RC Glossary

The introduction of spread spectrum technology into the world of radio control is without doubt one of the most important advances to occur in the history of the hobby.

The last major shake up of radio control systems was the introduction of Pulse Code Modulation (PCM), somewhere back in the 1980s, which allows the analogue signals being sent out from a standard FM transmitter to be converted to digital signals. This results in a stronger, more positive signal with less chance of interference either from other rc transmitters or 'metallic noise', whereby two metal surfaces inside the model rub together, generating a weak electronic signal that gets picked up by the receiver, causing unwanted servo movement.

Before recent years, RC flyers were on the 72MHz frequency band (and their transmitters all had long antennas with a flag at the tip to help judge wind direction). The problem with this is you had to make sure you were on a different "channel" as any other flyer or bad things would happen.  Like, as in, very, very bad things.  Think instant loss of control and crash.

But spread spectrum rc technology uses a completely different method of signal transmission and operates within the 2.4GHz frequency band, which is well clear of any of the other bands used for rc and other common radio signal transmissions.  This allows flyers to enjoy flying in confidence without fear of another flyer disrupting their precise "channel" no matter how many flyers you can stuff into one flying field.  It just doesn't happen with 2.4GHz technology.

This new technology for rc use has been developed from Direct Sequencing Spread Spectrum, a form of secure radio signal transmission that has been in use by top government bodies (military, NASA etc.) for a while. The rc version is fundamentally the same, but it's been tweaked a bit for the hobby industry.

3D refers to a complex form of advanced aerobatic flying. 3D airplanes have over-sized control surfaces, exaggerated control surface deflection and excess power for maximum performance and sensitivity. Many 3D maneuvers are performed at very slow speeds, often with the plane at the point of stall.

Adverse yaw is a term used when the nose of the plane isn't quite pointing in the direction it should be pointing in, as the plane turns. For instance, if you bank left into a turn the nose yaws to the right. A more visually obvious sign of adverse yaw is the tail end of the plane dropping (side-slipping) during the turn.

This adverse yaw occurs because a downward deflected aileron (i.e. the aileron on the outer wing during the turn) causes more drag than the upward deflected aileron, and this drag tries to pull the airplane in the opposite direction of the turn. 

For example, if the plane is in a banked turn to the right, there's increased drag on the left hand wing (because of the down aileron) which causes an unwanted yaw to the left, even though the plane is turning to the right.

Aerobatic refers to any maneuver or series of maneuvers that involve stunts of any kind, such as loops, rolls and spins. An airplane that is capable of performing such stunts is said to be "fully aerobatic".

Aft in aviation refers to the back or rearward area of an aircraft, or behind the object in question.

"This airplane's baggage compartment is aft of the CG."

A hinged flight control surface usually attached to the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll, or movement around the aircraft's longitudinal axis. Movement around this axis is called 'rolling' or 'banking'. Usage of ailerons and the elevator help to complete a turn. On basic aircraft without ailerons, rudder is used to turn the aircraft along its lateral axis. 

Aileron Differential is when the ailerons are set up to move upwards more than downwards, to counteract any adverse yaw during a turn caused by extra drag on the outer wing from the down aileron. Aileron differential simply means that the ailerons move more in one direction than the other, with the greater deflection being upwards. Ailerons that are set up this way are called differential ailerons.

Adverse Yaw

The reason why ailerons are sometimes set up this way is to counteract any adverse yaw when the airplane is turning.

Adverse yaw is a term used when the nose of the plane isn't quite pointing in the direction it should be pointing in, as the plane turns. A more visually obvious sign of adverse yaw is the tail end of the plane dropping (side-slipping) during the turn.

This adverse yaw occurs because a downward deflected aileron (i.e. the aileron on the outer wing during the turn) causes more drag than the upward deflected aileron, and this drag tries to pull the airplane in the opposite direction of the turn.

