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3D

• Term describing a type of flight pattern, which is characterized by combining two or more maneuvers into one maneuver. Examples: rolling circle, inverted backwards loop.

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

• Number describing degrees in an arc. A 360 represents one full turn through an axis. A 540 stall turn, for example, describes a one and one half revolution spin at the apex of a vertical stall, which results in the helicopter resuming nose forward flight before recovery.

• 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.

• 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.

• Advanced Bi-metallic Liner. A plating process using layered alloys to plate the piston sleeve. This resists flaking, resulting in a longer lasting fit between piston and sleeve.

• Almost Ready to Fly. A kit which is mostly pre-assembled, usually requiring installation of few parts, engine, and radio gear. Compare to a kit, which is a package of parts which require assembly.

• Adjustable Travel Volume. Used on many radio transmitters to limit, or extend, maximum throw of a servo.

• This describes the blade which is moving in the same direction as the helicopter in forward flight.

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

• 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. There are several good after run oils on the market.

• Aileron, or cyclic roll, banks the helicopter to the right or left. The tilt of the swashplate is used to control this function.

• This refers to the shape of a wing. In helicopters, the rotor disk is the effective wing, and airfoil refers to the shape of the blades.

• The amount of pitch at which an airfoil is flying. By adjusting the angle of attack, the efficiency of a blade is effected. More precisely, the angle between the chord of an airfoil and the wind.

• This is borrowed from full sized helicopters, and is a rotor head which allows the blades to flap, drag and feather.

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

• The line around which a body rotates.

• 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.

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

• A rigid, short antenna mounted to the model. Used to replace the longer receiver antenna.

• Control system used in helicopters. Changes pitch of blades in relation to their position via a swashplate. A flybar with paddles is used to gain responsiveness. The two systems are linked with Control Levers.

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

• One of several devices designed to aid in the process of balancing the rotor blades for a helicopter. Many of these will also help to match the C.G. of the blades.

• Term describing the event of a blade hitting another object. Although this can seem like a minor impact, the blades should be carefully and thoroughly inspected, as structural integrity is often compromised, producing an unsafe condition. If any question remains, do not fly until the blades are replaced.

• The act of a blade hitting the tail boom.

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

• Cyano-Acrylate glue. This adhesive is a fast cure type. There are many types used in model building. Refer to owners manual of kit to determine if used.

• Cyclic-Collective-Pitch-Mixing. Type of swashplate mixing which requires a radio with CCPM mixing functions. This uses three servos to control the cyclic, while all three work together to raise and lower the swashplate for collective control.

• Center of Gravity. A measurement used when balancing blades, as well as the model overall. Describes a central point in a given body, where all weight is considered to be concentrated. A central balance point.

• An imaginary point whereon the chord of an airfoil where the total of all aerodynamic forces are assumed to act.

• The force created by a bodys tendency to to follow a straight path working against a force which causes it to move in a curve, the resultant force which pulls away from a central axis of rotation.

• The frequency number used by the transmitter to send signals to the receiver. If radios transmit on the same frequency, or channel, glitching will occur in the active receiver on that channel. This is due to conflicting signals sent by the two radios. Flying sites should have a frequency control system to ensure that only one radio operates on any given channel at one time. This is usually a board with some type of marker for each channel. If the marker is not available, someone else is using that channel. Do not use your radio unless you are sure you are the only one on the frequency.

• The number of functions your radio can control. Ex: an 8 channel radio has 8 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.

• The imaginary straight line between the leading and trailing edges of an airfoil.

• 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

• The section of the drive train used to engage the gear when throttle is increased, and disengage while engine is at idle. This ensures that the rotor blades can remain at rest while the engine is idling.

• The mixing function which increases blade pitch when throttle is increased, and decreases pitch when throttle is decreased. This type of mixing allows autorotation to take place, and is more responsive than fixed-pitch machines.

• This effect is the bending of the rotor blades when stressed.

