Glossary

A glossary of terms designed to help beginners deal with the jargon of the modelling industry. Click on a letter to go directly to a specific section.

Other

A.A.C - Describes an engine with an Aluminium piston running in an Aluminium cylinder liner which has been Chrome plated.

A.B.C - Describes an engine with an Aluminium piston running in a Brass cylinder liner which has been Chrome plated.

A.B.S - A form of plastic most commonly used for non-structural items such as areas of trim and cowlings etc.

Aerobatics - Performing stunts with an aircraft such as loops and rolls etc.

Aerodynamics - The science that defines how and why aircraft fly.

Aeromodelling - The hobby of building and / or flying model aircraft.

Ailerons - Hinged flaps on the rear edge of an aeroplane wing. The ailerons move in opposite directions to give roll control of the aeroplane. Aileron is also used to describe the roll control of a helicopter. Technically this is incorrect because a helicopter does not have ailerons and so this should be described as cyclic pitch roll control but most people call it aileron for simplicity.

Air-brakes - Describes plates that can be deployed to slow an aeroplane down. Air-brakes are most commonly used on gliders and jets. They are used to steepen a landing approach to allow landing within a shorter distance.

Airframe - A term which describes the whole structural element that an aircraft is comprised of.

Airspeed - The speed of a model relative to the air in which it is flying. A model flying at 50mph relative to the ground while heading into a 20mph wind has an airspeed of 70mph. A model flying at 50mph relative to the ground while heading away from a 20mph wind has an airspeed of just 30mph. This is important on the downwind leg of a circuit when an aeroplane can get dangerously close to its stalling speed while appearing to be traveling quickly to the pilot standing on the ground. For helicopter flyers it is important because a helicopter flying at 20mph relative to the ground while heading away from a 30mph wind will in effect be flying backwards and the tail will try to spin around and 'weathercock' in line with the wind.

Antenna (aerial) - The parts of a radio system that transmit and receive radio waves.

A.M (Amplitude Modulation) - A form of radio transmission. Few radio control systems work on A.M these days.

Anhedral - Describes the angle of the wings relative to the body of an aeroplane when looking from the front or rear. Anhedral angle is where the tips of the wings are lower than the center section of the wing. Models with anhedral tend to be less stable but more manoeuverable than models without anhedral.

AoA (Angle of Attack) - Describes the angle from the horizontal at which a wing profile travels through the air.

A.R.T.F (Almost Ready To Fly) - This is a type of model kit where the bulk of the work is done for the modeller An ARTF kit comes with all major assemblies built and covered as opposed to a traditional model kit where the majority of the model has to be built from timber and plastic components and covered by the modeller

A.T.V (Adjustable Travel Volume) - An adjustment in a transmitter that sets the overall movement range of a servo.

A.V.C.S (Angular Vector Control System) - Another name for the heading hold feature of a gyro - refer to gyro for details of heading hold.

Avionics - A term which describes the on-board electronic gadgets which make models controllable, namely servos, receivers, switches, batteries, gyros, governors etc.

Auto-rotation - Describes the flight of a helicopter when the engine has stopped i.e. an auto-rotation is a helicopter version of a glide. A helicopter can glide very well as long as it has height to spare. By putting the blades into negative pitch, the rotor system is forced to spin faster as the machine descends and this kinetic energy can be used to land the helicopter safely by putting the blades back into positive pitch. The timing of this is crucial as the inertia stored in the head is quickly exhausted.

Autogyro - An aircraft which looks like a small helicopter but cannot actually hover like a helicopter. The rotor blades of an autogyro are not directly driven by the engine whereas in a helicopter they are. An autogyro needs forward airspeed over the rotors to make them spin, thereby creating lift. A helicopter needs no forward airspeed to spin its rotors. Although autogyros cannot hover (except in a strong wind) they do have very short take off and landing abilities compared to an aeroplane.

Barrel roll - Aerobatic manoeuver where the model rolls around the outside of an imaginary barrel while travelling forwards, thereby following a corkscrew path.

Batteries - Refer to cells.

Battery checker - A small electronic gadget that plugs into the radio system and gives a readout of the energy left in the battery pack. Battery checkers vary in price and complexity but no modeller should be without one.

B.E.C (Battery Eliminator Circuit) - Used in electric powered aircraft, the B.E.C allows the radio to run safely off the same battery as the motor. The B.E.C prevents the motor from draining all of the battery power. As the power decreases the B.E.C turns the motor off to allow a safe period of time for the pilot to land the model.

Blades - Helicopters have wings, its just that they are long, narrow and spin around on a shaft hence helicopters are often referred to as rotary wing aircraft. Model helicopter blades can be made from various materials and vary in price accordingly. Basic budget and training helicopters tend to be supplied with timber blades. Timber blades are perfectly acceptable for learning purposes because they are unlikely to be over-stressed in the learning stages and they are cheap to replace if they get damaged. For anything more advanced, composite or fiberglass blades are the better option. They are more expensive but they are almost always better balanced, give far superior performance and can handle much higher flight loads.

