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When to disconnect auto throttle before landing

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Maybe, not sure of the circumstances.  I have flown many non precision approaches where I disconnect A/T before landing.  However, since I am shooting a GPS or RNP approach I am in APP mode but it has nothing to do with ILS.  I can't imagine disconnecting A/T never working..., of course, it must be manually disconnected unless you are flying a coupled precision approach.

 

Discussion here: http://www.avsim.com/topic/486399-throttles-dont-retard-on-landing-p3d/

 

I usually always disconnect A/T with AP as well, but if the real thing will idle at 27' RA with or without AP, then it'd be nice to have that option.  Seems some carriers allow it.


- Chris Jefferies

 

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of course, it must be manually disconnected unless you are flying a coupled precision approach.

 

Which is not true of the real airplane.


Joe Diamond

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I have had bad luck leaving A/T on , hand flying the approach, flaring at around 20 feet and having the A/T not disconnect, resulting in a long landing. I just turn it off at about 100 ft, and no problem. 


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I've not had the same problem with coupled ILS approach.  A/T starts retarding to idle below 50 ft (not sure exactly when) and is in idle when I flare.  A long landing can be due to floating instead of making a positive ground contact, which is real easy to do in a PC simulator.  Not questioning your technique Bob, heavens no... but I have to watch the far end of the runway to make sure I don't float or do the opposite as in a carrier landing.


Dan Downs KCRP

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I've not had the same problem with coupled ILS approach.  A/T starts retarding to idle below 50 ft (not sure exactly when) and is in idle when I flare.  A long landing can be due to floating instead of making a positive ground contact, which is real easy to do in a PC simulator.  Not questioning your technique Bob, heavens no... but I have to watch the far end of the runway to make sure I don't float or do the opposite as in a carrier landing.

 

No floating for me, I can hear and feel the power come up as I flare and just fly level. If I didn't disconnect the A/T manually and pull throttle to zero, I would go right off the end of the runway at 20 feet AGL. Been doing this in real life as well as simming for too many decades to not know what is happening. 


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I can hear and feel the power come up as I flare and just fly level.

 

I don't experience that, in fact I can't make it do it if I try.  After the engines spool down for rotation (automatically by A/T), there is no more thrust.  Now the question is why is this happening to you and others.

 

Again, I didn't question your technique, I'm sure we both have more time waiting for the fuel truck than most have in their logbooks.

 

I am using Thrustmaster throttles, not going through FSUIPC but calibrated in P3D. I have the blue arc enabled on the N1 dials to show my throttle when moving.  My options include Fail Operational but normally uncouple the A/P around 1000 AGL.  Any ideas?


Dan Downs KCRP

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I don't experience that, in fact I can't make it do it if I try.  After the engines spool down for rotation (automatically by A/T), there is no more thrust.  Now the question is why is this happening to you and others.

 

Again, I didn't question your technique, I'm sure we both have more time waiting for the fuel truck than most have in their logbooks.

 

I am using Thrustmaster throttles, not going through FSUIPC but calibrated in P3D. I have the blue arc enabled on the N1 dials to show my throttle when moving.  My options include Fail Operational but normally uncouple the A/P around 1000 AGL.  Any ideas?

 

 

I very carefully adjust throttles to match the A/T setting on glideslope plus I even set it a bit lower, using the blue arc. Now if don't disconnect the A/T, the power setting stays at that descent level right through the flare altitude ( around 20 feet) , and the aircraft flies merrily along, level at around 10-15 feet. In order to land, which I did this afternoon, I have to force the nose down a bit, so it contacts the runway ( stupid way to land an aircraft and I would never do that in real life). If I manually disconnect A/T. and pull throttle to min at flare, aircraft flares normally, and descends to the runway at landing zone solid marker. My average landing in the 737 according to my stats from my VA is around -200fpm. 


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I very carefully adjust throttles to match the A/T setting on glideslope plus I even set it a bit lower, using the blue arc. Now if don't disconnect the A/T, the power setting stays at that descent level right through the flare altitude ( around 20 feet) , and the aircraft flies merrily along, level at around 10-15 feet. In order to land, which I did this afternoon, I have to force the nose down a bit, so it contacts the runway ( stupid way to land an aircraft and I would never do that in real life). If I manually disconnect A/T. and pull throttle to min at flare, aircraft flares normally, and descends to the runway at landing zone solid marker. My average landing in the 737 according to my stats from my VA is around -200fpm. 

 

Blue arc?

I don't experience that, in fact I can't make it do it if I try.  After the engines spool down for rotation (automatically by A/T), there is no more thrust.  Now the question is why is this happening to you and others.

 

Again, I didn't question your technique, I'm sure we both have more time waiting for the fuel truck than most have in their logbooks.

 

I am using Thrustmaster throttles, not going through FSUIPC but calibrated in P3D. I have the blue arc enabled on the N1 dials to show my throttle when moving.  My options include Fail Operational but normally uncouple the A/P around 1000 AGL.  Any ideas?

 

Ideas?  About why some have a proper disconnect and others don't? 

