Robbe/Futaba FC-16 radio setup for 90° swash plate

by Kim “AiRdAncE“ Dalmeijer

Just like many of you, I picked up helicopter flying after having some years of experience with model airplanes. I thought helicopters would present a greater challenge, and in my case I was right. The cost of a model helicopter was no big issue to me as far as the budget goes, as I already had the radio, servos and so on to install in my new helicopter.

I guess that once you get started you can make it as expensive as you like. Buy al the tuning parts available in CFK, GFK, and aluminum and convert your Eco 8 into a real 3D monster machine.

In my case, the budget for helicopters is limited. Not by my bank account, but by my wife... a real setback once I realized that my Futaba FC-16 radio does not support the stock 90° swash plate of the Eco 8. Whining to my wife about 'needing' a new radio was without success, and it severely damaged my self-esteem once she started shouting that I should 'stop whining like a five-year old'. That's hard to cope with once you're over thirty.

Back to the essence of this article. I have an Eco 8 with the stock 90° swash plate, and a Futaba FC-16 radio that supports 120° and 180° swash plate setups, but no 90° setup like in the Eco 8. Searching for a solution I found the following trick which works well for me.

The types of swash plates
Programming steps
Testing your setup
Finalizing

The types of swash plates

The FC-16 supports four types of swash plates. The first type, H-1 consists of a setup with two servos at a 90 degree angle. The second type, H-2, is the one we will use. The third type is the 120 degree setup which would be used with the 120 degree aluminum swash by Ikarus. The fourth type is also a 120 degree setup, but with an uneven distribution of servos; one on one side of the helicopter body, two on the opposing side.

In the diagram you can find a summary of the four types of swash plates supported by the FC-16, and how the servo's (red dots) are positioned. The red numbers indicate the channel which the servo is on. The arrow indicates the forward flight direction.

As mentioned before, we'll use type H-2. This type applies the so called Heim system. More about this later. If you observe the diagram carefully, you'll discover that the elevator servo in this type is supposed to be attached to the front of the swash plate. In the Eco 8, our elevator servo is attached to the rear. We can easily fix this by reversing our elevator channel, channel 2. What you'll find though, is that this does not complete our quest to fix the problem. The elevator servo does not respond to increases and decreases of the pitch/throttle. So the two roll servos raise the swash, while the elevator servo stays in placeâ€¦ a possibly dangerous situation, don't you agree ? I'm sure this would severely influence our flying performance, and not for the betterâ€¦

This is the result of using the Heim system. This system is designed for use with a mechanical mixer. That's why one servo seems to be 'paralyzed' during pitch adjustments. No worries though! We have a FC-16, which features two independent electronic mixers. Only to our advantage as electronic mixers show no signs of strain and friction like mechanical mixers do.

So, we need to setup one of these mixers to activate our 'paralyzed' servo using the inputs sent from the left stick. The next section describes what we need to do to accomplish this.

Programming steps

Below you'll find the step-by-step instructions to setup your FC-16 for the 90 degree swash plate.

1.	Turn on your transmitter.
2.	Enter programming mode by pressing the upper and lower MODE keys simultaneously.
3.	Browse through the menus using the left and right MODE keys until you find SWSH.
4.	Select SWSH 2 by using the DATA keys.
5.	Browse through the menus using the MODE keys until you find REV.
6.	Press the CURSOR keys until the little triangle above channel 2 flashes.
7.	Press the lower DATA key ( - ) to reverse this channel.
8.	Browse through the menus using the MODE keys until you find PMX 1.
9.	Press the CURSOR keys until INH starts flashing
10.	Press the DATA + key. INH should now change into ON. This means the mixer is now enabled.
11.	Press the CURSOR keys until the upper little triangle flashes.
12.	Press the DATA keys to move the triangle over the '3' in order to select channel 3 (throttle/pitch) as our mixer input.
13.	Press the CURSOR keys until the lower little triangle flashes.
14.	Press the DATA keys to move this triangle over the '2' in order to select channel 2 (elevator) as our mixer output.
15.	Press the CURSOR keys until the percent sign flashes.
16.	Use the DATA keys to set the value at something like 50%. Moving the left stick forward and backward (throttle/pitch) should now move the swash up and down evenly. If it still tilts forwards or backwards slightly in the upper and lower extremities, play around with the value a bit until you get it right.
17.	Exit programming mode by pressing the upper and lower CURSOR keys simultaneously.

That's it. You've set up your transmitter to support the 90 degree swash of the Eco 8 !

Testing your setup

Now, with your transmitter (TX) still on, connect the battery of your helicopter receiver (RX). You might want to make sure your motor does not start by disconnecting the motor power leads, or enabling a 0% throttle switch on your TX like I have. Check that all movements of the swash correspond with the appropriate stick movement (I'm applying the MODE 2 stick setup; throttle/pitch and rudder on the left stick, elevation and roll of the swash on the right stick):

Stick movement	Channel	Observation on swash plate
Left stick forward	1,2,3 and 6	Swash moves up
Left stick backward	1,2,3 and 6	Swash moves down
Left stick left	4	No movement (tail rotor moves)
Left stick right	4	No movement (tail rotor moves)
Right stick forward	2	Swash tilts forward
Right stick backward	2	Swash tilts backward
Right stick left	1 and 6	Swash tilts left
Right stick right	1 and 6	Swash tilts right
Below are optional:
2nd slider up (hovering pitch adjustment)	1, 2 and 6	Swash moves up slightly
2nd slider down (hovering pitch adjustment on)	1, 2 and 6	Swash moves up slightly

If either movement does not correspond to the movements described in the above table, try reversing the corresponding channel by using the servo reverse function REV.

For the optional slider to adjust the hovering pitch, you might want to program PMX 2 (the second mixer) to get the swash to move up and down evenly. Just program the input to channel 6, output to channel 2 and the amount to something like 15%.

Finalizing

The most ideal situation would be to either purchase the Ikarus aluminum tuning swash plate, or a radio with support for 90° swash. In my personal experience I've found that the trick that I describe in this article is somewhat inferior to a matched system. Especially the elevator servo behaves differently when increasing pitch. It slightly tilts the swash forward just below hovering pitch, tilts perfectly horizontal at hovering pitch, and slightly forward again just above hovering pitch. Not something I seem to be able to fix correctly - once you realize this, it's easily compensated with a little help from the right stick.

In rÃ©sumÃ©: if you have the budget and a cooperative wife, go for the 120° swash plate from Ikarus rather than applying this trick. It'll perform more accurately, plus the swash plate load is distributed evenly over three servos, rather than over two.

If you find any inconsistency, or if you feel a correction/remark/comment is in place, feel free to contact me via e-mail: k.dalmeijer@chello.nl .

Happy flying!