Terminology Help

360, 540, etc.
Number describing degrees in an arc. A 360 represents one full turn through an axis. A 360 turn, for example, is a flat turn where the aircraft does not roll its wings but rather just 'slides' through 360 degrees turning on rudder only.
For helis: A 540 stall turn, for example, describes a one and one half revolution spin at the apex of a vertical stall, which results in the helicopter resuming nose forward flight before recovery.

3D
Term describing a type of flight pattern, which is characterized by the performance of very specialized aerobatic manoeuvres below the model's normal stall speed. Examples include torque rolls, 'walk in the park', harriers, hangers, etc.
For helis: combining two or more manoeuvres into one manoeuvre. Examples: rolling circle, inverted backwards loop.

3F
Slang abbreviation for flip flop flying. Similar to 3D, but without the finesse.
ATL = Adjustable Throttle Limiter
High-end feature which adjusts to bring full servo potential within the limits of bind-free servo travel. Ideal for throttle control, or for more effective braking in gas racing.
ATV/EPA = Adjustable Travel Volume/End Point Adjustment
Allows separate adjustments of maximum servo travel to both sides of neutral. Helps tailor outputs for different control styles. Please refer to this FAQ for more information.

ARF
Almost Ready to Fly. A kit which is mostly pre-assembled, usually requiring installation of few parts, engine, and radio gear. Almost Ready to Fly name compares to a kit, which is a package of parts which require assembly.

ATV
Adjustable Travel Volume. Used on many radio transmitters to limit, or extend, maximum throw of a servo. ATV can indicate having a single adjustment which affects both ends of the servo (known as AST) or one adjustment for each end of the servo throw (known as EPA).

Aerobatics
The act of performing 'acrobatic' or stunt manoeuvres in the air such as loops, rolls, etc. For extensive information on aerobatics, consider purchasing A Look at Aerobatics (GPMZ0220), written by two-time U.S. National IMAC Aerobatic Freestyle Champion, Mike Cross.

After Run Oil
A lubricant designed to displace unburned fuel in the engine after running. The fuel can accelerate corrosion on some engine parts. By using an after run oil, the fuel is displaced, and a protective coating lines sensitive engine parts. This is an inexpensive engine insurance, and promotes long engine life. There are several good after run oils on the market.

Ailerons
Control surfaces usually on the wing, often near the tips. Used to bank the aircraft. They work in opposite directions (when one goes up, the other goes down.) One aileron raising forces air to push that side of the wing down, causing the model to roll in that direction. So, to roll right the right aileron raises. They control the airplane around the roll axis.

Airfoil
The shape of the wing when looking at its profile. Usually a raindrop type shape.

Angle of Attack
The amount of pitch at which an airfoil is flying. By adjusting the angle of attack, the efficiency of the wing/blade is effected. More precisely, the angle between the chord of an airfoil and the wind.

Area
The number of square inches (or feet) of the wing. It's the wingspan multiplied by the wing's chord. The area of a tapered wing is the wingspan multiplied by the average chord.

Aspect Ratio
The wingspan divided by the chord. Aspect ratio is important where a wing's efficiency is concerned. A short aspect ratio (short wings) is better for manoeuvring, since it allows a high roll rate. Short wings are also stronger than long wings. Gliders use high-aspect ratio wings (long, skinny wings) because they are more efficient for soaring flight. Example: 10 ft. wingspan with a 1 ft. chord has an aspect ratio of 10.

Axis
The line around which a body rotates.

Aft
Towards the rear. Used such as: "...with an aft center of gravity...."

Aileron Differential
Creating larger upward aileron travel than downward aileron travel to help minimize the model "dragging" the drooped aileron which causes a model to yaw with aileron input.

Ailerons
Hinged control surfaces located on the trailing edge of the wing, one on each side, which provide control of the airplane about the roll axis. The control direction is often confusing to first time modellers. For a right roll or turn, the right hand aileron is moved upward and the left hand aileron downward, and vice versa for a left roll or turn.

Ailevators
Twin elevator servos plugged into separate channels used to control elevator with the option to also have the 2 elevator servos act as ailerons in conjunction with the primary ailerons.

Airfoil
The shape of the wing when looking at its profile. Usually a raindrop type shape.
For helis: The rotor disk is the effective wing, and airfoil refers to the shape of the blades.

Amphibian
An aircraft that can fly off of water or land. The wheels retract into the hull or floats, depending upon the type of aircraft. An amphibian can land on water and then extend the landing gear to allow it to pull up onto the shore. Many seaplane bases had ramps to allow the airplanes to pull up onto dry land parking areas.

Angle of attack
The angle that the wing penetrates the air. As the angle of attack increases so does lift, up to a point (and drag).

Articulated Rotor
This is borrowed from full sized helicopters, and is a rotor head which allows the blades to flap, drag and feather.

Aspect Ratio
The wingspan divided by the chord. Aspect ratio is important where a wing's efficiency is concerned. A short aspect ratio (short wings) is better for manoeuvring, since it allows a high roll rate. Short wings are also stronger than long wings. Gliders use high-aspect ratio wings (long, skinny wings) because they are more efficient for soaring flight. Example: 10 ft. wingspan with a 1 ft. chord has an aspect ratio of 10.

