3D: Term describing a type of flight pattern, which is characterized by the performance of very specialized aerobatic maneuvers below the model's normal stall speed. Examples include torque rolls, 'walk in the park', harriers, hangers, etc.

3F: Slang abbreviation for flip flop flying. Similar to 3D, but without the finesse.

ABC: Aluminum-Brass-Chrome. The components used in the production of non-ringed engines. These engines use an aluminum piston, and a chrome or nickel plated brass sleeve. The engine is harder to turn over and start due to the tight fit between the piston and cylinder. This tight fit is what makes the engine more efficient, and powerful. ABC engines must be run in for best performance.

ABL: Advanced Bimetallic Liner. Specialized form of ABN. Instead of a single-step, single-material plating, the ABL Plating process is based on a layered approach made possible by two OS-developed hard-nickel alloys. The first alloy is used as the bottom (bonding) layer, to fuse the top layer to the brass liner. The second alloy, developed for superior hardness, forms the top layer. Together, they create a barrier that protects the liner against excessive heat and wear.

ABN: Aluminum-Brass-Nickel. The components used in the production of non-ringed engines. These engines use an aluminum piston, and a nickel plated brass sleeve. The engine is harder to turn over and start due to the tight fit between the piston and cylinder. This tight fit is what makes the engine more efficient, and powerful. ABN engines must be run in for best performance.

ABS Plastic: Acetyl Butyl Styrene. A type of plastic that can be thermo-formed.

Accelerated Stalls: Occurs above the usual power-off stall speed when too much elevator control is input too quickly. This type of stall is usually far more violent than a wings-level, power-off stall. However, an airplane can be stalled at any speed if too much elevator is applied to fast.

Adjustable Travel Volume (ATV): ATV allows you to preset the maximum travel of a servo to either side from its neutral position. Such settings help tailor control action to suit your flying or driving style.

Adverse Yaw: The tendency of an airplane to yaw in the opposite direction of the roll. For instance, when right aileron is applied, the airplane yaws to the left, thus opposing the turn. Adverse yaw is common in trainer type airplanes having flat bottom wings. It is most noticeable at slow speeds and high angles of attack, such as during takeoffs and when stretching a landing approach. Caused by the unequal drag of the upward and downward deflection of the ailerons, this undesirable trait can be minimized by setting up the ailerons with Differential Throw or by coordinating the turns, using the aileron and rudder controls simultaneously. (See Differential Throw.)

Aero-elastic Flutter: (propeller) Is speculated to be a dominant mechanism causing rapid fatigue failure near a tip when insufficient or destabilizing tip stiffness exists. The interaction between variable loading and deflection induces a high frequency vibration with unpredictable magnitude.

Aero Tow: The act of an aircraft hauling a glider aloft and releasing it.

Aft: Towards the rear. Used such as: "...with an aft center of gravity....".

After Run Oil: A lubricant designed to displace unburned fuel in the engine after running. The fuel can accelerate corrosion on some engine parts. By using an after run oil, the fuel is displaced, and a protective coating lines sensitive engine parts. This is an inexpensive engine insurance, and promotes long engine life. Marvel Mystery Air tool Oil is one of the best.

Ailerons: Hinged control surface located at the trailing edge of each wing, that provides control of the airplane about the roll axis. Ailerons move in opposite directions in order to provide lift on one wing and "stall" on the other, in the process "rolling" the aircraft in the direction of the wing with the raised aileron.

Aileron Differential: Adverse yaw, especially on flat-bottom wings, is caused by the difference in airflow density between the bottom and top of the wing. The airflow along the wing’s bottom is denser than it is over the top of the wing. Therefore, the aileron moving down into this denser air creates more drag than the “up” aileron moving into the less dense airflow on top of the wing. The greater drag on just one side of the wing, the side with the down aileron, forces the wing, and the attached fuselage, to yaw in that direction. At slow airspeeds this yawing effect is more powerful, and happens faster, than the rolling effect caused by the ailerons. The airplane’s nose first swings away from the turn’s intended direction and only then begins to turn correctly once the roll begins.

Airfoil: The shape of the wing when looking at its profile. Usually a raindrop type shape.

AMA: The Academy Of Model Aeronautics . The official national body for model aviation in the United States. AMA sanctions more than a thousand model competitions throughout the country each year, and certifies official model flying records on a national and international level.

Angle of Attack: The angle that the wing penetrates the air. As the angle of attack increases so does lift and drag, up to a point.

Anhedral: Is the opposite of dihedral, having the wing tip centerline lower than the wing root centerline. Anhedral is generally used to aid in the instability of an aircraft to make it more aerobatic. Note that Anhedral is correctly measured as the vertical distance from the centerline of the root rib to the centerline of the wing tip.

Ailevators: Twin elevator servos plugged into separate channels used to control elevator with the option to also have the 2 elevator servos act as ailerons in conjunction with the primary ailerons.

ARF: A prefabricated model - Almost Ready to Fly. Well, OK, so what does "almost" mean? Usually it will take anywhere from 30 minutes to five or six hours....or more if you are just starting. Surprisingly, some modelers like to build models...sometimes from "kits" which have some items pre-cut and contain some of the non-wood parts needed to finish the model. Usually, however, NONE of the electronic items are included in an ARF except, perhaps, the motor...check the specs carefully before you purchase.

