WO2007117260A2

WO2007117260A2 - Aircraft with belly flaps

Info

Publication number: WO2007117260A2
Application number: PCT/US2006/029455
Authority: WO
Inventors: Ron Blackwelder; Mark Page; Yann Staelens
Original assignee: University Of Southern California
Priority date: 2005-07-27
Filing date: 2006-07-27
Publication date: 2007-10-18
Also published as: EP1917186A2; WO2007117260A3

Abstract

A blended wing body aircraft may include a blended wing configured to house a person, payload and/or cargo within the wing, a surface structure, and an actuator. The actuator may be configured to controllably cause the planar structure to extend downwardly from an underside surface of the wing oriented such that the planar structure forms a sweep angle with the aircraft between -70 and 70 degrees. Substantially each point on the planar structure may be behind a leading edge of the wing and in front of a trailing edge of the wing by at least 5% of the length of the chord of the wing that passes through the point. The actuator may be configured to controllably cause the planar structure to extend downwardly from an underside surface of the wing with an orientation that causes an increase in static pressure ahead of the hinge line of the planar structure and a decrease aft of the hinge line during forward movement of the aircraft, as compared to when the planar structure is not extended. Deployment of all planar structures may increase the aircraft's control pitching moment and/or lift by more than 5 percent as compared to when they are not deployed.

Description

AIRCRAFT WITH BELLY FLAPS

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is based upon and claims priority to U.S. Provisional Patent Application Serial Number 60/702,912, entitled "Belly Spoiler for Pitching Moment Control," filed July 27, 2005, attorney docket number 28080-183, the entire content of which is incorporated herein by reference.

BACKGROUND

[0002] Technical Field

[0003] This application relates to aircraft, including aircraft that utilize a blended wing body.

[0004] Description of Related Art

[0005] Some aircraft have what is known as a Wended wing body. These are usually tailless aircraft in which persons, payloads, and/or cargo are held within the wing itself.

[0006] Blended wing body aircraft often have less effective pitching moment controls. The pitch controls of such aircraft often have a shorter lever arm from the control surface to the center of gravity than a conventional tailed airplane. Their instantaneous center of percussion, is therefore located closer to their centers of gravity, as compared to conventional aircrafts. This may cause the instantaneous center of rotation to be further ahead of the center of gravity. As compared to conventional aircraft, therefore, more force must often be asserted on the blended wing body aircraft in order to obtain an equivalent change in pitch, since the moment arm is smaller. This can introduce larger lift losses and cause the blended wing body aircraft to plunge downward in order to reach a higher prtch angle. This may cause "sagging" in the flight paflt of the blended wing body aircraft during takeoff and landing. This plunging may be undesirable and a form of temporary control reversal. In many aircraft, the pilot may command a nose up pitch to elevate the flight path. The initial flight path sagging that may be caused by the short-coupled controls may be in opposition to the pilot's intent.

LAS99 1465Q64-1.028080.0213 - 1 - SUMMARY

[0007] A blended wing body aircraft may include a blended wing configured to house a person, payload and/or cargo within the wing, a surface structure, and an actuator. The actuator may be configured to controllably cause the planar structure to extend downwardly from an underside surface of the wing with a hinge line of the planar surface oriented such that the planar structure forms a sweep angle with respect to the perpendicular to the aircraft's centerline between -70 degrees and +70 degrees, which in some embodiments may be between -10 and 50 degrees. Substantially each point on the planar structure may be behind a leading edge of the wing and in front of a trailing edge of the wing by at least 5% of the length of the chord of the wing that passes through the point.

[0008] The blended wing body aircraft may include one or more additional surface structures, each associated with an actuator that is configured to controllably cause each additional planar structure to extend downwardly from the underside surface of the wing. All of the planar structures may form a substantially continuous surface that has a centerline that substantially coincides with the centerline of the aircraft. The total span of the planar structures may be between 10 and 100 percent of the span of the wing.

[0009] The actuator may be configured to controllably cause the planar structure to form a deployment angle with a trailing portion of the underside surface of the wing that is between 10 and 170 degrees.

[0010] The sweep angle of the planar structure may be between -70 degrees to +70 degrees with most applications being between -10 and the sweep angle of the wings.

