A dynamic longitudinal stability analysis for a Canard type airplane in supersonic flight

Abstract

A dynamic longitudinal stability analysis is made for a Canard (tail forward) type airplane in steady horizontal flight at Mach numbers of 1.7 and 1.3. Four different wing configurations (Fig. 1) are investigated: Case I. Delta wing with the Mach wave ahead of the leading edge. The planform of the delta wing is characterized by one-half the apex angle, w[subscript o]. In this case it has been taken to be 18°. Case II. Delta wing with the Mach wave ahead of the leading edge (w[subscript o] = 25°). Case III. Delta wing with the Mach wave behind the leading edge (w[subscript o] = 54°). Case IV. Rectangular, bi-convex, wing with an aspect ratio of 2. The shell or fuselage of the airplane consists of a conical nose and cylindrical afterbody with no boat tailing at the aft end. The stabilizing surface is hi-convex and rectangular in plan form with an aspect ratio of 2. Power is assumed to be supplied by a constant thrust jet motor. Other characteristics may be found in Table I. The design of the airplane is based on the Mach number of 1.7 at an altitude of 30,000 ft. and a gross weight of 10,000 lbs. Static stability is assumed to be the major design variable. The dynamic stability is first investigated for a static stability just sufficient to allow a four-g maneuver without exceeding a 20 degree angle of attack on the fin. Then the static stability is increased in multiples of 2, 3, and 4, to establish a trend. It is found that the effects of compressibility have a powerful influence on some of the coefficients of the stability quartic and hence on the dynamic stability, and that dynamic instability will result in certain cases regardless of the amount of static stability provided.