Autorotation
The ability of a rotary wing aircraft to land safely without engine power. This manoeuvre uses the stored energy in the rotor blades to produce lift at the end of decent, allowing the model to land safely.

BEC = Battery Eliminator Circuitry
Allows receiver to draw power from a main battery pack, eliminating the need for (and weight of) a receiver battery.

Ball Bearing
Servo's output shaft is supported with bearings for increased performance and accuracy.

Ball Link
Connection using a ball, and a link which rotates on the ball. Used to connect the servo to a control surface or lever.

Backlash
Term describing the amount of play between gears, or gear mesh. If too loose, the gear can slip, or strip the teeth. Too tight, and excessive wear is caused.

Base Load Antenna
A rigid, short antenna mounted to the model. Used to replace the longer receiver antenna.

Bell and Hiller
Control system used in helicopters. Changes pitch of blades in relation to their position via a swash plate. A flybar with paddles is used to gain responsiveness. The two systems are linked with Control Levers.

Binding
What occurs when the friction at a joint is stronger than the linkage.

Boring holes in the sky
Having fun flying an R/C airplane, without any pre-determined flight pattern.

"Buddy" or Trainer Box
Two similar transmitters that are wired together with a "trainer cord." This is most useful when learning to fly-it's the same as having dual controls. The instructor can take control by using the "trainer switch" on his transmitter.

Butterfly
Also known as crow. A mix which activates up flaperons and down inner-most flaps for gliding speed control without spoilers or airbrakes.

Barn Door Ailerons
Larger, built up ailerons rather than an aileron from a simple strip of solid wood like some kits have.

Blade Balancer
Usually called a 'prop balancer' for aircraft. Used to ensure that the propeller and spinner are equally balanced side-to-side to avoid vibration problems.

Blade Strike
Term describing the event of a propeller blade hitting another object. Although this can seem like a minor impact, the blades should be carefully and thoroughly inspected, as structural integrity is often compromised, producing an unsafe condition. If any question remains, do not fly until the blades are replaced.

Buddy Box
Training method utilizing two transmitter control boxes, linked together. The trainer radio has override control, which the instructor uses to take control when the trainee looses control, or becomes disoriented.

CA
Abbreviation for cyanoacrylate. An instant type glue that is available in various viscosities (Thin, Medium, Thick, and Gel). These glues are ideal for the assembly of wood airplanes and other materials. NOTE: Most CA glues will attack foam.

CCPM
Cyclic-Collective-Pitch-Mixing. Type of swash plate mixing which requires a radio with CCPM mixing functions. This uses three servos to control the cyclic, while all three work together to raise and lower the swash plate for collective control. Please refer to the swash plate FAQ for further information.

CG = "Centre of Gravity"
For modelling purposes, this is usually considered-the point at which the airplane balances fore to aft. This point is critical in regards to how the airplane reacts in the air. A tail-heavy plane will be very snappy but generally very unstable and susceptible to more frequent stalls. If the airplane is nose heavy, it will tend to track better and be less sensitive to control inputs, but, will generally drop its nose when the throttle is reduced to idle. This makes the plane more difficult to land since it takes more effort to hold the nose up. A nose heavy airplane will have to come in faster to land safely.

Camber
If you draw a line through the center of the airfoil that's exactly half-way between the top and bottom surface, you get the mean airfoil line. Depending upon the airfoil, it can be straight or curved. This curve is called the "camber" of the airfoil. If it has a lot of curve, the airfoil is said to be "highly-cambered".

Canard
The horizontal surface forward of the wing used to control pitch. It's found on very few aircraft. Also the word used to describe aircraft that have a main wing and a horizontal control surface in the nose...also called, "tail first" aircraft.

Carburettor
The part of the engine which controls the speed or throttle setting and lean/rich mixture via setting of the needle valve.

Chandelle
A very steep climbing turn where the airplane makes a 180o change of direction.

Channel
The frequency number used by the transmitter to send signals to the receiver. If radios transmit on the same frequency, or channel, glitching will occur in the active receiver on that channel. This is due to conflicting signals sent by the two radios. Flying sites should have a frequency control system to ensure that only one radio operates on any given channel at one time. This is usually a board with some type of marker for each channel. If the marker is not available, someone else is using that channel. Do not use your radio unless you are sure you are the only one on the frequency.

Channel
The number of functions your radio can control. Ex: an 8 channel radio has 8 available servo slots used for separate control surfaces or switches. These channels can also be mixed on many radios, for such functions as collective, which increases pitch when throttle is increased.

Charge Jack
The plug receptacle of the switch harness into which the charger is plugged to charge the airborne battery. An expanded scale voltmeter (ESV) can also be plugged into it to check battery voltage between flights. It is advisable to mount the charge jack in an accessible area of the fuselage so an ESV can be used without removing the wing.

Charger
Device used to recharge batteries and usually supplied with the radio if NiCad batteries are included.

