File: D:/web/homefly/reference/glossary.htm
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<p align=center style='text-align:center'><b>Home Flyer�s Glossary<o:p></o:p></b></p>
<p><b>A</b> amp or ampere.</p>
<p><b>AC</b> 1. Alternating current. Current that cyclically reverses
polarity (flows in both directions).<br>
2. Auto Cutoff. A circuit that switches off or reduces current to the motor when
cell voltage drops to a predetermined (sometimes user-adjustable) level, in
order to prevent cell damage or the interruption Rx or servo operation. Also
called LVC (low voltage cutoff).</p>
<p><b>Acceleration</b> <i>(a)</i> The rate of change of velocity, measured in
(m/s<sup>2</sup>).</p>
<p><b>Actuator </b> A D'Arsonval, solenoid or brushed motor that moves an
output arm in response to an analog voltage signal from the receiver. </p>
<p><b>Aileron</b> One of a pair of control surfaces hinged to the TE of
a wing that generates rolling moment and commands bank angle. </p>
<p><b>Airfoil</b> The cross sectional shape of a flying surface (e.g. a
wing or stabilizer)</p>
<p><b>Airship</b> Powered LTA aircraft that is steerable (rigid [Zeppelin],
semi-rigid, non-rigid [blimp] and helistat).</p>
<p><b>ampere</b> (A) Unit of electric current (coulomb per second).</p>
<p><b>AM</b> Amplitude Modulation. Varying the amplitude a signal in
order to transmit information. </p>
<p><b>Angle of attack </b>(<i><span style='font-family:GreekC'>a</span></i>)
The angle between the chord line (or zero lift line) and the relative wind.</p>
<p><b>Angular displacement</b> The included angle through which an object
rotates, measured in radians (rad), degrees (<sup>o</sup>), or revolutions
(rev).</p>
<p><b>Angular speed</b> (<i><span style='font-family:GreekC'>w</span></i>) The
rate at which an object (e.g. a propeller) rotates, measured in rad/s, rev/s or
rev/min. Also called <i>rotational velocity</i>.</p>
<p><b>AOA</b> Angle of Attack. </p>
<p><b>ARF</b> Almost Ready to Fly (type of kit)</p>
<p><b>Aspect ratio</b> Wingspan squared divided by wing area (<i>AR</i>
= <i>b</i><sup>2</sup>/<i>S</i>)</p>
<p><b>Autonomous</b> Describes a self-contained, self-correcting,
independent computerized control and guidance system that performs tasks by
acquiring, processing and acting in response to environmental information. </p>
<p><b>AUW</b> All up weight. Gross takeoff weight.</p>
<p><b><i>B</i></b> Magnetic flux density, measured in teslas. (Always
capitalized.)</p>
<p><b>Back voltage</b> <i>(E)</i> A reactive voltage that opposes source
voltage. Also called <i>back emf </i>or<i> counter emf</i>.</p>
<p><b>Back voltage constant</b> <i>(K<sub>E</sub>)</i> The back voltage
generated by an electric motor divided by speed. <i>K<sub>E</sub>=E/</i><i><span
style='font-family:GreekC'>w=</span>(V-IR<sub>a</sub>)/</i><i><span
style='font-family:GreekC'>w</span></i>. Expressed in volt-seconds per radian,
(V-s/rad), volt-seconds (V-s) or webers (Wb). Also called<i> voltage</i> or <i>generator</i>
constant. </p>
<p><b>Bandwidth</b> The range of frequencies available for signaling.</p>
<p><b>Bank </b>1. <i>(v.tr.)</i> To roll.<br>
2. <i>(n.)</i> Lateral tilt of the wings with respect to horizontal, measured
in degrees.</p>
<p><b>Battery </b> Two or more cells electrically connected in series or
parallel.</p>
<p><b>BEC </b>Battery Eliminator Circuit. A voltage regulator usually built
into the ESC, through which a higher voltage battery can supply power to the
servos and Rx. </p>
<p><b>Beta</b> <i>(</i><i><span style='font-family:GreekC'>b</span>)</i>
Propeller blade incidence, the local angle of the blade at a given distance
along the radius, expressed in degrees (usually measured at the 3/4-radius
station when calculating the pitch for non-helical propellers).</p>
<p><b>Black wire corrosion</b> A process by which chlorine and fluorine
outgases from PVC insulation chemically combine with copper.</p>
<p><b>BL</b> Brushless. </p>
<p><b>Blimp</b> A non-rigid airship</p>
<p><b>Boundary layer</b> The region of fluid flow around a body that moves at
less than free stream velocity. The boundary layer can be laminar or turbulent.</p>
<p><b>Brick</b> A receiver, two servos and an ESC combined on a single circuit board
with connectors for the battery and motor or optional outboard ESC or servos. <b><o:p></o:p></b></p>
<p><b>Brushless </b> A type of DC motor that does not have a
mechanical commutator. AC is fed to the stator armature by an inverter. The
rotor contains permanent magnets. Uses a special controller. <b><o:p></o:p></b></p>
<p><b>Buddy box </b>A set of dual controls that overrides an instructor's Tx
via cable connection.</p>
<p><b><i>C</i></b> (italicized) 1. The current a cell or battery can
supply for one hour. <br>
2. The symbol for capacitance.</p>
<p><b>C</b> (not italicized) coulomb (Always capitalized.)</p>
