B757-200
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Maintenance
General Flight Cancelled / Delayed; General Maintenance Action
Procedure; MEL; Aircraft; Company Policy
We went to Aircraft X to further review deferrals. We found 2 deferrals on the Mode Control Panel. The MELs described LNAV; VNAV; HDG HOLD; FLT CH; ALT HOLD; VS; all possibly affected by the MELs. I asked the mechanic to have someone come out and describe what we'll have available after departure. I called Flight Control and asked if we were RVSM legal. I was told we can't fly the SID; that we would have to get direct all the way to ZZZ. This very degraded state was concerning to the First Officer and me especially with the winter storm warnings at our destination. We were also told that the aircraft would not be legal to return to ZZZ1 with deferrals. We were also concerned about having an inflight emergency and diverting to an airport with only RNAV approaches available as we weren't capable of that approach. After discussions with Maintenance Supervisor; Flight Control and the Assistant Chief Pilot someone decided to tail swap the trip.
Pilot reported misgivings from degraded navigation systems place on MEL and obtained an aircraft tail swap to complete the flight