chikhba

you have to understand first that there is 2 autopilots command CMD A and CMD B ,each one is considered as a channel so how this work in approach procedures ? we assume that you have set both ILS frequencies and courses and you are not below 1500 feet RA and about 30 degree intercept heading ;now push the approach button on MCP,than push CMD B now you will see both VOR/LOC and G/S are armed on FMA (flight mode annunciator) until now the AFDS shows CMD in green.When the LOC is captured FMA shows VOR/LOC in green and the AFDS switches from CMD to SINGLE CH this tell you that only one autopilot is engaged until now .When both VOR/LOC and G/S are engaged SINGLE CH will switch to CMD again when airplane reaches an altitude below 1500 RA this tell you that the second autopilot is engaged now you can see also that FLARE mode is armed which will engage at 50 RA approximately. let me know if you have other question; have a good flight.