© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The continuous search for aircraft flight performance to obtain lower fuel consumption leads to the optimization of wings shape and structure focused in the longer flight phase of its mission, the cruise phase. However, this leads to a loss of efficiency for other flight phases such as take-off and landing, resulting in the need for high-lift surfaces, that are basically triggered by electro-mechanical or hydro-mechanical actuators, adding a considerable amount of weight, complexity and cost to the design project. New concepts of aircraft have wing solutions that are optimized for every flight phase and, consequently, are capable of adjusting their structures in order to achieve the best performance on each flight situation. One of the main ideas on how to get this result is the implement of morphing wings by using smart actuators. Shape memory alloys are classified as smart materials and they can be used in order to develop light, simple and cheap solutions to obtain controlled modifications on aircraft aerodynamic surfaces. This paper focuses on evaluating the airfoil thickness effects on morphing wings composed by memory alloy actuators capable of camber adjustment. In order to achieve this goal, the morphing NACA 0020 designed for the present project is compared to a morphing NACA 0012 wing prototype. The fact that previously mentioned prototypes have different airfoil thickness promotes the ideal environment to investigate this effect on the performance of morphing wings capable of camber adjustment. In addition, each previously mentioned morphing wing prototype was compared to its traditional flap configuration to investigate the aerodynamic pros and cons related to this morphing mechanism. The comparison shows that despite the morphing wing as studied resulting in a lower performance, it’s design simplicity and weight reduction brings advantages to the whole aircraft in certain conditions.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Aircraft with three engines, as known as trijet, became a standard design among manufacturers after 1964 when the FAA's 60-minute rule was established for these aircraft. This regulation restricted the flight path to 60 minutes' flying time to a suitable airport, therefore affecting the operation costs and limiting the range of twin-jet aircraft. However, improvements to the engine's reliability in the following decades allowed ETOPS certification for twinjet aircraft. The traditional trijet designs were slowly retired, the last commercial trijet flight was in 2014.The industry abandoned the trijet design as solution for commercial aviation; however, executive jets such as the Falcon 7x and Falcon 8x, certified in 2016, show that this configuration might still be advantageous for specific markets. The certification at one engine inoperative condition presents an advantage for trijet aircraft, reducing takeoff thrust, since when one engine is inoperative, 75% of the total thrust is available for the trijet aircraft, while this value is only 50% for a twin-jet aircraft. An initial study conducted showed a trend of lower thrust to weight ratio for trijet aircraft when compared to twinjet aircraft, being particularly evident for MTOW (maximum takeoff weight) lower than 75,000 lb. The aircraft design is related to a multidisciplinary view. So, the thrust reduction and the implementation of a third engine have impacts on fuel burn, structural weight, external noise, performance, certification, maintenance, and the fuel feed system. In this sense, the multidisciplinary view justifies distinct thrust to weight ratio reduction caused by trijet configuration for different MTOW range. The aim of this work was to study the viability of a trijet aircraft configuration and potential advantages for a regional aviation scenario. The trijet configuration performance was evaluated and compared to twinjet configuration in a multidisciplinary design environment considering disciplines such as aerodynamics, noise, performance, flight mechanic, weight, and structure. An aircraft with MTOW of 48,500 lb. was studied and the results showed that a reduction up to 6.25% of installed thrust might be achieved with the trijet design compared to twin-jet aircraft when the field length defined by aviation regulations is the critical constraint. However, flyover noise, structural weight and direct operating cost might increase in trijet design.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.An experimental investigation has been undertaken to study the wavy leading edge phenomena on rectangular wing of aspect ratio 4 with a NACA 0020 airfoil at Reynolds number range from 700,000 to 3,000,000. Force measurements for various shapes of sinusoidal leading edge indicate smaller amplitude and shorter wavelength configuration (A3λ11) presenting a substantial increase in aerodynamic performance at entire range of Reynolds number tested when compared to baseline configuration, as result achieving 28.3 % of increasing in maximum lift coefficient. Oil flow visualizations reveal that tubercles with smaller amplitude have the role of delaying trailing edge flow separation. At high angles of attack, the A3 λ 11 configuration is shown to present spanwise wavelengths for which the optimal generation of streaks in turbulent boundary layers is expected according to previous experimental works. The appearance of such streaky boundary layers is a possible reason for the delay in flow separation and increase of maximum lift coefficient.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Optimization of wing shapes has been a constant struggle throughout the years of aircraft and aerodynamic development. Innovations have flourished in all scientific fields that influence wing design, such as materials, structural, manufacturing and aeronautical engineering, in order to improve performance and consequently reduce fuel consumption of aircraft, which translates in a light wing with an airfoil shape that assures the best lift coefficients required for a specific mission. On the other hand, this penalizes other maneuver possibilities for the same aircraft, hindering its capabilities and demanding development of different solutions, impacting on costs and draining resources. An “one fits all” concept solves this hurdle, since one design could accomplish a variety of missions, with adequate values for lift coefficient for each different flight phase. This concept can be achieved by wings capable of morphing, adjusting their structures on demand. One widely investigated field of research is morphing wings that uses smart materials, such as shape memory alloys, for actuation. Shape memory alloys are lightweight, simple and cheap materials that, combined with a morphing compliant rib, can achieve controlled displacements on aerodynamic surfaces. This paper analyses different rib concepts modifying chordwise positions for actuation by making use of shape memory alloy wires built-in a NACA 0012 reference wing. A comparison is made between different percentages of chordwise morphing capability and a simple NACA 0012 wing with a 25 percent chord plain flap, as usually seen on many simple aircraft designs. The results show an increase on lift coefficient values and a delay of stall angle for some chordwise actuation locations. The comparison parameter was a 15 degree of trailing-edge tip displacement related to the airfoil leading-edge. By reducing external surface gaps and steps, a simple and lightweight smart morphing wing can overcome a common flap design and still achieve a variety of different missions by adjusting itself in flight.