Narrative:

In cruise; I noticed the fuel temperature gauge (left side of the gauge -- #1 side) was reading nothing (below the -45 hash mark). I called maintenance control and explained what I saw on the gauge that shows a #1 side and a #2 side in regards to fuel temperature. There was some confusion initially as to whether it was the fuel tank temperature gauge on the left side of the instrument panel (of which there is only one for the left tank) or if it was the fuel temperature gauge which has a reading for the #1 side and the #2 side on 1 single gauge located on the right side of the instrument panel under the landing gear handle. The problem was with the gauge with the readings for #1 and #2 -- the #1 side was indicating nothing. To clear up the confusion; I used the phraseology of; 'the gauge under the landing gear handle on the right side of the instrument panel.' maintenance seemed to be clear at this point. I next had to call my dispatcher to devise a plan as to either continue on to the destination or to go somewhere else -- we collectively decided to continue on to the destination. Before we terminated communication; I made sure to ask maintenance and dispatch to get a hold of the local mechanic so he/she could meet us on arrival. We landed and deplaned in ZZZZ without incident. I next called dispatch to see if we could expect maintenance and was told that we can MEL the gauge over the phone with maintenance direction. I called maintenance and clarified the gauge once again and was told we could MEL the gauge; so we did. I then called dispatch to amend my release for flight back to ZZZ; due to the MEL being a dispatch advise item; and then departed and landed in ZZZ without incident. My crew and I had an equipment change in ZZZ and went on with the rest of our day. After our day was over; I found out that the gauge that was MEL'ed was not an MEL-able item. I immediately called maintenance control on the phone and asked about it (by this time it was a different maintenance controller); and was told that indeed we MEL'ed an item that was not MEL-able. At that instance; I realized that there was a gross miscom between me and the original maintenance controller; and even though I thought that I repeatedly clarified the gauge; it didn't work. Another contributing factor was the MEL reference with 2 similar; but very different gauges. I contacted my duty officer and disclosed the whole experience with him and then I filled out the required irregularity form and faxed him a copy. Callback conversation with reporter revealed the following information: reporter stated the right wing tank does not have any tank temperature gauge. The left wing temperature gage is the only reference for wing fuel tank temperature. Although maintenance control gave him the ok for the deferral over the phone; and they departed; the MEL was not legal; as he found out later. Reporter also stated; although they carry their MEL manual onboard; the MEL shows only one fuel temperature gage installed and '0' required. The MEL did not discriminate; or differentiate; the left wing fuel tank temperature from the engine fuel temperature gauge which is a dual reading; but single gauge. After a review of their MEL manual; his chief pilot informed him the company would be revising the MEL procedures language to address this discrepancy.

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Original NASA ASRS Text

Title: A BOMBARDIER DE HAVILLAND DHC-8-200 ACFT WAS DISPATCHED UNDER A MAINT MEL DEFERRAL WITH A FUEL TEMP GAUGE READING NOTHING. MEL WAS NOT LEGAL.

