Helicopter Glossary

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 maneuvers below the model's normal stall speed. Examples include torque rolls, 'walk in the park', harriers, hangers, etc.
For helis: combining two or more maneuvers into one maneuver. Examples: rolling circle, inverted backwards loop.

3F
Slang abbreviation for flip flop flying. Similar to 3D, but without the finesse.

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ATL = adjustable Throttle Limiter
High-end feature which adjts 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 Adjtment .

Allows separate adjtments of maximum servo travel to both sides of neutral. Helps tailor outputs for different control styles.

Activating (Arming) Switch
An external switch that prevents the electric motor from accidentally turning on.

adjustable Function Rate (AFR)
Similar to ATV, AFR allows end point adjtment independent of Dual Rate or Exponential settings.

adjustable Travel Volume (ATV)
End Point Adjtment, ATV you can independently preset the maximum travel of a servo on either side of neutral.

Adverse Yaw
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. Adjting the ailerons can help reduce the yaw.

Aerodynamics
Science of air in motion.

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 caes a model to yaw with aileron input.

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).

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 confing to first time modelers. 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.

Air Bleed Screw
Screw for adjting the amount of air allowed to bleed into the carburetor during idle

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.

AM
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 thoand model competitions throughout the country each year, and certifies official model flying records on a national and international level.

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).

Antenna
The telescoping tube that transmits the signal.

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.

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

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 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.

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

Axis
The line around which a body rotates.

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

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.

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 caed.

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

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

Bell and Hiller
Control system used in helicopters. Changes pitch of blades in relation to their position via a swashplate. 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 eful 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.

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CA
Abbreviation for cyanoacrylate. An instant type glue that is available in vario 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 swashplate 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 swashplate for collective control.

CG = "Center of Gravity"
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 sceptible 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.

Capacity
The maximum amount of energy a battery can store.

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

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.

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.

Chicken Stick
A hand-held stick used to 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 connects the wire end of the phrod 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 phrod.

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

Collective Pitch

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

Fore, Forward
Towards the front. used such as "...the forward edge of the rib...", or as in "...with fore and aft movement...."

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.

Frequency Control
The FCC has allowed the 72MHz (72.010 - 72.990) band to be used for R/C aircraft operations. This band is divided up into many different channels in which you can choose a radio system. You should be aware that certain areas have frequencies in which there is pager interference. This is why it is always a wise move to check with your local hobby shop to find out any channels that may be troublesome in the area you wish to fly. The FCC has allowed band 75MHz (75.410 through 75.990) for ground model use only (robots, battlebots, cars, boats), 50MHz (50.800 - 50.980) is allocated only to Amateur HAM license holders for R/C use (and only at 1W maximum power output.)

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 body of an airplane.

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Gain
Gyro sensitivity. When too low, the tail will not hold position well. When too high, the surface being dampened by the gyro will tend to wag, or hunt for center.

Gimbal (or Stick)
The device that allows the er 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.

Glitch
Momentary radio problem that never happens unless you are over trees or a swamp.

Glow Plug
The heat source for igniting the fuel/air mixture in the engine. When starting the engine a battery is used to heat the filament. After the engine is running, the battery can be removed. The wire filament inside the plug is kept hot by the "explosions" in the engine's cylinder. See next heading and "Idle Bar" plug.

Grease-in
A very smooth, gentle landing without a hint of a bounce.

Gyro
A gyro is an electro-mechanical, or electronic device which aids in the control of an R/C model. The gyro senses motion in one axis, and directs the servo to counter that motion. The sensor, which can be a mechanical gyroscope, or an electronic piezo crystal, detects unwanted movement. The gyro then instructs the servo to counter for that motion. At all times, the radio commands will override the gyro command. The level of control the gyro had is adjusted by the GAIN setting.
Mechanical Gyro: uses a mechanical gyroscope (similar to the child's toy) to sense movement.
Piezo Gyro: uses a piezo crystal to sense movement.
Non-Heading-hold vs. heading hold: A standard (nonHH) gyro senses movement and makes an effort to counter that movement as long as it feels it. Therefore, it is NOT going to return the model to the exact heading prior to the movement. Heading Hold (or AVCS) gyros will lock the model into one position, and accurately correct for movement by sensing rate of change and returning at that same rate.
SMM technology: utilizes a microchip to sense movement and provide all readings. Experiences minimal effect from temperature change, commonly known as 'temperature drift' which affects piezo and some mechanical gyros.

