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Commuter flight crew misinterp minimum equipment list requirement.
| Attributes | |
| ACN | 163535 |
| Time | |
| Date | 199011 |
| Day | Tue |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : den |
| State Reference | CO |
| Altitude | msl bound lower : 17000 msl bound upper : 17000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zdv |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Transport, High Wing, 2 Turboprop Eng |
| Navigation In Use | Other |
| Flight Phase | cruise other ground : preflight |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 240 flight time total : 13500 flight time type : 2000 |
| ASRS Report | 163535 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : atp pilot : commercial |
| Experience | flight time last 90 days : 250 flight time total : 2500 flight time type : 400 |
| ASRS Report | 163839 |
| Events | |
| Anomaly | aircraft equipment problem : critical other anomaly other |
| Independent Detector | other flight crewa |
| Resolutory Action | flight crew : overcame equipment problem |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
We left den with 2 MEL items, the radio cooling fans and the right pack ground cooling fan inoperative. I thought the right pack was inoperative for an phrases of flight and was using the left pack only. I read the wrong MEL item in the MEL list. The right pack was only inoperative for ground operation only. With 1 pack inoperative the procedure is to fly the aircraft at an altitude not above 17000'. With the overboard valve open for radio cooling, the left pack could not keep the cabin altitude below 10000' at our cruise altitude of 17000'. If I had known the right pack could have been used for flight we would not have had the cabin altitude problem. We called maintenance and told them we had a cabin altitude problem and had us return to den and land. Den maintenance people found some blockage in the right pack duct that they said would have caused the right pack fail even if we had tried to use it. They removed the blockage and replaced the cooling fan with a new fan. The problem with the turn back on my part is that I read and was using the procedure for an inoperative pack and not a ground cooling fan inoperative. If I had read the correct procedure, we may not have had the cabin altitude problem and would not have had to turn back to den for landing. The inoperative sticker on the right pack only said inoperative. It should have said, inoperative ground only to be correct with the placarding of a ground cooling fan. With an inoperative pack the placard should read just 'inoperative.' the wrong placard led me to believe I was operating the aircraft correctly. I should have looked at the MEL # closer. If I had, I would have known the right pack was usable in the air. Supplemental information from acn 163839: the log book stated that the cabin fan was inoperative, not the right pack. I should have checked the log book after the captain.
Original NASA ASRS Text
Title: COMMUTER FLT CREW MISINTERP MINIMUM EQUIPMENT LIST REQUIREMENT.
Narrative: WE LEFT DEN WITH 2 MEL ITEMS, THE RADIO COOLING FANS AND THE RIGHT PACK GND COOLING FAN INOP. I THOUGHT THE RIGHT PACK WAS INOP FOR AN PHRASES OF FLT AND WAS USING THE LEFT PACK ONLY. I READ THE WRONG MEL ITEM IN THE MEL LIST. THE RIGHT PACK WAS ONLY INOP FOR GND OPERATION ONLY. WITH 1 PACK INOP THE PROC IS TO FLY THE ACFT AT AN ALT NOT ABOVE 17000'. WITH THE OVERBOARD VALVE OPEN FOR RADIO COOLING, THE LEFT PACK COULD NOT KEEP THE CABIN ALT BELOW 10000' AT OUR CRUISE ALT OF 17000'. IF I HAD KNOWN THE RIGHT PACK COULD HAVE BEEN USED FOR FLT WE WOULD NOT HAVE HAD THE CABIN ALT PROB. WE CALLED MAINT AND TOLD THEM WE HAD A CABIN ALT PROB AND HAD US RETURN TO DEN AND LAND. DEN MAINT PEOPLE FOUND SOME BLOCKAGE IN THE RIGHT PACK DUCT THAT THEY SAID WOULD HAVE CAUSED THE RIGHT PACK FAIL EVEN IF WE HAD TRIED TO USE IT. THEY REMOVED THE BLOCKAGE AND REPLACED THE COOLING FAN WITH A NEW FAN. THE PROB WITH THE TURN BACK ON MY PART IS THAT I READ AND WAS USING THE PROC FOR AN INOP PACK AND NOT A GND COOLING FAN INOP. IF I HAD READ THE CORRECT PROC, WE MAY NOT HAVE HAD THE CABIN ALT PROB AND WOULD NOT HAVE HAD TO TURN BACK TO DEN FOR LNDG. THE INOP STICKER ON THE RIGHT PACK ONLY SAID INOP. IT SHOULD HAVE SAID, INOP GND ONLY TO BE CORRECT WITH THE PLACARDING OF A GND COOLING FAN. WITH AN INOP PACK THE PLACARD SHOULD READ JUST 'INOP.' THE WRONG PLACARD LED ME TO BELIEVE I WAS OPERATING THE ACFT CORRECTLY. I SHOULD HAVE LOOKED AT THE MEL # CLOSER. IF I HAD, I WOULD HAVE KNOWN THE RIGHT PACK WAS USABLE IN THE AIR. SUPPLEMENTAL INFO FROM ACN 163839: THE LOG BOOK STATED THAT THE CABIN FAN WAS INOP, NOT THE RIGHT PACK. I SHOULD HAVE CHKED THE LOG BOOK AFTER THE CAPT.
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.