[0011] Substantially every one of the points on the planar structure may be located behind the leading edge of the wing by at least 20% and in front of the trailing edge of the wing by at least 35% of the length of the chord of the wing that passes through the point.

[0012] The actuator may be configured to controllably retract the planar structure from its downwardly extending position until the planar structure is substantially flush with the underside surface of the wing.

LAS99 1465064-1.028080.0213 - 2 - [0013] The wing may include a landing gear well and the actuator may be configured to retract the planar structure into a position covering or within the landing gear well.

[0014] The planar structure may have a substantially rectangular or trapezoidal shape and/or a lower edge that is curved and/or serrated.

[0015] The surface structure may have a surface comprised of rigid, semi-rigid or flexible material. The material may enable the surface to deform in response to aerodynamic pressures. The surface may take on a parachute-like configuration. The surface may be made of any material, such as fabric, screen, another type of flexible membrane, or plastic. The surface may be continuous and supported on a rigid or non-rigid means of retention, such as a frame. The geometry of this membrane may have a substantially rectangular or trapezoidal shape and/or a lower edge that is curved and/or serrated. The membrane may have perforations.

[0016] The actuator may be configured to controllably cause the planar structure to extend with an orientation that causes an increase in static pressure ahead of the aircraft's center of gravity and a decrease aft during forward movement of the aircraft, as compared to when the planar structure is not extended, thereby producing a nose-up pitching moment.

[0017] The actuator may be configured to controllably cause all planar structures to extend so as to increase the aircraft's nose up control pitching moment by more than 5 percent and, in certain embodiments, with no material loss of lift, as compared to when the planar structures are not extended.

[0018] The actuator may be configured to controllabiy cause the planar structures to extend so as to increase the aircraft's lift by more than 5 percent with no material loss of pitching moment as compared to when the planar structures are not extended.

[0019] A process for taking off or landing an aircraft having a wing and a surface structure may include extending the planar structure downwardly from an underside surface of the wing and taking off and/or landing the aircraft. The planar structure may be retracted after takeoff and/or landing.

[0020] One or more of the features and/or steps that have been described may be used in connection with a conventional aircraft that has a tail and a fuselage configured to house persons, payloads and/or cargo.

LAS99 1465064-1.Q28080.0213 - 3 - [0021] These, as well as other components, steps, features, objects, benefits, and advantages, will now become clear from a review of the following detailed description of illustrative embodiments, the accompanying drawings, and the claims.

BRIEF DESCRIPTION OF DRAWINGS

[0022] FIG. 1 is a side view of a blended wing body aircraft with an extended belly flap having substantially no sweep.

[0023] FIG. 2 is a front view of the blended wing body aircraft shown in FIG. 1.

[0024] FIG. 3 is a top view of the blended wing body aircraft shown in FIG. 1 but with a sweep added to the belly flaps.

[0025] FIG. 4 is a side view of the blended wing body aircraft shown in FIG. 1 with the belly flaps retracted.

[0026] FIG. 5(a) illustrates a belly flap in a retracted position covering a landing gear well.

[0027] FIG. 5(b) illustrates the belly flap of FIG. 5(b) in an extended position with the landing gear also extended.

[0028] FIGS. 6(a)-(d) illustrate variations in the shapes of belly flaps.

[0029] FIGS. 7(a)-(d) illustrate various patterns of porous openings in belly flaps.

[0030] FIGS. 8(a)-(d) illustrate variations in the lower edges on belly flaps. The side edges may be similarly configured.

[0031] FIGS. 9(a)-(b) illustrate particular patterns of porous openings that utilize slot configurations next to the hinge and in the interior of the planar surface.

[0032] FIGS. 10(a) and (b) illustrate extensions of the belly flaps used to control the air flow under and around the flap. This embodiment may be employed near the landing gear (above) or removed from the landing gear (below).

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0033] FlG. 1 is a side view of a blended wing body aircraft with an extended belly flap having substantially no sweep. FIG. 2 is a front view of the blended wing body aircraft shown in FIG. 1. FIG. 3 is a top view of a blended wing body aircraft with belly flaps, but with a sweep angle, θ added to the belly flaps.

