Narrative:

Aircraft xyz arrived with pilot item of noisy left pack. Aircraft was moved to hardstand area to repair. 2 mechanics troubleshot and replaced a modulating valve. This did not correct item. Aircraft XXX canceled at gate with an anti-skid problem that was a no-go due to WX. Instead of extending estimated return to service on aircraft xyz, it was decided to place aircraft xyz left air conditioning pack on MEL. The MEL specification procedures were not clear. Aircraft xyz was taken to gate to take place of aircraft XXX. Aircraft xyz returned to field after approximately 45 mins of flight. Pilot complained of noise still coming from left pack even though pack was turned off. It seemed the turbine itself was failing and noise was coming from ram air turning the turbine. After discussion with maintenance control we took aircraft OTS and replaced left air conditioning pack.

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Original NASA ASRS Text

Title: A FOKKER 100 WAS DISPATCHED IN NON COMPLIANCE WITH THE L PACK DEFERRED AS INOP PER THE MEL BUT THE SPECIAL PROCS WERE NOT ACCOMPLISHED.

Narrative: ACFT XYZ ARRIVED WITH PLT ITEM OF NOISY L PACK. ACFT WAS MOVED TO HARDSTAND AREA TO REPAIR. 2 MECHS TROUBLESHOT AND REPLACED A MODULATING VALVE. THIS DID NOT CORRECT ITEM. ACFT XXX CANCELED AT GATE WITH AN ANTI-SKID PROB THAT WAS A NO-GO DUE TO WX. INSTEAD OF EXTENDING ESTIMATED RETURN TO SVC ON ACFT XYZ, IT WAS DECIDED TO PLACE ACFT XYZ L AIR CONDITIONING PACK ON MEL. THE MEL SPEC PROCS WERE NOT CLR. ACFT XYZ WAS TAKEN TO GATE TO TAKE PLACE OF ACFT XXX. ACFT XYZ RETURNED TO FIELD AFTER APPROX 45 MINS OF FLT. PLT COMPLAINED OF NOISE STILL COMING FROM L PACK EVEN THOUGH PACK WAS TURNED OFF. IT SEEMED THE TURBINE ITSELF WAS FAILING AND NOISE WAS COMING FROM RAM AIR TURNING THE TURBINE. AFTER DISCUSSION WITH MAINT CTL WE TOOK ACFT OTS AND REPLACED L AIR CONDITIONING PACK.

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.