WO2015183347A2

WO2015183347A2 - Flap design for fixed wing aircraft

Info

Publication number: WO2015183347A2
Application number: PCT/US2015/015152
Authority: WO
Inventors: Roy Thompson
Original assignee: Roy Thompson
Priority date: 2014-02-10
Filing date: 2015-02-10
Publication date: 2015-12-03
Also published as: WO2015183347A3

Abstract

A new flap design for fixed wing aircraft increases stability and performance of the aircraft through a wide range of air speeds and flight dynamics when implemented on the flap of a fixed wing aircraft. The flap comprises a step configuration on the underside of the flap. Aircraft may be retrofitted with flaps having the new design.

Description

FLAP DESIGN FOR FIXED WING AIRCRAFT

[0001] FIELD OF THE INVENTION.

[0002] The invention relates to a flap design for fixed wing aircraft comprising a step configuration on the underside of the flap. Implementation of the inventive design on the flap of a fixed wing aircraft increases stability and performance of the aircraft through a wide range of air speeds and flight dynamics. Aircraft may be retrofitted with flaps having the new design.

[0003] BACKGROUND OF THE INVENTION.

[0004] Lift is the force that directly opposes the weight of an aircraft and holds the aircraft in the air. Most of the lift on a normal aircraft is generated by the wings by way of a mechanical aerodynamic force produced by the motion of the aircraft through the air. Lift occurs when a moving flow of gas is turned by a solid object. The flow is turned in one direction, and the lift is generated in the opposite direction, according to Newton's Third Law of action and reaction. In fluid dynamics, air is modeled as a fluid. Faster moving fluid has exerts less pressure than slower moving fluid. What causes lift is introducing a shape into the airflow, which curves the streamlines and introduces pressure changes— lower pressure on the upper surface and higher pressure on the lower surface. This is why a flat surface like a sail is able to cause lift— the distance on each side is the same but it is slightly curved when it is rigged and so it acts as an airfoil. It is curvature that creates lift.

[0005] Lift is a mechanical force. It is generated by the interaction and contact of a solid body with a fluid (liquid or gas). Because lift is a force, it is a vector quantity, having both a magnitude and a direction associated with it. Lift acts through the center of pressure of the object and is directed perpendicular to the flow direction. There are several factors which affect the magnitude of lift.

[0006] For lift to be generated, the solid body must be in contact with the fluid. Without air, there is no lift generated by the wings. Lift is generated by the difference in velocity between the solid object and the fluid. There must be motion between the object and the fluid. Lift acts perpendicular to the motion, while drag acts in the direction opposed to the motion.

[0007] The amount of lift generated by a wing depends on the shape of the airfoil, the wing area, and the aircraft velocity. During takeoff and landing the aircraft's velocity is relatively low. To keep the lift high, with most current airfoil designs, slats are implemented on the wings' leading edges and flaps are implemented on the wings' trailing edges to increase the wing area and change the airfoil shape. The flaps and slats move along metal tracks built into the wings. Moving the flaps aft (toward the tail) and the slats forward increases the wing area. Pivoting the leading edge of the slat and the trailing edge of the flap downward increases the effective camber of the airfoil, which increases the lift. In addition, the large aft-projected area of the flap increases the drag of the aircraft. Flaps are the movable sections of the aircraft's wings closest to the fuselage. Ailerons are the outward movable sections of an aircraft's wings which move in opposite directions (one up, one down) to bank the aircraft.

[0008] There are many different types of flaps, with the specific choice depending on the size, speed and complexity of the aircraft on which they are to be used, as well as the era in which the aircraft was designed. Plain flaps, slotted flaps, and Fowler flaps are the most common. Krueger flaps are positioned on the leading edge of the wings and are used on many jet airliners.

[0009] In a fixed-wing aircraft, the spar is typically the main structural member of the wing, running spanwise at right angles (or thereabouts depending on wing sweep) to the fuselage of the aircraft. The spar carries flight loads and the weight of the wings while on the ground. In some designs, there may be multiple spars in the wing. Most wing structures have two spars, the front spar and the rear spar.

