ThinkInvisible

FAR seems to have solved the problem; there's still a little instability, but it's very manageable. FAR did steal most of my lift, but a redesign fixed that, including less of a massive nuclear reactor, comically oversized blades, and removal of the wings and tail fin. The thing isn't unbearable to fly anymore, and it goes surprisingly fast for something that looks so awkward - I managed ~30m/s before I found the ocean and decided not to fly over it. It seems to be impossible to control individual blade pitch like that with just Infernal Robotics's default controls (each blade would need its own keys!); I'd need to use something like kOS and get a computer to do it for me, which I've been meaning to figure out someday (but not today). This particular helicopter just uses gyroscopes to push the nose around directly, and the addition of FAR seems to be enough to make that work.

So I made a coaxial-rotor helicopter with Infernal Robotics parts and TweakScale (as shown above), and it's being very contrary. Both rotors are directly above the center of mass; both rotate with constant and opposite speed, and lift is controlled by tilting the blades. As it stands, I'm just using reaction wheels to control rotation (and thus movement) of this vehicle, since I don't know of any other way to do this. Something on this vehicle seems to be resisting any movement that isn't straight up or down. If I pitch the vehicle down in an attempt to move forwards, it works for a few seconds before the nose starts being forced back up (and slightly to the right, roll only). The wings and tail fin were added as a response to this problem, but they don't seem to help too much. With SAS disengaged, the vehicle also seems to be very stable with respect to yaw and roll, but it begins pitching uncontrollably and wildly (going from pointing straight down to straight up and back, repeatedly) if left alone. It seems like a similar oscillation can be induced with roll by moving left or right for more than a few seconds before trying to come to a stop. What could cause a helicopter to act this way? Am I missing some kind of critical control surface? Also, is there any way to control a helicopter like this without rotating the entire vehicle?