Aspect Ratio: The wingspan divided by the chord. Aspect ratio is important where a wing's efficiency is concerned. A short aspect ratio (short wings) is better for maneuvering, since it allows a high roll rate. Short wings are also stronger than long wings. Gliders use high-aspect ratio wings (long, skinny wings) because they are more efficient for soaring flight. Example: 10 ft. wingspan with a 1 ft. chord has an aspect ratio of 10.

ATV: Adjustable Travel Volume. Used on many radio transmitters to limit, or extend, maximum throw of a servo. ATV can indicate having a single adjustment which affects both ends of the servo (known as AST) or one adjustment for each end of the servo throw (known as EPA).

AUW: All Up Weight - The total weight of the project. This includes everything needed to make it run or fly. Receiver, servos, batteries, etc. The all up weight of the project.

Auxiliary Channel: any radio channel function other than the four basics (aileron, rudder, elevator and throttle).

Axial Roll: This type of roll is one where the aircraft’s fuselage remains exactly on the line of flight while the wings roll about it. Except for a very few jet fighters at high speed (the F-5 for one), no full size aircraft can perform a true axial roll. Most aircraft, especially trainers, roll about the line of flight, called a Barrel Roll.

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.

Bank: This is a measure of how far from level flight a plane’s wings are set during a turn of maneuver. It is measured in degrees of angle from level flight.

Ballast: Extra weight added to a glider to help it penetrate better in windy weather or to increase its speed. Ballast is usually added in tubes in the inner portion of the wings or in the fuselage at the center of gravity.

Ball Link: Connection using a ball, and a link which rotates on the ball. Used to connect the servo to a control surface or lever.

Barn Door Ailerons: Larger, built up ailerons rather than an aileron from a simple strip of solid wood like some kits have.

BB: These letters usually designate a ball-bearing supported crankshaft in an R/C engine or ball bearings in a better servo. This makes the engine run smoother and last longer.

BEC (battery eliminator circuit): A feature of some speed control units that permits both the motor and the receiver to be powered by the same battery.

BHP: Brake horsepower. A measurement standard used by manufacturers to help consumers compare engines. NOTE: BHP is measured at the maximum operating RPM of the engine, which may not be the RPM level at which your engine will provide maximum life and consistent performance.

Binding: Occurs when the friction at a joint is stronger than the linkage.

Blind Nut: (Also called a T-Nut) A pronged nut that is pulled into a surface such as wood so that it can not turn when a bolt is tightened into it. Blind nuts are typically used in situations where it would be impractical to use a tool, such as pliers, to hold the nut while the fastener is being tightened.

Boundary Layer: The thin layer of air immediately adjacent to a body moving through the air.

Bulkhead: A vertical former inside a fuselage.

Buddy Box: Training method utilizing two transmitter control boxes, linked together. The trainer radio has override control, which the instructor uses to take control when the trainee looses control, or becomes disoriented.

Butterfly: Also known as crow. A mix which activates up flaperons and down inner-most flaps for gliding speed control without spoilers or airbrakes. Crow (or butterfly) is only used for landing or perhaps for diving out of a thermal.

CA (cyanoacrylate): A modern hobby adhesive that cures very quickly. (read about how its made here)

CG: Center of Gravity. Describes a central point in a given body, where all weight is considered to be concentrated. A central balance point.

Cabane: A strut attaching a wing to the fuselage when the wing is above the fuselage such as biplanes and parasol aircraft.

Camber: If you draw a line through the center of the airfoil that's exactly half-way between the top and bottom surface, you get the mean airfoil line. Depending upon the airfoil, it can be straight or curved. This curve is called the "camber" of the airfoil. If it has a lot of curve, the airfoil is said to be "highly-cambered".

Canard: An aircraft having the horizontal stabilizer forward of the main wing rather than in the conventional position behind it. Canard aircraft are theoretically more efficient because both the horizontal stabilizer and the wing provide upward lift. The horizontal stabilizer of a conventional aircraft provides downward lift to stabilize the aircraft resulting in an overall decrease of the aircraft's total lift.

Carburetor: The part of the engine which controls the speed or throttle setting and lean/rich mixture via setting of the needle valve.

Castor Oil: Oil from a castor bean which is often used in glow fuels for lubrication and cooling.

Center of Gravity (CG): The balance point of a model airplane. For modeling purposes, this is usually considered -- the point at which the airplane balances fore to aft. This point is critical in regards to how the airplane reacts in the air. A tail-heavy plane will be very snappy but generally very unstable and susceptible to more frequent stalls. If the airplane is nose heavy, it will tend to track better and be less sensitive to control inputs, but, will generally drop its nose when the throttle is reduced to idle. This makes the plane more difficult to land since it takes more effort to hold the nose up. A nose heavy airplane will have to come in faster to land safely.

Center of Lift (COL): The location on the top of the wing where the sum of all lifting forces is located.

Centrifugal loads: (propeller) are very predictable, given rotational speed and mass density distribution of a blade. Their contribution to total stress is relatively small.

Chandelle: A very steep climbing turn where the airplane makes a 180° change of direction.

Channel: The number of functions your radio can control. Example: An 7 channel radio has 7 available servo slots used for separate control surfaces or switches. These channels can also be mixed on many radios, for such functions as collective, which increases pitch when throttle is increased.

