Radio Controlled Aircraft

Radio-controlled aircraft (also called RC aircraft) are small model aircraft that can be controlled remotely. They use radio control with a hand-held transmitter and a receiver within the craft. The receiver controls the corresponding servomechanisms that move the control surfaces based on the position of joysticks on the transmitter, which in turn maneuvers the plane.

RC planes as a hobby has been internationally growing due to the availability of smaller, relatively inexpensive parts and advancing technologies. A variety of models and styles are available to suit any preference or budget. Due to the availability and advances in high performance electric batteries and motors, a growing number of hobbyists are flying electric powered craft instead of fuel (most often methanol or gasoline based) powered craft, because of their ease of construction and the absence of fuel mess and fuss.

Scientific, government and military organizations are also utilizing RC aircraft for experiments, gathering weather readings, aerodynamic modeling and testing, and even use them as drones or spy planes.

There are many types of radio-controlled aircraft. For beginning hobbyists, there are park flyers, and trainers. For more advanced pilots there are glow plug engine, electric powered and sailplane aircraft. For expert flyers, jets, pylon racers, helicopters, 3D aircraft, and other high end competition aircraft provide adequate challenge.

A distinction is typically made between hobby grade and toy grade model aircraft. Toy aircraft are exclusively electric, have less power, and require little skill to fly. As a result, they are much cheaper (less than $75 or so). Hobby grade aircraft come in all varieties, from small electrics, to multi-thousand dollar craft with hundreds of cubic centimeters "under the hood".

Park flyers, as the name implies, are small, easy to fly electric aircraft. They are designed with the average flyer in mind, requiring an area no bigger than a park to fly. They are low budget and easy to fly. Trainers are similar to park flyers in that they are on the docile side and are comparatively inexpensive, however, they are bigger and are usually glow (gasoline) engine powered.

These are larger aircraft, like scale and sport planes. They are usually more expensive.

There are many different types of sport aircraft. They range from simple "fun-fly" glow engine planes with wingspans of under 40 inches, to colossal aircraft that range from 25 to 50 percent of the full scale size, with engines with hundreds of cubic-centimeters (cc's) under the cowling.

Most sport aircraft are capable to some degree of performing aerobatics. Many "giant-scale" aircraft are capable of performing complex aerobatics, ranging from loops and rolls to multiple snap rolls and tailslides. Giant Scale aircraft are flown in world-class competition. Most world-class competitors' aircraft have wingspans between 2 meters and 3.5 meters, with 2 cycle gas engines of 50 to 250 cc's.

Gliders are planes that do not usually have any form of propulsion. As most gliders are unpowered, flight must be sustained through exploitation of the natural lift produced from thermals and wind hitting a slope.

Jets tend to be very expensive and commonly use a turbine or ducted fan to power them. These aircraft can often reach speeds in excess of 200 mph. They require incredibly quick reflexes and very expensive equipment, so are usually reserved for the expert.

Racers are small propeller aircraft that race around a 2, 3, or 4 pylon track. They tend to be hard to see and go over 150 MPH.

Radio-controlled helicopters, although often grouped with RC aircraft, are in a class of their own because of the vast differences in construction, aerodynamics and flight training. Hobbyists will often venture from planes, to jets and to helicopters as they enjoy the challenges, excitement and satisfaction of flying.

3D flight is a type of flying in which model aircraft have a thrust-to-weight ratio of more than 1:1 (typically 1.5:1 or more), large control surfaces with extreme throws, and relatively low wing loadings.

These elements allow for spectacular aerobatics such as hovering, 'harriers', torque rolling, knife-edge, and more, maneuvers that are performed below the stall speed of the model. The type of flying could be referred to as 'on the prop' as opposed to 'on the wing', which would describe more conventional flight patterns that make more use of the lifting surfaces of the plane.

3D has created a huge market for electric indoor 'profile' types similar to the Ikarus 'Shockflyers' designed to be able to fly inside a gym or outside in little wind. These generally make use of small brushless motors (often outrunners, but also geared inrunners) and lithium polymer batteries. There are also many larger 3D designs designed for two and four stroke glow engines, two stroke gas engines and large electric power systems.

