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Stutter at 30 feet AGL with PMDG 747 Autoland

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SleepyWeltonBoy View Drop Down
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Joined: March-28-2013
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SleepyWeltonBoy Quote  Post ReplyReply Direct Link To This Post Topic: Stutter at 30 feet AGL with PMDG 747 Autoland
    Posted: December-07-2017 at 12:01pm
I am experiencing a strange issue with the PMDG 747 during an autoland on a 8nm approach. At about 30 feet AGL (above ground level), a very noticeable stutter occurs. If I fly a LH pattern and setup an autoland on the approach, the stutter is not present. I have approached PMDG with a ticket and they feel it could be a corruption with saved states and added they are working on a fix. That said, it does not explain why these cases behaved differently, other than the FMC is used rather differently in the former compared with the latter, i.e. in the latter (a LH pattern), the FMC actually reflects the flightplan flown, whereas in the former I believe that J-P uses some wizardry to fill the appropriate pages accordingly such that the approach can be flown.
 
Note that the problem does not occur with the PMDG 777 and also it only relates to autoland. I have observed that by hand-flying the approach from about e.g. 400-500 AGL, then the stutter does not occur. Any thoughts here, J-P?
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SleepyWeltonBoy View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SleepyWeltonBoy Quote  Post ReplyReply Direct Link To This Post Posted: December-08-2017 at 1:34pm
Some progress with this issue. If I choose, for example, a LH pattern and load everything on the ground using FSiPanel, and then use other software to position the aircraft on e.g. a 8nm final (appropriate to the destination airport of the LH pattern loaded into the FMC), the autoland is flown without hitch and no stutter at 30 feet. Effectively what I have done is to remove considerations of the route that would be loaded by default into the FMC by FSiPanel for e.g. a 8nm final (and obviously bogus with the exception of the ILS frequency!) and use instead that created by setting up the LH pattern within FSiPanel itself. This does require additional setting up by the user and of course you do lose the post-landing analysis within FSiPanel itself.
This is a workaround for me until the issue can be nailed and clearly non-ideal on account of the use of other software in combination with FSiPanel.
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J-P Garraio View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote J-P Garraio Quote  Post ReplyReply Direct Link To This Post Posted: December-08-2017 at 8:54pm
Hi.

I just tried several approaches with Autoland and didn't get any problem at all..

Which SIM are you using? 747 livery?

I will try again with the exact same settings as yours.

Have you tried importing a new 747 into FSiPanel?

Cheers,

J-P
FSiPanel for FSX
www.fsipanel.com
Jean-Pierre Garraio
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SleepyWeltonBoy View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SleepyWeltonBoy Quote  Post ReplyReply Direct Link To This Post Posted: December-09-2017 at 6:23am
Hi J-P,
 
Thanks for your checking of the issue that I am experiencing. I have just completely reinstalled P3D v3.4 after a clean uninstall and reinstalled the PMDG 747 QOTS II; the problem is still there.
 
Rather stumped at this point but will continue to liaise with PMDG until we nail down the cause of this issue.
 
Many thanks in the meantime (hopefully the problem does not occur in P3D v4!).  
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SleepyWeltonBoy View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SleepyWeltonBoy Quote  Post ReplyReply Direct Link To This Post Posted: December-09-2017 at 5:56pm
As an experiment, I completely reinstalled Windows 10 on a spare disk together with P3D 3.4 and the PMDG 747 and the problem is still there between 50 and 30 feet. All installations to the book including that of FSiPanel. No tweaks have been done to the Prepar3D.cfg file.
 
I had suspected an issue with aircraft landing lights etc. on account of night landings exhibiting different behaviour, e.g. stutter at 100 feet AGL and NO stutter at approx. 30 feet AGL. As an experiment, I switched off ALL aircraft lights (landing and everything else). Lo and behold, NO stutters both in day and night approaches.
 
I am not sure where to go with this but will report back to PMDG with my findings for their information. It could be a problem related to reflectivity (or not) of aircraft lights on the ground which is causing this issue. It is puzzling that the PMDG 777 does not seem to exhibit this behaviour so it could be related to only the 747. I am not convinced that this issue is widespread and could only be confined to the use of FSiPanel with the 747 for approaches which do not require a definite flightplan to operate with and program the FMC (I have already pointed out that I have tried successfully a LH pattern whereby no stutter had occurred). If PMDG cannot bottom this one out, I am just wondering whether or not the loaded aircraft in FSiPanel has somehow become corrupted and this manifests itself in this aircraft light reflectivity issue in close proximity to the ground. More particularly at night, it could be that the landing lights reflect off the ground at about 100 feet AGL and hence the stutter, whereas in daylight the landing lights might only reflect at rather closer distances above the ground, e.g. between 50 and 30 feet AGL.
 
Anyway, perseverance has paid for me and at least I can carry on using FSiPanel with my workaround. I shall post any thoughts from PMDG as soon as I get a response and it could be that the PMDG modelling needs fixing for the 747 for such issues.
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SleepyWeltonBoy View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SleepyWeltonBoy Quote  Post ReplyReply Direct Link To This Post Posted: December-16-2017 at 4:01pm

I have finally found a workaround within FSiPanel which eliminates the stutters and does not require switching off all external aircraft lights. Firstly, having saved the situation for the PMDG 747 in FSiPanel, fix the aircraft on the runway to be flown towards on the approach from within FSiPanel. Make sure that the FMC is programmed accordingly for the aircraft weight etc. Also, ensure that the altitude and speed are set appropriately for the approach. Next begin a takeoff along the runway to about the approach speed then pause the sim (no need to get airborne). Exit FSiPanel.

The next bit involves saving the PMDG 747 as a basic aircraft (yes, that is correct!) in FSiPanel and then moving the newly saved basic aircraft to the position for the approach to be flown. Be sure to select the APP button and autopilot and also that the speed is held at the approach speed itself and controlled for the approach when the pause is released.
 
Fly the approach and the experience is stutter-free. The above is only necessary for the PMDG 747 in my case and does not seem to be necessary for any other product.
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