Abstract: Hat-stringer-stiffened composite panels have been widely used in aircrafts. Accurate failure analysis of them is important for the safety and integrity of the fuselage. During the service period, these panels will bear not only the lateral force caused by the bending of fuselage, but also the radial pressure caused by the internal and external differential pressure during the take-off and landing of the aircraft. However, the latter case lacks investigation. Therefore, experimental and numerical studies for the static and fatigue failure of hat-stringer-stiffened composite panels under four-point bending loading have been performed in this work. To accurately predict the fatigue failure, a novel theoretical model has been proposed based on the fatigue damage theory. In addition, a user-defined subroutine USDFLD is developed for the implementation of the proposed theoretical model in Abaqus. Experimental results show that the main failure modes are the delamination of the skin and debonding between the girder flange and the skin. The experimental average value of the initial debonding load and displacement in static tests are 897.3 N and 10.8 mm, respectively. Predictions exhibit good agreement with experimental results with relative errors within 10%. Experimental average fatigue failure life of the specimens is 33,085 cycles, which is also close to the prediction with relative errors within 10%. This indicates the reliability and applicability of the established theoretical model and numerical method for predicting the failure of hat-shaped girder structures.

Abstract: This paper investigates the acoustics of a one-passenger and a six-passenger quadrotor urban air mobility (UAM) aircraft in level flight based on a high-fidelity computational fluid dynamics (CFD) approach. The CFD simulations are carried out using the HPCMP CREATE TM -AV multidisciplinary rotorcraft analysis and simulation tool Helios. The acoustic simulations are performed using the acoustic prediction tool PSU-WOPWOP. A total of three CFD models are simulated: a onepassenger isolated rotor configuration, a one-passenger full configuration with a fuselage, and a six-passenger isolated rotor configuration. The noise comparison between the one-passenger isolated rotor case and the full configuration case shows that the vehicle fuselage increases the A-weighted sound pressure level (SPL) up to 5 dB. The acoustic comparison between the one-passenger and the six-passenger isolated rotor configuration shows that the maximum overall SPL difference is up to 14 dB. Furthermore, it is shown that the noise of the six-passenger configuration is approximately 11 dB lower than that of a similar-sized conventional helicopter in an overhead scenario. The community noise impact of UAM aircraft is also assessed and compared to various background noise levels. The results show that the one-passenger quadrotor noise can be fully masked by freeway noise at an altitude greater than or equal to 1000 ft, while the six-passenger quadrotor noise can only be partially masked by freeway noise even at an altitude of 1000 ft.

Abstract: Zero-carbon-dioxide-emitting hydrogen-powered aircraft have, in recent decades, come back on the stage as promising protagonists in the fight against global warming. The main cause for the reduced performance of liquid hydrogen aircraft lays in the fuel storage, which demands the use of voluminous and heavy tanks. Literature on the topic shows that the optimal fuel storage solution depends on the aircraft range category, but most studies disagree on which solution is optimal for each category. The objective of this research was to identify and compare possible solutions to the integration of the hydrogen fuel containment system on regional, short/medium- and large passenger aircraft, and to understand why and how the optimal tank integration strategy depends on the aircraft category. This objective was pursued by creating a design and analysis framework for CS-25 aircraft capable of appreciating the effects that different combinations of tank structure, fuselage diameter, tank layout, shape, venting pressure and pressure control generate at aircraft level. Despite that no large differences among categories were found, the following main observations were made: (1) using an integral tank structure was found to be increasingly more beneficial with increasing aircraft range/size. (2) The use of a forward tank in combination with the aft one appeared to be always beneficial in terms of energy consumption. (3) The increase in fuselage diameter is detrimental, especially when an extra aisle is not required and a double-deck cabin is not feasible. (4) Direct venting has, when done efficiently, a small positive effect. (5) The optimal venting pressure varies with the aircraft configuration, performance, and mission. The impact on performance from sizing the tank for missions longer than the harmonic one was also quantified.

