in shapes of Pasta, there are numerous Manufacturers and
in turn, models of Radios (Tx), Receivers (Rx) and
Electric Speed Controls (ESC). Due to the support for
new pilots with "AS3X" and "Safe", I will be referring
mainly about Spektrum Radios and Receivers. The wiring
in a Internal Combustion (IC) and an Electric Powered
(EP) RC plane are very similar. As shown in the images
below, the IC plane doesn't need a ESC and the battery
plugs into a Hub or Harness to provide power to the
Receiver. The EP plane, because it has an electric
motor, needs the ESC to control the speed of that motor.
The ESC also provides power to the Receiver. In both
cases, the Radio sends the command to the receiver which
in turn, sends the command to the appropriate servo or
motor. In the case of the IC plane, there is a servo on
the throttle of the engine. The EP plane motor just
receives the command to decrease or increase the power
from the ESC.
Wiring for IC RC Plane
Wiring for EP RC Plane
There are two components in either of the two types of planes, that will control or restrict the number of options your plane can have. The number of channels your radio and receiver support, will determine the number of options that can be operated on your plane. If you have an 8 channel radio, but the receiver only has 4, then 4 is the maximum number of channels supported. And the reverse is also the case. Lets look at a basic plane that has Ailerons, rudder, elevator and throttle. The channels needed would be (this is not an indication of what surface/device is on what channel):
Channel #1 - ailerons
Channel #2 - elevator
Channel #3 - rudder
Channel #4 - throttle
So, you purchased a basic 4 channel radio and plane with a 4 channel receiver when you started out. 6 Months later you are loving the hobby and have decided to upgrade to a plane with flaps and retractable landing gear. Hmmmmm, seems to be a problem! You can fly it , but you can't use flaps or retract your landing gear! Well, the reason would be that your radio only supports 4 channels, despite the plane having a 6 channel receiver. Oh, and that plane you are saving up for that drops bombs too, because you want to enter into the National Bomb Dropping competition? Get the idea? So, what I am says is, while you may be in a hurry to get out flying and have bought a Ready to Fly package with an entry level radio, you now will join the ranks (myself included) that have gone out and bought at least an 8 channel radio.
The transmitter converts the pilot's movements into a radio signal in a process called modulation. The transmitter then broadcasts this signal to the receiver. The receiver inside the airplane picks up this signal the same way the radio in your car picks up the local radio station. The receiver pulls the information from the radio waves and relays this information to each servo. Each Servo has a horn that is attached to its shaft. This horn is attached to a control surface, or engine throttle, via a push rod. The rotation of the horn translates into a linear movement at the control surfaces.
Servo Push Rod Horn
The movement of
the servo is directly proportional to the movement of
the control sticks on the radio. In other words, the
control surfaces on the airplane move exactly the way
you move the stick on the radio. The servos and
receiver power source simply plug into the receiver.
Some people add a switch between the battery and
receiver which is mounted to the side of the airplane.
manufactures of large scale planes (i.e. Cessna 150)
install a switch as standard equipment. The switch
allows you to turn the receiver off without removing
the battery when you're not flying or waiting to
fly. If you wish to install a switch, install it
between the ESC/Hub and Receiver.
The basic "Stick" movements
on your radio as displayed below, correspond to the
appropriate servo control via the receiver. The more
you move any one stick, the more the receiver tells
the servo to move. While the picture may be a bit
intimidating, unless you are a 10 year old who has
spent the last 8 years with a game controller in
your hands, there are aids such as Safe to help you.
As most things, it is also a matter of time spent on
the field going through the movements and
I will not spend
a lot of time talking about the switches on your
radio, but there are three that are important to you
as a new pilot. Keep in mind that all the switches are
programmable and you can setup the function for each,
that best suits you. I will refer to a specific switch
such as "A". If you look beside each switch on your
radio, there should be a small label with what switch
it is. When you accumulate planes, each is a separate
setup for each plane, on your radio. When you want to
fly a different plane, you simply go to the plane
selection on your radio and select it. All settings
for each plane on your radio are for that particular
plane and are kept separate. It is highly recommended
that when you acquire new planes, you setup the same
switches for each with the same function. That way you
don't have to remember what switch does what as you
change plane selections.
The first switch
(I use switch "A") that is important, is the one you
use to turn Safe off and on, if your plane receiver
has it.The second switch is called the "Rate" or Dual
Rate" Switch, that controls the sensitivity of each
stick. "Dual Rates" refer to
altering the rate of servo travel for a control
surface on RC aircraft (e.g. Ailerons, Elevator, and
sometimes Rudder). Dual Rates consist of Low, Medium
and High Rates. Low Rates make the aircraft less
responsive (i.e. easier to control), and High Rates
make the aircraft more responsive (i.e. harder to
control). Dual Rates are typically controlled by a
three position toggle switch (I use switch "C") on a
radio. There are three settings, Low, Medium and
High for each of the aileron, rudder and elevator.
When you look at the radio display screen while
setting the Dual Rates, you first select the switch.
Further on the screen you select the control surface
you want to set for i.e. aileron. If you move the
switch through the three positions, you will see it
highlight each from 0, 1 and 2. You can set the
percent (%) of response for each, i.e. 55% for 0,
75% for 1 and 100% for 2. You would then go back and
select the control surface you want to set for, make
the changes and then repeat for the third surface.
This may sound complicated, but once our instructors
show you the screen and assist you in setting it up,
you will have a clear understanding of how it works.
