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I've started this glossary of terms for you to look at in case you see something you don't understand. I'll illustrate these terms with pictures as needed and as I find good ones.

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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.

Aerobatics - An 1913 a Frenchman by the name of Pegoud was the first person to perform aerobatics in a specially strengthened Bleriot. The first loop was made by Piotr Nesterov on 20<sup>th</sup> August 1913 in a Nieuport Monoplane.

Aerodynamics - The science or study of the dynamics or motion behavior of aircraft.

Airfoil - The cross-section shape of a wing taken at right angles to the wing span. Also known as the wing section or rib section.

AGL - Acronym for Above Ground Level.

Aileron - Hinged surfaces at the trailing edge or rear portion of the wing near the tips used to make the aircraft roll. When flying straight and level, moving the control stick to the right will raise the aileron on the right wing and lower the aileron on the left wing, thus increasing the lift on the left wing and decreasing the lift on the right wing.

Airbrake - An aerodynamic control which can be extended to increase drag and slow down an aircraft. On some aircraft the air brakes are used in conjunction with the ailerons for lateral control at low speeds where the ailerons become ineffective.

Amphibian - An aircraft capable of operating off either land or water.

Anemometer - A device for measuring windspeed.

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 chord line in relation to the longitudinal axis of the fuselage. This should not be confused with the Angle of Attack.

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. For example, a wing that is 10 times as long as it's width has an aspect ratio of 10:1 (read ten to one).

Autogyro - An airplane that flies by virtue of the lift generated by freewheeling rotating wings set to "windmill" above the fuselage. The forward motion of the autogiro provides the force to keep the rotors turning. Unlike a helicopter, the autogiro cannot hover.

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

Auto Rudder - 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.

Axis - The line around which a body rotates.

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Backlash - Term describing the amount of play between gears, or gear mesh. If too loose, the gear can slip, or strip the teeth. Too tight, and excessive wear is caused.

Ball Race - The inner or outer rings that form the tracks for the balls in a ball-bearing.

Balsa Wood - Balsa wood comes from the West Indian Corkwood tree (Ochroma lagapus). It is used in the construction of model aircraft as it is a very light and easily cut and formed. When selecting balsa wood it is important to consider the intended application as it varies considerably in density and hardness.

Ballast - Weight carried by an airplane to increase the Wing Loading or adjust the center of gravity.

Bamboo - A natural material with a great strength to weight ratio. It was used in the early construction of wings and fuselages.

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.

Bearing - The supports that are used to hold a rotating shaft in position. Small internal combustion engines such as those used to power model aircraft often use phosphor bronze for the main crank bearings. As well as holding the crankshaft in-line and reacting the thrust from the propeller they form a seal between the crankshaft and the crankcase so allowing the air-fuel mixture in the crankcase to be compressed (two-stroke engines).

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 airplane.

Binding - What occurs when the friction at a joint is stronger than the linkage.

Biplane - An airplane with two sets of wings, one on top of the other. Historically the biplane configuration was used as it improves the bending stiffness of the wing that was otherwise difficult to achieve in early monoplane designs.

Boom - A wood tube or strip that extends rearward from the wings or from a short fuselage to support the tail surfaces.

Boundary Layer - The relative speed of airflow varies with the distance away from the surface. Right next to the surface there is no measurable relative motion. The thin boundary layer is slowed down by the presence of the surface.

Bracing wire - Bracing wires used to between wing planes. A solid steel wire used to support the structure of an airplane's wings or fuselage. Turnbuckles are often used to tension the wires. In the early days of aircraft design the biplane with bracing wires and struts was the strongest design. The disadvantage of bracing wires is drag. Although the wires may be small in diameter the drag of these is a significant percentage of the overall drag of the airframe.

Bulkhead - A former within the fuselage used as internal support for longerons, sheet sides, stringers and so on. Open triangulated structures are often used in the rear section of a fuselage to reduce weight and so allow the center of gravity to be achieved without adding ballast.

Bungee - An elastic chord used to launch gliders. A number of different types of bungee are available with different characteristics.

