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There are many terms and jargon that are unique to just about every specialized field and radio control is not exception. We have put together this section to help familiarize you with some of those terms. We have broken the list into sections which you can access from the links at the right. This section will be under constant addition and revision.

Aircraft Terms
The following are some terms related to Aircraft in General:

Aileron   » Image
An Aileron is a moveable surface on the trailing edge of the wing which provides directional control of the roll of the aircraft. A Strip Aileron is an aileron that is narrow and usually takes up the entire, or most of the trailing edge of a wing. A Barn-door Aileron is wider and takes up a smaller portion of the trailing edge towards the wing tip.
The Airfoil is the shape of the cross section of the wing. The front of the airfoil is the leading edge and is usually a rounded section. The back of the airfoil is the trailing edge and usually tapers to nearly a point. The distance between the two is the wing chord. The top surface of the airfoil is usually always curved to allow smooth airflow and produce lift.
Ballast is extra weight added to a glider to help it penetrate better in windy weather or to increase its speed. Ballast is usually added in tubes in the inner portion of the wings or in the fuselage at the center of gravity.
Center of Gravity
The Center of Gravity is the position in the aircraft where if a point was placed, the plane would balance. The “C of G” should usually be found along the centerline of the aircraft at a distance approximately 1/3 of the way behind the leading edge of the wing.
The Clevis is a small fastener at the end of a pushrod, usually made from nylon or metal, which connects the pushrod to the control horn. Clevises may frequently be referred to as links.
Control Horn
The Control Horn is a small bracket mounted on a control surface to transfer the movement of the pushrod to the control surface.
Control Surface
A moveable surface, attached to the airframe of an aircraft, which controls the direction of the aircraft.
Conventional Tail
A Conventional Tail is one with the stabilizer mounted directly on the fuselage and is the usual configuration of an aircraft. These are the simplest to construct and seem to be most popular.
The covering of an aircraft is the skin which is applied to the airframe, closing it in. On R/C aircraft it is commonly a fabric or plastic film which is heat applied with an iron. Plastic covering, once applied, gives a durable, shiny finish and requires no further treatment. Fabric covering usually requires a layer of paint to finish it and make it resistant to the exhaust of the engine. Covering materials come on a roll and in many different colors and may be cut to rough shape before being ironed onto the airframe.
Crucifix tail
Crucifix tail refers to a stabilizer that is mounted part way up the fin. This is a compromise between the conventional tail and the T-tail, combining some of the major advantages of both.
Dihedral   » Image
The Dihedral of a wing is the Vshape the wing makes or the angle between the wing and the horizontal. Usually the greater the dihedral angle the more stable the aircraft will be (to a point) and is common in trainer type aircraft. A flat wing with little or no dihedral is less stable and more suited to aerobatics.
Elevator   » Image
The Elevator is the horizontal moveable control surface at the tail of the model connected to the stabilizer. It controls direction in pitch.
Engine mount
An engine mount supports the engine in an aircraft. Some aircraft use wooden rails to which the engine is mounted while others require a shaped nylon or aluminum mount. The wooden rail type would usually be included in a kit while the molded type may or may not be included, depending upon the kit. It is possible to get mounts specifically for a particular engine, although many generic type mounts are available to fit certain engine size ranges.
Fin   » Image
The Fin, also known as the “vertical stabilizer”, is the fixed vertical surface at the rear of an aircraft. It provides yaw stability for the aircraft.
Flap   » Image
The Flap is a control surface found on some aircraft, usually located on the inboard trailing edge of each wing. Flaps may be lowered to increase the lift of the aircraft by simulating an under-camber airfoil.
Flat Bottom
A Flat Bottom Wing is when the lower surface of the wing is primarily flat between the leading and trailing edges. This type of wing has high lift and is common on trainer type aircraft.
Flex Cable
A Flex Cable is a special type of pushrod which is very flexible and can bend around corners even more easily than a flexible pushrod. These are generally made with a metal cable running inside a plastic tube and are popular in controlling the engine throttle.
Flying Stab
A flying stab is where the stabilizer/ elevator is one complete unit which all moves to control the pitch of the aircraft.
Foam Rubber
Foam rubber is used to wrap the radio receiver and receiver battery pack in the plane so that they will be isolated from the vibration of the running engine.
Fuselage   » Image
The fuselage is the body part of the aircraft which holds the passengers, cargo, or in the case of an R/C aircraft, the radio system.
Glide Ratio
The glide ratio is defined as the distance traveled in a horizontal direction compared with the vertical distance dropped on a normal glide. A 10 to 1 glide ratio means that the aircraft would loose one foot of altitude for every ten feet of distance traveled.
The hinges are used to connect the moveable control surfaces of the aircraft to the fixed surfaces and allow smooth, easy movement. They may take several forms including hinge points, pinned hinges, “living” hinges, etc.
Landing Gear   » Image
The landing gear of the aircraft refers to the support between the wheels and the wing or fuselage. It is usually formed from metal, wire or a nylon/fiberglass combination.
The pitch refers to the angle of the aircraft in the up or down direction.
Polyhedral refers to the multiple angles that wing panels make with the horizontal. A wing with polyhedral has more than two wing panels and the angle of the wing changes at each joint.
The propeller is the device that converts the rotational action of the motor into movement of air that creates the thrust to power the aircraft. The size of an aircraft propeller is described by two numbers—the diameter in inches times the pitch in inches. For example, a 10 x 6 propeller is a prop of 10” diameter and having 6” of pitch. The diameter is simply the length of the prop. The pitch is described as the distance the propeller will move ahead in a perfect or solid medium, at 100% efficiency, in one revolution. That is to say, if you were to rotate your 10 x 6 propeller exactly once, your plane would move ahead 6”, assuming this could be done with no slippage.

