Glider Kits* Gliders built from kits are eligible for FAA certification if supported by a statement certifying that the glider was constructed in accordance with FAA-approved drawings and the manufacturer's manual of directions for building the glider; and that the parts and materials used, if other than those furnished with the kit, meet the manufacturer's recommendations. Also, the following inspections, by FAA representative, and tests should be made. • Inspection for workmanship, materials and conformity prior • A final inspection of the completed glider. Arrangement of Handbook The material in Basic Glider Criteria Handbook has been arranged so that the particular glider airworthiness recommendation is followed by the suggested methods for showing compliance. In cases where methods for showing compliance are not needed, the airworthiness recommendation will have no accompanying guidance material. Procedures and practices that assure safety equal to those listed in this handbook will also be acceptable. Any provisions which are shown to be inapplicable in a particular case will be modified upon request and evaluation by the Federal Aviation Agency. For further FAA guidance material on glider certificates, compliance procedures and related subjects, the following references are listed: *Prior to beginning construction, it should be determined that the manufacturer of the kit has obtained a type certificate for the prototype glider built from such a kit. Definitions TECHNICAL TERMS AND RELATED SYMBOLS (For definitions of nontechnical terms, refer to Par. 1.1 of CAR Part 1) Aerodynamic coefficients, CL, Cм, Сp, et cetera. The coefficients hereinafter specified are those of the "absolute" (nondimensional) system adopted as standard in the United States. The subscripts N and C used herein refer respectively to directions normal to and parallel with the basic chord of the airfoil section. Other subscripts have the usual significance. When applied to an entire wing or surface, the coefficients represent average values and shall be properly correlated with local conditions (wing load distribution) as required in Chapter 1, p. 13. (See figs. i-II, i-III and i-IV.) Air density, P.-The mass density of the air through which the glider is moving, in terms of the weight of a unit volume of air divided by the acceleration due to gravity. The symbol denotes the mass density of air at sea level under standard atmospheric conditions and has a value of 0.002377 slugs per cubic foot. (See definition of standard atmosphere.) Balancing loads.-Loads by which the glider is placed in a state of equilibrium under the action of external forces resulting from specified loading conditions. The state of equilibrium thus obtained may be either real or fictitious. Balancing loads may represent air loads, inertia loads, or both. Calibrated airspeed, CAS.-Speed equal to the indicated airspeed reading corrected for position and instrument error. Design aircraft tow speed, Va.-The maximum indicated airspeed at which the glider is to be towed by aircraft. Design auto-winch tow speed, Va.-The maximum indicated airspeed at which the glider is assumed to be towed by automobile or winch. Design flap speed, V,.-The indicated airspeed at which maximum operation of high-lift devices is chosen. Design gliding speed, V,.-The maximum indicated airspeed to be used in the determination of gust loads. Design gust velocity, U.—A specific gust velocity assumed to act normal to the flight path. Design stalling speed, Vs.-The computed indicated airspeed in unaccelerated flight based on the maximum lift coefficient of the wing and the gross weight. When high-lift devices are in operation, the corresponding stalling speed will be denoted by V sƒ• Figures i-ll, i–III and i—IV. Illustration of airfoil force coefficients. Design wing area, S.-The area enclosed by the projection of the wing outline (including ailerons and flaps, but ignoring fairings and fillets), on a surface containing the wing chords. The outline is assumed to extend through the fuselage to the plane of symmetry. (See fig. i-I.) Design wing loading, s = W/S.-The gross weight divided by the design wing area. (Area computed with wing flaps in retracted position, if so equipped.) Design dive speed, VD.-The maximum indicated airspeed to be used in the structural loading conditions and for which the glider is demonstrated to be free from flutter or any other undesirable flight characteristics. For utility category gliders V, shall not exceed V,. For high performance gliders, V, may exceed V,, but shall not be greater than 1.2 V,. Ꭰ Dynamic pressure, q.-The kinetic energy of a unit volume of air. = 1⁄2 PV,2 (in terms of true airspeed in feet per second). = 1⁄2 P.V2 (in terms of equivalent airspeed in feet per second). = = V2/391 pounds per square foot, when Vis miles per hour IAS. Gross weight, W.-The design maximum weight of the glider and its contents, used for purposes of showing compliance with the specified recommendations. Indicated airspeed, IAS.-Speed equal to the pitot static airspeed indicator reading as installed without correction for system errors but including sea level standard adiabatic compressible flow correction, and instrument error. Load factor or acceleration factor, n.—The ratio of a force acting on a mass to the weight of the mass. When the force in question represents the net external load acting on the glider in a given direction, n represents the load factor or acceleration factor in that direction as a multiple of the gravitational constant g. Limit load. The maximum load anticipated in service. Limit load test.-A static test in which the limit loads are properly applied. Never exceed speed, VNE.-The maximum indicated airspeed for which the glider is certificated for operation. Primary structure. Those portions of the glider structure, the failure of which would seriously endanger the airworthiness of the glider. Proof load. The prescribed externally-applied load, multiplied by the proof factor (normally 1.0). Standard atmosphere (standard air). Standard atmosphere refers to that variation of air conditions with altitude which has been adopted as standard in the United States. (See NACA Technical Report No. 218.) Mean aerodynamic chord.-The chord of an imaginary airfoil which would have force vectors throughout the flight range identical with those of the actual wing or wings. Terminal velocity. The maximum speed obtainable in diving flight. True airspeed, TAS.-True airspeed of the glider relative to undisturbed air. 657822 O-62-2 Ultimate factor of safety, j.—A design factor used to provide for the possibility of loads greater than those anticipated in normal conditions of operation and for design uncertainties. NOTE: Design wing area is outlined Figure i-l. Typical design wing areas. Ultimate load. The maximum load which the structure is required to support. It is obtained by multiplying the limit load by the ultimate factor of safety. Ultimate load test.—A static test in which the ultimate loads are properly applied. Loads should be supported for at least 3 seconds. |