For example, if the plane is in a banked turn to the right, there's increased drag on the left hand wing (because of the down aileron) which causes an unwanted yaw to the left, even though the plane is turning to the right.

The correct fix for this common issue is to apply a small amount of rudder during the turn in co-ordination with the aileron deflection. It's how real planes are flown and is known as 'coordinated flying'. The deflected rudder forces the nose of the plane round in the direction it's turning, thus acting against the drag and so no tail-drop is seen. 

Rudder can be applied manually during the turn (by using the rudder stick!) but a very easy and convenient fix if you have a computer-based transmitter with channel mixing capability is to mix rudder with aileron, so a small amount of rudder is automatically applied when you move the aileron stick.

Setting up some aileron differential is the other fix, particularly if you have an airplane that has a strong tenancy to drop its tail during a turn - some planes do it more than others - and especially if you're flying a plane without rudder control (i.e. aileron & elevator only).

Most computer radios offer an aileron differential programming option if each aileron has its own servo - refer to your transmitter instruction manual for the 'How to...' part. This is the easy fix!

In aeronautics, air brakes or speedbrakes are a type of flight control surface used on an aircraft to increase drag or increase the angle of approach during landing.

Air brakes differ from spoilers in that air brakes are designed to increase drag while making little change to lift, whereas spoilers reduce the lift-to-drag ratio and require a higher angle of attack to maintain lift, resulting in a higher stall speed.

An airfoil is the cross-section shape of a wing. Airfoils can be flat-bottomed, under-cambered, semi-symmetrical or symmetrical, depending on the style of airplane and what it needs to do. Different shape airfoils have different lift generating properties.

The Angle of Attack refers to the angle between the chord line of the wing of a fixed-wing aircraft and the vector representing the relative motion between the aircraft and the atmosphere. Since a wing can have twist, a chord line of the whole wing may not be definable, so an alternate reference line is simply defined. Often, the chord line of the root of the wing is chosen as the reference line.  

Critical Angle of Attack

The critical angle of attack is the angle of attack which produces maximum lift coefficient. This is also called the "stall angle of attack". Below the critical angle of attack, as the angle of attack increases, the coefficient of lift (Cl) increases. At the same time, above the critical angle of attack, as angle of attack increases, the air begins to flow less smoothly over the upper surface of the airfoil and begins to separate from the upper surface.

On most airfoil shapes, as the angle of attack increases, the upper surface separation point of the flow moves from the trailing edge towards the leading edge. At the critical angle of attack, upper surface flow is more separated and the airfoil or wing is producing its maximum coefficient of lift. As angle of attack increases further, the upper surface flow becomes more and more fully separated and the airfoil/wing produces less coefficient of lift.

An ARF simply means an aircraft that requires your own choice of electronics to install in the airframe.  Most ARF's require you to purchase all of the electronics separately (motor, servos, ESC, and sometimes additional accessories).  ARF's are for folks who either prefer a true build process and/or prefer to put their own choice of electronics in the aircraft.

For fiberglass and balsa airplanes from companies like Great Planes, ARF has a different meaning.  For these planes, ARF is used to describe an airplane kit which is pre-built (the wings, fuselage, and stabilizers are fully constructed and covered in Monokote or painted, etc.) but does not include servos, ESC, or a propeller / EDF. Like the foam ARF, these kits also do not include a radio, receiver, battery or battery charger. 

The TechOne ARF BUNDLE airplane requires intermediate level building skills. Some included components such as servos and motors do not come pre-installed and will need to be installed during the build process. Detailed building instructions are included with each model, however an adhesive product would be required such as a Foam Safe CA or FoamTac glue.

Freewing offers some of its 90mm jets in "ARF Plus" format. Expanding on the normal ARF format above, The ARF Plus format has ALL components installed already, EXCEPT for the motor, EDF unit, and ESC/UBEC. All other components, from the retracts to the servos and lights, are factory installed. The ARF Plus format allows pilots to obtain nearly ready-to-fly jets with most of the components installed, but gives those pilots the option of experimenting with installing their own custom power system, without the need of installing servos and doing the extensive plumbing of servo wires.