Bling - The replacement of standard parts of a model with upgrades for either functional or aesthetic purposes. This is most common on helicopters with many models having bling / upgrade parts available. Many of these parts enhance the performance of the model but many do little but improve the looks. A lot of money can be spent on bling that achieves very little, although beauty is in the eye of the beholder.

Boom - The rear part of a helicopter between the cockpit (pod) and the tail.

Brushed motor - Describes the traditional internal build of an electric motor. Brushed motors are still used for electric flight but are rapidly being phased out as brushless motors became more affordable. The sole advantage of brushed motors is their low cost. In every other respect they are outperformed by brushless motors. Note that a brushed motor requires a standard speed controller or a switch.

Brushless motor - Describes the internal build of the best motors for electric powered flight. Brushless motors are superior to brushed motors because when powered by the same battery they are far more efficient and able to handle much higher amperages. This gives the impression that they are more powerful than brushed motors which is not necessarily the case. They are much better at converting the power available from a given capacity of battery. This being the case, a brushless motor may actually drain the battery more quickly than a brushed motor but this tends not to bear out in reality as the gain in efficiency offsets the increased rate of consumption. Note that a brushless motor requires a brushless speed controller.

Buddy box - A method of teaching where two transmitters are linked together with a cable. The instructor has overall control but can push a button to transfer control to the pupil. If the pupil gets into trouble during the flight, the instructor simply releases the button to regain control and recover the model before it is damaged.

Bungee launch - A length of bungee line used to launch a glider from a site where it would have no other way of gaining altitude.

Bunt - Aerobatic manoeuver where the nose is continuously lowered such that the aircraft flies a circular path through the inverted and back to level flight i.e. a loop but down instead of up.

Camshaft - Internal part of the engine that drives the fuel inlet and exhaust outlet valves.

Canard - Some aeroplanes have the 'tailplane' at the front of the aeroplane instead of the back. When this is the case, the surface is referred to as a canard foreplane. The thinking behind this design is safety. Theoretically the main wing cannot be stalled as the canard foreplane will always stall first and an aeroplane that cannot be stalled should be safer than one that can.

Canopy - The cockpit glazing of an aircraft.

Carbon - Describes the carbon fibre composite technology used for many up-market helicopter parts and aeroplane add-ons; also used in helicopter blades.

Carburettor - Part of an engine. The Carburettor atomises the raw fuel when it arrives from the fuel tank and controls the ratio of fuel to air in the vapour going into the engine. Setting this mixture correctly is a critical aspect of model engine usage. The carburettor usually has a throttle system that allows the speed of the engine to be controlled as well.

C of G (Centre of Gravity) - This is the point of balance along the length of an aeroplane or helicopter. Think of it like a seesaw, it is the point of balance where the nose is level and in equilibrium. This is a critical point on all aeroplanes as a center of gravity which is too far rearward will make the aeroplane dangerously unstable and too far forward will make it unresponsive in pitch control.

Cell - Component part of a battery. Model technology uses three types of rechargeable battery - NiCad (Nickel Cadmium), NiMH (Nickel Metal Hydride) and LiPo (Lithium Polymer). NiCads are most commonly used for powering radio control units and are sometimes used as main power batteries for electric aircraft but they are heavy and deliver the worst energy density of any of these batteries i.e. they are very heavy in relation to the power they can actually deliver. NiMHs are commonly used for powering radios and as main power batteries for electric aircraft. They have a better energy density than NiCads, though not as good as LiPos. Their advantage is that they give a useful performance at a reasonable price and are less temperamental than LiPo cells. LiPos are almost always used as main power batteries for electric aircraft. They have a very high energy density and have revolutionised electric model flight. They demand respect in their handling though as abuse through ignorance or impatience will lead to the cells being permanently damaged and possibly exploding! Talk to a reputable dealer for further advice when buying LiPos. Refer to balancer.

Channel - Describes a dedicated frequency band that a radio control transmitter / receiver broadcast and receive on. This is very important as two models cannot fly at the same time if they are on the same channel i.e. the same frequency - refer to the FAQ page for a frequency chart.

Chaos - A very advanced helicopter aerobatic manoeuver where the machine continuously flips while performing pirouettes.

Chicken stick - A stick used to flip a propellor when starting an engine.

Chord - Another name for the width of a wing.

Collective pitch - The primary lift control of a helicopter. Collective pitch is when the rotor blades are tilted in unison either up or down to give more or less lift.