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This work investigates wavy leading edge phenomena at transonic flow regime. Pressure sensitive paint measurements are performed over upper surface airfoil at transonic flow regime. The experimental investigation was conducted at a transonic wind tunnel at Reynolds number of 1,000,000, Mach number from 0.6 to 0.7, and angle of attack from 0 to 4 degrees. Two sets of airfoil were used, a smooth NACA0012 profile as baseline model and a wavy leading edge NACA0012 profile with amplitude of 3% and wavelength of 11% both related to chord of the airfoil. The models were manufactured using a 3D rapid prototyping which significantly improved time and cost, and also the feasibility and accuracy of such complex wavy leading edge airfoil. Pressure sensitive paint measurements indicates an impressive modification on flow pattern caused by tubercles when compared to baseline airfoil. If on hand, the baseline airfoil presents lambda-shock wave pattern, on the other hand, the wavy leading edge model changes this flow pattern avoiding shock wave structure. A likely explanation for tubercles avoid shock wave is related to possible counter-rotating vortex generated by wavy configuration upstream of the shock wave line. Thus, the results presented here indicates a potential to apply tubercles in commercial aircraft wings at transonic regime in order to decrease drag rise.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The swept wing configuration showed interesting results for the leading edge phenomena in recent studies. The most important outcomes showed that configurations with higher wing loading at the tip (such as tapered and swept wings), tend to be more susceptible to the effect of tubercles, giving an important increase in stall angle, and consequently, in maximum lift coefficient. A remarkable gain of about 20% on CLmax (without large penalties on drag coefficient) was obtained in 30° swept models with taper ratios of 1 and 0.5.This increase in lift force is associated to the fact that the wavy configurations exhibit a delay on stall progression from wing tip to the root as consequence of the tubercle effects, which maintain the flow attached on leading edge at high angles of attack. To investigate the relationship between the increase in maximum lift coefficient and the swept angle, and continue with the study presented by Abrantes et al.11, a series of experiments were conducted on six wing configurations. The range of sweep-angles include wings with 30°, 40° and 50°, as well as two variations of taper ratio (TR=1 and TR=0.5). All models had an underlying NACA 0020 airfoil and a wavy geometry with amplitude A=0.03c and wavelength λ=0.11. The purpose of this research consisted in evaluating the drag and lifts forces at Reynolds number of 200,000 for all seven models and compares their results with the smooth wings. In addition, a flow visualization analysis using oil technics was included in order to better understand the involved phenomena.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The study of wavy leading edge phenomena on finite wings conducted on recent research has shown results that demonstrate improvements in aerodynamic characteristics for certain configurations. The most important outcomes were observed on swept and swept-tapered wings, attaining improvement in lift coefficients of around 20% when compared with their equivalent baseline models. This increase on lift force is associated to the fact that the wavy configurations exhibit a delay on the stall angle due to the effect of the tubercles, which main effect is to delay the stall progression from tip to root by keeping the flow attached on the leading edge at high angles of attack. Visualization results confirmed larger effect of these phenomena on the wingtip area. In order to give continuity to previous works that investigated swept wing with wavy leading edge, obtain a deeper knowledge of this phenomena and delimit the design space in which the wavy leading edge could be efficiently applied, a series of experiments were conducted on sixteen wing configurations including swept angles of 30 and 50 degrees, taper ratio of 1 and 0.5, and wavy span length of 20, 40 and 100% (from tip to root). All models had an underlying NACA 0020 airfoil and a wavy geometry with amplitude A = 0.03 and wavelength λ = 0.11 considering the root chord as reference. The purpose of this research consist in evaluating of drag and lift forces at Reynolds number of Re = 200, 000 for all models showing comparative results with the baseline wings. In addition, a flow visualization analysis using oil technique was included in order to better understand the involved phenomena.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.As a passive flow control mechanism inspired in nature, the wavy leading edge modifications have been tested here for specific rotary-wing airfoils. After examining previously studies, it was observed that these geometric devices could delay the boundary layer separation that usually occurs at high angles of attack in retreating blades, avoiding their abrupt stall. In order to evaluate if wavy leading edges could be applied successfully on helicopter blades, a series of wind tunnel tests have been performed for selected rotary-wing airfoils used in the H-60 Black Hawk aircraft. The waviness has shown a great potential to make softer the stall characteristics for the Sikorsky SC1094-R8 airfoil, a modified profile of the Sikorsky SC1095, while delaying the initial stall by up to 3◦, without a relevant increase in drag coefficient. The experimental investigation was based on force measurements (lift and drag coeficients) and oil flow visualization.

