AC 120-55C Air Carrier TCAS - Code7700

2/23/11 AC 120-55CAppendix 3APPENDIX 3. TCAS MEL AND MMEL PROVISIONS1. DISPATCHING WITH MEL PROVISIONS. Each operator with authority to dispatch anaircraft with a TCAS system or component temporarily inoperative must do so in accordancewith provisions of a MEL. MELs are approved for each operator and type of aircraft, withinprovisions of the FAA MMEL for that type. When proposed MEL provisions are consistent withthe FAA MMEL, POIs may approve the MEL. If requesting a less restrictive MEL or differentMEL provisions, forward a proposal for consideration of an FAA MMEL change to the AEGassigned for that aircraft type. No relief will be granted for the voice command portion of theTCAS system when functioning in the TA-only mode. The audio will be provided via a speaker,which may also service windshear and ground proximity equipment. Enhanced features(those above and beyond the basic TCAS system) may be inoperative provided that theinoperative features do not degrade the system (for example, flight level traffic altitude selectionfeature for a traffic display).2. BACKGROUND. The intent of the provisos and repair category intervals was to grant theoperator sufficient relief, especially during the early stage of the TCAS transition, in order topromote the installation process, as well as support the use of a practical system. Both equipmentreliability and operational experience dictated whether any revision to the MMEL relief wasconsidered.3. REVISIONS. The original Policy Letter 32 in the automated MMEL system outlined policyfor TCAS II. On April 6, 2002 MMEL Policy Letter 32, revision 5 was issued as updatedguidance to the FOEB for standardized MMEL relief for the TCAS. The most significant changein revision 5 is to change the relief category from C to B for the entire system when required by14 CFR.4. EXAMPLES. The following list is the standard set of provisos for all aircraft for which onegrants relief for the TCAS I and II systems and it is extracted from MMEL Policy Letter 32,revision 7, dated July 7, 2006:Page 1