Types
Free flight models may be broadly divided into four categories:
- Gliders (towline and hand-launched)
- Rubber-powered (pure duration, and scale with duration)
- Power (CO2, Methanol-fueled glow engine, or electric)
- Indoor (pure duration, and scale with duration)
When flown competitively, the usual aim is maximum flight duration. In the case of models flown outdoors, the modeler attempts to launch the model into rising column of air, a thermal. These outdoor free flight models tend to be designed for two very different flying modes: climbing rapidly under power or tow, and gliding slowly while circling with minimum fall rate. Much of the challenge in designing and flying these models is to maintain aerodynamic stability in both modes and to make a smooth transition between them. Modern models use mechanical or electronical timers to move control surfaces at preset times. Detecting the thermal into which to launch is vital and can involve several methods, ranging from radio telemetered temperature and windspeed measurements plotted on a chart recorder to Mylar streamers or soap bubbles to visualize the rising air.
Because competitions normally involve up to seven rounds during the day, each flown to a maximum flight time hard to achieve without thermal assistance; an automatic on-board timeswitch upsets the trim of the aircraft when the "max" is achieved, to bring the aircraft down safely and quickly. Locating and recovering the aircraft for further flights is an important part of free-flight. Many aircraft carry radio location beacons, and flyers will use GPS, binoculars, a compass and a directionally sensitive radio tracking receiver to assist them. A day's flying and retrieval may well involve 20 miles (32 km) or so on foot or on bike, depending on wind strength.
Models flown indoors do not depend on rising air currents, but they must be designed for maximum flight efficiency, because of the limited energy stored in the rubber or electric power source.
Within each category, there are different classes. Typically, there is an Fédération Aéronautique Internationale (FAI) world-championship class, a so-called mini class, an open class, and possibly any number of national or unofficial classes, for which regional or national competitions may be held. Within the competition classification codes specified by the FAI, free flight aeromodeling gets the generic code of F1, where the "F" stands for flying model aircraft in general, with the "1" stading specifically for free flight models.
Read more about this topic: Free Flight (model Aircraft)
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