The Art of the Helicopter John Watkinson - Karatunov.net

362 The Art of the Helicopter
Fig. 9.12 Mil V-12 was the biggest helicopter ever built but did not enter production.
Fig. 9.13 Control system of coaxial helicopter is inevitable complicated, needing two swashplates. Collective
controls usually run inside the mast.
thus need more power. However, this power loss may be cancelled by the fact that the
lower rotor recovers the swirl energy of the upper rotor.
The coaxial helicopter needs two swashplates as can be seen in Figure 9.13. The first
connects the stationary cyclic controls to the lower rotor, and the second allows the
cyclic control to pass from the lower rotor to the upper rotor. The cyclic control thus tilts
both rotors in the same sense. The collective control will apply the same pitch change to
both rotors. Yaw control is commonly obtained by differentially changing the collective
pitch. This requires rotating mixers to add the cyclic inputs from the swashplates to the
collective inputs that generally pass up the centre of the mast. The resulting mechanism
is incredibly complicated as a study of a Kamov rotor head will show.