ORIGINAL: barracudahockey

There's mCCPM and eCCPM

mCCPM like the Raptor has one servo for each control, elevator, aileron, and collective pitch.

eCCPM uses 3 servos, arranged around the swash plate usually 120 degrees apart (though there are variations) that are directly connected to the swash plate and use software mixing to achieve the same results. For example with mCCPM the elevator servo rocks the swash plate fore and aft for elevator control. With eCCPM the front two servos would pull down and the back servo would push upwards acheiving the same swash plate movement. With mCCPM the collective pitch servo would move an arm to move the swash plate up and down, with eCCPM all three servos move up at the same time through radio mixing.

Advantages of eCCPM, less complicated linkages, usually 3 servos and 3 striaght pushrods. Faster response to collective inputs (in some but not all models), can use less torque servos since 3 servos are doing the work of one.

Disadvantages, more complicated to program, direct linkages lead to stripped servos in almost any crash no matter how minor, requires 3 matched servos, takes some tinkering to get all the control interaction canceled out.