Collet - Describes a small metal 'donut' shaped object with securing screws projecting from the perimeter into the center hole. Collets are typically used on the ends of axles to stop wheels coming off and are heavily used in helicopter mechanics to retain gears on shafts.

Combat - A common game with model aeroplanes is to tie a streamer to the back of each model. The aim is to cut each other's streamers with the propeller and the pilot with the longest streamer remaining is the winner. This game is not conducive to a model's longevity!

Computer radio - Describes a radio transmitter with a small onboard computer system that provides many useful features and makes it much easier to set a model up. The phrase 'computer radio' should not deter those who don't understand computers from buying a computer radio system as no specialist knowledge is needed to use it and it makes life so much easier.

Con-rod - Short for connecting rod. This is an internal part of an engine connecting the piston to the crank-shaft.

Control Line - Flying model aircraft which are tethered by long wires. The wires are fixed to a hand grip which allows control of the elevator and sometimes the throttle as well. The model flies around the pilot, sometimes at great speed and not getting dizzy is part of the challenge.

Cowling - Nonstructural parts of the airframe that cover the engine bay for aesthetic and aerodynamic purposes - commonly made of plastic or fiberglass.

Crankshaft - Internal part of an engine that turns the linear motion of the piston into rotary motion of the output shaft.

Crankcase - Lower part of an engine that contains the crankshaft.

Crow-brakes - A form of air-brake.

Crystals - Small plug-in modules for radio transmitters and receivers that determine the frequency on which they communicate.

Cyano-acrylate - The technical name for Super Glue type adhesives.

Cyclic pitch - The primary directional controls of a helicopter. Cyclic pitch is when the rotor blades are tilted in opposition to make the helicopter fly either backwards or forwards (technically this is fore / aft cyclic but is often referred to as elevator control) or roll left or right (technically this roll cyclic but is often referred to as aileron control).

Cylinder - Main part of an engine where the fuel is drawn in, compressed, burnt and expelled.

Dead stick - When the engine stops unexpectedly during a flight.

Decal - Decorative sticker or trim.

Delta-peak - This is a function of fast chargers for NiCads and NiMHs that detects when they have taken as much charge as they can and stops charging them for safety.

Dihedral - Describes the angle of the wings relative to the body of an aeroplane when looking from the front or rear. Dihedral angle is where the tips of the wings are higher than the center section of the wing. Models with dihedral tend to be more stable than those without and demonstrate a limited ability to self level hence most trainers have dihedral built in.

Diesel - Many model engines work on the diesel principle of ignition (i.e. ignition by compression of the fuel mixture) but model 'diesel' fuel is actually kerosene and ether based.

Drag - One of the four primary forces on an aircraft. Drag is the effect of friction on an aircraft from the air when in flight and from the ground when taking off. Click HERE for an aeroplane forces diagram and HERE for a helicopter forces diagram.

Drop a wing - Another way to describe a tip stall.

Ducted fan - A form of propulsion designed to mimic jet propulsion. Before model jet turbines were a reality, models of jet aircraft were powered by a ducted fan, basically a multi-bladed fan impeller running at high speed within a tube and powered by a high revving two stroke glow engine. As model jet turbine engines became more readily available, ducted fans became less popular although they are still available and still a lot more affordable than their turbine cousins. Ducted fans are gaining in popularity in the electric sector following the technological leaps made by brushless motors and LiPo batteries.

Dual rates - A function of a radio transmitter allowing controls to be made more or less responsive at the flick of a switch.

Elevator - Hinged flaps at the rear of the tail-plane which give control of the aeroplane in pitch i.e. up and down. Elevator is also used to describe the fore / aft control of a helicopter. Technically this is incorrect because a helicopter does not have elevators and so this should be described as fore / aft cyclic pitch control but most people call it elevator for simplicity.

Elevon - Elevons occur on aeroplanes that do not have a tailplane i.e. flying wings such as the Stealth Bomber and deltas e.g. Concorde and the Vulcan bomber. The hinged flaps at the rear of the wings achieve both ELEVator and ailerON control hence the name. They move together for elevator control and in opposition for aileron control.

Epoxy resin - A two part adhesive available in different setting rates from five minutes to 24 hours.

Failsafe - A feature of P.C.M radio control systems whereby the controls can be set to default to a specific position in the event that interference occurs or the transmission signal is lost. A common usage is to set the throttle to idle or cut the engine completely to stop a model getting away should the control signal be lost.

Field box - Toolbox for assorted modelling bit and bobs. A field box is almost a personal statement varying from minimalist but impractical to the back-breaking, everything needed to re-build a car variety.

Fin - The vertical flying surface at the rear of an aeroplane. The fin is the fixed part; the flap attached to it is the rudder.

Fixed wing - Another term for aeroplane flight.

