mode is detected.
2) An autothrottle disconnect switch on the thrust levers is
pressed.
3) The A/T ARM switch is positioned to OFF.
4) The reverse thrust levers are set in the reverse thrust
position.
(6) Typical Autothrottle Flight Profile (Fig. 10)
(a) Takeoff (T/O)
1) When TO is selected on the TMSP, a reference EPR is calculated based on temperature and altitude. A provision to insert artificially high temperatures for derated takeoff is included. When the EPR (or THR) mode on the MCP is engaged, the thrust levers are driven until the reference EPR is reached. The T/O mode deactivates the autothrottle servo by removing the 115v ac excitation and zeroing the command when the airplane reaches 80 knots CAS. This prevents the thrust levers from retarding after T/O thrust is set.
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TAKEOFF. ASSUMED TEMPERATURE DERATE
DISENGAGE
. TO EPR
. THRUST
. THROTTLE HOLD AT 80 KNOTS
REVERSER. DISENGAGESWITCH
Typical Autothrottle Flight Profile
Figure 10
A
(b)
(c)
(d)
(e)
(f)
(g)
757 MAINTENANCE MANUAL
Climbout (CLB)
1) When the airplane is more than 400 feet above ground level and the climb mode is selected on the TMSP, a new EPR REF is calculated by the TMC. The engines are retarded to the new EPR REF.
Flight Level Change (FLCH) - Climb
1) Engagement of the FLCH mode on the MCP causes the TMS to accelerate the airplane by driving the thrust levers until the reference EPR is reached. The EPR REF and maximum PLA limits are not exceeded. Manual override of the thrust levers by the pilot causes the autothrottle servo to hold until a new mode is selected, capture of the selected altitude is achieved, or the REF EPR is exceeded.
Cruise (CRZ)
1) When CRZ is selected on the TMSP, the thrust levers control to the speed/Mach reference on the MCP. The maximum/minimum speeds, EPR, and PLA limits are still observed.
Vertical Navigation (VNAV)
1) The VNAV mode transfers both pitch and thrust control to the Flight Management Computer System (FMCS). The FMCS selects autothrottle modes (airspeed, Mach, and thrust) and provides the corresponding target reference values. The FMCS also commands throttle hold and retard to idle. All commands from the FMCS are subject to the thrust and speed limits computed by the TMS.
Flight Level Change - Descend
1) Selecting FLCH causes thrust lever retard to the computed aft limit until selected altitude is captured. Manual override of the thrust levers by a pilot causes autothrottle servo hold.
Speed (SPD)
1) The speed mode is selected manually by pressing the SPD pushbutton on the MCP. The autothrottle engages to control airspeed (or Mach) to the reference command on the IAS/MACH display on the MCP. The speed mode is automatically engaged upon capture of the selected altitude when in FLCH mode, or when the FLCH mode is exited.
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A
757
MAINTENANCE MANUAL
(h)
Go-Around (G/A)
1) The thrust levers are automatically advanced for a positive rate-of-climb when a go-around switch on the thrust levers is pressed.
(i)
Flare
1) During an A/P multi-channel approach, the thrust levers retard to the aft limit on command from the FCCs.
(7) Thrust Management System - Mode Select Logic
(a)
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