Trip device for enhancing aircraft performance and handling

Abstract

To provide a method of enhancing operation of an aircraft and a method of manufacturing a wing that are capable of improving aerodynamic efficiency by maintaining a laminar flow under cruise conditions while handling worst-case conditions without increasing a weight of the wing.SOLUTION: Low-drag design conditions for minimizing drag are identified for an airplane where a laminar flow 302 is targeted. Transition positions for a laminar flow 302 to a turbulent flow 306 are predicted for each design condition. The most downstream transition position is determined therefrom. A manufacturing method is determined to dispose a trip device 108 immediately after the most downstream position.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] 1. Field The present disclosure relates generally to aircraft wing efficiency and, more particularly, to a fixed position trip device along the span of a wing that controls laminar and turbulent boundary layer flows.

[0002] Embodiments are defined in the independent claims. Optional features of the embodiments are defined in the dependent claims.

[0003] 2. Description of Related Art Commercial transport aircraft manufacturers are under constant pressure to increase the operating efficiency of passenger and cargo aircraft. A major component of operating costs is fuel, and the two main factors that contribute to an aircraft's fuel efficiency are aerodynamic drag and aircraft weight. Manufacturers have sought techniques and devices to reduce drag without increasing weight while maintaining critical loads. [Background technology]

[0004] One technique is to maintain a laminar boundary layer flow over the wing, which reduces drag. Laminar flow control over an aerodynamic surface reduces drag and improves fuel efficiency by delaying the transition to turbulence in the boundary layer over that surface. This transition can be delayed by contouring the aerodynamic surface to promote laminar flow. During wing design, changes that increase the extent of laminar flow are balanced against increases in other factors that lead to performance shortfalls, such as aerodynamic shock strength and aircraft / wing weight. One design factor is to ensure that the increased extent of laminar flow eliminates the need to strengthen the wing to accommodate extreme load conditions, resulting in increased wing weight.

[0005] The extent of laminar flow is balanced against the possible excess loads on the wing in extreme load conditions, or more broadly, non-cruise conditions. The possible excess loads on the wing, which are taken into account when designing the wing, require the wing to be able to withstand extreme or worst case conditions. In other words, the wing must be strong enough to handle the extreme load conditions. Strengthening or reinforcing the wing adds weight to the aircraft, which can quickly negate any benefits gained by reducing drag from laminar flow.

[0006] There is therefore a need to improve aerodynamic efficiency by accommodating worst case conditions without increasing the weight of the wing while maintaining laminar flow at cruise conditions. Also, it must be possible to gather more accurate load, control efficiency, and handling quality data during ground-based wind tunnel testing of laminar flow wings. This data can be used for aircraft design prior to in-flight testing of the aircraft. Summary of the Invention

[0007] One disclosed embodiment is a method of operating an aircraft with a wing having a trip device at a fixed location along the span of the wing. When the aircraft is in flight, the wing moves through a transonic airflow as air passes over the wing surface creating a laminar boundary layer. When the airflow is downstream of the trip device, a turbulent boundary layer is created. The laminar boundary layer in front of the trip device extends for a particular length and the turbulent boundary layer extends for another particular length. The trip device is at a trip location aft of the laminar boundary layer, such trip location allows laminar flow over the length of the laminar boundary layer to increase aerodynamic efficiency and allows turbulent flow to flow over the length of the turbulent boundary layer, thereby reducing loading on the wing and providing a fixed aft limit to the transition from the laminar boundary layer to the turbulent boundary layer.

[0008] Another disclosed embodiment is a method of manufacturing a wing having a trip device. A target transition location that occurs naturally under normal cruise conditions is identified along the chord of an airfoil surface. A plurality of target transition locations are predicted under various design conditions. A most aft or downstream target transition location is identified from the plurality of target transition locations. Thus, shock generation on the wing is downstream of the identified most downstream target transition location along the chord of the airfoil. A trip device is installed along the span of the wing a selected length aft of the most downstream target transition location.

