Glossary

Like any specialist subject, modelling makes use of many terms whose meaning is not necessarily clear to a newcomer. This glossary should help those unfamiliar with some areas of modelling. It will be expanded regularly.

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A
ABS.
A type of plastic often used for vacuum formed components such as cowlings.
ACTUATOR.
A device for moving a control surface or throttle by electro-mechanical means.
ADVERSE YAW.
A turn in the direction opposite to that introduced by the ailerons, caused by the drag of the down-going aileron exceeding the turning moment introduced by the up-going aileron.
AERIAL.
On a transmitter a metal rod, usually collapsible, which radiates the transmitted signal; or a trailing or rigid wire on a receiver which collects the signal.
AERODYNAMICS.
The science or study of the forces acting on an aircraft in motion.
AEROFOIL.
The cross-section shape of a wing taken at right angles to the wing span., Also known as the wing section or rib section.
AEROTOW.
A method of launching a glider by towing it to altitude behind a powered aircraft.
AIRBRAKE.
An aerodynamic control which can be extended to increase drag and slow down an aircraft
ALL FLYING TAIL
Horizontal tail surfaces which do not have a separate elevator. The whole surface moves as one to give pitch control.
AMPHIBIAN.
An aircraft capable of operating off either land or water.
ANEMOMETER.
A device for measuring wind speed.
ANHEDRAL
Where the wings are set an angle such that the tips are lower than the centre. The opposite of DIHEDRAL
ANGLE OF ATTACK.
The angle at which a wing strikes the air stream.
ANGLE OF INCIDENCE.
Angle of the wing in relation to an arbitrary line fore and aft in the fuselage.
ASPECT RATIO.
The relationship of the wing span to the wing chord, expressed numerically by the number of times the span can be divided by the chord.
AUTOGIRO.
An aeroplane that flies by virtue of the lift generated by freewheeling rotating wings set 'windmill'' fashion above the fuselage. The forward motion of the autogiro provides the force to keep the rotors turning so unlike a helicopter the autogiro cannot hover.
AUTO-RUDDER (A/R)
A system used in free-flight models either to keep the rudder of a glider straight during tow and then automatically to set the glide turn on release, or, on rubber- and power-driven aircraft, to alter the rudder setting in flight, usually to re-trim from power to glide.
B
BALSA WOOD.
Very light wood with excellent strength -to-weight ratio. Grown mainly in South America and used extensively in model aeroplane construction.
BALLAST.
Weight carried by an aeroplane to increase the Wing Loading.
BANK.
A turn made in flight with one wing lip lower than the other.
BATTERY.
A means of storing electrical power chemically.
BEAM MOUNT.
Engine mounting consisting of a plate or beams to which the engine is mounted by means of the lugs on either side of the crankcase.
BELLCRANK
The pivoted wood, metal, or plastic arm which converts the motion of the control lines to up-and-down movement of the elevators in a control line model aeroplane.
BOOM.
A wood tube or strip that extends rearward from the wings or from a short fuselage to support the tail surfaces.
BULKHEAD
A former within the fuselage used as internal support for longerons, sheet sides, stringers and so on.
BUNTER.
A free-flight aircraft, either engine-assisted or a glider, which uses a quarter outside loop to effect the transition from climb or high-energy tow-launch into the glide, and thus maximise the possible altitude and hence duration.
C
CABANE
The strut assembly at the centre section of a biplane or Parasol monoplane.
CAMBER.
The curvature of the wing or horizontal tail, from the leading edge to the trailing edge.
CANARD.
An aeroplane designed to fly with its tailplane in front of the wing.
CANTILEVER
A wing built in such a way that it does not require external bracing. Model scale aircraft may have dummy external bracing to replicate the original even though the wings are actually strong enough not to need it.
CENTRE OF GRAVITY. OR WEIGHT (CoG).
The spot where the mass or weight of an aeroplane may be said to centre.
CENTRE OF LIFT (CL).
The spot where the lift of a wing (or wings) is said to centre.
CENTRE OF PRESSURE (CP).
The point on the upper surface of a wing. Relative to the chord. Where the lift can be said to centre.
CHORD.
The width of a wing or tailplane from front (leading edge) to back (trailing edge).
CIRCLE TOW.
A system by which a free-flight glider may be held captive on the towline and circled until the flyer detects a thermal into which to launch.
CIRCUIT.
A rectangular flight path around the runway in use; the flight-path used by aircraft approaching for landing.
CLEVIS.
A sprung link connecting a control rod to the surface being controlled.
CLOSED LOOP.
