Browse Topic: Aircraft structures
By tweaking the flap’s deflection angle, the flap rudder significantly enhances the hydrodynamic performance. This study investigates the influence of the location of the flap rotation axis and the size of the flap’s deflection affect how well the rudder performs in the water, using computer simulations to obtain high-resolution flow-field data. The results demonstrate that the flap rudder consistently generates more lift than your standard rudder. Prior to stall, pushing the flap rotation axis further back results in less lift, but also less drag. For maximum lift at small or moderate angles of attack, a rotation axis located at 0.75 c provides the highest lift coefficient, whereas the 0.85 c configuration combined with δ = 25° offers the best compromise between postponed stall and maintained lift-to-drag ratio. Put the pivot at 85% chord and set the flap deflection to 25 degrees, and an optimal configuration is achieved in terms of lift and drag. The configuration yields a stall
This SAE Aerospace Recommended Practice (ARP) recommends a methodology to be used for the design, analysis and test evaluation of modern helicopter gas turbine propulsion system stability and transient response characteristics. This methodology utilizes the computational power of modern digital computers to more thoroughly analyze, simulate and bench-test the helicopter engine/rotor system speed control loop over the flight envelope. This up-front work results in significantly less effort expended during flight test and delivers a more effective system into service. The methodology presented herein is recommended for modern digital electronic propulsion control systems and also for traditional analog and hydromechanical systems.
This SAE Aerospace Information Report (AIR) outlines a recommended procedure for evaluation of the vibration environment to which the gas turbine engine powerplant is subjected in the helicopter installation. This analysis of engine vibration is normally demonstrated on a one-time basis upon initial certification, or after a major modification, of an engine/helicopter configuration. This AIR deals with linear vibration as measured on the basic case structure of the engine and not, for example, torsional vibration in drive shafting or vibration of a component within the engine such as a compressor or turbine airfoil. In summary, this AIR discusses the engine manufacturer’s "Installation Test Code" aspects of engine vibration and proposes an appropriate measurement method.
This document provides recommendations involving BEV battery data retention and battery design that enhance the potential for BEV battery reuse and serviceability and that can improve recyclability. These recommendations have been developed by a group of professionals skilled in the secondary-use of batteries and in the research, development, and manufacture of BEV batteries and battery systems.
This SAE Aerospace Recommended Practice (ARP) establishes the overall component and system function guidelines and minimum performance levels for a TPMS. These guidelines include, but are not limited to: Design recommendations for system components, which: Monitor tire inflation Are located in/on the tire/wheel assembly, landing gear axle, and/or aircraft avionics compartment Recommended performance and safety guidelines for a TPMS.
We present a nonlinear topology optimization framework for designing crash--tolerant rotorcraft substructures by maximizing plastic work under prescribed crush displacement and volume constraints. The quasi-static response is modeled using a rate-independent elastoplastic formulation to capture path-dependent inelastic deformation of metallic components. A path-dependent adjoint method is developed to efficiently compute sensitivities of accumulated plastic work, revealing a mechanistic decomposition into elastic stiffness, deviatoric response, and yield surface contributions. Optimized 2D and 3D subfloor structures develop emergent plastic hinge networks and distributed deformation paths, significantly enhancing energy absorption compared to uniform designs. The results demonstrate that topology optimization can directly embed energy-dissipating mechanisms into primary rotorcraft structures, providing a practical framework for crashworthy rotorcraft and eVTOL airframe designs.
The validity of using comprehensive analysis (CA) tools coupled with computational fluid dynamics (CFD) to predict the aeromechanics of classical rotor blades was proven in the literature. This paper aims to enhance this validation for the complex double-swept planform ERATO blade under high-thrust level-flight condition. In order to do so, HOST comprehensive analysis tool and elsA/HOST high-fidelity loose coupling are compared to the results of the experimental campaign of the ERATO rotor carried out by ONERA in 1998 at the S1MA transonic wind tunnel. Trim commands and airloads are reviewed and enhanced with respect to a previous publication and structural loads (flap bending moment, chord bending moment and torsion moment) are used to validate the numerical simulations. The results highlight the need for high-fidelity methods in order to improve the accuracy of both the aerodynamic and structural responses.