[0009] Another disclosed embodiment is an aircraft wing having a trip device along the span of the wing, the device being located a selected length aft of a target transition location along the chord of the wing airfoil, the trip device preventing downstream movement of the laminar to turbulent transition and associated movement of the shock location on the wing, the trip device location on the wing airfoil varying along the span of the wing.

[0010] Illustrative, non-limiting examples of novel features according to the present disclosure are described in the following clauses.

[0011] A1. A method 500 for operating an aircraft 100, comprising: moving a wing 102 having a trip device 108 at a fixed position along the span of the wing 102 through an airflow such that air passing over the wing surface creates a laminar boundary layer 302; generating a turbulent boundary layer 308 when the airflow is downstream of the fixed position trip device 108; wherein the laminar boundary layer 302 extends a first length and the turbulent boundary layer extends a second length, and the fixed position trip device 108 is at the trip device that is aft of the laminar boundary layer such that the trip device position allows for a first length of laminar flow that increases aerodynamic efficiency and a second length of turbulent flow that reduces loading on the wing 102, thereby providing a fixed aft limit to the transition from the laminar boundary layer 302 to the turbulent boundary layer 308.

[0012] A2. The method 500 of clause A1, wherein the trip device position is aft of the target transfer position 106.

[0013] A3. The method 500 of clause A1, wherein the trip device position is at the target transfer position 106.

[0014] A4. The method 500 of clause A1, wherein the trip device location is upstream of the target transfer location 106.

[0015] A5. Reducing shock motion on a wing 102, A fixed-position trip device 108 reduces downstream movement of the transition and associated movement of the shock location on the wing 102 during transonic airflow to reduce shock motion. The method 500, 508 of clause A1 further includes:

[0016] A6. The method 500 of clause A1, wherein the trip device position reduces aerodynamic force variations for one of the particular flight parameters and conditions.

[0017] A7. The method 500 of clause A1, wherein the fixed position trip device 108 is a continuous trip strip along the span of the wing 102.

[0018] A8. The method 500 of clause A1, wherein the fixed position trip device 108 is a plurality of separate elements along the span of the wing 102.

[0019] A9. The method 500 of clause A1, wherein a dimension of the trip device varies along the span of the wing 102.

[0020] A10. The method 500 of clause A1, wherein the trip device position on the airfoil 104 of the wing 102 varies along the span of the wing 102.

[0021] A11. The method 500 of clause A1, wherein the fixed position trip device 108 is along an upper surface of the wing 102.

[0022] A12. The method 500 of clause A11, wherein the fixed position trip device 108 is along either side of the vertical wing surface.

[0023] A13. A method 400 for manufacturing a wing 102, comprising: The method includes identifying a first target transition location along a chord of an airfoil 104 surface under cruise conditions; predicting a plurality of target transition locations under a plurality of design conditions 404; identifying a most downstream target transition location 106 from the plurality of target transition locations such that shock onset 110 is downstream of the identified most downstream target transition location 106 along the chord of the airfoil 104 surface; and incorporating a trip device 108 a selected length along the span of the wing 102 aft of the most downstream target transition location 106.

[0024] A14. The method 400 of clause A13, wherein the trip device position reduces aerodynamic force variations between flight conditions.

[0025] A15. The method 400 of clause A13, wherein the trip device 108 is a continuous trip strip.

[0026] A16. The method 400 of clause A13, wherein the trip device 108 is a plurality of separate elements.

[0027] A17. The method 400 of clause A13, wherein the size of the trip device 108 and the trip device position vary along the span of the wing 102.

[0028] A18. A wing 102 of an aircraft 100 with a trip device 108 along the span of the wing 102, A wing 102 of an aircraft 100, where the trip device location is aft of a target transition location 106 along the chord of an airfoil 104 of the wing 102, a trip device 108 prevents downstream movement of the laminar to turbulent transition and associated movement of the shock location on the wing 102, and the trip device location on the wing airfoil 104 varies along the span of the wing 102.

[0029] A19. The wing 102 of the aircraft 100 of clause A18, wherein the trip device (108) is a continuous trip strip along the span of the wing 102.

