Akagi Kaman K-Max Helicopter

Here is a video showing the helicopter, the rotors are perfectly synchronized.

As there are not many such design helicopter, then my question are, is any aerodynamic weakness? What is its advantage/disadvantage of that helicopter?


It's a twin rotor design, counter-rotating: no resulting torque on the airframe and no tail rotor needing to be powered. The twin rotors do not share a common shaft, with all of the extremely complicated control mechanisms that these require.

From J. Gordon Leishman, Principles of Helicopter Aerodynamics, section 2.15:

The design advantage of a twin rotor is that all power can be devoted to providing useful vertical lift and performance. However, the two rotors and their wakes interact with one another, producing a somewhat more complicated flow field than is found with a single rotor, and this interacting flow incurs a loss of net rotor system aerodynamic efficiency.

  • $\begingroup$ I believe they are very different between V-22 Ofsprey, Akagi Kaman K-Max, but probably a bit similar too Chinook Helicopter (also built by Boeing). What my concern/question here is due to the overlapping blades, which aerodynamically will disturb the wind. V-22's blades are not overlapped at all. $\endgroup$ Dec 27 '19 at 10:01
  • $\begingroup$ Indeed, because there is a wing in between the V22 main rotors, creating a much wider aircraft. If the V22 could not tilt its rotors forward, the design would not make much sense. $\endgroup$
    – Koyovis
    Dec 27 '19 at 10:13

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