Setting Up A CCPM Heli

Cyclic Collective Pitch Mixing, or CCPM for short, is one of the two popular methods for controlling the swash of a RC heli. CCPM has been around and available for numerous years, but has really taken a foothold in the hobby recently. Modern radios make CCPM easier and more problem free than earlier hobbyists could have ever dreamed. With a little understanding and some simple tips, any heli pilot can be a CCPM expert.

Explanation of CCPM
CCPM can simply be defined in a helicopter as multiple servos working together, interdependently, to execute all the control movements (collective, aileron, and elevator) of the swashplate. There are 4 servo and 3 servo CCPM setups, this discussion will focus on what the majority of the CCPM helicopters use, a 3 servo 120° setup. The other method of swash control, non-CCPM, is often called Single Servo Mechanical. What is the difference one may ask? In simple terms, Single Servo Mechanical control uses a single servo for each control movement, and these servos are completely independent of each other--each has a duty that is distinct on the swashplate.

On the other hand, CCPM mixes a combination of the three servos together to complete the control movements. For example, when the collective stick on a radio is moved all three servos will flow in unison to raise or lower the entire swashplate accordingly. In CCPM no swash movement occurs without at least two servos doing the job.



Mechanical AND RADIO SETUP
The mechanical setup of a CCPM heli is extremely important, just as on non-CCPM machines. Doing proper setup in the beginning saves time and prevents troubles later on. It is important to follow the manufacturer directions as closely as possible from the manual. The crucial thing to remember with a CCPM setup is symmetry and right angles. The radio setup is also included in this section as they are intertwined.

1. Build the helicopter per the instructions, setting all linkages (and bellcranks if applicable) to the correct lengths. Install the servos and plug them into the proper channels. Many pilots get stuck at this stage, deciding which servo plugs in where. This can be confusing but there is a simple way to do it. Plug the servo that controls the ball that is inline with the frame of the heli (the ball that sits directly behind or in front of the mainshaft) into the elevator channel of the receiver (channel 3 on a JR system, channel 2 for Futaba and Hitec, for other makes check the radio manual). Then plug the other two swash servos into the aileron and pitch channels (channels 2 and 6 on JR radios). Do not worry about which of these two servos ends up in which channel, they will be taken care of in the radio setup.



2. Turn on the transmitter and set it to 120° CCPM in the swash type menu (or 140° if the heli is a 140° machine). Center all the trims, get rid of any sub-trim, and make sure all endpoints are at 100% for the 3 swash servos. It is also crucial at this point to set a linear pitch curve (0, 50,100) for the initial setup.

3.Make sure the throttle stick is at the halfway point (for electrics, make sure the motor is disabled). With the servos centered, try attaching control arms to the servos so each arm is perfectly lined up, either parallel with the servo, or exactly 90° to it depending on the heli. It is important that it be as close as possible to perfect, try various servo wheels and arms until one is found that fits the bill. If necessary, use a small amount of subtrim to center the arm, but only as a last resort. It is best to do as much mechanically with the arms and links. Once the three "perfect" arms have been found, install the ball links to them at the distances instructed in the heli manual then install the arms on the servos.



QQTECH TIP
Notice that eCCPM or mCCPM is not mentioned. Since all CCPM is done electronically (in the radio), there really is no mCCPM. What we have is "CCPM" or "Single Servo Mechanical" (can be shortened to just "mechanical" if preferred). No electronic mixing happens in a single servo setup, each servo is completely independent. When one servo fails in single servo machines, the radio still has control of the other two functions. This is not the case in a CCPM setup, where each servo relies on the others to complete their tasks. The terms eCCPM and mCCPM can cause quite a bit of confusion as the terms imply a similarity between the two, which is not the case. If one sticks to the historically more accurate terms of "CCPM" and "Single Servo Mechanical" it will help differentiate the two systems better. In other words, heli kits advertised as CCPM will be eCCPM, since that is the only type of CCPM available.

There is much debate on what the true advantages and disadvantages are for using CCPM over Single Servo. We will stick to the basics here and leave the debate for another time.

Some of the advantages of CCPM include:
• Easy mechanical setup, usually less linkages and hardware.
• Less slop due to less links.
• CCPM helicopters often weigh less, also due to the lower parts count.
• More torque is applied on the swash movements, multiple servos sharing the load compared to one in Single Servo.