© 2018 The Author(s).Aircraft with three engines, as known as trijet became a standard design among manufacturers after 1964 when the FAA's 60-minute rule was established for these aircraft. This regulation restricted the flight path to 60 minutes' flying time to a suitable airport, therefore affecting the operation costs and limiting the range of twin-jet aircraft. However, improvements to the engine's reliability in the following decades allowed ETOPS certification for twin-jet aircraft. The traditional trijet designs were slowly retired, the last commercial trijet flight was in 2014.The industry abandoned the trijet design as solution for commercial aviation; however, executive jets such as the Falcon 7x and Falcon 8x, certified in 2016, show that this configuration might still be advantageous for specific markets. The certification at one engine inoperative condition presents advantage for trijet aircraft reducing take-off thrust, since when one engine is inoperative, 75% of the installed thrust is available for the trijet aircraft, while this value is only 50% for a twin-jet aircraft. An initial study conducted showed a trend of lower thrust to weight ratio for trijet aircraft when compared to twin-jet aircraft, being particularly evident for MTOW (maximum take-off weight) lower than 75,000 lb. The aim of this work is to study the viability of a trijet aircraft configuration and potential advantages for a regional aviation scenario. The trijet configuration performance was evaluated and compared to twin-jet configuration in a multidisciplinary design environment considering disciplines such as aerodynamics, noise, performance, flight mechanic, weight, and structure. An aircraft with MTOW of 48,500 lb was studied and the results show that a reduction up to 9.4% of installed thrust might be achieved with the trijet design compared to twin-jet aircraft when the balanced field length is the critical constraint. However, flyover noise and structural weight might increase slightly in trijet design.