[0010] SUMMARY OF THE INVENTION.

[001 1] The new design for flaps for fixed wing aircraft comprises a flap having a step configuration on the underside of the flap. [0012] In one embodiment, the flap comprises a step configuration located substantially where the flap is adjacent to the wing, on the underside of the flap. The flap comprises a proximal end where it is adjacent to the wing, and a distal end where the flap ends at a trailing edge. The flap further comprises an upper surface and a bottom surface, and an upper proximal edge where the upper surface of the flap is adjacent to the wing and a lower proximal edge where the bottom surface of the flap is adjacent to the wing. The step configuration comprises a first leg having a proximal end rising substantially from the lower proximal edge of the flap along the length of the flap toward the upper surface of the flap at approximately a 40° ± about 3° angle. The 40° angle is measured with respect to a substantially perpendicular line to the span of the spar. The first leg rises at the approximately 40° angle to a point substantially to the halfway point of the height of the spar. The step configuration further comprises a second leg having a proximal end that extends from the upper end of the first leg to the trailing edge of the flap. The length of the step configuration extends spanwise along the length of the flap.

[0013] In one embodiment, the wing has only one spar.

[0014] In one embodiment, the wing has multiple spars. In this embodiment, the step configuration is designed with respect to the spar closest to the proximal end of the flap.

[0015] In other embodiments, the flap may comprise one or more sections. In each embodiment, the step configuration is designed into the section of the flap that comprises the distal edge of the flap.

[0016] BRIEF DESCRIPTION OF THE DRAWINGS.

[0017] Figure 1 depicts a diagram of a prior art wing.

[0018] Figure 2 (a)-(g) depict various prior art flap designs.

[0019] Figure 3 A depicts a side view of a conventional wing and plain flap configuration.

[0020] Figure 3B depicts a side view of the step configuration according to one embodiment of the invention. [0021] Figure 3C depicts a bottom view of a wing and flap with the step configuration according to one embodiment of the invention.

[0022] DETAILED DESCRIPTION OF THE INVENTION.

[0023] The following presents a simplified summary of one or more embodiments of the invention. This summary is not an extensive overview of all contemplated embodiments of the invention, and is intended to neither identify key or critical elements of all embodiments of the invention, nor delineate the scope of any or all embodiments.

[0024] The new design for flaps for fixed wing aircraft comprises a flap having a step configuration on the underside of the flap.

[0025] In one embodiment, the flap comprises a step configuration located substantially where the flap is adjacent to the wing, on the underside of the flap. The flap comprises a proximal end where it is adjacent to the wing, and a distal end where the flap ends at a trailing edge. The flap further comprises an upper surface and a bottom surface, and an upper proximal edge where the upper surface of the flap is adjacent to the wing and a lower proximal edge where the bottom surface of the flap is adjacent to the wing. The step configuration comprises a first leg having a proximal end rising substantially from the lower proximal edge of the flap along the length of the flap toward the upper surface of the flap at approximately a 40° ± about 3° angle. The 40° angle is measured with respect to a substantially perpendicular line to the span of the spar. The first leg rises at the approximately 40° angle to a point substantially to the halfway point of the height of the spar. The step configuration further comprises a second leg having a proximal end that extends from the upper end of the first leg to the trailing edge of the flap. The length of the step configuration extends spanwise along the length of the flap.

[0026] In one embodiment, the wing has only one spar.

[0027] In one embodiment, the wing has multiple spars. In this embodiment, the proximal spar is the spar closest to the proximal edge of the flap. [0028] In other embodiments, the flap may comprise one or more sections. In each embodiment, the step configuration is designed into the section of the flap that is closest to the distal edge of the flap.

[0029] Wind tunnel and actual flight tests conducted on a small single engine aircraft show that when the step configuration is used as the design of the flap of such an aircraft, the change in dynamics included reduced take-off distances, reduced landing distances, increased payload capacities, improved stability in poor environmental conditions and improved fuel economies over the same aircraft not having the step configuration.

