Multiple aircraft equipment problems confuses flight crew ground crew as to the legality of the MEL ...

Attributes
ACN	357929
Time
Date	199701
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : sea
State Reference	WA
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : atl
Operator	common carrier : air carrier
Make Model Name	B737-400
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	climbout : takeoff cruise other ground : preflight
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : instrument pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 200 flight time total : 11000 flight time type : 1800
ASRS Report	357929
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : less severe non adherence : published procedure non adherence : far other anomaly other
Independent Detector	other flight crewa
Resolutory Action	aircraft : equipment problem dissipated other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation other
Situations
Publication	Unspecified

Narrative:

Part 121 dispatch release showed 2 MEL items: APU inoperative and engine #2 N2 tachometer gauge inoperative. APU was MEL'ed on saturday, #2 N2 gauge MEL'ed on monday. We accepted the airplane on jan/tue/97, and complied with all procedures to operate the airplane safely. While en route on our first leg with the airplane we reviewed all procedures again and discovered that the 2 mels conflict because: APU inoperative requires engine #1 start at gate from external air, engine #2 start xbleed after pushback. #2 N2 inoperative special procedure requires both engines be started from same air source. We inadvertently operated the aircraft with this conflict due to the lack of any xrefed 'conflict alert' and a preponderance of operational steps listed in the special procedure for operating with an N2 gauge inoperative. The inbound crew advised us that the N2 indicator that was MEL'ed operated normally and we confirmed its normal operation during our start and throughout our entire first leg. We resolved the conflict at our first en route stop by alerting maintenance of the conflict and having them clear the #2 N2 gauge MEL item. The MEL book is full of these conflicts. Pilots should not have to proofread approved documents for obvious conflicts and maintenance and dispatch should not have released the airplane on jan/mon/97, when the second MEL developed. Of course pilots must always consider interrelationships before accepting multiple mels. In this case pilots caught the conflict after about 1 day of operation and before maintenance or dispatch! Contributing factor for this situation is that with an APU inoperative the B737-400 flight handbook precludes starting both engines at the gate unless the ramp/taxiway is too slippery for a xbleed start. This is because an air start at gate of both engines subjects the ground crew to unreasonable engine inlet risk and is only a last resort. This information is in the B737-400 flight handbook, something that maintenance or dispatch would not refer to normally.

Original NASA ASRS Text

Title: MULTIPLE ACFT EQUIP PROBS CONFUSES FLC GND CREW AS TO THE LEGALITY OF THE MEL REQUIREMENTS VERSUS THE LOGBOOK WRITE-UP AND DISPATCH RELEASE. ACFT OPERATED UNDER INCORRECT ASSUMPTIONS.

Narrative: PART 121 DISPATCH RELEASE SHOWED 2 MEL ITEMS: APU INOP AND ENG #2 N2 TACHOMETER GAUGE INOP. APU WAS MEL'ED ON SATURDAY, #2 N2 GAUGE MEL'ED ON MONDAY. WE ACCEPTED THE AIRPLANE ON JAN/TUE/97, AND COMPLIED WITH ALL PROCS TO OPERATE THE AIRPLANE SAFELY. WHILE ENRTE ON OUR FIRST LEG WITH THE AIRPLANE WE REVIEWED ALL PROCS AGAIN AND DISCOVERED THAT THE 2 MELS CONFLICT BECAUSE: APU INOP REQUIRES ENG #1 START AT GATE FROM EXTERNAL AIR, ENG #2 START XBLEED AFTER PUSHBACK. #2 N2 INOP SPECIAL PROC REQUIRES BOTH ENGS BE STARTED FROM SAME AIR SOURCE. WE INADVERTENTLY OPERATED THE ACFT WITH THIS CONFLICT DUE TO THE LACK OF ANY XREFED 'CONFLICT ALERT' AND A PREPONDERANCE OF OPERATIONAL STEPS LISTED IN THE SPECIAL PROC FOR OPERATING WITH AN N2 GAUGE INOP. THE INBOUND CREW ADVISED US THAT THE N2 INDICATOR THAT WAS MEL'ED OPERATED NORMALLY AND WE CONFIRMED ITS NORMAL OP DURING OUR START AND THROUGHOUT OUR ENTIRE FIRST LEG. WE RESOLVED THE CONFLICT AT OUR FIRST ENRTE STOP BY ALERTING MAINT OF THE CONFLICT AND HAVING THEM CLR THE #2 N2 GAUGE MEL ITEM. THE MEL BOOK IS FULL OF THESE CONFLICTS. PLTS SHOULD NOT HAVE TO PROOFREAD APPROVED DOCUMENTS FOR OBVIOUS CONFLICTS AND MAINT AND DISPATCH SHOULD NOT HAVE RELEASED THE AIRPLANE ON JAN/MON/97, WHEN THE SECOND MEL DEVELOPED. OF COURSE PLTS MUST ALWAYS CONSIDER INTERRELATIONSHIPS BEFORE ACCEPTING MULTIPLE MELS. IN THIS CASE PLTS CAUGHT THE CONFLICT AFTER ABOUT 1 DAY OF OP AND BEFORE MAINT OR DISPATCH! CONTRIBUTING FACTOR FOR THIS SIT IS THAT WITH AN APU INOP THE B737-400 FLT HANDBOOK PRECLUDES STARTING BOTH ENGS AT THE GATE UNLESS THE RAMP/TXWY IS TOO SLIPPERY FOR A XBLEED START. THIS IS BECAUSE AN AIR START AT GATE OF BOTH ENGS SUBJECTS THE GND CREW TO UNREASONABLE ENG INLET RISK AND IS ONLY A LAST RESORT. THIS INFO IS IN THE B737-400 FLT HANDBOOK, SOMETHING THAT MAINT OR DISPATCH WOULD NOT REFER TO NORMALLY.

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.

Multiple aircraft equipment problems confuses flight crew ground crew as to the legality of the MEL requirements versus the logbook write-up and dispatch release. Aircraft operated under incorrect assumptions.