A B737-300 in climb at 8000 ft returned to the field due to failure of the left air-conditioning pack and with the mistaken impression the right air-conditioning pack was also deferred inoperative.

Home

Browse by month

Random

Latest

About

Contact

Attributes
ACN	404074
Time
Date	199806
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : pit
State Reference	PA
Altitude	msl bound lower : 8000 msl bound upper : 8000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : pit
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	climbout : intermediate altitude other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : flight engineer pilot : instrument pilot : cfi
Experience	flight time last 90 days : 150 flight time total : 13000 flight time type : 7000
ASRS Report	404074
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : critical non adherence : far non adherence : published procedure
Independent Detector	other flight crewa
Resolutory Action	other
Consequence	Other
Supplementary
Air Traffic Incident	other

Narrative:

Aircraft had 2 mels. One related to a purge valve on the right air-conditioning pack. Maintenance had placed an 'inoperative' placard next to the right pack switch in the cockpit. After reviewing the MEL, we were led to believe that the right pack was inoperative and verified that the flight was filed at 25000 ft for single pack operation. After takeoff, the remaining operative pack failed. This resulted in a loss of cabin pressurization and necessitated a return to the departure airport. After returning to the gate, maintenance informed me that the MEL on the right pack only pertained to a maintenance function and that the pack should have been operated normally. Had this been the case, the flight could have continued to its destination with the subsequent in-flight failure. This occurrence was a result of a vague MEL that, unlike the majority, had no operational effect on the system. Obviously, it would be helpful if maintenance could either refrain from placing an 'inoperative' placard on a normally functioning system, or provide an annotation to the MEL stating that the inoperative component does not affect the flight crew.

Original NASA ASRS Text

Title: A B737-300 IN CLB AT 8000 FT RETURNED TO THE FIELD DUE TO FAILURE OF THE L AIR-CONDITIONING PACK AND WITH THE MISTAKEN IMPRESSION THE R AIR-CONDITIONING PACK WAS ALSO DEFERRED INOP.

Narrative: ACFT HAD 2 MELS. ONE RELATED TO A PURGE VALVE ON THE R AIR-CONDITIONING PACK. MAINT HAD PLACED AN 'INOP' PLACARD NEXT TO THE R PACK SWITCH IN THE COCKPIT. AFTER REVIEWING THE MEL, WE WERE LED TO BELIEVE THAT THE R PACK WAS INOP AND VERIFIED THAT THE FLT WAS FILED AT 25000 FT FOR SINGLE PACK OP. AFTER TKOF, THE REMAINING OPERATIVE PACK FAILED. THIS RESULTED IN A LOSS OF CABIN PRESSURIZATION AND NECESSITATED A RETURN TO THE DEP ARPT. AFTER RETURNING TO THE GATE, MAINT INFORMED ME THAT THE MEL ON THE R PACK ONLY PERTAINED TO A MAINT FUNCTION AND THAT THE PACK SHOULD HAVE BEEN OPERATED NORMALLY. HAD THIS BEEN THE CASE, THE FLT COULD HAVE CONTINUED TO ITS DEST WITH THE SUBSEQUENT INFLT FAILURE. THIS OCCURRENCE WAS A RESULT OF A VAGUE MEL THAT, UNLIKE THE MAJORITY, HAD NO OPERATIONAL EFFECT ON THE SYS. OBVIOUSLY, IT WOULD BE HELPFUL IF MAINT COULD EITHER REFRAIN FROM PLACING AN 'INOP' PLACARD ON A NORMALLY FUNCTIONING SYS, OR PROVIDE AN ANNOTATION TO THE MEL STATING THAT THE INOP COMPONENT DOES NOT AFFECT THE FLC.

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.