<p><b><i>c</i></b> The speed of light (approx. 300Mm/s).</p>
<p><b>CA</b> Cyanoacrylate. An instant adhesive.</p>
<p><b>Cabane</b> ( <i>kuh bane'</i>)<i> </i>Describes the short
struts that connect a parasol or biplane wing to the fuselage. </p>
<p><b>Camber</b> The ratio of chord height of the mean camber line to chord
length.</p>
<p><b>candela</b> (cd) Unit of luminous intensity (brightness) </p>
<p><b>Capacitance</b> <i>(C)</i> 1. In general, the charge storage capacity of
two separated conductors, particularly the charge divided by applied voltage,
measured in farads (F). <i>C=Q/V</i>.<br>
2. The displacement current a capacitor carries divided by rate of change of
voltage. <i>C=I/(dV/dt),</i> where <i>dV/dt</i> is the rate of voltage change.</p>
<p><b>Capacity</b> <i>(Q)</i> The amount of charge a cell can energize,
measured in milliamp-hours (mAh) or coulombs (C). <i>Q=It.<o:p></o:p></i></p>
<p><b>Capacitor</b> A passive device (e.g. two non-contacting conducting
plates) that transforms electrical energy into potential energy stored in an
electric field, and vice versa. Also called a <i>cap</i>.</p>
<p><b>CB </b> Center of Buoyancy. For a balloon or airship, the
point through which resultant force of the lifting gas is considered to act. </p>
<p><b>cd</b> candela (Always lower case.)</p>
<p><b>Cell </b>Voltaic cell. Metal electrodes of unequal
electronegativity immersed in an acid or alkaline electrolyte that convert
chemical energy to electrical energy. Often called (incorrectly) a <i>battery</i>.</p>
<p><b>CF</b> Carbon Fiber. Polyfilament composite structural
material embedded in adhesive matrix. <b><o:p></o:p></b></p>
<p><b>CG </b> Center of Gravity. The point through which inertia or
the resultant force of gravity is considered to act on a body.<span
style='font-size:10.0pt'> <o:p></o:p></span></p>
<p><b>Channel</b> 1. The band of frequencies used by a particular Tx
or Rx. Transmitters operating in proximity must be on different channels to
prevent interference. <br>
2. A discrete control output, although the term <i>function</i> is preferred. A
three function (3 channel) radio might control rudder, elevator and throttle,
for example. </p>
<p><b>Charge</b> <i>(Q) </i>1. <i>(n.)</i> Electric field flux or electricity
in general.<br>
2. A particular quantity of electricity, measured in coulombs (C) or
milliamp-hours (mAh).<br>
3. <i>(v.tr.)</i> To replenish the energy of a secondary cell via electrolysis.</p>
<p><b>Charged particle</b> An atomic body that posseses a positive or negative
electric field. Also called an <i>ion</i>. </p>
<p><b>Chord line</b> A reference line from the TE to the center of the LE
radius of an airfoil</p>
<p><b>CLA</b> Center of lateral area. The geometric centroid of a
side view (profile) shape. </p>
<p><b>CMOS</b> Complementary metal oxide semiconductor</p>
<p><b>Contest balsa</b> Balsa wood with a density of six pounds per
cubic foot (100 kg/m<sup>3</sup>) or less. </p>
<p><b>Control line</b> (C/L) Describes a mechanical system for remotely
controlling the elevator of a tethered aircraft. The pilot stands at the center
of the flight circle. Also called <i>U-Control</i>.</p>
<p><b>Conventional </b>Tail dragger landing gear configuration</p>
<p><b>Coreless</b> Describes a moving coil motor with the field
magnets inside the armature. The armature does not have a steel core. Uses a
standard high rate ESC. </p>
<p><b>coulomb</b> (C) Unit of charge equal to 6.28x10<sup>18</sup> electrons.
1C = 0.2778mAh. </p>
<p><b>Couple </b>A system of forces that creates torque without any resultant force
(pure moment).</p>
<p><b>CP</b> Center of pressure</p>
<p><b>Current </b><i>(I) </i>Charge that has been set in motion, or
particularly, charge (that moves past a point) divided by time, measured in
amps. <i>I=Q/t=V/R.<o:p></o:p></i></p>
<p><b>DC</b> Direct current. Current that flows in one direction (as
opposed to AC). </p>
<p><b>DD </b>Direct drive (prop mounted directly to motor shaft).</p>
<p><b>Decalage</b> Longitudinal dihedral. Angle between wing and
stabilizer chord lines or between biplane wings. </p>
<p><b>Defoam </b>To cut lightening holes in a molded foam RTF airframe and
cover with mylar.</p>
<p><b>Dethermalizer </b>(D/T) A movable wing, stabilizer or control surface
triggered by a fuse, Silly Putty or clockwork timer that causes a FF airplane
to descend rapidly.</p>
<p><b>DF </b> Ducted fan</p>
<p><b>Diametral pitch</b> <i>(DP)</i> See <i>pitch<o:p></o:p></i></p>
<p><b>Dihedral</b> The angle between two geometric planes. Slope of a wing from
root to tip. Influences lateral stability. </p>
<p><b>Dimension </b>Anything that is hypothetically measurable. In particular,
the magnitude of a physical quantity.</p>
<p><b>DIP </b> Dual Inline Package. The most common IC package type.
