HighFlier

Autothrottle on Landing

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On the 777 and 787, Boeing recommends to leave the autothrottle on during landing, even when performing manual flight. To my understanding, this is due to the use of fly-by-wire. However, I wonder if the same applies to the 747-8. Since the -8 shares a type rating with the -400, that would lead me to believe that you are supposed to disengage the autothrottle during manual flight. However, since the -8 utilizes fly-by-wire, that would lead me to believe that you are supposed to leave the autothrottle on. Clearly, I’m not sure which is right. Can anyone shed some light on what Boeing recommends for the 747-8?

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The 747-8 is not, in fact, full fly-by-wire, as is the case of the 777 and 787. I think it might just be limited to the ailerons and possibly the spoilers, but I don't remember off the top of my head. In any event, it's not the entire aircraft that's fly-by-wire.

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The 747-8 FCTM does not have a specific recommendation for A/T, which the 777 does.  It suggest that if you are going to disconnect A/T that you need to keep thrust changes minor and that you also need to incorporate "gust factors."  The A/T will automatically adjust for gusts for you and the nice thing about A/T is the help in thrust management it provides on go around with a low altitude level off.

The only electronically actuated controls on the -8 are outboard ailerons.

I prefer A/T landings on the 777 and 747-8, and manual throttle on the 737 and 747-400. That's just my preference.

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I believe that you are supposed to leave AT on, even on the 737NG because of TOGA. That wouldn't work without autothrottle being on.

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8 minutes ago, signmanbob said:

even on the 737NG because of TOGA. That wouldn't work without autothrottle being on.

TOGA button will still work and trigger the FMC to TOGA mode and the FD will command a climb. The only thing is that you will have to move the thrust levers forward on your own.

You can perform a go-around without the autothrottle on (fortunately!)

 

Edited by Budbud
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In real life we disengage the a/t for all manual landings in the 400 and -8. Some pilots will always disconnect it along with the autopilot, others will leave it on for a while, that part is just a matter of preference, but unless it’s an autoland we don’t land with it engaged. I do not know if this is Boeing procedure or company specific  

Pushing the TOGA will reactivate the a/t on a go around so that isn’t an issue. You have to make sure however that you disconnect it using the quick disconnect switches on the throttle quadrant. If you turn the a/t switch off they will not reactivate. 

 

Jeffery Williams

Edited by Jetlinker
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2 hours ago, downscc said:

The 747-8 FCTM does not have a specific recommendation for A/T, which the 777 does.  It suggest that if you are going to disconnect A/T that you need to keep thrust changes minor and that you also need to incorporate "gust factors."  The A/T will automatically adjust for gusts for you and the nice thing about A/T is the help in thrust management it provides on go around with a low altitude level off.

The only electronically actuated controls on the -8 are outboard ailerons.

I prefer A/T landings on the 777 and 747-8, and manual throttle on the 737 and 747-400. That's just my preference.

Same here. I have performed  some landings with A/T on and worked like a charm.

Best.

 

Miquel Egea.

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4 hours ago, Jetlinker said:

In real life we disengage the a/t for all manual landings in the 400 and -8. Some pilots will always disconnect it along with the autopilot, others will leave it on for a while, that part is just a matter of preference, but unless it’s an autoland we don’t land with it engaged. I do not know if this is Boeing procedure or company specific  

Pushing the TOGA will reactivate the a/t on a go around so that isn’t an issue. You have to make sure however that you disconnect it using the quick disconnect switches on the throttle quadrant. If you turn the a/t switch off they will not reactivate. 

 

Jeffery Williams

Is this the same for the 737NG?

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5 hours ago, signmanbob said:

Is this the same for the 737NG?

Not sure about the 737 as I haven’t flown one. 

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It has been years since I have flown the NGX but if I recall well, the quick disconnect button also flips the A/T arm swith to off in which case, autothrottle would not be reactivated by pressing TOGA.