• Term used for the horizontal controls used to determine the attitude of the helicopter. Also known as elevator and aileron.

• This device reduces blade oscillation around the hinge.

• A landing without engine power is commonly called this. This term is more often used to describe an unexpected autorotation. An example: "I ran out of fuel at 50 feet and had to dead stick".

• The condition in which the helicopter is set up to fly smoothly and predictably. This is the state where the mechanics and electronics work together to produce the best performance.

• Term describing the shape of the rotary wing formed by the spinning blades.

• Describes the condition of the rotor blades in relation to wind. The advancing blade tends to be moving faster than the retreating blade, due to the fact that the advancing blade is flying into the wind, while the retreating blade flies with the wind. This affects the amount of lift created by the individual blades in flight, resulting in a banking action. A helicopter with independent flapping blades will help to lessen this effect.

• The air resistance to forward motion. Drag can be increased with the use of certain types of devices installed on the aircraft, such as spoilers, airbrakes, or flaps. Old-style aircraft with lots of supporting wires had very large amounts of drag, while modern aircraft such as military jets, have very low drag.

• Radio function used to adjust control sensitivity.

• Cyclic- fore and aft. The control used to tilt the helicopter rotor head forward or backwards.

• The methanol or gasoline fueled power plant used in a model helicopter. These are commonly a two stroke engine, due to their higher performance and lower weight, but four stroke engines are also used.

• 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.

• Fast Forward Flight. This term is used when the helicopter is flying at a great rate of speed.

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

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

• The rod which supports the rotor blade grips. A flapping head has two of these, each of which allows some up and down movement. A see-saw type head has one feathering shaft between the two blade grips.

• The helicopter with the blade pitch fixed in one position is a fixed pitch machine. The accent and decent rate is controlled by the throttle, which increases and decreases head speed, thus generating the needed lift for the maneuver. These helicopters are simpler to build, and have fewer parts, but are tougher to fly. The use of throttle to control lift is not as responsive as collective pitch systems.

• Used to describe a rotor head in which the blades are allowed to flap independently.

• The methanol/nitromethane/lubricant mix used to fuel model engines. A helicopter fuel mix has a higher concentration of lubricant to counter the lack of sufficient airflow over the engine in a hover.

• Gyro sensitivity. When too low, the tail will not hold position well. When too high, the tail will tend to wag, or hunt for center.

• A helicopter using a gasoline engine as a power plant.

• A Methanol based fuel, with a lubricating agent, used in two stroke model engines. Most model fuels also use a percentage of nitromethane.

• This is used to heat the element in a glow plug, and is used when starting the model engine.

• This is used to heat the element in a glow plug, and is used when starting the model engine.

• 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.

• This is used to heat the element in a glow plug, and is used when starting the model engine.

• This is used to regulate rotor RPM.

• The cushion of air that the helicopter rides in when close to the ground. This will decrease the amount of collective needed to hover when near the ground.

• This describes the vibration effect that can cause a balanced helicopter to appear out of balance while on the ground. This effect will be most evident while on hard surfaces which do not absorb vibration.

• A mechanical or electronic device which helps to stabilize the orientation of the helicopter by sensing rotation, and moving the tail rotor servo to compensate. This device can be used on any axis, but is most frequently used on the tail rotor, as this is the hardest control to dial in.

• This term describes the tendency of a rotating body to tilt in the direction of an applied force 90 degrees later in the plane of rotation.

• This is a small fuel tank used in line between the main tank and the carburetor. The purpose of the header tank is to ensure that the fuel fed to the carb is free of bubbles, which can be caused by foaming, or by the clunk falling away from fuel during complex maneuvers. Also, lets the pilot see the fuel level for helicopters which have a hidden fuel tank.

• This describes a type of Gyro which senses rotation, as well as the direction of the helicopter. This is accomplished by sensing the rate of motion, and the time of motion, then compensating for the distance. While this sounds complicated, the effect is that if you have the helicopter dialed in, and point the nose north, with a heading hold gyro the helicopter will continue to face north until you command it to turn. See also Heading Lock.