A means of operating a control surface by means of flexible wires, under tension, attached to either side; sometimes known as pull-pull.
CLUNK TANK.
A fuel tank where the fuel pickup (the ‘clunk’) is at the end of a flexible tube. Gravity ensures that the ‘clunk’ is always at the bottom, enabling fuel to be collected whatever the orientation of the fuel tank.
CONDENSER TISSUE.
An ultra-light paper, originally used for insulation in electronic capacitors, used for covering some types of indoor free-flight aircraft.
CONSTANT-CHORD- WING
One that has parallel leading and trailing edges, with no taper.
CONTROL-LINE (CL) FLYING.
A method of flying a model aircraft by means of two thin wires connecting the model to a control handle held by the pilot. The model flying in a circular path and its elevation is controlled by the pilot.
CONTROL HANDLE
Device held in the hand, to which control lines are attached; vertical rocking movements of handle are carried via lines to the aeroplane elevators.
CONTROL HORN.
An arm fastened to a control surface to which is connected the control rod.
COUPE D’HIVER.
The FAI’s F1G small free-flight rubber duration class, originated in France during World War 2.
COWLING.
A specially shaped nose to enclose an engine.
CRYSTAL.
A component used to determine the operating frequency of a Radio Transmitter or Receiver. The frequency or Channel of R/Cequipment can be changed by plugging in the appropriate crystals.
CYANOACRYLATE.
A type of instant acting adhesive.
D
DATUM.
A reference line or point from which measurements are taken.
DEAD STICK.
A term used to describe a power model making a glide approach after the engine has stopped.
DELTA.
An aircraft with a wing of a triangular planform.
DETHERMALISER (D/T).
A device operated by a slow-burning fuse or by a mechanical or electronic timer that puts a free-flight aircraft into a super-stalled condition to bring it down after a pre-set flight time .
DIHEDRAL
The uptilt of wing panels toward the tips. Dihedral is applied for purposes of stability and to provide a turning moment for rudder-only models.
DIFFERENTIAL.
(ailerons) When ailerons are set to give more up movement than down movement. This is to reduce the effect of adverse yaw.
DOLLY
A wheeled frame which a model sits on to effect a take-off. The dolly either remains on the ground or drops off almost immediately.
DOUBLER.
A second sheet of material fixed inside the main fuselage side sheets on each side. For added strength.
DOUBLE-SURFACE WING.
A wing which is covered on both top and bottom with paper, cloth or other material.
DOWNTHRUST.
The slight tilting down of the engine or propeller thrust line to exert a slight downward pull under pressure.
DOWNWIND.
In the circuit flying parallel with the runway in the opposite direction to take-off.
DRAG.
A force acting on an aeroplane resisting its acting on an aircraft in motion resisting the movement through the air.
DUCTED FAN (DF).
A small diameter multi-bladed fan, operated at high rpm inside a tube or duct. The ejected air provides thrust in the same way as a jet engine, which the DF is often used to simulate.
DUTCH ROLL
A side-to-side wallowing motion of a model, often caused by insufficient fin area.
E
ELEVATOR.
The hinged control section of the tailplane, used to control pitch.
ELEVON.
An elevator split into 2 halves which can be operated independently so that the same control surfaces can be used to control the roll of an aircraft as well as the pitch. Often seen on Flying Wings and Delta planform models.
ENGINE BRAKE
A timer-operated device to stop the propeller of a free-flight duration aircraft at the end of the permitted engine run.
F
FF.
Free Flight
FAIL SAFE.
A system which closes the throttle and moves the control surfaces to pre-set positions in the event of loss of signal from the transmitter. Required by larger models and is intended to bring the model to earth quickly in the event of radio interference or transmitter failure.
FAIRING.
A streamlined cover over a joint or around angular parts of an aircraft intended to reduce drag.
FILLET.
A rounded contour used at the junction of vertical and horizontal surfaces on an aeroplane, to reduce wind resistance.
FIN.
The fixed forward portion of the vertical tail surfaces.
FINAL APPROACH.
The last phase of a flight when lined up with the runway during the landing approach.
FIREWALL.
A strong bulkhead immediately behind the engine on a powered aeroplane.
FLAPS.
Hinged surfaces attached to the trailing edge of a wing, either to increase manoeuvrability (as on a control line aerobatic model) or to increase lift at the expense of drag (as on most full size aircraft and some radio control aeroplanes).
FLAPERONS.
Ailerons which can be moved both up or both down to act as spoilers or flaps.
FLUTTER.