There are various ways to construct and assemble an RC plane. Various kits are available, requiring different amounts of assembly, different costs and varying levels of skill and experience.

Some kits can be mostly foam or plastic, or may be all balsa wood. Construction consists of using formers and longerons for the fuselage, and spars and ribs for the wings and tail surfaces. More robust designs often use solid sheets of wood to form these structures instead, or might employ a composite wing consisting of an expanded polystyrene core covered in a protective veneer of wood, often obechi. Such designs tend to be heavier than an equivalent sized model built using the traditional method, and would be much more likely to be found in a power model than a glider. The lightest models are suitable for indoor flight, in a windless environment. Some of these are made by bringing frames of balsa wood and carbon fiber up through water to pick up thin plastic films, similar to rainbow colored oil films. The advent of "foamies," or craft injection-molded from lightweight foam and sometimes reinforced with carbon fiber, have made indoor flight more readily accessible to hobbyists.

Flying models have to be designed according to the same principles as full-sized aircraft, and therefore their construction can be very different from most static models. RC planes often borrow construction techniques from vintage full-sized aircraft (although they rarely use metal structures).

Ready To Fly (or RTF) planes come as pre-assembled kits that usually only require wing attachment or other basic assembly. Typically, everything that is needed is already in the kit. RTF planes can be up in the air in just a few minutes and have all but eliminated assembly time (at the expense of the model's configuration options.) Among traditional hobbyist builders, RTF models are a point of controversy, as many consider model assembly as integral to the hobby. Brands associated with these types of aircraft include Great Planes, Hobbico, E-Flite, Hangar 9, Grand Wing Servo-Tech, HobbyZone and ParkZone.

Almost Ready to Fly (or ARF or ARTF) kits are similar to RTF kits; however usually require more assembly and sometimes basic construction. The average ARF aircraft can be built with less than 4 hours of labor, versus 20-50+ (depending on detail and desired results) for a traditional kit aircraft. The fuselage and appendages are normally already constructed. The kit will usually require separate purchase and installation of servos, choice of motor (gas, or electric), speed controller (electric) and occasionally control rods. This is an advantage over RTF kits, as most model aircraft enthusiasts already own their equipment of choice, and only desire an airframe. Lanier RC is typically hailed as the first ARF manufacturer. Other brands associated with this type of aircraft are Carl Goldberg Products, Great Planes, and Sig Manufacturing.

Balsa kits come in many sizes and skill levels. The balsa wood may either be cut with a die-cut or laser. Laser cut kits have a much more precise construction and much tighter tolerances, but tend to cost more than die-cut kits. Die-cut kits can work and look just as good with a little sanding, cutting and use of basic woodworking principles.

The kit usually contains most of the raw material needed for an unassembled plane, a set of (sometimes elaborate) assembly instructions, and a few spare parts to allow for builder error. Assembling a model from plans or a kit can be very labor-intensive. In order to complete the construction of a model, the builder typically spends many hours assembling the frame, covering it, and polishing/refining the control surfaces for correct alignment. The kit does not include necessary tools, and these have to purchased separately. A single overlooked error during assembly could compromise the model's airworthiness, leading to disaster.

Smaller balsa kits will often come complete with the necessary parts for the primary purpose of non-flying modeling or rubber band flight. These kits will usually also come with conversion instructions to fly as glow (gas powered) or electric and can be flown free-flight or radio-controlled. Converting a kit requires additional and substitution parts to get it to fly properly such as the addition of servos, hinges, speed controls, control rods and better landing gear mechanisms and wheels.

Many kits will come with a tissue paper covering that then gets covered with mulitple layers of plane dope which coats and strengthens the fuselage and wings in a plastic-like covering. It has become more common to cover planes with heat-curing plastic films ("heat shrink covering" or "solarfilm") that can be ironed on - a hand-held iron causes the film to shrink and adhere to the frame. This plastic covering is more durable and makes for a quick repair. Other varieties of heat shrinkable coverings are also available, that have fibrous reinforcements within the plastic film, or are actual woven heat shrinkable fabrics.

It is common to leave landing gear off smaller planes (roughly 36" or smaller) in order to save on weight and construction costs. The planes can then be launched by throwing and can then land in soft grass.

