RC Glossary of Terms

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.

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 Tow

The act of an aircraft hauling a glider aloft and releasing it.

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.

Aft

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

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.

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.

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.

Airware

Exclusive software developed by Spektrum for air RC transmitters that includes all programming functions and features.

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.

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.

AS3X

A proprietary combination of gyros, sensors, and software that helps to stabilize and control the heading of RC aircraft models.

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).

AVC(Active Vehicle Control)

A proprietary combination of gyros, sensors, and software that helps to stabilize and control the heading of surface RC models.

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.

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.

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.

Bank

This is a measure of how far from level flight a plane’s wings are set during a turn or maneuver. It is measured in degrees of angle from level flight.

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.