The effects of hover operations near a partial boundary structure were assessed for a free-flying quadrotor platform under both wind-off and wind-on conditions. The partial boundary structure was selected to replicate a building facade or urban vertiport environment, providing a realistic operational context for these free-flight tests. Test points were chosen to investigate operations near the partial boundary wall and edge, and across a range of partial ground effect conditions to capture the progressive onset of ground effect characteristics. Regions of degraded vehicle performance, quantified primarily by rotor thrust coefficient (CT ) and power requirements, emerged near the partial boundary edge. These performance trends were attributed to localized changes in rotor inflow profile, characterized by near-field rotor pressure measurements. Partial ground effect was found to not resemble full ground effect until much of the vehicle had traversed over the partial boundary, with the
This paper utilizes a combined experimental and modeling approach to investigate techniques for improving the forward-flight roll-control authority of a Quadrotor Biplane Tailsitter (QBiT). QBiT is a mechanically simple, efficient hover/cruise aircraft whose roll authority in forward flight is traditionally limited by differential propeller-torque-based control. The two roll-control enhancement techniques investigated are propeller canting and the use of ailerons. A 2-kg instrumented QBiT platform was developed and flight tested to collect high-fidelity flight data across multiple flight regimes including hover, transition, cruise, and coordinated turns. A flight dynamics model was developed and validated using wind tunnel measurements and flight-test data. Flight tests showed that the cant-only configuration exhibited limited roll authority during coordinated turns due to motor control saturation, whereas the cant-plus-aileron configuration provided improved roll performance. Using
A method for evaluation of control derivatives is introduced for the purpose of rapid design evaluation of an electric, fixed-pitch multirotor aircraft during the conceptual pre-design phase. This explicit linearization methodology allows rapid co-design of the vehicle configuration and control allocation using the pseudo-inverse method. A multi-objective design analysis is conducted for a 12 rotor lift + cruise eVTOL configuration subject to hover power requirements, controllability, and tolerance to failure conditions. Generalizable design guidelines are found and presented for the cant and rotor spin direction of the lift + cruise aircraft. The benefits shown include the addition of direct lateral force control derivative, a major increase in yaw control derivative, and reconfiguration to accommodate any Two Engine Inoperative failure conditions. These are achieved through mixing anhedral and dihedral rotor cant within each quadrant of the wing, setting the spin direction so the
T-tail architectures show potential for enhancing vertical tail-efficiency and lowering fuselage download and hub load cycles during low-speed transition. However, a horizontal stabilizer is principally susceptible to rotor wake impingement during cruise flight, which, in unfavorable conditions, could induce dynamic loads along with associated vibrations and structural fatigue. Predicting this phenomenon is challenging due to the complex aerodynamics and sensitive structural dynamics involved. This paper demonstrates the capabilities of a mid-fidelity simulation methodology for predicting empennage structural loads and vibrations. The approach utilizes mid-fidelity interactional aerodynamics modeling, building upon previously published Vortex-Lattice Model (VLM) results and extending them to include a Viscous Vortex Particle Wake (VVPM) analysis, coupled with a modal structural dynamics model of the fuselage. The study extends the simulation model's validation against experimental data
This study presents a high-fidelity aeroelastic analysis for lift-offset coaxial rotors based on a three-dimensional (3D) finite element (FE) multibody dynamic analysis. The structural model is based on an updated Lagrangian formulation to capture geometrically nonlinear behavior. The internal aerodynamic model uses lifting line theory with linear inflow model, while the external aerodynamic model employs a panel/vortex particle method to predict aerodynamic loads. The lift-offset coaxial rotor developed by Korea Aerospace Research Institute is employed to investigate the aeroelastic response and the coupling analysis is performed on hover flight condition. The results obtained from the aeromechanics analysis using uniform inflow are compared with CAMRAD II in terms of blade displacement and sectional loads. Furthermore, through high-fidelity aeroelastic analysis using panel/vortex particle method, rotor–rotor aerodynamic interactions and structural loads, and 3D stress and strain
A Rotor Control Equivalent Turbulence Input (RCETI) model for characterizing vehicle response in urban environments turbulent airwakes is investigated. By extracting transfer functions from the nonlinear, high fidelity UH-60 rotorcraft model implemented within the FLIGHTLAB®framework, vehicle response to vertical turbulence is evaluated and inverse mapping between the rotor hub thrust coefficient and the control input spectrum is determined. Furthermore, the RCETI methodology develops filters that produce time history samples of collective input that produce hub loads that are stochastically similar to those induced by atmospheric air wakes.
