Coaxial rotor

Ka-27/29/32, Ka-50/52. Can be described, not flight-tested yet.

Same as the tandem, nobody's flown one of these on RFM yet, so treat it as a starting point.

How a coaxial flies. Two rotors on one mast turn opposite ways. Yaw comes from differential collective. One rotor gets a bit more pitch and the other a bit less, so their torques stop cancelling and the aircraft turns. Pitch and roll use the same cyclic on both rotors.

Steps:

1. Power group. One or two sources. Outputs shaft.upper and shaft.lower, both role 1, ratio 1, each with its rotor's inertia.
2. Rotor units. rotor.upper and rotor.lower, both role 1, opposite Spin Direction. Both hubs share the same X and Z, with the upper hub higher by the real rotor spacing. Use two PointInfos or two bones.
3. Control maps. Both use the default collective and cyclic. Add Collective From Yaw of about +0.08 on one and −0.08 on the other, and swap the signs if the pedals come out backwards. If the cyclic on the rotor spinning the other way comes out mirrored, flip that rotor's Cyclic Long Sign or Cyclic Lat Sign.
4. Wake link. rotor.upper → rotor.lower, gain 1. The lower rotor works in the upper one's downwash, which is the big aerodynamic thing about a coaxial.
5. Fins and rudders. Kamovs have twin fins with rudders. Put one fin in the Fin slot and the other in Extra Surfaces with Vertical ticked. Give each one Incidence Per Yaw Deg so the pedals work as rudders at speed too (see Airframe aerodynamics).
6. Anti Torque Rotor Id. Leave it empty, and add rotor.lower to Extra Rotor Visuals.