Chord
The "depth" of the wing, its distance from leading edge to trailing edge. One of the components used to determine wing area. May vary from root to tip.

Control Surface
Any one of the various moveable portions of the wings, tail surfaces, or canard.

Conventional Gear
The landing gear arrangement where the airplane has a main gear and a tail wheel.

Coreless motor
In a conventional servo, the motor has a steel core armature wrapped in wire that spins inside the magnets. In a coreless design, the armature uses a thin wire mesh that forms a cup that spins around the outside of the magnet eliminating the heavy steel core. A coreless motor does not have magnets as standard servo motors do, so they have a smoother, more constant, and stronger action. Regular servo motors have either 3 or 5 magnets (poles) which when the armature is between these, the servo motor is at its weakest.

Cowl
The large moulded fairing around an engine. It serves two purposes when done right: It helps the airflow go smoothly around the front of the airplane, and also provides a proper path for cooling air around the engine.

Cyclic
Term used for the horizontal controls used to determine the attitude of the helicopter. Also known as elevator and aileron.

DSC = Direct Servo Control
High-end convenience feature which allows control/adjustment of servo function without sending signal through receiver. Requires optional DSC cord (FUTM4250) and DSC-compatible receiver such as R149DP and R113IP.

Dead Stick
A term used to describe un powered flight (glide) when the engine quits running.

Dialled In
Slang term for the condition in which the model is set up to fly smoothly and predictably. This is the state where the mechanics and electronics work together to produce the best performance.

Differential
Uneven movement in each direction of a control surface. Usually used when discussing ailerons or when describing an undesired unevenness in movement of other controls.

Digital
Please see the digital servo web page: http://www.futabarc.com/servos/futm0211.html

Diode
An electronic component which only allows current to flow one direction. Protects the transmitter against reverse polarity or power surges during charging.

Dorsal Fin
An extension of the vertical fin forward of the main part of the fin, and against the fuselage. On the top, or "dorsal" side of the aircraft.

Drag
The air resistance to forward motion. Drag can be increased with the use of certain types of devices installed on the aircraft, such as spoilers, airbrakes, or flaps. Old-style aircraft with lots of supporting wires had very large amounts of drag, while modern aircraft such as military jets, have very low drag.

Dual Conversion
A type of receiver that converts the incoming frequency through two intermediate stages. This tends to eliminate the type of interference known as "image". With high-precision components, it also allows the receiver to be much more precise in selecting the incoming channel it accepts. This is what helps the receiver to be very narrow-band.

Dual Rates
A switch that can make controls more or less sensitive. Lower rates are better for beginners, who tend to over control.

Elevator
Hinged control surface located at the trailing edge of the horizontal stabilizer, which provides control of the airplane about the pitch axis and causes the airplane to climb or dive. The correct direction of control is to pull the transmitter elevator control stick back, toward the bottom of the transmitter, to move the elevator upward, which causes the airplane to climb, and vice versa to dive.

Elevator-to-Flap Mixing
Used to apply flaps along with elevators to increase lift, allowing modeler to fly at slower speeds, make tighter loops or turns, etc.

Empennage
The vertical and horizontal tail surfaces of an airplane.

Epoxy
A two-part resin/hardener glue that is extremely strong. It is generally available in 6 and 30-minute formulas. Used for critical points in the aircraft where high strength is necessary.
Expanded Scale Voltmeter (ESV)
Device used to read the battery voltage of the on- board battery pack or transmitter battery pack.

Exponential Rate
Offers servo travel that is not directly proportional to stick travel. Control response is milder below half-stick, but becomes increasing stronger as stick travel approaches 100%. Great for aerobatics and trouble situations.

FM
Frequency Modulation. This describes the mode of transmission of radio signal from transmitter to receiver.

Fail Safe
A safety feature which turns a servo to a preset position if the signal is lost or interrupted. Please refer to the FAQ for more information. Additionally, battery failsafe is a safety feature which brings the throttle servo down to idle as a warning that the receiver battery's voltage is getting dangerously low. Please refer to the FAQ for more information.

Fairing
A shaped area used to smooth out, streamline, or "fair", the joint between two members of an airplane. A wing fairing joins the wing and fuselage. A landing gear fairing streamlines the landing gear struts, and wheel fairings (wheel "pants") streamline the bulky shape of the wheels.

Field charger
A fast battery charger designed to work from a 12-volt power source, such as a car battery.

"Figure 9"
Can be an "official" competition manoeuvre, or a badly-done loop. When the model flies over the top of a loop and picks up too much speed, the momentum prevents it from maintaining a loop's round shape.

Fin, Vertical Fin
The fixed portion of the vertical tail surface.

Flaperons
The movement of two aileron servos, both in the same direction at the same time, acting as flaps.

Flaps Hinged control surface located at the trailing edge of the wing inboard of the ailerons. The flaps are lowered to produce more aerodynamic lift from the wing, allowing a slower takeoff and landing speed. Flaps are often found on scale models, but usually not on basic trainers.

Flare
The point during the landing approach in which the pilot gives an increased amount of up elevator to smooth the touchdown of the airplane.