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
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
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
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.
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 adjustment independent of Dual Rate or Exponential settings.
Adjustable Travel Volume (ATV)
End Point Adjustment, ATV you
can independently preset the maximum travel of a servo on either side of neutral.
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. Adjusting the ailerons can help reduce the
Science of air in motion.
Towards the rear. Used such as: "...with an aft center of gravity...."
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.
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).
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
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.
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 adjusting the amount of air
allowed to bleed into the carburetor during idle
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, 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.
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 thousand model competitions throughout the country each year, and certifies official model flying
records on a national and international level.
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).
The telescoping tube that transmits the signal.
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.
Almost Ready to Fly, a model airplane that can be put together with a minimal amount of time.
This is borrowed from full sized helicopters, and is a rotor head which allows the blades to flap,
drag and feather.
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.
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
The line around which a body rotates.
BEC = Battery Eliminator Circuitry
Allows receiver to draw power from a main battery pack, eliminating the need for (and weight of) a
Cover over the rear of the crankcase of an engine.
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.
Servo's output shaft is supported with bearings
for increased performance and accuracy.
Connection using a ball, and a link which rotates
on the ball. Used to connect the servo to a control surface or lever.
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.
To fully charge and discharge a battery to
erase battery memory.
The device used to monitor the strength of the
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
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
Also known as crow. A mix which activates up flaperons and down inner-most flaps for gliding speed
control without spoilers or airbrakes.
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.
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 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.
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".
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.
The maximum amount of energy a battery can store.
The part of the engine which controls the speed or throttle setting and lean/rich mixture via
setting of the needle valve.
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.
A very steep climbing turn where the airplane makes a 180o change of direction.
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
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.
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
Device used to recharge batteries and usually supplied with the radio if NiCad batteries are
A hand-held stick used to start a model airplane engine.
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.
The clevis connects the wire end of the pushrod 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 pushrod.
Located in the fuel tank, a clunk is weighted and ensures that the intake line has a steady supply
This is the ability to vary the main blade pitch when the throttle is increased or decreased.
By using the advanced programming functions
of the transmitter, you can adjust the airplane without changing any mechanical structures.
Constant Drive Tail
This is a special autorotation clutch
that will always drive the tail rotor even when the engine is off or in "Hold".
This arm connects the control surface to the
clevis and pushrod.
Any one of the various moveable portions of
the wings, tail surfaces, or canard.
The landing gear arrangement where the airplane has a main gear and a tailwheel.
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
The covering of an aircraft is the skin which is applied to the airframe, closing it in. 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.
The large molded 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.
Main body of the engine
Critical Angle of Attack
The angle of attack at which smooth airflow over the top of the wing stops.
Primarily used in gliders for spoiler action by
mixing the flaps and ailerons. It is necessary for the ailerons to be using separate servos,
plugged into separate channels and the flap servo to be independent of both aileron channels. Upon
applying Crow Mixing, the flaps go down while both ailerons go up.
Crucifix refers to 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 advantages of both.
The device that sets the radio frequency of the transmission
The section of the crankcase where combustion takes place
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.
Slang term for a landing without engine power. An example: "I ran out of fuel at 50 feet and had to
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.
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.
This type of mixing is accomplished by having separate servos on each aileron, plugging one into
the aileron channel and the other into another unused channel. The two channels can be programmed
to both operate from the aileron control stick, however the travel volume for each aileron may be
adjusted separately giving more deflection in one direction (usually up) than in the other.
The degree of angle (V-shaped bend) at which the wings intersect the plane is called dihedral. More
dihedral gives an airplane more aerodynamic stability. trainer planes with large dihedral dispense
with ailerons and use only the rudder to control the roll and yaw.
An electronic component which only allows current to flow one direction. Protects the transmitter
against reverse polarity or power surges during charging.
Direction of Flight
The relative direction of the wing in relation to still air
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.
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 Aileron Extension or Y-Harness
The Y-Harness is a cable which plugs into a single channel in a receiver and two servos. This
allows both servos to be operated from the same channel.
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 (D/R)
Dual Rate allows the modeller to choose
between two different control sensitivities. With the dual rate switch in the "OFF" position, 100%
servo throw is available for maximum control response. In some more sophisticated systems this
"OFF" position may be adjusted to provide anywhere from 30% to 120% of normal full throw. In the
"ON" position, servo throw is reduced and the control response is effectively desensitized. The
amount of throw in the Dual Rate "ON" position is usually adjustable from 30% to 100% of total
servo movement. The modeller can tailor the sensitivity of his model to his own preferences.