• This describes a type of Gyro which senses rotation, as well as the direction of the helicopter. This is accomplished by sensing the rate of motion, and the time of motion, then compensating for the distance. While this sounds complicated, the effect is that if you have the helicopter dialed in, and point the nose north, with a heading lock gyro the helicopter will continue to face north until you command it to turn. See also Heading Hold.

• A fuel mix using a higher concentration of lubricant, to aid in the cooling of the engine in helicopter models.

• The helicopter radio differs from the standard radio in a few ways. First, the heli radio will need mixing functions specific to helicopters, and usually a minimum of five channels. Collective mixing for collective pitch helicopters is a necessity. Many fine radios are available which have this mix, and many more. Another difference between heli radios and airplane radios is the throttle stick, which is ratcheted in airplane transmitters, will not have the clicking feel on the heli version. This is due to the precise control needed on the heli collective stick to achieve and sustain a controlled hover. The radio used for a helicopter will vary from user to user, and the parameters used will vary from helicopter to helicopter.

• A balancing tool used to balance larger assemblies, such as a complete rotor head assembly.

• 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.

• The art of flying, without moving. This can also be an illusion, depending on windspeed. A helicopter in forward flight at 5mph into a 5mph wind will appear to be stationary relative to a fixed point on the ground. Relax, call it a hover and enjoy. This is the first maneuver most pilots strive to learn, and is often one of the hardest to master. This seems like another paradox, but as this is a critical position, and is often the beginning and end of many flights, it is quite necessary to learn first. Start with low hovers, with the helicopter nose facing away from you. In this orientation, the controls will respond in a predictable manner, and the helicopter will not have far to go if you do get into an uncomfortable position. Watch the whole machine, but pay particular attention to the body. This will give the best indication of a shift in orientation.

• 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.

• This is a setting on the transmitter which limits the throttle minimum. Particularly useful for FFF and 3D stunt flying.

• Used to measure the angle of attack of an airfoil, can be used to measure blade pitch, or paddle pitch.

• Flying upside down. This is accomplished using negative blade pitch relative to the helicopter to produce lift while upside down.

• When referring to helicopter models, a Kit describes a package of parts which must be assembled, as opposed to an ARF, or Almost Ready to Fly, which is mostly pre assembled.

• The rail or wheeled feet of the helicopter.

• The rail type landing gear used on many helicopter models.

• 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.

• This happens when an engine is dialed in, then developing a lean condition. Possible causes are fuel foaming due to excessive vibration, or a leak developing in the fuel delivery system. The air in the fuel line will cause the engine to run lean.

• The load placed on the airfoil of a flying machine. In the case of a helicopter, this would be blade loading. Found by dividing the weight of the helicopter by the total area of the rotor blades.

• The agent used to aid in the reduction of friction between two parts. This term is used for many substances, which in turn are used in many different ways. They are all, however, used to reach the same objective, that being the reduction of wear between parts. In the case of engine fuel, the lubricant is added to the fuel at the factory in many cases. This might be castor, a synthetic, or a blend. The percentage of lubricant required in the fuel will depend on the type of fuel, the engine, and the model requirement. For helicopters, a higher percentage of lubricant is required, as the engine is not in a position to receive as much airflow. Thus the lubricant is also used as a coolant. Bearing grease, and oils for moving parts are other examples of lubricants.

• Speed in Miles Per Hour. Like RPM, MPH is both singular and plural. You can go 1 MPH or 100 MPH. You don't go 100 MPH's.

• Slang term used to describe the difficulty of helicopter hovering to a newcomer. Hovering is like balancing a marble on a glass surface. As a side note, there have been trainer boxes using this very setup to give the beginner the feel of helicopter control without risking damage to a helicopter. For the modern pilot, a good simulator works much better.

