B777 FD 8 Degrees
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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.
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.
spannersatcx
The initial rotate attitude is about 15 degress for 2 engines and about 10 degrees for a single engine those are the target attitudes for take-off before the FDs come into play.
I think the question being asked is, why does the FD pitch bar indicate 8 degrees when the FD's are FIRST turned on.
I think the question being asked is, why does the FD pitch bar indicate 8 degrees when the FD's are FIRST turned on.
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why does the FD pitch bar indicate 8 degrees when the FD's are FIRST turned on?
Because that is the value to be flown, upon which all Takeoff distance parameters are calculated, for the airborne one engine inoperative acceleration from Vr to V2. After V2 has been reached, the target attitude will increase according to actual performance.
Regards,
Old Smokey
Because that is the value to be flown, upon which all Takeoff distance parameters are calculated, for the airborne one engine inoperative acceleration from Vr to V2. After V2 has been reached, the target attitude will increase according to actual performance.
Regards,
Old Smokey
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Flight directors aren't programmed for use on the ground, so I don't think the tail-strike senario applies in this case - especially as 12degrees is the tail-strike attitute on the B777-200.
A pitch attitude of 8 degrees is probably a safe compromise between stall warning and a positive rate of climb - which would ensure terrain seperation is ensured even at MTOW and a power setting of 50% N1.
A pitch attitude of 8 degrees is probably a safe compromise between stall warning and a positive rate of climb - which would ensure terrain seperation is ensured even at MTOW and a power setting of 50% N1.
Old Smokey
Quote:
Because that is the value to be flown, upon which all Takeoff distance parameters are calculated, for the airborne one engine inoperative acceleration from Vr to V2.
As TODR is dependent primarily on weight, would this pitch indication cater for a max weight take-off or is it a combination of that and also conditions like hot and high airfields?
Its a pity Boeing does not provide more info. Their manuals are rather sparse unlike Airbus.
Because that is the value to be flown, upon which all Takeoff distance parameters are calculated, for the airborne one engine inoperative acceleration from Vr to V2.
As TODR is dependent primarily on weight, would this pitch indication cater for a max weight take-off or is it a combination of that and also conditions like hot and high airfields?
Its a pity Boeing does not provide more info. Their manuals are rather sparse unlike Airbus.
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MBA747, Sempre Volando,
Yes, that's the way it is. It's a constant pitch value to be flown for the Airborne portion of the Takeoff from Vloff through to V2. It does cater for the worst case condition.
Certification testing is based upon flight at the nominated fixed pitch attitude from Vloff through to V2. This is not unique to Boeing, at one of the manufacturer's acquired by Boeing the figure was / is 9°, and applies at all weights and environmental conditions.
Think about it, in the 1st segment we are told to fly V2 (and the FD is programmed for this), in the 2nd segment we are told to fly V2 or V2 plus a particular additive if a higher speed has been achieved (and the FD is programmed for this), in the 3rd segment we are told to fly a constant altitude (and the FD is programmed for this), and so it goes. What are they going to tell you to fly between Vloff and V2? An attitude which will ensure correct acceleration between the two is what is provided, 8° for the case in point.
It COULD be varied at the manufacturer's discretion to squeeze the last drop of performance from the aircrat, but at this point in time, it's constant.
Regards,
Old Smokey
Yes, that's the way it is. It's a constant pitch value to be flown for the Airborne portion of the Takeoff from Vloff through to V2. It does cater for the worst case condition.
Certification testing is based upon flight at the nominated fixed pitch attitude from Vloff through to V2. This is not unique to Boeing, at one of the manufacturer's acquired by Boeing the figure was / is 9°, and applies at all weights and environmental conditions.
Think about it, in the 1st segment we are told to fly V2 (and the FD is programmed for this), in the 2nd segment we are told to fly V2 or V2 plus a particular additive if a higher speed has been achieved (and the FD is programmed for this), in the 3rd segment we are told to fly a constant altitude (and the FD is programmed for this), and so it goes. What are they going to tell you to fly between Vloff and V2? An attitude which will ensure correct acceleration between the two is what is provided, 8° for the case in point.
It COULD be varied at the manufacturer's discretion to squeeze the last drop of performance from the aircrat, but at this point in time, it's constant.Regards,
Old Smokey
