Radio-controlled aircraft
From Wikipedia, the free encyclopedia
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.
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[edit] Types
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".
[edit] Park flyers and trainers
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 engine powered. A glow engine is an internal combustion engine that burns a methanol/nitromethane/oil mixture.
[edit] Scale and sport planes
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.
Other sport aircraft are designated for scale-like flying referred to as "Scale." Scale is a very demanding but very rewarding aspect of the hobby. (More to come later)
[edit] Sailplanes and gliders
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. Dynamic soaring is another popular way of providing propulsion to gliders.
[edit] Jets
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.
[edit] Pylon racers
Racers are small propeller aircraft that race around a 2, 3, or 4 pylon track. They tend to be hard to see and can often go over 150 MPH, though some people do pylon races with much slower aircraft.
[edit] Helicopters
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.
[edit] 3D flight
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.
[edit] Types of kits and construction
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. "Crash proof" EPP (Expanded Polypropylene) foam planes are actually even bendable and usually sustain very little or no damage in the event of an accident, even after a nose dive.
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).
[edit] Ready To Fly
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.
[edit] Almost Ready to Fly
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.
[edit] Balsa kit
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.
[edit] From plans or scratch
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.
[edit] Plane characteristics
[edit] Wing location
[edit] High wing
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 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.
[edit] Low wing
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 World War II war planes and many newer passenger planes and commercial jets.
[edit] Mid wing
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 to a stable gliding position.
[edit] Number of channels
The number of channels a plane requires is determined by the number of mechanical servos that have been installed. On smaller models, usually one servo per control surface is sufficient.
- 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 may be required to perform various functions such as 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.
With a three channel RC plane, either the ailerons or rudder control surface 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.
[edit] Powerplants
Most planes need a powerplant to drive them, the exception being gliders. The most popular types for radio-controlled aircraft are internal combustion engines, electric motors, jet, and rocket engines. More info on all of these can be found at Model aircraft.
[edit] Frequencies and sub-channels
[edit] Frequency
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.
[edit] Reserved frequencies
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.
[edit] Sub-channels
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 spread spectrum technology. The most popular of these radio systems is made by a company called Spektrum, though other companies are working on their own versions. Spread spectrum allows multiple applications (pilots) to transmit using the same radio frequencies with little fear of conflicts.
[edit] Military usage
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.
[edit] See also
- Radio-controlled model
- Radio-controlled helicopter
- Model aircraft
- Academy of Model Aeronautics direct link to website
- British Model Flying Association
- Scale model
- Hotliner
- Fly RC
- International Miniature Aerobatic Club
[edit] External links
- RCUniverse - 280,000+ members. Truly the largest and most active RC community. Forums, classifieds, magazine, product guide, events, more.
- RCU Videos Radio control videos of airplanes, cars, boats, helis
- WattFlyer.com - Active electric rc aircraft forums
- RCGroups.com - the most active R/C community on the internet
- Flying Sites - UK's biggest resource of r/c model aviation information, help and news, including a very popular forum.
- Savage-Central R/C Forums, News & more
- Smooth Air Electric Flight Website
- Listing of many international RC frequencies
- United States RC frequencies
- Skyrunner RC Jet Website
- RC Airplane World - a comprehensive Getting Started in Radio Control guide