Abstract: Surface defect identification is a crucial task in many manufacturing systems, including automotive, aircraft, and steel rolling. Although image-based surface defect identification methods have been proposed, these methods usually have two limitations: images may lose partial information, such as depths of surface defects; and their precision is vulnerable to many factors, such as the inspection angle, light, color, noise, etc. Given that three dimensional (3D) point cloud can precisely represent the multi-dimensional structure of surface defects, we aim to detect and classify surface defects using 3D point cloud. This has two major challenges: (i) the defects are often sparsely distributed over the surface, which makes their features prone to be hidden by the normal surface; (ii) different permutations and transformations of 3D point cloud may represent the same surface, so the proposed model needs to be permutation and transformation invariant. In this paper, a two-step surface defect identification approach is developed to investigate the defects' patterns in 3D point cloud data. The proposed approach consists of an unsupervised method for defect detection and a multi-view deep learning model for defect classification, which can keep track of the features from both defective and non-defective regions. We prove that the proposed approach is invariant to different permutations and transformations. A case study is conducted for defect identification in the aircraft fuselage. The results show that our approach receives the best defect detection and classification accuracy compared with other benchmark methods.

Abstract: This paper presents the design calculations, implementations, and multi-engineering based computational constructions of an unmanned amphibious vehicle (UAmV) which efficiently travels underwater to detect and collect deep-sea minerals for investigations, as well as creative usage purposes. The UAmV is expected to operate at a 300 m depth from the water surface. The UAmV is deployed above the water surface near to the approximate target location and swims underwater, checking the presence of various mining, then extracts them using a unique mechanism and stores them in an inimitable fuselage location. Since this proposed UAmV survives in deep-sea regions, the design construction of this UAmV is inspired by hydrodynamic efficient design-based fish, i.e., Rhinaancylostoma. Additionally, standard analytical approaches are followed and, subsequently, the inimitable components such as wing, stabilizers, propellers, and mining storage focused fuselage are calculated. The computational analyses such as hydrodynamic investigations and vibrational investigations were carried out with the help of ANSYS Workbench. The hydrodynamic pressures at various deployment regions were estimated and thereafter the vibrational outcomes of UAmVs were captured for various lightweight materials. The computed outcomes were imposed in the analytical approach and thereby the electrical energy generations by the UAmV’s components were calculated. Finally, the hydrodynamic efficient design and best material were picked, which provided a path to further works on the execution of the focused mission. Based on the low drag generating design profile and high electrical energy induction factors, the optimizations were executed on this work, and thus the needful, as well as suitable UAmV, was finalized for targeted real-time applications.

Abstract: The key problem in the development process of a tiltrotor is its mathematical modeling. Regarding that, this paper proposes a dividing modeling method which divides a tiltrotor into five parts (rotor, wing, fuselage, horizontal tail, and vertical fin) and to develop aerodynamic models for each of them. In that way, force and moment generated by each part are obtained. Then by blade element theory, we develop the rotor’s dynamic model and rotor flapping angle expression; by mature lifting line theory, the build dynamic models of the wings, fuselage, horizontal tail and vertical fin and the rotors’ dynamic interference on wings, as well as nacelle tilt’s variation against center of gravity and moment of inertia, are taken into account. In MATLAB/Simulink simulation environment, a non-linear tiltrotor simulation model is built, Trim command is applied to trim the tiltrotor, and the XV-15 tiltrotor is taken as an example to validate rationality of the model developed. In the end, the non-linear simulation model is linearized to obtain a state-space matrix, and thus the stability analysis of the tiltrotor is performed.