© 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The Flight Simulator (FS) is a key aspect of the traditional aeronautical industry and the general aviation. In the general aviation, the flight simulator contributes to decrease pilot training costs and keep safety the aviation. In the case of traditional industries such as Embraer, Boeing and Airbus, and beyond that, the FS avoid delays and decrease the costs in development of new aircraft. Thus, the aeronautical industry has invested hardly on modeling and simulation (M&S). The objective of this paper is to describe the process of updating the latero-directional aerodynamic coefficients from aerodynamic model of the FS using flight test data in order to establish a model in according with aviation rules. This process is called as aerodynamic matching, and has presented very satisfactory results in aeronautical industry. The methodology used and proposed here is one more tool to model with precision the flight dynamics of airplanes.

© 2017 American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This work presents a proposed framework intended to be used for the optimization of highlift devices, namely Flaps and Slats for the present study. From the conceptual design up to flight test, as fidelity and design maturity increases, a robust and yet fast tool is needed to assist engineers to optimize and make better decisions regarding Flap and Slat deflection definitions in order to satisfy the multitude of design challenges such as take-off performance, climb performance, landing performance, deployment times, kinematics, icing effects, failures, only to name a few. Without such a tool or framework, one can be easily overwhelmed and the best solution or trade-offs cans be lost or obliterated by the huge amounts of possibilities, constraints and design goals. The proposed framework can used with multiple fidelity data such as physics based models, CFD models and semi-empirical ones, in order to accomadate the learning curve that exists under any product development timeline. For an initial approach, the takeoff performance calculation is conducted using statistical models constructed from wind tunnel test data and then optimized, having as main design goal the maximization of the MTOW for a certain runway and having 2nd segment gradient as main constraint. Other constraints can and will be added as needed, in order to assist in a robust decision. Once the framework is set, a multitude of design studies can be done, including design robustness, sensitiveness, design changes and many others. Not only a direct result in airplane performance is expected, but also an expressive reduction in development cycle times from conceptual design to flight test, since the framework will hugely speed up the design process.

© 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.A distinct wavy leading edge performance for finite wings can be expected in comparison to the infinite wing, due to the differences in geometry and flow conditions. An infinite span wing, unlike a partial span model, has a unique local Reynolds number, sweep angle, thickness and camber. In addition, it is not subjected to the wing tip phenomenon which changes the pressure coefficient along span, and, as consequence, the adverse pressure gradients. These differences on the flow over finite and infinite span geometries cause differences in tubercle performance, which have motivated some works, in order to investigate the influence of flow three-dimensionality on wavy leading edge performance. However, there are lack of works that evaluate the effects of the wing’s three-dimensional on flow topology of the wavy leading edge and their consequences in performance. The aim of this study is to investigate the effects of the wing’s three-dimensional flow on wavy leading edge phenomena at low Reynolds number. Experimental investigations were carried-out modifying geometric parameters of the wing planform (taper ratio and sweep) in order to understand the effects of these parameters on wavy leading edge phenomena. The tests are conducted for pairs of models with and without tubercles. A pair of two-dimensional models (NACA 0020) and four pairs of finite-wing models with taper ratios of 0.5 and 1, and sweep angles of 0º and 30º were tested. The experimental investigation was based on evaluation of force measurements (lift and drag) and flow visualizations (oil and mini-tufts). Additionally, the Reynolds number effects were also investigated by evaluating the wavy leading edge characteristics at Reynolds number 80,000 and 200,000.

