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Journal of Theoretical
and Applied Mechanics
5, 1, pp. 57-101, Warsaw 1967
and Applied Mechanics
5, 1, pp. 57-101, Warsaw 1967
Uproszczona analiza stateczności podłużnej szybowca w locie holowanym
Loty holowane szybowców są obecnie szeroko stosowane. Dotychczas jednak zagadnienie stateczności szybowców w locie holowanym nie zostało w pełni rozwiązane. Istnieje zaledwie kilka prac związanych z tym zagadnieniem. W niniejszej pracy rozpatrzono przypadek holu szybowca sztywnego nieodkształcalnego) przez samolot (ciężki) znajdujący się w poziomym prostoliniowym locie ustalonym. Opierając się na pracach [9] i [10] określono konfiguracje rozciągliwej liny holowniczej z uwzględnieniem oporów tarcia. Rozpatrzono równowagę i stateczność statyczną podłużną szybowca w locie holowanym, określono zakresy kątów holu i współczynników siły nośnej możliwych do uzyskania w czasie holu.
SIMPLIFIED LONGITUDINAL STABILITY OF A TOWED SAILPLANE
The paper deals with the case of a rigid sailplane towed by ail aircraft in a horizontal, steady flight along a straight line. The tow rope configuration was defined according to the paper by S. Neumark, the aerodynamic forces being taken into account. The equilibrium of the towed sailplane was considered. The tow angle intervals and the respective lift coefficients were calculated. The longitudinal stability of a sailplane was analysed by means of the small perturbation method developed by Bryant, Brown and Sweeting. This method leads to a sixth order characteristic equation and allows for the application of the Ruth-Hurwitz stability criterion. The roots of characteristic equation were calculated by means of the Bairstow method. Numerical analysis was accomplished for a specified high performance sailplane prototype. The influence on the stability of the following parameters was investigated: the relative sailplane-towing aircraft attitude, the flight velocity, the attachment lock position in relation to the sailplane gravity center, the length and elasticity of the tow rope. As may be concluded from the obtained results the towing does not change the high frequency oscillation but modifies the fugoidal ones. With respect to the sailplane stability it is advantageous — to fly the sailplane below the level of the towing aircraft for the fugoidal oscillation damping, -— the attachment lock should be built in to the sailplane structure before the gravity center (preferably above its level).
SIMPLIFIED LONGITUDINAL STABILITY OF A TOWED SAILPLANE
The paper deals with the case of a rigid sailplane towed by ail aircraft in a horizontal, steady flight along a straight line. The tow rope configuration was defined according to the paper by S. Neumark, the aerodynamic forces being taken into account. The equilibrium of the towed sailplane was considered. The tow angle intervals and the respective lift coefficients were calculated. The longitudinal stability of a sailplane was analysed by means of the small perturbation method developed by Bryant, Brown and Sweeting. This method leads to a sixth order characteristic equation and allows for the application of the Ruth-Hurwitz stability criterion. The roots of characteristic equation were calculated by means of the Bairstow method. Numerical analysis was accomplished for a specified high performance sailplane prototype. The influence on the stability of the following parameters was investigated: the relative sailplane-towing aircraft attitude, the flight velocity, the attachment lock position in relation to the sailplane gravity center, the length and elasticity of the tow rope. As may be concluded from the obtained results the towing does not change the high frequency oscillation but modifies the fugoidal ones. With respect to the sailplane stability it is advantageous — to fly the sailplane below the level of the towing aircraft for the fugoidal oscillation damping, -— the attachment lock should be built in to the sailplane structure before the gravity center (preferably above its level).