</p>
<p><b>Dirigible</b> An airship</p>
<p><b>Disk loading</b> The ratio of thrust to disk area for a propeller
or rotor, measured in pascals (Pa). Influences propulsive efficiency. </p>
<p><b>Displacement</b> The change in position, measured in metres (m).</p>
<p><b>Displacement current</b> <i>(I)</i> Current that occurs in an insulator. <i>I=C(dV/dt).<o:p></o:p></i></p>
<p><b>Dive test </b>A flight maneuver performed to determine the polarity of
static margin.</p>
<p><b>dm<sup>2</sup> </b> (lower case) Square decimetre. Unit of area
equal to 15.50 square inches or 0.1076 square feet.</p>
<p><b>DMM</b> Digital multimeter</p>
<p><b>DOF </b> Degree of freedom. One of 6 possible orthogonal motions (3
rotations and 3 translations) an object can control or perform: roll, pitch,
yaw, and translation along the x, y and z axes (surge, sway and heave).</p>
<p><b>Dorsal </b>Relating to the back or top of a body.</p>
<p><b>Dope</b> Clear or pigmented lacquer used as paint or paper adhesive.</p>
<p><b>Downlink</b> (<i>n.</i>)A means of transmitting information from a remote
device to the user, or (<i>v.tr.</i>)the act of downlinking.</p>
<p><b>DPDT </b>Double pole double throw</p>
<p><b>DPST </b>Double pole single throw </p>
<p><b>Drag </b>Aerodynamic force parallel to the relative wind (measured in
newtons or grams).</p>
<p><b>Drone</b> An autonomous and automatic freeflight UAV carrying a mechanism
to sustain stable flight on an uncorrected steady heading, and usually
programmed to function as a target. Its course is pre-programmed and cannot be
altered during flight.</p>
<p><b>Dropout </b> The minimum allowable voltage between the input
and output of a regulator. </p>
<p><b>DSM</b> Digital spectrum modulation. A proprietary implementation of
2.4GHz frequency division spread spectrum technology.</p>
<p><b>DSM2</b> DSM with two redundant data channels. <b><o:p></o:p></b></p>
<p><b>Dual rate</b> Tx feature that permits two levels of sensitivity
with respect to stick displacement.</p>
<p><b><i>E</i></b><i> </i> Back voltage (counter-emf) or energy. (Always
capitalized.)</p>
<p><b>EDF</b> Electric Ducted Fan </p>
<p><b>Efficiency</b> (<span style='font-family:GreekC'>h</span>) For a closed
system, output power divided by input power. 0<u><</u><span
style='font-family:GreekC'>h</span><u><</u>1.</p>
<p><b>Electricity</b> <i>(Q)</i> Electric charge (a property of space that
serves as the starting point for electrostatic force), a scalar quantity that
may be positive or negative, measured in coulombs (C).</p>
<p><b>Electromagnet</b> An inductor designed to supply mechanical energy.</p>
<p><b>Electromotive force</b> <i>(EMF, E or V)</i> Electrical potential or
voltage. A misnomer since emf is an energy concentration, not a force. </p>
<p><b>Electrostatic force</b> The force of interaction between charged
particles, measured in newtons. The force that causes electrons to move, and
hair to stand up in an electric field. (Not the same as electromotive force.)</p>
<p><b>Elevator </b>A control surface hinged to the TE of a horizontal
stabilizer that generates pitching moment.</p>
<p><b>Elevon</b> A control surface (elevator+aileron). One of a
pair of differential/collective ailerons located behind the CG. Used on flying
wings. </p>
<p><b>EMF</b> Electromotive force</p>
<p><b>Empty weight</b> The weight of a vehicle without payload</p>
<p><b>Endurance </b>How long something lasts, e.g. a flight, or the discharge
of current from a cell.</p>
<p><b>Energy</b> (<i>E</i>) The capacity to do work, measured in joules. <i>E=Fd=QV</i>,
where <i>d</i> is displacement parallel to the force. </p>
<p><b>Energy capacity</b> The amount of energy a cell or battery can
store, measured in joules.</p>
<p><b>Energy density </b>Energy capacity divided by volume. Measured in J/m<sup>3</sup>
or J/L.</p>
<p><b>Engine</b> A machine that converts the heat of burning fuel to mechanical
energy.</p>
<p><b>Error</b> The difference between the output and the commanded state
of a servo-controlled system. </p>
<p><b>ESC </b> Electronic Speed Control. A device that connects the
throttle function to the motor and provides proportional control over motor
speed. </p>
<p><b>ESV</b> Expanded scale (sensitive) voltmeter e.g. used to check battery
voltage.</p>
<p><b>Expo</b> Exponential throw. A feature of control linkages or
Tx programming that provides more sensitivity as control stick displacement
increases. </p>
<p><b><i><span style='font-family:GreekC'>F</span></i> </b> Magnetic flux,
measured in webers (Wb).</p>
<p><b><i>f</i></b><i> </i> Frequency</p>
<p><b>F</b> (not italicized) farad </p>
<p><b><i>F</i></b> (italicized) Force</p>
<p><b>farad</b> (F) Unit of capacitance (coulomb per volt). </p>
<p><b>Ferrite can</b> An inexpensive electric motor type featuring
ceramic ferrite field magnets, stamped steel case and carbon brushes.</p>
<p><b>FET </b> Field Effect Transistor. Controls an output current
with a small input voltage. </p>
<p><b>FF </b> Freeflight</p>
<p><b>FHSS </b>Frequency-hopping spread spectrum</p>
<p><b>Fin </b>Vertical stabilizer. (On a FF model, sometimes called a <i>rudder</i>.)</p>
<p><b>Flaperon</b> A control surface (flap+aileron). An aileron
with differential and collective actuation. Common on model sailplanes. </p>
<p><b>FM</b> Frequency Modulation. Varying the frequency of a signal in
order to transmit information. </p>
<p><b>Force</b> <i>(F)</i> A push or a pull, measured in newtons (N), the
product of mass and acceleration. <i>F=ma</i> </p>
<p><b>Freeflight</b> Describes an aircraft that is not remotely