• The power band of an engine between idle and full throttle. The helicopter engine will be tuned for optimum performance in the midrange, as that is where the helicopter will hover.

• Radios with mixing will take two or more controls and mix their output in relation to stick input. The number of channels that can be mixed, and the precision of the mixing curve, or number of curve points, will depend on the transmitter used.

• A specialized lever which has three or more pivots. The length between pivots will determine the proportion of the mix between two or more linkages.

• Fuel to air mixture is determined by the needle valve on the engine carburetor.

• Any electric motor used on the helicopter. Examples are the servo motors, which move the servo arms, and thus the control surfaces. There are also helicopter kits which use electric motors in place of the engine for quieter, cleaner flight.

• This is used to tune the fuel to air mixture on the engine carburetor. On most engines, the needle is turned clockwise to lean the mixture, and counterclockwise to richen.

• Abbreviation for nitromethane. The addition of nitromethane in fuel provides more power, and a smoother idle, thus making the engine easier to tune. The nitro also makes an engine run hotter, therefore, the amount of nitro added to a fuel results in a tradeoff. Common nitro mixes for helicopter use are 15% and 30%, but others are available.

• The addition of nitromethane in fuel provides more power, and a smoother idle, thus making the engine easier to tune. The nitro also makes an engine run hotter, therefore, the amount of nitro added to a fuel results in a tradeoff. Common nitro mixes for helicopter use are 15% and 30%, but others are available.

• The front most portion of the helicopter. This term is primarily used in reference to the helicopters orientation in relation to the pilot. An example: Nose in refers to the helicopter facing the pilot, a tricky position due to the reversal of the cyclic commands, as opposed to tail in which has a more natural feel.

• The orientation of the helicopter when the nose is facing the pilot. This can be a confusing state, as the cyclic controls will be reversed in this position.

• Pulse Code Modulation. A modified FM signal used in high end radios. The signal is coded by the transmitter, resulting in a cleaner signal.

• Pulse Position Modulation. Another term for FM.

• Used on the Hiller control system. Two paddles are mounted on either end of a fly bar to aid in the control of the rotor disk.

• This is designed to work with the principal of Gyroscopic Precession.

• This is the point at which a battery will no longer accept a charge, and converts the energy to heat. This is damaging to the battery pack, and potentially hazardous.

• This type of charger will eliminate the guesswork. When the battery has reached peak, the charger reverts to a maintenance charge rate, which will not damage the pack.

• The helicopter spins in place through one or more revolutions.

• Describes the fore and aft attitude of the helicopter.

• The angle of attack of a given airfoil.

• The programming function of the radio which aids in setting the hover point, and end points of the blade pitch in the collective mix.

• Device used to measure the pitch of the rotor blades.

• Device designed to aid in the balancing of model airplane propellers. Can be used to balance small rotating items on the helicopter, such as cooling fans and tail rotor assemblies.

• A linkage set up using two rods. One rod pushes, while the other pulls.

• This describes the direction and speed of wind on the rotor disk.

• 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. Keep in mind that a helicopter has many rotating parts, and they all cause resonance. The helicopter will need to be tuned to reduce the amount of resonance, and the vibration caused by resonance. While this cannot be eliminated, the vibrations can be tuned individually to reduce the overall vibration of the helicopter.

• A condition possible in FFF which causes the retreating blade to fail to generate lift.

• The function of the radio which mixes throttle to rudder, preventing the rotation of the helicopter during throttle increase or decrease.

• An engine which uses a piston with a piston ring. Compare to ABC or ABN. Best used in dusty environments, a ringed engine is less susceptible to damage from contaminants in the fuel/air mixture, but does not provide the higher compression ratio of the ABC/ABN engines.

• Describes the attitude of the helicopter from side to side.

• This term describes the rotor used to generate lift in helicopter design. The blades spinning around a central point form a rotary wing, or rotor disk. By manipulating the amount of pitch in the blades at certain points of the disk, lift is directed in order to move the helicopter in a desired direction.

