R/C Dictionary
3D: Term describing a type of flight pattern, which is characterized by the performance of very specialized aerobatic maneuvers below the model's normal stall speed. Examples include torque rolls, 'walk in the park', harriers, hangers, etc.
3F: Slang abbreviation for flip flop flying. Similar to 3D, but without the finesse.
ABC: Aluminum-Brass-Chrome. The components used in the production of non-ringed engines. These engines use an aluminum piston, and a chrome or nickel plated brass sleeve. The engine is harder to turn over and start due to the tight fit between the piston and cylinder. This tight fit is what makes the engine more efficient, and powerful. ABC engines must be run in for best performance.
ABL: Advanced Bimetallic Liner. Specialized form of ABN. Instead of a single-step, single-material plating, the ABL Plating process is based on a layered approach made possible by two OS-developed hard-nickel alloys. The first alloy is used as the bottom (bonding) layer, to fuse the top layer to the brass liner. The second alloy, developed for superior hardness, forms the top layer. Together, they create a barrier that protects the liner against excessive heat and wear.
ABN: Aluminum-Brass-Nickel. The components used in the production of non-ringed engines. These engines use an aluminum piston, and a nickel plated brass sleeve. The engine is harder to turn over and start due to the tight fit between the piston and cylinder. This tight fit is what makes the engine more efficient, and powerful. ABN engines must be run in for best performance.
ABS Plastic: Acetyl Butyl Styrene. A type of plastic that can be thermo-formed.
Accelerated Stalls: Occurs above the usual power-off stall speed when too much elevator control is input too quickly. This type of stall is usually far more violent than a wings-level, power-off stall. However, an airplane can be stalled at any speed if too much elevator is applied to fast.
Adjustable Travel Volume (ATV): ATV allows you to preset the maximum travel of a servo to either side from its neutral position. Such settings help tailor control action to suit your flying or driving style.
Adverse Yaw: The tendency of an airplane to yaw in the opposite direction of the roll. For instance, when right aileron is applied, the airplane yaws to the left, thus opposing the turn. Adverse yaw is common in trainer type airplanes having flat bottom wings. It is most noticeable at slow speeds and high angles of attack, such as during takeoffs and when stretching a landing approach. Caused by the unequal drag of the upward and downward deflection of the ailerons, this undesirable trait can be minimized by setting up the ailerons with Differential Throw or by coordinating the turns, using the aileron and rudder controls simultaneously. (See Differential Throw.)
Aero-elastic flutter: (propeller) Is speculated to be a dominant mechanism causing rapid fatigue failure near a tip when insufficient or destabilizing tip stiffness exists. The interaction between variable loading and deflection induces a high frequency vibration with unpredictable magnitude.
Aero Tow: The act of an aircraft hauling a glider aloft and releasing it.
Aft: Towards the rear. Used such as: "...with an aft center of gravity....".
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. Marvel Mystery Air tool Oil is one of the best.
Ailerons: Hinged control surface located at the trailing edge of each wing, that provides control of the airplane about the roll axis. Ailerons move in opposite directions in order to provide lift on one wing and "stall" on the other, in the process "rolling" the aircraft in the direction of the wing with the raised aileron.
Aileron Differential: Adverse yaw, especially on flat-bottom wings, is caused by the difference in airflow density between the bottom and top of the wing. The airflow along the wing’s bottom is denser than it is over the top of the wing. Therefore, the aileron moving down into this denser air creates more drag than the “up” aileron moving into the less dense airflow on top of the wing. The greater drag on just one side of the wing, the side with the down aileron, forces the wing, and the attached fuselage, to yaw in that direction. At slow airspeeds this yawing effect is more powerful, and happens faster, than the rolling effect caused by the ailerons. The airplane’s nose first swings away from the turn’s intended direction and only then begins to turn correctly once the roll begins.
Airfoil: The shape of the wing when looking at its profile. Usually a raindrop type shape.
AMA: The Academy Of Model Aeronautics . 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: The angle that the wing penetrates the air. As the angle of attack increases so does lift and drag, up to a point.
Anhedral: is the opposite of dihedral, having the wing tip centerline lower than the wing root centerline. Anhedral is generally used to aid in the instability of an aircraft to make it more aerobatic.
Note that Anhedral is correctly measured as the vertical distance from the centerline of the root rib to the centerline of the wing tip.
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.
ARF: A prefabricated model - Almost Ready to Fly. Well, OK, so what does "almost" mean? Usually it will take anywhere from 30 minutes to five or six hours....or more if you are just starting. Surprisingly, some modelers like to build models...sometimes from "kits" which have some items pre-cut and contain some of the non-wood parts needed to finish the model. Usually, however, NONE of the electronic items are included in an ARF except, perhaps, the motor...check the specs carefully before you purchase.
