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Advanced Wing And High-Lift Design

Final Report Summary - AWAHL (Advanced Wing And High-Lift Design)

Executive Summary:
The AWAHL (Advanced Wing And High Lift design) project comprises wing and high lift design of a regional turbo jet aircraft. It has been carried out within the Green Regional Aircraft (GRA) ITD of Clean Sky JU. AWAHL has three partners, FOI (Swedish Defence Research Agency) in Stockholm, the university Polimi in Milan and the company ASCO Industries in Belgium. The current periodic report covers the entire duration of the project which was 19 months after project extension.

The work is divided in four work packages (WPs) where the wing is first aerodynamically designed by in-house CFD and optimization tools in the first work package WP1 with optimal performance and constraints. The optimized wing is then used as input to WP2 in which an aeroelastic wing is designed minimizing the weight of the wing based on CFD defined loads distributions. The high lift design is carried out in WP3 which is closely connected to WP4 where the mechanical kinematic design is made to ensure its feasibility.

The design of the wing was eventually carried out in 3D using gradient based optimization. The performance of the wing was then evaluated with the wing attached to the fuselage and with the pylon/nacelle wit flow through conditions. The aerodynamic performance constrains were fulfilled at all design points leaving sufficient margin for additional losses due to tails, flap installations etc. The size of the wing was increased above specification, which was agreed in the project, so that a sufficient amount of fuel could be loaded into the wing. Due to this, some additional investigations were carried out on a down-scaled wing due to discussions about the size of the wing; the performance is still above required targets at the higher Mach numbers.

The optimized wing was then used for an aeroelastic design by optimization of the wingbox. Two different materials have been taken into account, aluminum alloy and carbon fiber composite; minimum weight is the objective of the aeroelastic optimization. Two structural models were used based on a stick model of the whole aircraft and on a detailed FEM model of the wing, respectively. Both strength and stability constraints have been included into the minimum weight Nastran optimization. The optimized structural weight of the wing is less than half with carbon fiber composite compared to the weight with aluminum. The performance was then evaluated by CFD investigations using the deformed wing. The higher the tip rotation, the worse becomes the aerodynamic performance.

A conventional three element high lift system with a forward slat and single slotted rear flap was developed from the designed wing in WP1. The design of the high lift configuration is carried out in 2.5D assuming infinite wing sweep with the leading edge sweep angle. The designs are then extended to a 3D wing, the performance of the high lift configurations are assessed from CFD calculations of the full 3D configurations including fuselage and pylon/nacelle. The performance was evaluated for both a landing and take-off configuration. The performance is acceptable but depending on which surface is used for the non-dimensional forces, the surface being either the specified surface or the actual surface of the enlarged wing. Due to kinematic constraints it was not possible to scale down the wing. Some attempts to improve the performance were made by adjusting the deflections of the flap and slat. The maximum lift increases about 12% indicating that the design in 2.5D is questionable for a wing with such a high sweep angle.

Several concepts for the kinematics of actuation of the slat and flap were investigated. For the slat, the only feasible and adequate alternative was the hydraulic actuation option due to the confined space at the leading edge. For the flap a ‘fixed rotating carriage’ concept was selected.

Project Context and Objectives:
The AWAHL project comprises wing and high lift design of a regional turbo jet aircraft. It has been carried out within the Green Regional Aircraft (GRA) ITD of Clean Sky JU. AWAHL has three partners, FOI (Swedish Defence Research Agency) in Stockholm, the university Polimi in Milan and the company ASCO Industries in Belgium. The current periodic report covers the entire duration of the project which was 19 months after project extension. AWAHL responded to the first batch of of open calls 2010 within JTI, no. JTI-CS-2010-01-GRA-02-007. The total budget of the project has been 450,000 €.

The work is divided in four work packages (WPs) where the wing is first aerodynamically designed by in-house CFD and optimization tools in the first work package WP1 with optimal performance and constraints. The optimized wing is then used as input to WP2 in which an aeroelastic wing is designed minimizing the weight of the wing based on CFD defined loads distributions. The high lift design is carried out in WP3 which is closely connected to WP4 where the mechanical kinematic design is made to ensure its feasibility.