This refers to an aerobatic maneuver that involves the airplane following the twist of a large imaginary corkscrew (horizontal) through the air by way of rolling the aircraft.

Battery Eliminator Circuits are small devices that eliminate the need for a receiver and servo battery pack. They draw higher voltage from the motor batteries and drop it to a voltage level that is suitable for your receiver and servos. This is required in applications which draw high power for multiple servos or use more than 3S motor packs, as most ESCs with linear BECs are not designed for these applications.

a 2.4GHz receiver needs to be 'bound' to the transmitter before it can receive signals from it. The process involves the Rx identifying a unique code being emitted from the Tx, and then the two components lock together on an available frequency. The process usually only takes a few seconds.  Every flyer who binds a 2.4GHz radio and receiver are immediately given their own unique code that is as unique as a fingerprint.  This ensures that the flyer will never have a conflict with any other flyer's code.

Imagine 100 flyers all using 2.4GHz radios and receivers flying at the same time at the same field (must be a really big flying field!) without any interference.  That's the beauty of 2.4GHz.

Bind N' Fly airplanes/quads/helis already come with a receiver so all that is required is for you to bind the receiver to your radio.  It is important to make sure that the receiver that comes with the model is compatible with your radio.  For instance, if you have a Spektrum transmitter, only a Spektrum receiver will be able to bind it to an aircraft compatible with Spektrum receivers.  Most radios and receivers are proprietary and only work together.

Hobbico produces many "TXR" Transmitter Ready aircraft, which are essentially the convenience of a BNF since the pilot just needs to add their compatible Hobbico/Tactic brand radio. Horizon Hobby produces a wide lineup of aircraft sold in the BNF format under the sub-brands "Eflite" and "Parkzone". These aircraft are convenient additions to a pilot's fleet, eliminating the added cost of purchasing a new radio with each new aircraft.

Brushless motors have almost completely replaced brushed motors in the RC industry. Their superior power and efficiency make them the obvious choice for powering your RC aircraft.  Here’s what you need to know to use them, and some helpful info on how they work.

Brushless Motor Benefits

Before going into how brushless motors work, here’s why they’re useful:

• More Efficient – Brushless motors are much more efficient than conventional brushed motors. This efficiency has been measured to be between 85% to 95% better than brushed motors.
• Less electrical energy is wasted as heat, and more is used to do useful work.
• Reduced Noise – Brushless motors have fewer mechanical parts than brushed motors, so they emit less sound.
• Longer Lifetime – Fewer moving parts are in mechanical contact than in brushed motors, reducing wear.
• Reduced EM Interference – Brushless motors emit less energy as electromagnetic (EM) waves than brushed motors do. This contributes to their efficiency, and helps reduce radio interference.
• Torque, Voltage, And RPM Linearly Related – This means that the amount of torque or RPM produced by the motor divided by the voltage put in is a constant, making it easy to predict how much power you’re going to get.

How Brushless Motors Work

On a fundamental level, an electric motor’s only job is to convert electrical energy (like that provided by a battery) into mechanical energy, like the turning of a propeller or rotor blade. There are two basic facts that allow electric motors to work:

1. Electric and Magnetic Fields are Related - That is, every moving charge produces a magnetic field, and magnetic fields can produce electric charge.
2. Magnets Interact – Magnets will align when placed near to each other. All electric motors basically consist of two magnets. One of them is permanent, the other is a coil of wire that, when charged, becomes a magnet.

The motor is designed such that the magnetic fields produced by each of the magnets are always out of alignment, causing the motor axil to rotate. This is similar to what happens when you hold a permanent magnet to a compass – the compass swings position so that it lines up with the magnets field.