Chicken Stick: A hand-held stick used to "flip start" a model airplane engine.

Chord: The "depth" of the wing, its distance from leading edge to trailing edge. One of the components used to determine wing area. May vary from root to tip.

Clevis: The Clevis is a small fastener at the end of a pushrod, usually made from nylon or metal, which connects the pushrod to the control horn. Clevises may frequently be referred to as links.

Clunk: Term used to describe the weighted end of the fuel pickup line in the fuel tank. The purpose of this is to ensure that the fuel pickup is always in the fuel supply, even when inverted.

Collet: A slotted jaw that allows a limited range of bits to be placed in a tool such as a router, moto-tool or pin vice.

Coning: This effect is the bending of the rotor or propeller blades when stressed.

Control Linkage: Any linkage transmitting servo movement to a control surface.

Control Surface: A movable surface such as elevator, rudder and aileron.

Conventional Tail: A Conventional Tail is one with the stabilizer mounted directly on the fuselage and is the usual configuration of an aircraft. These are the simplest to construct and seem to be most popular.

Covering: The covering of an aircraft is the skin which is applied to the airframe, closing it in. On R/C aircraft it is commonly a fabric or plastic film which is heat applied with an iron. Plastic covering, once applied, gives a durable, shiny finish and requires no further treatment. Fabric covering usually requires a layer of paint to finish it and make it resistant to the exhaust of the engine. Covering materials come on a roll and in many different colors and may be cut to rough shape before being ironed onto the airframe.

Cowl or Cowling: The large molded fairing around an engine. It serves two purposes: It helps the airflow go smoothly around the front of the airplane, and also provides a proper path for cooling air around the engine.

Crab: When an aircraft flies at a sideways angle relative to the direction being traveled. Can be caused by a crosswind or may be flown intentionally to reduce altitude without increasing forward airspeed while on landing approach.

Crow: See "Butterfly".

Crucifix Tail: A stabilizer that is mounted part way up the fin. This is a compromise between the conventional tail and the T-tail, combining some of the major advantages of both.

Datum: (aka Datum Line) A reference line from which measurements are taken.

Dead Stick: Slang term for a landing without engine power. An example: "I ran out of fuel at 50 feet and had to dead stick".

Decalage: The angular difference of the wing incidence and the horizontal stabilizer incidence.

Dethermalizer: A device used to spoil the trim of an aircraft and cause it to sink. A dethermalizer is most commonly used on free-flight endurance models to prevent them from flying away.

Detonation: Or pre-ignition is a potentially engine-damaging condition in which part of the fuel/air mixture ignites before the piston is at top dead center (TDC). Pre-ignition is a result of poor ignition timing and can be heard as 'engine knock'. In nitro engines, the proper combination of glow plug and nitro content will prevent this.

Delta Wing: Delta Wing aircraft have one large wing with a sharply swept leading edge and a strait trailing edge. The result is a wing that looks like the Greek letter Delta (Δ). There is usually no horizontal stabilizer with conventional elevators. Delta Wing aircraft use their ailerons for both pitch and roll control.

Differential Throw: Ailerons that are set up to deflect more in the upward direction than downward are said to have Differential Throw. The purpose is to counteract Adverse Yaw.

Dihedral: The upward inclination of an aircraft wing in relation to the lateral axis. A wing with dihedral is more stable and will tend to level itself from banked flight due to the higher wing having less lift than the lower wing.

Disk: Term describing the shape of the rotary wing or propeller formed by the spinning blades.

Direct Servo Control (DSC): This radio feature permits you to check servo operation without broadcasting a radio signal. A cable connects the transmitter to the receiver. Direct servo control is very useful for on-the-ground control checks.

Down Thrust: Downward angle of the engine relative to the centerline of the airplane. Down thrust helps overcome the normal climbing tendency caused by the torque of the engine.

Doublers: A second piece of balsa or plywood added to the fuselage side to enhance strength.

Drag: Air resistance that slows the model.

Dual Conversion: A dual conversion receiver filters the incoming radio signal from the transmitter through two separate and distinct electronic filters. This “double filtering” helps the receiver to ignore unwanted signals that are close to the frequency being used. This is NOT protection against another transmitter sending a signal on the SAME frequency. Instead, it is protection against other transmitters transmitting on frequencies that are close to the one being used.

Dual Rates: Radio function used to adjust control sensitivity.

Electric Starter: A hand-held electric motor used for starting a model airplane engine. Usually powered by a 12-volt battery.

Elevator: The pitch-control surface.

Empennage: The vertical and horizontal tail surfaces of an airplane.

Endpoint Adjustment: This radio feature adjusts the length of servo travel in one direction (a single channel will have adjustments for two endpoints). If your plane rolls faster one way than the other, endpoint adjustments can correct the problem.

Epoxy: A two-part resin/hardener glue that is extremely strong. It is generally available in 6 and 30-minute formulas. Used for critical points in the aircraft where high strength is necessary.

ESC (electronic speed control): The unit that controls the rpm of an electric motor.

Expanded Scale Voltmeter (ESV): Device used to read the battery voltage of the on-board battery pack or transmitter battery pack under load.

Exponential: This radio function allows the modeler to adjust the sensitivity of the control towards the center. This will make the small stick motions very precise, while longer stick movement moves the servo arm at a proportional rate.

