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ssair1

Auto-throttle Related..

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If A/T is engaged, with MCP Speed, and AP is off, do you have to manually RETARD before Vref? 

Kind regards, 

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You cant land 737 and 747 with AP off and AT on, but can do it with the 777. though it‘s not very elegant. 

Normally it‘s left thumb click click right thumb click click. 

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13 minutes ago, Ephedrin said:

You cant land 737 and 747 with AP off and AT on, but can do it with the 777. though it‘s not very elegant. 

1

Where have you taken this information from? It seems as if there are conflicting responses to this question: 

 

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38 minutes ago, ssair1 said:

Where have you taken this information from? It seems as if there are conflicting responses to this question: 

 

My Cousin flies the 737. 

The 737's autoland function inclueds a throttle idling mechanism. But this is a fully automatic flight mode while Boeing doesn't allow (or recommend?) a landing with enganged AT. It might work, but as long as it isn't officially adviced it is not save to do so. It isn't ment to be done and so you can not be sure it will work properly. (more or less the words of my Cousin a couple of years ago) Imagine gusty weather or anything differing from standard.

Concerning the 777 there are also several opinions. While it is officially allowed to keep its AT enganged (not to be confused with armed) it is still not elegant. Either you use the full automation on an autoland of you fly manually.. left thumb, then right thumb (as captain).

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If you are hand flying the 737 and the FD is tracking the LOC and G/S in APP mode then the autothrottle will automatically retard thrust at around 50ft or so, at least that's what PMDG has simulated. Although as Marc said, it most likely isnt a recommended practice.

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I Always left the autothrottle ON in my 5000 hours of MD80 flying. Always left the autothrottle ON on my first 800 hours of the B777. Mind you, in the 777, the manual states that it is designed to have the AT ON during ALL phases of flight. Weather it's an ILS, an RNAV, an RNP-AR or a FD OFF visual, the autothrottle retards in the same way. Same as on the MD80. I don't know why the recommendation is different on the other Boeings. It might be a combination of the traditional trim system and the power - pitch couple. The two planes I flew mitigated this by not having a big power-pitch couple tendency, or by having an automated trim system.

So again, at least on the 777, there's no reason to turn OFF the AT in 99% of the time. The FCTM will probably have some text regarding the matter.

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2 hours ago, xkoote said:

I Always left the autothrottle ON in my 5000 hours of MD80 flying. Always left the autothrottle ON on my first 800 hours of the B777. Mind you, in the 777, the manual states that it is designed to have the AT ON during ALL phases of flight. Weather it's an ILS, an RNAV, an RNP-AR or a FD OFF visual, the autothrottle retards in the same way. Same as on the MD80. I don't know why the recommendation is different on the other Boeings. It might be a combination of the traditional trim system and the power - pitch couple. The two planes I flew mitigated this by not having a big power-pitch couple tendency, or by having an automated trim system.

So again, at least on the 777, there's no reason to turn OFF the AT in 99% of the time. The FCTM will probably have some text regarding the matter.

I really could imagine that it is just that: on the MD80 the engines are in the back and the 777 has the advantage of the FBW. The 737 has a known tendency to pitch down when the engines spool down (around 60% N1 to idle is a significant thrust delta) that is easily to compensate when you move the throttles yourself but could surprise you wenn done automatically and isn‘t countered by the airplane.

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4 hours ago, xkoote said:

The FCTM will probably have some text regarding the matter.

The NGX FCTM is rather quiet on the use of autothrottle and landing, and I believe this depends more on company operating policies than Boeing recommendations.  The only related text I found was for go around or missed approach procedures where autothrottle should be disconnected when A/P reverts to single controller during the procedure.  I could argue that using A/T all the way to flare and reverse thrust is acceptable, considering the FMS will control airspeed in VNAV all the way to landing if properly set up.  The only time I use A/T in the NGX is during CATIII approaches; otherwise, I always disconnect the A/T a few moments before I disconnect A/P and always manually land.  The B744 A/T is generally disconnected for manual landings as well according to advice I got from RSR during beta.  The 777 is a different beast and A/T is generally used all the way to landing, according to a few I have confidence in on such matters.  Of course company policies always trump opinions.

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