Different sizes of motors require different size propellers to keep their operating RPMs in an optimum range. You can refer to our propeller chart that indicates which size propellers are generally suitable for various sizes of engines—both 2- cycle and 4-cycle.

Some aircraft or airboats may require a propeller that pushes the air rather than pulls it. These are called Pusher Propellers and they are also available. A given engine would require the same size pusher prop as it would a “tractor” type. Pusher propellers are required as most glow engines will only operate correctly in one direction, so reverse operation is not possible. The main exception to this is the Cox reed valve engines which will usually run as comfortably backward as forward. 3-Blade propellers are also available for use in model aircraft. They are not quite as efficient as the 2-blade props, but the may be useful in certain applications. A general rule of thumb for selecting a 3-blade prop for your engine is to reduce the applicable 2-blade size by one inch in the diameter measurement.

For example, if you are running a .40 size e ngine you would usually us e a 10 x 6 2-blade propeller. If you wish to run a 3-blade propeller, a good choice would be a 9 x 6 3-blade. Three blade props are quite often used where they are more scale looking than 2-blades, or when a smaller diameter propeller is required due to restricted clearance.
Pushrod Connectors
The pushrod connector is another means by which a pushrod may be connected to a servo. The connector is mounted onto a servo arm and the pushrod wire is secured by a set screw.
The pushrods are part of the control linkage which connects the servo part of the radio system to the control surfaces of the aircraft. Pushrods may consist of a firm piece of balsa or fiberglass rod with threaded wire and clevises fastened to both ends, or they may b e the flexible type and take the form of a wire or one plastic tube running inside another with the ability to turn around corners.
The roll refers to the rotation of the aircraft around it’s centerline (one wing up and one wing down).
Rudder   » Image
The Rudder is the moveable control surface at the tail of the model connected to the fin. It controls direction in yaw.
A semi-symmetrical airfoil has a curved wing bottom surface but to a lesser degree than the top surface. It is a compromise between the flat bottom and the symmetrical airfoil. This is a very popular airfoil on sport type aircraft.
Spinner   » Image
The spinner is the cone shaped object mounted to the engine prop shaft on the nose of the aircraft. The spinner may be made from plastic or aluminum and functions primarily to improve looks and aerodynamics.
A Spoiler is a control surface more commonly found on gliders and jet aircraft which is used to slow down the aircraft and decrease lift. They are rarely found on conventional aircraft. They may be mounted on either the top or bottom of the center portion of the wings.
Stabilizer   » Image
The Stabilizer is the fixed horizontal surface at the rear of an aircraft. It provides pitch stability for the aircraft.
A Symmetrical airfoil is curved on the bottom to the same degree as it is on the top. If a line was drawn from the center of the leading edge to the center of the trailing edge the upper and lower halves of the airfoil would be symmetrical. This is ideal for aerobatic aircraft and most lift is created by the angle of incidence of the wing to the flight path.
Tail Dragger
This refers to the landing gear configuration where the main landing gear with two wheels is placed forward of the center of gravity and one small wheel, called a “tail wheel”, is mounted under the tail of the aircraft.
Tow-hook   » Image
The tow-hook is a small metal hook mounted on the bottom of the glider fuselage at approximately the center of gravity and to which the hi-start or winch is connected.
Tricycle Landing Gear   » Image
Tricycle refers to the landing gear configuration with a single steerable nosewheel mounted in front of the center of gravity, and a set of main landing gear with two wheels positioned just behind the center of gravity. Tricycle landing gear is usually a little easier to use when learning.
T-tail   » Image
The T-tail refers to a stabilizer that is mounted on top of the fin. This brings the stabilizer away from the turbulent air-flow of the wing and makes pitch control more responsive. It also gets the stabilizer out of harms way when landing on rough terrain. The T-tail construction is usually more fragile than the conventional tail, though, and are more difficult to build.
An Under-camber airfoil has the lower surface of the wing curved inwardly almost parallel to the upper surface . This type of airfoil produces a great deal of lift but is not common in R/C models.
Another name for landing gear (see landing gear)
A V-Tail is a special tail surface configuration where the horizontal stabilizers and elevators are mounted at an angle between 30 and 45 degrees in a V-shape and the vertical fin is eliminated entirely. The stabilizers provide stability in both pitch and yaw while the moveable surfaces provide directional control in both pitch and yaw.
Wheel Collars
Wheel Collars are small metal collars fastened with a set screw to the axle of an aircraft on either side of the wheel. This prevents the wheel from coming off the axle or rubbing against the landing gear.
Wheels   » Image
The wheels for an aircraft come in several styles including treaded, non-treaded, scale tread, air-filled, and super lightweight. Most brands of wheels are available in sizes from 1¾” to 6”, in 1/4” increments.
Wing   » Image
The wing of the aircraft is the large horizontal surface which produces the lift and allows the aircraft to fly. Wing placement may be on the upper part of the fuselage known as a high wing plane. This is more common on trainer type aircraft as a high wing model is more stable due to the pendulum effect of the fuselage. A wing mounted on the bottom of the fuselage is referred to as a low-wing aircraft and is more suitable for aerobatic type aircraft as stability is more neutral and manoeuvres such as rolls and loops are more easily done.
Wing Area
The Wing Area is the total surface area of the wing of the aircraft, usually calculated by the wingspan times the wing chord, although more complex calculations re used on unconventional wing plans.
Wing Chord   » Image
The wing chord of an aircraft is the distance from the front or “leading edge” of a wing to the back or “trailing edge”
Wing loading
Wing loading is defined as the weight of the aircraft divided by the wing area. It is usually expressed in ounces per square foot.
Wing Seating Tape
Wing seating tape is mounted on the fuselage wing saddle where the removeable wing fits and isolates the wing from vibration as well as to form a seal to keep exhaust gases from entering the structure.
Wing Span   » Image
The Wingspan of an aircraft is the length of the wing as measured from wing tip to wing tip.
Wing Tip
The very outer edge of a wing.
The yaw refers to the angle of the aircraft in the side to side direction.

Radio Terms
The following are some terms related to Radio Control Systems:

Adjustable Function Rate (AFR)
Similar to ATV, AFR allows end point adjustment independent of dual rate or exponential settings.
Adjustable Travel Volume (ATV)
An adjustment that lets you preset the maximum travel of a servo to either side of neutral.
Aileron Extension
The aileron extension (servo extension) is a cable with connectors on either end which goes between the receiver and a servo. This allows the servo to be placed at a greater distance from the receiver than the cable that comes on the servo will allow. It also permits easier removal of a wing when the servo that controls the aileron is mounted in the wing and the receiver is in the fuselage (which is usually the case). One aileron extension is usually included with a radio system of four or more channels. Aileron Extensions of various lengths are available from different manufacturers. Please note: long aileron extensions can sometimes cause radio interference problems unless “noise traps” are used.
Amplitude Modulation (AM)
Was initially the primary means of radio modulation used in R/C until recently. The control information is transmitted by varying the amplitude of the signal. AM is now used in only less sophisticated systems.
Buddy Box
The ability to connect two transmitters together for training purposes.
There are two definitions for the word channel in radio control. 1. It can refer to the channel number or frequency of operation of a control system. 2. It may also refer to one of the operating functions of a radio system. For example, a 4-channel radio system would have four control functions: aileron, rudder, throttle and elevator.
An electronic component of the radio that determines the frequency of operation. There is one in the receiver and one in the transmitter.
Digital Trims
Digital trims utilize a spring loaded slide switch rather than a potentiometer to adjust trims using digital messages.
Direct Servo Controller (DSC)
Allows full function of an aircraft’s servos via an umbilical cord. This permits adjustment of radio functions without switching on the RF portion of a transmitter.
Dual Aileron Extension
The Y-Harness is a cable which plugs into a single channel in a receiver and two servos. This allows both servos to be operated from the same channel.
Dual Conversion
Dual conversion refers to the method in which the receiver processes the incoming signal. Generally a dual conversion receiver is less prone to outside interference and is the preferred type of receiver.
Dual Rates (D/R)
Dual Rate allows the modeler to choose between two different control sensitivities. With the dual rate switch in the “OFF” position, 100% servo throw is available for maximum control response. In some more sophisticated systems this “OFF” position may be adjusted to provide anywhere from 30% to 120% of normal full throw. In the “ON” position, servo throw is reduced and the control response is effectively desensitized. The amount of throw in the Dual Rate “ON” position is usually adjustable from 30% to 100% of total servo movement. The modeler can tailor the sensitivity of his model to his own preferences.
End Point Adjustment
The ability to adjust one end of a servo travel only. Similar to Adjustable Travel Volume, but for adjustment on one side of neutral only.
Exponential Rate
Exponential Rate is where the servo movement is not directly proportional to the amount of control stick movement. Over the first half of the stick travel, the servo moves less than the stick. This makes control response milder and smooths out level flight and normal flight maneuvers. Over the extreme half of the stick travel, the servo gradually catches up with the stick throw, achieving 100% servo travel at full stick throw for aerobatics or trouble situations.
Fail Safe (FS)
An electronically programmed mechanism in most PCM radios to automatically return a servo or servos to neutral or a preset position in case of radio malfunction or interference.
Flight Modes
The ability for a radio system to switch between different types of flying, particularly in helicopters. Different parameters may be committed to the transmitter’s memory and selected using a “flight mode” switch.
Frequency Flag
The frequency flag is a marker that is mounted on your transmitter to indicate what frequency your system is operating on to alert other modelers so as not to cause interference. See the section on frequencies below for more information on radio frequencies.
Frequency Modulation (FM)
Now the most common method of radio modulation in RC, FM is less prone to interference than AM. Information is transmitted by varying the frequency of the signal
Idle Up
The function of a helicopter radio to first bring the throttle and rotor speed up before adding collective pitch.