Narrative: IN CRUISE; I NOTICED THE FUEL TEMP GAUGE (L SIDE OF THE GAUGE -- #1 SIDE) WAS READING NOTHING (BELOW THE -45 HASH MARK). I CALLED MAINT CTL AND EXPLAINED WHAT I SAW ON THE GAUGE THAT SHOWS A #1 SIDE AND A #2 SIDE IN REGARDS TO FUEL TEMP. THERE WAS SOME CONFUSION INITIALLY AS TO WHETHER IT WAS THE FUEL TANK TEMP GAUGE ON THE L SIDE OF THE INST PANEL (OF WHICH THERE IS ONLY ONE FOR THE L TANK) OR IF IT WAS THE FUEL TEMP GAUGE WHICH HAS A READING FOR THE #1 SIDE AND THE #2 SIDE ON 1 SINGLE GAUGE LOCATED ON THE R SIDE OF THE INST PANEL UNDER THE LNDG GEAR HANDLE. THE PROB WAS WITH THE GAUGE WITH THE READINGS FOR #1 AND #2 -- THE #1 SIDE WAS INDICATING NOTHING. TO CLR UP THE CONFUSION; I USED THE PHRASEOLOGY OF; 'THE GAUGE UNDER THE LNDG GEAR HANDLE ON THE R SIDE OF THE INST PANEL.' MAINT SEEMED TO BE CLR AT THIS POINT. I NEXT HAD TO CALL MY DISPATCHER TO DEVISE A PLAN AS TO EITHER CONTINUE ON TO THE DEST OR TO GO SOMEWHERE ELSE -- WE COLLECTIVELY DECIDED TO CONTINUE ON TO THE DEST. BEFORE WE TERMINATED COM; I MADE SURE TO ASK MAINT AND DISPATCH TO GET A HOLD OF THE LCL MECH SO HE/SHE COULD MEET US ON ARR. WE LANDED AND DEPLANED IN ZZZZ WITHOUT INCIDENT. I NEXT CALLED DISPATCH TO SEE IF WE COULD EXPECT MAINT AND WAS TOLD THAT WE CAN MEL THE GAUGE OVER THE PHONE WITH MAINT DIRECTION. I CALLED MAINT AND CLARIFIED THE GAUGE ONCE AGAIN AND WAS TOLD WE COULD MEL THE GAUGE; SO WE DID. I THEN CALLED DISPATCH TO AMEND MY RELEASE FOR FLT BACK TO ZZZ; DUE TO THE MEL BEING A DISPATCH ADVISE ITEM; AND THEN DEPARTED AND LANDED IN ZZZ WITHOUT INCIDENT. MY CREW AND I HAD AN EQUIP CHANGE IN ZZZ AND WENT ON WITH THE REST OF OUR DAY. AFTER OUR DAY WAS OVER; I FOUND OUT THAT THE GAUGE THAT WAS MEL'ED WAS NOT AN MEL-ABLE ITEM. I IMMEDIATELY CALLED MAINT CTL ON THE PHONE AND ASKED ABOUT IT (BY THIS TIME IT WAS A DIFFERENT MAINT CTLR); AND WAS TOLD THAT INDEED WE MEL'ED AN ITEM THAT WAS NOT MEL-ABLE. AT THAT INSTANCE; I REALIZED THAT THERE WAS A GROSS MISCOM BTWN ME AND THE ORIGINAL MAINT CTLR; AND EVEN THOUGH I THOUGHT THAT I REPEATEDLY CLARIFIED THE GAUGE; IT DIDN'T WORK. ANOTHER CONTRIBUTING FACTOR WAS THE MEL REF WITH 2 SIMILAR; BUT VERY DIFFERENT GAUGES. I CONTACTED MY DUTY OFFICER AND DISCLOSED THE WHOLE EXPERIENCE WITH HIM AND THEN I FILLED OUT THE REQUIRED IRREGULARITY FORM AND FAXED HIM A COPY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED THE RIGHT WING TANK DOES NOT HAVE ANY TANK TEMP GAUGE. THE LEFT WING TEMP GAGE IS THE ONLY REFERENCE FOR WING FUEL TANK TEMP. ALTHOUGH MAINT CONTROL GAVE HIM THE OK FOR THE DEFERRAL OVER THE PHONE; AND THEY DEPARTED; THE MEL WAS NOT LEGAL; AS HE FOUND OUT LATER. REPORTER ALSO STATED; ALTHOUGH THEY CARRY THEIR MEL MANUAL ONBOARD; THE MEL SHOWS ONLY ONE FUEL TEMP GAGE INSTALLED AND '0' REQUIRED. THE MEL DID NOT DISCRIMINATE; OR DIFFERENTIATE; THE LEFT WING FUEL TANK TEMP FROM THE ENGINE FUEL TEMP GAUGE WHICH IS A DUAL READING; BUT SINGLE GAUGE. AFTER A REVIEW OF THEIR MEL MANUAL; HIS CHIEF PILOT INFORMED HIM THE COMPANY WOULD BE REVISING THE MEL PROCEDURES LANGUAGE TO ADDRESS THIS DISCREPANCY.

Data retrieved from NASA's ASRS site as of January 2009 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.