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airspeed at inititation of go-around is greater than IAS/Mach window plus 25
knots, that speed is maintained. GA displays as the reference thrust limit on the
primary EICAS engine display.
VNAV –
Arm VNAV by pushing the VNAV switch (the light illuminates and VNAV
annunciates on the PFD pitch mode annunciator in white characters below the
current pitch mode).
VNAV activates at 400 feet and provides pitch commands to maintain the FMC
computed airspeed/path:
• VNAV SPD (active) – AFDS maintains the FMC speed displayed on the
PFD and/or the CDU CLIMB or DESCENT pages. During speed
intervention, use the MCP IAS/MACH selector to manually set the speed
• when a VNAV descent is initiated before the top of descent (T/D) and the
airplane subsequently intercepts the VNAV descent path, the pitch
annunciation may change from VNAV SPD to VNAV PTH
April 01, 2001
747 Operations Manual
Automatic Flight -
System Description
Copyright © The Boeing Company. See title page for details.
D6-30151-425 4.20.7
• VNAV PTH (active) – AFDS maintains FMC altitude or descent path with
pitch commands. For a non-entered headwind, thrust may increase to
maintain the VNAV descent path. If the MCP altitude window remains set
to the current cruise altitude and the airplane is within two minutes of the
top of descent, the CDU scratchpad message RESET MCP ALT displays
• VNAV ALT (active) - If a conflict occurs between the VNAV profile and
the MCP altitude, the airplane levels and the pitch flight mode
annunciation becomes VNAVALT. The airplane maintains altitude. To
continue the climb or descent, change the MCP altitude and push the
altitude selector or change the pitch mode
V/S –
Pushing the V/S switch opens the vertical speed window and displays the current
vertical speed. It also opens the IAS/MACH window (if blanked). Pitch
commands maintain the rate of climb or descent selected in the V/S window.
FLCH SPD –
Pushing the FLCH switch opens the IAS/MACH window (if blanked). Pitch
commands maintain IAS/MACH window airspeed or Mach.
ALT –
Altitude hold mode is activated by:
• pushing the MCP altitude HOLD switch, or
• capturing the selected altitude from a V/S or FLCH climb or descent
G/S -
AFDS follows the ILS glideslope.
FLARE –
• FLARE (armed) - during autoland, FLARE displays below 1,500 feet RA
• FLARE (active) - during autoland, flare activates between 60 and 40 feet
RA. FLARE deactivates at touchdown and the nosewheel smoothly
lowers to the runway
Autothrottle System
The autothrottle system provides thrust control from takeoff through landing.
Autothrottle operation is controlled from the MCP and the CDUs. The MCP
allows mode and speed selection. The CDU allows FMC reference thrust limit
selection. When a pitch mode is active, FMC selects autothrottle modes and target
thrust values. Refer to Chapter 11, Flight Management, Navigation, for FMS and
CDU operation.
The autothrottle can be operated without using the flight director or the autopilot.
The autothrottle can be manually overridden or disconnected by using either
autothrottle disconnect switch.
April 01, 2001
747 Operations Manual
Copyright © The Boeing Company. See title page for details.
4.20.8 D6-30151-425
Automatic Flight -
System Description
Autothrottle Thrust Lever Operation
The autothrottle system moves thrust levers to control speed or thrust, depending
on the active mode.
Thrust levers can be manually positioned without disconnecting the autothrottle.
After manual positioning and release, the autothrottle repositions thrust levers to
comply with the active mode. The autothrottle system does not reposition thrust
levers while in HOLD mode.
Autothrottle Disconnect
The autothrottle system can be disconnected manually by positioning the
Autothrottle Arm switch to OFF or by pushing either Autothrottle Disconnect
switch. The EICAS caution message AUTOTHROT DISC displays when the
autothrottle has been manually or automatically disconnected.
Autothrottle disconnect occurs if a fault in the active autothrottle mode is detected,
or when a reverse thrust lever is raised to reverse idle. The autothrottle also
disconnects and cannot be reactivated if both FMCs fail or two or more engines
are shut down. The autothrottle disconnects when the FMC Master switch is
switched, but can be reactivated.
Automatic Flight Operations
Automatic Flight - Takeoff and Climb
Takeoff is a flight director only function of the takeoff/go–around (TO/GA) mode.
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