[0030] A20. The wing 102 of the aircraft 100 of clause A18, wherein the trip device 108 is a plurality of separate elements along the span of the wing 102.

[0031] A21. The wing 102 of the aircraft 100 of clause A18, wherein a trip device position on an airfoil 104 of the wing 102 varies along the span of the wing 102. [Brief description of the drawings]

[0032] [Figure 1] 1A and 1B are diagrams illustrating an aircraft, an aircraft wing, and an airfoil with a trip device, according to one embodiment. [Diagram 2] FIG. 1 is a perspective view of an aircraft showing trip devices on both wings, according to one embodiment. [Diagram 3] 1 illustrates an airfoil or wing section according to one embodiment, showing laminar and turbulent boundary layers. [Figure 4] FIG. 1 is a flow diagram illustrating a process for determining the best location for a trip and for collecting test data, according to one embodiment. [Diagram 5] FIG. 1 is a flow diagram illustrating a process for operating an aircraft having a wing with a trip device located on the upper surface of the wing, according to one embodiment. [Figure 6] FIG. 1 illustrates a flow diagram of an aircraft production and service method according to an embodiment. [Figure 7] FIG. 2 is a block diagram illustrating aircraft wing components according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] In the following description, numerous specific details are set forth to provide a thorough understanding of the presented concepts. The presented concepts may be practiced without some of these specific details. In other instances, well-known process steps are not described in detail so as not to unnecessarily obscure the described concepts. While some concepts are described in conjunction with specific examples, it should be understood that these examples are not intended to be limiting. It is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the claims.

[0034] Various drawings describe methods and systems for operating an aircraft having a wing with fixed-position trip gear. The drawings also describe methods for determining where the trip gear should be located along the span of the wing. Limiting the potential for increased loading and flight performance uncertainties associated with laminar flow wings is also described.

[0035] In one embodiment, it is preferred that the shock location or position on the wing coincides with the location for a typical wing that does not include a trip device and where the majority of the wing has a turbulent boundary layer under excessive load conditions.

[0036] There are secondary problems with extending the laminar flow region within the boundary layer; it is preferable to place the trip device at a fixed location along the chord of the wing to set a downstream limit for the extent of laminar flow. In one embodiment, the downstream limit of transition is defined as a function of spanwise position on the wing; that is, the chord position of the trip device can vary as the trip extends along the span of the wing. In addition to limiting the load increases that may result from extending laminar flow, this provides a known limit for extreme loading conditions that dictate the aircraft design configuration or critical operating conditions.

[0037] In one embodiment, advantageous specific flight parameters or design conditions are determined. These may include Mach number, altitude, weight, and other conditions. These are referred to as low-drag design conditions where drag is nominally minimized during cruise. For each low-drag design condition identified, expected transition positions are predicted under these conditions.

[0038] For each low drag design condition, there is one transition line along the span of the wing. The position that is furthest downstream along the chord of the wing considering the design condition is the target transition point. Immediately aft of the target transition point is the trip gear location. This provides a fixed aft limit for the transition position.

[0039] When there is a break in pressure, the shock line is lower upstream and higher downstream. The further downstream of the shock line, the greater the area of ​​low pressure on the wing, the greater the lift or load on the wing. A shock is a significant increase in pressure and is very sudden.

[0040] In one embodiment, the trip location or transition point is determined by considering the load, and specifically the location or position of the shock. The purpose is to control aerodynamic forces in extreme load conditions. In such conditions, the laminar boundary layer can adversely affect the shock location or position, and therefore limiting the laminar boundary layer will help limit the load in such cases.

[0041] In one embodiment, determining the trip device locations can make wind tunnel testing more systematic and deterministic to predict the control effects and handling qualities of an airplane. Ground collected data on aerodynamic control effects, loads, etc. become more reliable predictors of these quantities in flight when the determined trips reduce variability. Because the wing is designed to withstand high loads, the reduced uncertainty in testing with known transition locations or specific trip locations can increase confidence in predicting the structural response of laminar wing prior to building and testing the aircraft. In one embodiment, the trips limit the movement of the shock or shock line due to laminar flow, thereby limiting the amount of load on the wing.