This is the small motor commonly used to start the airplane's
A caustic material found in batteries.
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
Mixes the Elevator and Aileron functions, especially useful for delta-wing models where the
elevator and ailerons are the same control surfaces. Each surface is connected to a separate servo
(one servo plugged into the aileron channel and the other plugged into the elevator channel), the
surfaces will act as both ailerons and elevator, depending on the position of the controls.
Used to apply flaps along with elevators to increase lift, allowing modeler to fly at slower
speeds, make tighter loops or turns, etc.
The vertical and horizontal tail surfaces of an airplane.
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 is where the servo
movement is not directly proportional to the amount of control stick movement. Over the first half
of the stick travel, the servo moves less than the stick. this makes control response milder and
smooths out level flight and normal flight maneuvers. Over the extreme half of the stick travel,
the servo gradually catches up with the stick throw, achieving 100% servo travel at full stick
throw for aerobatics or trouble situations.
Frequency Modulation. This describes the mode of transmission of radio signal from transmitter to
Fail Safe (FS)
A safety feature which turns a servo to a
preset position if the signal is lost or interrupted. 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.
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
A fast battery charger designed to work from a 12-volt power source, such as a car battery.
Can be an "official" competition maneuver, 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.
Mixes the Flap and Aileron functions so
that when each aileron is connected to a separate servo (one servo plugged into the aileron channel
and the other plugged into the flap channel), the surfaces will act as both ailerons and flaps,
depending on the position of the controls.
The movement of two aileron servos, both in the same direction at the same time, acting as
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.
The point during the landing approach in which the pilot gives an increased amount of up elevator
to smooth the touchdown of the airplane.
A Flat Bottom Wing is when the lower surface of the wing is primarily flat between the leading and
trailing edges. This type of wing has high lift and is common on trainer type aircraft.
A flex cable is a special type of pushrod which
is very flexible and can bend around corners even more easily than a flexible pushrod. These are
generally made with a metal cable running inside a plastic tube and are popular in controlling the
A special box used to hold and transport all equipment used at the flying field.
Flight Pack or Airborne Pack
All of the radio equipment installed in the airplane, i.e., Receiver, Servos, Battery, Switch
Long, canoe-shaped structures that allow an airplane to land on water. They are not a part of the
aircraft structure, but suspended below the fuselage on struts. Also called "Pontoons".
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.
A flying stab is where the stabilizer/elevator is one complete unit which all moves to control the
aircraft in pitch.
Decrease in angle held by a servo which is being commanded by an AVCS gyro when the input is
released. For example, a rudder servo might be at full deflection when rudder input is held. When
the rudder stick is released but the model has not yet turned as far as the AVCS gyro has read your
input to tell it to move, the servo will continue to hold input. However, it may "flyback" or
decrease the angle at which it is holding slightly. This is perfectly normal.
The type of aircraft where the fuselage has the lower portion shaped like a power boat. The plane
lands on water directly onto the fuselage. There may be small floats suspended from the wings to
keep the plane level when it's in the water.
FM, or Frequency Modulation, is now the common method and is less prone to interference than AM.
Information is transmitted by varying the frequency of the signal.
Material that is used to dampen the airplane's vibrations and protect the airplane's battery and
Four Way Wrench
Combination wrench with sizes to fit glow plug, prop nut, etc.
Towards the front. Used such as "...the forward edge of the rib...", or as in "...with fore and aft
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.
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.)
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.
The body of an airplane.
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 user to input
desired control movements into the transmitter
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.
Momentary radio problem that never happens unless you are over trees or a swamp.
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.
A very smooth, gentle landing without a hint of a
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
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.
The device for carrying the transmitter
A device consisting of wires, switches, and a fuse that connects a motor to a battery.
The component which forms the end of the compression chamber of the engine
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.
Slang term for Heading Hold Gyro.
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.
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 sustain a controlled hover. The specific
radio requirements will vary from user to user, and the parameters used will vary from helicopter
to helicopter. Note that many radios produced have both airplane and helicopter programming in a
This term describes an airplane that has its wings
mounted on the top of the fuselage.
The hinges are the moving blades on the control surface that allow you to control the airplane's
movement. All hinges must be glued properly and securely to prevent the airplane from crashing.
Hit (or to be hit)
Sudden radio interference which causes
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.
The horizontal tail surface at the back of the fuselage which provides aerodynamic pitch stability
to the airplane.