The design of the wing was eventually carried out in 3D using gradient based optimization. The performance of the wing was then evaluated with the wing attached to the fuselage and with the pylon/nacelle wit flow through conditions. The aerodynamic performance constrains were fulfilled at all design points leaving sufficient margin for additional losses due to tails, flap installations etc. The performance of the wing can be seen in Figure 1 below in which the required targets are displayed as well for the four defined design points. The size of the wing was increased above specification, which was agreed in the project, so that a sufficient amount of fuel could be loaded into the wing. Due to this, some additional investigations were carried out on a down-scaled wing due to discussions about the size of the wing; the performance is still above required targets at the higher Mach numbers.

Figure 1. CL/CD versus CL for the optimized wing-body and wing-body-nacelle geometry.

The optimized wing was then used for an aeroelastic design by optimization of the wingbox. Two different materials have been taken into account, aluminum alloy and carbon fiber composite; minimum weight is the objective of the aeroelastic optimization. Two structural models were used based on a stick model of the whole aircraft and on a detailed FEM model of the wing, respectively. Both strength and stability constraints have been included into the minimum weight Nastran optimization. The optimized structural weight of the wing is less than half with carbon fiber composite compared to the weight with aluminum. The performance was then evaluated by CFD investigations using the deformed wing. The higher the tip rotation, the worse becomes the aerodynamic performance.

A conventional three element high lift system with a forward slat and single slotted rear flap was developed from the designed wing in WP1. The design of the high lift configuration is carried out in 2.5D assuming infinite wing sweep with the leading edge sweep angle. The designs are then extended to a 3D wing, the performance of the high lift configurations are assessed from CFD calculations of the full 3D configurations including fuselage and pylon/nacelle. The performance was evaluated for both a landing and take-off configuration. The performance of the landing configuration is displayed in Figure 2. The maximum lift of the landing configuration is CL=2.86 which just above the required level of CL=2.85. This value, however, is obtained by a using the reference surface of 113 m2 instead of the actual wing surface of 133 m2. With the actual wing surface, the maximum lift is only CL=2.43. Some attempts to improve the performance were made by adjusting the deflections of the flap and slat. The maximum lift increases about 12% and can probably be increased even more. The performance is then acceptable regardless of the scaling surface. This also indicates that the design in 2.5D is questionable for a wing with such a high sweep angle.

Figure 2. Left: Lift vs. incidence for landing configuration. Right: L/D vs. lift for take-off conf.

Several concepts for the kinematics of actuation of the slat and flap were investigated. For the slat, the only feasible and adequate alternative was the hydraulic actuation option due to the confined space at the leading edge. For the flap a ‘fixed rotating carriage’ concept was selected.

The AWAHL project has been successful and has given the partners new insights and experiences in wing and high lift design. The work has been challenging with many discussions, some parts of the work shown to be difficult and more time consuming than expected which has resulted in extension of the project. Some of the lessons learnt from the project are that some more geometric and structural design constraints would have been useful, the wing and high-lift designs in 2.5D were questionable and that the high lift aerodynamic and kinematic design should have been considered in the beginning of the project.

Project Results:
This is a summary of the results obtained in the project AWAHL and has been taken from the final deliverable D0.1 within the project.

3.1 Introduction

This report concludes the findings of the AWAHL (Advanced Wing And High lift design) project. The purpose of AWAHL has been to design a wing with its high lift system for an advanced regional turbo-fan aircraft with optimal performance. The work is divided in four work packages (WPs) where the wing is first aerodynamically designed by in-house CFD and optimization tools in the first work package WP1 with optimal performance and constraints. The optimized wing is then used as input to WP2 in which an aeroelastic wing is designed minimizing the weight of the wing based on CFD defined loads distributions. The high lift design is carried out in WP3 which is closely connected to WP4 where the mechanical kinematic design is made to ensure its feasibility.