© 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.After a previous work showing the aerodynamic longitudinal coefficients modeling, the authors continue to present the techniques to obtain the aircraft coefficients and how to structure them in an aerodynamic model but now with focus on the lateral-directional coefficients. Thus, the aim of this work is to present appropriated methodologies available used to calculate and model aerodynamic lateral-directional coefficients in the distinct phases of the aircraft design, mainly in the Conceptual and Preliminary Phases. In addition, the main recommended practices and general structure of the aerodynamic model are described in order to satisfy the requirements of different technologies during design cycles, such as Loads and Flight Dynamics. The procedures to obtain lateral-directional aerodynamic coefficients and derivatives from wind tunnel tests, theoretical and empirical methods are also presented here. The methodologies and techniques described in this work are available in public domain. The methodologies approaches described achieve a specific model complexity level and accuracy that depends on the aircraft design phase, staff expertise, company experience and design budgets. Apart from the methodology approach the understanding of the best practices and methodologies regarding aerodynamic modeling is essential to achieve success in the aircraft design. Thus, this work brings a contribution in the sense to present appropriated procedures to develop aerodynamic models under design constraints.

© 2017 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.The interest in studying the aerodynamic performance of airfoils at low Reynolds number has been increasing recently. There are many applications for airfoil design at low Reynolds number as design point. These applications include sailplanes, propellers, unmanned aerial vehicles (UAVs) and micro air vehicles (MAVs). However, there are few works evaluating the thickness effect as a design parameter for airfoil performance at low Reynolds number regime as well as data from flow visualizations in order to clarify the aerodynamic phenomena regarding thickness variation. In this sense, the aim of this work is to investigate the thickness effect on flow characteristics and performance of symmetrical airfoils at low Reynolds number regime by experimental investigation correlating force measurements with mini-tuft and oil flow visualization data. In an overall view, this work intends to contribute for investigations of desirable flow and geometric conditions of airfoils applied in UAV and MAV designs. Experimental tests were carried out at subsonic blower-type wind tunnel of open loop with closed section at ITA (Technological Institute of Aeronautics). A set of three symmetrical airfoils with different thickness (NACA 0012, NACA 0020 and NACA 0030) were tested at Reynolds number regime between 50,000 and 290,000. The results show distinct thickness effect for Reynolds number condition borders where at Re = 50,000 the thickest airfoil causes full flow separation with a great aerodynamic deterioration. In contrast, at Re = 290,000 the thickest airfoil achieves the highest maximum lift value.

© 2017 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.The aim of this work is to investigate the wavy leading edge phenomena for the very thick airfoil NACA 0030 by experimental investigation correlating force measurements with mini-tuft and oil flow visualization data at low Reynolds number regime. Experimental tests were carried out at subsonic blower-type wind tunnel of open loop with closed section at ITA (Technological Institute of Aeronautics). A set of four very thick airfoils were tested composed by one smooth configuration and three wavy leading-edge configurations (A= 0.03c, λ = 0.40c; A= 0.03c, λ = 0.11c; A= 0.11c, λ = 0.40c). The wavy leading edge geometry variation and Reynolds number effects were evaluated at range of Reynolds number between 50,000 and 290,000. For the highest Reynolds number condition, the results show worse aerodynamic performance for wavy leading edge when compared to previous studies of thinner airfoils. However, at Reynolds number 120.000, the configuration with A= 0.03c and λ = 0.11c presents a unprecedented result on literature overcoming the baseline maximum lift coefficient in 19,4% and the stall angle in 44%. In addition, the flow visualization results indicate that the leading edge stall characteristics at airfoils lead the tubercle configurations for better aerodynamic performance.