• The term used to describe the airspeed over different points of the blade structure.

• The shape of the rotary wing formed by the spinning blades.

• The airflow resulting from a spinning rotor. Similar to prop wash in an airplane.

• The yaw of the aircraft is controlled by the rudder function. On a helicopter, this is controlled by the speed and pitch of the tail rotor blades.

• In radios with idle up functions, this specifies the amount of tail rotor pitch in the different idle up conditions.

• Abbreviation for receiver.

• A solid axle head design. The two blades are connected by a feathering shaft. When one blade moves up, the other moves down.

• The radio component which does the work of moving a control surface.

• This describes the condition reached when descending from a hover and entering the helicopters down wash. This condition will result in a faster rate of decent.

• A computer program which uses a modified radio transmitter, and a graphic depiction of a helicopter and flying area. This is used to give helicopter pilots a feel for flying, without the risk of a crash. The simulator can be used by the newcomer to learn to hover, or by the expert to dial in that new 3D routine without crashing a very expensive 3D helicopter.

• The rail type landing gear used on many helicopter models.

• Slop occurs when a control surfaces movement does not move the servo. Common cause is a worn linkage point.

• Helicopters have two stabilizers, the horizontal and vertical, which are mounted on the tail. The stabilizers help the helicopter to weathervane, or point nose into the wind.

• This is the point at which an airfoil fails to produce lift.

• The maneuver in which the helicopter is flown to a point at which the rotor disk is vertical, the helicopter reaches an apex, then is turned about the yaw axis to continue in a nose forward attitude, then is given aft cyclic to return to horizontal flight.

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

• This is the ring positioned on the mast under the main rotor, which allows the pitch of the blades and paddles to be adjusted while the rotor is spinning.

• Abbreviation for tail rotor.

• The programming function of the radio which aids in setting the hover point, and end points of the throttle in the collective mix.

• A radio function which locks the throttle at a fixed point while a switch is activated. This function is used to hold the throttle in an idle. Useful when starting, as well as for auto rotations.

• The force which tends to cause rotation.

• A device used to expand the footprint of the helicopter, used for low level maneuvers. This will help to prevent the helicopter from tilting too far while learning to take off and land, and learning low level hovering.

• This describes the tendency of the main rotor blades to fly in an independent plane of travel. When the blades follow the same path of flight, the blades are tracking. This can be seen from the side of the helicopter while in a hover. One blade path should be visible. If the blades have the appearance of a ><, The blades are out of track. By adjusting the linkage of the pitch of one blade to match the other, tracking is dialed in, and the blades will appear thus --.

• The colored tape wrapped around the rotor blade, near the tip, to distinguish one blade from another. The contrasting colors of the blades will show when adjusting the tracking. Can also be used for balancing the blade. The tape is wrapped around the light blade to bring its weight up to equal that of the heavier blade. By adjusting the position and amount of tape, the C.G. of the blades can also be matched.

• The rotor is more efficient in forward flight than in a hover. Thus, when transitioning from hover to forward flight, additional lift is produced.

• The wobble effect experienced during the transition from hover to slow forward flight, and from forward flight to hover.

• The force used to hold the tail rotor in position creates side thrust, which will tend to slide the helicopter in the opposite direction. This is corrected with cyclic input.

• The effect which the leading edge of the rotor disk has upon the trailing edge during slow forward flight. This effect will cause a vibration in the helicopter.

• Abbreviation for transmitter.

• The twist in an airfoil.

• This describes the tendency to point into the wind. Helicopters are designed to weathervane.

• This term describes the sound that helicopter blades sometimes make. A full size helicopter, with a rotor head speed much slower than a model, but larger blades, has a distinctive sound.

• This can be used to describe a number of devices, all of which give a visual clue to the direction and speed of wind in a given location.

• The rate of movement about the vertical axis of a helicopter.

• Movement about the vertical axis of the helicopter.

• A type of linkage point using a bend in the control rod which resemble a Z.