Principia and Firespitter don't play nice: "Why are my helicopters wiggling back and forth like that?"

[Dr.Seuss]

I'm making this topic largely in case someone else comes across the same issue I did, so that they can (potentially) find the answer to their problem sooner rather than later.

The title says it all, basically. Principia, which changes the way physics are handled in KSP, does not play nice with the Firespitter plugin-- specifically, "FSengineBladed" and  "FSbladeLiftSurface". I've looked through the code but I haven't found an obvious source for this incompatibility, but I am certain that it comes from those two classes conflicting with/improperly using Principia's slightly different physics.

In practice this incompatibility manifests basically only with helicopter parts. If you throttle up a helicopter blade while Principia is installed, your helicopter will flop from side to side and bounce up and down like a fish out of water. It's quite funny, actually. Tellingly, the "current force" field of the rotor will always remain at 0. Simply put, the parts won't work for their intended purpose. Remove Principia, and boom- Helicopters can take off, hover, and crash catastrophically into the VAB just as you would expect.

I know for certain that this issue affects the Firespitter rotors, as well as those from "Airplane Plus". Another separate but very similar issue occurs with lifting bodies that use the mod "Hooligan Labs Airships"-- the parts from that mod also bounce about like convulsing fish when you attempt to use them in conjunction with Principia, so I can only assume that something very similar is causing both issues.

At the moment, since my cursory knowledge of unity modding doesn't afford me the ability to really find out what's wrong, and possibly fix it, There's not much that can be done if you find yourself with the same mod conflict. However, on the bright side, in the case of "airplanes plus", many of the parts cause no conflicts: so, you could simply hide the offending parts with something like "Janitor's Closet", and not encounter any problems. Hopefully this little write-up serves to help someone figure out why their helicopters just won't work, without having to check for mod incompatibilities one at a time for hours on end like I did 

[ErikErik]

Hey, I just saw this after scouring the internet for hours to try and figure out why my helicopters don’t fly. Do you perhaps know of any fixes have been for helicopter parts and such have been developed since some time has passed now? Regardless, many thanks for the explanation. 

[Lisias]

This was already diagnosed, and a pull request was issued, however never merged.