Evaluating rotor component clearances is a multidisciplinary process aimed at ensuring that no contact occurs between rotor parts during a rotorcraft's operational life. It begins with calculating relative distances between components across all possible displacements and deformations combinations using a rotor kinematic model, and ends with clearance verification through flight data analysis and simulation. This task requires coupling detailed rotor aeroelasticity with flight mechanics to predict deformation under load, which is computationally expensive and unsuitable for real-time use. This work proposes a machine learning–based alternative: a neural network to estimate rotor clearances from flight mechanics inputs, with a specific application demonstrated in a simulated tiltrotor emergency maneuver with a pilot in the loop. The trained model successfully captures nonlinear relationships between maneuver parameters and rotor structural response, providing accurate predictions with
High speed compound rotorcraft may operate with slowed rotors, resulting in high advance ratios and aeroelastic instabilities. The classic Floquet approach to understanding this periodic system was expanded using a hybrid symbolic and computational method, incorporating coupled flap-lag-torsion degrees of freedom, reverse flow, unsteady aerodynamics, and a realistic trim routine bounded by thrust reversal and blade stall. A novel eigenvalue tracking algorithm and modal waveform analysis of the eigenvector motion was developed to generate and identify root loci, providing fundamental insights into parametric resonance and other instabilities. Advance ratios above 3 were explored, with parametric evaluations of both physical dynamic stability and numerical stability. The model's predictions were validated using historical analyses and experimental results, and recommendations regarding stable configurations are provided.
An advanced coupling framework was leveraged to assemble analytic sensitivities of lifting line theory aerodynamic loads with respect to externally-defined blade geometry parameters for optimization of main rotor performance of conventional helicopter configurations. Three vehicle weights and two flat-plate-equivalent drag configurations were examined across the flight envelope from hover to an advance ratio of 0.3. Two types of twist controls were investigated: quasi-static and fully active. Power savings were strongly correlated to the forward flight to hover power, ranging between 1.5 and 3.5% for quasi-static geometries and 2.0 and 4.5% for fully active controls when the installed power is twice of that required in hover. Blade twists optimized at higher power ratios were observed to favor high shaft tilt angles. Optimal twist deformation relative to hover-optimized designs is nonlinear across the blade span. Minimal penalties to aerodynamic vibrations were incurred through the use
A novel airfoil was designed at a Reynolds number (Re) of 50,000 using a multi-objective, multi-fidelity framework based on unsteady Reynolds-averaged Navier-Stokes (URANS) simulations and a gradient-free optimization approach, and compared with the DEA-11 airfoil. Aerodynamic performance and flow physics were investigated through water tunnel experiments, two-dimensional and three-dimensional URANS simulations, and microscopic particle image velocimetry (Micro-PIV), with numerical results validated against experimental data. At Re = 50,000, the optimized airfoil achieves approximately 60% drag reduction at matched lift coefficient, a reduced extent of flow separation, lower pitching moment, with comparable maximum lift coefficient relative to the DAE-11 baseline. In the three-dimensional setting, a classical aspect ratio correction recovers the finite-wing lift closely, while three-dimensional URANS consistently under-predicts drag at positive angles of attack. Measurements and
An aspect of the ship-helicopter dynamic interface (DI) is the highly unsteady flow environment generated by ship-rotor aerodynamic interactions, which challenges safe launch and recovery operations. To investigate these interactions without the constraints of conventional rotor scaling, a novel airflow-and-blade-frequency (ABF) system was developed, decoupling rotor thrust from blade-passing frequency and enabling independent control of disk loading and periodic excitation. Mean-flow superposition and spectral analyses were used to assess the validity of linear-superposition approaches for DI modeling. While superposition reproduced portions of the interacting mean flow, it failed to capture key features such as superstructure sheltering. Spectral results showed that momentum injection and blade-passing frequency modified the interacting flow through distinct mechanisms. Across all operating conditions, the interacting flow exhibited elevated turbulent kinetic energy at pilot-relevant
