GLIDING GLOSSARY
by Waid Reynolds
Someone on RC Soaring Exchange who was new to RC soaring requested definitions of the terms being bandied about. I borrowed some definitions from replies on RCSE, and added a few of my own. Hopefully, this information might be of use to some of us who are just getting up to speed. Let me know if you think of other terms or acronyms that should be added to the list.
| Term | Definition |
| TD | Thermal duration, the most common type of RC soaring contest. Each flight in a contest involves keeping the glider aloft for a time predetermined by the contest director. A precision (time and/or location) landing may also be required. |
| High Start | A commonly used launching device for thermal gliders. A length of surgical tubing (tubing size is dependent on weight of glider to be launched) is staked to the ground at one end. A string is tied to the other end of the tubing. A parachute and a metal ring are tied to the far end of the string. The metal ring is then pulled back until the tubing is stretched to 3 or 4 times its normal length. The ring is slid onto the hook on the bottom of a glider. When the glider is released the high start pulls it into the air until all the tension has been released from the tubing. At that point the ring slides off the hook and the glider is free. |
| XC | Cross country RC soaring. The pilot and helpers ride in a pickup or open car while soaring their glider. The object is either to go fastest around a closed course, or to go for all out distance. FAI (see below) has establshed world records for this category. |
| FAI | Federation Aeronautique Internationale, the international aviation (both model and full size) organization that establishes world championship aviation competition rules, and promulgates world records. |
| F3B | International (FAI) soaring class. Contests involve speed, distance and duration tasks. Requires expensive equipment and considerable teamwork. Not common in the U.S. |
| F3J | International (FAI) thermal duration soaring class launched by hand tow. Tasks are similar to TD contests. But, flight scores are normalized within each group of pilots who launch their gliders simultaneously. There is less emphasis on spot landings. |
| Slope Soaring, or Sloping | Flying a glider along the top of a cliff or hill where the wind blowing against the face of the embankment is forced to go up, creating an updraft. Gliders can be kept aloft as long as the wind is sufficiently strong. |
| PSS | Power slope scale, slope soaring models that look similar to full size powered aircraft. These tend to be fairly fast, relatively heavy, and highly maneuverable for performing aerobatics. They are usually flown in moderate to high winds of 15 to 30 knots. |
| Crow | Both ailerons raise as flaps go down to increase descent rate during landing approach. |
| Reflex | The trailing edge of the wing is raised slightly. In flying wings this is to reduce the pitching moment so that a horizontal tail is not needed. In conventional gliders reflexing the flaps and ailerons reduces aerodynamic drag for high speed cruising between thermals. |
| Unlimited | Refers to a popular TD competition glider class in which there is no wingspan limitation. |
| Standard Class | Refers to a less popular TD competition glider class in which wingspan is limited to 100 inches. |
| 2M, 2 Meter | Refers to a popular TD competition glider class in which the wingspan of the glider is limited to 2 meters (about 79 inches) |
| HLG | Hand launched RC glider. |
| Aspect Ratio, AR | The ratio of the wing span to the average wing chord (width). Usually computed by dividing the square of the wing span by the area of the wing. In general, wings with higher aspect ratios exhibit less drag than those with lower aspect ratios. |
| Wing Loading, WL | The flying weight of the glider in ounces divided by the lifting area of the glider's wing in square feet. Expressed as "ounces per square foot", "oz/sf". Wing loading determines how fast gliders fly relative to one another. A glider of higher wing loading must fly faster. |
| Gas Bag, Floater | Light wing loading glider designed to fly slowly and stay up in weak lift. Usually will not penetrate into wind very well. Wing loading would be less than 8 oz/sf and probably in the 4 to 6 oz/sf range. |
| Stall | When a wing flies at very high angles of attack relative to the airflow (usually >10 degrees) the airflow over the top of the wing may separate from the wing surface, causing severe turbulence, high drag, and loss of most of the wing's lift. |
| Tip Stall | The stall occurs at a wing tip first. This can result in loss of control and a sudden drop of one wing, which results in a spin. It is best to design wings so that the root stalls first and the tips last so that the ailerons remain effective until the wing is almost fully stalled. |
| Dork Landing, Lawn Dart Landing | A spot landing in which the pilot dives the glider nearly vertically into the ground in an attempt to hit the spot. Not very aesthetic, and tends to break gliders. To be avoided unless you thrive on ridicule. |
| Rx, Rcvr | Radio receiver |
| Tx, Xmtr | Radio transmitter |
| IC | Integrated circuit |
| Pot | Potentiometer |
| Cap | Capacitor |
| FG | Fiberglass cloth. Also refers to construction where fiberglass cloth is embedded in epoxy or polyester plastic resin. |
| Composite Construction | In gliders, this construction utilizing FG, CF, Kevlar, and other types of man made fabrics embedded in plastic resin |
| FC | Foam core. Hot wire cut foam styrofoam core generally used in wings and tails. |
| CF | Carbon fiber cloth or tow. Has extremely high tensile strength to weight ratio. |
| Tow | A bundle of parallel carbon fibers often used as reinforcement on the top and bottom of wing spars to improve the bending strength and rigidity |
| LE | Leading edge. Middle name of a lot of French dudes. |
| TE | Trailing edge. |
| CG | Center of gravity, the fore and aft location where the model balances. |
| FW | Flying wing. |
| Fuse | Fuselage, the body of an aircraft. |
| Stab | Horizontal stabilizer. |
| Wingeron | The wings, which are mounted on a wing rod that serves as an axle, rotate in opposite directions to provide roll control in lieu of using ailerons. |
| Pitcheron | The wings rotate in the same direction to provide pitch control. The stab is not moveable. This term normally assumes wingeron capability, as well. |
| CD | Contest director. |
| WC | World champion in the United States. Water closet in the United Kingdom. |
| Hemo | Hemostat: a locking needle-nose clamp used by modelers and physicians |