Mechanical vs. CCPM rotor head control
Posted on December 8, 2009 by aaronredbaron
Most collective pitch model helicopters today use electronic mixing, called CCPM (Cyclic and Collective Program Mixing), while the other type of swashplate mixing, mechnical, has become less popular. CCPM mixing does offer some advantages, but there is still value to a well designed mechnically mixed heli. What is all this mixing we are speaking about anyway? Although a select few models have used a collective pitch control which goes through the center of the main shaft and does not affect the swashplate, most models move the swashplate up and down for collective pitch control, and tilt it for cyclic pitch control (aileron and elevator). Here is where the difference lies; in a CCPM setup, three identical servos work in unison through an electronic mix to accompish collective pitch, as well as fore/aft (elevator) and roll control. In a mechanically mixed heli, each control function has a dedicated servo, and they work together through a mechanical mixing system to manipulate the swashplate.
Mini Titan SE CCPM swash control
CCPM
Advantages
- Torque of servos gets added up when working together for collective pitch, which requires the most force of all the controls
- Fewer mechanical linkages to introduce slop or free play into the system
- Less weight from parts associated with a mechanical mixing system
- Strength of servos’ centering ability gets added up, providing a crisp, smooth feel around neutral
Disadvantages
- Servos must be well matched
- More complicated initially to comprehend and setup
- If one servo fails in flight a crash is practically guaranteed
- Interaction or cross-control can be difficult to eliminate, although its a minor issue with good servos
Raptor 50 cyclic servos
Mechanical Mixing
Advantages
- Zero interaction or cross control
- Loss of one servo in flight does not affect the other controls as much as CCPM
- Servos don’t need to be matched, although its best to used matched servos for advanced aerobatics
- Easy to set up and doesn’t even require a computer radio
Disadvantages
- Requires more linkages and mechanical parts than CCPM
- A powerful collective pitch servo with good holding power must be used for the best performance
- More weight with associated parts
- Much more difficult to design and implement for a new helicopter design than CCPM