Abstract: This paper presents an aircraft configuration trade space exploration for NASA’s SUbsonic Single Aft eNgine (SUSAN) Electrofan, which is a 180 passenger regional class transport aircraft that utilizes electrified aircraft propulsion and advanced propulsion airframe integration technologies to enable reduced fuel consumption and emissions. At its core is a hydrocarbon fuel-consuming aft fuselage propulsor that produces 35% of the total thrust while generating power to drive wing-mounted electric propulsors, which produce the remaining 65% thrust. This power is extracted from the aft fuselage propulsor via a set of generators and is managed with the help of a rechargeable battery, classifying the propulsion system as hybrid electric. Investigated in this work are different aft fuselage propulsor concepts, several wing propulsor configurations, and different types of stability and control strategies that can be accommodated by this hybrid electric system architecture, with an emphasis on aircraft performance. Results obtained using a low-order multidisciplinary design and analysis framework demonstrate that even with a subset of the advanced technologies that are being considered for the SUSAN Electrofan, significant improvements to fuel efficiency can be achieved.

Abstract: Guided waves-based SHM systems are of interest in the aeronautic sector due to their lightweight, long interrogation distances, and low power consumption. In this study, a bottom-up framework for the estimation of the initial investment cost (COTC) and the added weight (WAW) associated with the integration of a SHM system to an aircraft is presented. The framework provides a detailed breakdown of the activities and their costs for the sensorization of a structure using a fully wired approach or the adoption of the printed diagnostic film. Additionally, the framework considers the difference between configuring the system for Manual or Remote data acquisition. Based on the case study presented on the sensorization of a regional aircraft composite fuselage, there is a trade-off between COTC and WAW for the SHM options considered. The Wired–Manual case leads to the lowest COTC with the highest WAW, while the combination of diagnostic film with a Remote system leads to the highest COTC and the lowest WAW. These estimations capture the characteristics of each system and can be integrated into cost–benefit analyses for the final selection of a particular configuration.

Abstract: This paper presents the development of a novel polymorphing wing capable of Active Span morphing And Passive Pitching (ASAPP) for small UAVs. The span of an ASAPP wing can be actively extended by up to 25% to enhance aerodynamic efficiency, whilst its pitch near the wingtip can be passively adjusted to alleviate gust loads. To integrate these two morphing mechanisms into one single wing design, each side of the wing is split into two segments (e.g., inboard and outboard segments). The inboard segment is used for span extension whilst the outboard segment is used for passive pitch. The inboard segment consists of a main spar that can translate in the spanwise direction. Flexible skin is used to cover the inboard segment and maintain its aerodynamic shape. The skin transfers the aerodynamic loads to the main spar through a number of ribs that can slide on the main spar through linear plain bearings. A linear actuator located within the fuselage is used for span morphing. The inboard and outboard segments are connected by an overlapping spar surrounded by a torsional spring. The overlapping spar is located ahead of the aerodynamic center of the outboard segment to facilitate passive pitch. The aero-structural design, analysis, and sizing of the ASAPP wing are detailed here. The study shows that the ASAPP wing can be superior to the baseline wing (without morphing) in terms of aerodynamic efficiency, especially when the deformation of the flexible skin is minimal. Moreover, the passive pitching near the wingtip can reduce the root loads significantly, minimizing the weight penalty usually associated with morphing.

Abstract: The truss-braced-wing (TBW) aircraft is a promising innovative design for the next-generation airliner. Nevertheless, for a full TBW wing–body–tail configuration, it is still a challenge to perform the comprehensive refined aerodynamic design. Especially, the complex mutual interference among the wing, struts, and fuselage should be analyzed in detail. Meanwhile, for its one-design cruise condition with and , the aerodynamic explorations and performances of drag divergence and near-buffet-onset condition are also fateful. To address these issues, we utilize high-fidelity Reynolds-averaged Navier–Stokes solver and gradient-based optimizer to conduct aerodynamic optimization designs, including a single-point optimization, a two-point optimization, and a three-point optimization. Results indicate that the single-point design obtains a nearly shock-free configuration with an approximate elliptical lift distribution and an of 24.09. Also, the refined local aerodynamic analyses lead to a good understanding of the complicated interactions with several junctions. For multipoint optimizations, both optimized configurations have the same level aerodynamic behavior on cruise condition compared with the single-point result, and they have a satisfying performance of drag divergence. Moreover, the three-point optimization design shows excellent aerodynamic efficiency with some extra off-design points evaluations, whereas the two-point optimization still has an undesirable off-design result.