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 maximize the possible altitude and hence duration.

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Cabane - French for shed, it describes the center section area 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 airplane designed to fly with its tailplane in front of the wing, italso refers to a forward horizontal stabilizer. Some aircraft have canards in addition to a conventional horizontal stabilizer on the tail.

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.

Carburetor - The part of the engine that controls the engine speed. This is done by controlling the amount of air and fuel. The basic amount of fuel is normally controlled by the needle valve.

Caster - Swivel or rotate slightly. The tail wheel on tail draggers may be allowed to just caster. This has the added benefit of not feeding ground input back into the rudder servo mechanism.

Cellulose Dope - A nitrocellulose varnish like liquid used to shrink fabric onto a frame.

Centre of Gravity - The spot where the mass or weight of an airplane may be said to centre. The position of the centre of gravity of a model aircraft will determine how stable the aircraft is in flight. As the centre of gravity moves rearward (towards the tail) the aircraft will become more and more unstable. In models powered by internal combustion engines with fuel tanks situated in front of the centre of gravity it is important that the centre of gravity is set with the fuel tank empty. Otherwise, as the fuel is used the aircraft will become unstable. The centre of gravity may be assessed by balancing the aircraft on two finger tips placed either side of the fuselage.

Centre of Lift (CL) - The spot where the lift of a wing (or wings) is said to centre.

Centre of Pressure - The point on the upper surface of a wing relative to the chord where the lift can be said to center.

Chord - The width of a wing or tailplane from front (leading edge) to back (trailing edge).

Chord Line - A line from the front of an airfoil (the leading edge) to the trailing edge.

Chordwise Balance - A point at the center of lift of the blade, along the chord line. On a model it is advisable that the blade be balanced at this point as well as along the span.

Clevis - A sprung link connecting a control rod to the surface being controlled.

Composite - Generally describes a material composed of a stronger material embedded in a matrix. Concrete is a composite of gravel and sand embedded in cement, for example. In aircraft, composites are generally glass, boron, or carbon fibers woven as cloths or embedded directly as unidirectional or randomly oriented fibers in a matrix of epoxy or polyester resins.

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.

Contra-Rotating Propellers - Two propellers on the same axis rotating in opposite directions. It is a convenient method to increase power for a given propeller diameter.

Control Horn - An arm fastened to a control surface to which is connected the control rod.

Control Surfaces - Parts of an aircraft that are activated by the pilot or servos (in the case of a radio-controlled model) to change the airflow around the surfaces of the aircraft. The changes in airflow cause the aircraft to roll, pitch, or yaw.

Coriolis Effect - The tendency of a mass to increase or decrease its angular velocity when its radius of rotation is shortened or lengthened, respectively. In a helicopter, the coriolis effect of the main rotor blades is compensated for by the lead - lag hinges.

Coupe D’Hiver - The FAI’s F1G small free-flight rubber duration class, originated in France during World War 2.

Cowling - A name given to the aerodynamically efficient covering around or enclosing an engine.

Cyanoacrylate - A type of instant acting adhesive.

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Datum - A reference point, line, or plane from which measurements are taken.

Dead Stick - A term used to describe a power model making a glide approach after the engine has stopped.

Decals - Term used to describe a pre-printed set of letters or symbols that can be applied to a surface by transfer.

Delta - An aircraft with a wing of a triangular planform, the base of the triangle forms the trailing edge.

Dethermalizer - 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.

Diesel Engines - Diesel engines can offer a lot in terms of power to weight ratio and the ability to turn a large propeller.

Dihedral - The dihedral angle is the angle made between one wing and the horizontal, as viewed from the nose or tail of the aircraft. 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.

Dolly - A wheeled frame that a model sits on to effect a take-off. The dolly either remains on the ground or drops off almost immediately.

Dope -
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. When mounting engines be it IC or electric always try and incorporate some down and right thrust. This will vary with prop size, power and model type.

Downwind - In the circuit flying parallel with the runway in the opposite direction to take-off.

Drag - A force acting on an airplane resisting its acting on an aircraft in motion resisting the movement through the air.