Planes can be built from published plans, often supplied as full sized drawings with included instructions. Parts normally need to be cut out from sheet wood using supplied templates.

Hobbyists that have gained some experience in constructing and flying from kits and plans will often venture into building custom planes from scratch. This involves finding drawings of full sized aircraft and scaling these down, or even designing the entire airframe from scratch. It requires a solid knowledge of aerodynamics and a plane's control surfaces. Plans can be drawn up on paper or done with CAD software. Many CAD packages exist for the specific purpose of designing planes and perfecting airfoils.

The easiest planes to fly are typically ones that have a high wing, or a wing that is on top or above the plane's fuselage. Wing dihedrals (bend or change of angle in wing relative to fuselage) or polyhedrals are also common. Most trainers and park flyers have this configuration.

These planes hold most of their weight under the canopy of the wing structure and tend to react more like a glider. For this reason, they are very stable and easy to fly. If a high wing plane is out of control, stability can often be regained by returning the controls back to a neutral position, allowing the plane to naturally fall back into a gliding position. Because of the wing shape, wing position, and drag under the wing due to the fuselage, these planes fly slower than their mid and low wing counterparts, but can usually do some aerobatic maneuvers.

High wings are typical of many vintage private planes. For example, the Piper Cub and the Cessna 170.

Low wing planes offer a higher level of flying difficulty because the weight of the plane sits on top of the wing structure, making the balance a bit top heavy. Most wing configurations provide a slight dihedral to provide a bit more balance during flight.

The weight distribution and wing position of a low wing plane provides a good balance of stability and maneuverability. The plane's weight is easier to move around the rotation axis during a roll because it is closer to the wing, requiring much less leverage than a high wing plane.

Low wings are typical of WWII war planes and many newer passenger planes and commercial jets.

Mid wing planes are usually considered the most difficult to fly. The wings are usually located right in the vertical middle of the plane, near the bulk mass of the plane. Very little leverage is needed to turn and rotate the plane's weight.

Mid wings are often straight without any dihedral providing an almost symmetrical aerodynamic structure. This allows the plane to be relatively balanced whether rightside-up, upside-down, or any other position. This is great for military jets, sport planes and aerobatic planes, but less advantageous for the learning pilot. Because of this symmetry, the plane doesn't really have any natural or stable flying position, like the high wing planes, and will not automatically return back to a stable gliding position.

The number of channels a plane requires is determined by the number of electronic servos that have been installed. On smaller models, usually one servo is required per control surface.

* Ailerons - controls roll.
* Elevator - controls pitch (up and down).
* Throttle or, if electric, motor speed.
* Rudder - controls yaw (left and right).

For more complex models and larger scale planes, multiple servos may be used on control surfaces. In such cases, more channels as required to perform the various functions (operatin opening cargo doors, dropping bombs, operating remote cameras, lights, etc.

The right and left ailerons move in opposite directions. However, aileron control will often use two channels to enable mixing of other functions on the transmitter. For example when they both move downward they can be used as flaps (flaperons), or when they both move upward, as spoilers (spoilerons). Some aircraft, such as the Concorde do not have an elevator. When that function is mixed with ailerons the surfaces are known as elevons. Each of these mixes are common on radio control planes.

Three channel RC planes are common. Either ailerons or rudder is eliminated. If the rudder is eliminated, turning is accomplished by rolling the plane left or right and applying the correct amount of up-elevator. If the ailerons are eliminated, the wing needs to have a significant amount of dihedral (V-bend in the wing). The rudder will turn the plane so that one wing will turn into the wind, causing it to lift and roll the aircraft. Many trainers and electric park fliers use this technique.

Most planes need a powerplant to drive them, the exception being gliders.

