Airplane with variable-incidence wing

Abstract

The craft is for hovering flight, vertical takeoff and landing, and horizontal forward flight. It has a tail-sitting fuselage and a ducted fan mounted to the fuselage aft to provide propulsion in both (a) hovering and vertical flight and (b) horizontal forward flight. At each side is a floating wing, supported from the fuselage for passive rotation (or an actuator-controlled optimized emulation of such rotation) about a spanwise axis, to give lift in forward flight. The fuselage attitude varies between vertical in hovering and vertical flight, and generally horizontal in forward flight. Preferably the fuselage is not articulated; there is just one fan, the sole source of propulsion, rotating about only an axis parallel to the fuselage; and thrust-vectoring control vanes operate aft of the fan. Preferably at each side a small, nonrotating wing segment is fixed to the fuselage, and the floating wing defines-along its trailing portions-a corner notch or slot near the fuselage; forward portions of the fixed wing segment are within this notch. Preferably the spanwise axis is along a surface of the floating wing, and a long hinge supports that wing from the fixed wing segment, within the notch. During vertical and transitional flight characteristically the leading edge of the floating wing is down relative to the fuselage axis.

Description

BACKGROUND1. Field of the InventionThis invention relates generally to vertical-takeoff-and-landing (VTOL) airplanes; and more particularly to tail-sitting aircraft capable of hovering flight, generally vertical takeoff and landing, and substantially horizontal forward flight.2. Prior ArtTwo types of prior aircraft are pertinent to my invention:ducted -fan craft, such as the French Coleopter (FIG. 8) and the 1972 Shorts Skyspy; and"free wing" or "floating wing" craft in which the wing pivots about a spanwise axis, and is free to float in response to gusts. FIGS. 9 through 12 show a craft of this type, designed by Spratt.In operation near hover, for a given diameter and power, a ducted fan produces more static thrust than an unducted propeller. The Coleopter enjoys this important advantage. Following is an excerpt from Taylor, J. W. R., ed., Jane's Pocket Book of Research & Experimental Aircraft (1976), at page 221, on the "SNECMA C.450-01 Coleopterere". FIG. 8 has been adapted from ...

AI Technical Summary

Benefits of technology

In particular, as compared to prior free-wing configurations of, e.g., Spratt and Stout, my invention shares the advantages of the Coleopter's ducted fan--namely, the very high level of available static thrust that is of enormous value for efficient VTOL and hover operation, and also the greater safety of the guarded fan. On the other hand, by adding a wing that can be of far greater span than the duct diameter, my invention provides induced-drag levels comparable with those of a conventional airplane configuration--and thus is vastly superior in cruise performance to all prior flying-duct craft. Added safety advantages accrue from the stall resistance of the floating wing.

Thus, compared with the Allen or Spratt craft, the "break" in the wing is arranged differently--in such a way that wing bending moments are resisted by the long hinge, instead or being carried on a single short shaft. This saves weight, since the hinge pin can be made smaller and lighter than a shaft.

Problems solved by technology

This small causes span the cruise induced drag (drag due to lift) to be unacceptably high.

Allen's and Spratt's craft are relatively complex in that each requires a separate horizontal tail.

The wing bending moments are carried on a shaft; this wastes weight, because the shaft must be relatively large and heavy.

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