With the brushed motor design, the magnetic fields are kept out of alignment by turning on the different coils of wire that surround the motor axil in succession. Metal brushes make mechanical contact with the rotating axil and the contacts with each metal coil. As the axil rotates, the brushes contact different coils. The end result is that current flows through different coils at different times, constantly changing the magnetic field and rotating the motor shaft.

It’s here that we see the main problem with the brushed design: the contact between the motor coils and the brushes causes friction, which increases with speed. The metal coils wear out over time, and are prone to sparking. They can also ionize surrounding air, creating ozone. So how can we get around these issues? The answer lies in the brushless motor design. Instead of using mechanical brushes to turn on the various wire coils, an ESC (electronic speed controller) is used instead. The ESC switches the motor coils on or off rapidly, and is synchronized to the motor axial position.

Always look for an ESC with a capacity (measured in amps) greater than that of the motor you’re pairing it with.

Some Common Terms Explained

There are a number of special terms associated with brushless motors. Here are explanations for some of the most common:

• RPM – This is a measure of angular speed, or how fast something is rotating. A motor’s RPM is simply how fast it can rotate.
  
  
• Kv Rating - Remember how we said that the relationship between voltage, torque, and RPM was linear for a brushless motor? It turns out that the number of RPM provided by each volt is the same, called  the Kv number. The Kv number’s useful because it let’s you figure  out how many volts you need to achieve a certain RPM, or vice versa.  For an example, a 980 Kv motor powered by an 11.1 volt battery would spin at 980 x 11.1 = 10878 RPM with no load. The Kv rating always assumes no load on the motor, so the actual RPM that your achieve  will be less than the one you calculate.
  
  
• Continuous / Burst Current – Continuous current measures how much current a motor can handle continuously, for an extended period of  time. Burst current measures how much current a motor can handle for a short amount of time, about a few seconds.
  
  
• Current Rating – This is the maximum current that a given motor can handle, measured in amps.
  
  
• Inrunner / Outrunner – These are the two major brushless motor  designs. An inrunner brushless motor has stationary coils, and a rotating permanent magnet inside the coils on the motor shaft. An outrunner brushless motor is the opposite, it has a rotating permanent magnet, placed outside the stationary coils on the motor shaft . Outrunner motors have lower Kv ratings, so they run at a lower speed with more torque. This could allow you to direct drive larger props without a gearbox. RC cars and boats tend to require inrunner brushless motors, rather than outrunners.
  
  
• Torque - Torque is a measure of angular force, or how much “push” a rotating shaft has.  
  
  
• Watt – This is a measure of power, or how fast energy is used.
  
  
• Volt – This measures electric potential, or how much “push” the electrons from a battery have. A greater voltage means that more energy is being applied to a given amount of charge.

A Buddy Box is one of the best training aids, where the student's transmitter is attached via cable (or wireless for newer radios) to the instructor's. The student has complete control over the airplane, but at the flick of a switch the instructor can take control if the student gets into a situation that may result in loss of aircraft.

The Bulkhead is the foremost former of your airplane on to which the engine is mounted. Also called a firewall.

Cyanoacrylate (CA for short) is the generic name for a family of fast-acting adhesives, sometimes referred to as "Super Glue." CA comes in three varieties: thin, medium, and thick.  These terms refer to the viscosity and gap filling properties of the glue.  Thin CA is used to join materials which are tight fitting.  Medium CA has minor gap filling properties and is a good all-around choice for hobby use.  Thick CA can be used to fill larger gaps and is slightly more flexible than the thin and medium weight products.

IMPORTANT - if you are using CA for foam airplanes, make sure to use a "Foam Safe CA" as some foams will melt / deform if general purpose CA is applied to their surface.

CG is short for Center of Gravity. In reference to radio controlled aircraft, the CG is the ideal balance point for your aircraft to achieve level, stable flight in normal conditions. Each manufacturer will provide a recommended CG in their user manual as a starting point of reference. Some more advanced flyers prefer their plane not to be in perfect balance, and will add more weight to the aircraft to make it “tail heavy” or “nose heavy” depending on their preference.