Below is an example of a radio's D/R & Expo
Now when you add
in the Safe switch, you can see six different levels
of control with the Rate switch. Three setting with
Safe and three settings without Safe. When you have
Safe on and use the Rate switch, you not only have the
ability to slow down the reactions of the plane to
your stick movements, you have Safe's ability in
obtaining level flight after a turn. When you
are first starting your lessons, your instructor is
going to have your Rate switch in the Low position.
This means you have to move the stick a lot more than
Medium or High for the control surface to move. This
means your plane is not going to make any fast
movements such as turns and elevation changes. You
learn to make smoother movements and become confident
with your flying. As you improve, you can switch to a
higher setting. A good example would be doing your
takeoff and landing at low with Safe and once you gain
some height, switch to a higher rate setting and
practice smaller stick movements.
important switch, is the Throttle Cut switch. This is
a two position switch you assign to cutting power to
the motor. Your throttle must be cut until you have
moved your plane to your pilot station at the runway.
You then do your surface movement and motor run-up
tests. The propeller on any plane is capable of
causing serious body damage and has to be treated as
such. When you have finished your flight, you once
again cut the throttle before picking up your plane.
When you purchase a RTF or BNF plane, the receiver
will have been installed. Take a close look at that
receivers and what is coming out of it.
Servos have one thing in common. They each have
three wires attached which plug into the appropriate
slot on the receiver. As shown in the pictures
above, there isn't any uniformity in the colours
used for the wires. What they do have in common is
that one wire is for power, one for signal and one
for ground. Usually the brown or black is the ground
wire. Now, once again look at the receiver and in
all cases, the wire colours are all in the same
order. As you are installing batteries or making
connections to the wing from the receiver, one of
these connectors can come out of the receiver.
Simply plug it back in, in the same colour order as
the rest. If you are doing your check at the flight
like and one control surface isn't working, it is
because that plug has come out, or is partly out and
not making a connection. If you are installing a
receiver and aren't sure which way the colours
should go, try with all black or brown at the
bottom. If they are backwards, the servos will not
work. Just reverse all the plugs and it should be
A Typical receiver with Antennas
Speed Control (ESC)
An ESC will have
three sets of wires. One lead will plug into
your airplane's main battery. The second lead will
have a standard servo wire that plugs into the
throttle channel of your receiver. And finally, the
third set of wires actually power the motor.
A Sample connection of an ESC
An ESC follows a speed reference signal (derived from a throttle lever) and varies the switching rate of a network of field effect transistors . By adjusting the duty cycle or switching frequency of the transistors, the speed of the motor is changed. The rapid switching of the transistors is what causes the motor itself to emit its characteristic high-pitched whine, especially noticeable at lower speeds.
Different types of speed controls are required for brushed DC motors and brush-less DC motors. A brushed motor can have its speed controlled by varying the voltage on its armature. A brush-less motor requires a different operating principle. The speed of the motor is varied by adjusting the timing of pulses of current delivered to the several windings of the motor.
Brush-less ESC systems basically create three-phase AC power, like a VFD (variable frequency drive), to run brush-less motors. Brush-less motors are popular with radio controlled airplane hobbyists because of their efficiency, power, longevity and light weight in comparison to traditional brushed motors. Brush-less DC motor controllers are much more complicated than brushed motor controllers.
The correct phase varies with the motor rotation, which is to be taken into account by the ESC: Usually, back EMF from the motor is used to detect this rotation, but variations exist that use magnetic (Hall effect) or optical detectors. Computer-programmable speed controls generally have user-specified options which allow setting low voltage cut-off limits, timing, acceleration, braking and direction of rotation. Reversing the motor's direction may also be accomplished by switching any two of the three leads from the ESC to the motor.
normally rated according to maximum current, for
example, 25 amperes or 25 A. Generally the higher
the rating, the larger and heavier the ESC tends to be
which is a factor when calculating mass and balance in
airplanes. Many modern ESC's support nickel metal
hydride, lithium ion polymer and lithium iron
phosphate batteries with a range of input and cut-off
voltages. The type of battery and number of cells
connected is an important consideration when choosing
a battery eliminate circuit (BEC), whether built into
the controller or as a stand-alone unit. A higher
number of cells connected will result in a reduced
power rating and therefore a lower number of servos
supported by an integrated BEC, if it uses a linear
voltage regulator. A well designed BEC using a
switching regulator should not have a similar
ESC's are rated
for a maximum current. The more current an ESC is
rated for, the more expensive and heavier it will be.
Choose an electronic speed controller that is rated
for slightly more than what your motor will pull at
full throttle. Too much current will damaged an
electronic speed controller very quickly! On the same
token, too big of an ESC is dead weight that will
adversely affect the performance and balance of your
ESC firmwareMost modern ESC contain a micro-controller interpreting the input signal and appropriately controlling the motor using a built-in program, or firmware. In some cases it is possible to change the factory built-in firmware for an alternate, publicly available, open source firmware. This is done generally to adapt the ESC to a particular application. Some ESC'sESCs are factory built with the capability of user up-gradable firmware. Others require soldering to connect a programmer. ESC are usually sold as black boxes with proprietary firmware. As of 2014, a Swedish engineer named Benjamin Vedder started an open source ESC project later called VESC. The VESC project has since attracted attention for its advanced customization options and relatively reasonable build price compared to other high end ESC's.
Go to the next chapter Glossary