Looking at the Kaman K-Max and H-43 Huskie, it looks like they rely entirely on rotor flaps. How are they controlled?


1 Answer 1


What's missing from the picture is the hydraulic actuators that move the swash plate. The K-max and all other Kaman helicopters have cyclic and collective control via servo-tabs behind the trailing edge of the blades. These can be deflected manually. The servo tabs are visible on this picture:

enter image description here

Further info from this site, which also shows a cutaway drawing revealing the thin control rods inside the rotor hub fairing:

The servo flap is a small airfoil located at about 75 percent span of the rotor blade, situated on the trailing edge of each rotor blade. These flaps are controlled by the pilot through push-pull control rods and their function is similar to that of an elevator on fixed wing airplanes. Moving the trailing edge of the flap upward moves the leading edge of the main rotor blade up. This increases the rotor pitch or the lift in very much the same manner as the elevator, on a fixed wing aircraft, changes the angle of attack on the wing. Thus the helicopter pilot can cause the angle of attack of the flap to increase or decrease in pitch, causing the helicopter to alternately dive or climb.

  • $\begingroup$ Hi Koyovis, thanks. I understood how collective control works, but I still don't understand how cyclic control works. Is there a swashplate which tilts the rotors forward/backward, and sideways? $\endgroup$
    – Tony Stark
    Commented Dec 5, 2017 at 9:37
  • $\begingroup$ @TonyStark the control rods are rotating and they need to be cyclically extended, so I expect that somewhere inside is an arrangement similar to a swashplate. $\endgroup$
    – Koyovis
    Commented Dec 5, 2017 at 14:56
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    $\begingroup$ The first synchropter (Flettner 282 Kolibri) did have swashplates for collective pitch control. (Source: John Watkinson, The Art of the Helicopter). $\endgroup$
    – xxavier
    Commented Dec 6, 2017 at 11:16

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