EZ Connector: A Dubro product name generically used to describe a fitting that is attached to a control horn or servo arm by means of a pin and a snap connector. A wire or cable pushrod slides through a hole in the connector and is secured by means of a set screw. (personally, I prefer the good ol' z bend)

Failsafe: A PCM function which moves servos to a pre programmed position if transmitter signal is lost or corrupted.

Fairing: A component used to create a streamlined intersection between two or more other components or to cover a component to reduce drag.

Federation Aeronautique Internationale: Also called FAI-The European body that governs flying model similar to the Academy of Model Aeronautics in the United States.

Field Charger: A fast battery charger designed to work from a 12-volt power source, such as a car battery.

Figure 9: A loop that is terminated by a dive into the ground. This maneuver is entertaining for all pilots present except the one who performs the maneuver.

Flare: A gradual increase in pitch angle to bleed off excess airspeed just before landing.

Flaps: Hinged control surface located at the trailing edge of the wing inboard of the ailerons. The flaps are lowered to produce more aerodynamic lift from the wing, allowing a slower takeoff and landing speed. Flaps are often found on scale models, but usually not on basic trainers.

Flight Box: A special box used to hold and transport all equipment used at the flying field.

Flight Pack (or Airborne pack): All of the radio equipment installed in the airplane, i.e., Receiver, Servos, Battery, Switch Harness.

Flutter: A phenomenon whereby the elevator or aileron control surface begins to oscillate violently in flight. This can sometimes cause the surface to break away from the aircraft and cause a crash. There are many reasons for this, but the most common are excessive hinge gap or excessive "slop" in the pushrod connections and control horns. If you ever hear a low-pitched buzzing sound, reduce throttle and land immediately.

FM: Frequency Modulation. This describes the mode of transmission of radio signal from transmitter to receiver.

Four Stroke (Four Cycle): Although a 4-stroke engine has less power than a 2-stroke engine of comparable size, there are advantages to 4-stroke engines. They do not require a muffler and are often quieter than most 2-strokes are with a muffler. They can swing a bigger prop than the same size 2-stroke engine. This is an asset in the large, slow-flying aerobatic and scale models where 4-stroke engines are usually mounted. Lastly, the fuel economy is better.

Frequency Control: The FCC has allowed the 72MHz band to be used for R/C aircraft operations. This band is divided up into many different channels in which you can choose a radio system. You should be aware that certain areas have frequencies in which there is pager interference. This is why it is always a wise move to check with your local hobby shop to find out any channels that may be troublesome in the area you wish to fly.

Frequency Module: A frequency module plugs into the transmitter and enables you to change the channel number your radio broadcasts on.

Fuel Overflow Line (Vent): The fuel line is either open to atmospheric pressure or attaches to the muffler pressure nipple to pressurize the fuel tank for better fuel flow to the engine. This is the line through which the fuel will overflow when the tank is full.

Fuel Pick Up-Line: The fuel line in the fuel tank through which fuel travels to the carburetor. Typically a flexible tube with a weight or "Clunk" on the end which allows it to follow the fuel with changes in aircraft attitude. This is the line through which the tank is filled.

Fuselage: The main body of the airplane.

Glide Ratio: Is defined as the distance traveled in a horizontal direction compared with the vertical distance dropped on a normal glide. A 10 to 1 glide ratio means that the aircraft would loose one foot of altitude for every ten feet of distance traveled.

Glitch: Momentary radio problem that never happens unless you are over trees or a swamp ;)

Glow Heater AKA Ni-Starter: This is used to heat the element in a glow plug, and is used when starting the model engine.

Glow Fuel: A Methanol based fuel, with a lubricating agent, used in most model engines. Most model fuels also use a percentage of nitro-methane.

Glow Plug: This is the plug that is used to help ignite the fuel in a model engine. The combustion of the fuel in the engine keeps the element hot between cycles, thus the glow plug does not need to be regulated or powered while the engine is running.

Grease-In: A very smooth, gentle landing without a hint of a bounce.

Ground Effect: The cushion of air that the model rides on when close to the ground. This will decrease the amount of elevator needed to maintain a constant altitude when near the ground/landing.

Ground Loop: An unwanted acrobatic maneuver while you plane is on the ground. The plane suddenly spins in a circle, sometimes tipping nose down...not good for propellers.

Hangar Rash: A skin condition suffered by your aircraft when it is not taxiing, flying or landing. I.E. when your are transporting it to the flying field, or working on it on your bench, or when someone steps on it accidentally.

Header Tank: A small fuel tank located between the main fuel tank and the engine. The physics of the setup ensure that the header tank remains full until the main tank is nearly dry. It also prevents bubbles from reaching the engine and provides a more consistent run.

Hit: Sudden radio interference which causes your model to fly in an erratic manner. Most often caused by someone turning on a radio that is on your frequency, but can be caused by other radio sources miles away.

Horizontal Stabilizer: The flight surface that supports the elevator and also helps to stabilize the model in pitch.

Hot Start: An engine which has been running will tend to remain hot for a short time. During this period, it is possible to restart the engine by turning the crankshaft without the glow plug being plugged in to a glow starter. This is something to be aware of, as it could possibly create an unsafe condition.