The AWAHL consortium consists of three partners, the Swedish defence research agency FOI being the coordinator, the Italian university POLIMI and the Belgian company ASCO. FOI has been responsible for the wing design (WP1) and high lift design (WP3), Polimi was responsible for the aeroelastic wing design (WP2) and ASCO for the kinematics high lift design (WP4). Alenia who has monitored the technical work in the project has determined the target performance and requirements of the aircraft. Initially the project was scheduled to last for 10 months but was extended to 18 months of duration due to some encountered delays.

This short report summarizes the findings of the technical work of AWAHL. Each work package is summarized in four separate reports that describe the findings and results in more details, deliverables D1.2 D 2.2 D3.2 and D4.2 as defined in the Description of Work. In the following sections each of the work packages are described and summarized including the main findings. At the end a summary is given including come conclusions and lessons learned.

3.2 Wing Design (WP1)

The goal of wing design was to achieve given glide factors (L/D) at cruise speeds (M∞ = 0.74; 0.78; 0.81) close to trimmed conditions (CL between 0.45 and 0.56) and one subsonic speed M∞ = 0:41 with higher lift coefficient (0.8). The wing shape is dictated primarily by the required minimum fuel volume between the front and rear spars, maximum relative thickness at the wing root, kink and tip sections and by the total wing surface. To maximize the volume, it was decided to have the front and rear spars at minimum and maximum chord, which is at 18 and 72% local chord No minimum thickness for the wing sections was given which later on turned out to be problematic for the -design, in particular the kinematic design.

The optimization of wing is based on gradient based optimization. Here we make use of the unstructured flow solver Edge [1] in order to solve both the compressible Euler equations and the adjoint flow equations [2]. The software AESOP integrates geometrical parameterizations, mesh deformation algorithms, the flow solver Edge, adjoint solver and optimization algorithm in one platform [3]. The drag is the objective function being minimized. Note that the optimization is based on inviscid calculations; the optimized configurations are validated using viscous RANS calculations with Edge. The computational grids are made with a combination of the commercial software IcemCFD and the in-house mesh generator TRITET [4][5] for unstructured grids.

Some effort to design wing sections assuming 2.5D (assuming infinite wing sweep) was made initially where separate optimizations were made for the root, kink and root airfoils. Although several optimizations were conducted, the performance when extending the optimized airfoils to a 3D wing was never sufficiently close to what was required. This approach was hence abandoned and the design continued directly in 3D.

An initial wing plan form was supplied by Alenia. To ensure that a sufficient fuel volume could be stored between the spars, the wing span was extended about 2.5 m (half span). Due to the high Mach number (M∞ = 0.81) a high sweep angle was selected close to its maximum allowed value. This wing plan form was kept constant during the optimization. The optimization optimized the wing shape in span-wise sections as well as the wing dihedral. The optimization was done in two steps starting with an optimization for the highest Mach number (M∞ = 0.81) and, in the second step, an optimization for the remaining three Mach numbers (M∞ = 0.41 0.74; 0.78) with a penalty on deviation from the drag at the highest Mach number in the first step.

The wing plan form and the optimized wing with its sectional airfoils can be seen in Figure 2.1. Both the initial, the high speed (M∞ = 0.81) and the final shapes of the airfoil sections are given. The data of the final wing is given in Table 2.1.

Figure 2.1. Left: Wing plan form. Right: Initial, high-speed design and low-high speed design wings.

Wing surface 133 m2

Wing reference surface 113 m2

Mean aerodynamic chord 3.817 m

Wing span 35.960 m

Wing sweep 32.89º

Fuel volume 24.714 m3

Root chord 6.579 m

Kink chord 3.567 m

Tip chord 1.658 m

Front spar 18% chord

Rear spar 72% chord

y-position of root 1.706 m

y-position of kink 6.337 m

Kink twist angle 2.922º

Root twist angle 6.346º

Wing span 35.960 m

Table 2.1: Properties of the designed wing.