LAS99 1465064-1.028080.0213 - 4 - [0034] As shown in FIGS. 1-3, a blended wing body aircraft 101 may include a wing that is configured to house one or more persons, payload, and/or cargo within the interior of the wing. The aircraft may have no tail and may be powered by one or more propellers, jets, rockets, and/or by any other means. The aircraft may instead be without a means of propulsion.

[0035] The actual shape and configuration of the blended wing body aircraft may vary widely. The aircraft shown in FIGS. 1-3 is just an example.

[0036] One or more surface structures may extend downwardly from an underside surface 109 of the wing. Each surface structure may be substantially planar. Flaps, such as flaps 103, 105, and 107, are examples. Each of the flaps 103, 105, and 107 may cooperate when extended downwardly to form a substantially continuous or discontinuous surface. The center line of the continuous or discontinuous surface may substantially coincide with the center line of the aircraft.

[0037] Each of the flaps 103, 105, and 107 may vary widely in their configuration and orientation. Examples will now be discussed.

[0Q38] In some embodiments, each flap may be at a sweep angle θ with respect to the perpendicular to the centerline of the aircraft (see FIG. 3) that is between - 70° and 70°. In other embodiments, the sweep angle θ may fall within a narrower range, namely between -10° and the sweep angle Λ of the wing (see FIG. 3).

[0039] When deployed, substantially each point on each flap may be behind a leading edge of the wing by at least 5% of the length of the chord of the wing that passes through the point. Similarly, substantially each point on each flap may be in front of a trailing edge of the wing by at least 5% of the length of this chord. One such point is shown in FIG. 3. It is on the flap 103 and is labeled as a flap point 111. The chord of the wing that passes through the flap point 111 is shown in FIG. 3 as extending between a leading point 113 on the leading edge of the wing and a trailing point 115 on the trailing edge of the wing. Thus, the distance 112 between the leading point 113 and the flap point 111 and the distance 114 between the flap point 111 and the trailing point 115 may both be greater than 5% of the distance between the leading point 113 and the trailing point 115.

[0040] In other embodiments, the range of positioning may be narrower. Specifically, substantially every one of the points on the planar structure may be

LAS99 1465064-1.028080.0213 - 5 - located behind a leading edge of the wing by at least 20% of the length of the chord of the wing that passes through the point, and in front of the trailing edge of the wing by at least 35% of the length of this chord. In these embodiments, for example, the distance 112 between the leading point 113 and the flap point 111 may be at least 20% of the distance between the leading point 113 and the trailing point 115, and the distance 114 between the flap point 111 and the trailing point 115 may be at least 35% of the distance between the leading point 113 and the trailing point 115.

[0041] The deployment angle δ at which each planar structure is deployed (see FIGS. 1 and 9) may be between 10 and 170°. In other embodiments, the deployment angle may be within a narrower range, such as between 40 and 95°.

[0042] FIG. 4 is a side view of the blended wing body aircraft shown in FIG. 1 with the belly flaps 103, 105, and 107 retracted. In this embodiment, the belly flaps 103, 105, and 107 may be retracted so as to cause their exterior surfaces to be substantially flush with the underside surface 109 of the wing. Retractions to other positions relative to the underside surface 109 may be done instead.

[0043] The width of each flap may vary. In one embodiment, the combined width of the flaps may span between 10 and 100 percent of the span of the wing. When the retracted position covers or causes the flap to be within a landing gear well (as discussed below), the combined width of the flaps may span between 2 and 20 percent of the span of the wing.

[0044] When deployed in its extended position, each flap may cause an increase in the static pressure ahead of the hinge line 123 of the flap and a decrease in that static air pressure aft of the hinge line 123 of the flap during forward movement of the aircraft, as compared to when the flap is in a retracted position that is substantially flush with the underside surface 109 of the wing. This may produce a nose-up pitching moment about the center of gravity 121 of the aircraft.

[0045] When deployed in their extended position, the collective effect of the flaps (or of just one flap if only one flap is used) may be to increase the control pitching moment of the aircraft by at least 5% as compared to the control pitching moment of the aircraft when the flaps are retracted substantially flush with the underside surface 109 of the wing.

