text: longi- 
  tudinal control of a tandem-rotor helicopter. 
  A pitching moment can be produced by tilting 
  both rotors by a cyclic pitch change in each 
  rotor, by a differential collective pitch change 
  that increases the thrust on one rotor and de- 
  creases it on the other, or by some combination 
  of these methods. The two basic methods are 
  illustrated in figure 4.36. Obviously, a change 
  in fuselage attitude must accompany the dif- 
  longitudinal 
  ferential collective method of 
  control. 
  
  There are several possibilities  for 
  
  The directional control 
  
  Directional control of a tandem-rotor heli- 
  copter is accomplished by differential cyclic 
  control of the main rotors. For a pedal turn 
  to the starboard, the forward rotor 
  is tilted 
  to the starboard and the rear rotor is tilted to 
  port, creating a turning moment as shown in 
  
  321 