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 maneuvering, 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.
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).
AUW: All Up Weight - The total weight of the project. This includes everything needed to make it run or fly. Receiver, servos, batteries, etc. The all up weight of the project.
Auxiliary channel: any radio channel function other than the four basics (aileron, rudder, elevator and throttle).
Axial Roll: This type of roll is one where the aircraft’s fuselage remains exactly on the line of flight while the wings roll about it. Except for a very few jet fighters at high speed (the F-5 for one), no full size aircraft can perform a true axial roll. Most aircraft, especially trainers, roll about the line of flight, called a Barrel Roll.
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.
Bank: This is a measure of how far from level flight a plane’s wings are set during a turn of maneuver. It is measured in degrees of angle from level flight.
Ballast: 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.
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.
Barn Door Ailerons: Larger, built up ailerons rather than an aileron from a simple strip of solid wood like some kits have.
BB: These letters usually designate a ball-bearing supported crankshaft in an R/C engine or ball bearings in a better servo. This makes the engine run smoother and last longer.
BEC (battery eliminator circuit): A feature of some speed control units that permits both the motor and the receiver to be powered by the same battery.
BHP: Brake horsepower. A measurement standard used by manufacturers to help consumers compare engines. NOTE: BHP is measured at the maximum operating RPM of the engine, which may not be the RPM level at which your engine will provide maximum life and consistent performance.
Binding: Occurs when the friction at a joint is stronger than the linkage.
Blind Nut: (Also called a T-Nut) A pronged nut that is pulled into a surface such as wood so that it can not turn when a bolt is tightened into it. Blind nuts are typically used in situations where it would be impractical to use a tool, such as pliers, to hold the nut while the fastener is being tightened.
Boundary Layer: The thin layer of air immediately adjacent to a body moving through the air.
Bulkhead: A vertical former inside a fuselage.
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.
Butterfly: Also known as crow. A mix which activates up flaperons and down inner-most flaps for gliding speed control without spoilers or airbrakes. Crow (or butterfly) is only used for landing or perhaps for diving out of a thermal.
CA (cyanoacrylate): A modern hobby adhesive that cures very quickly. (read about how its made here)
CG: Center of Gravity. Describes a central point in a given body, where all weight is considered to be concentrated. A central balance point.
Cabane: A strut attaching a wing to the fuselage when the wing is above the fuselage such as biplanes and parasol aircraft.
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: An aircraft having the horizontal stabilizer forward of the main wing rather than in the conventional position behind it. Canard aircraft are theoretically more efficient because both the horizontal stabilizer and the wing provide upward lift. The horizontal stabilizer of a conventional aircraft provides downward lift to stabilize the aircraft resulting in an overall decrease of the aircraft's total lift.
Carburetor: The part of the engine which controls the speed or throttle setting and lean/rich mixture via setting of the needle valve.
Castor Oil: Oil from a castor bean which is often used in glow fuels for lubrication and cooling.
Center of gravity (CG): The balance point of a model airplane. For modeling 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.
Center of Lift (COL): The location on the top of the wing where the sum of all lifting forces is located.
Centrifugal loads: (propeller) are very predictable, given rotational speed and mass density distribution of a blade. Their contribution to total stress is relatively small.
Chandelle: A very steep climbing turn where the airplane makes a 180° change of direction.
Channel: The number of functions your radio can control. Example: An 7 channel radio has 7 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.
Chicken Stick: A hand-held stick used to "flip start" a model airplane engine.
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.
Clevis: 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.
Clunk: Term used to describe the weighted end of the fuel pickup line in the fuel tank. The purpose of this is to ensure that the fuel pickup is always in the fuel supply, even when inverted
Collet: A slotted jaw that allows a limited range of bits to be placed in a tool such as a router, moto-tool or pin vice.
Coning: This effect is the bending of the rotor or propeller blades when stressed.
Control linkage: Any linkage transmitting servo movement to a control surface.
Control surface: A movable surface such as elevator, rudder and aileron.
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.
Covering: 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.
Cowl or Cowling: The large molded fairing around an engine. It serves two purposes: It helps the airflow go smoothly around the front of the airplane, and also provides a proper path for cooling air around the engine.
Crab: When an aircraft flies at a sideways angle relative to the direction being traveled. Can be caused by a crosswind or may be flown intentionally to reduce altitude without increasing forward airspeed while on landing approach.
Crow: See "Butterfly"
Crucifix tail: 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.