Narrative:

While cruising at FL330, we heard a 'groaning' noise similar to an engine 'rollback', followed by a a/C pack number 1 fault trip off, chime, and checklist on the MFDU. Followed checklist, waited a little over the two min minimum, and reset PACK1, completed checklist and got out the book for expanded information. Approximately two mins later, again heard the same noise followed by PACK1 fault light again, accomplished checklist and did not reset, consulted the book and discussed descending just as a precaution, fuel permitting. Just as we were about to ask for a lower altitude, about FL250 was a good idea, PACK2 now also faulted without warning or the same odd noise. We immediately donned oxygen masks, established communications and I, PNF, requested an immediate lower altitude due to a press as problem and center turned us 20 left off of the airway. During descent, monitored the cabin rate of climb press. Differential, and cabin altitude, which was not climbing too badly, as this aircraft was pretty 'tight'. During the descent, accomplished the checklist for pack 1 and 2 fault, and reset pack 2. It came back on and held for the rest of the flight and we flew at FL240 with plenty of fuel reserve. Center of course wanted to know if we needed any further assistance or wanted to declare an emergency, and we told them no that we had recovered one air conditioner and pressurization was ok now. I called ZZZ1 dispatch on the radio and let them know what was going on and the dispatcher, first officer, and I discussed alternatives if pack 2 faulted again, and we made a good plan and they took care of letting maintenance and ZZZ2 know that we were coming in needing maintenance action. This is a repeat identical series of malfunctions that occurred on this aircraft a few days before. Due to the smoothness of the first officer/PF, and the fact that the cabin pressure held better than expected. Callback conversation with reporter revealed the following information: the reporter stated the failure of the left #1 air conditioning pack was caused by the failure of the #1 pressure regulator and shutoff valve. The reporter said this was a repeat identical failure on this aircraft a few days before. The reporter stated the #2 pack after tripping off was reset after two mins and operated normally the remainder of the trip. The reporter said the maintenance action on #2 pack, if any, is unknown.

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Original NASA ASRS Text

Title: A FOKKER 100 IN CRUISE AT FL330 HAD #1 PACK FAIL. RESET, FAILED AGAIN. FEW MINS LATER #2 PACK FAILED. DESCENDED TO FL240 AND RESET #2 PACK OPS OK.

Narrative: WHILE CRUISING AT FL330, WE HEARD A 'GROANING' NOISE SIMILAR TO AN ENG 'ROLLBACK', FOLLOWED BY A A/C PACK NUMBER 1 FAULT TRIP OFF, CHIME, AND CHKLIST ON THE MFDU. FOLLOWED CHKLIST, WAITED A LITTLE OVER THE TWO MIN MINIMUM, AND RESET PACK1, COMPLETED CHKLIST AND GOT OUT THE BOOK FOR EXPANDED INFO. APPROX TWO MINS LATER, AGAIN HEARD THE SAME NOISE FOLLOWED BY PACK1 FAULT LIGHT AGAIN, ACCOMPLISHED CHKLIST AND DID NOT RESET, CONSULTED THE BOOK AND DISCUSSED DSNDING JUST AS A PRECAUTION, FUEL PERMITTING. JUST AS WE WERE ABOUT TO ASK FOR A LOWER ALT, ABOUT FL250 WAS A GOOD IDEA, PACK2 NOW ALSO FAULTED WITHOUT WARNING OR THE SAME ODD NOISE. WE IMMEDIATELY DONNED OXYGEN MASKS, ESTABLISHED COMS AND I, PNF, REQUESTED AN IMMEDIATE LOWER ALT DUE TO A PRESS AS PROB AND CENTER TURNED US 20 L OFF OF THE AIRWAY. DURING DSCNT, MONITORED THE CABIN RATE OF CLB PRESS. DIFFERENTIAL, AND CABIN ALTITUDE, WHICH WAS NOT CLBING TOO BADLY, AS THIS ACFT WAS PRETTY 'TIGHT'. DURING THE DSCNT, ACCOMPLISHED THE CHKLIST FOR PACK 1 AND 2 FAULT, AND RESET PACK 2. IT CAME BACK ON AND HELD FOR THE REST OF THE FLT AND WE FLEW AT FL240 WITH PLENTY OF FUEL RESERVE. CENTER OF COURSE WANTED TO KNOW IF WE NEEDED ANY FURTHER ASSISTANCE OR WANTED TO DECLARE AN EMER, AND WE TOLD THEM NO THAT WE HAD RECOVERED ONE AIR CONDITIONER AND PRESSURIZATION WAS OK NOW. I CALLED ZZZ1 DISPATCH ON THE RADIO AND LET THEM KNOW WHAT WAS GOING ON AND THE DISPATCHER, FO, AND I DISCUSSED ALTERNATIVES IF PACK 2 FAULTED AGAIN, AND WE MADE A GOOD PLAN AND THEY TOOK CARE OF LETTING MAINT AND ZZZ2 KNOW THAT WE WERE COMING IN NEEDING MAINT ACTION. THIS IS A REPEAT IDENTICAL SERIES OF MALFUNCTIONS THAT OCCURRED ON THIS ACFT A FEW DAYS BEFORE. DUE TO THE SMOOTHNESS OF THE FO/PF, AND THE FACT THAT THE CABIN PRESSURE HELD BETTER THAN EXPECTED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE FAILURE OF THE L #1 AIR CONDITIONING PACK WAS CAUSED BY THE FAILURE OF THE #1 PRESSURE REGULATOR AND SHUTOFF VALVE. THE RPTR SAID THIS WAS A REPEAT IDENTICAL FAILURE ON THIS ACFT A FEW DAYS BEFORE. THE RPTR STATED THE #2 PACK AFTER TRIPPING OFF WAS RESET AFTER TWO MINS AND OPERATED NORMALLY THE REMAINDER OF THE TRIP. THE RPTR SAID THE MAINT ACTION ON #2 PACK, IF ANY, IS UNKNOWN.

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.