Minimum equipment list requirement misinterpreted.

Attributes
ACN	92327
Time
Date	198808
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : sna
State Reference	CA
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport
Navigation In Use	Other
Flight Phase	ground : preflight
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : instrument pilot : flight engineer pilot : commercial
Experience	flight time last 90 days : 200 flight time total : 11000 flight time type : 2300
ASRS Report	92327
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	non adherence : far other anomaly other
Independent Detector	other flight crewa
Resolutory Action	none taken : detected after the fact
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	other

Narrative:

An engine hydraulic pump valve was placed on the MEL by maintenance and two flts were flown in that condition. The engine hydraulic pump valve was inoperative in the open position. We subsequently determined that this specific pump valve should not have been operated inoperative under the MEL and it had been confused with another hydraulic valve with a similar sounding nomenclature. Contributing factors - pressure to maintain schedule, minimize delays, not questioning a maintenance decision, pilot fatigue, 4-DAY trip with long duty days, many flts and minimum rest overnight periods.

Original NASA ASRS Text

Title: MINIMUM EQUIPMENT LIST REQUIREMENT MISINTERPRETED.

Narrative: AN ENG HYD PUMP VALVE WAS PLACED ON THE MEL BY MAINT AND TWO FLTS WERE FLOWN IN THAT CONDITION. THE ENG HYD PUMP VALVE WAS INOPERATIVE IN THE OPEN POS. WE SUBSEQUENTLY DETERMINED THAT THIS SPECIFIC PUMP VALVE SHOULD NOT HAVE BEEN OPERATED INOPERATIVE UNDER THE MEL AND IT HAD BEEN CONFUSED WITH ANOTHER HYD VALVE WITH A SIMILAR SOUNDING NOMENCLATURE. CONTRIBUTING FACTORS - PRESSURE TO MAINTAIN SCHEDULE, MINIMIZE DELAYS, NOT QUESTIONING A MAINT DECISION, PLT FATIGUE, 4-DAY TRIP WITH LONG DUTY DAYS, MANY FLTS AND MINIMUM REST OVERNIGHT PERIODS.

Data retrieved from NASA's ASRS site as of August 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.