P3D Ground friction with FSX Add-ons...

[Andrew Hansen 37]

Hello,

 

I've been using the professional version of Prepar3d for a little over two weeks now.    So far I've successfully ported over two of my FSX add-on planes:  the PMDG 737NGX and the Lotus L-39.  

 

I installed the Lotus L-39 into P3D via the regular installer, while I manually copied my PMDG NGX files from my FSX installation.     I run P3D in legacy mode (renaming the .exe) to accommodate EZCA and Tileproxy, both of which work fine in Prepar3d.       Both the NGX and L-39 load fine and seem to function correctly while running P3D in legacy mode.    

 

I am noticing that both the 737NGX and the L-39 require significantly more thrust to taxi when installed in P3D.     The 737NGX requires about 10 percent more thrust to achieve the same taxi performance in P3D as compared to my FSX installation, assuming the same weights and conditions.       Similarly, the L-39 requires quite a bit more thrust to taxi and maneuver as opposed to the way it performs in FSX.       Has anyone else noticed the same thing on your P3D setup with these aircraft or others?     

 

I'm wondering if there are subtle changes in flight dynamics modeling implemented with Prepar3d that would explain my experience?    Takeoff distances with both the Lotus L-39 and PMDG 737 are also greater in P3D than FSX, assuming both the same weight and density altitude conditions for each aircraft.    This of course would be attributable to a change in ground friction modeling between the two versions of Flight Simulator/P3D.     I am also noticing stopping distances have decreased significantly for both aircraft in my P3D installation, again attributable to differences in ground friction modeling between P3D and FSX.    

 

I have a registered version of FSUIPC 4.92 installed into P3D, but I do not use the ground friction variable option or a .lua file that modifies ground friction in Prepar3D.

 

Thank you for any insight.    

 

-Andrew

 

[jcomm 5,889]

Andrew,

 

and, weren't you using that LUA script in FSX? That would explain the difference :-)

 

I used the "Dynamic Friction" script with P3D and it worked ok. Do exactly the same as with FSX to make it operational.

[Andrew Hansen 37]

Andrew,

 

and, weren't you using that LUA script in FSX? That would explain the difference :-)

 

I used the "Dynamic Friction" script with P3D and it worked ok. Do exactly the same as with FSX to make it operational.

 

 

Hi JC,

 

I meant to clarify that I am not using any any kind of friction modification for either FSX or P3D; both sims are running stock ground friction without any FSUIPC intervention or script.      This is so weird!      I haven't come across any other threads with P3D users reporting the same thing experience with ground friction, yet I noticed it right off when I installed both of these aircraft into P3D.      I also double checked all my controllers to make sure nothing could have been sending inadvertent braking input.

 

PMDG actually did amazingly well with whatever mod they used to achieve correct ground friction with the 737NGX in FSX.     At lighter weights in FSX, using the 737NGX, once you use enough thrust to establish normal taxi speed, you can pretty much idle the throttles and maintain your momentum.      Not so in P3D, at least from my experience.      Also, in FSX with the 737NGX, at high weights you can taxi with a max power setting need of 30 percent N1 or below.      In P3D under the same conditions, I have to use anywhere from 40 to 50 percent N1 to maintain the same taxi speed.        

 

Scratching my head with this one!    :huh:   

[jcomm 5,889]

Well, then is really puzzles me as well :-/

 

I do not have FSX installed. When I installed P3D I did find that by default the brakes ( in my controller ) could be inadvertently applied because the Axis sensitivity and null zones were all wrong, but then the "brakes" or "differential brakes" red tags would appear in the lower right corner of the display (?).

 

When I had both sims installed I was never able to detect such a difference between FSx and P3D, and I have the PMDG 737 NGX, as well as Aerosoft's AXE.

 

I will try to find out more about this and will report what I have found!