© 2017 by the American Institute of Aeronautics and Astronautics, Inc.The aircraft design cycle is a complex process that involves various design phases with different levels of maturity always driven by market requirements and certification. These requirements involve disciplines such as performance, flight mechanics, environmental comfort, emissions and maintenance. However, for most aircraft designs, the requirements that define initially the aircraft lofting and are mandatory during the design cycle are related to aircraft performance since what sells the aircraft is its performance. Thus, an accurate drag polar prediction during the aircraft design phases guarantees the success of the design by a decrease in risks of do not accomplish performance requirements. In the past, certain aircraft designs achieved drag prediction errors of 10 to 20% showing outwith the range needed for success. Therefore, the aeronautical companies have been pursuing accurate drag polar prediction methodologies putting many efforts in semi-empirical formulation implementations, CFD simulations and wind tunnel campaigns in order to achieve minimum errors in predicting the drag polars before the first flight keeping errors at least below 10%. The aim of this work is to present in detail the distinct drag polar prediction methodologies applied during the design aircraft phases in the aeronautical industry as well as establish requirements that guarantee a minimum drag polar prediction errors pursuing at least values below 10% where an accurate prediction methodology could be considered achieving errors around 5%. Semi-empirical methods, numerical simulations (CFD) and wind tunnel test procedures applied during conceptual design and preliminary phase are described. In addition, processes proposed for updating the drag polar formulation before the first flight are suggested what could represent an improve in accuracy for drag polar prediction methodology in the future design cycles. This work also intend to reinforce the methodologies available and open opportunity to start discussions for new approaches regarding the drag polar prediction during design cycle such as increase in numerical simulation (CFD) and in using simulation model even in early phases in order to obtain accurate drag polars.

© 2016 American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This paper presents a new approach on aircraft design education based on LPD principles in order to expand knowledge generation and communication during early aircraft design phase, and as a consequence support the emergence of innovative, efficient design solutions as well as provide wide knowledge on aircraft design problematization. The benefits of working with set-based and visible knowledge in a new process framework are evidenced in a case study of early aircraft design at PEE (Embraer Engineering Specialization Program), an environment of aeronautical industry simulation focused on the capacitation of young engineers.

© 2016, American Institute of Aeronautics and Astronautics Inc, AIAA . All rights reserved.Considering the lack of studies in airfoil geometry effect on tubercle performance and in order to contribute to research in this topic by expanding the investigation of the flow characteristics and aerodynamic performance for distinct airfoils, the aim of this paper is to investigate the effect of the airfoil thickness variation in the wavy leading edge phenomenon by experimental investigation correlating force measurements with mini-tuft and oil flow visualization at low Reynolds number regime. Besides, the Reynolds number effect will be evaluated in the sensitive range between 50.000 and 290.000. Experimental tests were carried out at subsonic blower-type wind tunnel of open loop with closed section at ITA (Technological Institute of Aeronautics). Two different sets of airfoils with distinct thickness (NACA 0012 and NACA 0020) were tested where each set contents a smooth leading-edge configuration and three wavy leading-edge configurations. The results show that the increase in airfoil thickness causes aerodynamic deterioration at pre-stall regime for wavy leading edge airfoil. In addition, the data show that the Reynolds number effect is sensitive on wavy airfoil performance where in some cases at lowest Reynolds number the wavy leading edge configuration achieves maximum lift higher than smooth configuration.

© 2016 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.The objectives of this work is to show appropriated available methodologies used to calculate and modeling aerodynamic coefficients in the distinct aircraft design phases, mainly the Conceptual and Preliminary Phases, as well as present the main recommended practices and general structure of the aerodynamic model to attend the requirements of different technologies during design cycles, such as Loads and Flight Dynamics. This work shows how to get longitudinal aerodynamic coefficients and derivatives from wind tunnel tests, theoretical and empirical methods. The whole approach of this paper will focus on methodologies and techniques that are in public domain. Another important concern of this paper is to make clear that the use of each methodology regards complexity and accuracy is dependent on the aircraft design phase, staff expertise, company experience and design budget. However, understanding the best practices of the aerodynamic modeling is essential to achieve success in the aircraft design. Thus, this work brings a contribution in the sense to show appropriated methodology options under design constraints, starting with the general arrangement concept of an Aerodynamic Model as a part of the Aircraft Simulation Model.

