Prepar3D Forums

I recently upgraded to v4.4 from 4.3. I loaded my favourite aircraft - the Xtreme Prototypes Learjet 25. But after starting both engines the left one kept spooling down during taxi and it made a take-off impossible. I wondered if it might be a problem with the Saitek Throttle Quadrant so I temporarily switched throttle 1 to a different axis.

The problem remained ruling out a hardware problem. But this aircraft had been fine with v4.3. I thought about what might be responsible. I had updated the client and content only.

I decided to delete the contents of the Shaders folder. This fixed the engine problem but I’m puzzled why it should. Can anyone shed any light on why this cured the problem?

We version the cached shaders, so you shouldn't get 4.3 shaders trying to load in 4.4. If you had any 3rd party add-ons that modified the sahder source, the compiled shaders might have been in a bad state. It's also possible the compiled shader file could have become corrupt if there is hard drive issue or the app was killed in the middle of writing out a file. Finally, we've seen some cases where GPU or driver changes have lead to difference in the compiled shader output. If have issues after swapping out GPUs or updated drivers, it can be good to clear them out.

Thanks Beau. It does sound like it was a corrupted file given it was a 3rd party aircraft that may still have been using a file from 4.3.

The fact there is a link between 3rd party aircraft and the shaders folder suggests the problem lay in that folder.

Happy for you to close this as resolved.