Narrative:

On apr/mon/95 flight XXX departed stl with an FAA inspector in the cockpit acm seat. While cruising at FL350, the cabin pressure warning light came on with the cabin altitude at 10000 ft and rising slowly. After quickly completing cabin loss procedures, I increased power and the first officer selected a warmer temperature on both packs. This increased the air flow available to the packs for pressurization and the cabin pressure altitude improved a little. We asked for an received an immediate descent clearance from ATC along with vectors for aircraft spacing. We made a power on descent using full spoilers to control our speed and rate of descent. Any reduction in power or use of anti-ice caused the cabin altitude to rise. Passing approximately 20000 ft, the cabin altitude was approaching 14000 ft. We dropped the masks manually, checked the masks down visually and made a PA announcement to use the masks immediately. The L-1 hostess knocked on the door, and said she could not hear our PA clearly. The first officer told her to make another PA announcement and then make sure everyone was on oxygen. Approximately at this time, the aircraft caught the cabin at 15000 ft. Power was no longer needed for pressurization, so anti- ice came on, and a power off maximum rate descent to 10000 ft was accomplished under 60 seconds. The passenger were briefed to come off the oxygen. Total time on oxygen was under 2 mins. We diverted to okc, when ATC said they were holding for dfw, our original destination. Later on the ground at okc, the FAA inspector reviewed our performance during the emergency: 1) he did not think the outflow valve had been full closed. 2) he waited and waited for us to use our checklist. 3) he did not like the first officer using his hand microphone rather than his oxygen mask microphone. 4) he did not like L-1 asking about our mask announcement to the passenger. I very strongly told the FAA inspector that he should have spoken up immediately during the emergency, not now, after the fact. I further stated the outflow valve was repeatedly checked full closed, during the descent to 10000 ft, by both pilots. All items on the checklist had been completed, but had he mentioned the checklist, we would have used it to double-check our procedures, early in the emergency, time permitting, our first duty was to fly the aircraft, then handle the emergency, then use the checklist as time permitted. It was lost in the workload in error. The first officer found the hand microphone transmitted better and faster than his oxygen mask microphone. The mask microphone was usable, but not as good. Had the cabin pressure altitude been higher or for a longer time, he would have used his oxygen mask microphone. I did use my mask microphone. L-1 hostess wanted to understand our PA announcement, so she would not tell the passenger conflicting information. The total time the oxygen was used by the passenger was approximately 2 mins. Summary: maintenance found nothing wrong with the aircraft pressurization or pack system. Something controling either the outflow valve or the packs froze up at FL350. Increasing air flow to the packs was all that could be done, plus descended to 10000 ft. Mistakes and suggestions: 1) declaring an emergency to ATC, although ATC knew our problem and did all it could to help. It would not have hurt a thing to formally declare an emergency. 2) not using the checklist early in the emergency to double-check our procedures. Delaying too long can cause the checklist to be forgotten in the workload. 3) not having any communications between the acm (FAA) and the pilots, even though it would have made the emergency procedures safer. 4) not alerting the L-1 hostess early in the emergency that the oxygen mask might have to be dropped if the cabin altitude went above 14000 ft. 5) inability of ATC radar or our aircraft radar to paint, heavy icing, which compounded our problem when the heavy icing occurred.

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Original NASA ASRS Text

Title: EMERG TRAFFIC. ACR ACFT SLOWLY LOSES PRESSURE AND IS FORCED TO DSND. CREW FORGETS TO USE CHECKLIST.