Edited by Budbud
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36 minutes ago, maukro_1990 said:

Is it common to leave autothrottle on during the whole landing? 

What airplane?  Manual or auto landing?

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On 11/6/2018 at 7:51 PM, downscc said:

What airplane?  Manual or auto landing?

Do i leave the autothrottle enganged during a manual landing with a 747-8? I saw lots of videos where simmers leave AT on when AP was off. The question is if i can leave the autothrottle enganged during a manual landing, like i normally do with a T7?!

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1 hour ago, maukro_1990 said:

Do i leave the autothrottle enganged during a manual landing with a 747-8? I saw lots of videos where simmers leave AT on when AP was off. The question is if i can leave the autothrottle enganged during a manual landing, like i normally do with a T7?!

If you mean the switch, then yes, although that depends on each carrier. Some carriers close it all together. The Boeing procedure is to leave the switch to ON all the time.

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32 minutes ago, Olympic260 said:

If you mean the switch, then yes, although that depends on each carrier. Some carriers close it all together. The Boeing procedure is to leave the switch to ON all the time.

I concur. Where I work we turn it off after landing and turn it on just before takeoff, as having it on during the taxi and inadvertently hitting the TOGA could make for a rather bad day. 

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4 hours ago, maukro_1990 said:

Do i leave the autothrottle enganged during a manual landing with a 747-8? I saw lots of videos where simmers leave AT on when AP was off. The question is if i can leave the autothrottle enganged during a manual landing, like i normally do with a T7?!

On 11/5/2018 at 12:45 AM, signmanbob said:

Is this the same for the 737NG?

 

there's a significant difference between the autothrottle arm switch on the MCP and the autothrottle disconnect buttons on the thrust levers! I've seen (too) many people in YT having their joystick buttons assigned to A/T arm in FSUIPC which will turn the autothrottles off completely. As "Jetlinker" above said, when you DISARM the autothrottle you can press ToGA as much as you want, the engines won't spool up automatically in case of a go around, only your flight mode will change to go around. And that at least is the same on the 737, yes. when you flip down that ARM switch, then it is just that: disarmed. Although at the moment I really can't tell what happens on the 737 when you press the disc buttons on the throttles. Will that arm switch stay up or not? But on the 777 if you flip down the arm switches it's off.

Edited by Ephedrin

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3 hours ago, Ephedrin said:

 

there's a significant difference between the autothrottle arm switch on the MCP and the autothrottle disconnect buttons on the thrust levers! I've seen (too) many people in YT having their joystick buttons assigned to A/T arm in FSUIPC which will turn the autothrottles off completely. As "Jetlinker" above said, when you DISARM the autothrottle you can press ToGA as much as you want, the engines won't spool up automatically in case of a go around, only your flight mode will change to go around. And that at least is the same on the 737, yes. when you flip down that ARM switch, then it is just that: disarmed. Although at the moment I really can't tell what happens on the 737 when you press the disc buttons on the throttles. Will that arm switch stay up or not? But on the 777 if you flip down the arm switches it's off.

On the 737 the A/T switch is a solenoid one. When you press the A/T disconnect it will kill the switch as well. On the 777/744/748 this does not happen. The only way to kill the switch is to manually close it.

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34 minutes ago, Olympic260 said:

On the 737 the A/T switch is a solenoid one. When you press the A/T disconnect it will kill the switch as well. On the 777/744/748 this does not happen. The only way to kill the switch is to manually close it.

But you don‘t have to advance the throttles manually on a go around in the 737, have you??? To be honest, if I screw up my approach and do a last second go around I always do it manually and press TOGA after that, but I know it‘s not the correct procedure. It‘s caused by my PC controllers ^^

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In the 737, if you press the A/T quick disconnect button, the A/T is disarmed (A/T arm switch off), so you have to advance manually the thrust levers for a go around.

In this configuration, pushing TOGA will only set the TOGA mode and the FD to command the go around but the A/T will no kick in.

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