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alexzar14

throttles don't retard on landing, P3D

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There are several things that bug me about the PMDG 737-800. This AT issue is among my biggest peeves. Also chief among them is the fact the LNAV will not automatically arm for go-arounds.

Check Page 87 of the NGX intro manual. I just found this now, and wonder if this may be the issue for landing and power.  

 

 

SHOW THRUST LEVER POS: When the airplane is being flown using auto-throttle, the throttle position quickly gets out-of-sync with the position of your joystick throttle. This can create an uncomfortable change in thrust when you disconnect the auto-throttle on approach or immediately prior to landing. In order to eliminate the need for you to quickly adjust your throttles to avoid a thrust change we have devised a system that will allow you to easily sync your throttle position to the auto-throttle position:

By selecting Show Thrust Lever Position to ON, you will notice that moving your throttles while the auto-throttles are engaged will cause a small cyan marker to appear on the inside of the engine N1 thrust rings on the upper engine display unit. The cyan mark is showing you the current position of your joystick throttle. Simply put the cyan mark to the same location as the white throttle tick mark displayed on the same arc, and you will have your throttles properly synchronized with the current auto-throttle setting.

This feature is a PMDG feature and has nothing to do with the real jet. I understand why it's available but I do not use it due to the lack of realism.

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I did several flights in P3D with throttles in AT mode retarding themselves just before touch down (always had it in FSX too).

Now another flight and this didn't happen, the thrust was on after touchdown trying to maintain Vref (135 it was). I tried the approach 3 more times (I have FSUIPC saving flight every 30 seconds) and every landing I experienced the same thing: no throttle retardation. I am panicking now... seriously panicking, please help.

 

...my CH thrust levers were retarded.

 

This is a known issue if the A/T is off

Vernon Howells

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The ALWAYS option in no way applies to landing. Here's an example of how having it unchecked affected me. Prior to checking the option, used to push my hardware throttles to the max forward position after engaging TOGA and leave them there. During descent when the AT would reduce thrust to idle and go into ARM mode, the software would look at the position of the hardware throttles and advance the sim throttles to max to match the hardware throttle position. For reasons I never fully understood or researched, I would not have control over the sim throttles. After checking the ALWAYS option, I pull my hardware throttles back to idle after engaging TOGA on takeoff. This way, when the AT reduce thrust to idle during descent and enter ARM Mode, they stay at idle and also allow me to manually control thrust if needed as described in my previous post. I have never been able to discover why the AT don't retard to idle during the flare in landing.

 

Incidentally, the Airbus crash you mentioned above did not occur on the first flight. That flight was conducted at an airshow and had nearly 100 journalist and various VIPs on board. Most survived. I believe 2 lives were lost.

 

 

That is what I have been doing, Throttles full forward, engage Toga, and leave throttles full forward until AT is disengaged and then retard throttles. I think this is where the issue occurs, since AT disconnect then results in engines spooling up to full throttle until I can yank the throttle levers back. Using the show thrust lever position, which I was totally unaware of till now, will get the throttle adjusted so that at AP disconnect, there should be no appreciable change in thrust, since the throttle will already be set at whatever the AT was commanding. Going to try it on next flight. 


 

Bob Cardone        MSFS 2020       FlyVirtual.net   Aivlasoft EFB2  /pf3-supporter.gif

 

 

 

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Well I used the procedure I mentioned above of utilizing "show thrust lever position" and reduced the thrust setting on my throttle, as I approached the runway to match the indication on the N1 thrust rings. When I landed, the AT cut off, and I got no surge in thrust and touched down exactly at Vref right on the touchdown zone.. It worked perfectly.  :smile:


 

Bob Cardone        MSFS 2020       FlyVirtual.net   Aivlasoft EFB2  /pf3-supporter.gif

 

 

 

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Well I used the procedure I mentioned above of utilizing "show thrust lever position" and reduced the thrust setting on my throttle, as I approached the runway to match the indication on the N1 thrust rings. When I landed, the AT cut off, and I got no surge in thrust and touched down exactly at Vref right on the touchdown zone.. It worked perfectly.  :smile:

That was WITH the AT disengaged at 100ft? I do basically what you described above. I don't use the "show thrust lever position" indication but instead simply place the thrust levers approximately where I know they should be, disengage the AT and quickly adjust to match. You can hear a change in N1 if not matched.

 

I'd still like to see that AT close automatically on landing as in the real jet.

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That was WITH the AT disengaged at 100ft? I do basically what you described above. I don't use the "show thrust lever position" indication but instead simply place the thrust levers approximately where I know they should be, disengage the AT and quickly adjust to match. You can hear a change in N1 if not matched.

 

I'd still like to see that AT close automatically on landing as in the real jet.

 

I am not sure when exactly the AT disengaged, but it did disengage. I was staring at the engine gauges during landing so I missed the switch off point. I will note the disengage point next time, but I think the way to get this to work, as you said, is to set the throttle on short final so that when  the AT switches off, that the throttle setting is close to the same power  setting that the AT is commanding at the time of AT disengagement . if the throttle is set too high, when the AT switches  off, the result is an engine power surge which messes up the flare.  


 

Bob Cardone        MSFS 2020       FlyVirtual.net   Aivlasoft EFB2  /pf3-supporter.gif

 

 

 

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So what's the solution? Why do throttles cut in FSX and not in P3D?

 

Initially it did cut in P3D too, I happened to save an approach of one of the early flights I did in P3D (it was CYYZ 33R) and I just tried the saved approach again and bingo - it retarded! I tried this approach 4 times, it retarded every time. Some parameters were saved in that flight I guess...

As said above, the modern plane like NGX does have an auto-retard as the 777, it is upsetting having to land it like a 737-200 in the P3D.


Alexander Zar

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What are use trying to do? Land manually with the A/T on?


Vernon Howells

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What are use trying to do? Land manually with the A/T on?

The theme of this thread is the fact that the AT, if engaged while landing, regardless of autopilot or flight director engagement, should close below 27ft RA during landing as in the real jet. They do not in the PMDG 737.

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The theme of this thread is the fact that the AT, if engaged while landing, regardless of autopilot or flight director engagement, should close below 27ft RA during landing as in the real jet. They do not in the PMDG 737.

 

I tried doing this with A/P off and autothrottle on. On the FMA it shows RETARD and the throttles come back but stay slightly above idle. Mean while the N1% stays at approach idle.

 

If you try it with autothrottle off and ap off the same happens the 737 NGX throttles stay above idle.

 

This is a P3D/FSX limitation and PMDG know about this


Vernon Howells

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I tried doing this with A/P off and autothrottle on. On the FMA it shows RETARD and the throttles come back but stay slightly above idle. Mean while the N1% stays at approach idle.

If you try it with autothrottle off and ap off the same happens the 737 NGX throttles stay above idle.

This is a P3D/FSX limitation and PMDG know about this

I figured they knew about it. They don't miss much! I do wish they would get us a FANS MCDU. That's what we have installed in the fleet at my company. It's akin to the B777 CDU, which I believe IS a FANS MCDU.

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Can only report it works fine for me using P3D V3.2

 

Can you be more specific and describe what "works fine" means? 

 

1. Are you leaving AT on during the flare?

2. When does AT switch off, altitude wise?

3. Do throttles go to idle at switch off? 

4. What is the setting of AT options in the simulation setting of the 737? Always, never, or retard and hold? 


 

Bob Cardone        MSFS 2020       FlyVirtual.net   Aivlasoft EFB2  /pf3-supporter.gif

 

 

 

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