controlled. Control surfaces are fixed or pre-programmed. (All types except R/C
and C/L.) <b><o:p></o:p></b></p>
<p><b>Frequency</b> <i>(f)</i> The number of times a cycle (usually of AC)
occurs divided by time, measured in hertz (Hz). </p>
<p><b>Full house</b> Rudder, elevator, throttle and
aileron-equipped R/C airplane. Replicates full scale control arrangement. </p>
<p><b>Function </b>A control output, e.g. rudder, throttle etc. Also called a <i>channel<o:p></o:p></i></p>
<p><b>Fuse</b> Fuselage </p>
<p><b>g</b> (lower case, not italicized) gram</p>
<p><b><i>g</i></b> (italicized) An arbitrary constant, force divided by mass in
an accelerative field (gravitational, electric or magnetic). <i>g=F/m </i>(=9.806m/s<sup>2</sup>
average near the earth's surface).<i> <o:p></o:p></i></p>
<p><b>Glow </b> An IC motor that uses a glow plug (as opposed to
spark ignition) and burns alcohol/nitromethane/lubricant fuel. Most glow
engines are two-stroke.</p>
<p><b>gram</b> (g) A unit of mass or inertia. The force equivalent is 9.806mN
(0.03527 oz) at the earth's surface.</p>
<p><b>Ground effect</b> Increased L/D that becomes significant when
an airplane or helicopter is within approximately one half span (or rotor
radius) of the ground. </p>
<p><b>Gyro </b>Gyroscope. An electromechanical or piezoelectric sensor that outputs
a signal proportional to angular acceleration.</p>
<p><b>H</b> (not italicized) henry</p>
<p><b><i>H </i></b>(italicized) Magnetizing force, measured in amp-turns per
metre (A/m).</p>
<p><b>Helistat</b> An airship that derives at least 40% of its lift from
propellers.</p>
<p><b>henry</b> (H) Unit of inductance (weber/amp). </p>
<p><b>hertz</b> (Hz) Unit of frequency (cycle/second). </p>
<p><b>High rate</b> Describes an ESC with a switching frequency
between 50kHz and 250kHz. Switching frequencies above 50kHz are usually used
with coreless motors.</p>
<p><b>HTA </b> Heavier-Than-Air. Any aircraft whose flight does not
depend on the buoyancy of lifting gas. All aircraft except balloons and
airships. </p>
<p><b>Hz</b> hertz</p>
<p><b><i>I</i></b><i> </i> Current</p>
<p><b>IC </b> 1. Internal combustion. 2. Integrated circuit. </p>
<p><b>i.d.</b> Inside diameter</p>
<p><b>IF</b> Intermediate frequency. For superheterodyne receivers
a (usually) much lower fixed frequency, such as 455kHz, to which the antenna
output is converted and at which filtering, detection and amplification take
place. </p>
<p><b>Impedance</b> <i>(Z)</i> Opposition to current, or the property of a
conductor that opposes current (measured in ohms). There are two types of
impedance: resistance <i>(R)</i> and reactance <i>(X).</i> </p>
<p><b>Incidence</b> Angle between the chord line of a flying surface and
a fuselage reference axis. </p>
<p><b>Inductance</b> <i>(L)</i> 1. In general, the capacity of a conductor to
produce a magnetic field. In particular, magnetic flux divided by current,
measured in henries (H). <i>L=</i><i><span style='font-family:GreekC'>F</span>/I</i><br>
2. The voltage a conductor generates divided by the rate of change of current
in that conductor (self inductance) or another conductor (mutual inductance). <i>L=
-V/(dI/dt),</i> where <i>dI/dt</i> is the rate of current change.</p>
<p><b>Induction</b> The process by which the gravitational, magnetic or
electric field of one body creates a field (of the same or different type) in
itself (self induction) or another non-contacting body (mutual induction). </p>
<p><b>Inductor</b> A passive device (e.g. coil of wire) that transforms electrical
energy into potential energy stored in a magnetic field, and vice versa (i.e.
provides inductance).</p>
<p><b>Inertia </b>The capacity of a body to resist acceleration, measured in
kilograms.</p>
<p><b>Inertial moment </b>Moment of inertia </p>
<p><b>Infrared </b>(IR) Electromagnetic radiation whose wavelength ranges
between 1mm (short microwaves) and 0.8um (visible red light) and can be used to
transmit control signals.</p>
<p><b>J</b> joule</p>
<p><b>Jap tissue</b> Fine grain tissue paper made by Esaki Model Co. primarily
from gampi bark. Used as a covering material. Comes in white and colors. Often
painted with dope.</p>
<p><b>joule</b> (J) <i>(jewel) </i>Unit of energy (kg-m<sup>2</sup>/s<sup>2</sup>=N-m).</p>
<p><b>JST</b> Japan Solderless Terminal. A type of electrical
connector, most commonly the ZM series (1.5mm pitch) made by JST Mfg. Co. Ltd.
</p>
<p><b>k </b> (lower case) kilo-. Unit prefix signifying 1000</p>
<p><b>kg</b> kilogram. A unit of mass or inertia. The force equivalent is
9.806N (35.27 oz) at the earth�s surface.</p>
<p><b>Kinetic energy</b> (<i>KE</i>) The energy possessed by a body by virtue
of its motion (<i>KE</i>=1/2<i>mv</i><sup>2</sup>), expressed in joules (J).</p>
<p><b><i>L</i></b> (italicized) Inductance</p>
<p><b>L</b> (not italicized) liter</p>
<p><b><i><span style='font-family:GreekC'>l</span></i></b> Wavelength</p>
<p><b><i>L/D</i></b> (L over D) Ratio of lift to drag for a flying
surface or an airplane. </p>
<p><b>LE</b> Leading edge. Forwardmost part of a flying surface. </p>
<p><b>LED</b> Light Emitting Diode. Semiconductor that converts
electrical energy to light. </p>
<p><b>LHS </b>Local hobby shop</p>
<p><b>Li </b> lithium. A chemical element. A type of cell electrolyte with
high specific energy. </p>
<p><b>Lift </b>Aerodynamic force perpendicular to the relative wind (measured
in newtons or grams).</p>
<p><b>Lift slope</b> <i>(a)</i> = <i>dC<sub>L</sub> /d</i><i><span
style='font-family:GreekC'>a</span></i>. Rate of change of lift
coefficient with respect to angle of attack.</p>