Abstract: The inverse problem of determining how to shot peen a plate such that it deforms into the desired target shape is a challenge in the peen forming industry. While peening thick plates uniformly on one side results in a spherical shape, with the same curvature in all directions, complex peening patterns are required to form other shapes, such as cylinders and saddles found on fuselages and wing skin panels. In this study, we present an optimization procedure to automatically compute shot peening patterns. This procedure relies on an idealized model of the peen forming process, where the effect of the treatment is modeled by in-plane expansion of the peened areas, and on an off-the-shelf optimization algorithm. For validation purposes, we peen formed three 305 × 305 × 4.9 mm and two 762 × 762 × 4.9 mm 2024–T3 aluminium alloy plates into cylindrical and saddle shapes using the same peening treatment. The obtained shapes qualitatively match simulations. For 305 × 305 × 4.9 mm plates, the relative differences had the same distribution and were of the same order of magnitude as initial out-of-plane deviations measured on the as-received plates.

Abstract: We investigate the error scaling and computational cost of wall-modeled large-eddy simulation (WMLES) for external aerodynamic applications. The NASA Juncture Flow is used as representative of an aircraft with trailing-edge smooth-body separation. Two gridding strategies are examined: 1) constant-size grid, in which the near-wall grid size has a constant value and 2) boundary-layer-conforming grid (BL-conforming grid), in which the grid size varies to accommodate the growth of the boundary-layer thickness. Our results are accompanied by a theoretical analysis of the cost and expected error scaling for the mean pressure coefficient and mean velocity profiles. The prediction of is within less than 5% error for all the grids studied, even when the boundary layers are marginally resolved. The high accuracy in the prediction of is attributed to the outer-layer nature of the mean pressure in attached flows. The errors in the predicted mean velocity profiles exhibit a large variability depending on the location considered, namely, fuselage, wing-body juncture, or separated trailing edge. WMLES performs as expected in regions where the flow resembles a zero-pressure-gradient turbulent boundary layer such as the fuselage ( error). However, there is a decline in accuracy of WMLES predictions of mean velocities in the vicinity of wing-body junctions and, more acutely, in separated zones. The impact of the propagation of errors from the underresolved wing leading edge is also investigated. It is shown that BL-conforming grids enable a higher accuracy in wing-body junctions and separated regions due to the more effective distribution of grid points, which in turn diminishes the streamwise propagation of errors.

Abstract: The aircraft fuel tank, as the source of fuel supply, is one of the key components for an aircraft. It is fastened to the fuselage with thousands of rivets, in which each rivet is sealed carefully to prevent the leakage. Thus, the sealing quality of the aircraft fuel tank needs to be precisely measured to ensure its normal function. To achieve the measurement, the complete 3D point clouds captured by 3D scanning are usually utilized. Therefore, it is necessary to align the different views of the aircraft fuel tank point clouds, to obtain the complete data. However, the aircraft fuel tank consists of abundant repetitive structures, such as the regular-distributed rivets, which can lead to mismatches in the aircraft fuel tank point clouds if using the conventional registration methods. In order to address the challenges, we propose a new registration framework, which is able to handle the point cloud match under the repetitive and complex scenes. First, a novel 3D descriptor called LP-PPF is constructed with the point and line features from the aircraft fuel tank point clouds, so as to identify the repetitive structures correctly. Then, according to the proposed descriptor, the accurate registration can be achieved between the neighboring point cloud pairs. Finally, based on the results of pairwise registration, the complete aircraft fuel tank point cloud can be obtained via the multi-view registration method. Experiments demonstrate that our method achieves favorable results on both synthetic and raw scanned point cloud data.

