Collective
~ adjusts helicopter's altitude during hovering flight
~ is a position control
~ due to ground effect moving the collective a set amount will change altitude by a set amount
~ most collective controls also effect engine power output
~ the change in pitch angle of the main rotor almost always requires a change in engine power to maintain a constant main rotor RPM

No connection configuration
~ pilot is required to roll the throttle on and off while making collective pitch adjustments

Correlated collective
~ collective is mechanically connected to the engine throttle such that moving the collective also moves the throttle
~ correlators can be very effective if the engine power output can be accurately matched to collective position

Governor
~ a device which actively tries to maintain rotor RPM at a preset value
~ would typically sense the change in main rotor RPM caused by a collective pitch adjustment,
~ and would increase or decrease throttle as required to maintain desired RPM
~ some governors sense collective movement and start adding or removing fuel right away in anticipation of the effect the movement will have on RPM
~ this is called a "compensator" and is typical in turbine engines which are slow to accelerate and decelerate
~ and therefore would experience large RPM fluctuations without the compensator

Collective is connected to the engine because
~ throttle is typically mounted on the end of the collective control (but is sometimes on the overhead panel on machines with governors)
~ you can think of the two controls together as the "power" control, or you can think of them seperately

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