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.
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
This is a setting on the transmitter which limits
the throttle minimum. Particularly useful for FFF and 3D stunt flying.
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.
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 because it "takes in" air, and because "intake" is
a better-sounding word than "takes in".
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 used. Instead, idle-ups are used and the modeler learns to understand and
respond to the controls' reversal in inverted flight.
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.
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".
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.
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
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.
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.
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.
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.
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.
The speed at which a sailplane loses altitude
most slowly. Usually expressed in feet per minute.
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.
A specialized lever which has three or more
pivots. The length between pivots will determine the proportion of the mix between two or more
The control stick configuration with the rudder and
elevator being controlled by the left stick while the right stick controls the throttle and
The control stick configuration with the ailerons
and elevator being controlled by the right stick while the left stick controls the rudder and
The control stick configuration with the rudder and
elevator being controlled by the right stick while the left stick controls the ailerons and
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 use,
see 9Z/8U modules, TF modules and aftermarket modules.
The section of the crankcase used to mount the
engine to the airplane
This device muffles engine noise and increases the back pressure from the engine's exhaust stack,
which can improve the airplane's performance at low speeds. Mufflers are usually required by R/C
A radio with a 20 KHz band width. All Futaba radios produced 1992
or later and all Futaba FM and PCM radios ever produced are narrow band. Specific list of Futaba
narrow band transmitters.
This mechanism within the carburetor adjusts
the fuel mixture and throttle. Refer to your engine's manufacturer instructions for directions on
how to adjust the needle valve.
NiCad (or NiCd) = Nickel Cadmium battery
batteries which are typically used as power for radio transmitters and receivers.
Nitro = Nitromethane
A fuel additive which increases a model engine's ability to idle low and improves high speed
performance. Ideal nitro content varies from engine to engine. Refer to the engine manufacturer's
instructions for best results. Nitro content in fuel is indicated by the percent of the fuel.
A Noise Trap is a small electronic device which
is wired into a long servo extension to reduce radio interference and to boost the control signal
going to the servo. These are recommended for use where long servo leads are necessary.
National Organization for Racing Radio Controlled Autos.
The part of the landing gear that is attached to
the nose of the fuselage. The nose gear is usually connected to the rudder servo to help you steer
the airplane on the ground.
Drive gears within a servo are made of nylon.
Nylon gears show slower wear than metal gears, but are more prone to failure due to severe
vibration, flutter, or physical shock to the servo.
Galvanic separation, blocks interference from the motor current circuit, prevents it reaching the
PA2 = Pilot Assist
Optional onboard device which uses
optical sensors to correct model's orientation to upright.
PCM = Pulse Code Modulation
PCM systems use digitally
encoded signals to minimize interference and provide today's most advanced R/C control.
Low-voltage protection, gives safely margin when using BEC in model aircraft. PCO cuts off the
motor (the main power consumer) in good time, to reserve sufficient battery capacity for a safe
This is the point at which a battery will no longer accept a charge, and converts the energy to
heat. This is damaging to the battery pack, and potentially hazardous.
This type of charger will eliminate the
guesswork. When the battery has reached peak, the charger reverts to a maintenance charge rate,
which will not damage the pack.
Usually refers to a type of battery charger
that automatically shuts off when a battery is fully charged.
To make progress against the wind.
Degree of nose up or nose down from level to the horizon.
The airplane axis controlled by the elevator.
Pitch is illustrated by holding the airplane at each wingtip. Raising or lowering the nose is the
pitch movement. This is how the climb or dive is controlled.
The programming function of the radio which aids in setting the hover point, and end points of the
blade pitch in the collective mix.
Offsets the entire heli pitch curve, increasing or decreasing responsiveness proportionally at all
Polyhedral refers to the multiple angle wing panels make with the horizontal. A wing with
polyhedral has more than two wing panels and the angle of the wing changes at each joint.
POR - Power On Reset
Safety circuit; controller does not start working until the throttle stick is set to "off".
Prevents the motor bursting into life unexpectedly; an important safety aspect for all
12-volt distribution panel that provides correct voltage for accessories like glow-plug clips, fuel
pumps and electric starters. Usually mounted on a field box and connected to a 12-volt battery.
The main crankshaft which transfers the power of
the engine to the propeller
Pulse Position Modulation. Another term for FM.
A linkage set up using two rods or wires. One is
pulled for one direction, the other is pulled for the other.
A linkage set up using two rods. One rod pushes, while the other pulls.