© 2016 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.The Flight Simulator (FS) is a key aspect of the traditional aeronautical industry and the general aviation. In the general aviation, the flight simulator contributes to decrease pilot training costs and keep safety the aviation. In the case of traditional industries such as Embraer, Boeing and Airbus, and beyond that, the FS avoid delays and decrease the costs in development of new aircraft. Thus, the aeronautical industry has invested hardly on modeling and simulation (M&S). The objective of this paper is to describe the process of updating the longitudinal aerodynamic coefficients from aerodynamic model of the FS using flight test data in order to establish a model in according with aviation rules. This process is called as aerodynamic matching, and has presented very satisfactory results in aeronautical industry. The methodology used and proposed here is one more tool to model with precision the flight dynamics of airplanes.

© 2015 by the American Institute of Aeronautics and Astronautics, Inc.Aircraft landing-gear noise has been recognized in recent years to be one of the major sources for the overall aircraft noise, noticeably, during the approach flight phase. The importance of investigating landing-gear noise is further justified by the incorporation of more stringent noise regulations by regulating authorities and due to the current trend recorded by aircraft manufacturers to design super-sized aircraft such as the Airbus A380. In this context, the Brazilian SILENT AIRCRAFT PROJECT is related to an innovative program to improve science and aerospace technology in the country, which was established between university (University of São Paulo) and industry (EMBRAER). It focuses on investigation and development of solutions to minimize external noise in new aircraft configurations. The present work is part of the before mentioned project and it has the objective to achieve significant noise reduction levels for the G550 Nose Landing Gear (NLG). This should be performed with numerical tools and the project also intends to provide guidelines towards the design of new aircraft programs. The investigation approach for noise reduction is established by the analysis of noise dominant sources of the G550 NLG (breakdown analysis) and by evaluating some proposed solutions to minimize the referred noise (noise minimization devices studies) as well. Higher intensity acoustic contributors for some landing gear components are identified and sorted out according to their power. Rub caps, ramps and fairings are proposed to minimize noise for the NLG components. Fairings to cover upper and lower torque arm and axle, and unconventional configuration (door as ramp function) appear as solution to decrease noise remarkably. The simulation tool used in this work is the Exa PowerFLOW, a lattice Boltzmann unsteady fluid flow solver commercially available.

© 2015, American Institute of Aeronautics and Astronautics Inc, AIAA. All rigths reserved.From the beginning of aviation designers are searching for methods and technologies for reducing the required fuel burn of commercial aircraft. Wingtip devices in special winglets offer a way of significative drag reduction for transport airplanes. Winglet alongside with tip tanks, raked wingtips, aligned fans belong to this class of wingtip devices. Although winglets are targeted to induced drag reduction their effects can be extended to wave and zero-lift drag as well. Induced drag alone is responsible for 30-40% of the overall drag of a transport airplane at long-range cruise condition and for considerably downgrading the climb performance of fixed-wing aircraft. Better investigation in this field employing CFD tools and extensive wind-tunnel testing has allowed the rising of efficient winglet designs in recent times. Several of newly designed aircraft configurations embody winglets and many older ones are being retrofitted. However, there are discussions concerning the best cost/benefit of reducing induced drag of a transport plane with wingtip devices. Another big issue is the associated penalties to the configuration caused by winglets when compared to a simple wingtip extension. This paper addresses some of these issues based on the expertise obtained designing winglets for several airplane configurations, ranging from a business jet and a twinjet airliner for 70 passengers to an AEW&C military airplane.