Channel mixing is when two separate channels are made to operate in conjunction with one another. For example, you could program an aileron and rudder mix whereby the rudder automatically moves a set amount when the ailerons are deflected. Or you could have elevators automatically drop when flaps are activated.

Continuous current measures how much current a motor or battery can handle continuously, for an extended period of time. Burst current measures how much current a motor or battery can handle for a short amount of time, about a few seconds.

This is a plastic or metal piece that is attached to a control surface, onto which the servo linkage is connected to by way of pushrod and clevis.

The control surface on an aircraft is the term used to describe the moving part of any flying surface such as the rudder, elevator and ailerons.  These are all control surfaces.

Something that is possible on a computer-based transmitter only, control surface mixing is a single pair of control surfaces made to act as two separate pairs would. A common example of control surface mixing is to combine elevator and aileron deflection into 'elevons', on a flying wing type rc aircraft such as the F-117, B-2 Spirit or any delta or flying wing.

In this case, the transmitter is operated normally but the single pair of control surfaces combine the two different deflections in accordance with the Tx stick movements and so move together, as elevators do, and individually as ailerons do. Other similar control surface mixing includes flaperons (mixing aileron & flap deflection) and spoilerons (mixing aileron & spoiler deflection).

A crosswind is when the wind is blowing at, or approximately, 90 degrees to your line of flight, take off or landing.  A crosswind takeoff or landing is more challenging as you have to negotiate the proper control surfaces to compensate for the crosswind.

Crow is a name given to a type of air-braking method common on rc gliders, whereby the flaps go down and the ailerons go up simultaneously. The lowered flaps create high drag, while the raised ailerons reduce lift, this combination makes landing a fast glider more easy.

Discharge rate is simply how fast a battery can be discharged safely. In the RC LiPo battery world it is called the “C” rating. A battery with a discharge rating of 10C would mean you could safely discharge it at a rate 10 times more than the capacity of the pack, a 15C pack = 15 times more, a 20C pack = 20 times more, and so on.  

Let's use a 1000 mAh battery as an example; if it was rated at 10C that would mean you could pull a maximum sustained load up to 10,000 milliamps or 10 amps off that battery (10 x 1000 milliamps = 10,000 milliamps or 10 amps). From a time stand point, this equals 166 mAh of draw a minute so the 1000 mAh pack would be exhausted in about 6 minutes. 

Most RC LiPo Battery packs will show the continuous C rating and some are now indicating a burst rating as well. A burst rating indicates the battery discharge rate for short bursts of extended power. The higher the C rating, usually the more expensive the battery. This is where you can save some money. Getting an extremely high discharge rated pack when there is no way you could possibly pull the full amount of power is not required. The most important thing is you can't go with too low a discharge C rating or you will damage your battery and possibly your ESC (electronic speed control). As a very general guide line, 25C to 30C discharge rated packs are the norm for most RC aircraft.

Dead Stick is commonly referred to when your airplane's motor cuts out unexpectedly in mid-air. With any luck you'll have enough altitude to glide safely in for a nice landing. Sometimes pilots will "dead stick" their airplane by dropping their throttle to idle on purpose in the event they need to lower airspeed on final approach or bleed off airspeed in order to land before running out of runway.

This is usually due to being too "High and Hot", a term for having a glideslope too high for a normal landing, at an airspeed too fast to make the target touchdown area.

Dihedral is the upward angle of the wings when viewed from the front. An airplane with dihedral is more stable in the air than one without. Both high-wing and low-wing airplanes may have dihedral to help with overall stability.

Drag is the force that is created by the movement of the airplane through the air, on the air immediately surrounding the plane. Higher drag means that the plane has to work harder to cut through the air.

