Take off mode is engaged by pressing either of the takeoff go-aroundswitches on the throttles, with the aeroplane on the ground the auto throttlesarmed and the desired n1 thrust limit selectedfrom the flight management system computer display unit. the autothrottle enunciation changes from armed to n1 and the thrust levers advancetoward takeoff thrust. the auto throttle sets the computed n1 value. between 60to 80 knots the auto throttle enunciation changes to throttle hold.
to indicatethe auto throttle cannot change thrust leaver position although they can stillbe repositioned manually. after takeoff the auto throttles remain in throttlehold. until 400 feet radio altitude is reached and 18 seconds have elapsedsince lift off. auto throttleenunciation then changes from throttle hold to arm.
reduction to climb thrust can now be made by pressing the N 1 switch.flexible takeoff or takeoff legs is a facility to allow the auto throttle tocalculate and provide a reduced thrust takeoff by entering an assumedtemperature into the flight management system or the thrust mode limit panel. theautothrottle maintains thrust at the n1 limit selected from the flight managementsystem computer display unit, n1 is enunciated with the autothrottle and the n1switch illuminates. pressing the n1 switch changes the auto throttle mode fromn1 to armed. if an engine fails while the auto throttle isin the n1 mode the thrust lever of the failed engine would advanceforward a few degrees and return to or below the other thrust lever position. thespeed mode is available throughout the flight once the takeoff phase is completed.
pressing the mode control panel speed selects which selects the speed mode ifcompatible with the engaged automatic flight director system pitch mode. MCPspeed is enunciated for the auto throttle and the speed mode switch illuminatesthe speed or Mac shown in the mode control panel IAS Mac display is the targetspeed the auto throttle will not set power above the displayed n1 limit howeverthe auto throttle can exceed an n1 value that had been manually set by the n1manual set knob if an engine fails while the auto throttle is in a speed modeboth thrust levers advance together to maintain the target speed the flightmanagement system speed mode is an auto throttle mode which is commanded by theflight management system during vertical navigation operation when engaged themode control panel IAS mag display is blank the SB cursors are positioned atthe flight management systems commanded airspeed and the auto throttlemaintains this commanded speed our FMC speed is enunciated in the auto throttleflight mode annunciator the auto throttle is limited to the n1 value shown onthe n1 gauge on the engine instruments and crew alerting system display theautothrottle enunciates arm when the auto throttle arm switch is at arm and noauto throttle mode is engaged the thrust levers can be manually positioned withoutinterference from the auto throttle system while arm is enunciated the autothrottle automatically transfers to arm from the speed or n1mode when the modeis be selected by pressing the respective mode selector switch while the switchis illuminated the autothrottle engages and enunciates retard during levelchange and vertical navigation descents retard changes to arm when the thrustlevers reach the aft stop or when manually prevented from reaching the aft stopduring landing the retard mode engages reduces thrust and enunciates retard shortlyafter flare mode engagement or at 27 feet Radio altitude whichever occurs firstduring a non-precision or visual approach with flaps extended to 15 or greaterand the automatic flight director system not in altitude require or altitudehold the autothrottle retard mode engages at 27 feet Radio altitude theautothrottle automatically disengages approximately two seconds after landingtouchdown with the autothrottle armed switch at arm i autothrottle go aroundmode is armed when descending below 2,000 feetradio altitude with or without the automatic flight director systemengagedonce armed the autothrottle go-around mode can be engaged until twoseconds have elapsed after landing touchdown pressing either takeoff go-aroundswitch engages the autothrottle go-around mode thrust or n1 is enunciated forthe auto throttle and the thrust levers advanced to the reduced go-aroundthrust setting this reduced setting produces a 1,000 to 2,000 feet per minuterate of climb after reaching reduced go-around thrust pressing eithertakeoff go-around switch the second time signals the auto throttle to advancethrust to the full go-around n1 limit after reaching reduced or full go-aroundthrust the auto throttle go-around mode can be terminated by selecting another automaticflight director system pitch mode or when altitude acquire enunciates engaged