[2] The A/T operates over the full flight regime, from takeoff through touchdown. The A/T and DFCS work together to maintain the airplane's flight profile. The DFCS system normally selects the A/T mode. If the DFCS is off ,the pilot can select the desired autothrottle mode. During the initial takeoff roll, the A/T controls thrust (N1), then holds that thrust untill reaching a safe altitude. When climbing, the DFCS normally maintains the airspeed and the A/T maintains the thrust. During cruise, the A/T maintains the airspeed while the DFCS maintains the altitude. When descending, the throttles normally return to the aft stop and the DFCS maintains the airspeed if LVL CHG or vertical path is selected. During the approach the DFCS maintains the vertical flight path and the A/T maintains the selected airspeed. At flare, the throttles are retarded to the aft stop. If a Go-Around is made, the A/T maintains thrust. At touchdown the A/T automatically disengages.

Fig. 35-1  full flight regime A/T mode

[3] The DFCS mode control panel (MCP) is located on the P7 glare shield. The MCP provides the pilots with a central control for the automatic flight control functions of the airplane. The MCP provides control of the autothrottle, autopilot and flight director. Three illuminated push-type switches and a light are directly related to A/T operation, they are A/T ARM SWITCH, N1 SELECT SWITCH, SPEED SWITCH, and A/T ARM LIGHT. The A/T engage (ARM/OFF) switch is two position, solenoid held. The switch is held in ARM, if the A/T engage interlock circuit is satisfied. With N1 mode selected, the A/T controls the throttles maintaining N1 limit thrust. In SPEED mode the A/T maintains the airplane's airspeed.

Fig. 35-2  DFCS MCP

[4] Two A/T disengage switches are located on two end of each throttle lever handle, they provide a means of disengaging the A/T. Two takeoff/Go-around (TO/GA) switches are located on the aft edge of each throttle lever, they are provide a means of engaging the A/T in the takeoff or go-around mode. All four switches are momentary contact type switches. Each has a set of normally open contacts and a set of normally closed contacts. The A/T disengage switches are designed to be operated with the thumb while the hand is on the throttle levers. The two disengage switches are wired in series and the normally closed contacts form a part of A/T engage circuits. Pressing either switch will disengage the A/T. The normally open contacts are in the A/T warning light circuit and are used to reset the warning light. The TO/GA switches are operated with a finger tip while the hand is on the throttle lever. Pressing either switch activates the takeoff or go-around mode for both A/T and AFDS.