<p><b>Load factor</b> Lift divided by rest weight.</p>
<p><b>Loop </b>An aerobatic maneuver in which the flight path describes a
vertical circle.</p>
<p><b>LRK</b> Describes a type of BL outrunner motor developed by Christian
Lucas, Ludwig Retzbach and Emil Kuerfuss</p>
<p><b>LTA </b> Lighter-Than-Air. Aircraft category that includes balloons,
airships, i.e. any type that depends for flight upon the buoyancy of lifting
gas such as helium, hydrogen or hot air. </p>
<p><b>lumen</b> (lm) Unit of luminous flux (quantity of light)
(=candela-steradian). </p>
<p><b>LVC </b>Low voltage cutoff. Also called <i>auto cutoff</i>.</p>
<p><b>m</b> (lower case, not italicized) 1. milli- Unit prefix signifying
1/1000.<br>
2. metre.</p>
<p><b><i>m</i></b> (lower case, italicized) Mass</p>
<p><b>M</b> (upper case) mega- Unit prefix signifying 10<sup>6</sup>.</p>
<p><b>MAC </b> Mean Aerodynamic Chord. For a flying surface, the
theoretical chord line through which the sum of aerodynamic forces and moments
is assumed to act.</p>
<p><b>Magnetic flux</b> (<i><span style='font-family:Symbol'>F</span></i>) The
force field created by electric current, measured in webers (Wb) <b><o:p></o:p></b></p>
<p><b>Magnetic flux density</b> (<i>B</i>) Magnetic field strength divided by
area, measured in teslas (T).</p>
<p><b>Magnetic force</b> An effect of magnetism, the force of interaction
between electric currents, measured in newtons (N).</p>
<p><b>Magnetomotive force</b> (MMF) The potential energy concentration in a
magnetic field (the ratio of energy to magnetic flux), expressed in amps. (A
misnomer since MMF is an energy concentration, not a force.)</p>
<p><b>mAh</b> milliamp-hour. Unit charge supplied by 1mA flowing
for one hour. 1mAh=3.6C.</p>
<p><b>Mass</b> <i>(m)</i> The property of matter or energy that resists
acceleration (cf. inertia) and serves as the starting point for accelerative
field force (gravitational, electric or magnetic). In particular, the mass
value of a specified body, measured in grams (g) or kilograms (kg). </p>
<p><b>MAV</b> Micro Aerial Vehicle. Span < 15cm. </p>
<p><b>Metacentric height</b> For airships, the vertical distance
between CG and CB. For airplanes, the vertical distance between CG and CLA. </p>
<p><b>micron</b> Obsolete term for <i>micrometre</i>.</p>
<p><b>MMF</b> Magnetomotive force</p>
<p><b>Module </b> For gears, the pitch diameter (in mm) divided by
number of teeth. The metric analog of diametral pitch. Common modules are
(0.20, 0.25, 0.30, 0.35 and 0.50)mm. Module=25.4/diametral pitch. </p>
<p><b>Modulus of elasticity </b>(<i>E</i>)<b> </b>The resistance of material to
deformation (inherent rigidity or stiffness). Within the limits of elasticity,
the ratio of stress to strain, a.k.a. <i>Young�s modulus,</i> expressed in
pascals (Pa). </p>
<p><b>Moment </b>A twisting force (a.k.a. torque) that tends to cause rotation.</p>
<p><b>Moment arm </b>The perpendicular distance from a force to the axis of
rotation (i.e. the length of a fulcrum or lever arm), expressed in metres. </p>
<p><b>Moment of inertia</b> (<i>J</i>) Torque divided by angular acceleration,
measured in kg-m<sup>2</sup>. In statics, the second moment of area.</p>
<p><b>Momentum </b>(<i>p</i>)<b> </b>The product of mass and velocity (<i>p</i>=<i>mv</i>),
expressed in kg-m/s. </p>
<p><b>MOSFET</b> Metal Oxide Semiconductor Field Effect Transistor<i>
<o:p></o:p></i></p>
<p><b>Motor</b> A device that supplies mechanical energy (e.g. an engine,
electric motor, or actuator).</p>
<p><b>MTBF</b> Mean Time Between Failure. The average length of
time a component or system will perform before failure occurs(initially or
after repair or replacement), specified in hours.</p>
<p><b>n</b> nano- A unit prefix signifying 10<sup>-9</sup>. (Never
capitalized.)</p>
<p><b>N</b> newton (Always capitalized.)</p>
<p><b>NC</b> No connection or normally open</p>
<p><b>Neutral point</b> (NP) The point about which the sum of aerodynamic
moments can theoretically be assumed to act.</p>
<p><b>newton</b> (N) A unit of force equal to one kilogram-metre per
second squared (kg-m/s<sup>2</sup>).</p>
<p><b>newton-metre</b> (N-m) Unit of torque or moment. (Small
amounts are expressed in mN-m.)</p>
<p><b>NiCd </b> <i>(nigh cad)</i> Nickel cadmium. A type of
secondary cell. </p>
<p><b>NiMH</b> Nickel metal hydride. A type of secondary cell. </p>
<p><b>NO</b> normally open</p>
<p><b>NP</b> Neutral point</p>
<p><b>o.d.</b> Outside diameter</p>
<p><b>ohm</b> (<span style='font-family:Symbol'>W</span>) Unit of
impedance. </p>
<p><b><i><span style='font-family:GreekC'>w</span></i></b> Angular
velocity</p>
<p><b>OOS</b> Out of Sight. Refers to a model aircraft with which
visual contact has been lost. </p>
<p><b>Outrunner </b>Describes a type of brushless motor in which permanent
magnets rotate around the outside of an armature stator.</p>
<p><b>p </b> pico- Unit prefix signifying 10<sup>-12</sup>. (Never
capitalized.) </p>
<p><b><i>P</i></b> Power</p>
<p><b>P-effect</b> Yaw generated when the relative wind hits a propeller disk
non-perpendicularly (i.e. not parallel to the propeller shaft).</p>
<p><b>Pa</b> pascal</p>
<p><b>Parasol</b> High wing monoplane configuration with cabane struts
connecting the wing to the fuselage.</p>
<p><b>pascal</b> (Pa) Unit of pressure or stress (N/m<sup>2</sup>). </p>
<p><b>Passive</b> Describes a class of electrical devices that do not have a
built-in source of power (resistor, capacitor and inductor).</p>
<p><b>PCB</b> Printed Circuit Board. </p>
<p><b>PCM</b> Pulse code modulation. Analog carrier encoding for RC signals.