LAS99 1465064-1.028080.0213 - 6 - [0046] FIG. 5 illustrates a belly flap in a retracted position covering a landing gear well. As shown in FIG. 5, a belly flap 501 may be in a retracted position that is substantially flush with an underside surface 503 of an aircraft. While in this retracted position, the belly flap 501 may substantially cover a landing gear well 505.

[0047] Within the landing gear well 505, there may be an actuator 507, at least one wheel 509, and various linkages, such as linkages 513, 515, and 517, that link the flap 501 and the wheel 509 with the actuator 507 and one or more wing anchors, such as wing anchors 519 and 521.

[0048] FIG. 5(b) illustrates the belly flap of FIG. 5(a) in a position extended from the landing gear well. As shown in FIG. 5(b), the belly flap 501 has been deployed in this extended position, along with the wheel 509.

[0049] Any type of actuator may be used for the actuator 507. For example, the actuator 507 may be a hydraulically-driven piston. In addition or instead, the actuator 507 may be electrically-driven, using, for example, an electric motor and ball screw arrangement. A hydraulic motor may be used in addition or instead. One or more locking mechanisms (not shown) may be added to lock the belly flap 501 into its deployed position, that is, the position shown in FIG. 5(b).

[0050] The belly flap 501 need not be used as a cover for the landing gear well 505 while in its retracted position, as shown in FIG. 5(a). Instead, the belly flap 501 may be retracted within the landing gear well 505. In this embodiment, differently-configured linkages may be used to move the belly flap 501 between its deployed position as shown in FIG. 5(b) and retracted position within the landing gear well. In this embodiment, a different structure may be used to cover the landing gear well while the wheel 509 and the belly flap 501 are in their retracted position.

[0051] One or more of the actuators and associated linkages that are shown in FIGS. 5 (a) and (b) and/or discussed above in connection with these figures may be used in connection with each of the belly flaps 103, 105, and 107 shown in FIGS. 1-4, or some or all of these belly flaps may use a different type of actuator and/or linkage.

[0052] FIGS. 6(a)-(d) illustrate variations in the shapes of belly flaps. A substantially rectangular shape is illustrated in FIG. 6(a), trapezoidal shapes are

LAS99 1465064-1.028080.Q213 - 7 - illustrated in FIGS. 6(b) and (c), while a curved lower edge is illustrated in FIG. 6(d). The belly flap(s) may have a different shape from any of those illustrated in FIG. 6. The shape may depend upon performance criteria that are desired from the belly flap and/or other criteria concerning the aircraft.

[0053] FIGS. 7(a)-(d) illustrate various patterns of porous openings in belly flaps. As shown in these figures, a belly flap may include one or more porous openings at one or more locations. Whether the belly flap has any openings, the number of openings, the shape of the openings, and the position of the openings may again be dictated by performance criteria that is desired from the belly flap and/or other criteria concerning the aircraft.

[0054] FIGS. 8(a)-(d) illustrate variations in the lower edges on belly flaps. A serrated edge is illustrated in FIG. 8(a), a lower edge that is narrower than an upper edge is illustrated in FIG. 8(b), an edge with scallops is illustrated in FIG. 8(d), and an edge that includes angled serrations and scallops is illustrated in FIG. 8(c). The lower edges and side edges of the belly flaps may be similar to or different from any of those shown in FIG. 8. The lower edges and side edges may similarly be configured to achieve desired performance criteria and/or to meet other criteria of the aircraft.

[0055] FIGS. 9(a)-(b) illustrate particular types of porous belly flaps 905 and 906 that utilize a slot type opening. In this embodiment, the belly flap 905 may be attached via a hinge 911 to the underside surface of the wing 909. The belly flap 906 may similarly be attached. This may leave a slot 913 between the upper extremity of the belly flap and the wing's surface. The belly flap 906 may leave multiple slots. A slot 915 may be included in the interior of the belly flap, such as in the belly flap 906.

[0056] FIGS. 10(a) and (b) illustrate extensions of the belly flaps used to control the air flow under and around the flap. This embodiment may be employed near the landing gear (above) or removed from the landing gear (below). They illustrate that, although the belly flaps may be primarily planar, extensions may be added to their extremities to control the air flow around the flaps. Specifically, they illustrate belly flaps 1001 and 1003 that may have an extension 1005 and 1007, respectively, under a belly 1009 and 1011 , respectively of a wing 1013 and 1015,

LAS99 1465064-1.028080.0213 - 8 - respectively. They also illustrate air flows 1017 and 1019, respectively, that may result.

