Flapping Blades Demo
by jfrouleau
uploaded 2017-07-18
(updated 2017-12-26)
stock aircraft
#helicopter #chopper #blade #flapping


Built in the SPH in KSP version 1.3.1.

This is a demonstration of a flapping blades rotor made with claws. The claws implement both a flapping hinge and a lead-lag hinge. Blade flapping is used to counter dissymmetry of lift caused by a rotating wing moving horizontally. The technique used to attach the blades to the claws is very simple: the blades are positionned exactly where they must dock with the claws and attached to decouplers. As soon as they are decoupled, they immediately dock at this position and angle. If they fall to the ground instead of docking, try moving them a little nearer of farther from the claws until you find the sweet spot. Editor Extension debug position is very useful for precise positionning. Docking blades will remove the symmetry so you won’t be able to collectively adjust the pitch of the blades in flight. So yeah you can use this to make reliable articulated parts at launch. Who wants to try an ornithopter ? :-) Docking ports can also be used to make flexible joints using the same method but I found they attach at different angles causing more dissymetry instead which leads to a shaky rotor and a disaster shortly after.

This is just a proof of concept so don’t pay attention to the weaknesses of this helicopter such as poor lift, random bearing explosions once in a while. More research is needed on this. Claws can also be used with locked pivots for still flexible but stiffer joints depending on the blades. The speed of this helicopter is about 180 m/s.


  1. Stage to decouple and attach the blades.
  2. Free all 4 pivots.
  3. Stage twice to decouple the rotor and start the engines.
  4. Put SAS on, raise throttle.
  5. You will find that the lift is not great as I said but for now just press 3 to engage forward engines and use this to lift.

This is the same helicopter but with a classic fixed blades rotor. The lift generated at the front is much higher than the lift generated at the back causing the helicopter to pitch up.

With articulated blades, the lift is more evenly distributed. This eliminate the problem of the helicopter pitching up.

Here is an autorotation landing after I ran out of fuel. Notice how the blades are inclined on the other side since the rotor turn in the opposite direction.

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