[Andrew Hansen 37]

Thanks JC!     I tried completely disabling FSUIPC in P3D, but experienced the same inexplicable ground friction, so I can rule any kind of interference with that out.    HOWEVER, I went back and ran P3D via the original Prepar3D.exe rather than my renamed to FSX.exe file (to run P3D in legacy mode), and guess what?      The excess ground friction problem magically went away.      :blink:

 

What the monkey hey ho I wonder why.      The FSX.exe is simply the original Prepar3d.exe renamed to facilitate compatibility with older FSX add-ons like EZCA.      But what in the world would cause a renamed .exe to affect flight dynamics???     The plot thickens, but we're on to something at least, haha.   

 

The only thing I canz speculate on is the presence of a file in my P3D root directory named, "Prepar3D.exe.config".       Dissecting this file via Windows notepad, we find that it's directing the loading of certain .NET Framework files:

 

<?xml version="1.0"?>
<configuration>
  <startup useLegacyV2RuntimeActivationPolicy="true">
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>
  </startup>
</configuration>

 

Upon renaming my original Prepar3d.exe to FSX.exe, and thereafter running this renamed file to start P3D (stay with me here), I'm thinking that the above "Prepar3D.exe.config" is being bypassed and the .NET stuff above not being loaded properly is causing something weird to happen with the flight dynamics.     I will admit this seems a bit of a shot in the dark, but I can verify running the original unrenamed Prepar3d.exe file makes the excess ground friction problem go away.     :blink:

 

I will try renaming "Prepar3D.exe.config" to "FSX.exe.config" and then running P3D via the renamed FSX.exe file and see what happens.    Wish me luck - I'll report back (if I survive the attempt).    

[jcomm 5,889]

Thx for the precious report!

 

I am about to try to install FSX stuff on P3D, without having FSX installed, and without using the EMT... So, any findings in this area are welcomed!!!!

[kand 205]

you can try opening up the p3d sim1.dll in a hex editor and view the settings? there is an excel here which lists the offsets to check and explains the scalars, make sure you set your hex editor to decimal when viewing the scalars

[Andrew Hansen 37]

Ok, it now appears I've solved the problem.     Yay me!    

 

Conclusion - If you rename your Prepar3D.exe to FSX.exe (in order to run your old FSX add-ons properly), you apparently also need to additionally rename the following files in your Lockheed Martin/Prepar3D root folder or you may experience flight dynamics anomalies (like excessive ground friction):

 

"Prepar3D.exe.config" - copy and rename to "FSX.exe.config"

"Prepar3D.exe.manifest" - copy and rename to "FSX.exe.manifest"

 

Don't ask me why, don't ask me how, but if the above files are bypassed during initial P3D load-up by failing to rename them in the prescribed manner,  ground friction with add-on FSX aircraft is somehow messed up.      All of this at least from my own personal experience with my particular installation.     Your mileage may vary.          Again, this only applies to those of us who have renamed their .exe files in their P3D installation.  

 

Thanks for everyone's input and I hope this might help someone else out.    

you can try opening up the p3d sim1.dll in a hex editor and view the settings? there is an excel here which lists the offsets to check and explains the scalars, make sure you set your hex editor to decimal when viewing the scalars

 

Hi Kand,

 

Actually a very smart idea and I was originally thinking along the same lines before I came up with the ultimate solution (which I posted above in this thread).      I even tried to be extra-sneaky and copied my FSX sim1.dll into my P3D root directory (after copying the P3D original and renaming it), but P3D refused to load it and would not start.      Thanks for your input!

[jcomm 5,889]

 

 

Conclusion - If you rename your Prepar3D.exe to FSX.exe (in order to run your old FSX add-ons properly), you apparently also need to additionally rename the following files in your Lockheed Martin/Prepar3D root folder or you may experience flight dynamics anomalies (like excessive ground friction):
 
"Prepar3D.exe.config" - copy and rename to "FSX.exe.config"
"Prepar3D.exe.manifest" - copy and rename to "FSX.exe.manifest"

 

Precious info Andrew! Thx!