Ducted Fan - 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 ducted fan is often used to simulate.

Dutch Roll - A side-to-side wallowing motion of a model, often caused by insufficient fin area.

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Elevator - The elevator is used on an airplane to control the pitch. Applying up-elevator will generate lift on the underside of the tailplane surface causing the tailplane to move downwards. The effect will be for the angle of attack of the will to be increased and hence generate more lift. The overall effect causing the airplane to climb. At low speeds the elevator will not work. During ground taxiing maneuvers the elevator may be used to stop the nose of the aircraft pitching into the ground, this will rely on the thrust from the aircraft being directed by the tailplane.

Elevons - 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.

Engine Cowling - A covering placed around an engine.

Engine Mounting - Isolating the engine mount using rubber can reduce the vibration levels on the airframe and so reduce noise levels. Also, if your radio gear is suffering from vibration rubber isolation can help. When mounting engines be it IC or electric always try and incorporate some down and right thrust. This will vary with prop size, power and model type. If using a commercial type of mount eg plastic type you can use self tapping type screws but really only up to .40 cu size engines with 10 x 6 props. I still like to use nuts and bolts though.

Engine Power to Weight Ratio - The power to weight ratio for a given engine size is a useful parameter to use when comparing aero engines.

Exhaust - The exhaust system on an internal combustion engine may be used to reduce noise and/or increase power.

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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 airplane, to reduce air resistance.

Fin - The fixed forward portion of the vertical tail surfaces.

Final Appraoch - The last phase of a flight when lined up with the runway during the landing approach.

Finishing - The detail in the finishing of the aircraft can be as important as
the fundamental design.

Firewall - A strong bulkhead immediately behind the engine on a powered airplane.

Flaps - Hinged surfaces attached to the trailing edge of a wing, either to increase maneuverability (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 airplanes).

Flaperons - A combination of ailerons and flaps. The differential movement has the same effect as ailerons and the collective movement the same effect as flaps.

Flare - The point during the landing approach in which the pilot gives an increased amount of up elevator to smooth the touchdown of the airplane. Ground effect may result in the aircraft remaining airborne for longer than expected.

Flight Box - A special box used to hold and transport all equipment used at the flying field. The more compartments the better, but ensure that the box is easy to clean as it will inevitably get covered in fuel and dirt.

Flight Pack - All of the radio equipment installed in the airplane: Receiver, Servos, Battery and Switch Harness.

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 airplane with a fuselage shaped like a boat for operation off water.

Flying Scale Model - A flyable miniature of a manned airplane.

Flying Tail - Horizontal tail surfaces which do not have a separate elevator. The whole surface moves as one to give pitch control.

Flying Wings - If you are looking for more information on flying wings try this excellent site:

Former - See: Bulkhead.

Forward Sweep Wing - The tips of the wing are forward of the leading edge at the root of the wing. There are many problems with this design, one being torsional stability resulting in flutter.

Free-Flight -

Freewheeler - A propeller with a special device that allows it to windmill after the rubber motor is unwound.

Frieze Type Aileron - When the aileron is down there is a very smooth flow over the top surface. However, when the aileron is up the bottom sticks out below the surface of the wing creating drag and balancing the drag created by the opposite aileron.

Fuselage - The body of an airplane.

Fuselage Construction - The fuselage of a model airplane that is intended to fly may be constructed in a number of ways depending on the required performance envelope of the model aircraft. A number of construction methods along with useful hints and tips are included here.

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Geodetic - A latticework or basket-weave construction.

Glazing - A great way to make your own glazing panels for model aircraft.

Glider - A highly efficient engineless airplane. Capable of flying for long periods in gently rising air currents (thermals).

Glitch - Momentary uncontrolled operation of control surfaces caused by electronic interference or equipment malfunction.

Glow Plug - The glow plug is the source of ignition in a "glow engine" hence the name.

Glue - A huge number of glues are used by model makers. A general guide to their
use is included here, but for more detailed uses, limitations and hazards the
individual manufacturers recommendations should be followed.

