITTED OVER THE CTR FREQ THAT WE WERE MAKING AN EMER DSNT TO 14000'. THE DSNT WENT AS CHKLIST REQUIRES AND WITH NO CONFLICT WITH OTHER TFC (THE CTLR DID ACKNOWLEDGE MY EMER XMISSION). WE, AFTER TALKING TO THE COMPANY, ELECTED TO FLY OVER THE ATLANTIC AND DUMP FUEL AND RETURN TO CHS. WE DID SO WITH NO MORE PROBS. CAPT SHOWED EXCELLENT CREW COORD BY UTILIZING US AND ASSIGNING US TO SPECIFIC TASKS SO THAT WHILE THE MULTIPLE PROBS CAME UP, THE ACFT CONTINUED TO BE FLOWN ON COURSE AND ALL CLRNCS WERE ADHERED TO. AS OF THE DATE OF THIS LETTER THE CAUSE OF THE DECOMPRESSION WAS STILL NOT KNOWN TO ME.

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.