[0042] As mentioned above, laminar flow control on an aerodynamic surface reduces drag and improves fuel efficiency by delaying the transition to turbulence in the boundary layer over that surface. During design, changes that increase the extent of laminar flow are made to balance the potential increase in other factors that contribute to drag. For maneuvering conditions away from the target cruise conditions, the transition can be expected to move forward or aft depending on the specific flow conditions (e.g. altitude, Mach number, weight...). In general, the further downstream the transition occurs (i.e. the larger the chord position), the greater the benefit of laminar flow.

[0043] FIG. 1A is a perspective view of an aircraft 100 showing a wing 102 and a cross section of the wing 102 or airfoil shown in FIG. 1B. FIG. 1B is an airfoil 104 of the wing 102 according to one embodiment. There is a target transition point 106 on the upper surface of the airfoil 104. The target transition point 106 may be on the lower surface of the airfoil 104. This is a point on the airfoil 104 where it has been determined that laminar flow is predicted to transition to turbulent flow in order to achieve a favorable balance between the aerodynamic efficiency of the wing (e.g., reducing drag) and the ability to adequately handle extreme loading conditions (without having to increase the weight of the wing). A process for determining the location of such a target transition point 106 is shown in FIG. 4.

[0044] The target transition point 106 is immediately followed by the trip 108. The distance between the target transition point 106 and the trip 108 can vary but is typically short. One factor in determining the predicted or expected location of the target transition point 106 and therefore the position of the trip 108 is the shock line location 110. The shock line location 110 significantly influences or determines whether the wing 102 can meet the requirements for handling extreme loading conditions. As described in more detail above, as a general principle, the further aft the shock line location 110 is, the greater the low pressure area on the upper surface of the wing, which typically stresses the wing during extreme loading conditions (e.g., a tight turn or recovery from a sudden drop in altitude where there is extremely low pressure on the upper surface of the wing).

[0045] 2 is a perspective view of the aircraft 100 showing the trip gear 108 on each wing, according to one embodiment. The trip gear 108, shown in dashed lines, extends the wing span on each wing from the body or fuselage to the tip of the wing. As noted above, the position of the trip 108 may vary on each airfoil of the wing; that is, the amount of surface area forward or aft of the trip 108 may differ along the span of the wing.

[0046] 3 illustrates an airfoil or wing cross section 104 according to one embodiment, showing laminar and turbulent boundary layers. The boundary layers, trip device dimensions, and airfoil cross section dimensions are not to scale and have been exaggerated for ease of illustration.

[0047] Shown is an airfoil or wing section 104 and a cross section of a trip device 108. The front of the airfoil section 104 is on the left. This is where the air first hits the wing with laminar flow control. A laminar boundary layer 302 forms from the front of the wing up to the trip 108 position. Just after the trip 108 position, the airflow transitions to a turbulent boundary layer 306. Without the trip device, the airflow would naturally transition to a turbulent boundary layer position 304 further downstream at various extreme load conditions. Three possible turbulent boundary layer transitions are shown in FIG. 3. Various possible shock locations are not shown in FIG. 3. Typically, the trip device causes the shock line to be further upstream on the wing than it would be without the trip device.

[0048] FIG. 4 is a process flow diagram illustrating a method for determining the best anticipated location for the trip unit and for collecting test data, according to one embodiment. In step 402, low-drag design conditions for minimizing drag are identified for an aircraft targeting laminar flow. These conditions are identified for low-drag conditions during cruise. Examples include Mach number, altitude, weight, and other conditions. In step 404, a laminar to turbulent transition position is predicted for each design condition. This will result in two or more locations along the chordwise length of the airfoil where the airflow will naturally transition from laminar to turbulent. In step 406, the system identifies or determines the most downstream envelope transition position along the span of the airfoil, taking into account the low-drag design conditions. As shown in FIG. 2, a design condition is determined that produces a most downstream path similar to the trip unit path similar to the continuous or dashed line 108 of the trip unit in FIG. 2.