Flaps - Hinged flaps at the trailing edge of an aeroplane wing which allow the wing to fly more slowly without stalling thus allowing the aeroplane to take off in a shorter distance and land more slowly or on a shorter air strip. Flaps are most commonly used on scale models.

Flapperons - Flapperons are used to save having to split the trailing edge wing area into separate aileron and flap components. Instead, the ailerons are moved up or down in unison to give FLAP control and are moved in opposite directions to give ailERON control hence the name.

Flare - Raising the nose of an aircraft just before it touches down on landing to reduce speed and soften the landing impact. Also describes the final bleeding off of speed on a helicopter transition from the circuit to the hover.

Flybar - Part of a helicopter rotor head which provides stability and control inputs.

F.M (Frequency Modulation) - A form of radio transmission. Most radio control systems work on F.M these days.

Foamie - Describes an A.R.T.F model constructed mainly of foam.

Four stroke engine - A four stroke engine takes four complete strokes of the piston in the cylinder to complete a full cycle (two complete revolutions of the propellor) - stroke 1, exhaust valve closes, fuel valve opens, piston goes from top to bottom, fuel / air mixture is drawn in to the cylinder - stroke 2, fuel valve closes, piston goes from bottom to top, fuel / air mixture is compressed - stroke 3, fuel / air mixture is ignited and explodes forcing the piston from top to bottom - stroke 4, exhaust valve opens, piston goes from bottom to top forcing the spent mixture out of the exhaust valve. Also, refer to two-stroke.

Free flight - The hobby of flying model aircraft which, once off the ground, have no direct control input from the owner i.e. no radio control. Free flight models mostly have pre-set controls that perform their function at programmed intervals but there is no other control from the ground.

Frequency - Refer to channel and to FAQs page for details of frequencies.

Fuel - Glow engines run on a mixture of methanol and oil. Traditionally the oil was castor oil but modern synthetic oils offer many advantages and the issue of which is best tends to be hotly debated. Refer to the engine manufacturers instructions if in doubt. Typically the ratio will be 80% methanol to 20% oil for a 2-stroke engine and 83-85% methanol to 15-17% oil for a 4-stroke engine. This is referred to as a straight mix because it contains no ignition enhancers. Many modellers prefer to use a fuel with nitro methane added. 5% nitro gives improved starting, idling and throttling but little added power. For higher performance, particularly in helicopters, it is not uncommon to run up to 30% nitro but this is expensive and unnecessary at club level and may require alterations to the engine. Model 'diesel' engines are not fueled with the sort of diesel you buy from Esso. Model diesel is based on ether and kerosene, it's just that the engines work on the diesel principle of compression ignition. The use of petrol engines is on the increase in modeling because the fuel is cheaper, the engines more reliable and there is a lot less oily mess to clean off the model. This is because the oil ratio can be as low as 50:1 in many model petrol engines as opposed to 4:1 for the glow engine. The two main reasons why a glow engine needs so much oil in the fuel are: 1) the un-burnt oil carries heat away from the engine as it exits the exhaust and 2) because the con-rod is fitted with plain bush bearings as opposed to the roller race bearings in a petrol engine con-rod.

Fuselage - Describes the body of an aeroplane or the body shell of a helicopter.

Glide - Describes the flight of an aeroplane when not under power.

Glider - Describes an aeroplane which is not powered. Gliders can be launched either by bungee, aerotow or hand launched from a slope. Whichever system is used, the idea is to gain and maintain height using natural sources of lift, either slope lift or thermal lift.

Glitch - When a model is thrown off course by radio interference.

Glow Plug - The majority of model aircraft engines in use today are glow plug engines, which run on a mixture of methanol, nitro methane and oil. A glow plug engine is a form of low compression diesel engine with a constant source of ignition. To start the engine a battery is connected to make the plug element glow and provide ignition. Once the engine is running, the battery is disconnected, but the plug continues to glow due to a catalytic reaction between the platinum element and the methanol in the fuel.

Governor - A governor is an electronic device used on a helicopter to maintain a constant rotor head speed by automatically adjusting the engine throttle to provide more or less power in response to the demands of the pilot. Governors are only required for advanced 3D aerobatic flight and are not necessary for beginners or intermediate pilots.

Gravity - One of the four primary forces on an aircraft. Gravity pulls the aircraft towards the ground. Lift and skill stop it hitting it too hard! Click HERE for an aeroplane forces diagram and HERE for a helicopter forces diagram.

Ground loop - Some aeroplanes are very hard to steer in a straight line when trying to take off. A ground loop is where the model fails so badly to go in a straight line that it turns right round in a circle.

