Abstract: Retarding of the point of transition from laminar flow to turbulent flow in aerodynamic boundary layers on the surfaces of aircraft is accomplished by radiating acoustic energy at frequencies greater than twice the critical Tollmein-Schlichting frequency into the boundary layer. The acoustic energy interferes with the formation of Tollmein-Schlichting waves, thereby increasing the incidence of laminar flow and reducing aerodynamic drag.

Abstract: In combination with a propeller disposed in an aircraft, aft from the nose portion of the craft, an improvement is provided for reducing noise, as well as mechanical load on the propeller blade, and includes a construction part situated upstream from the propeller and being exposed to the oncoming air flow prior to reaching the propeller, thus being an obstacle that has a particular contour in a plane transversely to an axis of rotation of the propeller, so that at least the rear edge, as seen in peripheral direction of rotation of the propeller, forms an angle that is not zero in relation to a leading edge of the propeller, when the propeller as a whole is in a horizontal disposition.

Abstract: A turbulence generation inhibitor comprising a fluid conduit having an interior wall surface with the interior wall surface having a plurality of spaced-apart microscopic grooves formed therein which are parallel to the mean-flow direction. Each of the grooves is defined by oppositely disposed side walls with the side walls of each of the grooves having at least one catenary shaped surface provided thereon.

Abstract: The surface of the body is provided with grooves (5), which extend in the flow direction and which are separated from one another by ribs (4) which are constructed to have sharp edges. The surface is composed of a multiplicity of individual elements (3), which have the ribs (4) and grooves (5) on their side facing the flow. The individual elements (3) are disposed relative to one another and/or constructed in such a manner that slits are formed on the side facing the flow between the ribs and grooves. The slits (9) are connected with one another by channels (6) disposed below the surface of the individual elements (3) which faces the flow.

Abstract: A device for reducing the frictional drag inherent in flow mechanics in airborne, waterborne and space vehicles in which the surface of a body in a flowing medium is provided with an asymmetrical microstructure in the form of grooved profiles whose dimensions do not essentially exceed the average free travel length of the molecules of the medium.

Abstract: The turbulent drag is reduced on the surface of a body moving through a fluid by providing longitudinal channels in the surface, for example of an aircraft wing, which channels extend in parallel to the flow direction and which channels are interconnected with the boundary layer by a longitudinal gap communicating the channel with the boundary layer.

Abstract: A fluid flow control for reducing the drag associated with an upswept afterbody includes a pair of ridges forming substantially symmetric flow channels arranged in an approximately helical fashion on either side of the afterbody so as to intersect at approximately the centerline of the undersurface. Each ridge has a generally rearward pitch so that the flow channels form a substantially V-shaped configuration rearwardly. The flow channels cross the local fluid flow streamlines at an optimum angle for producing a strong vortex core along the channel length with the vortex rotating in a direction counter to that normally found in the wake of conventional upswept afterbodies.

Abstract: The invention is a system of flow control devices which result in reduced skin friction on aerodynamic and hydrodynamic surfaces. The devices cause a breakup of large-scale disturbances in the boundary layer of the flow field. Referring to FIGS. 1 and 2, the riblet device 10 acts to reduce disturbances near the boundary layer wall by the use of longitudinal striations forming vee-shaped grooves. These grooves are dimensional on the order of the wall vortices and turbulent burst dimensions 31 depicted in FIG. 3. The large-eddy breakup device 41, depicted in FIGS. 4 and 5, is a small strip or airfoil which is suspended in the upper region of the boundary layer. Various physical mechanisms cause a disruption of the large-scale vortices. The combination of the devices of this invention result in a substantial reduction in skin friction drag.

Abstract: Streamwise ridges on a lifting wing intercept local flow consisting of free stream and spanwise crossflow to create a pattern of vortices over the wing and aligned with the ridge axes; the vortices act as suction pumps collecting low energy boundary layer fluid, ingesting such fluid into the core of the vortices, transporting it in the streamwise direction, and discharging it into the wake. Fresh fluid from the outer, free stream flow replaces the spent fluid withdrawn by the vortex array. This produces a favorable pressure gradient that maintains laminarity, avoiding the onset of boundary layer transition leading to turbulence. The favorable pressure gradient also suppresses separation on the back side of the wing, where the pressure gradient is normally positive and adverse.