[0049] In step 408, the trip device is installed on the wing, where the trip device (whether a separate element or a continuous trip strip or edge, alone or with a vortex generator or other means) is immediately after the most downstream position determined in step 406. The distance between the most downstream position in step 406 and the trip device path can be determined using conventional means. As noted above, the position (or transition position) of the trip device on the chordwise length of the airfoil from the wing can be varied for each airfoil making up the wing. That is, the ratio of the downstream length (after the trip device) to the upstream length of the chord can be varied for each airfoil, resulting in a path similar to the trip 108 of FIG. 2.

[0050] In step 410, the system collects wind tunnel and other computational data of the wing with the trip gear in the best expected or predicted position determined in step 408. Using this data, it can be determined whether the trip gear is best positioned in terms of critical or extreme load conditions. Adjustments to the trip positions can be made as appropriate to fine-tune to address critical load conditions and aerodynamic efficiency prior to actual flight testing.

[0051] It would be preferable to be able to predict flight test loads (section lift) a priori with high fidelity. In one embodiment, the loads are determined on the wing with existing trip devices at their best guess locations as determined by the process described in Figure 4. By better knowing where to place the trip devices, it is possible to limit the variability of aircraft control effectiveness and maneuverability.

[0052] FIG. 5 is a flow diagram of a process for piloting an aircraft having a wing with a trip device located on the upper surface of the wing according to the process described in FIG. 4, according to one embodiment. In step 502, the aircraft is in flight and its wing is moving through the air. Specifically, the wing is moving through a transonic airflow. In step 504, the movement of the wing through the air creates a laminar boundary layer on the upper surface or lower front of the wing, which starts at the leading edge of the wing. In another embodiment, the laminar boundary layer is along a vertical surface. In step 506, the laminar flow transitions to a turbulent boundary layer as a result of the trip device on the surface of the wing. In the chord of the wing, the length of the laminar boundary layer is a first length and the length of the turbulent boundary layer is a second length. The total chord length of the airfoil is the sum of the first length and the second length. In step 508, a shock is generated on the wing. This shock has less movement as flight conditions change than would have occurred if the trip device had not been installed on the wing in a position determined via the process described in Figure 4. As discussed above, the shock line is in a position on the wing that reduces the amount of low pressure on the upper surface of the wing (i.e., expands the amount of high pressure area on the upper surface). This reduces the loads on the wing in extreme conditions. Similar features apply to the lower surface of the wing or the vertical sides of the wing.

[0053] As mentioned above, the fixed position trip gear 108 disclosed herein is used on the wings of the aircraft 100. The manufacture of such equipment may therefore be described in the context of an aircraft manufacturing and service method 600 as shown in FIG. 6 and the aircraft 100 shown. During the pre-production phase, the method 600 may include specification and design 604 of the aircraft 100 and procurement 606 of materials. During the production phase, a manufacturing phase 608 of components and subassemblies of the aircraft 100 and a system integration phase 610 take place. The aircraft 100 then proceeds through certification and delivery 612 and into service 614. While in service with a customer, the aircraft 602 is scheduled for routine maintenance and service 616, which may include modifications, reconfigurations, refurbishments, etc.

[0054] Each of the processes of method 600 may be performed or carried out by a system integrator, a third party, and / or an operator (e.g., a customer). For purposes of this specification, a system integrator may include, but is not limited to, any number of aircraft manufacturers and major system subcontractors, a third party may include, but is not limited to, any number of vendors, subcontractors, and suppliers, and an operator may be an airline, a leasing company, a military entity, a service organization, etc.

[0055] 7, aircraft 100 produced by method 600 may include an airframe 618 with high level systems 620 and an interior 622. Examples of high level systems 620 include one or more of a propulsion system 624, an electrical system 626, a hydraulic system 628, and an environmental system 630. Although an aerospace example is shown, the principles of the embodiments described herein may be applied to other industries.