Gyro - A gyro is an electronic device that corrects an unstable flight characteristic of an aircraft. Gyros are most commonly used on helicopters to make the yaw (often referred to as rudder) control manageable. When model helicopters first arrived on the market in the 1970s, gyros were not common and the pilot workload was immense in trying to control the tail without any electronic assistance. Over the years, gyro technology has improved out of all recognition and today's gyros are solid state and amazingly efficient, giving precision control of one of the hardest helicopter controls to master. Beginners should not be fooled into buying the most expensive gyro on the market as it can actually hinder mastery of the tail control. A standard gyro with a reasonably fast servo is all that is needed.
Gyros are also used in aeroplanes to smooth out undesirable and unpleasant flight characteristics.

Hand-launch - Describes the launch of an aeroplane by throwing it into the air.

Head - Top part of the cylinder of an engine which features either a glow plug, spark plug or tommy bar.

Heading hold - Describes an additional flight mode of a gyro which locks the nose of the helicopter onto one heading thereby allowing ambitious aerobatics to be performed without the heading of the helicopter wandering off course.

High wing - An aeroplane with its wings located at the top of the fuselage. High wing aeroplanes are generally more stable than low wing aeroplanes, hence most trainers are high wingers.

Horns - Describes the lever arms affixed to a servo shaft to allow the connection of push-rods or control cables.

Idle - Describes an engine which is running slowly or 'ticking over'.

Idle-up - Describes a selectable flight mode which allows a helicopter to fly upside down. Helicopters have two functions assigned to the throttle stick, throttle and collective pitch. To fly upside down you need to pull the stick back, thereby reducing the collective pitch of the rotor blades to the point that they are at a negative pitch angle. In the normal flight mode, pulling the stick back would also cause the engine speed to reduce to idle so an idle-up mode is used where the engine speeds up again below the throttle stick mid point, thus inverted flight can be sustained.

Incidence - Describes the angles at which parts of an aircraft relate to each other e.g. some aircraft require their wings and tailplanes to be set an angle of a couple of degrees nose up relative to the centerline of the fuselage.

Immelmann - Describes an aerobatic manoeuver consisting of a half loop followed by a half roll - named after its inventor, Max Immelmann.

In-runner - Describes a brushless electric motor where the outer can of the motor is stationary and the core of the motor spins with the shaft.

Interference (radio) - When the signal between a radio transmitter and receiver is corrupted by other radio waves. This can cause the model to behave erratically or crash.

Inverted - Describes a model which is flying upside down.

Jesus bolt - Used to describe situations where a single bolt holds a critical element such as the bolt retaining a helicopter rotor head to the mainshaft.

Jet turbine - Describes a model gas turbine engine. Model jet engines are a practical power source for both aeroplanes and helicopters and are commonplace these days, although too expensive for the average modeller Typically they are started on a gas mixture of propane and / or butane which is switched over to kerosene once the engine is running. Many model turbine engines feature fully automated computerised control systems for maximum performance and safety.

Kicker - Describes an accelerator for making adhesives set more quickly, particularly cyano-acrylates.

Knife-edge - An aerobatic manoeuver where the model is made to fly on its side for an extended period.

Lift - One of the four primary forces on an aircraft. A wing generates lift through a combination of the correct aerofoil profile traveling through the air at sufficient speed and at a suitable angle of attack. This combination creates a smooth, laminar flow of air over the wing and the wing shape leads to a pressure differential, with high pressure being generated below the wing and low pressure above. If the angle of attack becomes too great or the speed decreases too much the airflow becomes turbulent and breaks away from the wing. The wing stalls and lift ceases to be generated. Click HERE for an aeroplane forces diagram and HERE for a helicopter forces diagram.

LiPo - Refer to Cells.

LiPo balancer - A small electronic gadget that plugs into the maintenance lead of a LiPo battery pack. The balancer makes sure that all of the cells in a lithium polymer pack are charged to the same level as an unbalanced pack is an explosion hazard. Always refer to the product instructions for the safe handling of LiPo batteries. Refer to cells for further details.

Loop - Aerobatic manoeuver where the nose is continuously raised such that the aircraft flies a circular path through the inverted and back to level flight.

Low wing - An aeroplane with its wings located at the bottom of the fuselage. Low wing aeroplanes are generally less stable but more manoeuverable than high wing aeroplanes, hence many aerobatic models are low wingers.

Memories - Computer radio transmitters allow the user to adjust a vast number of parameters for the control and trimming of a model aircraft. In order to avoid having to repeatedly change these settings for each model, the transmitter allows various model setups to be saved to dedicated memories that can be selected when the user wants to fly a different model.

Methanol - Refer to Fuel.

Mid wing - An aeroplane with its wings located at the middle of the fuselage. Mid wing aeroplanes generally give a good compromise between stability and manoeuverability, hence many sport models are mid wingers.