Hydraulic Lock: Hydraulic lock happens when the engine becomes flooded with fuel, to the point where the piston cannot compress it in the combustion chamber. This can result in engine damage if the crankshaft is forced through a rotation without relieving the pressure. To cure, remove the glow plug, and pour out the excess fuel.

Idle Bar Plug: This type of glow plug has a "bar" across the tip to help prevent raw fuel from being splashed onto the glow element. Too much raw fuel will cool the plug and prevent it from igniting the fuel/air mixture. An idle bar is a help in obtaining a low idle speed.

Immelmann: A maneuver originally used to reverse direction in combat. The airplane noses up and over onto its back. It then rolls upright and continues in the direction opposite to the original direction. It was invented by the World War I German pilot Max Immelmann, whose airplane could perform the maneuver, and other's couldn't. It got him out of a lot of trouble in combat until the Allied aircraft designs caught-up and allowed their planes to perform the maneuver, too.

Incidence: Angle of the airfoil's centerline to the longitudinal axis of the aircraft. Positive incidence indicates that the center of the leading edge is higher than the center of the trailing edge. Negative incidence indicates that the center of the leading edge of the wing is lower than the center of the trailing edge of the wing.

Incidence Meter: Used to measure the angle of attack of an airfoil.

Kit: A Kit describes an unassembled model, arrives as packages of parts which must be assembled, as opposed to an ARF, or Almost Ready to Fly, which is mostly pre assembled or a PNP Plug and Play.

Laminar Flow Wing: Laminar Flow is the smooth, uninterrupted flow of air over the contour of the wings, fuselage, or other parts of an aircraft in flight. Laminar flow is most often found at the front of a streamlined body and is an important factor in flight. If the smooth flow of air is interrupted over a wing section, turbulence is created which results in a loss of lift and a high degree of drag. An airfoil designed for minimum drag and uninterrupted flow of the boundary layer is called a laminar airfoil.

Lateral Balance: The left-right or side-to-side balance of an airplane. An airplane that is laterally balanced will track better through loops and other maneuvers.

Leading Edge (LE): The foremost edge of an airfoil or propeller, first part of the wing or propeller to go thru the air.

Lean: Refers to carburetor setting. When an engine is run too lean it will overheat, causing damage, and likely an in flight engine failure. Tuning a carburetor is best accomplished by starting rich, and working gradually to the condition which produces maximum power, while allowing a small amount of unburned fuel mixture to lubricate and cool the engine.

Lift: The aerodynamic force generated by air flowing around an airfoil that is equal to or greater than the weight of the aircraft and acts opposite to the force of gravity.

Longeron: A load-bearing, fore to aft structural member of a fuselage.

mAh (Milliamp Hour): A measure of a battery's total capacity. The higher the number (ex. 600 mAh, 1,500 mAh) the more charge a battery can hold and usually, the longer a battery will last under a certain load. Typical rechargeable receiver battery packs are in the 500-600 mAh range. Typical R/C car motor batteries are in the 1,200 - 1,500 mAh range.

Mixing (Coupling): Two radio control channels can be coupled together so that they move together when only one control channel is activated. Many 1/4 scale models require a combination of aileron and rudder to turn. Mixing does this electronically at the transmitter. V-tailed models, where the two halves of the V-tail must move not only together but independently, are another use of control mixing.

Moment (nose moment, tail moment): Refers to a distance on a model forward or aft of the balance point.

Moment Arm: The distance between where a force is applied and the Center of Gravity. The distance from the Elevator hinge line to the Center of Gravity is the Pitch Moment Arm.

Muffler: A device attached to the exhaust stack of the engine to reduce noise and increase back pressure which helps low speed performance. Note: Most R/C Clubs require the use of mufflers.

Muffler Baffle: A restrictor plate inside the muffler which reduces engine noise. This plate can be removed to increase power, but only if there are no noise restrictions where you fly.

Needle Valve: Adjustment on a carburetor used to set proper fuel/air mixture. Some carburetors have separate needle adjustments for low and high throttle. Typically, turning the needle clockwise (screwing in) leans the mixture (less fuel), and vice versa. However, there are a few exceptions--refer to the engine manufacturer's instructions.

Negative or Positive Shift: In North America, FM radios are grouped by those using positive shift and those that use negative shift. Typically we speak of JR and Airtronics as positive shift. Hitec and Futaba are negative shift. In some cases these brands can be made to change shift through a function called shift select or reverse shift. In most of the rest of the world, all radios are positive shift, as I understand it. Shift refers to how the radio codes instructions for the receiver. One is not better than the other, they are just different. This is only important when you are buying a new receiver as you need to be sure that your FM receiver and your FM radio are using the same shift. Shift does not apply to AM radios. Crystals are not specific to shift, but they may be specific to AM vs. FM.

Nose: The front portion of a model's fuselage.

Nitro: Nitro-methane, a fuel additive which increases a model engine's ability to idle low and improves high speed performance. Ideal nitro content varies from engine to engine. Refer to the engine manufacturer's instructions for best results. Nitro content in fuel is indicated by the percent of the fuel.

NiCd: Nickel Cadmium battery. Rechargeable batteries which are typically used as power for radio transmitters and receivers.

Ni-Starter: A self-contained battery and glow plug clip, used when starting the engine. (See Glow Plug Heater.)

One-Point Landing (or a figure 9): Synonymous with "stuffing it in." Something we hope you never do.