Narrative: ON APR/MON/95 FLT XXX DEPARTED STL WITH AN FAA INSPECTOR IN THE COCKPIT ACM SEAT. WHILE CRUISING AT FL350, THE CABIN PRESSURE WARNING LIGHT CAME ON WITH THE CABIN ALT AT 10000 FT AND RISING SLOWLY. AFTER QUICKLY COMPLETING CABIN LOSS PROCS, I INCREASED PWR AND THE FO SELECTED A WARMER TEMP ON BOTH PACKS. THIS INCREASED THE AIR FLOW AVAILABLE TO THE PACKS FOR PRESSURIZATION AND THE CABIN PRESSURE ALT IMPROVED A LITTLE. WE ASKED FOR AN RECEIVED AN IMMEDIATE DSCNT CLRNC FROM ATC ALONG WITH VECTORS FOR ACFT SPACING. WE MADE A PWR ON DSCNT USING FULL SPOILERS TO CTL OUR SPD AND RATE OF DSCNT. ANY REDUCTION IN PWR OR USE OF ANTI-ICE CAUSED THE CABIN ALT TO RISE. PASSING APPROX 20000 FT, THE CABIN ALT WAS APCHING 14000 FT. WE DROPPED THE MASKS MANUALLY, CHKED THE MASKS DOWN VISUALLY AND MADE A PA ANNOUNCEMENT TO USE THE MASKS IMMEDIATELY. THE L-1 HOSTESS KNOCKED ON THE DOOR, AND SAID SHE COULD NOT HEAR OUR PA CLRLY. THE FO TOLD HER TO MAKE ANOTHER PA ANNOUNCEMENT AND THEN MAKE SURE EVERYONE WAS ON OXYGEN. APPROX AT THIS TIME, THE ACFT CAUGHT THE CABIN AT 15000 FT. PWR WAS NO LONGER NEEDED FOR PRESSURIZATION, SO ANTI- ICE CAME ON, AND A PWR OFF MAX RATE DSCNT TO 10000 FT WAS ACCOMPLISHED UNDER 60 SECONDS. THE PAX WERE BRIEFED TO COME OFF THE OXYGEN. TOTAL TIME ON OXYGEN WAS UNDER 2 MINS. WE DIVERTED TO OKC, WHEN ATC SAID THEY WERE HOLDING FOR DFW, OUR ORIGINAL DEST. LATER ON THE GND AT OKC, THE FAA INSPECTOR REVIEWED OUR PERFORMANCE DURING THE EMER: 1) HE DID NOT THINK THE OUTFLOW VALVE HAD BEEN FULL CLOSED. 2) HE WAITED AND WAITED FOR US TO USE OUR CHKLIST. 3) HE DID NOT LIKE THE FO USING HIS HAND MIKE RATHER THAN HIS OXYGEN MASK MIKE. 4) HE DID NOT LIKE L-1 ASKING ABOUT OUR MASK ANNOUNCEMENT TO THE PAX. I VERY STRONGLY TOLD THE FAA INSPECTOR THAT HE SHOULD HAVE SPOKEN UP IMMEDIATELY DURING THE EMER, NOT NOW, AFTER THE FACT. I FURTHER STATED THE OUTFLOW VALVE WAS REPEATEDLY CHKED FULL CLOSED, DURING THE DSCNT TO 10000 FT, BY BOTH PLTS. ALL ITEMS ON THE CHKLIST HAD BEEN COMPLETED, BUT HAD HE MENTIONED THE CHKLIST, WE WOULD HAVE USED IT TO DOUBLE-CHK OUR PROCS, EARLY IN THE EMER, TIME PERMITTING, OUR FIRST DUTY WAS TO FLY THE ACFT, THEN HANDLE THE EMER, THEN USE THE CHKLIST AS TIME PERMITTED. IT WAS LOST IN THE WORKLOAD IN ERROR. THE FO FOUND THE HAND MIKE XMITTED BETTER AND FASTER THAN HIS OXYGEN MASK MIKE. THE MASK MIKE WAS USABLE, BUT NOT AS GOOD. HAD THE CABIN PRESSURE ALT BEEN HIGHER OR FOR A LONGER TIME, HE WOULD HAVE USED HIS OXYGEN MASK MIKE. I DID USE MY MASK MIKE. L-1 HOSTESS WANTED TO UNDERSTAND OUR PA ANNOUNCEMENT, SO SHE WOULD NOT TELL THE PAX CONFLICTING INFO. THE TOTAL TIME THE OXYGEN WAS USED BY THE PAX WAS APPROX 2 MINS. SUMMARY: MAINT FOUND NOTHING WRONG WITH THE ACFT PRESSURIZATION OR PACK SYS. SOMETHING CTLING EITHER THE OUTFLOW VALVE OR THE PACKS FROZE UP AT FL350. INCREASING AIR FLOW TO THE PACKS WAS ALL THAT COULD BE DONE, PLUS DSNDED TO 10000 FT. MISTAKES AND SUGGESTIONS: 1) DECLARING AN EMER TO ATC, ALTHOUGH ATC KNEW OUR PROB AND DID ALL IT COULD TO HELP. IT WOULD NOT HAVE HURT A THING TO FORMALLY DECLARE AN EMER. 2) NOT USING THE CHKLIST EARLY IN THE EMER TO DOUBLE-CHK OUR PROCS. DELAYING TOO LONG CAN CAUSE THE CHKLIST TO BE FORGOTTEN IN THE WORKLOAD. 3) NOT HAVING ANY COMS BTWN THE ACM (FAA) AND THE PLTS, EVEN THOUGH IT WOULD HAVE MADE THE EMER PROCS SAFER. 4) NOT ALERTING THE L-1 HOSTESS EARLY IN THE EMER THAT THE OXYGEN MASK MIGHT HAVE TO BE DROPPED IF THE CABIN ALT WENT ABOVE 14000 FT. 5) INABILITY OF ATC RADAR OR OUR ACFT RADAR TO PAINT, HVY ICING, WHICH COMPOUNDED OUR PROB WHEN THE HVY ICING OCCURRED.

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.