For larger and heavier models, the most popular powerplant is the glow-engine, a form of internal combustion engine. They function very similarly to diesel engines, as they do not use spark plugs and rely on the heat of compression for combustion. Glow-engines appear similar to small gasoline motorcycle-engines, but glow-engines are considerably simpler in operation. The simplest (and cheapest) glow-engines use a two-stroke cycle engine, glow plug to burn fuel, and an external ignition system (a dry cell or other low voltage source). This ignitor battery is only used for starting. After the engine is running, the platinum metal filament in the glow plug continues to glow, from a catalytic reaction with the methanol vapor present in all glow-engine fuels, and the battery can be removed. The fuel is a mixture of slow burning methanol, nitromethane, and oil lubricant (castor oil or synthetic oil). The reciprocating action of the cylinders applies torque to a crankshaft, to which the propeller is connected. Vendors of model engines rate size in terms of engine displacement. Common sizes range from as small as 0.01 cubic inch (in³) to over 1.0 in³ (0.16 cc - 16 cc). As Richard Feynman mentioned in his famous There's Plenty of Room at the Bottom lecture, the speed an engine can rotate without breaking tends to go as the inverse of the linear dimension (inverse 1/3 power of the displacement). However, the intake air flow improves less quickly than that with small scale, due to decreasing Reynolds number and, eventually, to viscous flow.

Not all simple internal combustion model aircraft engines use glow plugs. There are also true diesels, that used to be popular in Europe. These also are carbureted, not fuel injected. They have an adjustable compression ratio and burn a more easily ignited mixture of ether and kerosene (with lubricating oil). These are preferred for endurance competition, because of the higher energy content of the fuel.

Internal combustion (IC) engines are also made in upscale (and up-price) configurations. Increasingly popular variations include four-strokes, which appeared in modern form as early as 1976, and which usually use much less fuel (important for the higher cost of glow-fuel) due to the more efficient fuel-air handling of a four-stroke, and are much more easily quieted down with mufflers. Small, gas-powered engines, such as those used for weed wackers and chainsaws are becoming increasingly popular for giant scale models, which are typically considered to be 25% the size of the real plane, or larger. All IC engines generate substantial noise (and engine exhaust) and require routine maintenance. In the scale RC community, glow-engines have been the mainstay, but electric power for small and beginner planes, and gasoline power for larger planes are two rapidly expanding areas.

In electric-powered models, the powerplant is a battery-powered electric motor. Throttle control is achieved through an electronic speed controller (ESC), which regulates the motor's output. Electric-flight was tested on model aircraft in the 1970s, but high-cost and inefficiency prevented widespread adoption within the industry until the early 1990s, where falling costs of motors, control systems and, crucially, more practical battery technologies came on the market. Electric-power has made substantial inroads into the park flyer and 3D-flyer markets. Both markets are characterized by small and lightweight models, where electric-power offers several key advantages over gas engines: greater efficiency, higher reliability, less maintenance, much less pollution (both air pollution and the layer of unburnt fuel that collects on the fuselage of IC powered aircraft after flying), and more quiet flight. The 3D-flyer especially benefits from the near-instantaneous response of an electric-motor and the high power-to-weight ratios possible from Lithium-polymer batteries and brushless motors.

As the size of a model aircraft increases, the cost of electric-flight increases much more rapidly than traditional glow-engine flight. As of 2005, an electric-flight conversion for mid-large scale-models (above 0.60in³ glow-engine) is prohibitively expensive (>$400 USD), though prices are dropping quite rapidly. Most such models remain powered by the venerable glow-engine, as their pilots prefer the sound and smell of a genuine 4-stroke IC-engine. Solar powered flight has been demonstrated, but is not yet practical for RC hobbyists.

A recent development is the use of small jet turbine and ducted fan engines in hobbyist models, both surface and air. Model-scale turbines resemble simplified versions of turbojet engines found on commercial aircraft, but are in fact new designs (not based upon scaled-down pre-existing commercial jet engines.) The first hobbyist-developed turbine was developed and flown in the 1980s, but only recently has commercial production made turbines readily-available for purchase.

A ducted fan (usually electric) is an assembly of the spinning fan (a propeller with more blades), held inside a shaped-duct. Compared to an open-air propellor, a ducted-fan generates more thrust per crossectional-area. The shaped-duct often limits installation to recessed areas of the fuselage or wings. Ducted fans are popular with scale planes of jet-aircraft, where they mimic the appearance and feel of jet engines, as well as increasing the model's maximum airspeed. They are also found on non-scale and sport models, and even lightweight 3D-flyers. Like propellers, fan-units are modular components, and most fan-powered aircraft can accommodate a limited selection of different fan-units. Actual turbine engines are gas powered versions of the same general idea.