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Handle
The device for carrying the transmitter

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

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

Heading Hold
This describes a type of Gyro which senses rotation, and maintains direction. This is accomplished by sensing the rate of motion, and the time of motion, then compensating for the distance. While this sounds complicated, the effect is that if you have the model dialed in, and point the nose north, with a heading hold gyro on the yaw axis the model will continue to face north until you command it to yaw. See also Heading Lock. This is not recommended for aircraft use while in flight due to the requirement to use YAW (rudder) command to turn the model. Often used for ground use only for perfect take off and landing runs.

Heading Lock
Slang term for Heading Hold Gyro.

HEC
High Efficiency Clock. High motor pulse frequency, giving very fine control of motor speed, and saving current in the part-load range. Produces longer running times and reduces the thermal load on the motor.

Helicopter Radio
A remote control radio system designed specifically for use with helicopter models. The helicopter radio differs from an aircraft radio in a few ways. First, the heli radio needs mixing functions specific to helicopters, and Usually a minimum of five channels. Collective mixing for collective pitch helicopters is a necessity. Second is the throttle stick, which is ratcheted in airplane transmitters, will not have the clicking feel on the heli version. This is due to the precise control needed on the heli collective stick to achieve and stain a controlled hover. The specific radio requirements will vary from er to er, and the parameters used will vary from helicopter to helicopter. Note that many radios produced have both airplane and helicopter programming in a single radio.

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 mt be glued properly and securely to prevent the airplane from crashing.

Hit (or to be hit)
Sudden radio interference which caes your model to fly in an erratic manner. Most often caused by someone turning on a radio that is on your frequency, but can be caused by other radio sources miles away.

Horizontal Stabilizer
The horizontal tail surface at the back of the fuselage which provides aerodynamic pitch stability to the airplane.

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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Ldle Up
This is a setting on the transmitter which limits the throttle minimum. Particularly useful for FFF and 3D stunt flying.

Lmmelmann
A maneuver originally used to reverse direction in combat. The airplane noses up and over onto its back. It then rolls upright and continues in the direction opposite to the original direction. It was invented by the World War I German pilot Max Immelmann, whose airplane could perform the maneuver, and others couldn't. It got him out of a lot of trouble in combat until the Allied aircraft designs caught-up and allowed their planes to perform the maneuver, too.

Lntake
An air inlet on an aircraft. You can have a carburetor intake, cooling intake, air conditioning intake (on full-size aircraft), and so on. Named becae it "takes in" air, and becae "intake" is a better-sounding word than "takes in".

Lnverted
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.

Lnverted Flight Control
Activates inverted flight programming for helis, which reverses the direction of the rudder, pitch and elevator servos, and sets up inverted flight pitch high-side and low-side. Inverted programming is used to allow the radio inputs to be identical to upright flight while the model is inverted. Note: this approach to hovering is seldom ed. Instead, idle-ups are used and the modeler learns to understand and respond to the controls' reversal in inverted flight.

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 assemblies that include the wheels and the wheel struts. The word "gear" is used in the sense of "equipment", as opposed to the "toothed wheel" meaning of "gear". The British call the landing gear the "undercarriage".

Lateral Balance
The left-right or side-to-side balance of an airplane. An airplane that is laterally balanced will track better through loops and other maneuvers.

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

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.

Loop
A vertical circle in the air. The plane noses up, keeps rotating until it's on its back, and then comes down and around to describe a vertical circle in the air.

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MHz = Megahertz
The unit of radio frequency. 75 MHz are surface frequencies; 72 MHz are air frequencies; 27 MHz and 50 MHz can be used for either ground or air applications. Note: use of the 50 MHz (ham radio) band requires an FCC license.

