| Radio-controlled glider | |
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| A traditionally built '100S' class thermal soaring glider |
A radio-controlled glider is a type of radio-controlled aircraft that normally does not have any form of propulsion. They are able to sustain continuous flight by exploiting the lift produced by slopes and thermals, controlled remotely from the ground with a transmitter. They can be constructed from a variety of materials, including wood, plastic, polymer foams, and composites, and can vary in wing loading from very light to relatively heavy, depending on their intended use.
International radio-controlled glider competitions are regulated by the Fédération Aéronautique Internationale (FAI) although many countries have their own national classes.
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Hand launching is the simplest way to get a model into the air. Depending on craft design & the conditions at launch - the pilot or an assistant need only to gently 'throw' it into the wind, at an angle deemed best suited, usually between horizontal & 45 degrees of zenith. In this manner a successful launch is possible with very little effort. This method is usually utilised when slope soaring, where with a little experience, it is possible to simply hold the craft above your head at the correct angle & let go.
In this method another person runs along the ground, pulling a long (50 - 100m) line with the glider attached to the end, while the pilot steers it. It can be performed on any flat piece of terrain, as the glider is given sufficient altitude during the launch. A variation of this method uses a pulley staked to the ground with the tower moving toward the pilot.
This launch is a variant of the towline launch performed alone. The running person is replaced by a combined length of elastic cord or rubber tubing and line which is attached to the ground, often using a 'corkscrew' dog stake.[1]
A second, powered radio-controlled powered aircraft lifts the model glider into the air, attached to a special cradle which is, in turn, mounted to either the top or the bottom of the carrier aircraft. Although this method is spectacular, it requires an experienced pilot to steer the carrier aircraft as the addition of the glider can significantly affect the handling of the carrier aircraft. Special care must be also taken by the pilots of both models to avoid a collision after the release of the glider.
This method of launching can be performed only on a special type of glider - a Discus Launch Glider. To launch the model into the air, the pilot holds the model by the tip of a wing, spins 360°, rotating the model around his/her body and then releases hold of the model allowing it to launch at high speed . Although DLGs are a fairly new type of gliders, they are gaining popularity due to their ease of launching and efficient flight characteristics. DLG models are used in the F3K contest class, as defined by FAI.
As full-size aerotowing using a radio-controlled tug, often used for launching larger scale gliders.[2]
As full-size winch launching but using a small electric motor and a reverse pulley staked to the ground. The launch speed is controlled by the pilot using a foot pedal.[3]
Slope soaring uses the lift produced by wind blowing up the face of a steep slope on hills, mountains, and cliffs.[4] Dynamic soaring, utilizing the leeward or "backside" of a hill, has recently become very popular.
Combat is usually flown with expanded polypropylene (EPP) foam models due to their impact resistance. Each pilot tries to knock the other's aircraft physically out of the air. A "kill" is scored only when the opponents aircraft hits the ground. If a hit occurs and each aircraft recovers and remains airborne, the hits generally do not count. Often this activity includes extreme maneuvers and aerobatics.
This particular class of slope glider is extremely popular, as novices can learn to fly with a model that is practically indestructible. There is also a wide appeal in owning an inexpensive glider that is also a stand-off scale model, particularly of favorite World War II fighters, e.g. the Spitfire/Seafire, P-51 Mustang and P-47 Thunderbolt.
