Pitch and throttle curve

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The pitch and throttle curve work together to control how much 'lifting power' is available at any position of the collective/throttle control stick. The pitch curve controls the main rotor's collective pitch, and the throttle curve controls the position of the throttle.

The pitch and throttle curve settings consist of a number of points (typically 3 to 7) which can be set to any given percentage of travel. For example, a 3-point pitch curve would allow you to set the collective pitch precisely at bottom, middle and top stick positions; between those points the pitch would change smoothly to join those points up.

Each flight mode has independent pitch and throttle curves associated with it. Typically normal mode will have the pitch range restricted, say from -3 to +8 degrees; whereas an idle up mode will use the full collective pitch range available to allow for acrobatics. Normally the maximum pitch range will be determined by your helicopter's mechanical setup and your swash mix values, with zero degrees collective pitch at 50% on the pitch curve; then the desired pitch range will be set by restricting the range of your pitch curve.

As the collective pitch is changed, the load on the engine also changes. Unless the throttle is also changed the main rotor will either speed up or speed down, leading to inconsistent control responses. The throttle curve therefore must be set to work in harmony with the pitch curve to provide sufficient power to keep the head speed constant (we say the throttle is corellated with collective). Setting the throttle curve correctly is generally a process of trial-and-error, often using a tachometer to monitor the head speed. Alternatively, a governor can be used to manage the throttle automatically on the helicopter.

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