Abstract: The present paper deals with the investigation, at conceptual level, of the performance of short–medium-range aircraft with hydrogen propulsion. The attention is focused on the relationship between figures of merit related to transport capability, such as passenger capacity and flight range, and the parameters which drive the design of liquid hydrogen tanks and their integration with a given aircraft geometry. The reference aircraft chosen for such purpose is a box-wing short–medium-range airplane, the object of study within a previous European research project called PARSIFAL, capable of cutting the fuel consumption per passenger-kilometre up to 22%. By adopting a retrofitting approach, non-integral pressure vessels are sized to fit into the fuselage of the reference aircraft, under the assumption that the main aerodynamic, flight mechanic, and structural characteristics are not affected. A parametric model is introduced to generate a wide variety of fuselage-tank cross-section layouts, from a single tank with the maximum diameter compatible with a catwalk corridor to multiple tanks located in the cargo deck, and an assessment workflow is implemented to perform the structural sizing of the tanks and analyse their thermodynamic behaviour during the mission. This latter is simulated with a time-marching approach that couples the fuel request from engines with the thermodynamics of the hydrogen in the tanks, which is constantly subject to evaporation and, depending on the internal pressure, vented-out in gas form. Each model is presented in detail in the paper and results are provided through sensitivity analyses to both the technologic parameters of the tanks and the geometric parameters influencing their integration. The guidelines resulting from the analyses indicate that light materials, such as the aluminium alloy AA2219 for tanks’ structures and polystyrene foam for the insulation, should be selected. Preferred values are also indicted for the aspect ratios of the vessel components, i.e., central tube and endcaps, as well as suggestions for the integration layout to be adopted depending on the desired trade-off between passenger capacity, as for the case of multiple tanks in the cargo deck, and achievable flight ranges, as for the single tank in the section.

Abstract: Accurate perception of flight parameters is essential for the safe and stable flight of small unmanned aerial systems (SUASs). However, traditional flush air data sensing (FADS) systems require complex tubing and fuselage openings. Herein this study, a flexible skin system integrated with a pressure and thermal flow sensor array, and a dual‐sensor fusion algorithm for determining the angle of attack (AOA) and airspeed (V ∞ ), are proposed. By establishing an error back‐propagation neural network, the dual‐sensor fusion modality demonstrates higher estimation accuracy than other modalities that utilize only pressure data or only flow velocity data, achieving mean absolute errors of the AOA and V ∞ of less than 0.16° and 0.37 ms−1, respectively. Moreover, the simulation and experimental results show that sensors placed closer to the leading edge of the wing can provide higher estimation accuracy of the flight parameters. The flight parameters determined using the flexible air data sensing system and dual‐sensor fusion algorithm demonstrate potential application in the flight control of SUASs.

Abstract: An integrated modeling approach is presented for the conceptual design of electric aircraft propulsors, with application to NASA’s hydrogen fuel-cell powered transport aircraft concept, being developed under the CHEETA (Center for High-Efficiency Electrical Technologies for Aircraft) program. The distributed boundary layer ingesting (BLI) fan module and the fan-hub embedded MgB2 based fully superconducting (SC) electric motors are modeled together using Signomial Programming (SP). An all-at-once SP optimization eliminates external design iterations between modules and provides sensitivities to design parameters as part of the optimization solution. In addition, the approach developed here is modular and component models can be easily added to study various aircraft architectures. A trade space exploration of CHEETA propulsors indicates a highly-distributed 32 wing and fuselage mounted propulsors configuration, powered by 0.5 MW and 1.6 MW motors, respectively, as the optimal, yielding 16% reduction in the aircraft electric energy consumption relative to a conventional twin electric under-wing propulsors design. However, the design selected is a 9 propulsors configuration with 2.4 MW motors (power range more suitable for fully SC architecture), with about 14% power savings. The fan-embedded motor architecture leads to fan hub-to-tip ratios of up to 0.5, which are higher than typical.

