AFDS - OPERATION - TAKEOFF
General
The F/D display supplies the pilot with roll and pitch commands during takeoff. After the airplane is off the ground, the pilot can stay in the F/D takeoff mode, or when the airplane is above 50 feet radio altitude, the pilot can engage the autopilot to the takeoff mode.
Both F/D switches must be set to the OFF position to remove the takeoff mode.
The takeoff mode has this sequence:
Before takeoff
Takeoff start
Lift-off/in air
Climbout.
Before Takeoff
All of these conditions must be true to put the F/D in the takeoff mode (TO/GA):
The captain and/or the first officer F/D switches are in the ON position
The autopilot is not engaged
The airplane is on the ground.
The PFD shows:
FLT DIR as the AFDS status
TO/GA as the pitch and roll mode
The F/D pitch bar shows eight degrees
The F/D roll bar shows wings level.
The pilot sets an engine-out climb speed (V2) and a clearance altitude on the MCP. The autothrottle (A/T) arm switches are on.
Takeoff Start
The pilot pushes a TO/GA switch on the thrust levers. The autothrottle engages in the takeoff thrust mode and the throttles move forward until the engines reach takeoff thrust. THR REF shows on the PFDs as the active autothrottle mode.
In takeoff, the flight director shows on the PFDs automatically even if the flight director switches are in the OFF position. This is called AUTO POP UP. It occurs when all these conditions are true:
A flight director switch is in the OFF position
The pilot pushes a TO/GA switch
The trailing edge flaps are not up.
The TMCF removes power from the autothrottle servo motors at 80 knots. Throttle hold (HOLD) shows on the PFDs.
Lift-Off/In Air
For a normal lift-off, the pitch command holds:
Target airspeed
Combination of airspeed and pitch attitude
Pitch attitude.
If the climb rate is less than 600 feet per minute, the pitch command is to hold attitude. For a climb rate between 600 feet per minute and 1200 feet per minute, the pitch command holds a mix of airspeed and attitude. For a climb rate more than 1200 feet per minute, the pitch command holds a target airspeed.
If an engine fails during takeoff, the pitch axis command is a mix of airspeed and attitude for a climb rate less than 1200 feet per minute. For a climb rate more than 1200 feet per minute, the pitch axis holds a target airspeed.
The target airspeed for a normal takeoff is the larger of these two:
V2 plus 15 knots
The airspeed at lift-off plus 15 knots.
If the airspeed is more than the target for five seconds, the target airspeed becomes the smaller of the current airspeed or V2 plus 25 knots.
This mix of speed and attitude commands gives wind shear protection during takeoff and go-around. The F/D pitch command also keeps the airplane in these limits:
Flap placard speeds
Maximum operating velocity and Mach (VMO/MMO)
Minimum speed.
At five feet radio altitude, the roll command changes to track hold.
The autothrottle stays in HOLD.
FLT DIR remains the active AFDS status until the pilot engages the autopilot.
The pitch and roll modes remain in TO/GA until the pilot selects another pitch or roll mode.
Climb Out
The roll command continues to hold track. The pitch command continues to hold speed, attitude, or a mix of speed and attitude.