Ground Loop - A rapid circular rotation of a model on the ground, usually performed while taxiing 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.

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Hand-Launch - To start a model in flight by releasing it or throwing it from the hand.

High Lift Wing - A wing designed to produce a greater lifting force than a conventional wing. This is often achieved at the penalty of drag.

Hinge - There are many ways of constructing a hinge for the ailerons, rudder and elevator control surfaces. A number of the different methods are described here along with the pro's and con's of each.

Horizontal Stabilizer - The horizontal tail surface at the back of the fuselage (more commonly called an elevator) which provides aerodynamic pitch stability to the airplane.

Horsepower Loading - The ratio of gross wieght to horsepower, obtained by dividing the total weight by the engine&prime;s horsepower rating.

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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.

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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. A jig is normally used where a series of parts need to be assembled in the same way a number of times. However, when constructing a fuselage a jig may be used to ensure alignment from front (engine mounting position) to rear (tail surfaces mounting position).

Joints - Joint terminology and examples of good and bad joints.

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Laminar Flow Wing - A wing designed such that the air flow over it is laminar at zero to small angles of attack. In Laminar flow the adjacent layers of air flowing over the wing do not mix.

Landing Gear – term used to generally describe the wheels, struts, brakes, and other parts of the airplane used for movement on the ground, landings, and takeoffs. Landing gear can also be used as a general term for separate floats on a seaplane aircraft.

Landing Wire - Bracing wires which are designed to take the reverse loads on airplanes as a result of landing or inverted maneuvers. Landing wires are generally found on biplanes and some earlier monoplane aircraft with externally braced wings.

Lateral Axis - The axis extending through the centre of gravity of an aircraft and parallel to the wing surfaces.

Lateral Control - Ailerons give lateral control allowing the aircraft to be rotated around its lateral axis.

Leading Edge - The front or entering edge of a wing or tail.

Lift - The sum of all the aerodynamic forces acting on an aircraft at right angles to the flight path. When the aircraft is in steady level flight the lift is equal and opposite to the weight of the aircraft. Wings create lift.

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.

Longerons - The main fore-and-aft strips in a fuselage.

Low Wing - An aircraft with a single set of wings mounted at or near the bottom of the fuselage.

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Markings - General term used to describe the numbers, letters, and national symbols applied to aircraft for identification purposes.

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.

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 Centre of Gravity and nose, or Centre of Gravity and tail.

Monocoque - A form of fuselage construction with rounded exterior and very little internal structure in which the skin carries virtually all stresses.

Monoplane - Only one set of wings.

Motor Bearer - Hardwood strip mount for model airplane engines.

Motor Stick - A strong strip used to support the rubber motor; the body of stick-type models.

Muffler - See: <a href="e/exhaust.htm">Exhaust.

Mush - A nose-high, slow-speed flight attitude resulting from a slightly tail-heavy trim.

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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.

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Oleo - A shock absorbing system used in landing gear.

O.O.S. - Out of sight of the timekeeper.

Ornithopter - An airplane that flies by flapping its wings like a bird.

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Parasitic Drag - Resistance to a forward airplane movement caused by any non-lifting components of the airplane. The fixed undercarriage on most aircraft is one of the main causes of unwanted drag. Retractable landing gear will reduce area of drag to virtually zero.

Parasol - An airplane in which the wing is mounted above the fuselage on struts.

Pitch - The pitch of the aircraft whilst flying is controlled by the elevator.
However, if the line of thrust of the power unit and/or angle of attack of the
main wing are set incorrectly the pitch may also be a function of engine thrust.
Pitch is the theoretical distance travelled along the axis of rotation
of a propeller during one revolution.

Pitch Control - Provided by the elevators fitted to the tailplane.

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 airplane in climb and dive.

Planform - The outline of wing or tailplane when viewed from above.

Planking - Sheet-wood covering accomplished by gluing thin flat wood strips side by side on a fuselage.

Plywood - Sheet wood made by gluing 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.

Port Side - Right side of an airplane

Profile Drag - This is the sum of the form and skin friction drag calculated at zero incidence.

