Narrative:

On may/xx/96, I was in command of a DC9-32 (mcdonnell douglas) from XXX to ZZZ and back to XXX. During the descent into lax, the N1 tach gauge failed on the left engine. The airplane was configured with mixed engines, pvwjt-9 dash 7 on the left and a dash 9 on the right. Upon arriving in lax, I referred to the MEL and conferred by phone with the maintenance controller in mke. We determined the applicable dmi number and filed the left N1 tach gauge as deferred, the flight proceeded to XXX from ZZZ normally. Upon arriving in oma, it was learned that deferring the N1 tach gauge was improper due to the intermixed engine confign. According to maintenance control, in the future whenever an MEL item or a dmi (deferred maintenance) item conflicts with a procedure in maintenance computer program, a programmed flag or alert will be raised. It has been emphasized now in my mind the importance of more thoroughly examining everything available in the MEL involving a dmi before jumping to conclusions.

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Original NASA ASRS Text

Title: AN N1 GAUGE FAILED, WAS PLACARDED INOP AND DEFERRED. WITH A MIX OF ENGS JT8D-7 AND JT8D-9, THE N1 GAUGE IS NOT DEFERRABLE. MAINT CTLR ENTERED A WRONG MEL NUMBER SO THE MISTAKE WASN'T FOUND UNTIL AFTER THE ACFT HAD FLOWN ANOTHER LEG.

Narrative: ON MAY/XX/96, I WAS IN COMMAND OF A DC9-32 (MCDONNELL DOUGLAS) FROM XXX TO ZZZ AND BACK TO XXX. DURING THE DSCNT INTO LAX, THE N1 TACH GAUGE FAILED ON THE L ENG. THE AIRPLANE WAS CONFIGURED WITH MIXED ENGS, PVWJT-9 DASH 7 ON THE L AND A DASH 9 ON THE R. UPON ARRIVING IN LAX, I REFERRED TO THE MEL AND CONFERRED BY PHONE WITH THE MAINT CTLR IN MKE. WE DETERMINED THE APPLICABLE DMI NUMBER AND FILED THE L N1 TACH GAUGE AS DEFERRED, THE FLT PROCEEDED TO XXX FROM ZZZ NORMALLY. UPON ARRIVING IN OMA, IT WAS LEARNED THAT DEFERRING THE N1 TACH GAUGE WAS IMPROPER DUE TO THE INTERMIXED ENG CONFIGN. ACCORDING TO MAINT CTL, IN THE FUTURE WHENEVER AN MEL ITEM OR A DMI (DEFERRED MAINT) ITEM CONFLICTS WITH A PROC IN MAINT COMPUTER PROGRAM, A PROGRAMMED FLAG OR ALERT WILL BE RAISED. IT HAS BEEN EMPHASIZED NOW IN MY MIND THE IMPORTANCE OF MORE THOROUGHLY EXAMINING EVERYTHING AVAILABLE IN THE MEL INVOLVING A DMI BEFORE JUMPING TO CONCLUSIONS.

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.