Fig. 35-4  A/T modes on EADI

[5] The primary function of the autothrottle interface with the EADI is for the flight mode annunciator (FMA). The FMA function utilizes the top of the EADI display to annunciate the autothrottle mode. Engaged modes are display in green .These modes are N1, GA, RETARD, FMC SPD, MCP SPD and THR HOLD. ARM annunciation is displayed in white. In addition, an airspeed tape with a target airspeed index is displayed on the left side of the EADI.

Fig. 35-3 A/T disengage and TO/GA switches

[6] The takeoff mode is prepared for use by engaging the FMCS in the takeoff mode with the airplane on the ground. The FMA will annunciate TO for the N1 limit . Moving the A/T engage switch to the ARM position arms the A/T for takeoff and FMA will display ARM for the A/T . The A/T cannot be engaged on the ground unless the FMCS is in the takeoff mode. Pressing either TO GA switch engages the takeoff mode. The throttles advance at 15 degrees per second to the predicted throttle position and the FMA A/T annunciation changes from ARM to N1. When the engine N1 approaches the takeoff rating the throttles make final adjustments to overcome system rigging tolerances and obtain the correct N1. At 84 knots CAS the A/T enters a hold state, two independent circuits ensure that the throttle servomotor are unable to move. A THR HOLD annunciation comes into view on both FMA when both hold circuits have operated. In addition to N1 operation in the takeoff mode, the A/T will control N1 in climb. Pressing the N1 pushbutton on the MCP engages the N1 mode and the A/T adjusts to the climb thrust rating, the FMA annunciates N1 and the pushbutton N1 switch on the MCP is illuminated.

[7] As the airplane approaches the selected altitude under VNAV control, the A/T is switched into the FMC SPD mode. It annunciates FMC SPD and will remain in that mode during the altitude hold mode. When the airplane begins to descend under VNAV control, the A/T retards the thrust levers to idle and annunciates RETARD. The mode is terminated by either pilot stopping the throttles or the throttles driving against the idle stop . The A/T then goes to and annunciates ARM mode.

[8] When the DFCS captures the glide slope, the VNAV mode is disengaged and the A/T switches to the MCP SPD mode. Selection of desired speed is made on the DFCS MCP. The A/T annunciates MCP SPD and the SPEED pushbutton on the MCP is illuminated. The pushbutton is illuminated to indicate to the pilot that pressing it will cause the A/T to revert to ARM. During the landing flare maneuver, the flare retard provides a thrust reduction to idle in six seconds. The FMA will show RETARD. At squat, the throttles are moved aft at eight degrees per second to insure throttles move quickly to idle if any residual throttle displacement exists. The A/T disengages two seconds after squat with no warning light.
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