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.

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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.