Propeller - An assembly of radially disposed blades with an airfoil shape that when rotated in air produce thrust.

Propeller Sizes - For a given engine size a range of propellers may be fitted. The tables here may give you a starting point and some alternatives.

Prop Pitch - Props are designated by these two numbers, for instance 10 - 6 (often pronounced 10 by 6). The first number is the prop's length, 10". The second number is the pitch or angle of the blades. The 6 represents the distance the propeller will move forward in one revolution, in this case 6".

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.

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Radial Engine - An engine design where the cylinders are designed symmetrically around a central crankshaft and hence radiate out.

Radial Mount - A molded plastic or metal mount which is fastened to the mounting lugs of an engine and then bolted directly to the engine bulkhead or firewall.

Radio Control -

Ramjet - A type of jet engine with very few moving parts which consists of a specially shaped tube open at both ends in which air is compressed purely from the forward speed. The addition of fuel and this being then ignited increases the volume of air. Note that ramjets only operate above certain speeds.

Rate of Roll - A measure of the speed with which an airplane rotate around its long axis, or roll. This is normally measured in degrees per second.

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 airplane.

Resonance - Resonance's occur when the source of vibration has a frequency that coincides with one of the natural frequencies of the structure.

Retractable Landing Gear

Rib Section - The cross-section shape of a wing, from leading to trailing edge.

Roll - A rotation of an aircraft around the longitudinal axis. This effect is produced by the ailerons.

Roll Control - Provided by the ailerons.

Root - The part of a wing where it meets the fuselage.

Rotary - An aircooled engine whose cylinders, arranged like the spokes of a wheel, rotate around a fixed crankshaft. The fuel is supplied to the engine through the crankshaft and the engine normally exhausts straight out the top of the cylinder. This arrangement was used with early engines as the mass of the engine was used as the flywheel allowing the engine to run smoothly.

Rudder - The moving part of the vertical tail surface of an airplane which provides yaw control.

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Sailplane - See glider.

Scale - The debate as to what is scale and what is not will go on and on.

Service Ceiling - The altitude above sea level beyond which an airplane can no longer climb more than 30 m (100 ft) per minute.

Shear Web -

Side Slipping - The direction of flight is at an angle to the fore aft axis of the aircraft.

Side Thrust - Offsetting the propeller thrust line, so there is a slight sideways pull.

Single-Surface Wing - A wing formed from a single sheet of balsa, or one that has a framework covered only on the top.

Slats - Slats are used on the leading edge of a wing to improve lift. They help the formation of a smooth boundary layer over the leading edge allowing the wing to operate at a higher angle of attack before separation occurs.

Slipstream - The column of air pushed rearward by a rotating propeller; it always moves faster than the airplane itself.

Spars - Spanwise load-carrying members of a wing or tail.

Spin - The rapid rotation of an aircraft after it has stalled. In order to recover the aircraft it is necessary to first increase the airspeed so that the flying surfaces are no longer stalled.

Spiral Dive - An ever-tightening downward corkscrew flying path.

Spiral Stability - The characteristic of an airplane that permits high-speed banked turns without diving to the ground.

Spinner - The nose cone which covers the hub of the propeller. Check that the spinner does not touch the propeller blades as this may result in the propeller blades wearing and possibly failing. Remember a large spinner will result in less effective propeller area and a reduction in engine cooling.

Spoilers - Controls which can be deployed into the airflow to ‘spoil’ the lift. Usually found on gliders and used to aid landing.

Stabilizer - A surface that is used to stabilize the aircraft during normal flight e.g. the tail fin and tailplane. Other designs such as a V-tail may be used to provide both pitch and yaw stability.

Stability - The tendency of an airplane to return to level flight, after having been disturbed by an upsetting force.

Stagger - On a biplane, this term is used to describe the distance the distance between the top wing or wings and the bottom wing when looking down on the airraft.

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.

Starboard - Left side of the airplane

Stick - The operating arm on a transmitter which is moved to make the control surface move.

Stitching - A step by step article on creating simulated stitching effect on fabric.