 

I don't usually leave the A/T on for a hand-flown approach, but the one or two times I have, it seemed the A/T wasn't spooling down.  I always disconnect A/T and almost never leave the APP mode enabled very long.  Once the runway is visible I hand-fly, as long as my final checks are complete.  I personally think that if established on final with correct flaps and speed, the NGX lands perfectly.  Perhaps the 800/900 are harder to place softly, I usually fly the 700.  I did a flight into SFO the other night and was established perfectly.  I placed it down with grace. In all honesty, if you watch videos of landings, most planes require some forward and backward inputs to the elevator to obtain the right angle.  The NGX is really the only one that seems to do this.  All others simply require back pressure and idle throttle.  With the ground effect this is proper flight dynamics, it's just hard to accomplish in the sim.  Takes a lot less movement. 

 

I should add that I'm not using FSUPIC for calibration, despite owning the paid version.  I'm also on FSX:SE.

Upon reviewing videos, most planes seem to require a good deal of forward and backward pressure to maintain the proper angle.  Although a -200 series, this demonstrates the yoke movement. 

 

 

-800 here:

https://www.youtube.com/watch?v=D6t6nC6DiFk

 

Some aircraft seem to require more yoke movement.  The Dash 8 seems to require very little forward pressure during flare.  Hopefully this reflects the FDE for the Majestic.  Nevertheless, most of us are so used to sim aircraft only requiring back-pressure on landing.  I've had a lot of add-on since FS2002, so it was hard to adjust to the FDE in the NGX.  I don't even think the original NG simulated this ground effect that much.

 

Anyhow, back to the A/T.  If the real NG would idle at 27' AGL regardless of AP status, then I wish the NGX would.  It shouldn't matter that most carriers or Boeing recommend otherwise. Like the MD-11, it's nice to sometimes fly to the runway without messing with the throttle.


- Chris Jefferies

 

Asus Maximus VII Hero motherboard | Intel i7 4790k CPU | MSI GTX 970 4 GB video card | Corsair DDR3 2133 32GB SDRAM | Corsair H50 water cooler | Samsung 850 EVO 250GB SSD (2) | EVGA 1000 watt PSU

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I very carefully adjust throttles to match the A/T setting on glideslope plus I even set it a bit lower, using the blue arc. Now if don't disconnect the A/T, the power setting stays at that descent level

 

That's where we differ, I'll may match the throttle position on the N1 dial during approach but I pull throttles back to idle before flare even in A/T.  I suspect that when the throttle controller retards thrust for your flare you are overriding it with the above idle throttle position. Depends on throttle override options too maybe, mine is set to override in HOLD only.  Too bad we don't have realistic motorized throttles.

 

 

 


I have to force the nose down a bit,

 

My memory isn't very good, but I recall that the A/P commands a nose up trim prior to flare. At least I think that is the NGX.  It's normal to apply a slight forward pressure around 50 AGL or so.


Dan Downs KCRP

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I suspect that when the throttle controller retards thrust for your flare you are overriding it with the above idle throttle position.

 

The other thing I suspect is the spool down time being an issue.  I just did a landing with Flaps 30, I usually use 40 but one of our 737 pilots said they usually use 30, and the increased landing speed made it seem like there was thrust all the way to rotation.  I watched the N1 gages this time and noticed they started winding down to idle below 50 and above 30 AGL but they were still unwinding by the time I started executing the flare. 

 

As an experiment before taxiing to gate, I stood on the brakes and throttled up to 60% N1 then pulled the throttles quickly to idle, I observed a slightly increased amount of decay to idle than in the flare. This makes sense because in the flare the fans had 150 kt wind blowing into them.

 

Landing with the slower speeds afforded by Flaps 40 is much easier, but I am not seeing a problem either way.


Dan Downs KCRP

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I have always been amazed at how the NGX flies a coupled approach in autoland with both autopilots engaged. It flies it with uncanny precision, and I have noticed that with flaps 30 the retard is a lot later than what I do when hand flying.

 

I have also noticed the aiming touchdown point with the flight path vector.

 

From now on I am just going to try to do things as it does.


Alberto Ferracuti

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I found this thread searching for "auto retard B737". I am flying in Steam edition and I too cannot get the AT to retard or shut off on landing. Even if I smash the plane to the ground (for experimental reasons only) and retard the physical throttle it will continue speeding. Not even our beloved PMDG simulation is perfect!

 

So I disconnect at least 100' AGL. Works better anyways. I use the cyan arc to get close to the current AT thrust before I switch off AT. I always get very smooth landings that way.

 

Note that switching off the AT alone has no effect, even if the hardware lever is fully retarded. You have to actually move the hardware to adjust the thrust. 

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I found this thread searching for "auto retard B737". I am flying in Steam edition and I too cannot get the AT to retard or shut off on landing. Even if I smash the plane to the ground (for experimental reasons only) and retard the physical throttle it will continue speeding. Not even our beloved PMDG simulation is perfect!

 

So I disconnect at least 100' AGL. Works better anyways. I use the cyan arc to get close to the current AT thrust before I switch off AT. I always get very smooth landings that way.

 

Note that switching off the AT alone has no effect, even if the hardware lever is fully retarded. You have to actually move the hardware to adjust the thrust. 

 

Full names in your posts please.

 

Are you calibrating you axes through the sim or through FSUIPC?


Kyle Rodgers

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Kyle is suggesting you look at your configuration.  The throttle will retard for landing every time for most users. When you say you have to move the controller to affect thrust it sounds like either a throttle option or an FSUIPC issue.


Dan Downs KCRP

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It's a known fact the autothrottle of the NGX does not mimic the real aircraft (which retards at 27ft) in manual flight. Someone should register a ticket (probably me but I have been too lazy).


It has been discussed and confirmed in page 4 of this thread.


Hans Hjorth

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