Klish

First of all, thank you for this mod, it’s always the first one I look for when a new update rolls out! I have two potential bugs to report, which I could not find prior record of. In my hard, 100+ mod career game, I had an early jet plane could not take off, as it insisted on spinning out on flat ground around 50-80m/s with no control input. The stability derivatives were all green at the default Mach 0.35, but in the 0.15-0.20 range, several turned red, including Xu. The cheatsheet I’ve written down from some of the guides on this forum says that positive Xu means there is a bug. Figuring another mod might be an issue, I downloaded a fresh install of KSP and manually installed FAR (and the dependencies) from SpaceDock. The craft still had the issue and I started playing with individual parts to isolate it. I have found that there are several parts that appear to have a positive Xu at Mach 0.35 when initially placed, including the spaceplane cockpits, some landing gear, and cargo bays (not an exhaustive list). It will become appropriately negative if the parts are rotated. They all seem to seem to be parts with aerodynamic shapes/small cross sections perpendicular to the direction of travel so I would expect drag increase with increased speed to be small, but not for it to be the inverse! However, I am not an aerodynamic expert like you are, perhaps this is somehow expected behavior, or perhaps something wrong with just my computer? As a result of this toying around, I have also found that the SPH FAR window will freeze, go blank, and requiring exiting and re-entering the building if you ask it to calculate stability derivatives when there are no parts placed. I know that most people don’t build single part planes or calculate the stability derivatives of nonexistent parts. However, in the first case, adding more parts doesn’t seem to fix the issue, only mask it by outnumbering the bad parts with good ones, which can lead to problems with small planes and at low speeds. Thank you again for your continual work on this mod, and let me know if you need any more info!