Stacked co-rotating rotors offer a mechanically simple alternative to conventional coaxial counter-rotating systems, but their aerodynamic performance is strongly dependent on both axial and azimuthal blade spacing. This study experimentally and numerically investigates the effects of rotor spacing on the performance and wake structure of model-scale stacked rotors in hover. A dedicated test platform was developed to measure thrust, power, and phase-resolved 2D-3C particle image velocimetry flow fields for two-bladed stacked rotors over axial spacings of Δz/c=0.75 to 5 and azimuthal spacings of ϕ = 0° and 90°. Relative to isolated two- and four-bladed baseline rotors, the stacked configurations exhibited measurable variations in total hub loading and induced flow structure as a function of spacing. The flow field results show that changes in axial spacing alter the relative position of the lower rotor within the convected wake of the upper rotor, producing corresponding changes in
In this study, a novel rotorcraft comprehensive analysis (CA) framework is constructed for the aeromechanics analysis of various rotorcraft configurations such as single main/tail rotors, coaxial rotors, and tilt rotors. The framework incorporates numerous solution procedures that include trim, blade response, loads, and vibration with external interfaces to computational fluid dynamics (CFD) analysis. The structural module is characterized by a displacement-based geometrically exact beam (GEB) model and multibody formulations while the internal aerodynamics module is developed using a lifting-line representation of blades with simple inflow models. A series of validation on static benchmark examples showed excellent correlations with published records, particularly in the context of large deformation behavior of heavily loaded beams. The rotorcraft aeromechanics analyses of various configuration rotors such as single main rotor and lift-offset coaxial rotor types are performed next to
Cold spray deposition is a kinetic-based deposition method that uses an inert gas flow to accelerate particles, where kinetic energy causes plastic deformation upon impact with a substrate, as discussed in Reference 1. Cold spray has been investigated as a method to deposit metal coatings on polymer-based composites, such as aerospace carbon-fiber-reinforced plastics (CFRP's), as discussed in Reference 2. These methods also exhibit low deposition efficiency (15-45%) as shown in Reference 3. In this work, to achieve high deposition efficiency and create an erosion-resistant coating, we use metal-polymer composite powders for cold spray, to make polymer-on-polymer bonding the dominant and effective bonding mechanism; this method lowers impact velocities relative to pure metal deposition to avoid substrate damage. The polymer can also lower the effect of material mismatch, while the nickel can help enhance the erosion performance of the final coating above that of pure polymer. This paper
The bird strike performance of rotorcraft components must be demonstrated to the airworthiness authority in accordance with the certification requirements of CS 29.631. This necessitates continuous efforts to design and validate birdstrike-resistant structures through a combination of experiments and simulations. In this study, an integrated experimental and numerical investigation is conducted to evaluate the structural response and failure characteristics of the main rotor pitch link subjected to bird impact. In the experimental program, high-speed imaging and strain measurements were used to capture the transient deformation and impact force history. In parallel, a highly nonlinear finite element model was developed using the LS-DYNA solver. The numerical model was validated against experimental results. Results demonstrate that localized plastic deformation and stress concentrations occur near the impact region, consistent with damage patterns observed in real-world incidents. This
This paper presents an analytical prediction of rotor blade–wake interaction (BWI) noise using a newly developed turbulence intensity model. The new model is developed using high-fidelity computational fluid dynamics (CFD) results and is validated against experimental data for a BO105 rotor, showing good agreement. Compared to the Glegg model, the proposed approach predicts sound pressure levels approximately 3 dB higher at 600 Hz and about 2 dB higher below 800 Hz, highlighting the contribution of turbulence outside the vortex core. Furthermore, high-fidelity CFD simulations of tip vortex impingement on a downstream wing are performed using Large Eddy Simulation (LES), fully turbulent Improved Delayed Detached Eddy Simulation (SST-IDDES), and Gamma Transitional IDDES (GT-IDDES). Both LES and GT-IDDES capture detailed unsteady and boundary layer transitional flow features, whereas SST-IDDES fails to capture transition and produces a RANS-dominated, time-averaged flow field. The swirl
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