This refers to a type of technology developed by Spektrum for their spread spectrum 2.4GHz rc systems. Stands for Digital Spectrum Modulation, the '2' and the 'X' just being the updated versions of the original. Just one of many branded abbreviations for particular 2.4GHz rc technology names.

Dual rates enable the control surface deflection limits to be changed, while still retaining full stick movement. So you could have 'high' deflection (or "High Rates"), plus a setting for decreased deflection limits at full stick movement (or "Low Rates").

Most flyers prefer to setup dual rates so they can enjoy maximum movement (for 3D or aerobatics as an example) or a lower setting for easier control of a "twitchy" aircraft, or for the takeoff and landing sequence.  

An Elevator is the flight control surface usually at the rear of an aircraft, which control the aircraft's orientation by changing the pitch of the aircraft, and so also the angle of attack of the wing. In simplified terms, they make the aircraft nose-up or nose-down.

When elevator and aileron control is made by the same control surface, this surface is called an elevon. Only possible with a channel mixing option on the transmitter.  Elevons are common on delta-wing aircraft such as "flying wings", the F-117, B-2 Spirit, etc.

The empennage (em-puh-nage) also known as the tail or tail assembly, of most aircraft gives stability to the aircraft, in a similar way to the feathers on an arrow; the term derives from the French for this. Most aircraft feature an empennage incorporating vertical and horizontal stabilizing surfaces which stabilize the flight dynamics of yaw and pitch, as well as housing control surfaces.

An electronic speed control or ESC is an electronic circuit with the purpose to vary an electric motor's speed, its direction and, in some cases, act as a dynamic brake. An ESC can be a stand-alone unit which plugs into the receiver's throttle control channel or incorporated into the receiver itself, as is the case in some micro or RTF aircraft.

Many aircraft 24" or larger in wingspan use ESCs with an integrated BEC. The BEC powers the receiver and servos, via the same throttle wire coming out of the ESC which is plugged into the Throttle channel on your receiver. This is a convenient way to power your receiver and servos, without the need for a receiver battery. Receiver batteries are still used in the RC hobby, primarily for liquid fuel powered aircraft, or larger electric aircraft above 7-8 pounds in weight.

Expo lets you reduce (or increase) control surface movement around the central stick movements, effectively making the control surface movement disproportional to your stick movements. This is a way to "soften" the stick sensitivity around center.  This helps the aircraft be less "twitchy".  You still have the full range of control input from the edges, just that the area around center is softened to decrease sensitivity so your aircraft doesn't look like it consumed too much coffee that morning.

Flaperons is a single control surface on the trailing edge of each wing that does the job of flaps and ailerons. An rc system with control mixing capability is needed to have flaperons.  Used commonly on rc sailplanes but can be mixed for most any aircraft to increase lift/drag to slow the aircraft and lower the stall speed.

Flaps are devices used to alter the lift characteristics of a wing and are mounted on the trailing edges of the wings of a fixed-wing aircraft to reduce the speed at which the aircraft can be safely flown and to increase the angle of descent for landing. They shorten takeoff and landing distances. Flaps do this by lowering the stall speed and increasing the drag.

Extending flaps increases the camber or curvature of the wing, raising the maximum lift coefficient — the lift a wing can generate. This allows the aircraft to generate as much lift, but at a lower speed, reducing the stalling speed of the aircraft, or the minimum speed at which the aircraft will maintain flight. Extending flaps increases drag, which can be beneficial during approach and landing, because it slows the aircraft. On some aircraft, a useful side effect of flap deployment is a decrease in aircraft pitch angle which lowers the nose thereby improving the pilot's view of the runway over the nose of the aircraft during landing. However the flaps may also cause pitch-up depending on the type of flap and the location of the wing.

Flaring is the action taken in the last few seconds of the landing approach, right before touchdown, to reduce the approach angle and slow the rate of descent.

