Rotorcraft Flying Menu >Helicopter Flight Controls > Collective Pitch / Throttle Coordination

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.

Figure 4-3. Relationship between manifold pressure, r.p.m., collective, and throttle.