RC Hobbies Glossary

Some airplanes, especially high-wing airplanes with flat-bottom airfoils, have a tendency to yaw in the opposite direction of the bank. This is most common when flying at low speeds with high angles. Adjusting the ailerons can help reduce the yaw.

Aerodynamics

Science of air in motion.

Aileron Extension

The Aileron Extension (also known as a 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).

Aileron/Rudder Mixing

Adds rudder control when aileron is input from the transmitter aileron stick.

Ailerons

Each side of this airplane has a hinged control surface, called an aileron, located on the trailing edge of the wing. Move the left aileron up and the right aileron down, and the airplane will turn or roll to the right. Perform the opposite actions, and the airplane will roll to the left. This is how you control the airplane's direction in flight.

Air Bleed Screw

Screw for adjusting the amount of air allowed to bleed into the carburetor during idle

Airfoil

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.

AM, or Ampilitude Modulation, was the primary means of modulation in R/C until recently. The control information is transmitted by varying the amplitude of the signal.

AMA

The Academy Of Model Aeronautics. The official national body for model aviation in the United States. The official national body for model aviation in the United States. AMA sanctions more than a thousand model competitions throughout the country each year, and certifies official model flying records on a national and international level.

Angle of Attack (AOA)

The angle between the chord of the wing and the relative wind that strikes the airfoil. The Angle of Attack is independent of the attitude of the sailplane with respect to the horizon.

Antenna

The telescoping tube that transmits the signal

ARF

Almost Ready to Fly, a model airplane that can be put together with a minimal amount of time.

ATS, Revolution Mixing, or Anti Torque Compensation

This is " Automatic Tail System". This refers to the radio mixing in a certain amount of tail rotor when the throttle / pitch is increased or decreased.

Autorotation

This is the term for when the engine is either not running or is put into a idle position with the "Hold" switch.

Axis

A line passing through a body about which the body revolves.

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Backplate

Cover over the rear of the crankcase of an engine.

Ballast

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.

Battery Cycling

To fully charge and discharge a battery to erase battery memory.

Battery Meter

The device used to monitor the strength of the transmitter batteries

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CA (Cyanoacrylate)

An instant type glue that is available in various consistencies (Thin, Medium, Thick, and Gel).

Capacity

The maximum amount of energy a battery can store.

Carburetor

By adjusting the needle valve in the carburetor, you control the engine’s lean/rich fuel mixture and determine the airplane's speed.

Center Line

An imaginary line drawn through the center of the aircraft from the nose through the tail.

Center of Gravity (CG)

Balancing point of an aircraft.

Charge Jack

The plug receptacle of the switch harness into which the charger is plugged to charge the battery.

Charger

This is the device used to charge/recharge batteries. If NiCad batteries are provided with the radio, a charger is usually provided as well.

Chicken Stick

A hand-held stick used to start a model airplane engine.

Clevis

The clevis connects the wire end of the pushrod to the control horn of the control surface. A small clip, the clevis has fine threads so that you can adjust the length of the pushrod.

Clunk

Located in the fuel tank, a clunk is weighted and ensures that the intake line has a steady supply of fuel.

Collective Pitch

This is the ability to vary the main blade pitch when the throttle is increased or decreased.

Computer Radio

By using the advanced programming functions of the transmitter, you can adjust the airplane without changing any mechanical structures.

Constant Drive Tail

This is a special autorotation clutch that will always drive the tail rotor even when the engine is off or in "Hold".

Control Horn

This arm connects the control surface to the clevis and pushrod.

Control Surfaces

The moveable part on the wing and tail that causes the aircraft to roll (aileron), pitch (elevator) or yaw (rudder).

Covering

The covering of an aircraft is the skin which is applied to the airframe, closing it in. 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.

Crankcase

Main body of the engine

Critical Angle of Attack

The angle of attack at which smooth airflow over the top of the wing stops.

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.

Crucifix Tail

Crucifix 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 advantages of both.

Crystal

The device that sets the radio frequency of the transmission

Cylinder

The section of the crankcase where combustion takes place

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Dead Stick

When the airplane is in flight gliding, without the engine running, it is called “dead stick.”

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.

Dihedral

The degree of angle (V-shaped bend) at which the wings intersect the plane is called dihedral. More dihedral gives an airplane more aerodynamic stability. trainer planes with large dihedral dispense with ailerons and use only the rudder to control the roll and yaw.

Direction of Flight

The relative direction of the wing in relation to still air

Dual Aileron Extension or Y-Harness

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 modeller 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 modeller can tailor the sensitivity of his model to his own preferences.

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Electric Starter

This is the small motor commonly used to start the airplane's engine.

Electrolyte

A caustic material found in batteries.

Elevator

The hinged control surface functions as an elevator, which you adjust to control the airplane's pitch axis. Pulling the transmitter's control stick toward the bottom of the transmitter adjusts the elevator upward, and the airplane begins to climb. Push the control stick forward, and the airplane begins to dive.

Elevator Mixing

Mixes the Elevator and Aileron functions, especially useful for delta-wing 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.

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.