The flare is crucial in "softening the blow" to the wheels and struts and the rest of the airplane.  Hard landings from a lack of flare can stress or fracture components and the airframe itself.  

Fore in aviation refers to the front or foreward section of an aircraft.  

"The firewall is fore of this airplane's CG".

The fuselage is the main body of an airplane, excluding wings, tail and everything else.

This is the tendency of a spinning object to precess or move about its axis when disturbed by a force. The engine and propeller act as a big gyroscope. However, gyroscopic precession is likely to be minimal in a typical aircraft.

Gyroscopic precession is frequently confused with p-factor.

Hand launching or hand tossing is the way to launch any flying aircraft without landing gear. The model should be held level at the bottom of the fuselage close to the aircraft's CG at head-height and launched into wind with a slight high Angle of Attack. Velocity of the toss is proportional to how powerful the aircraft's power system is.

Under-powered EDF jets will need a harder toss than say a propeller-driven plane with a light wing load.

Also called the tailplane. The horizontal surface at the back of the fuselage, to which the elevators are attached. It's a tailplane's job to generate a downward force, to counteract the natural tendency for a plane to want to nose-dive into the ground. 

These are the two major brushless motor designs. An inrunner brushless motor has stationary coils, and a rotating permanent magnet inside the coils on the motor shaft. An outrunner brushless motor is the opposite, it has a rotating permanent magnet, placed outside the stationary coils on the motor shaft .

Outrunner motors have lower Kv ratings, so they run at a lower speed with more torque. This could allow you to direct drive larger props without a gearbox. EDF jets tend to require inrunner brushless motors, rather than outrunners.

The only non-acronym in the list, a kit simply means an aircraft that requires your own choice of electronics to install in the airframe.  Most kits require you to purchase all of the electronics separately (motor, servos, ESC, and sometimes additional accessories).  Kits are for folks who either prefer a true build process and/or prefer to put their own choice of electronics in the aircraft.

Freewing offers some of its 90mm jets in "KIT+ format, also known as "KIT PLUS". Expanding on the normal KIT, The KIT+ format has ALL components installed already, EXCEPT for the motor, EDF unit, and ESC/UBEC. All other components, from the retracts to the servos and lights, are factory installed. The KIT+ format allows pilots to obtain nearly ready to fly jets with most of the components installed, but gives those pilots the option of experimenting with installing their own custom power system, without the need of installing servos and doing the extensive plumbing of servo wires.

Kv rating (not to be confused with kilo-volt) is the RPM of the motor (k) per volt (V) with no load. For example, a brushless motor with a Kv rating of 3000 powered by a 12V power source would be capable of 36,000 RPMs (multiply 3000x12). This is the max RPMs that this motor can reach under no load. A motor with a higher Kv will have more top end speed, but not as much acceleration/torque. A motor with a lower Kv will not be as fast, but will accelerate faster.

In rc flying, landing gear is the portion under the airplane that is allows the airplane to land on wheels.  This may include struts, wheels, retracts, tail wheel and their associated mechanisms.

Landing gear can be fixed or retractable up into the underside of the wing or fuselage (called 'retracts', usually only found on planes with 5 channels or more).

The leading edge refers to the front edge of the wing, horizontal stabilizer, rudder or any control surface.

Lithium Polymer or Lipo batteries are the standard rechargeable battery type used in today's RC products. LiPo's have significant benefits over Nickel-metal Hydride (NiMH) or Nickel-cadmium (NiCd) including lighter weight, increased run time, and higher number of charge cycles. The nominal voltage of each LiPo cell is 3.7V.  Here are the nominal voltages of the most popular size LiPo batteries:

LiPo Nominal Voltage (Resting)