Rapid oscillation of a wing or control surface. Usually appears only at high speed and is often caused by excessive gaps between wing and control surface, or by inadequately stiff control rods, or in the case of a wing insufficiently stiff structure.
FLYING BOAT.
An aeroplane with a fuselage shaped like a boat. For operation off water.
FLYING SCALE MODEL.
A flyable miniature of a manned aeroplane.
FORMER.
See Bulkhead.
FREEWHEELER
A propeller with a special device that allows it to windmill after the rubber motor is unwound.
FREQUENCY MONITOR.
Multi-channel radio receiver used to check for interference on model radio control frequencies.
FUSELAGE.
The body of an aeroplane.
G
GEODETIC.
A latticework or basket-weave construction.
GLIDER.
A highly efficient engineless aeroplane. Capable of flying for long periods in gently rising air currents (thermals).
GLITCH.
(colloquialism) momentary uncontrolled operation of control surfaces caused by electronic interference or equipment malfunction.
GROUND LOOP
A rapid circular rotation of a model on the ground, usually performed while taxying or during take off. Taildragger aircraft are particularly susceptible to this as they are sensitive to crosswinds.
GUSSET.
Small strengtheners fixed at points of heavy stress in an aircraft’s structure.
H
HAND-LAUNCH (HL).
To start a model in flight by releasing it or throwing it from the hand.
HELICOPTER.
An aircraft that can rise or descend vertically, by means of large overhead power-driven rotor or rotors,
I
INCIDENCE.
The angle, relative to the fuselage datum, at which a wing is set.
INDUCED DRAG.
Resistance of a wing to forward movement due to disturbance of the surrounding air and related to the lift produced by the wing.
INVERTED.
Flying upside down.
J
JAPANESE TISSUE.
A very light paper, usually made from rice straw, used for covering some free-flight aircraft.
JIG.
A fixture or form for holding parts together for assembly.
K
KNOCK-OFF.
A way of mounting parts such as wings, tailplane or undercarriage so that they will knock-off without damage in the event of a crash landing.
L
LANDING GEAR.
See Undercarriage.
LANDING WIRE
Bracing wires which take the non-flying loads on a wing or wings; usually found on bi-planes.
LEADING EDGE.
The front or entering edge of a wing or tail.
LEADOUT
The wires that are attached to the bellcrank and which extend out past the wing tip, to fasten to the control wires on a control line model.
LIFT COEFFICIENT.
An indication of the relative lift of an aerofoil.
LIFT-DRAG RATIO.
The relation of total lift to total drag of an aerofoil, expressed as a mathematical proportion; 6 to 1;15 to 1 and so on.
LOMCOVAK.
An aerobatic manoeuvre which combines extreme roll pitch and yaw changes to produce a violent movement of the aircraft. The name is derived from a Polish word which describes the effect of too much liqueur spirit.
LONGERONS.
The main fore-and-aft strips in a fuselage
M
MAX.
An abbreviation for the maximum time for which the flight of a free-flight aircraft is recorded, typically three minutes.
MICROFILM
A cellulose lacquer solution poured onto the surface of a tank of water to form an extremely thin film used for the covering of F1D and other types of free-flight indoor aircraft.
MID-AIR.
Collision of 2 models in flight.
MIXER.
A mechanical or electronic device which allows two different inputs to operate a control surface; flaperons for example.
MOMENT ARM.
The distance between the point at which a force is applied and the point of action of the force. For example, the distance between the CoG and nose, or CoG and tail.
MONOCOQUE.
A form of fuselage construction with rounded exterior and very little internal structure in which the skin carries virtually all stresses.
MOTOR BEARER.
Hardwood strip mount for model aeroplane engines.
MOTOR STICK.
A strong strip used to support the rubber motor; the body of stick-type models
MUSH
A nose-high, slow-speed flight attitude resulting from a slightly tail-heavy trim.
N
NEEDLE VALVE.
Fuel mixture adjustment on a model engine.
NICAD.
Nickel Cadmium rechargeable battery.
NORDIC.
The World Championship class for free-flight gliders (F1A), the specification for which originated in Scandinavia.
NOSE PLUG.
A shaped wooden block used to support the propeller bearing in many rubber powered models.
O
OLEO
A shock absorbing system used in undercarriages.
O.O.S.
Out of sight of the timekeeper.
ORNITHOPTER.
An aeroplane that flies by flapping its wings like a bird.
P
PARASITIC DRAG.
Resistance to a forward aeroplane movement caused by any non-lifting components of the aeroplane.
PARASOL.
An aeroplane in which the wing is mounted above the fuselage on struts.