Mixing is the ability to have one channel of control input at the transmitter affect more than one receiver channel and servo movement.
Mode I
The control stick configuration with the rudder and elevator being controlled by the left stick while the right stick controls the throttle and ailerons. This is popular in Europe.
Mode II
The control stick configuration with the ailerons and elevator being controlled by the right stick while the left stick controls the rudder and throttle. This is the normal set-up for aircraft in North America.
Mode IV
The control stick configuration with the rudder and elevator being controlled by the right stick while the left stick controls the ailerons and throttle. This is similar to Mode 1 except that the sticks are reversed. Some find this mode more desirable for flying aerobatics than the default Mode II.
Model Memory
Allows the storage of information for more than one model. Very convenient for only having to set reversing, trim, mixing, etc for a model once and still be able to use the transmitter for more than one model.
The way the electronic control information is sent from your transmitter to the receiver through radio waves.
Noise Traps
A noise trap is a small electronic device which is wired into a long servo extension to reduce radio interference and to boost the control signal going to the servo. These are recommended for use where long servo leads are necessary.
Pitch Curve
The pitch curve is the relation between the position of your transmitter control stick for collective pitch and the actual pitch of the rotor blades. It is desirable to have adjustable pitch curve points on a helicopter radio—the more the better. That way one can customize the collective response according to the type of flying.
Pulse-Code Modulation (PCM)
A special digital encoding of a frequency modulated signal. FM is still utilized, however, the control information is in the form of a digital word rather than just a pulse width, as is used with standard AM or FM. Using PCM adds additional protection against interference from various sources.
Servo Control Arms
Servo Control Arms are the plastic output horns which are mounted to the output shaft on your servos. These come in various sizes and styles for different control applications. Most servos will come with an assortment of arms so you can customize to your own specific control needs.
Servo Extension
Same as aileron extension.
Servo Reversing
This feature allows the modeler to reverse a servo’s rotation direction at the flip of a switch. Permits servos to be mounted in the most convenient way without concern for their rotation direction. The proper movement can then be selected when the installation is completed.
Servo Torque
The measure of power of a servo as measured in ounce-inches (the number of oz. the servo can push with a 1” control arm)
Servo Tray
A Servo tray is a plastic tray which facilitates mounting your servos easily in your model. The tray is molded to hold your servos securely and ensure positive control to your control surfaces. Different trays may hold anywhere from one to four servos and are shaped for different uses and servo positions in your model.
Snap Roll Button
This feature is found on more complex radios and is used to perform a snap roll maneuver by simply pressing one button. The function is usually programmable to give a combination of rudder, elevator and aileron control.
Sub Trim
A radio function which allows very precise electronic centering of servos. Switch Harness - The switch harness is mounted in your model and it connects between your receiver and the NiCd battery pack. It provides a power ON/OFF switch to the radio in your model and it also allows your charger to be connected to your model’s battery pack for charging.
Synthesized Frequency
A more sophisticated method of controlling the frequency of a radio control system than crystals. Synthesizing is more expensive than crystals, however, it gives you the opportunity of selecting from a whole band of frequencies on which to operate. This allows you to obtain a clear frequency at the field—no more waiting for a crystal controlled frequency to become clear.
Trainer System
The trainer system feature allows two transmitters of similar design to be connected together via a cord (trainer cord) so that one transmitter may be used by an instructor and the second one by a student when learning to fly. The instructor simply has to hold a switch on his transmitter to give the student’s transmitter full control. If the student gets into trouble, the instructor can release the switch and he has full control of the model.
Variable Trace Rate (VTR)
This radio function is similar to exponential except it uses two linear responses to determine the servo sensitivity on the first and second half of the control stick movement.
Same as a Dual Aileron Extension.