[0057] The belly flaps may be extended and retracted at any time during the use or maintenance of the aircraft. For example, the belly flaps may be extended and thus deployed during takeoff and/or landing, and retracted while the plane is in flight and, if not blocked by extended wheels, while taxiing on the runway and/or at rest on the ground.

[0058] The components, steps, features, objects, benefits and advantages that have been discussed are merely illustrative. None of them, nor the discussions relating to them, are intended to limit the scope of protection in any way. Numerous other embodiments are also contemplated, including embodiments that have fewer, additional, and/or different components, steps, features, objects, benefits and advantages. The components and steps may also be arranged and ordered differently. In short, the scope of protection is limited solely by the claims that now follow. That scope is intended to be as broad as is reasonably consistent with the language that is used in the claims and to encompass all structural and functional equivalents.

[0059] For example, although having thus-far been described in connection with aircraft having a blended wing body, the surface structures, such as the belly flaps that have been described, may be used in connection with conventional aircraft, that is, aircraft that may be configured to contain persons, payloads, and/or cargo within a central fuselage, and that may have a tail. When used with conventional aircraft, the belly flaps may still extend downwardly from an underside surface of the wing and may conform to one or more of the other criteria that have been described above in connection with aircraft having a blended wing body.

[0060] Although belly flaps have thus-far been illustrated in the drawings, other types of surface structures may be used instead. Further, the number of planar structures may be different than the three that have been illustrated. For example, a single surface may span both sides of the wing; one surface may instead be used under each side of the wing; and even multiple surfaces may instead be used under each side of the wing. Also, all of the surfaces need not be co-Sinear, particularly when they are at a sweep angle with respect to the aircraft. Even

LAS991465064-1.Q28080.Q213 - 9 - when using multiple surfaces on the same side of a wing, the multiple surfaces need not be co-linear.

[0061] Further, the downwardly extending surface structures that have been discussed, such as the belly flaps, may have shapes other than substantially planar. For example, one or more of these surface structures may have a curved surface that is convex or concave relative to the direction of the wind. A cross- section similar to the cross-section of a half pie is an example.

[0062] The phrase "means for" when used in a claim embraces the corresponding structure and materials that have been described and their equivalents. Similarly, the phrase "step for" when used in a claim embraces the corresponding acts that have been described and their equivalents. The absence of these phrases means that the claim is not limited to any corresponding structures, materials, or acts.

[0063] Nothing that has been stated or illustrated is intended to cause a dedication of any component, step, feature, object, benefit, advantage, or equivalent to the public, regardless of whether it is recited in the claims.

LAS99 1465064-1.028Q80.0213 - 10 -

Claims

WE CLAIM:

1. A blended wing body aircraft comprising: a blended wing configured to house a person, payload and/or cargo within the wing; a surface structure; and an actuator configured to controllably cause the planar structure to extend downwardly from an underside surface of the wing oriented such that: the planar structure forms a sweep angle measured from the perpendicular to the centerline of the aircraft between -70 and 70 degrees; and substantially each point on the planar structure is behind a leading edge of the wing and sn front of a trailing edge of the wing by at least 5% of the length of the chord of the wing that passes through the point.

2. The blended wing body aircraft of claim 1 comprising one or more additional surface structures, each associated with an actuator that is configured to controllably cause the additional planar structure to extend downwardly from the underside surface of the wing.

3. The blended wing body aircraft of claim 2 wherein all of the planar structures form a substantially continuous or discontinuous surface that has a centerline that substantially coincides with the centerline of the aircraft.

4. The blended wing body aircraft of claim 2 wherein all of the planar structures collectively span between 10 and 100 percent of the span of the wing.

5. The blended wing body aircraft of claim 1 wherein the actuator is configured to controllably cause the planar structure to form a deployment angle with a trailing portion of the underside surface of the wing that is between 10 and 170 degrees.

6. The blended wing body aircraft of claim 5 wherein the actuator is configured to controllably cause the planar structure to form a deployment angle

LAS99 1465064-1.028030.0213 - 1 1 - with a trailing portion of the underside surface of the wing that is between 40 and 95 degrees.