The locations of the front and rear spars were chosen at the most upstream and downstream locations, respectively, in order to allow for as large fuel volume as possible. The final volume of the fuel is 10% larger than what was initially required which was 22.47 m3 (the volumes given are actual geometric volumes without any safety factor). The reason for this is the extension of the wing and some ambiguous information if the volume inside the fuselage should be taken into account or not. Note also that the actual wing surface is larger than the upper bound of 118 m2 according to the specifications. The reason for the enlarged wing is the extended tip being agreed on at an early stage of the project to ensure the required fuel volume.

The optimized wing is attached to the supplied fuselage. In addition, the nacelle is attached on a designed pylon to the kink of the wing. The performance of the entire configuration is then investigated with CFD RANS calculations. The performances of the wing-body and wing-body-nacelle configuration are shown in Figure 2.2 in which the required targets are displayed as well for the four design points. The aerodynamic performance constrains are fulfilled at all design points leaving sufficient margin for additional losses due to tails, flap installations etc.

Figure 2.2. CL/CD versus CL for the optimized wing-body and wing-body-nacelle geometry.

The sensitivity of the location of the nacelle in axial and stream wise position was carried out, the span wise position remained constant. The sensitivity is in general small and is largest in the axial position for the lowest Mach number.

An additional investigation of a downscaled wing with a reference area of 118 m2 was made to get an idea of its performance. The motivation for this investigation was that there were issues and discussions about the enlarged wing; this is further discussed in the high lift design below. The downscaled wing was attached to the same fuselage and pylon/nacelle as the larger initial wing. The study revealed that its performance is still above required targets at the higher cruise Mach numbers, it is just slightly below for the low Mach number design point. In addition, an estimation of the performance of the wing scaled to 112 m2 was carried out as well as an investigation of straightening the leading edge of the wing and the effect of the wing geometry reconstruction.

3.3 Wing aeroelastic design (WP2)

The scope of WP2 was the aeroelastic optimization of the wingbox of the wing aerodynamically optimized by FOI. Aiming at this main target, two different tiers of structural models have been adopted. Tier one is a stick model for the whole airframe where lumped mass and beam elements are used. They represent a first level of prediction of inertial loads and stiffness distribution across the whole aircraft is well suitable for conceptual structural sizing. This model has been created using a software called NeoCASS, developed by POLIMI during FP6-SimSAC project and recently developed as Open Source Project (www.neocass.org). Using this approach it is very easy to generate a stick model of a full aircraft and perform the most classical structural and aeroelastic analysis such as modal analysis, static aeroelastic and flutter analysis.

Tier two is a hybrid model including the original stick model of fuselage and tail planes connected to a detailed finite element model of the wing. Finally, the detailed FEM model of the wing has been adopted to perform the structural optimization using MSC/NASTRAN SOL200. Indeed, starting from the structural properties of the stick model determined using NeoCASS software; a static optimization has been formulated taking into account for stress, displacement and stability constraints. Once the optimal solution in terms of minimum weight has been found, the new structural properties have been fed back to keep the stick model aligned with the optimal hybrid model based on a detailed 3D FEM model of the wing.

The structural optimization of the wingbox has been performed using a classical wingbox configuration based on two main spars and Z-shaped stiffeners, as reported in Figure 2.1.

Figure 2.1: Overview of the procedure adopted inside WP 2.

Figure 2.2 shows the wingbox structure embedded into the CAD file of the full aircraft and the final FEM model of the wingbox.

Figure 2.2: Overview of the FEM model adopted for optimization.

Two different materials have been taken into account, i.e. aluminum alloy and carbon fiber composite, whose properties are reported in Table 2.1. The aerodynamic loads based on VLM and computed during the conceptual design of the aircraft, together with the mass distribution represented by lumped masses (CONM2 cards), have been transferred to the wingbox model.

Aluminium - 7075-T6

σy,c [MPa] 413.7

Ec [GPa] 70.0

ρ [Kg/m3] 2800.0

σall [MPa] 233.0

Carbon fibre ply - IM7/8552

E11 [GPa] 150 XT [MPa] 2323.0

E22 [MPa] 9080 XC [MPa] 1200.0

G12 [MPa] 5290 YT [MPa] 101.4

■xy 0.32 YC [MPa] 199.8

ρ[Kg/m3] 1500 SL [MPa] 107.0

Thickness [mm] = 0.13

0.13

Table 2.1: Material characteristics.