Mode 1 and 2 - Describes the configuration of the control sticks on a transmitter. Mode 1 is where the rudder and elevator are on the left hand stick with the aileron and throttle on the right hand stick. Mode 2 is where the rudder and throttle are on the left hand stick with the aileron and elevator on the right hand stick. These are the most common configurations but there are also modes 3 and 4 available. Please refer to radio manufacturers for details.

Motor - Refer to brushed and brushless motors.

Motor mount - Component part of a model to which the engine or motor is mounted. Small to mid size aeroplanes usually feature mounts made of nylon or glass reinforced plastic. Larger aeroplanes often feature metal alloy mounts on rubber vibration isolation mountings. Helicopter engine mounts are usually a strength giving structural part of the airframe.

Muffler - Refer to silencer.

NiCad - Refer to Cells.

NiMH - Refer to Cells.

Nitro - Refer to Fuel.

Out-runner - Describes a brushless electric motor where the core of the motor stays stationary and the outer can spins with the shaft.

Paddle - Part of the helicopter rotor head. Paddles are mounted on the ends of the flybar and perform two functions. They are aerofoil shaped and when tilted give control inputs to the flybar. The mass of the paddles gives a stabilization effect. Heavier paddles make a helicopter more stable, lighter paddles make a helicopter more manoeuverable.

Park-flyer - Describes small, lightweight models that can be safely flown in very small areas and do not require dedicated flying sites.

P.C.M (Pulse Code Modulation) - Technical description for a digital radio control system. P.C.M systems are more expensive but give better interference rejection and allow the use of a failsafe system.

Peg-board - A board with radio frequency numbers displayed; used to avoid crashes due to conflicting radio signals. Pilots either put a peg on their number to show that it is in use (peg on system) or take a peg off to show that it is in use (peg off system). The two systems are mutually exclusive. The Forest Radio Model Club uses the peg on system.

Port - The left hand side of an aircraft when viewing it from behind.

P.P.M (Pulse Position Modulation) - Technical description for an analogue radio control system. P.P.M systems are less expensive than P.C.M systems and so are more commonly used but they are more susceptible to interference and do not allow the use of a failsafe system.

Propellor - A fan attached to the engine to convert rotary motion of the crankshaft into thrust to move the aeroplane. Propellors exist in many different forms. Most commonly they have two blades but control line speed models often use single blade props (with a counter weight) for more efficiency and scale models often use multi-blade props to look more like the real thing. All model engines are designed to run anti-clockwise when viewed from the front (although some engines can run backwards) and so most propellors are designed accordingly. For aeroplanes that are designed with engines at the back, specialised pusher props are also available.

Prop balancer - A device that allows the user to correct any imbalance in the weights of opposed propellor blades thereby decreasing vibration.

Pulse jet - A crude form of jet engine most notably used on buzz bombs in WWII. Pulse jets are still used on fast jet models and are most commonly seen at airshows due to their spectacular noise and speed. Pulse jets seem to be getting less popular as gas turbines become more affordable and more user friendly.

TBC

Receiver - The part of the onboard radio system that takes the control signals from the transmitter and moves the servos accordingly.

Retracts - Describes an undercarriage that can be folded away after take-off. Retracts are powered either by motors or pneumatics.

R.O.G (Rise Off Ground) - Describes a normal take off.

Roll - When the model rotates around the long nose to tail axis. When the model stays on this axis the roll is said to be axial. When the model 'corkscrews' around this axis the roll is a barrel roll.

Rotary wing - Another term for helicopter flight. The blades of a helicopter are rotary wings.

R.T.F (Ready To Fly) - This is a type of model where all of the work is done for the modeller. Usually all you have to do is charge the battery.

Rudder - Hinged flap at the rear of the vertical fin which gives control of the aeroplane in yaw i.e. left and right. Rudder is also used to describe the yaw control of a helicopter. Technically this is incorrect because a helicopter does not have a rudder and so this should be described as left / right yaw control but most people call it rudder for simplicity.

Rx - Short for receiver.

Servo - A component of the radio system. Servos are the small motorised control units that move the control elements of model aircraft i.e. servos control the ailerons, elevators, rudder, throttle, flaps and undercarriage of an aeroplane or the cyclic pitch, collective pitch, throttle, yaw and undercarriage of a helicopter. Basic training aeroplanes can get away with using basic, cheap servos. Basic training helicopters must use reasonable ball-raced servos. High performance aeroplanes and helicopters must use high performance servos, fit for the rigours intended.

Shock Flyer - Describes very lightweight but highly aerobatic indoor models. Shock Flyer is a trade name that is lazily used in the same way that Hoover is a trade name we use to describe all vacuum cleaners.

Shot down - When someone switches on a transmitter using the same frequency as someone already flying causing the model to crash through conflicting radio signals. Modellers use a pegboard to avoid this.