7. The blended wing body aircraft of claim 1 wherein the sweep angle of the planar structure is between -10 degrees and the sweep angle of the wing.

8. The blended wing body aircraft of claim 1 wherein substantially every one of the points on the planar structure is located behind the leading edge of the wing by at least 20% and in front of the trailing edge of the wing by at least 35% of the length of the chord of the wing that passes through the point.

9. The blended wing body aircraft of claim 1 wherein the actuator is configured to controllably retract the planar structure from its downwardly extending position until the planar structure is substantially flush with the underside surface of the wing.

10. The blended wing body aircraft of claim 1 wherein the wing includes a landing gear well and the actuator is configured to retract the planar structure into a position covering or within the landing gear well.

11. The blended wing body aircraft of claim 1 wherein the planar structure has a substantially rectangular shape.

12. The blended wing body aircraft of claim 1 wherein the planar structure has a substantially trapezoidal shape.

13. The blended wing body aircraft of claim 1 wherein the planar structure has a plurality of openings there through.

14.. The blended wing body aircraft of claim 1 wherein the planar structure has a lower edge and/or side edges that are curved.

15. The blended wing body aircraft of claim 1 wherein the planar structure has a lower edge and/or side edges that are serrated.

16. The blended wing body aircraft of claim 1 wherein the surface structure is substantially planar.

17. A blended wing body aircraft comprising: a blended wing configured to house a person, payload and/or cargo within the wing;

LAS99 1465064-1.02808Q.0213 - 12 - a surface structure; and an actuator configured to controllably cause the planar structure to extend downwardly from an underside surface of the wing from a hinge line with an orientation that causes an increase in static pressure ahead of the hinge line of the structure and a decrease aft of the planar structure during forward movement of the aircraft, as compared to when the planar structure is not extended, thereby producing a nose-up pitching moment.

18. The blended wing body aircraft of claim 17 wherein the actuator is configured to controllably cause the planar structure to form a deployment angle with a trailing portion of the underside surface of the wing that is between 10 and 170 degrees,

19. The blended wing body aircraft of claim 18 wherein the actuator is configured to controllably cause the planar structure to form a deployment angle with a trailing edge of between 40 and 95 degrees.

20. The blended wing body aircraft of claim 17 wherein the sweep angle of the planar structure is between -70 and +70 degrees

21. The blended wing body aircraft of claim 20 wherein the sweep angle of the planar structure is between -10 degrees and the sweep angle of the wing.

22. The blended wing body aircraft of claim 17 wherein substantially every one of the points on the planar structure is located behind the leading edge of the wing by at least 20% and in front of the trailing edge of the wing by at least 35% of the length of the chord of the wing that passes through the point.

23. The blended wing body aircraft of claim 17 wherein the wing includes a landing gear well and the actuator is configured to retract the planar structure into a position covering or within the landing gear well.

24. The blended wing body aircraft of claim 17 wherein the planar structure has a plurality of openings there through.

25. The blended wing body aircraft of claim 17 wherein the planar structure has a lower and/or side edges that are serrated.

LAS99 1465064-1.028080.0213 - 13 -

26. The blended wing body aircraft of claim 17 wherein the surface structure is substantially planar.

27. A blended wing body aircraft comprising: a blended wing configured to house a person, payload and/or cargo within the wing; one or more surface structures; and one or more actuators configured to controllably cause the planar structures to extend from an underside surface of the wing so as to increase the aircraft's control pitching moment by more than 5 percent as compared to when the planar structures are not extended.

28. The blended wing body aircraft of claim 27 wherein the actuators are configured to controlϊably cause the planar structures to form a deployment angle with a trailing portion of the underside surface of the wing that is between 10 and 170 degrees

29. The blended wing body aircraft of claim 28 wherein the actuators are configured to controllably cause the planar structures to form a deployment angle with a trailing portion of the underside surface of the wing that is between 40 and 95 degrees.

30. The blended wing body aircraft of claim 27 wherein the sweep angle of each planar structure is between -70 and +70 degrees

31. The blended wing body aircraft of claim 30 wherein the sweep angle of each planar structure is between -10 degrees and the sweep angle of the wing.