PEAK DETECT CHARGER.
A battery charger which uses the measured voltage of the battery pack to shut off charging rather than a timer.
PITCH (1).
The distance forward theoretically travelled by a propeller in one revolution.
PITCH (2).
A rotation of an aircraft up and down around the wing axis. This effect is caused by the elevator.
PITCH-DIAMETER RATIO.
The relation between the propeller pitch and diameter, expressed as a mathematical proportion, as 1.5 to 1, and so on.
PITCH STABILITY.
Stability of an aeroplane in climb and dive.
PLANFORM.
The outline of wing or tailplane when viewed from above.
PLANKING
Sheet-wood covering accomplished by glueing thin flat wood strips side by side on a fuselage.
PLYWOOD.
Sheet wood made by glueing together two or more very thin layers of wood with the grain of adjacent layers at right angles.
POD.
A short streamlined fuselage fitted with a boom to support the tail surfaces.
POD-AND-BOOM
A model that derives its name from the appearance of its short fuselage and tail-support boom.
POLYHEDRAL.
A form of dihedral in which there are one or more changes of dihedral in each wing panel.
PROPELLER.
An airscrew that pushes air backwards as it rotates, thus pulling the aeroplane forwards.
PUSHER
A plane in which the engine is mounted ahead of the propeller, so that the propeller pushes instead of pulls.
PVA.
A water based type of adhesive.
Q
QUICK LINK
A sprung clip, of metal or plastic, used to connect a pushrod to the actuator or control surface.
R
R/C.
Radio Control.
RADIAL MOUNT.
A moulded plastic or metal mount which is fastened to the mounting lugs of an engine and then bolted directly to the engine bulkhead or firewall.
RATE SWITCH
A switch on the transmitter which changes the amount of movement of a control surface when the stick is moved.
RANGE.
The maximum distance over which radio control can safely be maintained.
REFLEX.
A reversal of the camber on a flying surface. Often used on flying wing or delta planform aircraft.
RESISTANCE.
Air drag, or the opposition of the air to being displaced by the forward movement of an aeroplane.
RIB SECTION.
The cross-section shape of a wing, from leading to trailing edge.
RISE-OFF-GROUND (ROG).
Used of a free-flight aircraft, usually to an obsolete specification, that takes off as opposed to being hand launched.
ROLL.
A rotation of an aircraft around the longitudinal axis. This effect is produced by the ailerons.
ROOT.
The part of a wing where it meets the fuselage.
RUDDER.
The moving part of the vertical tail surface of an aeroplane which provides yaw control
S
SAILPLANE.
See glider.
SERVO.
A motor-driven device for moving controls of a radio controlled aeroplane.
SIDE THRUST.
Offsetting the propeller thrust line, so there is a slight sideways pull.
SIDEWINDER.
Colloquial expression describing an engine mounted on its side.
SINGLE-SURFACE WING.
A wing formed from a single sheet of balsa, or one that has a framework covered only on the top.
SLIPSTREAM.
The column of air pushed rearward by a rotating propeller; it always moves faster than the aeroplane itself.
SOLID MODEL.
A non-flying model formed from solid pieces of wood or plastic.
SPARS.
Spanwise load-carrying members of a wing or tail.
SPIRAL DIVE.
An ever-tightening downward corkscrew flying path.
SPIRAL STABILITY.
The characteristic of an aeroplane that permits high-speed banked turns without diving to the ground.
S.M.A.E.
Society of Model Aeronautical Engineers. The precursor of the BMFA.
SNAKE.
A type of flexible pushrod consisting of a plastic or braided metal wire inner, inside a plastic sleeve.
SPOILERS.
Controls which can be deployed into the airflow to ‘spoil’ the lift. Usually found on gliders and used to aid landing.
STABILITY.
The tendency of an aeroplane to return to level flight, after having been disturbed by an upsetting force.
STALL.
The complete loss of lift resulting from too steep an angle of attack.
STALLING ANGLE.
The particular angle at which a wing abruptly loses lift; usually expressed in degrees.
STICK
The operating arm on a transmitter which is moved to make the control surface move.
STOL
Short Take Off and Landing. Describes an aircraft with special high-lift devices to keep the take off or landing run as short as possible.
STREAMLINED.
The shape of the exposed contours of an aeroplane for the least possible air drag; usually rounded in front, pointed at the rear.
STRINGER.
Light, lengthwise fuselage strips intended more to give the desired shape than to add strength.
STRIP AILERONS.
Ailerons consisting of simple strips along the full length of the wing trailing edge.
