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Chris Catalano

When is the exact moment you are supposed to disconnect the A/T

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Hi Everyone:
 

Can someone please tell me the exact moment during a descent you are supposed to disconnect the Autothrottle?  I am accustomed to disconnecting 50ft AGL, but I am not sure this is the "official" time to do so. Anyone?

 

Thanks,

 

Chris Catalano 

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Straight off, I don't know. But I do know I would like to be in control of the throttle way before 50ft AGL. Wind strength and direction is not constant in the real world. You need to be ready for instant throttle input during approach and landing.

Bob

 

 

Sent from my iPad using Tapatalk

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50ft is ok. There is no correct answer here, you can disconnect it at top of descend point if you like.


[color=#a9a9a9][size=1][size=4][img]http://forum.avsim.net/public/style_images/flags/rs.png[/img][/size] Lj. Prodanovic[/size][/color]

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50 feet is by the book yes. But why disconnect the AT? It offers alpha floor protection. If you need to add thrust or take some off just do it manually. You aren't going to hurt the servos.

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It's quite heavy while locked to servos and it tend to resist.

 

Anyway, I think manual flight should be with AP and AT off. If you leave AT connected, it's not manual flying anymore, so I tend to disconnect both at the same time.


[color=#a9a9a9][size=1][size=4][img]http://forum.avsim.net/public/style_images/flags/rs.png[/img][/size] Lj. Prodanovic[/size][/color]

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If you forget (or choose not) to disconnect the A/T, what happens if you land with it on?  Will it still maintain the speed that is dialed in right down the runway? (potentially causing a catastrophic result!)

 

Chris Catalano

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I don't know if there's ground logic that would close throttles on touchdown, never tried to land 737 with AT connected unless it's autoland.

 

You can try and inform us ;)


[color=#a9a9a9][size=1][size=4][img]http://forum.avsim.net/public/style_images/flags/rs.png[/img][/size] Lj. Prodanovic[/size][/color]

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Can someone please tell me the exact moment during a descent you are supposed to disconnect the Autothrottle?

For Cat 1, visual and non-precision, the answer is when you feel like it, but not below 50' (FAA) and 158' (JAA) or MDA.

 

Cat II and Cat III depends on equipment and SOPs.


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Since you didn't specify any other conditions than descent, the time to disconnect A/T is when you disconnect the autopilot, at whatever time that is, as you are not supposed to fly "half automatic" in the sense of A/P off, A/T on during any phase of flight other than takeoff or climb (FCTM 1.43). If that is at your TOD or on final doesn't make a great difference.

 

Other than that and as it has already been pointed out above, depending on the rules A/P and A/T need be disconnected as specified in FCOM 1 L.10.5 for single channel operation.

 

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It is the policy at my airline to leave the auto throttles engaged all the way to touchdown. 

RL or virtual?


[color=#a9a9a9][size=1][size=4][img]http://forum.avsim.net/public/style_images/flags/rs.png[/img][/size] Lj. Prodanovic[/size][/color]

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It is the policy at my airline to leave the auto throttles engaged all the way to touchdown.

777 this is normal, but that policy can't be implemented on a 737.


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777 this is normal, but that policy can't be implemented on a 737.

 

It can and that is exactly how it is done at my company.  The A/T is normally left engaged all the way until touchdown per our company procedures.  When left engaged they will begin to retard at 27' RA and will disengage two seconds after touchdown.

RL or virtual?

Very much real.


Joe Diamond

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Wow. Your procedure completely contradicts the recommendation Boeing has stated in our manuals. Live and learn :unsure:


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