The structural optimization problem includes 60 design variables, defining the wingbox structural properties (10 variables) in 6 structural zones along wingspan. Both strength and stability constraints have been included into the minimum weight Nastran optimization by means of DEQATN cards. On the final optimized wingbox a divergence and flutter analysis has been performed to check the reliability of the obtained solution.

Figure 2.3: The wingbox model adopted for structural optimization (left) and the variable linking (right).

A summary of the obtained optimal solution is reported in Table 2.2:

Table 2.2: Optimal solution.

For the optimal solution an aerodynamic assessment has been started in cooperation with FOI, by computing the deformed shape in cruise conditions using the CFD based loads transferred to the structural mesh, and transferring back to the CFD mesh the structural deformed configuration. At the first step of this assessment the optimal wing appears as too much flexible, in terms of Tip rotation in cruise, mainly due to the absence of any stiffness constraint during the optimization. To help the designer in defining a new structural configuration a set of 6 optimization runs has been preformed to set up the Pareto front correlating the Tip rotation with the structural mass. Figure 2.4 shows a comparison between wing deflection in cruise and at max load factor, while Figure 2.5 shows the final Pareto front.

Figure2.4: Composite case, cruise speed @1g (left) and 2.5g (right) levels.

Figure2.5: The resulting Pareto Front for the composite wing.

3.4 Wing high lift design (WP3)

A conventional three element high lift system with a forward slat and single slotted rear flap was developed from the designed wing in WP1. The slat and flap are segmented with the division line at the position of the pylon at the kink of the wing. The slat extends along the entire leading edge whereas the flap extends to about 75% of the span. The geometry of the configuration is displayed in Figure 3.1 below.

Figure 3.1. High lift configuration.

The design of the high lift configuration is carried out in 2.5D assuming infinite wing sweep with the leading edge sweep angle. Optimizations are carried out based on 2.5D CFD simulations for the kink airfoil. The extension of the slat is limited by the position of the front spar minus a margin of about 2% chord; hence the slat extends from the leading edge until 15.5% local chord. The flap is designed with the same constraints and extends from 74.3% chord to the trailing edge. The optimization is carried out for the position and rotation of the two elements as well as the shape of the configuration that is not visible when deployed.

The design is first carried out for the landing configuration using stochastic population based methods built into an in-house tool [6]. The lift is maximized at two angles of attack for the landing configuration. Two angles were selected, one in the linear range and one close to maximum lift, to avoid flow separation at lower incidences and reattachment at maximum lift. There is a close interaction with the kinematic design in WP4 to ensure that the design is realistic and possible to manufacture. The design for take-off is done in a similar manner in 2.5D freezing the shape of the elements and optimizing the position and deflection angles of the slat and flap obeying the kinematic constraints for the landing configuration. Furthermore, the glide factor is maximized (lift over drag) for the take-off configuration.

The designs in 2.5D are then extended to a 3D wing by using a geometrical transformation from the kink airfoil to airfoil sections along the span. The final performance of the high lift configurations are then assessed from CFD calculations of the full 3D configurations including fuselage and pylon/nacelle. The performances of the configurations were performed at M∞ = 0.2 with different requirements concerning maximum lift at landing and glide factors at take-off. The performance of the 3D landing and take-off configurations can be seen in Figure 3.2

Figure 3.2. Left: Lift vs. incidence for landing conf. Right: L/D vs. lift for take-off conf.

The maximum lift of the landing configuration is CL=2.86 which just above the required level of CL=2.85. This value, however, is obtained by a using the reference surface of 113 m2 instead of the actual wing surface of 133 m2. With the actual wing surface, the maximum lift is only CL=2.43. The take-off performance is above required levels for both specified design conditions where the reference surface has been used. If the actual wing surface is used, this would correspond to a shift of the two curves to the left in the right figure above which results in glide factors more or less on top of what was required.