Turbines require specialized design and precision-manufacturing techniques (some designs for model aircraft have been built from recycled turbocharger units from car engines), and consume a voracious mix of A1 jet fuel and synthetic motorcycle-engine oil. These qualities, and the turbine's high-thrust output, makes owning and operating a turbine-powered aircraft prohibitively expensive for most hobbyists. Turbine-powered and ducted fan planes attract large crowds at organized events; their authentic sound and high-speed make for excellent crowd pleasers.

Pulse jet engines, operating on the same principle as the WW II V-1 flying bomb have also been used. The extremely-noisy pulsejet offers more thrust in a smaller package than a traditional glow-engine, but is not widely used. A popular model was the "Dynajet".

Rocket engines are sometimes used to boost gliders and sailplanes. In the 1950s, a type of model rocket motor called the Jetex engine was quite popular. Today, flyers mount readily-available model rocket engines to provide a single, short (< 10 second) burst of power. However, government regulations and restrictions have rendered rocket-propulsion unpopular even for gliders.

Frequency determines the line of communication between a receiver and transmitter. The transmitter and receiver must both be on the same frequency so the plane can be controlled.

Many countries reserve specific frequencies for radio control use. Due to the longer range and potentially worse consequences of radio interference, model aircraft have exclusive use of their own frequency allocation in some countries.

USA and Canada reserved frequencies

* 72 MHz: aircraft only (France also uses US/Canada channels 21 through 35).
* 75 MHz: surface vehicles.
* 27 MHz: general use, toys.

European reserved frequencies

* 35 MHz: aircraft only.
* 40 MHz: surface vehicles.
* 27 MHz: general use, toys, citizens band radio.

Australian reserved frequencies

* 36 MHz: aircraft and water-craft (odd channels for aircraft only)
* 29 MHz: general use
* 27 MHz: light electric aircraft, general use

Amateur Radio License reserved frequencies

* 50 and 53 MHz in the USA and Canada
* 433-434 MHz in Germany

Remarkably, there are specific bands in 35 MHz called A and B bands. Some European countries allows only use in A band, whereas others allow use in A and B band.

RC aircraft in the USA utilize a 72 MHz frequency band for communication. The transmitter radio broadcasts on AM, FM using PPM or PCM. Each aircraft needs a way to determine which transmitter to receive communications from, so a flight channel, or sub-channel (range of frequency), is necessary.

A crystal is put into the transmitter to allow it to communicate at a specific sub-channel to match the receiver in the aircraft. This is important so that two transmitters are not trying to control the same craft, resulting in an uncontrolled and potentially dangerous crash. For example, if a person is flying an aircraft on channel 35, and someone else turns their radio on the same channel, the aircraft's control will be compromised and the result is almost always a crash. For this reason, when flying at RC airfields, there is normally a board where hobbyists can post their sub-channel flag, so everyone knows what channel they are using, avoiding such incidents.

A modern computer radio transmitter and receiver can be equipped with synthesizer technology, using a Phase Locked Loop (PLL), with the advantage of giving the pilot the opportunity to select any of the available channels with no need of changing a crystal. This is very popular in flying camps where a lot of pilots have to share a limited number of channels.

Some new controllers use spectrum technology. These controllers are manafactured by Spektrum. When turned on, they will automatically lock on to two channels. Interference is impossible due to the fact that they operate above normal frequencies. The receivers and transmitters are also embedded with a unique code as an extra precaution.

Model aircraft are also used in the military, with its primary task to gather intelligence of areas. Most of these devices use ball-bearing engines, similar to those found on R/C boats.

Besides as a reconnaissance vehicle, there are also concerns that it could be used for bomb attacks. Just as Bruce Simpson's home-made cruise missile, it could be rigged with an explosive or biological bomb.Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts.
Virtual Magic is a human knowledge database blog. Text Based On Information From Wikipedia, Under The GNU Free Documentation License. Copyright (c) 2007 Virtual Magic. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".

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