SWEEPBACK.
The angling back of the wings from the centre, to increase directional stability or reduce drag at high speed
T
Tx.
Abbreviation for transmitter.
TAB.
A small adjustable surface on wing or tail surfaces, used to make small trim changes.
TAIL.
The surfaces (tailplane and fin) at the rear of a conventional aeroplane fuselage.
T-TAIL.
Arrangement where the tailplane is mounted on top of the fin.
TAILDRAGGER.
An aircraft which has an undercarriage arrangement where the mainwheels are under the wing with smaller wheel at the tail end of the fuselage. The aircraft sits on the ground with a nose-high attitude.
TAILPLANE.
The fixed horizontal tail surface.
TAILSKID
A fixed angular fixture use to support the tail end of an aircraft on the ground instead of a wheel.
TEMPLATE.
A stiff pattern for marking the outlines of pieces to be cut from sheet wood or metal.
THERMAL.
A rising column of relatively warm air.
THRUST.
The propulsive force developed by a driven propeller or jet engine.
THRUST LINE.
An imaginary line drawn along the propeller shaft and extending rearward through the aeroplane.
TIMER.
A lightweight clockwork or electronic device fitted to free-flight aircraft to operate in-flight systems and to control the dethermaliser.
TIP LOSS.
Reduction in lift near the tips of wings due to the leakage of the high-pressure air from beneath to the low-pressure area above.
TOP RUDDER
Rudder used when an aircraft is flying on its side to keep the flight path horizontal.
TORQUE.
The reactive force generated by a revolving propeller that tends to rotate the aeroplane in a direction opposite to the direction of the propeller rotation.
TORQUE METER.
A device used when winding the rubber motor of a free-flight aircraft that measures the torque stored in the motor and thus enables the maximum energy to be stored in it.
TORQUE ROLL.
An aerobatic manoeuvre that uses the torque reaction to accelerate the rate of roll of an aircraft.
TOWHOOK.
A hook fixed to the underside of a glider fuselage for attachment of the towline.
TOWLINE.
The launching cord used for pulling aloft a glider or sail plane.
TRACKER.
A lightweight radio transmitter carried by some free-flight aircraft to aid their location by means of a highly directional receiver.
TRAILING EDGE.
The rear edge of a wing or tail surface.
TRANSMITTER.
An electronic device for producing radio waves.
Tx
Abbreviation for transmitter.
TRICYCLE (TRIKE) UNDERCARRIAGE.
An undercarriage arrangement where the main wheels are set under the wing just behind the cog point, with the third wheel positioned under the nose just behind the engine. The aircraft sits on the ground with the fuselage level.
U
UHF.
Ultra High Frequency.
UNDERCAMBER.
The concave curve on the underside of some aerofoils.
UNDERCARRIAGE.
The wheel and strut assembly that supports an aeroplane at rest on the ground and during take-off and landing.
V
V-TAIL.
Tail consisting of 2 surfaces at an extreme dihedral angle. The elevator and rudder functions are mixed and the fin and rudder can be dispensed with.
VHF.
Very High Frequency.
VARIABLE INCIDENCE TAILPLANE (V.I.T.)
An automatic device that alters the tailplane incidence of a free-flight aircraft in flight to re-trim it after its climb.
VENTURI.
A tube reduced in diameter at its centre. Air flowing through it is speeded up by the change in shape.
VORTICES.
Twisting air disturbances resulting from the movement of a wing through the air.
W
WAKEFIELD.
The World Championship free-flight rubber-driven duration class (F1B) named after Lord Wakefield of Hythe who donated the trophy in 1928.
WASHIN.
Twist incorporated in wing tips to raise the leading edge, to give more incidence at the tip than at the root
WASHOUT.
Twist incorporated in wing tips to raise the trailing edge, to give less incidence at the tip than at the root.
WINDING TUBE.
A removable tube surrounding the rubber motor of a free-flight aircraft during winding, which protects the fuselage from damage in case of a motor breakage.
WING LOADING
Expression for the weight per unit wing area of a model. Thermal gliders might have a wing loading of around 10 or 12 ounces per square foot, large scale power models may be over 24 ounces per square foot.
WINCH
A motorised towline spool for launching gliders.
WING.
The principal supporting surface of an aeroplane.
WING SECTION.
The chord-wise cross section of a wing.
X
XTAL
Abbreviation for Crystal.
Y
YAW
A ‘side-to-side’ rotation of an aircraft around the vertical axis. This effect is produced by the rudder.
Z
ZOOM.
An abrupt and steep climb.