Some disadvantages of CCPM may include:
• Interaction--this is evidenced by the "dance" a CCPM swashplate does on occasion, especially when it is moved quickly. Its cause lies in the basic geometry of the system (one servo has to travel a little more than the others to move the swash the same distance for elevator) and in the inherent, minute speed/wear differences between one servo and the next. The slower the servo, the worse the interaction. Modern radios do a pretty good job at taking this into account and rectifying the situation, but some interaction usually remains.
• CCPM helicopters that use direct links from the servos to the swashplate leave the servos more susceptible to damage in a crash.
• In a CCPM heli, when one servo dies inflight, all basic swash control is lost; slightly lowering the chances to save the heli.
• CCPM requires the use of high quality servos that are the same make and model (and preferably age), mixing servos or penny pinching here will cause some headaches in setup and in flight.QQ

4.Next, get the 3 servos moving in the right direction. This can be a difficult and trying task but there are some well known tricks that make it easy. Remember the following detail and things will be simple; servo reversing in CCPM is used to set the relation between the servos. Meaning they move together when they should, and in opposite directions when they should. Servo reversing is not used to reverse a function's direction, such as pitch or cyclic--for this, adjustments in the swash mixing menu will be made.


5.Before connecting the swashplate to the servos, make sure the servos are moving properly in relation to each other. Use the servo reversing menu to do this. The two side servos (the pitch and aileron channels) are setup first using the reversing menu. Set them so that the two servo arms move in opposite directions when a left/right cyclic command is given (one arm moves up and the other moves down). Set the servo plugged into the elevator channel so that its arm moves in the opposite direction as the other two servos when a fore/aft cyclic input is given (the other two servos will move together with fore/aft swash movement). Only reverse the elevator servo to fix the fore/aft direction, leave the aileron and pitch servos at the settings set in the left/right setup above.


6. Now move on to getting the servos moving in the right direction in relation to the helicopter. Center the controls and connect the swashplate, making sure it is level and in the EXACT center of its travel range by adjusting the linkages. Move the throttle/pitch stick up, if the swash is moving in the right direction (inducing positive pitch) then this function is working properly. If the swash is giving negative pitch when positive is expected, use the swash mix menu to reverse it by changing the value for Pitch in the menu from a positive to a negative (retaining the same number value). For example, if the number next to Pitch in the radio was +70, setting it to -70 will reverse the pitch function and make the swash move in the opposite direction. Do the same thing with the Aileron function (left/right cyclic) and the Elevator function (fore/aft cyclic)--using the mix numbers to reverse the direction if necessary.


7.Once the swashplate is moving in all the right directions in respect to the control stick, it is time to set the travels and prepare for flight!! Please note that most radios have a default expo amount for the swash mixes in CCPM. These expo settings help counteract interaction and it is generally recommended that expo is used for a smooth swashplate. Use the values found in the swash mix menu (the same ones used earlier to change the pitch, aileron, or elevator function direction) to increase or decrease the travel for each movement (check for binding as well). If more pitch is needed simply increase the Pitch value to add more travel. Do not change the "+/-" found in front of the value, only the number itself. For example, if more pitch is needed and the Pitch value in the Swash Mix menu is initially -60, changing the number to -70 would add more travel, and likewise, if the Pitch value was initially +60, changing it to +70 would also add more travel. Clear as mud? Don't worry, some time spent using the radio and seeing the effects of each change will help CCPM make more sense.


Trim ADJUSTMENTS
With the mechanical setup done properly, the helicopter should end up with equal positive and negative pitch and equal cyclic throws. Finish by setting the pitch curves and getting everything else ready to go on the heli. If small adjustments are needed to get a "hands free hover" during flight testing, it is ok to use the radio trim. But if too much trim is being used, change the linkages instead to center things up. CCPM helis work best when the mechanical setup is near perfect and the less trim used the better for the mixing.[10}

140° Versus 120° CCPM
There are a small number of helis out there that are offered in a 140° CCPM version. The huge advantage a 140° system has over a 120° is that the geometry is more evened out between the two side servos and the front servo. This gives a more equal cyclic rate all the way around, where on a 120° setup the left/right cyclic is slightly faster than the fore/aft. The drawback is that there are still only a handful of radios with 140° mixing available (though a radio with a 120° program can be made to work with a 140° setup with some simple mixing). Also, only a handful of kits with 140° CCPM are currently available.

The End!
Though it may appear complicated on paper, and in theory, setting up a CCPM heli is really no more difficult than setting up a Single Servo Mechanical heli. The trick is to be exact in the mechanical setup and to read the radio and helicopter manuals thoroughly. Follow the steps just outlined and that CCPM heli will no longer be a mystery.