Silencer - Part of the exhaust system of a model engine - A large chamber allowing the spent fuel / air mixture to expand as it exits the engine, thereby dissipating its energy and making it quieter.

Simulator - A computer flight simulator designed to mimic the behaviour of model aeroplanes and helicopters. Simulators usually allow the user to operate the programme with an actual radio transmitter for absolute realism.

Skids - The undercarriage bars of a helicopter.

Slope lift - Slope lift is generated when wind driven air meets a physical obstacle like a hill. The air is forced up the slope and a glider flown into this rising air will also rise assuming the lift is strong enough and the model is light enough.

Solarfilm / Solartex - A pre-coloured plastic sheet used for covering / finishing model aeroplanes. Solarfilm has a heat activated adhesive backing. To apply it you simply lay it on the model and apply a warm iron to it. The heat causes the adhesive to activate so it sticks to the model and the heat also causes it to shrink thereby getting rid of the wrinkles. Because it is pre-coloured, there is no painting necessary and it is also fuel proof. Solartex is a heavier version of Solarfilm and gives more of an impression of a fabric finish. As a result, Solartex is most commonly used on scale models or where a stronger covering is needed.

Speed controller - An electronic device that takes power from a battery and delivers it to a motor at a rate governed by the position of the throttle stick. Essentially it gives the pilot throttle control of the motor. Speed controllers exist in many different forms. Brushed motors require brushed motor controllers; brushless motors require brushless motor controllers. The controller must be able to cope with the voltage of the battery and the amperages that the motor will be drawing. It is essential to get the correct type of controller for the motor and battery being used - refer to a reputable dealer for advice.

Spoilers - Plates that are projected from a wing surface to reduce speed and increase drag. They are used to steepen a landing approach to allow landing within a shorter distance.

Spin - A true spin is where an aeroplane rotates rapidly, losing height with little or no forward airspeed and with the wing in a stalled condition. Spins can be induced deliberately as an aerobatic manoeuver or can occur through instability. In the latter instance it can be impossible to break out of them but this is rare.

Stall - A stall occurs when a wing is slowed down so much relative to its angle of attack that the air breaks away from it forming a turbulent layer. The result is that the wing ceases to generate lift and the model falls.

Stall-turn - Aerobatic manoeuver where the model is flown vertically upwards until it stops at which point full rudder is applied causing the model to rotate quickly until it points vertically down. The model is allowed to build up speed before pulling back to level flight.

Starboard - The right hand side of an aircraft when viewing it from behind.

Starter - Typically a 12 volt motor used for starting model engines.

Switch harness - A term used to describe the radio system on/off switch mounted to the model. A switch harness comprises a switch unit with cables to connect to the battery pack, the radio receiver and a fly-lead to allow the battery to be charged.

Tail-dragger - Describes an aeroplane with two wheels near the front and a small wheel at the tail. The aeroplane sits on the ground with its tail down.

Tailplane - The horizontal flying surface at the rear of an aeroplane. The tailplane is the fixed part; the flap attached to it is the elevator.

Tachometer - A hand held gadget that measures the rotational speed of an aeroplane propeller or a helicopter head.

Thermal lift - A thermal is an invisible column of rising air, which is typically formed by an area on the ground getting hotter than its surroundings. The air above it gets warmer than the air surrounding it and rises. A glider flown into this rising air will also rise assuming the lift is strong enough and the model is light enough. Thermals are not easy to find but are sometimes marked by birds circling in them and big thermals often have light fluffy (cumulus) clouds above them. A strong thermal is easily detectable when a model flies into it because you can see the model buck and / or rise.

Three-pointer - When an aeroplane lands and all three wheels touch at the same time.

Thrust - One of the four primary forces on an aircraft. Thrust is what drives the aircraft forward and is usually generated by a power source such as an engine and propellor. In gliders, thrust is a component of gravity i.e. a glider is always falling on a shallow glide path, a component of which is forward motion. A glider gains altitude by spending time in air which is rising faster than the glider is falling. Refer to slope lift and thermal lift. In a helicopter, thrust is generated by tilting the rotor disk. Click HERE for an aeroplane forces diagram and HERE for a helicopter forces diagram.

Tip-stall - A tip-stall occurs when the airflow breaks away from the tip of the wing before the root, hence lift is lost at the tip and the aircraft 'drops a wing' towards the stalled tip. The tip stalls before the root most commonly on aircraft with tapered wings because the smaller tip profile cannot generate the same amount of lift as the larger root profile. This can be overcome by introducing washout.

Tommy Bar - Describes the screw threaded bar on top of a model diesel engine used to adjust the compression ratio of the engine. This is an important adjustment to get right because too much compression will damage the engine and too little compression will make it low on power and difficult to start.

Trainer lead - The umbilical lead to link two transmitters for training purposes - refer to buddy box.

