Control System for a remote controled model plane

There a a TON of different configurations when it comes to RC control.

The most basic implementation is what is called a 3 channel setup:

• Throttle
• Rudder (left and right turn)
• Elevator (nose up and down)

The 3 channel models usually use dihedral to self level from a turn.

If you want a little more control (often called bank and yank) you add ailerons using either an additional channel split with either a mechanical linkages / y-cable harness or an yet another channel to control ailerons.

Yet more options are:

• Flaps - usually two more channels
• actuators such as bomb drops etc
• lights etc etc

These channels are almost always PWM (pulse width modulation) control of servos and require an individual wire (Signal, +5V, GND) back to the receiver.

An alternative for modern servos/flight controllers is to essentially use TDM to string all of the channels together in a single output called PPM (Pulse Position Modulation).

BTW, I most often fly with 8 channel radio/receiver on my planes (6 or so in use).

Hi Bob,

Thanks for the great information. As I pointed out to Joey it is a legitimate question that I have had. I haven't had time to check out your links but I will. Please leave your answer in place as I can control the helpfuls and corrects.

John

"RC Aircraft" is a very generic term and the amount of controls can vary depending on the type and the intended use.  In general there are 4 types of main control and two ancillary controls:

Main controls:

Throttle - Controls speed of the propulsion system

Elevator (horizontal part on an aircrafts tail) - Used to control pitch
Ailerons - these are on the wings and used to control roll

Rudder - (vertical part on tail) used to control yaw.

Ancillary:

Flaps

Retracts

Nice to have:

Brakes

Thrust vectoring.

This is a typical 4 channel setup for an airplane or jet.  Its very common to only have 3 of the 4 however.  Trainer type planes will usually have dihedral in the wings (the make a V shape when you look at the front) and these typically do not contain ailerons.  The reason is that by steering with rudder, it takes a lot of work to get the plane to roll upside down (inverted).  It can be done but you have to try.  When you let go of the rudder in a turn, the dihedral helps "auto level" the plane as the wing that is banked is more parallel to the airflow and creates more lift causing it to roll flat.

However with ailerons, you can roll upside down very easy.  The reason rudder is not included many times on aileron planes is it usually isn't needed.  The rudder helps correct for cross wind conditions, and most people wont fly in a cross wind as correcting for it is difficult.  So to make things cheaper it is usually left off.

I would say 3 channels is the minimum required.  There are very basic trainer planes that use 2 channels.  For example, I have an "airhogs" brand plane and all it is has it two motors.  The motors have and angle on them pointing up.  So to climb, I give more throttle, to dive less throttle.  If I want to turn, the system will reduce the throttle on one of the motors.

This type of aircraft usually doesn't fly real well and I question if they are really easier to fly than a 3 channel plane.  They are trying to protect you from being able to over control the plane, but not having enough control is usually more disastrous in my opinion.

Any airplane sold a "aerobatic" will include a rudder, in some cases a very large rudder as in an "Extra 300" plane.  The rudder is use to perform tricks, snaps, hovers, and knife edges (flying with wing tip pointing down).

Some advanced aircraft like my big jet, require rudder by AMA rules.  AMA is the governing body of rc aircraft in the USA.

The ancillary controls I spoke of is called Flaps and gear.  These are on the wings next to the ailerons, usually more towards the body of the plane.  The flaps increase lift and drag making landing easier and slower.  The gear may be retractable requiring yet another channel.

A helicopter has the same basic controls but in a different configuration.  The same motions are used the, pitch, speed, roll and yaw.  I will digress on that for now so please ask if you want more information.

Each control is on a different channel.  Sometimes one set of controls may take two channels, for example it is common to have each aileron on a different channel since one of the servos needs reversed.  It also helps with initial setup trim to be able to adjust each aileron independently through the radio instead of using the mechanical linkages.

These days, most RC control systems are on the 2.4GHZ band.  Each channel has a variation of the 2.4ghz band and there are 100 channels from 2.400 to 2.500 that can be used.  The most channels I have ever seen on an RC radio is 18.  I use a 14 channel radio.

There are various protocols used that allow many radios to share the 2.4ghz spectrum and allow multiple aircraft in the air.  A couple of main ones are Spektrum DSM2 and Futaba FASST.  These are frequency hopping methods coupled with and ID that prevent interference.  Several years ago before computer based radios were very advanced, 72MHZ was used more widely.  It was common to have interference between radios and have airplanes crash.  It became common practice to have a flag on the radio's antenna showing what channel you are using as well as a radio impound.  Those days are gone.

As you may know, the Receiver (RX) sends out a PWM signal to the servos.  However the radio link uses PPM.  In terms of how they may communicate back and forth, that will depend on manufacturer.  They may use different channels or they may use one channel with encoding.

I have an estimated 3000 RC flights on my Futaba radio, and I have had 0 interference that I have ever noticed as a comparison.

There are 2 sticks on the radio, various switches and sometimes dials or sliders.  The two sticks have two different configurations depending on where you live.  In the US we use "Mode 2".

Left Stick x axis: rudder

Left Stick y axis: throttle

Right stick x axis: roll

Right Stick y axis: elevator

Mode 2 is primarily used in Europe:

Left Stick x axis: rudder

Left Stick y axis: elevator

Right stick x axis: roll

Right stick y axis: throttle

I have no idea the history behind this but this how things have been for some time now.

The best aircraft I like are 6 channel that have all control surfaces with flaps and retractable landing gear.

I mentioned I have a 14 channel radio, here is how my jet is mapped out:

1: Left Elevator

2: Left Aileron

3: Throttle

4: Rudders

5) Gears

6) right elevator

7) right aileron

8) left flap

9) right flap

10) steering

11) brakes

Computer radios these days allow channels to mixed and followed by other channels.  Just about any configuration can be had.  One thing interesting is that my jet has gears and gear doors.  A small unit, called a sequencer, reads the gear channel and then controls both the gears and the gear doors with a delay between the two.  however there are radios with the functionality built in by using 2 or more channels.

I'll let you digest that I have a lot more

Bob is right on!  However you forgot retracts   I went a bit overboard LOL.

perhaps I will explain helicopters next just for fun.

Now that is a great answer. I will re-read it a couple of times and post some followup questions but right now the boss wants to go to lunch.

John

Ah yes, retractable landing gear! Where we're going we don't need landing gear! 

Cool, I am correcting a couple typos as well

Technically, mode 2 is rudder/throttle on left, pitch/roll on the right and mode 1 is rudder/elevator on left, roll/throttle on right. but no one buys mode 1 over here! 

http://www.spektrumrc.com/Articles/Article.aspx?ArticleID=2105

There are other modes but we don't speak of them.

Great post BTW!

Thanks I fixed it in my post.

I know that if you have a V-tail you need something called a 'mixer' to make it control like a regular tail.