Aerofoil and wings for air vehicles

Patent metadata

Field	Value
Publication number	US-2016137288-A1
Application number	US-201414896828-A
Country	US
Kind code	A1
Filing date	Jun 8, 2014
Priority date	Jun 10, 2013
Publication date	May 19, 2016
Grant date	—

Abstract

Two element aerofoils are provided, having an aerofoil chord, a primary element having a first leading edge and a first trailing edge, a secondary element having a second leading edge and a second trailing edge, a gap between the primary element and the secondary element, and an axial overlap between the first trailing edge and the second leading edge. The secondary element is deflectable with respect to the primary element about a fixed hinge point by a flap deflection angle. The secondary element is configured to operate in airbrake mode when deflected by a respective the flap deflection angle corresponding to a design airbrake deflection angle wherein to generate an airbrake drag. In at least some examples, the axial overlap is numerically greater than −0.5% of the aerofoil chord, at least for the design airbrake deflection angle. Also disclosed are methods for operating air vehicles, and methods for designing two-element aerofoils.

First claim

1 . Two element aerofoil, having an aerofoil chord, a primary element having a first leading edge and a first trailing edge, a secondary element having a second leading edge and a second trailing edge, a gap between the primary element and the secondary element, and an axial overlap between the first trailing edge and the second leading edge, the secondary element being deflectable with respect to the primary element about a fixed hinge point by a flap deflection angle, the secondary element being configured to operate in airbrake mode when deflected by a respective said flap deflection angle corresponding to a design airbrake deflection angle wherein to generate an airbrake drag, wherein at least for said design airbrake deflection angle said axial overlap is numerically greater than −0.5% of the aerofoil chord.

2 . The aerofoil according to claim 1 , wherein said design airbrake deflection angle is greater than 40°.

3 . The aerofoil according to claim 1 or claim 2 , wherein said design airbrake deflection angle is greater than 45°.

4 . The aerofoil according to any one of claims 1 to 3 , wherein said design airbrake deflection angle is greater than 55°.

5 . The aerofoil according to any one of claims 1 to 4 , wherein said airbrake drag corresponds to an airbrake aerofoil drag coefficient that is at least 150% greater than a datum drag coefficient of the aerofoil at a zero said flap deflection angle.

6 . The aerofoil according to claim 5 , wherein said airbrake aerofoil drag coefficient is greater than 0.15.

7 . The aerofoil according to claim 5 or claim 6 , wherein said airbrake aerofoil drag coefficient is greater than 0.2.

8 . The aerofoil according to any one of claims 5 to 7 , wherein said airbrake aerofoil drag coefficient is greater than 0.3.

9 . The aerofoil according to any one of claims 1 to 8 , wherein the primary element is configured for providing high lift mild stall characteristics, and wherein the aerofoil is configured to generate said airbrake drag while concurrently retaining said mild stall characteristics.

10 . The aerofoil according to any one of claims 1 to 9 , wherein at least for said design airbrake deflection angle said axial overlap is between −0.5% and +4% of the aerofoil chord.

11 . The aerofoil according to any one of claims 1 to 10 , wherein said axial overlap provides a smooth variation of aerofoil maximum lift coefficient with said flap deflection angle for a range of said flap deflection angles at least ±10° from said design airbrake deflection angle.

12 . The aerofoil according to any one of claims 1 to 10 , wherein at said axial overlap, the aerofoil maximum lift coefficient is maintained constant within 0.1 with said flap deflection angle for a range of said flap deflection angles at least ±10° from said design airbrake deflection angle.

13 . The aerofoil according to any one of claims 1 to 12 , wherein a value for said axial overlap is chosen to maximize the maximum lift coefficient obtained for the aerofoil at said design airbrake deflection angle.

14 . The aerofoil according to any one of claims 1 to 13 , wherein said secondary element is in the form of a slotted flap.

15 . The aerofoil according to any one of claims 1 to 14 , wherein the secondary element is deflectable with respect to the primary element about said fixed hinge point to provide said flap deflection angle ranging between about −15° and +60°.