32. The blended wing body aircraft of claim 27 wherein substantially every one of the points on the planar structure is located behind the leading edge of the wing by at least 20% and in front of the trailing edge of the wing by at least 35% of the length of the chord of the wing that passes through the point.

33. The blended wing body aircraft of claim 27 wherein the wing includes a landing gear well and the actuators are configured to retract one of the planar structures into a position covering or within the landing gear well.

LAS99 1465064-1.028080.0213 - 14 -

34. The blended wing body aircraft of claim 27 wherein at least one of the planar structures has a plurality of openings there through.

35. The blended wing body aircraft of claim 27 wherein at least one of the planar structures has a lower and/or side edges that are serrated.

36. The blended wing body aircraft of claim 27 wherein each surface structure is substantially planar.

37. An aircraft comprising: a wing having a landing gear well; a surface structure; and an actuator configured to controllably extend the planar structure from a position covering or within the landing gear well to a position that causes the planar structure to extend downwardly from an underside surface of the wing such that: the planar structure forms sweep angle with the aircraft between 70 and +70 degrees; and substantially each point on the planar structure is behind a leading edge of the wing and in front of a trailing edge of the wing by at least 5% of the length of a chord of the wing that passes through the point.

38. The blended wing body aircraft of claim 37 wherein the actuator is configured to controllably cause the planar structure to form a deployment angle with a trailing portion of the underside surface of the wing that is between 10 and 170 degrees.

39. The blended wing body aircraft of claim 37 wherein the sweep angle of the planar structure is between -5 degrees and the sweep angle of the wing.

40. The blended wing body aircraft of claim 37 wherein substantially every one of the points on the planar structure is located behind the leading edge of the wing by at least 20% and in front of the trailing edge of the wing by at least 35% of the length of the chord of the wing that passes through the point.

LAS99 1465064-1.028080.0213 - 15 -

41. The blended wing body aircraft of claim 37 wherein the planar structure spans in front of the wheel well and underside a half of the wing between 2 and 20 percent of the span of the half of the wing.

42. A process for taking off or landing an aircraft having a wing and a surface structure, comprising in the order recited: extending the planar structure downwardly from an underside surface of the wing so that: the planar structure forms a sweep angle with the aircraft between 70 and +70 degrees; and substantially each point on the planar structure is behind a leading edge of the wing and in front of a trailing edge of the wing by at least 5% of the length of a chord of the wing that passes through the point; and taking off or landing the aircraft.

43. The process of claim 42 wherein the process is performed both during take off and landing.

44. The process of claim 42 wherein the process is performed during take off and further comprising retracting the planer structure after takeoff.

45. The process of claim 42 wherein the process is performed during landing and further comprising retracting the planer structure after landing.

46. A blended wing body aircraft comprising: a blended wing configured to house a person, payload and/or cargo within the wing; one or more surface structures; and one or more actuators configured to controllably cause the planar structures to extend from an underside surface of the wing so as to increase the aircraft's lift coefficient by more than 5 percent as compared to when the planar structures are not extended.

47. The blended wing body aircraft of claim 46 wherein the actuators are configured to controllably cause the planar structures to form a deployment angle

LAS99 1465064-1.028080.0213 - 16 - with a trailing portion of the underside surface of the wing that is between 10 and 170 degrees.

48. The blended wing body aircraft of claim 46 wherein the sweep angle of each planar structure is between 70 and +70 degrees.

49. The blended wing body aircraft of claim 46 wherein substantially every one of the points on the planar structure is located behind the leading edge of the wing by at least 20% and in front of the trailing edge of the wing by at least 35% of the length of the chord of the wing that passes through the point.

50. The blended wing body aircraft of claim 46 wherein the wing includes a landing gear well and the actuators are configured to retract one of the planar structures into a position covering or within the landing gear well.

51. The blended wing body aircraft of claim 46 wherein at least one of the planar structures has a plurality of openings there through.

52. The blended wing body aircraft of claim 46 wherein at lease one of the planar structures has a lower and/or side edges that are serrated.

53. The blended wing body aircraft of claim 46 wherein each surface structure is substantially planar.

LAS99 1465064-1.028080.0213 - 17 -