1 Cell (1S) 3.7V
2 Cell (2S) 7.4V
3 Cell (3S) 11.1V
4 Cell (4S) 14.8V
6 Cell (6S) 22.2V

While the nominal voltage is the standard voltage labeling on most LiPo batteries, the maximum voltage of LiPo batteries is an important data point which shows you when you batteries are fully charged. Your battery charger will typically cutoff it's charge cycle when it reaches the maximum voltage of each LiPo cell; 4.2V per cell. Here are the maximum voltages of LiPo RC batteries:

LiPo Maximum Voltage (Fully Charged)

1 Cell (1S) 4.2V
2 Cell (2S) 8.4V
3 Cell (3S) 14.8V
4 Cell (4S) 16.8V
6 Cell (6S) 25.2V 

An aerobatic maneuver where the airplane flies a vertical circle in the air. The easiest stunt of all to pull off, and any airplane with an elevator can do them.  The main thing to remember is to perform the maneuver high enough so the airplane doesn't hit the ground coming out of the loop.  (That would be bad).

Loss of Orientation is when you lose sight of which way up your rc airplane is and what it's doing, either because it's too far away to see properly, doesn't have a paint scheme that is easy to tell top or down orientation or because of low light levels, or you've just flown it directly over your head and momentarily lost all visual reference to everything. It happens to all rc pilots from time-to-time and is not the best feeling to have in the hobby.

Mixing is the ability to combine two different rc functions into one. See Control Surface Mixing and Channel Mixing.

Mode 1 refers to the set-up of the transmitter where the left stick operates the elevator and rudder, and the right stick operates the throttle and ailerons. This is a less-common mode for transmitter layout.  See Mode 2 for the typical setup.

Mode 2 refers to the set-up of the transmitter where the left stick operates the throttle and rudder, and the right stick operates the elevator and ailerons. This is the most common transmitter mode.

Moment is the tendency of an object to rotate or pivot about a point. The further an object is from this point, the greater the force it exerts.

Non-scale refers to any model aircraft that is not modeled from a real-life aircraft.  Non-scale aircraft are made up designs.

Sometimes you may find the need to connect more than one Li-Po battery together in your aircraft.  There are two primary methods to connect more than one Li-Po battery to your aircraft.  It is important to learn the difference between the two.  You are either trying to double the voltage while maintaining the same capacity rating or double the capacity while maintaining the voltage of one of the batteries.

Connecting in Parallel 

When connecting in Parallel you are doubling the capacity (amp hours) of the battery while maintaining the voltage of one of the individual batteries. This would be used in aircraft you are wanting to increase the mAh, or time you have to fly. Two 3S 2200 mAh Li-Po batteries in Parallel will be giving you the equivalent of a single 3S battery with 4400 mAh capacity, to in theory double your flight time.  Use a jumper wire between the positives of both batteries and another jumper wire between the negatives of both batteries. Connect your positive and negative wires to the same battery to run to your application. 

Connecting in Series 

When connecting your batteries in Series you are doubling the voltage while maintaining the same capacity rating (amp hours). This might be used in a larger-sized EDF jet where you wish to bump up from a 6 Cell setup to perhaps an 8 Cell setup.  In this example you would connect a 6 Cell with a 2 Cell in Series. Just use a jumper wire between the negative of the first battery and the positive of the second battery. Run your negative wire off of the open connector from the first battery and your positive off of the open connector on your second battery.

Park Flyers are rc electric model aircraft that are in the smaller-sized class that are safe to fly in areas like parks, schools and parking lots.

Micros, small jets, 700-1200mm aircraft typically fall into this category.  In some cases 1400mm aircraft can be considered park flyers but generally the larger and more powerful the aircraft, the less likely you can fly it in smaller spaces.

P-factor is the term for asymmetric propeller loading, that causes the airplane to yaw to the left when at high angles of attack.

Assuming a clockwise rotating propeller it is caused by the descending right side of the propeller (as seen from the rear) having a higher angle of attack relative to the oncoming air, and thus generating a higher air flow and thrust than the ascending blade on the left side, which at the other hand will generate less airflow and thrust. This w