[0056] Apparatus and methods embodied herein may be used during any one or more of the steps of method 600. For example, components or subassemblies corresponding to steps 608 and 610 may be fabricated or manufactured in a manner similar to components or subassemblies produced during the operational life of aircraft 100. Also, one or more apparatus embodiments, method embodiments, or a combination thereof may be utilized during steps 608 and 610, such as by substantially streamlining the assembly of aircraft 100 or reducing the cost of aircraft 100. Similarly, one or more of apparatus embodiments, method embodiments, or a combination thereof may be utilized during the operational life of aircraft 100, such as for, but not limited to, maintenance and service 616.

[0057] This disclosure includes subject matter described in the following clauses.

[0058] Clause 1. A method for enhancing operation of an aircraft (100), comprising: moving an airfoil (102) having a trip device (108) at a fixed position along the span of the airfoil (102) through an airflow such that air passing over a surface of the airfoil (102) creates a laminar boundary layer (302); and Creating a turbulent boundary layer (306, 308) when the airflow is downstream of a fixed-position trip device (108). the fixed position trip device (108) is at a position of the trip device (108) that is aft of the laminar boundary layer (302), such that the laminar boundary layer (302) extends a first length and the turbulent boundary layers (306, 308) extend a second length, the position of the trip device (108) allowing for laminar flow in the first length that increases aerodynamic efficiency and allowing for turbulent flow in the second length that reduces loading on the wing (102), thereby providing a fixed aft limit for the transition from the laminar boundary layer (302) to the turbulent boundary layer (306, 308).

[0059] Clause 2. The method of clause 1, wherein the location of the trip device (108) is aft of the target transition location (106).

[0060] Clause 3. The method of clause 1 or clause 2, wherein the position of the trip device (108) is at the target transition position (106).

[0061] Clause 4. The method of any of clauses 1 to 3, wherein the location of the trip device (108) is upstream of the target transition location (106).

[0062] Clause 5. The method of any of clauses 1 to 4, further comprising reducing movement of the shock on the wing (102), wherein the fixed position trip device (108) reduces downstream movement of the transition and associated movement of the shock location (110) on the wing (102) during transonic airflow.

[0063] Clause 6. The method of any of clauses 1 to 5, wherein the position of the trip device (108) reduces variation in aerodynamic forces between flight conditions.

[0064] Clause 7. The method of any of clauses 1 to 6, wherein the fixed position trip device (108) is a continuous trip strip along the span of the wing (102).

[0065] Clause 8. The method of any of clauses 1 to 7, wherein the fixed position trip device (108) is a plurality of separate elements along the span of the wing (102).

[0066] Clause 9. The method of any of clauses 1 to 8, wherein a dimension of the trip device (108) varies along the span of the wing (102).

[0067] Clause 10. The method of any of clauses 1 to 9, wherein the position of the trip device (108) on the airfoil (104) of the wing (102) varies along the span of the wing (102).

[0068] Clause 11. The method of any one of clauses 1 to 10, wherein the fixed position trip device (108) is along the upper surface (102) of the wing.

[0069] Clause 12. The method of any of clauses 1 to 11, wherein the fixed position trip device (108) is along either side of the vertical surface of the wing (102).

[0070] Clause 13. A method for manufacturing a blade (102), comprising the steps of: identifying a first target transition location (106) along a chordwise direction of a surface of an airfoil (104) under cruise conditions; predicting a plurality of target translation positions (106) under a plurality of design conditions; identifying a most downstream target transition location (106) from the plurality of target transition locations (106) such that shock onset is downstream of the identified most downstream target transition location (106) along a chord of the airfoil (104) surface; incorporating a trip device (108) at a selected length along the span of the wing (102) aft of the downstream most target transition location (106); The method includes:

[0071] Clause 14. The method of clause 13, wherein the position of the trip device (108) reduces aerodynamic force variations between flight conditions.

[0072] Clause 15. The method of clause 13 or clause 14, wherein the trip device (108) is a continuous trip strip.

[0073] Clause 16. The method of any of clauses 13 to 15, wherein the trip device (108) is a plurality of separate elements.

