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When to disconnect auto throttle before landing

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Hello In the real world does the auto throttle get disconnected when the autopilot is disconnected or do pilots let AT control the approach speed all the way down, also does lnav and vnav only work once the auto pilot is turned on after takeoff, thanks Wayne


Wayne such

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Some airlines do not allow their crews to have the autothrottle on while the autopilot is off during approach. I follow this policy and just disconnect both of them at the same time.


-Alex 

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Some airlines do not allow their crews to have the autothrottle on while the autopilot is off during approach. I follow this policy and just disconnect both of them at the same time.
I do the same. I'm not sure what FAA policies exist regarding this, but from a purely systems stand point it just needs to be disconnected in time to retard the throttles to idle. If you're performing an autoland, even this will be automatic (but where's the fun in that). Eric Szczesniak

Eric Szczesniak

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After disconnecting AP the AT is running and will deactivating when you turn it off. Before take-off, you can set the AT on and select the LNAV and VNAV on, the AP can select above 400ft take off.


Volkan

 

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I disconnect at around 100ft. Some real world pilots hand fly down and would like to control the throttles as well, but in FS I find it hard not to over power or under power, so I let the AT stay in place until just over the threshold.


Yours truly
Boaz Fraizer
Copenhagen, Denmark

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Remember that power affects your pitch. If the auto-throttle is on, you will tend to overpitch: as you raise the nose, the A/T will increase power to compensate for loss of speed. This extra power will raise your noise further. The opposite applies for lowering the nose. For this reason, many pilots tend to disconnect the auto-throttle when they disconnect the autopilot. If you don't do this, the autothrottle will reduce to idle at 27 feet radio altimeter and then disconnect two seconds after touchdown.

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David Zhong

 

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Hello In the real world does the auto throttle get disconnected when the autopilot is disconnected or do pilots let AT control the approach speed all the way down, also does lnav and vnav only work once the auto pilot is turned on after takeoff, thanks Wayne
A search in this forum will show multiple posts by rw 737 pilots stating that Boeing's officiel policy (or recommendation) is to turn off AT when AP is off. Bruno

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Remember that power affects your pitch. If the auto-throttle is on, you will tend to overpitch: as you raise the nose, the A/T will increase power to compensate for loss of speed. This extra power will raise your noise further. The opposite applies for lowering the nose. For this reason, many pilots tend to disconnect the auto-throttle when they disconnect the autopilot. If you don't do this, the autothrottle will reduce to idle at 27 feet radio altimeter and then disconnect two seconds after touchdown.
Wow I had no idea it idles and then disconnects after touchdown, another awesome feature I didnt even know about.

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While there is no official FAA stance on the use of A/T, there is an official stance on the use of A/P for commercial operations: FAR 121.579: 500' or twice the AP fail altitude loss specified by the aircraft's AFM, whichever is lower (providing exceptions for specific operations).


Kyle Rodgers

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A/T and A/P off at about 1000 feet and hand fly the rest. I understood it was Boeing policy that A/T should be off when A/P is off. I recall I read that in the manuals.

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As I have been struggling to manage power on landing when flying without A/P, I have been looking for info on using A/T without A/P. Reading this topic here, it appeared to me that indeed A/T should not be used if A/P is disconnected.I have just been watching a "Cockpit video" featuring the 737-600 flown by Westjet, with a landing visual landing in Fort McMurray. Interesting enough, the PIC flew the aircraft manually but left A/T on until flying over the runway threshold. I clearly heard the PIC order "A/T disconnect" just before touch down.Is there a Westjet pilot out there to comment on this (or anybody else) ? Thanks.


Jean-Marc Jaquier

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As I have been struggling to manage power on landing when flying without A/P, I have been looking for info on using A/T without A/P. Reading this topic here, it appeared to me that indeed A/T should not be used if A/P is disconnected.I have just been watching a "Cockpit video" featuring the 737-600 flown by Westjet, with a landing visual landing in Fort McMurray. Interesting enough, the PIC flew the aircraft manually but left A/T on until flying over the runway threshold. I clearly heard the PIC order "A/T disconnect" just before touch down.Is there a Westjet pilot out there to comment on this (or anybody else) ? Thanks.
Any possibility you could post a link to that video?Regards,

Rick Hobbs

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As I have been struggling to manage power on landing when flying without A/P, I have been looking for info on using A/T without A/P.
What problems are you having?

Matt Cee

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