[0030] When the aircraft was placed into a stall formation of 18-22° angle of attack or greater, the aircraft did not stall but rather entered into a glide formation. In contrast, this same aircraft without the step configuration enters into a stall at this angle of attack.

[0031] The use of the step configuration does not require a change in wing design over the prior art (other than the use of the step configuration).

[0032] A person having skill in the art of aircraft and airfoil design will be able to design and build airfoils/wings having the step configuration of the invention without undue experimentation. The wing is designed according to prior art principles of flight and aerodynamics, with the flap configured with the step configuration as described herein. The flap having the step configuration can be made of conventional materials now known or later developed, as known to those skilled in the art.

[0033] Turning to the figures, Figure 1 depicts a top perspective view of a prior art wing 100 having a flap 110; a spar 120; an aileron 130; a wing tip 140; stringers 150; ribs 160; a skin 170; and a fuel tank 180. The wing has a leading edge 101 and a trailing edge 102, as well as an upper surface 103 and a bottom surface 104. The flap has a proximal edge 11 1 where it is attached to the wing 100, and also a distal edge 112. The spar 120 has a height as measured between its top end 121 and bottom end 122. [0034] Figure 2 (a)-(f) depict side views of various prior art flap designs. Figure 2(a) depicts a wing 200 with a plain flap 201 that rotates downwards on a simple hinge 205 mounted at the front of the flap 201 to attach it to wing 200.

[0035] Figure 2(b) depicts a wing 210 with slotted flap 21 1 having a gap 215 between the flap 21 1 and the wing 210, that forces high pressure air from below the wing 210 over the flap 21 1.

[0036] Figure 2(c) depicts a wing 220 with a split flap 221 where the rear portion of the lower surface of the flap 221 hinges downwards from the leading edge of the flap 221, while the upper surface stays immobile.

[0037] Figure 2(d) depicts a wing 230 with a Zap flap 231 where the leading edge of the flap 231 is mounted on a track, while a point 232 at mid chord on the flap 231 is connected via an arm to a pivot just above the track. When the flap's leading edge moves aft along the track, the triangle formed by the track, the shaft and the surface of the flap (fixed at the pivot) gets narrower and deeper, forcing the flap 231 down.

[0038] Figure 2(e) depicts a wing 240 with a Fowler flap 241 split flap that slides backward flat, before hinging downward, thereby increasing first chord, then camber.

[0039] Figure 2(f) depicts a wing 250 with a double slotted Fowler flap 251.

[0040] Figure 3A depicts a side view of a wing 300 having a plain flap 310.

[0041] Figure 3B depicts a side view of the step configuration 320 according to one embodiment of the invention. In this embodiment, step configuration 320 has been applied to a plain flap as depicted in element 310 in Figure 3A. Flap 310 comprises a proximal end where it is adjacent to the wing 300, and a distal end at the trailing edge of the flap 310. Flap 310 further comprises an upper surface 314 and a bottom surface 315, and a lower proximal edge where the bottom surface 315 of the flap 310 is adjacent to the wing 300. Step configuration 320 comprises a first leg having a proximal end along the points where flap 310 is attached to the bottom surface 315 of the wing 300, starting at Point A and extending toward the upper surface 314 of flap 310 at approximately a 40° ± about 3° angle. The 40° ± about 3° angle is measured with respect to a line F-G that is substantially perpendicular to the span of wing spar (B-B ) that is closest to flap 310. The first leg rises at the approximately 40° angle to a distal end point (Point C) that is located substantially at the halfway point of the height of the proximal spar (Point D). The step configuration 320 further comprises a second leg having a proximal end that extends from distal end point C to the trailing edge of the flap 310, ending at E.

[0042] The length of step configuration 320 extends the length of flap 310 as seen in Figure 3C, which is a bottom view of a wing 300 having the step configuration 320 in this embodiment of the invention.

