Narrative:

The previous night; I flew this aircraft into ZZZ from ZZZ1 and had the rad altitude 1 fail in flight. Upon landing; I contacted maintenance and deferred the item in accordance with MEL before going to the hotel. The maintenance action required for this MEL says to pull and collar cbs D14; D21; the GPWS circuit breaker and the TCAS (J6 or D3... J6 in this case). It also requires that the GPWS and TCAS be deferred in accordance with mels. All this was accomplished. This day; I showed up for the flight and found it was same aircraft but the TCAS deferral had been cleared at some point during the day. When I called maintenance for clarification they told me it was not necessary since only one RA was deferred. I agreed that only one was deferred but pointed out that the maintenance action does not differentiate between the numbers of RA's deferred. It merely says to do those actions. The maintenance rep advised me to call my flight manager which I did. The FM told me that he would make some calls and to stand by. He called me back after about 15 minutes and told me it was resolved and that I should call maintenance. When I did; they still insisted it was good as is. At this point I talked to dispatch and told them I could not depart until the TCAS was deferred. I heard that they put in a call to the director of flight operations but never did hear what he said. After about an hour delay; dispatch called me back and agreed to defer the TCAS. We re-deferred that TCAS and departed. At least one and possibly three flts went with the TCAS not deferred. Log was reviewed before flight. The issue was resolved when they agreed to defer the TCAS. The MEL procedure is extremely vague and poorly written. In the description; it says that the TCAS need not be considered inoperative if only one RA is deferred but then the maintenance action requires you to defer the TCAS regardless of the number of RA's deferred. If the intent is to allow TCAS operation it should say so in the maintenance action. The MEL really needs to be rewritten. I was really unhappy to have to delay a flight merely to make it less safe by rendering an otherwise operable system inoperable. However; the wording of the MEL left me no choice if I wanted to fly legally. The TCAS did in fact work just fine and it is obviously a critically important instrument for flight safety. Please fix the MEL.

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Original NASA ASRS Text

Title: PLT OF AN EMB-145LR (ERJ-145LR) WITH A RADIO ALTIMETER (1 OF 2) FAILURE IN FLT; RPTS THE MEL PROC IS EXTREMELY VAGUE AND POORLY WRITTEN AND CONFLICTS WITH THE MAINT PROC REGARDING THE REQUIREMENT TO ALSO DEACTIVATE A FUNCTIONING TCAS AND GPWS SYSTEM.

Narrative: THE PREVIOUS NIGHT; I FLEW THIS ACFT INTO ZZZ FROM ZZZ1 AND HAD THE RAD ALT 1 FAIL IN FLT. UPON LNDG; I CONTACTED MAINT AND DEFERRED THE ITEM IAW MEL BEFORE GOING TO THE HOTEL. THE MAINT ACTION REQUIRED FOR THIS MEL SAYS TO PULL AND COLLAR CBS D14; D21; THE GPWS CB AND THE TCAS (J6 OR D3... J6 IN THIS CASE). IT ALSO REQUIRES THAT THE GPWS AND TCAS BE DEFERRED IAW MELS. ALL THIS WAS ACCOMPLISHED. THIS DAY; I SHOWED UP FOR THE FLT AND FOUND IT WAS SAME ACFT BUT THE TCAS DEFERRAL HAD BEEN CLEARED AT SOME POINT DURING THE DAY. WHEN I CALLED MAINT FOR CLARIFICATION THEY TOLD ME IT WAS NOT NECESSARY SINCE ONLY ONE RA WAS DEFERRED. I AGREED THAT ONLY ONE WAS DEFERRED BUT POINTED OUT THAT THE MAINT ACTION DOES NOT DIFFERENTIATE BETWEEN THE NUMBERS OF RA'S DEFERRED. IT MERELY SAYS TO DO THOSE ACTIONS. THE MAINT REP ADVISED ME TO CALL MY FLT MGR WHICH I DID. THE FM TOLD ME THAT HE WOULD MAKE SOME CALLS AND TO STAND BY. HE CALLED ME BACK AFTER ABOUT 15 MINUTES AND TOLD ME IT WAS RESOLVED AND THAT I SHOULD CALL MAINT. WHEN I DID; THEY STILL INSISTED IT WAS GOOD AS IS. AT THIS POINT I TALKED TO DISPATCH AND TOLD THEM I COULD NOT DEPART UNTIL THE TCAS WAS DEFERRED. I HEARD THAT THEY PUT IN A CALL TO THE DIRECTOR OF FLT OPS BUT NEVER DID HEAR WHAT HE SAID. AFTER ABOUT AN HOUR DELAY; DISPATCH CALLED ME BACK AND AGREED TO DEFER THE TCAS. WE RE-DEFERRED THAT TCAS AND DEPARTED. AT LEAST ONE AND POSSIBLY THREE FLTS WENT WITH THE TCAS NOT DEFERRED. LOG WAS REVIEWED BEFORE FLT. THE ISSUE WAS RESOLVED WHEN THEY AGREED TO DEFER THE TCAS. THE MEL PROC IS EXTREMELY VAGUE AND POORLY WRITTEN. IN THE DESCRIPTION; IT SAYS THAT THE TCAS NEED NOT BE CONSIDERED INOP IF ONLY ONE RA IS DEFERRED BUT THEN THE MAINT ACTION REQUIRES YOU TO DEFER THE TCAS REGARDLESS OF THE NUMBER OF RA'S DEFERRED. IF THE INTENT IS TO ALLOW TCAS OPERATION IT SHOULD SAY SO IN THE MAINT ACTION. THE MEL REALLY NEEDS TO BE REWRITTEN. I WAS REALLY UNHAPPY TO HAVE TO DELAY A FLT MERELY TO MAKE IT LESS SAFE BY RENDERING AN OTHERWISE OPERABLE SYSTEM INOPERABLE. HOWEVER; THE WORDING OF THE MEL LEFT ME NO CHOICE IF I WANTED TO FLY LEGALLY. THE TCAS DID IN FACT WORK JUST FINE AND IT IS OBVIOUSLY A CRITICALLY IMPORTANT INSTRUMENT FOR FLT SAFETY. PLEASE FIX THE MEL.

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