Technically, PCM is a form of encoding, not modulation.</p>
<p><b>PD </b>Pitch diameter</p>
<p><b>Peanut scale</b> Rubber scale FF event in which wingspan is
generally limited to 13 inches. </p>
<p><b>PIC</b> Programmable integrated circuit. </p>
<p><b>Piezoelectric </b><i>(pee ay zo)</i> Describes a material (or a specimen
made from a material) that generates an electric charge when mechanically
deformed and deforms when an electric charge is applied.</p>
<p><b>Pitch</b> 1. Diametral pitch. For gears, the number of teeth per inch of
pitch diameter. To convert from metric, DP=25.4/module. Common gear pitches are
32, 48 and 64.<br>
2. The distance a propeller will advance in one revolution along the blade
chord line, assuming no slip.<br>
3. (<i>v.tr.</i>) To rotate, or (<i>n.</i>) the angle or rotation about the
lateral axis (nose up or nose down).<br>
4. Center-to-center distance between connector pins, measured in mm.</p>
<p><b>Pitch diameter</b> (PD) The diameter of a pitch circle. When gear sets
are idealized as smooth, contacting disks, the pitch circle represents the
outside edge of the disk. </p>
<p><b>Polyhedral</b> More than two dihedral breaks in a wing.</p>
<p><b>Pot</b> Potentiometer or variable resistor. </p>
<p><b>Potential energy </b>(<i>PE</i>) The rest energy stored in a body or
system by virtue of mechanical deformation, its position within an accelerative
field, or electrical or chemical state, measured in joules (J).</p>
<p><b>Power </b><i>(P)</i> The rate at which work is done or energy is
produced or consumed, measured in watts (W). The output power of a motor is <i>P=</i><i><span
style='font-family:GreekC'>w</span>T</i> when [angular displacement] = radians,
and 2<span style='font-family:GreekC'>p<i>w</i></span><i>T</i> when [angular
displacement] = revolutions. For electrical power, <i>P=IV=I</i><sup>2</sup><i>R=V</i><sup>2</sup><i>/R</i>
(Joule's Law). In mechanics, <i>P=E/t=Fv</i>, where <i>E </i>is energy, and <i>v</i>
is speed.</p>
<p><b>PPM</b> Pulse Position Modulation. A common form of analog carrier
encoding for RC signals. Technically, PPM is a form of encoding, not
modulation.</p>
<p><b>Primary</b> A throw away cell type that is not rechargeable. </p>
<p><b>Propeller constant </b>A physical quantity that when multiplied by the
square of propeller speed gives the amount of torque a propeller absorbs. Or
equivalently, the amount of torque the propeller absorbs at one unit of angular
velocity. <i>P.C.</i> = <i>T</i>/<span style='font-family:GreekC'>w</span><sup>2<o:p></o:p></sup></p>
<p><b>Propo</b> Proportional. Describes an R/C system in which servo
output is a continuous linear function of Tx stick displacement. </p>
<p><b>Pull-pull</b> A type of control linkage that uses two cables in tension
instead of a pushrod.</p>
<p><b>Pusher </b>A type of propeller<b> </b>that rotates clockwise when viewed
from the front and is usually mounted behind the motor<b>.<o:p></o:p></b></p>
<p><b>PWM</b> Pulse width modulation. Describes the input signal-encoding
format for standard servos (vs. actuators, which use an analog voltage input).
Technically, PWM is a form of encoding, not modulation</p>
<p><b><i>Q</i></b> Electric charge, measured in coulombs.</p>
<p><b><i>R</i></b> Resistance</p>
<p><b><i>R</i><sub>a</sub></b> Armature resistance of an electric
motor. Also called <i>R</i><sub>m</sub><i> </i>(motor resistance).</p>
<p><b>rad/s </b>radian per second</p>
<p><b>radian</b> (rad) An angle equal to 180/<span style='font-family:GreekC'>p
</span>(= 57.296<span style='font-family:GreekC'>)</span><sup>o<o:p></o:p></sup></p>
<p><b>R/C</b> (or RC) Radio control. Remote control via radio uplink. </p>
<p><b>Reactance</b> <i>(X)</i> The impedance that arises when current or
voltage changes. Electrical energy is stored as potential energy in an electric
or magnetic field, measured in ohms. Reactance varies as a direct function of
the rate of current change (inductive reactance <i>X</i><sub>L</sub>) and an
inverse function of voltage change (capacitive reactance <i>X</i><sub>C</sub>).
</p>
<p><b>Reactive </b>Describes a device (e.g. capacitor, inductor or motor) that
generates voltage in response to voltage or current change. There are two types
of reactive devices: passive and active.</p>
<p><b>Resistance</b> <i>(R)</i> A type of impedance that causes electrical
energy to be dissipated as heat or radiation, measured in ohms.</p>
<p><b>Resistivity</b> (<span style='font-family:GreekC'>r</span>) Specific
resistance, a material property. <span style='font-family:GreekC'>r</span>=<i>RA/L</i>,
where <i>L</i> is the length of a conductor of constant cross sectional area <i>A,
</i>made of the subject material. Measured in ohm-metres (<span
style='font-family:GreekC'>W</span>-m).</p>
<p><b>Resistor </b>A passive device that purposely dissipates electrical
energy.</p>
<p><b>Resultant </b>A force (or moment) equal to the vector sum of multiple
forces (or moments).</p>
<p><b>rev</b> Revolution (360<sup>o</sup>)</p>
<p><b>Reverse expo</b> A feature of some control linkages, Tx
programming or ESCs wherein sensitivity <i>decreases</i> as stick displacement <i>increases</i>.
</p>
<p><b>Reynolds number</b> (<i>Re</i>) A dimensionless constant that expresses
scale effect, the ratio of inertial to viscous forces in fluid flow (<i>Re = </i><span
style='font-family:GreekC'>r</span><i>vL/</i><i><span style='font-family:GreekC'>m</span>,
</i>where <span style='font-family:GreekC'>r</span>=fluid density<i>, v=</i>speed<i>,
L=</i>characteristic length, and <i><span style='font-family:GreekC'>m</span> =</i>fluid
viscosity)<i>.<o:p></o:p></i></p>
<p><b>RF</b> Radio frequency. An AC frequency high enough to
produce electromagnetic radiation. Approx 4kHz to 10GHz in practical applications.