MPH
Speed in Miles Per Hour. Like RPM, MPH is both singular and plural.

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 Gear
Also Main Landing Gear. The large, heavy-duty landing gear struts and wheels that support most of the weight of the airplane. They are Usually under the wing or under the fuselage near the center of the aircraft. Any other landing gear struts and wheels are noticeably smaller.

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

Metal gears
Drive gears within a servo which are made of one or multiple metal types. Metal gears tend to wear more rapidly than nylon gears when in the same installation, and so require more frequent service to maintain optimum accuracy; however, metal gears are more durable in the case of severe vibration, flutter, or physical shock.

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

Mixing
Allows a single input to control the operation of two or more servos. Simplifies routine flying and allows more involved maneuvers-great for intermediate-advanced fliers. For example, Flap-to-elevator mixing: Most models will change pitch upon deploying flaps (some will climb; others dive). After test flying the model and determining the direction and amount of elevator throw required to correct for this change, a pilot may set a flap-to-elevator mix to compensate. Once the mix is operating properly, when the modeler gives flap control, the radio automatically also gives the proportional amount of elevator throw, keeping the model flat and straight.

Mixing Arm
A specialized lever which has three or more pivots. The length between pivots will determine the proportion of the mix between two or more linkages.

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.

Module
A removable/replacable plug in unit used in most complex computer radios, containing all frequency control equipment, including the crystal and all tuned components. Changing channels or bands on a modular radio requires only changing module. Changing crystals WITHIN a module to change the channel of the module itself is against FCC regulation and is not recommended. To use your transmitter on a different channel you simply purchase another module on that other channel and the radio is now fully properly tuned and safe and easy to use on that other channel as well.
Futaba module models include TP, TK, TJ, TL, and TK-FSS. For information on which module to e, see 9Z/8U modules, TF modules and aftermarket modules.

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 exhat stack, which can improve the airplane's performance at low speeds. Mufflers are Usually required by R/C Clubs.

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Span, also "Wingspan"
The widest straight-line distance between the two wingtips.

Speed Brakes
Large panels that fold out of the aircraft structure to provide a lot of extra drag to the air. They are not part of the wing structure, but are Usually mounted on the fuselage. Military jets most often have speed brakes, which fold out of the fuselage. Some airliners use spoilers as speed brakes when at altitude.

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.

Speed Flap
The middle control surface on a 6-trailing-edge-surface glider or the inboard control surface on a 4-surface glider.

Spin
A maneuver where at least one wing is stalled and the two wings are operating at very different angles of attack. This caes the airplane to rotate around its middle while it descends at a high rate of speed. When it's done on purpose, it is a precision maneuver, with the pilot trying to get the airplane to rotate an exact number of turns from entry to exit. When it's done accidentally, it can easily result in a crash. Many models crash when the pilot enters an accidental spin too close to the ground. This is caused by improper speed control during the landing approach.

Spinner
The bullet-shaped fairing on the nose of the airplane around the propeller. This smooths the airflow around the propeller hub and also makes the airplane looks much better.

Split-S
Basically a reverse Immelmann. The airplane rolls onto its back, and then the nose comes down to finish a 1/2-loop. The direction of flight is changed 180o.

Spoiler(s)
Control surfaces on the wing that destroy lift. They "spoil" it. They are used on sailplanes because they can steepen the very flat glide of the aircraft, which makes landings much easier. On full-size aircraft, spoilers are also used to kill lift on landing to make sure the airplane is firmly on the ground. They also add a lot of drag to help with aerodynamic braking.

Stabilator
Stabilizer+elevator, also called full-flying tail. Stabilizer incidence controlled by pilot in lieu of an elevator.

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

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).

Strut
Basically this is a supporting member. A wing strut supports the wing, and goes from the fuselage to the wing. Cabane struts are on biplanes, and support the upper wing over the fuselage. A landing gear strut is the portion that holds the wheel assembly to the airplane, and away from the wing or fuselage.