[0074] Clause 17. The method of any of clauses 13 to 16, wherein the size of the trip device (108) and the position of the trip device (108) vary along the span of the blade (102).

[0075] Clause 18. A wing (102) of an aircraft (100) having a trip device (108) along the span of the wing (102), the location of the trip device (108) being aft of a target transition location (106) along a chord of an airfoil (104) of the wing (102), the trip device (108) preventing downstream movement of the laminar to turbulent transition and associated movement of an impact location (110) on the wing (102), and the location of the trip device (108) on the airfoil (104) of the wing (102) varying along the span of the wing (102).

[0076] Clause 19. A wing (102) of an aircraft (100) as described in clause 18, wherein the trip device (108) is a continuous trip strip along the span of the wing (102).

[0077] Clause 20. A wing (102) of an aircraft (100) according to clause 18 or clause 19, wherein the trip device (108) is a plurality of separate elements along the span of the wing (102).

[0078] Clause 21. A wing (102) of an aircraft (100) according to any of clauses 18 to 20, wherein the position of the trip device (108) on the airfoil (104) of the wing (102) varies along the span of the wing (102).

[0079] It is therefore to be understood that the disclosure is not limited to the specific embodiments illustrated, and that modifications and other embodiments are intended to be included within the scope of the claims. Moreover, while the above description and related drawings describe embodiments of the disclosure in terms of certain example combinations of elements and / or functions, alternative implementations may provide different combinations of elements and / or functions without departing from the scope of the claims. Accordingly, any reference numerals in parentheses appearing in the claims are provided for illustration purposes and are not intended to limit the scope of the claimed subject matter to the specific embodiments provided in the disclosure.

Claims

1. A method of enhancing controllability of an aircraft (100), comprising: moving an airfoil (102) having trip devices (108) at fixed positions along the transverse span of the airfoil (102) through an airstream such that air passing over a surface of the airfoil (102) creates a laminar boundary layer (302); generating a turbulent boundary layer (306, 308) when the airflow is downstream of the fixed position trip device (108); wherein the fixed position trip unit (108) is at a trip unit (108) position aft of the laminar boundary layer (302), such that the laminar boundary layer (302) extends a first length and the turbulent boundary layer (306, 308) extends a second length, the trip unit (108) position allowing laminar flow in the first length to increase aerodynamic efficiency and allowing turbulent flow in the second length to reduce loading on the wing (102), thereby providing a fixed aft limit for a transition location from the laminar boundary layer (302) to the turbulent boundary layer (306, 308); the trip device (108) position is at or aft of the target transition position (106); The method, wherein the target transition location (106) is a most downstream target transition location (106) among a plurality of target transition locations from laminar flow to turbulent flow during cruise predicted under a plurality of design conditions, including a plurality of cruise conditions of different speeds, altitudes, and weights.

2. 2. The method of claim 1, further comprising reducing movement of a shock location on the wing (102), wherein the fixed position trip device (108) reduces downstream movement of the transition location and associated movement of a shock location (110) on the wing (102) during transonic airflow.

3. The method of claim 1 or 2, wherein the trip device (108) position reduces aerodynamic force variations between the cruise conditions.

4. The method of any one of claims 1 to 3, wherein the fixed position trip device (108) is a continuous trip strip along the transverse span of the wing (102).

5. A method of manufacturing an airfoil (102), comprising the steps of: Identifying a first target transition location (106) along a chordwise direction of a surface of an airfoil (104) under cruise conditions; predicting a plurality of target transition locations from laminar to turbulent flow during cruise under a plurality of design conditions, including a plurality of cruise conditions of different speeds, altitudes, and weights; identifying a most downstream target transition location (106) from the plurality of target transition locations such that shock onset is downstream of the most downstream target transition location (106) identified along a chord of the airfoil (104) surface; incorporating a fixed position trip device (108) along the span of the wing (102) a length aft of the downstream most target transition location (106); The method includes:

6. The method of claim 5 , wherein a trip device (108) position reduces aerodynamic force variations between said cruise conditions.

7. The method of claim 5 or claim 6, wherein the trip device (108) is a continuous trip strip.

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