An improvement of the MacCready speed-to-fly theory used in sailplanes cross-country flights is outlined. Two different parameters characterizing the thermal are introduced (the vertical speed of the air inside the thermal and the thermal radius) and a universal dimensionless model is proposed, which can be applied to any sailplane. The maximum average cross-country speed, the optimum airspeeds in descent and climb, the rate of climb in the helical trajectory and other flight variables are calculated versus two abbreviated parameters condensing thermal and sailplane data.
ReichmannH.Vuelo sin Motor. Técnicas Avanzadas, 1988 (Paraninfo, Madrid).
2.
MacCreadyP.Optimum airspeed selector. In Soaring, 1954 (Santa Monica, California).
3.
MetzgerD. E.HedrickJ. K.Optimal flight paths for soaring flights. J. Aircraft, November 1975, 12 (11), 867–871.
4.
StojkovicB.Generalized speed-to-fly theory. Tech. Soaring, July 1993, XVII (3), 77–83.
5.
SpeightG.Automatic adjustment of the MacCready ring. Tech. Soaring, April 1989, XIII (2), 57–58.
6.
FinkeK.Comparison of classical speed to fly theory using second, third, fourth and fifth degree polynomial speed polars. Tech. Soaring, July 1992, XVI (3), 78–85.
7.
MatharR.Stochastic models of thermal convection: An extended MacCready theory and a simulation tool. Tech. Soaring, October 1996, XX (4), 113–117.
8.
MieleA.Flight Mechanics, Vol. 1: Theory of Flight Paths, 1962 (Addison-Wesley, Reading, Massachusetts).
9.
Martínez-GarcíaJ. J.Gómez-TiernoM. A.Curso de Mecánica del Vuelo, 1993 (Publicaciones de la ETSIA, Madrid).
10.
HaleF. J.Introduction to Aircraft Performance, Selection and Design, 1984 (John Wiley, New York).
11.
Jane's All the World's Aircraft 1987–1988, 1987 (Jane's Publishing Company Limited, London).
12.
Manual de Vuelo y Calculadores de Planeo del Planeador Schleicher ASK-21, 1997 (Dirección General de Aviación Civil, Escuela de Planeadores, Ocaña, Toledo).
