In the past, there have been different devices used to modify the performance characteristics of a winged craft. This includes aircraft as well as land or water craft which use a wing that moves through air or water. Such devices have included adding a propeller on the trailing edge end of such a specially designed wing.
For example, in U.S. Pat. No. Re29,023 to Malvestuto, Jr., the inventor herein, there is disclosed a means and method of rotor-augmented lift for airplanes. In particular, it discloses an aircraft having a wing divided with a semi-circular recess in the trailing edge of the wing. A powered rotor which is rotatable about the axis of the recess, has blades whose tips extend close to the semi-circular edge of the recess, below the upper surface of the wing. The rotor produces direct upward thrust on the aircraft and also creates low pressure over the wings and high pressure below the wings to augment the direct upward thrust of the rotor. Air moving centrifugally impinges on the edged surface of the recess to produce forward thrust.
Another patent of interest is U.S. Pat. No. 3,856,238, also to Malvestuto, Jr., the inventor herein, for an aircraft transporter. The transporter has a plurality of wings each of which has a portion of the trailing edge configured to define a semicircle. A power-driven rotor is mounted in the semicircle on a fixed axis of rotation of the rotor, which is slightly canted relative to the forward direction of aircraft movement to provide a component of forward thrust. In addition, lighter than air buoyancy units are connected to the ends of the wings to provide additional lifting force.
In yet another invention of interest, there is disclosed a high-speed water vessel in U.S. Pat. No. 3,965,836, to Malvestuto, Jr., the inventor herein, which includes rotors located within semicircular shaped recesses in the trailing edges of air foils attached to the water vessel. Rotation of the blades provides thrust forces against the trailing edges of the air foils to propel the vessel forwardly through the water. In addition, lift forces raise the hull of the vessel so the vessel can move through the water at higher speeds.
In spite of the advantages obtained with devices cf the type as described above, there still remains a need for enhancing wing surface aerodynamics and performance to allow additional craft control and propulsion capabilities. For an aircraft, such capabilities would include vertical take-off and landing, extremely low speed flight without degradation of high speed capability, increased cruise range and/or loiter time, increased payload, and safety. For a land craft (i.e., ground vehicle), this would include the capability to reduce unwanted drag in the case of cars or trucks, or to generate additional downward thrust in the case of racing vehicles. For a watercraft, this would include the capability to provide lift and forward thrust. For an underwater craft, this would include enhanced performance and maneuvering capabilities.
For example, in various logistical maneuvers using cargo aircraft, it is desirable for the air craft to have the ability to become airborne at very low speeds. This permits shortened take off and landing distances which can be very critical in certain applications, such as military maneuvering. In addition, it is very desirable to have a wing which has a design so that it tends to prevent a stall condition to occur. A stall condition occurs when the angle of attack of the wing, or the overall angle with respect to the generally horizontal direction of movement, is too steep. In such a case, the normal flow of air across the wing is disrupted, causing the wing to lose all lift capability. In this instance, the aircraft begins to fall, which can be disastrous.
In the past, in order to achieve higher values of wing lift, which is especially critical during take off and landing of the aircraft at low speeds, there has been the use of flaps. Flaps are hinged mechanical devices designed to alter, temporarily, the geometry of the wing. Flaps achieve higher values of wing lift at speeds which are lower than the minimum speed of the aircraft without the use of the flaps, i.e., with the flaps retracted. When flaps are used, however, there is a significant increase in the possibility of wing stall or flow separation. Thus, for many aircraft, the flaps operate in conjunction with other mechanical devices such as leading edge flaps and the like in order to control stall without sacrificing the required lift for take off and landing. Moreover, conventional flap systems are mechanically extremely complicated, and require careful operation by the pilot in order to achieve the desired lift without stalling the wings of the aircraft when in flight.
Another disadvantage is that when flaps are in their operational mode, i.e., deflected, in addition to the desired aerodynamic wing lift, there is a large increment of unfavorable aerodynamic wing drag. The drag penalty due to flap deflection therefore requires additional power and fuel to compensate for this drag, which is the conventional solution. This is in order to safely maintain the appropriate flight speed of the craft during take off, climb to cruise altitude, landing approach, and landing phases of flight. Unfortunately, this aerodynamic drag penalty when the flap is operational, and need for additional power requirements to overcome such drag, is an undesirable result.
Accordingly, it is an object of the present invention to provide a rotor flap apparatus for attachment to the wing of a craft which provides changes in the magnitudes and arrangement of lift and/or drag forces so that the operating performance of the craft is significantly enhanced. The wing can be planar as represented by an aircraft wing, or can be an annular surface such as a ring wing.
It is further an object of the present invention to provide a rotor flap apparatus for attachment to the wing of a craft which lessens the chance of a stall condition, especially during extremely low-speed takeoff and landings in the case of an aircraft.
It is yet another object of the present invention to provide a rotor flap apparatus which does not generate unwanted aerodynamic drag during operation, and therefore, does not require additional power requirements to overcome such drag.
Yet another object of the present invention is to provide such rotor flap apparatus which can improve the performance of a craft by providing forward thrust force for increasing flight speed.
Still another object of the present invention is to provide such rotor flap apparatus which can also provide a rearward acting thrust force for reducing flight speed for steep landing approaches and takeoffs at very low speeds in the case of an aircraft.
Another object of the present invention is to provide a rotor flap apparatus for reducing aerodynamic drag forces acting on a ground vehicle.
A further object of the present invention is to provide a rotor flap apparatus for enhancing the maneuverability of underwater craft.
Another object of the present invention is to construct a rotor flap apparatus which is relatively simple in construction.
Yet another object of the present invention is to construct a rotor flap apparatus which is cost effective in its manufacture, and durable and reliable in use.