Figure 3-2.  A twist grip throttle is usually mounted on the end of  the collective lever. The throttles on some turbine helicopters are  mounted on the overhead panel or on the floor in the cockpit.  Some helicopters do not have correlators or governors and  require coordination of all collective and throttle movements.  When the collective is raised, the throttle must be increased;  when the collective is lowered, the throttle must be decreased.  As with any aircraft control, large adjustments of either  collective pitch or throttle should be avoided. All corrections  should be made through the use of smooth pressure. In piston helicopters, the collective pitch is the primary control  for manifold pressure, and the throttle is the primary control  for rpm. However, the collective pitch control also influences  rpm, and the throttle also influences manifold pressure;  therefore, each is considered to be a secondary control of the  other’s function. Both the tachometer (rpm indicator) and  the manifold pressure gauge must be analyzed to determine  which control to use.  Figure 3-3  illustrates this relationship. Figure 3-3.  Relationship between rpm, manifold pressure, collective,  and throttle.  Figure 3-4.  The cyclic pitch control may be mounted vertically  between the pilot’s knees or on a teetering bar from a single cyclic  located in the center of the helicopter. The cyclic can pivot in all  directions.  The rotor disk tilts in the same direction the cyclic pitch control  is moved. If the cyclic is moved forward, the rotor disk tilts  forward; if the cyclic is moved aft, the disk tilts aft, and so on.  Because the rotor disk acts like a gyro, the mechanical linkages  for the cyclic control rods are rigged in such a way that they  The cyclic pitch control (or simply “cyclic”) is usually  projected upward from the cockpit floor, between the  pilot’s legs or between the two pilot seats in some models.  [Figure 3-4]  This primary flight control allows the pilot to fly  the helicopter in any direction of travel: forward, rearward,  left, and right. As discussed in Chapter 2, Aerodynamics  of Flight, the total lift force is always perpendicular to the  tip-path plane of the main rotor. The purpose of the cyclic  pitch control is to tilt the tip-path plane in the direction of  the desired horizontal direction. The cyclic controls the  rotor disk tilt versus the horizon, which directs the rotor disk  thrust to enable the pilot to control the direction of travel of  the helicopter. Cyclic Pitch Control Twist grip throttle Increasing the throttle increases  manifold pressure and rpm Lowering the collective pitch  decreases manifold pressure  and increases rpm Raising the collective pitch  increases manifold pressure and  decreases rpm Reducing the throttle decreases  manifold pressure and rpm Solution and manifold pressure is if rpm is HIGH LOW LOW LOW LOW HIGH HIGH HIGH Cyclic pitch control Cyclic pitch control 3-3