Minimum equipment list confusion.

Attributes
ACN	137872
Time
Date	199002
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : ewr
State Reference	NJ
Altitude	agl bound lower : 0 agl bound upper : 0
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	ground : preflight
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 173 flight time total : 10300 flight time type : 3200
ASRS Report	137872
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	non adherence : far other anomaly other
Independent Detector	other flight crewa other other : unspecified
Resolutory Action	none taken : detected after the fact
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

In bos out station, #1 generator was inoperative due to phase reversal. Aircraft air crew wrote in logbook that #1 generator would not automatic parallel. This is normal due to bus protection. Maintenance in bos MEL'ed #1 generator automatic parallel inoperative. On placard maintenance stated manual paralleling 'ok' on #1 generator. I do not believe this was accomplished. Flew bos to ewr -- how this was accomplished we cannot guess. The aircraft generator in ewr was then written up as not being able to parallel on bus tie by automatic or manual means. MEL xa was issued by ewr maintenance which should have been done initially, but maintenance did not remove incorrect automatic paralleling MEL xb. These 2 MEL's are in conflict. MEL xb requires 3 operating generators. Whenever a generator is inoperative (MEL xa), it is impossible to parallel. Aircraft then flew from ewr to mlb and returned to ewr. We obtained the aircraft in ewr. We reviewed the logbook and discussed that the first write-up and MEL were incorrect and that the second MEL appeared to correct the situation. This is where we made our mistake. We failed to examine the MEL book. We had all flown numerous times with inoperative generators and everything was normal except MEL xb. We assumed maintenance failed to remove MEL xb for some administrative purpose. We flew to tpa. Dispatch requested a call from us and notified us of the conflicting MEL's. We had tpa maintenance remove MEL xb.

Original NASA ASRS Text

Title: MINIMUM EQUIPMENT LIST CONFUSION.

Narrative: IN BOS OUT STATION, #1 GENERATOR WAS INOP DUE TO PHASE REVERSAL. ACFT AIR CREW WROTE IN LOGBOOK THAT #1 GENERATOR WOULD NOT AUTO PARALLEL. THIS IS NORMAL DUE TO BUS PROTECTION. MAINT IN BOS MEL'ED #1 GENERATOR AUTO PARALLEL INOP. ON PLACARD MAINT STATED MANUAL PARALLELING 'OK' ON #1 GENERATOR. I DO NOT BELIEVE THIS WAS ACCOMPLISHED. FLEW BOS TO EWR -- HOW THIS WAS ACCOMPLISHED WE CANNOT GUESS. THE ACFT GENERATOR IN EWR WAS THEN WRITTEN UP AS NOT BEING ABLE TO PARALLEL ON BUS TIE BY AUTO OR MANUAL MEANS. MEL XA WAS ISSUED BY EWR MAINT WHICH SHOULD HAVE BEEN DONE INITIALLY, BUT MAINT DID NOT REMOVE INCORRECT AUTO PARALLELING MEL XB. THESE 2 MEL'S ARE IN CONFLICT. MEL XB REQUIRES 3 OPERATING GENERATORS. WHENEVER A GENERATOR IS INOP (MEL XA), IT IS IMPOSSIBLE TO PARALLEL. ACFT THEN FLEW FROM EWR TO MLB AND RETURNED TO EWR. WE OBTAINED THE ACFT IN EWR. WE REVIEWED THE LOGBOOK AND DISCUSSED THAT THE FIRST WRITE-UP AND MEL WERE INCORRECT AND THAT THE SECOND MEL APPEARED TO CORRECT THE SITUATION. THIS IS WHERE WE MADE OUR MISTAKE. WE FAILED TO EXAMINE THE MEL BOOK. WE HAD ALL FLOWN NUMEROUS TIMES WITH INOP GENERATORS AND EVERYTHING WAS NORMAL EXCEPT MEL XB. WE ASSUMED MAINT FAILED TO REMOVE MEL XB FOR SOME ADMINISTRATIVE PURPOSE. WE FLEW TO TPA. DISPATCH REQUESTED A CALL FROM US AND NOTIFIED US OF THE CONFLICTING MEL'S. WE HAD TPA MAINT REMOVE MEL XB.

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.