There were several discussions which wing surface to use for the force coefficients. It is clear that the performance of the landing configuration is far below the required level of maximum lift using the actual wing surface. On the other hand, it was necessary to increase the size of the wing to store the required volume of fuel which was also agreed by all partners. If the larger wing does not contribute to an increased weight of the total aircraft one can argue that it is fair to use the reference surface. There were also suggestions to scale down the designed wing to an acceptable size which was done for the wing without a high lift system in WP1. However, the kinematics design of the slat could not be realized for a scaled down configuration at the outer part of the wing due the very thin wing in this region.

Nevertheless, attempts were made to increase the performance by changing the deflections of both the slat and the flap for both the landing and take-off configurations. The deflections were varied by hand and by intuition to what was believed to potentially increase the maximum lift. This was also a way to verify the quality of the design in 2.5D which may be questionable for a wing with such a high wing sweep angle (32.89º).

The deflection angles of the inner and outer slat and flap were varied, in most cases increased, individually and in combination up to 15º. Altogether four landing configurations were evaluated and one take-off configuration in addition to the initial designs. These new configurations do not obey the kinematic constraints as the original designs do; the new configurations are purely a way to see if the performance can be increased and to justify the design in 2.5D. Figure 3.3 reveals the results obtained for all configurations. The maximum lift increases to CL=3.2 for one of the landing configurations, or to CL=2.72 normalizing with the actual wing surface. Obviously, this is a large improvement to the original design and the results with the actual wing surface are close to what was required. The results are improved for the take-off configuration as well. It is not unlikely that the results can be further improved. This exercise demonstrates that the design in 2.5D is questionable for configurations with such a high wing sweep and that a design in 3D may have to be considered in the future.

Figure 3.3. Left: Lift vs. incidence for 5 landing conf. Right: L/D vs. lift for 2 take-off conf.

3.5 High lift kinematic design (WP4)

Within WP4, ASCO elaborated conceptual deployment mechanisms for both 3D leading edge and trailing edge high lift design resulting from WP3. More specifically, this came down to defining different actuation concepts for slats and flaps, assessing them by comparing required and available space allocation in the fixed wing as well as computing the applicable components and interface loads. The deployment concepts found to be the most adequate for the subject devices were then further matured. Sketches from various stations along the wing span were drawn, inputs were given to reach a realistic 3D design, interface loads were derived to enable preliminary sizing of the main actuation components and kinematical checks were carried out.

As already mentioned previously in this report, the encountered problem in terms of leading edge high lift device integration on the 3D AWAHL wing was due to the extremely confined space available at the leading edge of the outboard sections of the wing. This space allocation constraint made down-selection and integration of an adequate actuation mechanism not straightforward. It was even concluded that the classical rack-and-pinion actuation, which was initially envisioned in the Description of Work, was not compatible with the AWAHL WP1 wing and its required performance. The figure below shows the encountered integration issues on a wing tip station (pinion out of wing envelope and large front spar penetration by slat track).

Figure 0.2. Slat #5 OB support – preliminary sized actuation mechanism sketch

Several alternatives were investigated to solve this issue: thickening of the 3D wing, elimination of the outboard slat, the usage of Krueger flaps instead of slats and the actuation of the slats by means of hydraulic pistons instead of a rack and pinion mechanism. In the end, the only feasible and adequate alternative was the hydraulic actuation option. Examples of such applications already exist, e.g. Falcon 900LX and Boeing 737 (Figure 0.3).

Figure 0.3. Slat hydraulic actuation on Falcon 900LX and Boeing 737

Once this wing integration issue was solved, the ASCO team analysed and gave feedback to FOI regarding the provided preliminary span wise 2D-sections of the wing with the high lift devices in retracted and landing setting. After some iterations, the 3D landing and take-off configurations depicted in Figure 0.4 were obtained.

