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
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.
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,
For helis: combining two or more maneuvers into one maneuver. Examples:
rolling circle, inverted backwards loop.
Slang abbreviation for flip flop flying. Similar to 3D, but without the
A return to top
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
Adjustable Function Rate (AFR)
Similar to ATV, AFR allows end point adjustment independent of Dual Rate or
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 yaw.
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
The shape of the wing when looking at its profile. Usually a raindrop type
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
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.
The line around which a body rotates.
B return to top
BEC = Battery Eliminator Circuitry
Allows receiver to draw power from a main battery pack, eliminating the need
for (and weight of) a receiver battery.
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
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
Base Load Antenna
A rigid, short antenna mounted to the model. Used to replace the longer
To fully charge and discharge a battery to erase battery memory.
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.
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
"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.
C return to top
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
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
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
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
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 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 wing.
Device used to recharge batteries and usually supplied with the radio if
NiCad batteries are included.
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
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 of fuel.
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
The landing gear arrangement where the airplane has a main gear and a
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 weakest.
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.
D return to top
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 dead stick".
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
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
E return to top
This is the small motor commonly used to start the airplane's engine.
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 dive.
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
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.
F return to top
Frequency Modulation. This describes the mode of transmission of radio
signal from transmitter to receiver.
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 wheels.
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 flaps.
Hinged control surface located at the trailing edge of the wing inboard of
the ailerons. The flaps are lowered to produce more aerodynamic lift from
the wing, allowing a slower takeoff and landing speed. Flaps are often found
on scale models, but usually not on basic trainers.
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 engine throttle.
A special box used to hold and transport all equipment used at the flying
Flight Pack or Airborne Pack
All of the radio equipment installed in the airplane, i.e., Receiver,
Servos, Battery, Switch harness.
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
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
Material that is used to dampen the airplane's vibrations and protect the
airplane's battery and receiver.
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 movement...."
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
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.
G return to top
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
Gimbal (or Stick)
The device that allows the user to input desired control movements into the
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
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 bounce.
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
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.
H return to top
The device for carrying the transmitter
A device consisting of wires, switches, and a fuse that connects a motor to
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 single radio.
This term describes an airplane that has its wings mounted on the top of the
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
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
I return to top
J return to top
K return to top
L return to top
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
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"
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 piston.
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
M return to top
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
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 Clubs.
N return to top
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
Rechargeable 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
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.
O return to top
Galvanic separation, blocks interference from the motor current circuit,
prevents it reaching the receiver.
P return to top
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 landing.
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
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 points.
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 modelers.
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
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.
Q return to top
R return to top
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
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
The function of the radio which mixes throttle to rudder, preventing the
rotation of the helicopter during throttle increase or decrease.
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
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 right.
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.
S return to top
SMT = Surface Mount Technology
Ultralight, solid-state components which offer greater vibration resistance
An airplane that has floats, or pontoons, attached to allow it to land on
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 airplane.
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 installation.
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
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 results.
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 changed
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 this angle).
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.
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 propeller.
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.
T return to top
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
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
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 mix.
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 forward.
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 stabilizer.
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.
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
Slides used to adjust control surfaces during flight.
Abbreviation for transmitter.
U return to top
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
V return to top
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
The non-moving surface that is perpendicular to the horizontal stabilizer
and provides yaw stability. This is the surface to which the rudder
W return to top
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
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 plans.
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 structure.
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
X return to top
Y return to top
The nose-left and nose-right movement of the airplane. This is controlled by
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.
Z return to top
The wire ends of pushrods have Z-shaped bends, which attach to the servo.
Used for crimping wire ends into Z bends.