Monthly Archives: July 2017

X-Plane 11: Racing the sun at Cunderdin WA

After lengthy delays with some technical and personal health issues, I finally…finally managed to get this latest X-Plane 11 cross-country gliding adventure recorded and edited!

I even managed, after several failed attempts, to eventually upload all two hours of it to YouTube, although I had to split the video into two parts.  Such is the nature of the 2nd rate internet services that we are lumbered with in Australia.

Apart from having some more fun with another virtual gliding adventure in X-Plane 11, my task was intended to be an experiment. My question I wanted to be answered by this task was this:

Can this simulator successfully and convincingly implement a cross-country gliding task of about two hours duration, which is based solely on ‘blue’ (cloudless) thermals?

To answer that, here are the links to the videos on my YouTube channel, and my conclusions and X-Plane 11 settings can be found below.


This was overall another enjoyable flight adventure using X-Plane 11, and that was in spite of some personal pain discomfort at times during the flight. X-Plane continues to surprise and please me with what it can provide to a virtual gliding enthusiast like myself, and it does this regardless of some pretty significant limitations in the modelling of a realistic soaring environment. For example, there are no cloud based thermals in X-Plane. Every glider soaring session in X-Plane 11 is effectively what glider pilots call a “blue” thermal day.  Imagine what a great virtual gliding sim this would be if X-Plane had competition soaring environment functionality similar to that provided by the CumulusX! add-on for FSX.  Blue thermal days are fine occasionally,  and they do occur sometimes in the real-world, but thermals with cumulus clouds on top make for a more tactical cross-country challenge or glider race. Completing a cross-country task without a land-out is less of a lottery with cloud based thermals.


One good thing I can say about the X-Plane 11 thermals is that do appear to be modelled reasonably realistically in terms of their lateral structure. The thermals exhibit a noticeably irregular lift profile when circling in them, making centring on the core quite challenging. I liked this and believe it is much better than the thermals in FSX and Prepar3D, which are too circular in lateral profile. With the weather settings that I used, the X-Plane thermals seemed lumpy and bumpy  – just like the real-world thermals as I remember them.  Also, the lift at the tops of the thermals tapers off reasonably convincingly in X-Plane, but I am still uncertain about whether there is any modelling of the overall vertical lift profile for X-Plane thermals.

There is still some more testing to be done. Some questions about thermal modelling remain in doubt or are still unanswered by just one test task. These include:

Do the thermals exhibit lift weakening close to ground level?

Do the thermals widen and lift become stronger in the upper levels?

Are the life cycles of thermals modelled in any way?


One tick in the box for X-Plane 11 that I can report is that an examination of my flight tracks when circling in thermals indicates that X-Plane seems to be making some attempt to model either thermal lean or drift of thermals in response to the wind.


On the other hand, I have not seen any clear evidence yet that X-Plane 11 thermals might be linked to ground features, nor have I seen confirmation yet that the thermal distribution might be linked to land classes such as large water bodies, forests, built up areas etc.  The land class question might be resolved definitively when I fly future tasks in more diverse areas than was the case at Cunderdin.


One current disappointment is that the X-Plane 11 cloud shadows exhibit a very annoying and distracting flicker on my system, which I cannot seem to get rid of. To get around this problem for this task, I eliminated the lower cloud covering, leaving only the high cirrus layer. The cloud shadows from the cirrus layer still flicker but are less noticeable due to the lighter shading from these high level and thinner clouds.  Since recording this flight, I have found a plugin that allows me to make all cloud shadows totally transparent, effectively hiding cloud shadows, so that this problem does not irritate me. Nevertheless, I would like to have visible cloud shadows that do not flicker – so I am still looking for a better solution to this problem.


The flight plan is a 160 kilometre triangle based on a real-world task at Cunderdin in Western Australia. The original task was flown by Luke Dodd in an Astir CS sailplane in 2000. For my own convenience, I chose not to convert the task turn point coordinates, and instead, I modified the turn points slightly, placing them over the grain elevator structures at Kellerberrin and Wyalkatchem. Also I placed the start and finish lines over the glider clubhouse at Cunderdin airfield with an arbitrary maximum start height of 6,000 feet MSL and a minimum safe finish height of 500 feet AGL.  My chosen start and finish line height limits are typical of the limits set for UK Virtual Gliding Association tasks.

The Plan-G flight planner shows that I should be able to complete the task in under two hours if I can achieve a task average speed of 83 kph or better. As the 2-part video above shows, I completed the task faster than that and was able to land and park the glider before the sun set.

Flight Plan

Flight Plan (click to enlarge)



For this task, I setup for an aerotow launch from Cunderdin, Western Australia on runway 32 at 15:50 local time on a sunny autumn (fall) afternoon. My intention was to release at 3,000 feet AGL, climb to the maximum start height of 6,000 feet before crossing the start line, hopefully by about 16:00. This would give me about two and quarter hours to complete the task before the sun sets. I felt that this would give some incentive to keep pushing harder, in effect a race against the sun, rather than having me taking it too cautiously and cruising around the course at the best L/D speed.


Airfield (click to enlarge)



Time and Date

Time and Date (click to enlarge)



Atmospheric Conditions

Atmospheric Conditions (click to enlarge)

Cloud Layer 1

Cloud Layer 1 (click to enlarge)

Wind layer 1

Wind layer 1 (click to enlarge)

Wind layer 2

Wind layer 2 (click to enlarge)


Wind Layer 3

Wind Layer 3 (click to enlarge)