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 airplane for the least possible air drag; usually rounded in front, pointed at the rear.

Stressed Skin - An outer covering used on wings and fuselages, designed to carry the tension and compression forces encountered in flight.

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.

Swept Wing - The leading and trailing edges of a wing are angled backwards to reduce drag at high speeds.

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Tab - A small adjustable surface on wing or tail surfaces, used to make small trim changes.
See also: Trim Tab.

Tachometer - An optical sensor designed specifically to count light impulses through a turning propeller and read out the engine rpm (revolutions per minute). This is useful when tuning an engine or matching the throttle and tune on multi-engined aircraft.

Tail - The surfaces (tailplane and fin) at the rear of a conventional airplane fuselage

T-Tail - Arrangement where the tailplane is mounted on top of the fin.

Taildragger - An aircraft which has an landing gear 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.


Tailskid - A fixed angular fixture use to support the tail end of an aircraft on the ground instead of a wheel.

Tandem Winged - An airplane with wings of similar size mounted one in front of the other, on pretty much the same level.

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.

Three Point Landing - With a tail dragger there is an art in landing with all three wheels touching the ground at the same time.

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 airplane.

Timer - A lightweight clockwork or electronic device fitted to free-flight aircraft to operate in-flight systems and to control the dethermalizer.

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.

Tip Stall - The outboard end of one wing stops developing lift, causing the plane to roll suddenly in the direction of the stalled wing. This situation is not fun when you are only a few feet off the runway trying to land.

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 airplane 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 maneuver that uses the torque reaction to accelerate the rate of roll of an aircraft.

Touch-And-Go - Landing and taking off without a pause. Useful to practice when learning to fly.

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.

Trailing Edge - The rear edge of a wing or tail surface.

Trainers - There are a number of requirements for the basic trainer aircraft. Points to consider whether you are designing, constructing or choosing are outlined along with some of the most popular kits on the market.

Tricycle Landing Gear - 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.

<a name="trim-tab">Trim Tab - A small auxiliary surface hinged on an airplane's control surfaces, used to bring it into balance or trim. This may be as simple as a small metal tab on the trailing edge of an elevator that is set to trim the aircraft for horizontal flight.

Twin Engine - There are a number of variations on the twin engined aircraft. An example given here uses a single engine and a flexible drive to turn two propellers.

Two-Stroke Engine - The two stroke engine has been the main stay of powered model aircraft for a number of years due to the high power to weight ratio. The main downfall of the two-stroke engine is the high fuel consumption. The basic construction, operation and general notes on starting, running and maintaining are all included within this section.

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Undercamber - The concave curve on the underside of some airfoils.

Undercarriage – British terminology for landing gear.

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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.

Variable Incidence Tailplane - 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 - Air from the high pressure region under the wing flows to the low pressure region above the wing when generating lift, the result are vortices. This reduces the effective lifting area of the wing and generates drag. If the wing span was very long the loss due to this flow from bottom to top would be very low and the induced drag very low. This is why high aspect ratio wings are used where low drag and high lift is required e.g. gliders.

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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. Washout inherently makes the aircraft more stable.

Waterslide Decals - Markings come in many different forms and are normally provided with the kit.

Wheel Spats - Designed to reduce the drag of fixed undercarriages by providing an aerodynamic shroud over the top section of the wheels.

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 Construction - The wing of a model airplane that is intended to fly may be constructed in a number of ways depending on the required performance envelope of the model aircraft.

Wing Covering - There are a number of ways a model aircraft wing can be constructed and finished to produce a durable structure (this is especially important in the case of model aircraft powered by internal combustion engines).

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.

Wing Section - The chord-wise cross section of a wing. Since the first days of flight wing sections have been continually changing and optimized for different aspects: lift, drag, low speed, high speed, strength.....

Wing Warping - The earliest form of roll control was produced by warping the whole wing. Raising the trailing edge of the right hand wing and lowering the trailing edge of the left hand wing will result in the aircraft rolling to the right.

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Yaw - A ‘side-to-side’ rotation of an aircraft around the vertical axis. This effect is produced by the rudder.

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