Abstract: A cascaded micro-groove aerodynamic drag reducer is provided by creating a plurality of spaced-apart, microscopic grooves in the aerodynamic surface. Each of the grooves is defined by oppositely disposed side walls with each of the side walls of each groove having at least one catenary shaped surface provided thereon. In the preferred embodiment, each of the side walls is provided with a plurality of catenary shaped surfaces with each of the catenary shaped surfaces having a plurality of smaller catenary surfaces provided thereon.

Abstract: A wing-mounted pod for preventing an unstable increase in the pitching moment of a swept-wing aircraft due to increasing speed and angle of attack is disclosed. This invention is for use on a swept-wing aircraft of the type having a nonlinear, unstable increase in its pitching moment due to a loss of lift at the outboard wing above a predetermined angle of attack at high Mach numbers. For an aircraft having a single, strut-mounted engine on each wing, the pod is placed along the intersection of the upper surface of the wing and the inboard side of the engine mounting strut. The pod prevents an increase in the pitching moment by inducing the formation of a shock in the air flowing over the upper surface of the inboard wing at the same angle of attack at which the outboard wing loses lift. The shock causes localized flow separation on the inboard wing, thereby preventing the increase in pitching moment otherwise experienced by the aircraft.

Abstract: A removeable spoiler is described for reducing the wing lift of parked aircraft. It includes a spoiler member in the form of a strip temporarily mountable to stand upright and project into the airstream on the top of the wing. It extends parallel to the wing axis and is supported by a clamp contacting the outer surface of the wing for securing the spoiler to the wing.

Abstract: This invention is for a passive laminar flow airfoil which has an upper skin 12 and lower skin 14 joined at a trailing edge 16. A leading edge structure 20, such as de-icing equipment, is joined to the upper and lower skins by interface mechanisms 30 and 35. Generally, the interface mechanisms are forward facing steps, with or without adjacent gaps, shaped and dimensioned to accomplish laminar flow using standard airfoil manufacturing techniques.

Abstract: An airfoil having improved aerodynamic characteristics incorporates a leading edge (13) and a trailing edge (14) longitudinally displaced therefrom. A continuous lower surface (21), defining the lower camber of the airfoil, extends from the leading edge (13) to the trailing edge (14). The upper surface of the airfoil incorporates a first upper surface (22) extending rearwardly from the leading edge (13) and terminating in an offset (20), and at least a second upper surface (23) extending rearwardly therefrom. The first upper surface (22) defines a first upper camber portion of the airfoil and the second upper surface (23) defines a second upper camber portion thereof.

Abstract: The invention is a small wedge shaped flap (20) for attachment to or near the trailing edge (14) of a airfoil (10) which improves the coefficient of lift and reduces the coefficient of drag providing an overall increase in fuel ecomony at cruise conditions. In detail the wedge shaped flap (20) has a downward height (26) of between 0.5 percent to 1.5 percent of the chord (16) of the airfoil (10) and has an included angle (30) to the chord of between 15.degree. and 45.degree.. The wedge flap is preferably placed at distance (24) of between 0 to 1.0 percent of the chord (16) from the trailing edge (14).

Abstract: One or more channels whose edges generate streamwise vortices from heights coincidental with a local flow-control surface into the channels are used to maintain attached flow of a fluid medium flowing therepast, even in areas of severe regional adverse pressure gradients. The channels are generally triangular in shape with the apex forwardmost in the flow. The channels work very effectively when nested in series and are most effective when the channels extend to the trailing edge of a flow-control surface.

Abstract: An airfoil modification device that helps maintain airstream attachment to either upper or lower airfoil surfaces, the device in the form of a plurality of spaced, low profile rods arranged generally end-to-end and attached to the airfoil and generally normal to the airstream to define a serrated edge that induces multi-directional airstream turbulence.

