Category Archives: Prepar3D V4

Getting CumulusX! to work in Prepar3D V4


In a comment on my YouTube channel, I was asked how I was able to make CumulusX! work in P3D V4.  CumulusX.exe is a 32 bit application for FSX and not supported in P3D. Because my answer was somewhat complicated, I thought it would be easier to explain in my blog rather than in a YouTube comment. Also, as a blog post it might be useful to a broader audience.

Note that I have FSX Steam Edition installed on my P3D flight sim PC, so my experience might be different to yours if you do not have FSX installed.  In particular, you may find it difficult get the CumulusX! smart tow feature working without first configuring it in FSX – but more on that later.

BTW: The partner application WinchX! works fine with P3D V4, although I had to manually add the code to load it automatically in my exe.xml file.

I installed CumulusX! manually into P3DV4 and  I am very happy so far with the way that it is working, both standalone and in multiplayer flight sessions.  However, I did not keep any notes on the installation procedure that I used, so I am relying on my memory to describe the steps taken. If you plan to follow my steps on your system, do so at your own risk and make backups of everything that you modify.

Step 1.  I copied the “CumulusX!” sub-folder and its contents from the “Modules” sub-folder in the CumulusX! installation package into my P3D “Modules” sub-folder.  Note that CumulusXDLL.dll library is 32 bit and will not work with P3DV4 but my experience suggests that this dll is not required.  So I do not bother trying to load it with P3D V4. In FSX and 32 bit versions of P3D you would normally load it with an entry in your DLL.xml file. The 32 bit CumulusX!.exe file is a standalone application and works fine with P3D V4. Since there is no installer for P3D, I manually added the required code to my Prepar3D exe.xml file – this is covered in step 3 below.

Step 2. I copied the “SimObjects” sub-folder and its contents from the “SimObjects” sub-folder in the CumulusX! installation package and merged it into my P3D “SimObjects” sub-folder. These new miscellaneous SimObjects are needed to create the CumulusX! thermal clouds.

Step 3. I manually added the following lines to:  C:\Users\jfall\AppData\Roaming\Lockheed Martin\Prepar3D v4\exe.xml after making a backup.  Note that I set the “ManualLoad” option to True so that I am prompted and can choose to load CumulusX!, or not, each time that I start a P3D session. You may choose to set this option to “False” if you want CumulusX! to automatically start with every flight. You can always shut the application down later if you don’t need it.  I only use CumulusX! for glider flights because I don’t like the CumulusX! cloud textures, although I can to some degree conceal them among the standard P3D cumulus cloud textures. Also, for powered GA flights I usually prefer to use Active Sky lift and sink features instead of CumulusX!.  On the other hand, when I want to use Active Sky with CumulusX! for a glider flight, I set the lift and sink values in Active Sky wind settings to zero so that they do not conflict with CumulusX! lift and sink.

Note that you can also manually start CumulusX! after starting the sim by double clicking on the CumulusX!.exe file if you don’t want to modify your exe.xml file.

You will find exe.xml in:

C:\Users\<your login name>\AppData\Roaming\Lockheed Martin\Prepar3D V4

Here are the lines added to my exe.xml file, but you must change the path statement to match your own system:

<Path>P:\Prepar3D v4\Modules\CumulusX!\CumulusX.exe</Path>


Step 4. We must prevent the creation of the default P3DV4  thermals, which will conflict with the CumulusX! thermals. To do this I made a backup copy of the ThermalDescriptions.xml file in C:\ProgramData\Lockheed Martin\Prepar3D v4.  I then replaced the ThermalDescriptions.xml file with the following content:

<?xml version=”1.0″?>
<SimBase.Document Type=”AceXML” version=”1,0″ id=”AirObjectVisuals”>
<Descr>AceXML Document</Descr>

<!– Thermal Types –>
<!– 00 Null thermal – For non-thermal areas –>
<!– 01 Damp Green Areas – Medium-large diameter short slow non-tubulent –>
<!– 02 Isolated Rock – Smallish Sharp fast turbulant high –>
<!– 03 Large Hot Area – desert, dense urban Large rough turbulant fast and high –>
<!– 04 Small Hot Area – dirt fields, small urban – Slightly smaller for rural area –>
<!– 05 Grassy Areas – Wide medium strength medium turbulance and semi-low –>
<!– 06 Cool Forests – Small to large, slow to fast, low to medium –>
<!– 07 Warm Forests – medium to large, medium to fast, medium to high –>
<!– 08 Semi-Arid – Wide and medium to fast and high –>
<!– 09 Big Mountain – Fast rowdy high for mountain air –>
<!– 10 Wetlands and Lakes – Mild Sink Large flat smooth slowly sinking air. –>

<!– 00 Null Thermal  –>
<ThermalDescription id=”{4f5e0000-1e81-11db-9897-001372201444}”>

Note that you cannot simply delete or rename the ThermalDescriptions.xml file because P3D V4 will replace it on startup.

Step 5. The Smart Tow Plane configuration menu in CumulusX! does not seem to work properly with P3D. I think it tries to update the FSX.cfg file instead of Prepar3D.cfg. To get the smart tow feature configured the way I like it with the aircraft model of my choice, I configured it first in FSX first then copied the “[SIM]” configuration lines from FSX.cfg to Prepar3D.cfg.  Naturally, I had to install the same tow plane model in both sims. I am fairly sure that I was able to configure the tow plane speed in P3D itself but if I am wrong then the default speed is working OK.  These are the SIM config  lines that I added to my Prepa3D.cfg file – yours may be different:

TowPlaneTitle=PA36 Pawnee Brave 375 N55128 (Without Dispersal Equipment)

I suppose that if you do not have FSX installed, you could try and  change, or add,  the [SIM]  entry shown above into your Prepar3D.cfg file and change the TowPlaneTitle to your tow plane of choice, and  see if that works. You could then use trial and error to find a suitable TowPlanePitch value – note that it is a negative value.