The rigid mechanism that transfers movement from the servo to the control surface.
The pushrod connector is another means by
which a pushrod may be connected to a servo. The connector is mounted onto a servo arm and the
pushrod wire is secured by means of a set screw.
How fast something turns. It means Revolutions Per Minute. It is both singular and plural.
The radio unit in the airplane which receives
the transmitter signal and relays the control to the servos. This is somewhat similar to the radio
you may have in your family automobile, except the radio in the airplane perceives commands from
the transmitter, while the radio in your car perceives music from the radio station.
Direction that the air molecules strike the
lead-ing edge of the wing.
If a wing has an airfoil that curves down from the high point, and then curves back up, it's said
to be "reflexed". Reflex is the size of that reverse curve.
This is the increased vibration (or amplitude of oscillation) of system when acted upon by a force
whose frequency is close to or equal to the normal frequency of the system. When the resonance of
many parts of a machine are in synch, the whole machine will vibrate at a greater rate and can be
damaged. Resonance can cause difficulties in an aircraft, particularly when using a vibration mount
with an improperly balanced propeller/spinner.
For helis: Keep in mind that a helicopter has many rotating parts, and they all cause resonance.
The helicopter will need to be tuned to reduce the amount of vibration.
Specifically used for mechanical retracts. It
is a non-proportional servo which only moves 180 degrees. That is to say this servo is either "off"
(gear up and fully locked) or "on" (gear down and fully locked). No ATV, EPA, or AST adjustments
can be made on these servos because they are not proportional. The linkage must be set up properly
to allow this servo to operate at its full range and do its job-securing your model's landing gear
in a gear-up or gear-down position.
Short for retractable landing gear. Wheels and struts that fold up into the airplane to get them
out of the airstream and present less resistance to the airflow.
The function of the radio which mixes
throttle to rudder, preventing the rotation of the helicopter during throttle increase or
Radio Operated Auto Racing. National body to standardize and sanction R/C car and truck racing.
The airplane keeps the nose pointed in one
direction while it rolls over on its back and then upright again.
The airplane axis controlled by the ailerons. Roll
is illustrated by holding the airplane by the nose and tail. Dropping either wingtip is the roll
movement. This is used to bank or turn the airplane. 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.
Hinged control surface located at the trailing edge of the vertical stabilizer, which provides
control of the airplane about the Yaw axis and causes the airplane to Yaw left or right. Left
rudder movement causes the airplane to Yaw left, and right rudder movement causes it to Yaw
In radios with idle up functions, this specifies the amount of tail rotor pitch in the different
idle up conditions.
Mix used to counteract undesirable roll
which often happens with rudder input, especially in knife edge, also called roll coupling.
This heli mix adds a small amount of throttle to counter the added load on the main gear from
increasing the pitch of the tail blades, helping to maintain a constant headspeed during rudder
application. (This is a minor effect and is not a critical mix for most helicopters.)
Ruddervators are on a v-tail. Both of the ruddervators move up and down for pitch control and both
move left or right for yaw control.
Abbreviation for receiver.
SMT = Surface Mount Technology
Ultralight, solid-state components which offer greater vibration resistance and reliability.
An airplane that has floats, or pontoons, attached to allow it to land on water.
The electro-mechanical device which moves the control surfaces or throttle of the airplane
according to commands from the receiver. The radio device which does the physical work inside the
Servo Control Arms
Servo Control Arms are the plastic output
horns which are mounted to the output shaft on your servos. These come in various sizes and styles
for different control applications. Most servos will come with an assortment of arms so you can
customize to your own specific control needs.
Reverses the rotation of a servo with the flip of a switch. Adds ease and flexilibility during
Servo Output Arm
The removable arm or wheel which bolts to
the output shaft of a servo and connects to the pushrod.
Used to reverse the direction of a servo to
ease installation and set up.
A "hit" that results in a crash landing. Sometimes
caused by radios miles away.
Moveable surfaces on the leading edge of the wing that helps airflow in low-speed flight. They
enable the wing to fly at lower airspeeds than without them by directing the airflow over the wing
and preventing separation of the airflow. Basically, they are retractable slots. All modern
jetliners have slats, which open when landing flaps are lowered. Some aircraft intended for very
short takeoff and landing have slats that open and close automatically, depending upon airspeed and
angle of attack.
A maneuver where the airplane's controls are used to make the fuselage fly at an angle to the line
of flight. This causes a tremendous increase in drag, and allows an airplane without landing flaps
to increase its angle of descent without picking up a lot of speed.