Ridge racing (or pylon racing where markers are present) is essentially using the slope lift to race along the "lift zone" -- generally parallel to the slope. This can be MoM (man-on-man) racing, in which 2 to 4 gliders compete against each other on the same course. Scoring is similar to match racing in the sport of sailing - the first pilot to complete the course receives one point, the second two points and so on. At the end of the competition, the pilot with the fewest points wins. Another form of slope r/c glider racing is called F3F. F3F is one of many competition categories for model and full scale aircraft that are defined by the Fédération Aéronautique Internationale (FAI). In F3F racing, the pilot is timed on the course for 10 legs of 100 meters for a total distance of 1 kilometer. All pilots fly a timed run for each round. The fastest pilot receives 1000 points for the round and all others are given a percentage which is determined by the ratio of their time to the fast time for the round. At the end of the competition, the pilot with the most points wins.[5]
PSS, or Power Scale Soaring, is all about building and flying scale model gliders of full-sized jet-, rocket- or piston-powered aircraft. World War II prop planes such as the P-51, Supermarine Spitfire and Me 109 are common subjects for PSS planes, however PSS aircraft produced to date have ranged from the early biplanes through to modern jet fighters and even commercial airliners.
The challenge with Power Scale Soaring is to build a model as close to scale as possible whilst at the same time ensuring the model has good flying characteristics.
Model EPP jet fighter slope soarers have become extremely popular, usually either 1950s and some 1960s designs e.g. the MiG-15, the P-80 Shooting Star, and the F-86 Sabre, and the Northrop F-5 and F-20. More ambitious modellers are experimenting with more recent jet fighters such as the F-16, F-15, MiG-29 and Su-27.
Equally popular are models of military trainers, such as the Pilatus PC-9, BAe Hawk, and Aermacchi MB 326 and MB 339.
More information about Power Scale Soaring can be found under Power Scale Soaring Association and the website of the Power Scale Soaring Association (PSSA)[1]
Dynamic soaring is a relatively new style of flying model gliders whereby the windshear just downwind of certain slopes can be used to create high speeds. It involves gaining altitude, then soaring into a patch of dead air, then back to the lift to gain speed.
Thermal soaring uses columns of warm, rising air called thermals to provide lift for a glider. Thermal soaring gliders are normally launched with a bungee cord catapult, a winch or towed by a powered plane. A discus launch glider (DLG) is simply catapulted into the air with a spinning motion much like a discus throw.
Discus launching is often combined with slope soaring. Thermals from elsewhere can drift in over the hill to combine with the hill lift or they can be formed by the hill itself, if the slope is angled to the sun causing the slope to heat up faster than in the surrounding areas. The resulting warm air will then flow upwards pulling in air from the valley below, causing a wind up the slope. The lift is thus a combination of ridge lift and thermal. This has produced a new term, "slermal", to describe the mixture of both slope lift and thermal activity coming up the hill face.
Expanded polypropylene foam ( EPP) foam flying wings have become very popular recently, primarily due to their crash damage resistance and low cost. They are often used for slope combat, where pilots try to knock other pilots' gliders out of the sky with their own. A "kill" is only scored when the opponent's plane actually hits the ground. A popular airfoil used on some flying wing type gliders is the KF airfoil or one of the variants of the family of the Kline Fogleman airfoil. This airfoil has been proven to show an increase in performance by providing greater stability on the wing at lower speeds.
Scale gliders are models of full-size gliders. Scale gliders are generally larger models (2 m wingspan or greater) and made from composite materials. Scale Gliders are sometimes modified slightly to obtain the best flying characteristics, such as less drag and more aerobatic potential. This is achieved by changing the size of the control surfaces or the wing airfoil. Some scale gliders are very close in appearance to their full scale counterparts, and this makes them a beautiful sight at any flying field. A model often "scaled" because of its clean looks and great aerobatic potential is the MDM-1 Fox. The ASW series (mostly ASW-26 and ASW-28) are also popular scale gliders.
Powered gliders use electric motors, internal combustion engines or even jet turbines to provide propulsion for a glider to get in the air. They are normally used to get thermal soarers in the air.[6] Some electric gliders have propellers which fold inwards when the power source is cut of during flight. This provides the glider with lower air resistance and reduces overall drag which may be present if the propeller was to remain in its open or natural state.
Note[7]
International radio-controlled glider competitions are regulated by the Fédération Aéronautique Internationale (FAI). The classes are:
British national radio-controlled glider classes are:
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