Over-control: Excessive control inputs that overcompensate for unwanted model movement.

Parasitic Drag: A resisting force caused by external items mounted on an aircraft other than the lifting surfaces.

PCM: Pulse-code modulation (PCM) is a digital representation of an analog FM signal where the magnitude of the signal is sampled regularly at uniform intervals, then quantized to a series of symbols in a digital (usually binary) code. PCM Hides small amounts of interference. The advantage of this is that transient interference (brief bursts of static) will cause the servos to hold their last position until the receiver can recognize the signal again. This is definitely a good thing if you're in a contest, because it means your aircraft won't bobble unexpectedly. The only drawback to this is that if your aircraft has a small radio frequency interference (RFI) problem, you won't see it right away. By the time this small problem develops into a big problem, it may be too late.

Peak Charger: A peak charger automatically shuts off when your battery is fully charged. This means longer run times for your vehicle. Peak chargers are nearly foolproof, if you forget to turn it off, the charger does it for you. No more overcharged batteries.

Pitch: The pitch refers to the angle of the aircraft in the up or down direction.

Pitch Axis: The airplane axis controlled by the elevator. Pitch is illustrated by holding the airplane at each wingtip. Raising or lowering the nose is the pitch movement. This is how the climb or dive is controlled.

Platform: The outline of a flight surface. For example, an elliptical shaped wing has an elliptical platform.

PNP: Plug And Play, Usually comes set up with every thing ready to fly except the receiver and transmitter. Although some even come with the receiver and transmitter.

Positive Shift: See "Negative or positive shift" above.

Polyhedral: When viewed from the front (leading edge), a wing with polyhedral has three distinct points at which its surface is angled upward relative to an imaginary horizontal line which the leading edge would follow if the wing were perfectly flat from tip to tip. The two wing halves form the first angle which occurs in the center of the wing (if we stopped here, the wing would have dihedral. At equidistant points from the center of the wing (and typically closer to each wing tip than the center) on each wing half, there is another "break point" where the wing angles up again, making the wing tips higher, when measured from the imaginary horizontal line.

Power Panel: 12-volt distribution panel that provides correct voltage for accessories like glow-plug clips, fuel pumps and electric starters. Usually mounted on a field box and connected to a 12-volt battery.

PPM (aka FM): Pulse Position Modulation (PPM) is an analog signal also known as FM. The disadvantage of course is that your aircraft will jump around during RFI incidents that would go unnoticed with PCM. The advantages of PPM is that the receivers cost less and small RFI problems have a way of growing into large RFI problems. Some pilots like the security that comes from seeing problems when they're tiny, so they can be investigated and fixed before they become large.

Preflight: A thorough check of an aircraft prior to flying it to ensure that it is airworthy and safe. A proper pre-flight should include checking that all control surfaces are solidly attached, as well as items such as the propeller, spinner, landing gear, linkages, etc.

Programmable or Computer Radios: These high-tech radios are not inexpensive but allow a full set of programmable transmitter features like multiple plane memory, preprogrammed maneuvers (rolls, loops, etc. at the touch of one button) and much more.

Prop Pitch: Props are designated by these two numbers, for instance 10 - 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".

Prop Balancer: Used to ensure that the propeller and spinner are equally balanced side-to-side to avoid vibration problems.

Receiver: The part of the radio system that converts radio signals sent by the transmitter into electrical impulses.

Re-Kitting: Changing your finished model back into a kit, as a result of "stuffing it in."

Resonance: This is the vibration frequency of a rotating or moving object. When the resonance of many parts of a machine are in synch, the whole machine will vibrate at a greater rate. This can cause vibration damage. Resonance can cause difficulties in an aircraft, particularly when using a vibration mount with an improperly balanced propeller/spinner wherein the engine is vibrating at one frequency and the propeller at another.

Retracts: Short for retractable landing gear. Wheels and struts that fold up into the airplane to get them out of the air stream and present less resistance to the airflow.

RFI: Radio Frequency Interference.

Rib: The internal, vertical portion of the wing that gives it an airfoil-shaped contour.

Rich: This refers to the air/fuel mixture on an internal combustion engine. A "rich" mixture means that there is not enough air compared to the amount of fuel entering the combustion chamber. If you are not careful, this condition can lead to hydro lock.

Roll Axis: The airplane axis controlled by the ailerons. Roll is illustrated by holding the airplane by the nose and tail. Dropping either wingtip is the roll movement. This is used to bank or turn the airplane. Many aircraft are not equipped with ailerons and the Roll and Yaw motions are controlled by the rudder. This is one reason why most trainer aircraft have a larger amount of dihedral.

Roll Coupling: Applying rudder alone can cause the aircraft to bank into a turn without aileron input. The ability of the rudder to perform a banked turn is called roll coupling since the rudder input also induces the roll into the bank. Roll coupling is caused by wing dihedral, (the upward bend in the wing), and rudder placement. The higher the rudder is above the wing and fuselage, the greater its roll coupling effect. Roll coupling in performance aerobatic aircraft is not a good thing as it makes certain maneuvers, like a slow roll or stall turn, very difficult. But it is good in an aerobatic trainer as it teaches the pilot how to coordinate rudder and aileron.