Abstract: A pair of metallic strips are provided for the improvement in the stalling aerodynamics of the Cessna Series 150 and 152 aircraft, especially during conditions which would otherwise generate an unintentional spin entry, followed by a fatal accident. The strips are secured to the leading edge of the airplane wing at a point substantially adjacent to each wing root. Each strip has a plurality of raised surfaces for modifying the airflow over the upper wing surface, and a concave surface which is placed against the leading edge of the airplane wing. Fasteners placed in recessed areas on the strip secure the strip to the wing's leading edge. The addition of these strips to the airplane wing modify the stall pattern in its area of separated airflow over the upper surface of the wing in such a way that the pilot is provided with greater aileron control during stalling conditions.

Abstract: A drag-reducing structure is provided on a pylon that suspends a wing-mounted engine. The structure reduces drag by preventing ambient airflow, in a region between the wing, pylon, and engine, from accelerating to supersonic velocities and causing shock waves resulting in excessive drag. In one embodiment, the structure is a broad fairing on the inboard vertical surface of the pylon. In another embodiment, the structure is a tapered bump mounted at the inboard intersection between the wing and pylon.

Abstract: Disclosed is an airplane all-moving airfoil having a moment reducing apex for facilitating control of the airfoil. In a preferred embodiment, the apex protrudes forward from the leading edge of an all-moving horizontal stabilizer and operates through its aerodynamic effect on the stabilizer to reduce the moment required to maintain and vary the stabilizer position. Counter-rotating airflow vortices produced by the apex reduce the rearward displacement of the center of pressure on the stabilizer as the stabilizer is deflected into an increasing angle of attack. As a result, lighter weight hydraulic stabilizer and elevator actuating mechanisms can be employed. In a preferred embodiment an aeroelastically flexible apex is employed to enhance moment reduction at high angles of attack.

Abstract: A supercritical wing section having a large average leading edge radius of curvature, followed on the upper surface by a reduction in curvature and then a knee, or region of positively increased curvature, at between 3% and 13%, preferably 5% to 10%, chord the region of increased curvature being followed by a region of low curvature extending for 30% to 90% of the chord, whereby in use of the wing at low speeds the peak velocity and peak suction are contained, in use thereof at intermediate speeds local supersonic expansion is minimized, and in use thereof in supercritical conditions a region of high expansion, stabilized over the region of increased curvature, is created.

Abstract: One or more aerodynamic bodies of preselected shape and placement are employed on the lower surface of an aircraft wing or other aerodynamic lifting surface for the purpose of reducing its drag. These anti-drag bodies singly or collectively provide a reduction in the lower speed profile drag of the associated lifting surface, an increase in its lift at a given angle of attack, and an increase in its critical Mach number.

Abstract: A thin, high performance swept wing of the tapered type with an improved leading edge characterized by (1) camber that increases from a minimum near the wing root to a maximum near the wing tip, and (2) substantially a constant leading edge radius extending substantially across the wing span which defines a "blunt" contour. The wing in combination with a T-tail aircraft with a stick shaker/pusher activated by a rate of change of angle of attack sensor and optionally a strake between the leading edge and a wing tip tank which intrinsically combine to define a system that enhances aircraft performance by reducing minimum airspeed without impairing aircraft performance at high subsonic Mach (M) numbers.

Abstract: Vortex diffusion means for an aircraft having lift structure rooted therein that extends outboard to a structure tip from which a discrete tip vortex develops when said tip is propelled through the air. A sub-wing extends from the tip of the lift structure. Preferably, the sub-wing has its leading edge or upper lead surface tangent to the upper lead surface of the lift structure and a span axis parallel to the span axis of the lift structure. The sub-wing's chord is sized to equally divide the bound vorticity shed at the tip of the lift structure so that twin discrete vortices are generated. One discrete vortex forms along the streamwise edge of the lift structure's tip and the other forms along the streamwise edge of the sub-wing's tip. The distance between the two vortices is in the range of from 25 to 50% of the local chord of the lift structure.