Patent GB-191228440-A (GB)
Title: Improvements in or relating to the Stability of Flying Machines.
Inventor: CAREY HIRZEL DENIS DE MUSSENDE
IPC: B64C3/14
Filed: 1912-12-10
Granted: 1913-12-10
Abstract: 28,440. Carey, H. D. de M. Dec. 10. [Cognate Application, 7186/13.] Planes and the like, construction of; steering and balancing; cars.-Supporting and controlling surfaces are so formed that vertical sections taken in different directions give curves which vary in such a way that when the wind veers, or the surface is rotated, about an axis more or less normal to the surface, a regular variation of pressure results. Fig. 1 shows a plan view of a pair of supporting- surfaces A B, E D arranged on opposite sides of the plane of symmetry S Y of the machine, the edges AB being in front. Sections of the surfaces taken parallel to the plane of symmetry may give straight lines or curves. The middle points of such straight lines of surface or of the chords of such curves lie along the line C C', and the invention consists in designing each surface so that the heights of these middle points above an horizontal plane do not increase with increase in distance from the plane of symmetry, while the angles of incidence of these straight lines of surface or chords increase algebraically with increase of distance from the plane of symmetry, especially at a distance from that plane. When the relative wind veers so as to take such a path as from W to F across the windward wing and from L<1> to G<1> across the leeward wing, it acts, upon the windward wing, upon curves W K F, Figs. 1 and 2, of under surface which, as the angle of inclination of the direction of the wind to the plane of symmetry increases, increase in convexity-or decrease in concavity-with or without a small decrease in the angle of incidence of the chord W F, Fig. 2 ; while, on the leeward wing, the curvatures of the arcs L<1> K<1> G<1>, and the incidences of the chords L<1> G<1>, in the path of the wind change in the opposite sense as the wind veers. The pressure on the windward wing is thus reduced, and that on the leeward wing is increased, so that the lateral equilibrium of the machine is maintained. A discussion of the conditions for the occurrence of points of inflexion in the sections inclined to the plane of symmetry is given in the Specification, surfaces having the forms of a hyperbolic paraboloid and a right conoid being specially considered. The points of inflexion, when they occur, can be confined to sections quite close to the plane of symmetry. The surfaces usually have a continuous curvature, but they may be formed by a series of lines making very small angles with one another. Fig. 10 shows a section of a wing, taken parallel to the plane of symmetry of the machine, in which the section of the upper surface is straight at the rear half and increases in curvature towards the leading edge A. The sections of the upper surface may decrease in camber with increase of distance from the plane of symmetry, and if the rear edge of the wing is of appreciable thickness nearest the plane of symmetry, Fig. 13, and decreases in thickness towards the lateral extremity E of the wing, as shown in Fig. 14, the upper sections may decrease in camber while the chords of the upper surface have a greater increase of angle of incidence with distance from the plane of symmetry than the chords of the under surface. These surfaces may be designed to give longitudinal stability, and, in addition, the machine may, for this purpose, be filled with a fixed head or tail plane of the form described above. For a tail' plane, a surface approximating in form to a hyperbolic paraboloid is especially suitable, the surface, shown in plan in Fig. 9, being so set that a vertical section through M C M', in the plane of symmetry of the machine, gives a parabola which is convex below and of maximum curvature, while a section through N C N', at right angles to the plane of symmetry of the machine, gives a parabola of maximum curvature with its concavity downwards. For manual operation, a surface similar to that just described may be rotatable about a normal axis through C. A pair of such rotatable surfaces may form the wings of an aeroplane. According to Provisional Specification 28,440/12, which deals with surfaces forming a portion of a hyperbolic paraboloid or an approximation thereto, the body of the machine may taper rearwardly from the points C C, Fig. 1, the rear inside corners of the wings being cut away so as to leave a rearwardly widening space on both sides of the body.