RTF: Ready-to-Fly. Some newer airplanes are now available as RTF models. These planes usually come with everything needed for flight--plane, radio system, engine and all hardware. The really nice thing about an RTF is that it will almost always be completely pre-built with only a few minor construction steps left for the modeler. If you want to fly and want to fly now, RTF is the way to go.

Rudder: The vertical control surface that controls yaw.

Rx: Abbreviation for receiver.

Servo: An electromagnetic device that moves the control surfaces and is controlled by the electrical impulses from the receiver.

Servo Output Arm: The removable arm or wheel which bolts to the output shaft of a servo and connects to the pushrod.

Servo Reversing: This radio feature allows you to install the servos where they can give the best pushrod routing without concern about the direction of servo rotation. When your installation is complete, turn on your radio and check each channel. If a channel operates opposite of its intended direction, a simple flick of a switch corrects the problem.

Sesquiplane: A biplane having one wing significantly smaller than the other.

Slat: A high-lift device on the leading edge of a wing designed to keep air flowing over the wing at a higher angle of attack than could be achieved otherwise.

Slip: A maneuver where the airplane's controls are used to make the fuselage fly at an angle to the line of flight. This causes a tremendous increase in drag, and allows an airplane without landing flaps to increase its angle of descent without picking up a lot of speed.

Slop: Unwanted, excessive free movement in a control system. Often caused by a hole in a servo arm or control horn that is too big for the pushrod wire or clevis pin. This condition allows the control surface to move without transmitter stick movement. (See Flutter.)

Snap Roll: A type of rolling maneuver that is very quick and violent. It's basically a spin where the flight path is in any direction chosen by the pilot.

Solo: Your first totally unassisted flight that results in a controlled landing.

Speed Brakes: Large panels that fold out of the aircraft structure to provide a lot of extra drag to the air. They are not part of the wing structure, but are usually mounted on the fuselage. Military jets most often have speed brakes, which fold out of the fuselage. Some airliners use spoilers as speed brakes when at altitude.

Spinner: Cone on the front of the propeller made from plastic or metal to improve aerodynamics, looks and use of an electric starter.

Split-S: Basically a reverse Immelmann. The airplane rolls onto its back, and then the nose comes down to finish a 1/2-loop. The direction of flight is changed 180°.

Sport Airplane: A model which possesses some attributes of many of the specialty airplanes and are best for general flying as they are the most versatile and durable.

Sputter Bug: (slang courtesy of RC Universe) A new Nitro owner running his engine too Rich and all the excess fuel either runs down the fuselage or on the track!

Stab: Horizontal stabilizer.

Stall: When the air flowing over the wing cannot produce enough lift to support the weight of the model, it's called a "stall". This can happen if the modeler flies too slowly, or if the wing is at a too-high angle to the incoming airflow. If the wing is at a too-high angle to the incoming airflow, then it cannot flow over the wing properly to develop lift.

Stall Turn: The maneuver in which the model is flown to a point at which the rotor disk/main wing is vertical, reaches an apex/stalls, then is turned about the yaw axis to continue in a nose forward/down attitude, then is returned to horizontal flight.

Sub-Trim: This is a trim function on many computer radios, allowing trim function during set-up, and still allowing the full trim function in flight.

Tail Dragger: This refers to the landing gear configuration where the main landing gear with two wheels is placed forward of the center of gravity and one small wheel, called a “tail wheel”, is mounted under the tail of the aircraft.

Tail Wheel: The small wheel at the tail of the airplane. This is found on the type of airplane that has the two large wheels in the front, and the small one in the rear. The airplane sits on its tail.

TE: Trailing Edge (rear)

Thrust/Drag Loads: (propeller) Are somewhat uncertain due to complexities of aerodynamic environments. The relative axial speed at the prop (at any radial station) is aircraft speed plus the amount the air in front of the blade is accelerated by the mechanics creating thrust. The latter may be approximated using first order classical theory. Much empirical lift/drag data (from wind tunnel tests) exists to quantify lift/drag loads, once relative velocity and angle of attack distributions are established.

Tip Stall: The outboard end of one wing (the tip) 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.

Torsional Acceleration Loads: (propeller) Are generally not known. Analytical estimating technique used by Landing Products to quantify torsional acceleration loads suggests that they can become dominant when pre-ignition or detonation occurs. These analytical observations are supported by test experience with very high performance engines running at elevated temperatures. The latter causes a high torsional load (about the engine shaft) which creates high bending stresses, adding to those from centrifugal force and lift/drag effects. These torsional acceleration loads depend on unique conditions for specific engines. Engines "hopped up" for racing appear to be especially prone to create high torsional loads when lean mixtures lead to high cylinder temperatures and pre-ignition/detonation.

Torque: The force which tends to cause rotation.

Touch-And-Go: Landing and taking off without a pause. Often confused with a good bounce.

Trailing edge (TE): The aft-most edge of an airfoil or propeller.

Trainer Airplane: A model designed to be inherently stable and fly at low speeds, to give first-time modelers time to think and react as they learn to fly.

Trainer System: This effective method of training allows two transmitters to be connected by means of a trainer cord. The instructor can pass control over to the student's transmitter so that he can fly. If the student gets into trouble, the instructor can regain control instantly.

Transmitter: The hand-held part of the radio system that sends the signal to the receiver.