Do not forget that you can ask for help and advice from Peter Lürkens and other CumulusX! users on the Aerosoft forums, although keep in mind that CumulusX! is not supported in P3D and you will need sign up if you do not already have an Aerosoft forums account. Here is the link to the CumulusX! topic:

Also help and advice is available for CumulusX! and virtual gliding issues in general on the UK Virtual Gliding Association  forum (membership of the association is free, although donations are welcome.) Our members mainly use FSX but many have experience with P3D, X-Plane and Condor.

CumulusX! has an excellent and detailed manual. You can find it online or in the Manual sub-folder in the CumulusX! folder. I recommend that you read it at least five times if you want to get the most out of this outstanding add-on. CumulusX! also comes with some example configuration files (.cmx), so try them out. In particular, if you are just getting started with CumulusX!, try the Beginner.cmx configuration.

Prepar3D V4 Nephi 100 Km triangle glider speed challenge


This flight adventure was my attempt, using Prepar3D V4, to emulate a real-world gliding speed challenge.  My P3D flight was inspired by one of Bruno Vassel’s excellent YouTube videos (see links below).  In that video, Bruno broke the Utah 100 km triangle speed record of 95.2 mph set back in 2003 by flying an average 100.23 mph (162 km/h) in a Schleicher ASW 27b glider on the 5th August 2017 at Nephi, Utah (u14).

Link to Bruno’s speed challenge flight video:
Link to Bruno’s YouTube channel (highly recommended):

My YouTube flight:

To emulate Bruno Vassel’s real-world speed challenge in a somewhat convincing way, I undertook the following actions and configuration settings:

Task replication: I replicated Bruno’s flight task by extracting the waypoint data from the IGC logfile captured on Bruno’s flight, and then converted the data to an FSX flight plan using a Python script that I had developed.

This is the resultant flight plan in Little Navmap:

Flight Plan


Choice of glider model: The choice of glider model was easy.  I used the ASW27b model from Wolfgang Piper’s collection of freeware gliders for FSX and P3D. This matches up nicely with Bruno’s glider, although there are likely some differences due to limitations in the simulator flight modelling.

Link to Wolfgang Pipers website:


Payload and ballast settings: To maximise my cruise speed performance, I set the payload and ballast in P3D to give the maximum take-off payload of 500 kg.  I also set the pilot weight and ballast to bring the centre of gravity slightly forward of default to improve high speed trimming as shown in the following snapshot:



Weather settings: To approximate the weather conditions of Bruno’s flight, I initially explored the possibility of using Active Sky 2016 (AS16) to inject historical weather directly into the sim. The problem with that approach was that the AS16 add-on chose stratus clouds when the historical meta data left the lower cloud layer type unspecified and the soaring environment add-on (CumulusX!) will not produce thermals when stratus clouds are present in the lowest cloud layer.

To get around that problem, I tried using a snapshot of the historical weather in manual mode and then changed the cloud type to cumulus but then I ran into other problems.  Firstly the upper level wind layers had enough wind shear to make thermalling in the simulator almost impossible. Also AS16 seemed to generate too many clouds for the specified cloud coverage, which did not look anything like the real-world conditions seen in Bruno’s video. Moreover, the extra clouds exacerbated performance issues that I have been experiencing lately in my simulator.

In the end, I decided to use the historical data from AS16 as a guide for manually creating a weather scenario using the advanced weather settings in Prepar3D. I tried to copy the AS16 reported weather conditions as closely as possible but I did modify the upper wind layers a little to reduce the wind shear to more modest levels.  I also reduced the reported visibility to better match the cloud haze visible in Bruno’s video because this visibility issue had not been reported in the AS16 historical weather data. Plus I elliminated the lower level cloud layer completely, relying instead on clouds generated by the CumulusX! add-on in ‘Unblue’ mode. I added a high-level cirrus cloud layer for purely cosmetic reasons.






Soaring environment configuration: To create a convincing soaring environment (thermals) consistent with the conditions evident in Bruno’s flight video, I configured CumulusX! as shown in the following snapshot. Note also, that I was using ‘blue’ thermals (i.e. no cumulus cloud layer in P3D) and I had the ’Unblue’ option in the CumulusX! Help menu ticked. This was done, partly because my P3D installation did not seem to represent a 2/8 or less cloud coverage accurately, and also because reducing the cloud coverage helped with some performance issues that I have been experiencing lately.  Unfortunately, the CumulusX! cloud textures looked awful.

Link to CumulusX! competition soaring environment add-on:



While I fell well short of the Utah 100 km speed record (only 95.88 mph as against 100.23 mph) in my attempt, I nevertheless enjoyed this speed challenge immensely.  I felt pressured all the way around the set course, trying to balance minimum arrival height against the need to achieve a task average speed greater than 100 mph.  I am convinced that a speed challenge, such as this, can be equally entertaining as any race against other gliders in a multiplayer event.



My task result in SeeYou:


My flight path in Little Navmap:

Flight path