Epoxy

A two-part resin/hardener glue that is used to put together models. Epoxy is extremely tough.

Expanded Scale Voltmeter (ESV)

This device is used to check the voltage of the battery pack.

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.

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Fail Safe (FS)

An electronically programmed mechanism in most PCM radios which automatically returns a servo or servos to neutral or a preset position in case of radio malfunction or interference.

Fin

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.

Flapperon 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.

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.

Flight Box

The box in which you store and transport your flying equipment is called a flight box.

Flight Pack or Airborne Pack

These interchangeable terms describe the radio equipment that is installed on the airplane.

Flying Stab

A flying stab is where the stabilizer/elevator is one complete unit which all moves to control the aircraft in pitch.

FM, or Frequency Modulation, is now the common method and is less prone to interference than AM. Information is transmitted by varying the frequency of the signal.

Foam Rubber

Material that is used to dampen the airplane's vibrations and protect the airplane's battery and receiver.

Four Way Wrench

Combination wrench with sizes to fit glow plug, prop nut, etc.

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.

Fuel Bulb

Rubber bulb used to transfer fuel to model tank

Fuel Overflow Line (Vent)

This line pressures the fuel tank and provides an even fuel flow to the engine. It also functions as an overflow line when the fuel tank is full.

Fuel Pickup Line

This line connects the fuel tank to the carburetor, usually with a clunk on the tank end to keep the fuel flowing while the aircraft is in flight. Fuselage. The main body of an airplane.

Fuselage

The main body of an airplane.

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Gimbal (or Stick)

The device that allows the user to input desired control movements into the transmitter

Glide Ratio

The glide ratio is defined as the distance travelled 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.

Glow Plug Clip/Battery

A 1.2-volt battery with a clip which is connected to your engine’s glow plug used to start the engine. You remove it once the engine is running smoothly.

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Handle

The device for carrying the transmitter

Harness

A device consisting of wires, switches, and a fuse that connects a motor to a battery.

Head

The component which forms the end of the compression chamber of the engine

High Wing

This term describes an airplane that has its wings mounted on the top of the fuselage.

Hinge

The hinges are the moving blades on the control surface that allow you to control the airplane's movement. All hinges must be glued properly and securely to prevent the airplane from crashing.

Horizontal Stabilizer.

The horizontal surface of the tail gives the airplane stability while in flight.

Hovering Pitch

This is the amount of pitch you will need to hover the helicopter. On average this is about 5 degrees. Most helicopter radio's will have a knob on the transmitter to vary the amount of pitch at the present hovering stick position.

Hovering Throttle

This is the amount of throttle you will need to hover the helicopter. On average this is about 50% throttle. Most helicopter radio's will have a knob on the transmitter to vary the amout of throttle at the present hovering stick position.

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Inverted

This is when the helicopter is inverted and the funtions of the Pitch, Elevator, Rudder can be reversed by the use of the "Inver" switch or the pilot can do it him or her self at the sticks. This is refered to as "Switchless" inverted.

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L/D

Lift divided by drag expressed as a ratio. Essentially the same as a glide ratio. Think of L/D as a glide slope, then, for a given amount of distance the sailplane moves forward, it drops a certain amount.

Landing Gear

The wheel and gear assembly the airplane uses to land. It is attached to the bottom of the fuselage.

Leading Edge

The front edge of a flying surface.

Long Stroke

The stroke of an engine refers to the distance the piston travels from top to bottom. In a Long Stroke engine this distance is a bit longer than on the standard engine making the engine a bit stronger in torque and operation lower RPM. Quite often an engine is "Long Stroke" if the stroke distance is greater than the diameter of the piston.

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mAh (Milliamp Hour)

A measure of a battery's capacity. The larger the number of milliamp’s the longer the battery cell will last.

Main Landing Gear

The wheel and gear assembly the airplane uses to land. It is attached to the bottom of the fuselage.

Minimum Sink

The speed at which a sailplane loses altitude most slowly. Usually expressed in feet per minute.

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.

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.

Mode III

The control stick configuration with the rudder and elevator being controlled by the right stick while the left stick controls the ailerons and throttle.

Mounting Lug

The section of the crankcase used to mount the engine to the airplane

Muffler

This device muffles engine noise and increases the back pressure from the engine’s exhaust stack, which can improve the airplane's performance at low speeds. Mufflers are usually required by R/C Clubs.

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Needle Valve

This mechanism within the carburetor adjusts the fuel mixture and throttle. Refer to your engine’s manufacturer instructions for directions on how to adjust the needle valve.

NiCad

This abbreviation stands for Nickel Cadmium, the chemical compound used in rechargeable batteries.

Nitro

Short for nitromethane, a fuel additive that improves an airplane's high-speed performance. Check your engine’s instructions to determine the ideal nitro content for your engine.

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.

NORRCA

National Organization for Racing Radio Controlled Autos.

Nose Gear

The part of the landing gear that is attached to the nose of the fuselage. The nose gear is usually connected to the rudder servo to help you steer the airplane on the ground.