</p>
<p><b>Rigger's line</b> A line tangent to the underside of a flat bottom or
undercambered airfoil.</p>
<p><b>RMS</b> Root mean square. The equivalent DC amplitude of an AC
signal. For a sinusoidal waveforms, <i>V</i><sub>rms</sub>=0.7071<i>V</i><sub>peak<o:p></o:p></sub></p>
<p><b>ROC</b> Rate of climb. </p>
<p><b>ROG</b> Rise Off Ground. Take off, usually from wheeled landing
gear (versus hand launch). </p>
<p><b>Roll </b>Angle or rotation about the longitudinal axis (bank). Also, an
aerobatic maneuver.</p>
<p><b>Room flyer</b> An RC aircraft that can be easily flown in a normal size
living room.</p>
<p><b>Rotational velocity</b><i> </i>Angular speed</p>
<p><b>ROW</b> Rise Off Water </p>
<p><b>RPV</b> Remote Piloted Vehicle. A recoverable, non-autonomous
UAV controlled from a distant location through a communication link,
transmitting data to a remote controller and reacting to operator commands and
other control inputs. </p>
<p><b>RTF</b> Ready to Fly </p>
<p><b>RTP</b> Round the Pole. Electric control line airplane
tethered to a pylon, with the pilot located outside the circle, controlling
elevator, throttle or other functions. </p>
<p><b>Rudder </b>A control surface hinged to the TE of a vertical stabilizer
that generates yawing moment.</p>
<p><b>Ruddervator</b> A differential/collective control surface
(rudder+elevator) used with V-tail.</p>
<p><b>Rx</b> Receiver. A device that intercepts and decodes a Tx
signal. </p>
<p><b>s </b>(lower case) Second (Unit of time).</p>
<p><b>S</b> (upper case) 1. siemen (unit of conductance).<br>
2. Integer suffix that indicates series connection. E.g. 2 cells in series are
denoted <i>2S</i></p>
<p><b>Safe Start</b> An ESC feature that prevents current from flowing
through the motor when the battery is initially connected.</p>
<p><b>Scale factor</b> A number used as a multiplier in scaling (e.g.
between the size of a scale model and the full size prototype).</p>
<p><b>Secondary</b> A type of cell that may be recharged
(rechargeable).</p>
<p><b>Semi-hedral</b> Two dihedral breaks in a wing</p>
<p><b>Servo</b> A closed-loop electromechanical actuator consisting
of a motor, gear train, feedback element, error detector and amplifier arranged
to position an output arm in response to a control signal. </p>
<p><b>Shift</b> Frequency deviation, particularly as it pertains to FM. May be
positive or negative.</p>
<p><b>SI </b> The international standard system of measurement.</p>
<p><b>Slow Flyer </b>Micro R/C airplane with low wing loading and high lift
coefficient. </p>
<p><b>SMT</b> Surface Mount Technology (or SMD, surface mount
device). A technique for minimizing the volume and mass of device packaging.</p>
<p><b>SOA</b> Safe Operating Area. The region bounded by voltage
and current combinations that permit rated life and performance of a device to
be obtained. </p>
<p><b>Span loading</b> (<i>b<sup>2</sup>/w)</i> Wingspan squared divided
by weight. Influences climb efficiency. </p>
<p><b>SPDT</b> Single pole double throw </p>
<p><b>Specific energy</b> <i>(E</i><sub>s</sub><i>)</i> Energy capacity
divided by mass. Measured in joules per gram (J/g) or J/kg. <i>E</i><sub>s</sub><i>=</i>3.6<i>QV/m</i>,
where <i>Q</i> is capacity (mAh) and <i>m</i> is mass (g). </p>
<p><b>Speed constant</b> (<i>K</i><sub><span style='font-family:GreekC'>w</span></sub><i>
</i>) <i>k sub omega</i> The speed of an electric motor divided by back
voltage. <i>K</i><sub><span style='font-family:GreekC'>w</span></sub><i>=</i><i><span
style='font-family:GreekC'>w</span>/(V-I*R</i><sub>a</sub><i>)</i>=<i><sub> </sub></i><i><span
style='font-family:GreekC'>w</span>/E.</i> Expressed in radians per volt-second
(rad/V-s) or Wb<sup>-1</sup>. Also called <i>velocity</i> <i>constant </i>or <i>voltage</i>
<i>constant</i> <i>(K</i>v<i>)</i> and given in rpm/volt. <i>K</i><sub><span
style='font-family:GreekC'>w</span></sub><i>=1/K</i><sub>E</sub><i>=</i>1<i>/K</i><sub>T</sub>.
</p>
<p><b>SPST </b>Single pole single throw </p>
<p><b>Stab </b> Stabilizer </p>
<p><b>Stabilator</b> Stabilizer+elevator (also called full-flying
tail). A variable incidence horizontal stabilizer controlled by the pilot (in
lieu of an elevator).</p>
<p><b>Stabilizer</b> A fixed aerodynamic surface that maintains equilibrium
in pitch or yaw</p>
<p><b>Static margin </b>The horizontal distance from CG to NP, divided by MAC.
