GURNEY FLAP

Abstract

A gurney flap arrangement comprises: an airfoil with an opening in a surface of the airfoil; a gurney flap having a first position in which at least a portion of the gurney flap extends through the opening and projects outwardly from the airfoil surface, and a second position in which the gurney flap does not project from the airfoil surface or projects outwardly from the airfoil surface to a lesser extent; and a seal disposed about the opening to seal a gap in the opening between the gurney flap and the airfoil.

Claims

1. A gurney flap arrangement comprising: an airfoil with an opening in a surface of the airfoil; a gurney flap having a first position in which at least a portion of the gurney flap extends through the opening and projects outwardly from the airfoil surface, and a second position in which the gurney flap does not project from the airfoil surface or projects outwardly from the airfoil surface to a lesser extent; and a seal disposed about the opening to seal a gap in the opening between the gurney flap and the airfoil.

2. A gurney flap arrangement as claimed in claim 1, wherein the opening comprises a slot, wherein in the first position the gurney flap extends out of the slot, and wherein in the second position the gurney flap is withdrawn into the slot.

3. A gurney flap arrangement as claimed in claim 1, wherein the gap between the gurney flap and the airfoil surrounds the gurney flap within the opening, and the seal bridges the gap between the gurney flap and the airfoil.

4. A gurney flap arrangement as claimed in claim 1, wherein in the second position the gurney flap is flush with an envelope of the airfoil.

5. A gurney flap arrangement as claimed in claim 1, wherein the seal comprises seal body, preferably wherein the seal body is made of a single homogeneous material.

6. A gurney flap arrangement as claimed in claim 5, wherein the seal body comprises self-lubricating material, preferably wherein the seal body comprises PTFE, graphite, or molybdenum di-sulphide.

7. A gurney flap arrangement as claimed in claim 5, wherein the seal body comprises a scraper lip in contact with the gurney flap and configured to bear against a side of the gurney flap during transition of the gurney flap between first and second positions.

8. A gurney flap arrangement as claimed in claim 5, wherein the seal comprises biasing means to urge the seal body, and preferably the scraper lip, to bear against the gurney flap.

9. A gurney flap arrangement as claimed in claim 1 wherein the seal comprises a slot, and wherein in the first position the gurney flap extends out of the slot, and in the second position the gurney flap is withdrawn into the slot.

10. A gurney flap arrangement as claimed in claim 1, wherein the seal comprises a cap section fixed to an end of the gurney flap.

11. A gurney flap arrangement as claimed in claim 10, wherein the seal comprises a fold section connecting the cap section to the airfoil, wherein in the first position the fold section defines a surface curving out from the airfoil towards the end of the gurney flap, and wherein in the second position the fold section retracts into the airfoil.

12. A gurney flap arrangement as claimed in claim 1, wherein the seal completely covers the opening and fully encloses the gurney flap.

13. A method of manufacturing a gurney flap arrangement comprising: an airfoil, a gurney flap, and a seal; the method comprising: providing an opening in the airfoil; arranging the gurney flap so that it has a first position in which at least a portion extends through the opening and projects from the airfoil, and a second position in which the gurney flap does not project from the airfoil; positioning the seal about the opening to seal a gap in the opening between the gurney flap and the airfoil.

Description

[0019] An exemplary embodiment of the present disclosure will now be described by way of example only and with reference to the accompanying drawings in which:

[0020] FIG. 1 shows an exemplary airfoil with a gurney flap;

[0021] FIG. 2 shows a view of a gurney flap arrangement;

[0022] FIG. 3A shows a section view of the arrangement of FIG. 2 with the gurney flap in a first position;

[0023] FIG. 3B shows a section view of the arrangement of FIGS. 2 and 3A with the gurney flap in a second position;

[0024] FIG. 4A shows a section view of an alternative arrangement with a gurney flap in a first position;

[0025] FIG. 4B shows a section view of the alternative arrangement of FIG. 4A with the gurney flap in a second position.

[0026] FIG. 1 shows a gurney flap arrangement comprising an airfoil 10, an actuator 12, a flexible member 14, an opening 17, and a gurney flap 20. FIG. 1 shows the gurney flap 20 in a first, stowed position, and the insert shows the gurney flap 20 in a second, deployed position. The opening 17 can be clearly seen in FIG. 1, and permits ingress of atmospheric debris (dust, ice, and water etc.) into the airfoil structural cavity during the gurney flap operation.

[0027] The airfoil 10 is a main rotor blade of a rotary wing aircraft mounted to a rotor hub. The airfoil 10 has a pressure side 11, a suction side 13, a main spar 15, a leading edge 18, and a trailing edge 19. The gurney flap 20 is deployed to increase the rotor blade lift during blade rotation. The gurney flap 20 is retracted during other parts of blade rotation to decrease drag.