This is another special unit that is attached to the autorotation clutch will let the main blades
turn the tail rotor when the engine is off or in "Hold". The difference between this and a
"Constant Drive Clutch" is that this one will "Slip" a little so the tail rotor while spinning will
not load the main rotors as much while in the "Hold" funtion doing a "Autorotation".
Unwanted, excessive free movement in a control system. Often caused by a hole in a servo arm or
control horn that is too big for the pushrod wire or clevis pin. This condition allows the control
surface to move without transmitter stick movement. Also, see flutter.
A specially-shaped slot in the wing just behind the leading edge. This directs airflow from below
to the top of the wing, and helps low-speed flight by delaying the stall. Because they are
permanently-mounted, they do add drag. See also "Slats"
A very slow version of the roll.
A type of rolling maneuver that is very quick and
violent. It's basically a spin where the flight path is in any direction chosen by the pilot.
Improper speed control during a landing approach can also make the model snap over on one wing and
enter a spin. Since it's close to the ground, there's not enough room to recover, and a crash
Snap Roll Button
This feature is found on more complex
radios and is used to perform a snap roll maneuver by simply pressing one button. The function is
usually programmable to give a combination of rudder, elevator and aileron control.
Snap Roll Switch
Combines rudder, elevator and aileron
movement to cause the aircraft to snap or spin on the flip of a switch.
Your first totally unassisted flight that results in a controlled landing.
Span, also "Wingspan"
The widest straight-line distance between the two wingtips.
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.
An electronic device that functions as a
throttle for an electric motor. A speed control controls the speed or rpm of an electric motor.
The middle control surface on a
6-trailing-edge-surface glider or the inboard control surface on a 4-surface glider.
A maneuver where at least one wing is stalled and the two wings are operating at very different
angles of attack. This causes 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.
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.
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
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.
Stabilizer+elevator, also called full-flying tail. Stabilizer incidence controlled by pilot in lieu
of an elevator.
The Stabilizer is the fixed horizontal surface at the rear of an aircraft. It provides pitch
stability for the aircraft.
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
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
This is a trim function on many computer radios,
allowing trim function during set-up, and still allowing the full trim function in flight.
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
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.
An optical sensor designed specifically to count light impulses through a turning propeller and
read out the engine RPM.
The nickname of an airplane that sits on its tail with the two main wheels in front and a tailwheel
in the rear.
Stabilator with collective and differential actuation.
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 useless 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 pushed
into position by the ground crew.
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.
Rising body of hot air that can take a sailplane to a great height.
A liquid that solidifies; used to prevent
screws from loosening due to vibration.
The control that allows the pilot to change the speed of the engine. In a car, the "gas pedal" is
actually the throttle control for the car.
The programming function of the radio which
allows throttle operation to be adjusted to meet the modeler's specific needs at various points
along the throttle movement. Particularly useful with 2-stroke engines in providing linear throttle
response at the various points of throttle application.
For helis: Aids in setting the hover point, and end points of the throttle in the collective
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
The forward force provided by the airplane's engine. This is the force that drives the airplane
The force which tends to cause rotation.
Inserted into ailerons, these rigid wire rods
run along the wings' trailing edge, then bend downward and connect to the pushrods.
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
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
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.
The hand-held radio controller. This is the
unit that sends out the commands that you input.
The landing gear arrangement where the
airplane has main gear and a nose gear.
Slides used to adjust control surfaces during
Abbreviation for transmitter.
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.
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.
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 uses two linear responses to determine the
servo sensitivity on the first and second half of the control stick movements.
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.
The vertical surface of the tail gives the airplane stability while in flight.
The non-moving surface that is perpendicular to
the horizontal stabilizer and provides yaw stability. This is the surface to which the rudder
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, and helps the "PT" family of trainers recover, hands-off, from
unwanted spiral dives.
The round retaining piece that anchors wheels in place on the axle.
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).
Because wings provide the primary lift force on an airplane, adjustments to the wings affect the
airplane's movements while in flight.
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
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 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 exhaust gases from entering the
The maximum distance from wingtip to wingtip.
The very outer end of a wing.
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.
The nose-left and nose-right movement of the airplane. This is controlled by the rudder.
The airplane axis controlled by the rudder. Yaw is
illustrated 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.
The wire ends of pushrods have Z-shaped bends, which
attach to the servo.
Used for crimping wire ends into Z bends.