When CG is ahead of NP, static margin is assigned a positive value.</p>
<p><b>Step</b> The smallest control signal increment a receiver, servo,
ESC or actuator can resolve.</p>
<p><b>STOL </b> Short Take Off and Landing. Ability to take off and
land in a short distance. </p>
<p><b>Superheterodyne </b>A receiver demodulation scheme that converts an
antenna output to a usually much lower fixed intermediate frequency (IF) such
as 455kHz, at which filtering, detection and amplification take place. </p>
<p><b>Switching frequency</b> Rate at which a switched power supply (ESC)
turns its output on and off, measured in hertz. Higher switching frequency
enables more efficient power transfer. </p>
<p><b>T</b> tesla </p>
<p><b><i>t </i></b> Time, measured in seconds (s).</p>
<p><b>Tail dragger</b> Landing gear configuration with two main wheels ahead of
the CG, and a tailwheel.</p>
<p><b>Taileron</b> A stabilator with collective and differential
actuation. </p>
<p><b>Tangential displacement</b> The linear distance traveled along a curved
path</p>
<p><b>TE </b> Trailing edge. The rearmost edge of a flying surface. </p>
<p><b>tesla </b>Unit of magnetic flux density (Wb/m<sup>2</sup>).</p>
<p><b>Thrust </b>Propulsive force, measured in newtons or grams.</p>
<p><b>Torque</b> <i>(T)</i> Twisting force (tends to cause rotation) or moment,
measured in newton-metres (N-m), or millinewton-metres (mN-m). <i>T=Fd</i>,
where <i>d</i> is the moment arm, and <i>F</i> is the component of force
perpendicular to the moment arm.</p>
<p><b>Torque constant</b> <i>(K</i><sub>T</sub><i>)</i> The torque produced by
an electric motor divided by current draw minus no-load current. <i>K</i><sub>T</sub><i>=T/(I-I</i><sub>0</sub><i>).</i>
Expressed in newton-metres per amp (N-m/A) or webers (Wb). <i>K</i><sub>T</sub><i>=K</i><sub>E</sub><i>=1/K</i><sub><span
style='font-family:GreekC'>w</span></sub><i>.</i> </p>
<p><b>Torque reaction</b> A rolling couple created by a propeller, or the
yawing couple created by a rotor.</p>
<p><b>Tractor </b>A type of propeller that rotates counter-clockwise when
viewed from the front, and is usually mounted in front of the motor.</p>
<p><b>Transition</b> The region in which a boundary layer changes from laminar
to turbulent. </p>
<p><b>Tricycle </b>A type of landing gear configuration</p>
<p><b>Trim</b> For R/C aircraft, to adjust CG location, thrust angle and
control surface neutral settings so as to permit hands off flight, or the
levers on a Tx that control such settings. For FF; to adjust alignment, CG,
thrustline and control tabs in order to achieve desired flight pattern.</p>
<p><b>Tx </b> Transmitter. A device that generates a radio signal
intended for remote reception. (Sometimes called a <i>controller</i>.) </p>
<p><b><span style='font-family:Symbol'>m</span> </b> (not
italicized) (pronounced <i>micro</i>) A unit prefix that signifies 1/1,000,000.</p>
<p><b><i><span style='font-family:Symbol'>m</span></i></b><i><span
style='font-family:Symbol'> </span></i>(italicized) (pronounced <i>myoo</i>)
Magnetic permeability</p>
<p><b>UAV</b> Unmanned Aerial Vehicle. A powered aerial vehicle sustained
in flight by aerodynamic lift and guided without an onboard crew. It may be
expendable or recoverable, and can fly autonomously or be piloted remotely.
There are two categories of UAVs: drones and RPVs.</p>
<p><b>UBEC </b>Ultimate battery eliminator circuit. A BEC used with high
voltage batteries or high current control systems that employs a switched
regulator instead of a series pass regulator. </p>
<p><b>U-Control</b> Control line. Also called <i>ukie</i> or <i>U/C</i>.</p>
<p><b><span style='font-family:Symbol'>m</span>m </b> micron or
micrometre. One-millionth of a metre.</p>
<p><b>Unit variation</b> Random and unpredictable deviations in the performance
of putatively identical products due to imprecise or inconsistent manufacturing
processes or quality controls. Also called <i>unit to unit variation</i>.</p>
<p><b>Uplink</b> A means of transmitting information from the user to a remote
device, or the act of uplinking<span style='font-size:10.0pt'>.<o:p></o:p></span></p>
<p><b>V</b> (not italicized) volt</p>
<p><b><i>V</i></b> (italicized) Voltage</p>
<p><b>Vector </b>A quantity that has a magnitude and a direction (e.g. force or
velocity).</p>
<p><b>Ventral </b>Relating to the underside of a body.</p>
<p><b>volt </b>(V) Unit of voltage (joule per coulomb). </p>
<p><b>Voltage</b> <i>(V)</i> In general, the potential energy concentration in
an electric field (the ratio of energy to charge). In particular, joules per
coulomb, expressed in volts. <i>V=E/Q=IR.<o:p></o:p></i></p>
<p><b>Voltage constant </b>See <i>back voltage constant<o:p></o:p></i></p>
<p><b>VTOL </b>Vertical takeoff and landing (e.g. helicopter) </p>
<p><b>Washin </b>A warp or the act of warping a wing so that tip
chord incidence is <i>more than</i> the root chord incidence</p>
<p><b>Washout </b>Building or warping a wing so that tip chord
incidence is <i>less than</i> the root chord incidence, usually distributed
over the outer 1/3 of the wing.</p>
<p><b>watt</b> (W) Unit of power (joule per second). </p>
<p><b>Wavelength</b> (<i><span style='font-family:GreekC'>l</span></i>) The
distance occupied by one cycle of a wave, measured in metres. Usually applies
to electromagnetic radiation (<i><span style='font-family:GreekC'>l</span>=c/f</i>)
or sound waves<i>.<o:p></o:p></i></p>
<p><b>Wb</b> weber</p>
<p><b>weber</b> (Wb) Unit of magnetic flux or magnetism (volt-second). </p>
<p><b>Weight</b> <i>(w)</i> 1. Gravitational force (usually the earth's) acting
on a body of mass, measured in newtons. <i>w=mg</i>, where <i>g</i> is the
acceleration of gravity (average 9.806m/s<sup>2</sup>). Often synonymous with <i>mass</i>,
and measured in grams (g) or kilograms (kg).<br>
2. The amount of force needed to keep a body at rest with respect to its
inertial frame (also called <i>g-force</i> or <i>apparent weight</i>).</p>
<p><b>Wh </b>Watt-hour (a unit of energy) 1W-hr = 3.6kJ. <b><o:p></o:p></b></p>
<p><b>Wingeron </b> Wing+aileron. Wing incidence differentially controlled
by the pilot, in lieu of ailerons. </p>
<p><b>Wing loading</b> <i>(w/S)</i> Weight divided by wing area, measured
in g/dm<sup>2</sup> or ounces per square foot. Influences efficiency and stall
speed.</p>
<p><b>Work</b> The conversion of energy to a useful form, measured in joules.
Particularly, force times the displacement parallel to the force</p>
<p><b><i>X </i></b><i> </i>Reactance</p>
<p><b>Xformer</b> Transformer</p>
<p><b>Xtal </b> Crystal. Quartz piezoelectric (pee-ay-zo-electric)
circuit element used in angular acceleration sensors and often serves as a
frequency reference for Tx and Rx oscillators.</p>
<p><b>Yaw </b>Angle or rotation about the vertical axis (nose left or nose
right).</p>
<p><b><i>Z</i></b> Impedance</p>
<p><b>Zeppelin</b> A rigid airship (after Graf Ferdinand von Zeppelin).</p>
<p><b>Zero lift line</b> The chord line that is parallel to the
relative wind when a wing is not producing lift. </p>
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