[0028] FIG. 2 shows a gurney flap arrangement 100 disposed on the pressure side of an airfoil 110 near the trailing edge. The gurney flap 120 has rectangular cross-section with rounded corners disposed approximately in the centre of an opening 170 formed in the airfoil 110. A seal 150 is disposed within the opening 170 in the airfoil 110 and surrounds the gurney flap 120, bridging and covering a gap between the gurney flap 120 and the edge of the opening 170. The seal 150 is flexible and has a slot (e.g. an elongate letterbox shaped hole) through which the gurney flap 120 passes. The edge of the slot of the seal 150 defines a scraper lip 152, which is urged into contact with the gurney flap 120 by spring 140 (shown in dashed outline in FIG. 2).

[0029] FIG. 3A shows the view of section A-A of FIG. 2. The seal 150 is bonded on to the structure of the airfoil 110 around the edge of the opening 170 at bonding portions 154. The gurney flap 120 is shown in the first (deployed) position and hence extends through the slot in the seal 150 and projects from the surface of the airfoil 110. In the first position the gurney flap 120 increases the lift of the airfoil 110. The seal 150 has an overall outward curvature (albeit a small curvature) so that the scraper lips 152 meet the gurney flap 120 at an angle. The scraper lips 152 continuously contact the sides and edges (not shown in FIG. 3A) of the gurney flap 120, biased by the spring 140 disposed within the opening 170 and within the seal 150, positioned against the edge of the opening 170 in the airfoil 110. The seal 150 is energised continuously by the spring 140 (or any other suitable elastomeric or metallic spring energisers).

[0030] The gurney flap 120 is moved (e.g. by an actuator) in the directions indicated by arrow 190. FIG. 3B shows the gurney flap 120 in the second (stowed) position. As the gurney flap 120 is withdrawn into the interior of the airfoil 110, it slides past scraper lips 152, which clean off any accumulated debris. Thus, not only does the seal prevent ingress of atmospheric debris by sealing the gap in the opening 170, but the scraper lips 152 ensure that no debris is transported into the airfoil 110 when the gurney flap 120 is stowed.

[0031] In the second position, the end of the gurney flap 120 is flush with the outer surface of the airfoil 110. The gurney flap 120 may be withdrawn so that the seal 150 is flush with the pressure side surface of the airfoil 110.

[0032] The seal 150 may be made of self-lubricated material such as PTFE, graphite, molybdenum di-sulphide or any other suitable self-lubricated elastomeric material. The gurney flap 120 may be made of metallic materials or non-metallic composite materials. The contact surfaces of the gurney flap 120 may also be coated, for example with graphite or tungsten carbide to provide high wear resistance and self-lubrication.

[0033] FIG. 4A shows an alternative gurney flap arrangement 200. A cross-section through the arrangement is shown when the gurney flap 220 is deployed in the first position. The seal 250 is bonded to the airfoil 210 at bonding portions 254 and is also bonded to the end of the gurney flap 220 at cap portion 252. Fold portions 256 connect the cap portion 252 to the bonding portions 254, and hence the depicted arrangement fully seals the inside of the airfoil 210 from atmospheric media whilst allowing the gurney flap 220 to deploy and retract.

[0034] The opening 270 in the airfoil 210 is clearly visible in FIG. 4A, with the gurney flap 220 disposed approximately in the centre. The fold sections 256 curve outward from the bonding sections 254 at the edge of the opening 270 to connect to the cap section 252 at the end of the gurney flap 220. Therefore, the seal 250 itself provides the aerodynamic surface of the gurney flap 220, with the gurney flap 220 providing the required support.

[0035] FIG. 4B depicts the gurney flap arrangement 200 of FIG. 4A with the gurney flap 220 in the second (stowed) position. When the gurney flap 220 is fully retracted into the interior of the airfoil 210, the cap section 252 of the seal 250 is flush with the outer surface of the airfoil 210. The fold sections 256 are folded back into the interior of the airfoil 210, and parts of the opening 270 are thus external to the seal arrangement. Those regions may be sized such that they are not detrimental to the overall aerodynamics of the airfoil.

[0036] The gurney flap arrangements 100, 200 described herein and depicted in the figures may be used to prevent the ingress of atmospheric debris into an airfoil during use of a gurney flap. They provide a simple, robust design for a sealing system for a gurney flap which improves seal integrity and reliability. The arrangements provide complete seals for isolating the atmospheric side of the airfoil from the interior. Due to their simplicity and robustness, the arrangements can be used in high g-force environments, for example at 700g. Finally, the moulded seal structure with bonding provides a minimum space envelope and weight reduction, as well as a minimum number of moving parts.

[0037] While the arrangements have been shown and described with reference to exemplary embodiments, those skilled in the art will appreciate that changes and/or modifications may be made thereto without departing from the scope of the present disclosure as defined by the appended claims.