Sub-Trim
This is a trim function on many computer radios, allowing trim function during set-up, and still allowing the full trim function in flight.

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
An optical sensor designed specifically to count light impulses through a turning propeller and read out the engine RPM.

Taildragger
The nickname of an airplane that sits on its tail with the two main wheels in front and a tailwheel in the rear.

Taileron
Stabilator with collective and differential actuation.

Tailskid
On old World War I type aircraft, or pioneer-type aircraft, there was no tailwheel. A wooden skid was used to support the tail of the airplane. While this helps slow the airplane during landing, it is eless as an aid to steering on the ground. The real aircraft with tailskids had to be maneuvered on the ground by ground crews, who put the tail on a small cart and towed the airplane where they wanted it. For small distances, the tail was picked-up by hand and the airplane phed into position by the ground crew.

Tailwheel
The small wheel at the tail of the airplane. This is found on the type of airplane that have the two large wheels in the front, and the small one in the rear. The airplane sits on its tail.

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
The control that allows the pilot to change the speed of the engine. In a car, the "gas pedal" is actUsually the throttle control for the car.

Throttle Curve
The programming function of the radio which allows throttle operation to be adjusted to meet the modeler's specific needs at vario points along the throttle movement. Particularly useful with 2-stroke engines in providing linear throttle response at the vario points of throttle application.
For helis: Aids in setting the hover point, and end points of the throttle in the collective mix.

Throttle Hold
A radio function which locks the throttle at a fixed point while a switch is activated. This function is used to hold the throttle in an idle. useful when starting, as well as for auto rotations.

Throttle Stop Screw
Screw for setting the lower limit of the throttle movement

thrust
The forward force provided by the airplane's engine. This is the force that drives the airplane forward.

Torque
The force which tends to CAUSE rotation.

Torque Rods
Inserted into ailerons, these rigid wire rods run along the wings' trailing edge, then bend downward and connect to the phrods.

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.

Trailing Edge (TE)
The rearmost edge of the wing or stabilizer.

Trainer Airplane
A model designed to be inherently stable and fly at low speeds, to give first-time modelers time to think and react as they learn to fly.

Trainer System
Allows trainer to link radios with a student via a cord, and to instantly take control of student's craft in-flight. The 8U system has special training features available.

Transmitter (Tx)
The hand-held radio controller. This is the unit that sends out the commands that you input.

Tricycle Gear
The landing gear arrangement where the airplane has main gear and a nose gear.

Trim Lever
Slides used to adJust control surfaces during flight.

Tx
Abbreviation for transmitter.

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Undercamber
This means that the lower surface of the wing has a hollow curve when observed from front to back. A thin wing with a high camber will be undercambered.

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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 es two linear responses to determine the servo sensitivity on the first and second half of the control stick movements.

Ventral Fin
A small vertical surface on the bottom of the aft fuselage. Usually a long, slim triangle that is narrow at the front, and widens toward the rear. It Usually ends at the rudder hinge line.

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

Vertical Fin
The non-moving surface that is perpendicular to the horizontal stabilizer and provides yaw stability. This is the surface to which the rudder attaches.

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Washout
An intentional twist in the wing, caing 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, and helps the "PT" family of trainers recover, hands-off, from unwanted spiral dives.

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

Wheel Pants
The large fairings used to streamline the wheels of an aircraft that has non-retracting or "fixed" landing gear (so-called because it's "fixed" in place).

Wing
Because wings provide the primary lift force on an airplane, adjtments 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 exhat gases from entering the structure.

Wing Span
The maximum distance from wingtip to wingtip.

Wing Tip
The very outer end of a wing.

Winglet
A small vertical surface at the tips of the wings. They help direct the turbulent airflow that all wings have at the tips. They make the wings more efficient.

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Yaw
The nose-left and nose-right movement of the airplane. This is controlled by the rudder.

Yaw Axis
The airplane axis controlled by the rudder. Yaw is illtrated by hanging the airplane level by a wire located at the center of gravity. Left or right movement of the nose is the Yaw movement.

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

Z-Bend Pliers
used for crimping wire ends into Z bends.