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PCM

Pulse Code Modulation, the control information is in the form of a digital word rather than just a pulse width as in standard AM or FM. Using PCM adds additional protection against interference from various sources.

Peak Detection

Usually refers to a type of battery charger that automatically shuts off when a battery is fully charged.

Penetrate

To make progress against the wind.

Pitch

Degree of nose up or nose down from level to the horizon.

Pitch Axis

The horizontal plane on which the airplane’s nose is raised or lowered. By adjusting the elevator, you can raise the airplane's nose above the pitch axis (climb) or lower it below the pitch axis (dive).

Polyhedral

Polyhedral refers to the multiple angle 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.

Prop shaft

The main crankshaft which transfers the power of the engine to the propeller

Pushrod

The rigid mechanism that transfers movement from the servo to the control surface.

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 means of a set screw.

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RTR, RTF

Ready-to-Run; Ready-to-Fly - Ready to Run or Fly models come pre-assembled with radio equipment installed. These models still may require starting/charging equipment. e.g., battery, charger, glow igniter, fuel etc.

Receiver (Rx)

The receiver unit in the airplane receives your signals from the ground transmitter and passes the instructions along to the airplane’s servos.

Relative Wind

Direction that the air molecules strike the lead-ing edge of the wing.

ROAR

Radio Operated Auto Racing. National body to standardize and sanction R/C car and truck racing.

Roll Axis

The horizontal plane on which the airplane’s wings are raised or lowered. By adjusting the ailerons, you can drop a wing tip below the roll axis and cause the airplane to bank or roll.

Rudder

The hinged control surface on the vertical stabilizer that controls the airplane’s yaw. Moving the rudder to the left causes the airplane to yaw left; moving the rudder to the right causes it to yaw right.

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Servo

The servo transforms your ground commands into physical adjustments of the airplane while it’s in the air.

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 Output Arm

A removable arm or wheel that connects the servo to the pushrod. Also called servo horn.

Slipper Clutch

This is another special unit that is attached to the autorotation clutch will let the main blades turn the tail rotor when the engine is off or in "Hold". The difference between this and a "Constant Drive Clutch" is that this one will "Slip" a little so the tail rotor while spinning will not load the main rotors as much while in the "Hold" funtion doing a "Autorotation".

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.

Span

The maximum distance from wingtip to wingtip.

Speed Control

An electronic device that functions as a throttle for an electric motor. A speed control controls the speed or rpm of an electric motor.

Spinner

Term describing the nose cone that covers the propeller hub.

Spoiler

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

The Stabilizer is the fixed horizontal surface at the rear of an aircraft. It provides pitch stability for the aircraft.

Stall

Loss of lift resulting from exceeding the critical angle of attack.

Sub Trim

A radio function which allows very precise electronic centering of servos.

Switch Harness

This switch is commonly located on the fuselage and governs the on/off mechanism for the flight pace. Tachometer. A device the measures the engine’s RPM (rotations per minute) by counting light impulses that pass through the spinning propeller.

Symmetrical Wing

A Symmetrical Wing 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.

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Tachometer

A device the measures the engine’s RPM (rotations per minute) by counting light impulses that pass through the spinning propeller.

Thermal

Rising body of hot air that can take a sailplane to a great height.

Thread Locker

A liquid that solidifies; used to prevent screws from loosening due to vibration.

Throttle Stop Screw

Screw for setting the lower limit of the throttle movement

Torque Rods

Inserted into ailerons, these rigid wire rods run along the wings’ trailing edge, then bend downward and connect to the pushrods.

Tow-hook

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.

Trainer Airplane

Designed to fly with high stability at low speeds, a trainer model airplane allows new users some extra reaction time as they learn to control the airplane’s movements.

Transmitter (Tx)

The device used on the ground to transmit instructions to the airplane. Three transmitter modes are used in model airplanes. The most common is Mode II, where the left stick controls the throttle and rudder and the right stick controls the elevator and aileron.

Trim Lever

Slides used to adjust control surfaces during flight.

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Under-camber

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.

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V-Tail

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.

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.

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 movements.

Vertical Stabilizer

The vertical surface of the tail gives the airplane stability while in flight.

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Wheel Collar

The round retaining piece that anchors wheels in place on the axle.

Wing

Because wings provide the primary lift force on an airplane, adjustments to the wings affect the airplane’s movements while in flight.

Wing Area

The Wing Area is the total surface area of the wing of the aircraft, usually calculated by the wingspan times 7the wing chord, although more complex calculations are used on unconventional wing plans.

Wing Chord

The Wing Chord of an aircraft is distance from the front or "leading edge" of a wing to the back or "trailing edge".

Wing Loading

Wing loading is the weight of the aircraft divided by the wing area. It is designated 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

The maximum distance from wingtip to wingtip.

Wing Tip

The very outer end of a wing.

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Yaw Axis

The vertical plane through which the airplane’s nose passes as it yaws to the left or to the right. The rudder controls the yaw axis.

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Z-Bend

The wire ends of pushrods have Z-shaped bends, which attach to the servo.

Z-Bend Pliers

Used for crimping wire ends into Z bends.