16 . The aerofoil according to any one of claims 1 to 15 , wherein, at said design airbrake deflection angle, at least a majority of an airflow over said secondary element is fully detached.

17 . The aerofoil according to any one of claims 1 to 16 , wherein at said design airbrake deflection angle said aerofoil generates a maximum lift coefficient greater than 2.5.

18 . The aerofoil according to any one of claims 1 to 17 , wherein at said design airbrake deflection angle corresponds to a design Reynolds number of between 0.3*10 6 and 1.0*10 6 .

19 . The aerofoil according to any one of claims 1 to 18 , wherein at said design airbrake deflection angle corresponds to a design Reynolds number of 0.4*10 6 .

20 . Two element aerofoil, having an aerofoil chord, a primary element having a first leading edge and a first trailing edge, a secondary element having a second leading edge and a second trailing edge, a gap between the primary element and the secondary element, and an axial overlap between the first trailing edge and the second leading edge, the secondary element being deflectable with respect to the primary element about a fixed hinge point by a flap deflection angle, the secondary element being configured to operate in airbrake mode when deflected by a respective said flap deflection angle corresponding to a design airbrake deflection angle wherein to generate an airbrake drag, wherein a value for said axial overlap is chosen to maximize the maximum lift coefficient obtained for the aerofoil at said design airbrake deflection angle.

21 . The aerofoil according to claim 20 , wherein said design airbrake deflection angle is greater than 40°.

22 . The aerofoil according to claim 20 or claim 21 , wherein said design airbrake deflection angle is greater than 45°.

23 . The aerofoil according to any one of claims 20 to 22 , wherein said design airbrake deflection angle is greater than 55°.

24 . The aerofoil according to any one of claims 20 to 23 , wherein said airbrake drag corresponds to an airbrake aerofoil drag coefficient that is at least 150% greater than a datum drag coefficient of the aerofoil at a zero said flap deflection angle.

25 . The aerofoil according to claim 24 , wherein said airbrake aerofoil drag coefficient is greater than 0.15.

26 . The aerofoil according to claim 24 or claim 25 , wherein said airbrake aerofoil drag coefficient is greater than 0.2.

27 . The aerofoil according to any one of claims 24 to 26 , wherein said airbrake aerofoil drag coefficient is greater than 0.3.

28 . The aerofoil according to any one of claims 20 to 27 , wherein the primary element is configured for providing high lift mild stall characteristics, and wherein the aerofoil is configured to generate said airbrake drag while concurrently retaining said mild stall characteristics.

29 . The aerofoil according to any one of claims 20 to 28 , wherein at least for said design airbrake deflection angle said axial overlap is numerically greater than −0.5% of the aerofoil chord.

30 . The aerofoil according to any one of claims 20 to 29 , wherein at least for said design airbrake deflection angle said axial overlap is between −0.5% and +4% of the aerofoil chord.

31 . The aerofoil according to any one of claims 20 to 30 , wherein said axial overlap provides a smooth variation of aerofoil maximum lift coefficient with said flap deflection angle for a range of said flap deflection angles at least ±10° from said design airbrake deflection angle.

32 . The aerofoil according to any one of claims 20 to 30 , wherein at said axial overlap, the aerofoil maximum lift coefficient is maintained constant within 0.1 with said flap deflection angle for a range of said flap deflection angles at least ±10° from said design airbrake deflection angle.

33 . The aerofoi

Assignees

• Israel Aerospace Ind Ltd

Inventors

• Shepshelovich Michael
• Abramov Danny

Classifications

• B64C3/50

  by leading or trailing edge flaps · CPC title

• B64C2230/20

  by passively inducing fluid flow, e.g. by means of a pressure difference between both ends of a slot or duct · CPC title

• B64C3/14

  Aerofoil profile · CPC title

• B64C2003/147

  comprising trailing edges of particular shape · CPC title

• B64C9/20 Primary

  by multiple flaps · CPC title