Yaw

The tendency of an radio controlled aeroplane to yaw in the opposite direction of the roll. For instance, when right aileron is applied, the radio controlled aeroplane yaws to the left, thus opposing the turn. Adverse yaw is common in trainer type radio controlled aeroplanes 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 effect can be minimized by setting up the ailerons with Differential Throw or by coordinating the turns, using the aileron and rudder controls simultaneously.

Yaw Axis

  The RC aeroplane axis controlled by the rudder. Yaw is illustrated by hanging the RC aeroplane level by a wire located at the centre of gravity. Left or right movement of the nose is the Yaw movement.

Ailerons

  Hinged control surfaces located on the trailing edge of the wing, one on each side, which provide control of the radio controlled aeroplane 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.

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.

CG ("Centre of Gravity")

  For modelling purposes, this is usually considered -- the point at which the radio controlled aeroplane balances fore to aft. This point is critical in regards to how the radio controlled aeroplane reacts in the air. A tail-heavy plane will be very snappy but generally very unstable and susceptible to more frequent stalls. If the radio controlled aeroplane 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 radio controlled aeroplane will have to come in faster to land safely.

Dead Stick

  A term used to describe unpowered flight (glide) when the engine quits running.

Differential Throw

  Ailerons that are set up to deflect more in the upward direction than downward are said to have Differential Throw. The purpose is to counteract Adverse Yaw.

Dihedral

  The V-shaped bend in the wing. Typically, more dihedral causes more aerodynamic stability in an radio controlled aeroplane, and causes the rudder to control both the roll and yaw axis. This is why some trainers and sailplanes require only 3 channels of radio control--I.e., having no ailerons.
 
Down Thrust

  Downward angle of the engine relative to the centreline of the radio controlled aeroplane. Down thrust helps overcome the normal climbing tendency of flat bottom wings.

Elevator

  Hinged control surface located at the trailing edge of the horizontal stabilizer, which provides control of the radio controlled aeroplane about the pitch axis and causes the radio controlled aeroplane 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 radio controlled aeroplane to climb, and vice versa to dive.

Endpoint Adjustment

  This radio feature adjusts the length of servo travel in one direction (a single channel will have adjustments for two endpoints).  If your plane rolls faster one way than the other, endpoint adjustments can correct the problem.

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 radio control aeroplane.  Flight Pack (or Airborne pack) - All of the radio equipment installed in the radio control aeroplane, ie., Receiver, Servos, Battery, Switch Harness.

Flutter

  A phenomenon whereby the elevator or aileron control surface begins to oscillate violently in flight. This can sometimes cause the surface to break away from the aircraft and cause a crash. There are many reasons for this, but the most common are excessive hinge gap or excessive "slop" in the pushrod connections and control horns.  If you ever hear a low-pitched buzzing sound, reduce throttle and land immediately.

Frequency Module

  A frequency module plugs into the transmitter and enables you to change the channel number your radio broadcasts on. 

Horizontal Stabilizer

  The horizontal tail surface at the back of the fuselage which provides aerodynamic pitch stability to the radio control aeroplane.

Lateral Balance

  The left-right or side-to-side balance of an radio control aeroplane. An radio control aeroplane that is laterally balanced will track better through loops and other manoeuvres.

Leading Edge (LE)

  The very front edge of the wing or stabilizer. This is the edge that hits the air (or trees) first.

Mixing (Coupling)

  Two radio control channels can be coupled together so that they move together when only one control channel is activated. Many 1/4 scale models require a combination of aileron and rudder to turn. Mixing does this electronically at the transmitter. V-tailed models, where the two halves of the V-tail must move not only together but independently, are another use of control mixing.  One-Point Landing  Synonymous with "stuffing it in." Something I hope you never do this.

Prop Pitch

  Props are designated by these two numbers, for instance 10 - 6. The first number is the prop's length, 10" and the second number is the pitch or angle of the blades. The 6 represents the distance the propeller will move forward in one revolution, in this case 6".

Roll Axis

  The radio control aeroplane axis controlled by the ailerons. Roll is illustrated by holding the radio control aeroplane by the nose and tail. Dropping either wingtip is the roll movement. This is used to bank or turn the radio control aeroplane. Many aircraft are not equipped with ailerons and the Roll and Yaw motions are controlled by the rudder. This is one reason why most trainer aircraft have a larger amount of dihedral.

Rudder

  Hinged control surface located at the trailing edge of the vertical stabilizer, which provides control of the radio control aeroplane about the Yaw axis and causes the radio control aeroplane to Yaw left or right. Left rudder movement causes the radio control aeroplane to Yaw left, and right rudder movement causes it to Yaw right.

Stall

  What happens when the angle of attack is too great to generate lift regardless of airspeed. (Every airfoil has an angle of attack at which it generates maximum lift -- the airfoil will stall beyond this angle).

Tip Stall

  The outboard end of one wing (the tip) stops developing lift, causing the plane to roll suddenly in the direction of the stalled wing. This situation is not fun when you are only a few feet off the runway trying to land.

Washout

  An intentional twist in the wing, causing the wing tips to have a lower angle of attack than the wing root. In other words, the trailing edge is higher than the leading edge at the wing tips. Washout helps prevent tip stalls.

Wing Root

  The centreline of the wing, where the left and right wing panels are joined.

Y-Harness

  Two servos can be plugged into one channel with a Y-harness. The two servos will then operate simultaneously. It is most often used in areas where the strength of one servo is not adequate.