777 AIRCRAFT MAINTENANCE MANUAL
AFDS -OPERATION -AUTOLAND ROLL AND YAW
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AFDS -OPERATION -GO-AROUND
General
Go-around is a combined AFDS and TMCF mode. The pilot uses the mode in these conditions:
*
An aborted approach
*
Windshear during takeoff or landing.
The pitch command keeps the airplane in these limits:
*
Flap placard speeds
*
Maximum operating velocity and Mach (VMO/MMO)
*
Minimum speed.
The roll command holds the present track of the airplane over the ground.
In go-around, the flight director display on the PFDs automatically comes on even if the flight director switches are off. This is called AUTO POP UP. It occurs when all these conditions are true:
*
A flight director switch is off
*
The trailing edge flaps are not up
*
The pilot pushes a TO/GA switch.
Go-Around Arm
Go-around arms when the airplane is in the air and, one of these conditions is true:
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*
Glideslope mode is active
*
The trailing edge flaps are not up.
The PFD and MCP continue to show the approach modes.
Go-Around Active
The go-around mode starts when the pilot pushes either TO/GA switch. With one push of the TO/GA switch, the autothrottle controls to a 2000 ft/min climb. With a second push, the autothrottle controls to full go-around thrust.
TO/GA shows on the PFD as the active mode for roll and pitch. The autothrottle mode is thrust (THR).
The AFDS supplies an initial pitch up command to make sure the airplane clears any obstacles. After the pitch up command, the AFDS commands one of these:
*
Target airspeed
*
A combination of target airspeed and pitch attitude
*
Pitch attitude.
If the climb rate is less than 600 FPM, the pitch command is to hold attitude. For a climb rate between 600 FPM and 1200 FPM, the pitch axis holds a mixture of airspeed and attitude. For a climb rate more than 1200 FPM, the pitch axis holds a target airspeed.
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AFDS -OPERATION -GO-AROUND
For go-around with an engine out, the pitch axis command is a mixture of airspeed and attitude at a climb rate less than 1200 FPM. For a climb rate more 1200 FPM, the pitch axis holds a target airspeed.
This mix of speed and attitude command gives windshear protection during go-around.
Go-Around Off
Below 400 feet, the AFDS stays in go-around unless the pilot disengages the autopilot and sets the flight director switches to off.
Above 400 feet, the pilot can select another roll or pitch mode.
In this example, the AFDS captures the MCP altitude of 5000 feet. The PFDs show ALT and the airplane levels off at 5000 feet.
Go-around stays as the active roll mode until the pilot selects another roll mode.
The pitch mode change from TO/GA to ALT makes the autothrottle change to SPD mode at the speed set on the MCP.
When a go-around occurs below 1500 feet during an autoland, all six backdrive actuators stay engaged until a different roll or pitch mode, other than TO/GA, is selected.
When a go-around occurs below 1500 feet during an autoland,
bus-isolation stays active until the airplane is above 400 feet.
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AFDS -OPERATION -GO-AROUND
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AFDS -FUNCTIONAL DESCRIPTION -AUTOPILOT CONTROLS
General
The AFDC program has the:
*
Pitch control laws