Abstract: The fuselage structure is one of the important subassemblies of an airplane. It is used to house the passengers, baggage and cargo and subjected to many loads in the flight and during the ground roll. The significance of this research paper is to compare the stresses induced in the fuselage under various flight and loading conditions. The structural analysis is carried out for two different materials that is Aluminium, Al-7075 and Titanium alloys. The deformation of the fuselage structure at the various loading conditions and for different materials is analysed using ANSYS-Static Structural, and the Modelling of the fuselage structure is performed by using CREO 4.0. The stresses induced in the aluminium fuselage are more than that developed in the titanium alloy fuselage. The deformation at different places of the aluminium fuselage structure is also more than the titanium alloy fuselage.

Abstract: Flow control methods for aerodynamic drag reduction have been a field of interest to aircraft designers, who seek to minimize fuel consumption and increase the aircraft’s aerodynamic performance. Various flow control techniques, applied to aeronautical applications ranging from large airliners to small hand-launched unmanned aerial vehicles (UAVs), have been conceptualized, designed and tested in the past. Among others, the concept of riblets, inspired by the shark’s skin morphology, has been proposed and evaluated for airliners. In this work, the implementation of riblets on a medium-altitude long-endurance UAV (MALE) is investigated. The riblets can offer drag reduction due to the decrease in total skin friction, by altering the boundary layer characteristics in the near-wall region. The riblets are implemented on specific locations on the UAV (main wing, fuselage and empennage) and appropriately selected, on which the boundary layer becomes transitional from the laminar to the turbulent flow regime. For this reason, computational fluid dynamics modelling is performed by solving the Reynolds-averaged Navier–Stokes equations, incorporating the k-ω SST eddy viscosity turbulence model. The effect of the riblets in the near-wall region is modelled with the use of an appropriate wall boundary condition for the specific turbulence dissipation rate transport equation. It is shown that a drag reduction benefit, for both the loiter and the cruise flight segments of the UAV mission, can be obtained, and this is clearly presented by the drag polar diagrams of the air vehicle. Finally, the potential benefit to flight performance in terms of endurance and payload weight increase is also evaluated.

Abstract: Existing research on the magnetic coupler of unmanned aerial vehicle (UAV) wireless charging systems usually ignores the UAV fuselage, but the fuselage causes eddy current loss and reduces a system’s efficiency. Therefore, aiming at the above problems, this paper proposes a design for a magnetic coupler using nanocrystalline cores to reduce the loss caused by the UAV fuselage. First, the parameters of the asymmetric circular coils were designed for higher mutual inductance. The losses caused by the windings and cores were also calculated. Second, for the loss effect of the carbon fiber fuselage, the fuselage was modeled as an additional coil coupled with both the transmitting and receiving coils. The fact that the eddy current induced by the fuselage leads to efficiency reduction is revealed, which has been generally ignored by previous research. Then, the effect of the nanocrystalline alloy was analyzed based on the magnetic circuit model. An optimized nanocrystalline alloy film was applied to reduce eddy current loss and improve coupler efficiency. Finally, an experimental prototype with a 500 W output, 90.3% efficiency, and a 300 mm air gap were fabricated. When compared to the design without UAV material considerations, the coupler efficiency was improved by 7.9%.

Abstract: Micro-Unmanned Air Vehicles (Micro-UAVs), especially quadrotor UAVs, have been widely used in recent years because of their simple structure and convenient operation. However, due to under-actuated and strongly-coupled characteristics, their flight performance is not perfect when suffering external uncertainty such as wind disturbance. Therefore, in this paper, the literature is reviewed related to wind acting on UAVs and makes some conclusions. First, we review the wind field model of quadrotor operation and decompose it into wind turbulent model, wind shear model, and other typical wind field models. Then we focus on the mathematic model of wind disturbance on UAVs and divide it into effect on rotors and effect on the fuselage. Finally, various control laws are used to study the wind resistance of quadrotors. We review the promising works which have been done before and determine the research emphasis to be focused on in the future.