CORRELATOR / GOVERNOR CYCLIC PITCH CONTROL COLLECTIVE PITCH / THROTTLE COORDINATION 4-2 Figure 4-4. The cyclic pitch control may be mounted verti- cally 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. Figure 4-3. Relationship between manifold pressure, r.p.m., collective, and throttle. Figure 4-2. A twist grip throttle is usually mounted on the end of the collective lever. Some turbine helicopters have the throttles mounted on the overhead panel or on the floor in the cockpit. A correlator is a mechanical connection between the collective lever and the engine throttle. When the col- lective lever is raised, power is automatically increased and when lowered, power is decreased. This system maintains r.p.m. close to the desired value, but still requires adjustment of the throttle for fine tuning. A governor is a sensing device that senses rotor and engine r.p.m. and makes the necessary adjustments in order to keep rotor r.p.m. constant. In normal operations, once the rotor r.p.m. is set, the governor keeps the r.p.m. constant, and there is no need to make any throttle adjust- ments. Governors are common on all turbine helicopters and used on some piston powered helicopters. 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. has to be moved manually with the twist grip in order to maintain r.p.m. Twisting the throttle outboard increases r.p.m.; twisting it inboard decreases r.p.m. [Figure 4-2] The cyclic pitch control tilts the main rotor disc by changing the pitch angle of the rotor blades in their cycle of rotation. When the main rotor disc is tilted, the horizontal component of lift moves the helicopter in the direction of tilt. [Figure 4-4] When the collective pitch is raised, the load on the engine is increased in order to maintain desired r.p.m. The load is measured by a manifold pressure gauge in piston helicopters or by a torque gauge in turbine helicopters. In piston helicopters, the collective pitch is the primary control for manifold pressure, and the throttle is the pri- mary control for r.p.m. However, the collective pitch control also influences r.p.m., and the throttle also influences manifold pressure; therefore, each is consid- ered to be a secondary control of the other’s function. Both the tachometer (r.p.m. indicator) and the manifold pressure gauge must be analyzed to determine which control to use. Figure 4-3 illustrates this relationship. IfGLYPH<.notdef> Manif oldGLYPH<.notdef> PressureGLYPH<.notdef> is andGLYPH<.notdef> R.P .M.GLYPH<.notdef> is Solution Low Low Low Low High High High High Increasing the throttle increases manifoldGLYPH<.notdef> pressure and r.p.m. Lowering the collective pitch decreasesGLYPH<.notdef> manifold pressure and increases r.p.m. Raising the collective pitch increasesGLYPH<.notdef> manifold pressure and decreases r.p.m. Reducing the throttle decreases manifoldGLYPH<.notdef> pressure and r.p.m.