Figure 0.4. 3D wing with final 4 slats landing (middle) and take-off (right) settings

On the trailing edge side, the high lift device chosen for the AWAHL wing was a commonly used single slotted flap. Following the correction of a few rear spar clash and clearance issues in the first sketches generated within WP1 and WP3, ASCO carried out detailed kinematic designs and integration assessments. Several flap actuation concepts were investigated. Two concepts were found to be suitable for the AWAHL wing and high lift device design. In the end, only the most promising ‘fixed rotating carriage’ concept was further matured. Preliminary sizing of the flap actuation mechanism revealed that this system could be integrated and was compatible with the AWAHL wing. Figure 0.5 depicts the 3D flap configuration and ‘fixed rotating carriage’.

Figure 0.5. Defined flap configuration and 3D representation of ‘fixed rotating carriage’ concept

Just like for the slats, ASCO helped FOI to optimize their initial proposal for the landing and take-off configurations of the trailing edge flaps. The outcome of that iterative process is visible in Figure 0.6.

Figure 0.6: 3D flap landing (left) and take-off (right) setting

3.5 Summary and lessons learned

In AWAHL a wing for a regional turbo jet aircraft has been designed. A conventional three element high lift system has been designed for the wing along with its kinematics to deploy the slat and flap to ensure that the high lift system is realistic. The structure of the wing has been optimized to minimize its weight and the aerodynamic performance of the deformed wing has been analyzed.

The performance of the designed wing is good and above specified targets although the wing was enlarged to host the required level of fuel. The designed high lift system shows acceptable performance depending on the scaling surface (actual or reference) of the force coefficients. An additional exercise demonstrates that the high lift system can be further improved. The structural weight of the wing can be reduced substantially which degrades the aerodynamic performance as a consequence.

The AWAHL project has been successful and has given the partners new insights and experiences in wing and high lift design. The work has been challenging with many discussions, some parts of the work shown to be difficult and more time consuming than expected which has resulted in extension of the project. Some of the lessons learnt from the project are:

− There were some lack of geometric constraints specified in the project requirement, in particular on minimum wing thickness making the integration of the high lift system unnecessarily difficult

− The wing design was improved considerably when carried out in 3D compared to 2.5D due to the relatively high wing sweep.

− The high lift design in 2.5D is obviously not optimal, probably due to the high wing sweep causing many 3D effects. A design in 3D may be considered in future high lift designs

− The requirements from the high lift aerodynamic and kinematic design should have been considered in the beginning of the project in the wing design. In this way the outer part of the wing could have been made thicker with minimum thickness constraints.

− There were lack of requirements or targets for the structural design such as e.g. acceptable weights, deformations, stiffness

− There was ambiguity from Alenia concerning constraints for the wing size, fuel volume and spacing

Overall the outcome of the AWAHL project is believed to be of a high quality thanks to the highly skilled and dedicated persons performing the work at FOI, Polimi and ASCO with the strong support by Alenia

Potential Impact:
AWAHL has had an impact within the Green Regional Aircraft (GRA) demonstrating that a wing with high performance well above targets can be designed with numerical methods. From the designed wing designs for an aero-elastic wing and for a high lift system were made as well with a good outcome. Furthermore, the high lift design has been shown to be realizable from the kinematic design.

The limited success of the wing and high lift design in 2.5D assuming infinite wing sweep will be considered in future aircraft designs where the wing has a high sweep. For such configurations, the design may be made directly in 3D from the beginning.

The outcome and results of AWAHL has been disseminated within GRA.

No conference proceedings or peer review articles have been produced. No applications for patents have been done.

The results from AWAHL will be exploited in several ways by both FOI, Polimi and ASCO. AWAHL has brought FOI, Polimi and ASCO closer together stimulating further work and projects together.

There are many lessons learned from the projects that will be exploited by the partners in the future. These include e.g. that some more geometric and structural design constraints would have been useful, the wing and high-lift designs in 2.5D were questionable due to the high wing sweep and that the high lift aerodynamic and kinematic design should have been considered in the beginning of the project.

No patents, trademarks, registered designs etc. have been produced.