Transitional lift - The phenomenon where a helicopter needs a lower power setting to maintain height when flying in the circuit than it does when flying in the hover. For the same power setting, the rotor disk generates additional lift when a helicopter is on the move compared to when it is stationary.

Transmitter - The ground part of the radio control system that converts stick movements into command signals and transmits them as radio waves for the receiver.

Tricycle undercarriage - Describes an aeroplane with one wheel at the front and two wheels just behind the middle.

Trim - An aircraft which is properly trimmed will fly with the minimum of unpredictable changes and will require minimal corrections to maintain a constant flight path. An aircraft which is not trimmed may be difficult to control. The process of taking an untested aircraft and adjusting it to fly correctly is called trimming it out. A model radio control transmitter has an additional control for each primary function called a trim bar which allows the fine adjustment of each in order to make an aircraft fly correctly.

Tuned pipe - A form of exhaust system designed to enhance the power of a two-stroke engine. The internal design of a two-stroke engine means that for a short period the inlet port is open at the same time as the exhaust port. This means that some of the incoming fuel / air mixture goes straight through to the exhaust port and is never used. A tuned pipe is designed to reflect the exhaust gas wave back to the exhaust port, thereby preventing the fuel / air mixture leaving the cylinder before it has been used. The tuned pipe also helps the exhaust gas leave the engine more quickly, thereby allowing more fuel / air mixture in and tuned pipes are often quieter than standard silencers. The downside is that tuned pipes can be temperamental to set up. If the pipe is too short, it reflects the exhaust wave too soon and hot gases are sent back into the engine and it will overheat. If the pipe is too long, it reflects the wave too late and more fuel is pulled through the engine unused. When the correct length is established the engine is said to be 'on the pipe'.

Two stroke engine - A two stroke engine takes two complete strokes of the piston in the cylinder to complete a full engine cycle (one complete revolution of the propellor) - stroke 1, piston goes from top to bottom, spent fuel / air mixture from previous stroke is ejected as piston passes and opens exhaust port, fuel / air mixture is drawn in to the cylinder as piston passes and opens inlet port, there is some crossover as both inlet and exhaust ports are open at the same time, refer to tuned pipe - stroke 2, piston goes from bottom to top, piston passes and closes inlet and exhaust ports, fuel / air mixture is compressed, fuel /air mixture is ignited and explodes forcing the piston from top to bottom. Also, refer to four-stroke.

Tx - Short for transmitter.

U/C (Undercarriage) - Describes the wheels, axles and legs that support an aircraft when it's on the ground.

Valves - Valves are internal parts of engines that are timed to open and shut at specific times and for specific periods, to let fuel in and exhaust gases out. In conventional four stroke engines the valves are springloaded mechanical devices in the cylinder head, which are opened by a series of cams, pushrods, rockers and tappets. In rotary valve four stroke engines, the valve is a port that is opened and closed according to its position within a chamber with a fuel inlet on one side and and an exhaust outlet on the other. In some of the more esoteric two stroke engines, reed valves are used to control the inlet of fuel to the crankcase. Reed valve engines can run equally well in either clockwise or anti-clockwise directions.

Vibration - The nemesis of any model aircraft. It is good practice to eliminate as much vibration as possible because vibration can lead to damage. This means spending time balancing propellors, spinners, rotor blades, tail blades, cooling fans etc and fitting larger engines on anti-vibration mountings.

Wand - A hex shaped shaft (like a long allen key) connected into the end of a starter; used for starting helicopter and ducted fan engines.

Washout - A deliberate twist built into a wing such that the tip flies at a lower angle of attack than the root. The idea is to ensure that the root always stalls before the tip as a tip stall is a dangerous phenomenon that can cause unexpected loss of control at low speed or even induce a spin.

Washout base (or mixer) - Part of a helicopter rotor head.

Xtals - Short for crystals in the way that Xmas is short for Christmas.

Yaw - Left / right axis of rotation around the centre of gravity. Yaw control is via the rudder in an aeroplane and the tail-rotor in a helicopter.

TBC

Other

2.4 GHz - Describes radio control systems operating in the 2.4 GHz waveband. For details click HERE.

3D - Describes extreme aerobatic manoeuvers. For aeroplanes these manoeuvers are usually below the stall speed and rely on high power to weight ratios to maintain altitude. Many are characterised by high speed oscillations in all axes as well as manoeuvers where the model is made to hang on the prop.

4D - There is some debate about this as some manufacturers call their models 4D because they have side force generators allowing extended knife edge flight. Others say 4D flying describes specialised indoor aeroplanes such as shock flyers with reversible pitch propellors that can actually fly backwards.

540 / 720 - Describes variations of the stall turn manoeuver with a helicopter where the model rotates in yaw through 540 or 720 degrees instead of the normal 180 degrees.