Tricycle Landing Gear: Refers to the landing gear configuration with a single steerable nose wheel mounted in front of the center of gravity, and a set of main landing gear with two wheels positioned just behind the center of gravity. Tricycle landing gear is usually a little easier to use when learning.

T-tail: Refers to a stabilizer that is mounted on top of the fin. This brings the stabilizer away from the turbulent air-flow of the wing and makes pitch control more responsive. It also gets the stabilizer out of harms way when landing on rough terrain. The T-tail construction is usually more fragile than the conventional tail, though, and are more difficult to build.

Trim: The adjustment of a model's control surfaces to obtain a stable and balanced flight performance.

Vertical Fin: A fixed, vertical stabilizer that reduces the model's tendency to yaw about the vertical axis.

Washout: An intentional twist in the wing, causing the wing tips to have a lower angle of attack than the wing root. In other words, the trailing edge is higher than the leading edge at the wing tips. Washout helps prevent tip stalls.

Weathervane: An aircrafts natural tendency to turn into the wind.

Wheel Collar: A small, round retaining device used to keep wheels from sliding off an axle.

Wind Sock: A tubular flag like device that shows the direction of wind movement. Wind speed may also be approximated by the angle at which the sock hangs. Used by pilots to aid with takeoff, landing, and flight patterns.

Wing Chord: The distance measured horizontally between the wing's LE and TE.

Wing Loading: This is the amount of weight per square foot that has to be overcome to provide lift. It is normally expressed in ounces per square foot. This specification can be easily calculated as follows: If you know the square inches of the wing, simply divide by 144 to obtain square feet. Divide the total weight (in ounces) of the airplane by the wing area (in square feet). This information is valuable when deciding on which airplane to build next. Planes with high wing loading numbers must fly faster to stay in the air. These are generally "performance" airplanes. Conversely, planes with lower numbers do not need as much air flowing around the wing to keep it flying. Trainers are designed to have low wing loading because slow, efficient flight is desired.

Wing Root: The centerline of the wing, where the left and right wing panels are joined.

Y-Harness: Two servos can be plugged into one channel with a Y-harness. The two servos will then operate simultaneously. It is most often used in areas where the strength of one servo is not adequate.

Yaw: The left or right movement of an aircraft's nose about its vertical axis.

Yaw Axis: The airplane axis controlled by the rudder. Yaw is illustrated by hanging the airplane level by a wire located at the center of gravity. Left or right movement of the nose is the Yaw movement.

Z-bend: Shaped like a “Z,” it is the simplest way to connect a pushrod to a control horn or servo-output arm.

3D Maneuver Explanations by Aircraft Proving Grounds.com

1. Half Cuban Eight: Model pulls up and executes five-eighths (5/8) inside loop to 45 degrees, hesitates, does one-half (1/2) roll, hesitates, then performs one-eight (1/8) inside loop back to level flight in the opposite direction as entry.
2. Slow Roll: Model rolls at a uniform rate through one (1) revolution in either direction. Center is the inverted portion of maneuver.
3. Inside Loop: Model pulls up and executes the loop. The loop should be completely round.
4. Split S: Model performs one-half (1/2) roll in level flight then immediately executes one-half inside loop to level flight in opposite direction as entry. (This is basically an Immelmann done backwards.)
5. Immelmann: The model starts the Immelmann flying straight and level, pulls up into one-half (1/2) loop immediately followed by one-half (1/2) roll and finishes flying straight and level and exactly 180 degrees from the heading at entry.
6. Half Reverse Cuban Eight: Model pulls up and executes one-eighth (1/8) inside loop to 45 degrees, hesitates, does one-half (1/2) roll, hesitates, then performs five-eights (5/8) inside loop back to level flight in the opposite direction as entry.
7. Hammerhead (stall turn): Model executes one-quarter (1/4) loop to a vertical track, performs a stall turn through 180 degrees, then recovers with another one-quarter (1/4) loop to level flight in the opposite direction
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8. Straight Flight: The model must be brought exactly parallel to the flight path and flown in an absolutely straight and level path.
9. Inverted Flight: The model flies along a straight line inverted.
10. Knife Edge: Model rolls 90 degrees at a uniform rate. The center of gravity is held at a constant altitude during the entire maneuver using rudder for altitude and elevator for rudder.
11. Take off: The model must stand still on the ground with the engine(s) running, without being held. The throttle is then smoothly, not suddenly, advanced. After the takeoff roll has started, the nose wheel lifts off the ground (tail wheel for a conventional gear airplane), and the aircraft assumes a climb attitude while still rolling on its main wheels. When the aircraft reaches flying speed it should gently lift off the ground and climb at a gradual angle. The aircraft must not deviate in heading during the takeoff. The takeoff is completed when the model is approximately 2 meters (6 1/2 feet) from the ground.
12. Landing: The landing maneuver will start two (2) meters from the ground. The model flares smoothly to a nose-high attitude, dissipating flying speed, then smoothly touches the ground, within the landing zone, with the main wheels first, with no bouncing or changes in heading after touchdown. The nose wheel on a tricycle gear and the tail wheel on a conventional (unless a "three (3) point landing" of mains and tail wheel touching simultaneously is executed) should settle gently to the ground after a brief rollout. The maneuver shall be considered complete once the plane has slowed below flying speed and has rolled straight for 15 meters.