[0043] Where wing 300 comprises multiple spars 330i, the step configuration is measured from the spar 330 closest to the flap 310.

[0044] Where flap 310 comprises a configuration other than a plain flap, such as the flap designs shown in Figures 2(a)-2(f) having multiple flap sections, step configuration 320 is designed into the section of the flap that is on the bottommost surface of the flap and the most distal section of the flap from the wing.

[0045] In some embodiments, a wing may be designed with multiple flaps, in which case the step configuration is designed into each flap using the same principles.

[0046] While certain embodiments have been described, they are merely explanations and not restrictive of the broad invention, and that this invention not be limited to the specific constructions and arrangements described, since various other changes, combinations, omissions, modifications and substitutions, in addition to those set forth in the above paragraphs, are possible. Those skilled in the art will appreciate that various adaptations, combinations, and modifications of the just described embodiments can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.

Claims

CLAIMS What is claimed is:

1. A flap for a fixed wing aircraft comprising:

an upper surface;

a lower surface; and

a step configuration on the lower surface of the flap;

wherein the step configuration is defined by a first leg having a first leg proximal end extending from the lower surface of the flap adjacent to the wing to which the flap is attached toward the upper surface of the flap and ending at an upper first leg endpoint, and a second step leg extending from the first leg endpoint to the trailing edge of the flap;

wherein the first step leg extends from the first leg proximal end upward toward the upper surface of the flap to a point located substantially at the midpoint of the height of the spar in the wing;

wherein the first step leg comprises an angle of about 37° to about 43° with respect to an imaginary line that extends perpendicular to the span of a spar in the fixed wing of the aircraft.

2. The flap of claim 1, wherein the first step leg and the imaginary line define an angle of about 38° to about 42°.

3. The flap of claim 2, wherein the first step leg and the imaginary define an angle of about 39° to about 41°.

4. The flap of claim 3, wherein the first step leg and the imaginary line define an angle of about 40°.

5. The flap of any of claims 1 to 4, wherein the first step leg comprises a substantially straight line.

6. The flap of claim 5, wherein the spar comprises the spar closest to the flap if the wing comprises multiple spars.

7. The flap of claim 5, wherein the step configuration is disposed on the bottommost surface and the most distal section of the flap where the flap comprises a plurality of sections.

8. A wing for a fixed wing aircraft comprising:

a spar attached within the interior of the wing extending spanwise substantially in a perpendicular direction from the fuselage of the fixed wing aircraft;

an upper airfoil surface;

a lower airfoil surface; and

a flap comprising a step configuration on the lower surface of the slap; wherein the flap comprises:

an upper surface;

a lower surface; and

a step configuration on the lower surface of the flap;

wherein the step configuration is defined by a first leg having a first leg proximal end extending from the lower surface of the flap adjacent to the wing to which the flap is attached toward the upper surface of the flap and ending at an upper first leg endpoint, and a second step leg extending from the first leg endpoint to the trailing edge of the flap; wherein the first step leg extends from the first leg proximal end upward toward the upper surface of the flap to a point located substantially at the midpoint of the spar in the wing that is closest to the flap;

wherein the first step leg comprises an angle of about 37° to about 43° with respect to an imaginary line that extends perpendicular to the span of the spar in the fixed wing of the aircraft.

9. The wing of claim 8, wherein the first step leg and the imaginary line define an angle of about 38° to about 42°.

10. The wing of claim 9, wherein the first step leg and the imaginary line define an angle of about 39° to about 41°.

11. The wing of claim 10, wherein the first step leg and the imaginary line define an angle of about 40°.

12. The wing of any of claims 8 to 11 , wherein the first step leg comprises a substantially straight line.

13. The wing of claim 12, wherein the spar comprises the spar closest to the flap if the wing comprises multiple spars.

14. The wing of claim 12, wherein the step configuration is disposed on the bottommost surface and the most distal section of the flap where the flap comprises a plurality of sections.