Air carrier PIC stated confusion re use of inoperative aircraft equipment.

Attributes
ACN	261555
Time
Date	199401
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : bwi
State Reference	MD
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	A320
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	climbout : takeoff ground : preflight landing other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 110 flight time total : 7800 flight time type : 1200
ASRS Report	261555
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe non adherence : far non adherence : published procedure other anomaly other
Independent Detector	other flight crewa
Resolutory Action	none taken : anomaly accepted
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation
Situations
Publication	Unspecified

Narrative:

On preflight aircraft had a flight control computer that was inoperative. Maintenance replaced the faulty computer. During maintenance test of aircraft's autoland capabilities the mechanic couldn't get a proper indication from the autothrust system and as a result decided to placard the autothrust system inoperative and dispatch the aircraft under my company's MEL. On takeoff the autothrust activated automatically as was normal. I decided to leave the autothrust system on and it functioned normally throughout the entire flight. Landing at destination was visual. I had closely watched the mechanic during all his testing of the system and felt that inasmuch as we never got any self- detected faults of the system during the testing that the autothrust system would function normally when used in 'normal' operation. The mechanic agreed. We also ended up flying the aircraft with no passenger and no revenue cargo aboard since our flight had canceled. The problem here is that our MEL, while it definitely advises us when to not use a system, doesn't tell us when we may use an inoperative system. Recommendation: all MEL's should be very clear when an inoperative system may be used vs when it may not.

Original NASA ASRS Text

Title: ACR PIC STATED CONFUSION RE USE OF INOP ACFT EQUIP.

Narrative: ON PREFLT ACFT HAD A FLT CTL COMPUTER THAT WAS INOP. MAINT REPLACED THE FAULTY COMPUTER. DURING MAINT TEST OF ACFT'S AUTOLAND CAPABILITIES THE MECH COULDN'T GET A PROPER INDICATION FROM THE AUTOTHRUST SYS AND AS A RESULT DECIDED TO PLACARD THE AUTOTHRUST SYS INOP AND DISPATCH THE ACFT UNDER MY COMPANY'S MEL. ON TKOF THE AUTOTHRUST ACTIVATED AUTOMATICALLY AS WAS NORMAL. I DECIDED TO LEAVE THE AUTOTHRUST SYS ON AND IT FUNCTIONED NORMALLY THROUGHOUT THE ENTIRE FLT. LNDG AT DEST WAS VISUAL. I HAD CLOSELY WATCHED THE MECH DURING ALL HIS TESTING OF THE SYS AND FELT THAT INASMUCH AS WE NEVER GOT ANY SELF- DETECTED FAULTS OF THE SYS DURING THE TESTING THAT THE AUTOTHRUST SYS WOULD FUNCTION NORMALLY WHEN USED IN 'NORMAL' OP. THE MECH AGREED. WE ALSO ENDED UP FLYING THE ACFT WITH NO PAX AND NO REVENUE CARGO ABOARD SINCE OUR FLT HAD CANCELED. THE PROB HERE IS THAT OUR MEL, WHILE IT DEFINITELY ADVISES US WHEN TO NOT USE A SYS, DOESN'T TELL US WHEN WE MAY USE AN INOP SYS. RECOMMENDATION: ALL MEL'S SHOULD BE VERY CLEAR WHEN AN INOP SYSTEM MAY BE USED VS WHEN IT MAY NOT.

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.