Programmable Mixing Terms
The following are some terms related to Programmable Mixing in Radio Systems:

Programmable Mixing is the electronic coupling of one channel to another. One control input will yield output to two different servos.

Aileron/Rudder Mixing
Adds rudder control when aileron is input from the transmitter aileron stick.
V-Tail Mixing
Used when there is a V-Tail on the aircraft rather than the conventional elevator and rudder. Each control surface of the V is connected to a separate servo. Operating the elevator control stick will move both surfaces up for back stick or both surfaces down for forward stick. Moving the rudder control stick left will move the left surface of the V down and the right surface up. Moving the rudder control stick to the right will move the left surface of the V up and the right surface down.
Flaperon Mixing
Mixes the Flap and Aileron functions so that when each aileron is connected to a separate servo (one servo plugged into the aileron channel and the other plugged into the flap channel), the surfaces will act as both ailerons and flaps, depending on the position of the controls.
Elevon Mixing
Mixes the elevator and aileron functions, especially useful for deltawing models where the elevator and ailerons are the same control surfaces. Each surface is connected to a separate servo (one servo plugged into the aileron channel and the other plugged into the elevator channel), the surfaces will act as both ailerons and elevator, depending on the position of the controls.
Flap/Elevator Mixing
Couples the flaps and elevators such that when the flaps are lowered, the elevator will be automatically adjusted to prevent pitching of the model.
Elevator/Flap Mixing
Couples the elevators and flaps such that when control is input to the elevators, the flaps will move in the opposite direction. This permits the model to perform tighter maneuvers in the pitch attitude.
Crow Mixing
Primarily used in gliders for spoiler action by mixing the flaps and ailerons. It is necessary for the ailerons to be using separate servos, plugged into separate channels and the flap servo to be independent of both aileron channels. Upon applying Crow Mixing, the flaps go down while both ailerons go up.
CCPM Mixing
Cyclic/Collective Pitch Mixing is used exclusively in helicopters and eliminates much of the complicated linkages required on a conventional setup. CCPM is a system which mounts 3 servos below the swashplate, with short, straight linkages directly to the swashplate at 120 degree intervals. With CCPM, complex collective and cyclic mixing is accomplished electronically, rather then mechanically. As a result, many parts are eliminated, along with excessive control system play—not to mention the quicker building time and lower required maintenance. Differential Ailerons - This type of mixing is accomplished by having separate servos on each aileron, plugging one into the aileron channel and the other into another unused channel. The two channels can be programmed to both operate from the aileron control stick, however the travel volume for each aileron may be adjusted separately giving more deflection in one direction (usually up) than in the other.