Browse Topic: Airframes
The paper presents the successful drag reduction of the Racer demonstrator's rotor head through its innovative full fairing, based on a robust de-risking methodology leveraging 2D Robust Design Optimization (RDO) for airfoils, 3D CFD analysis with multiple fidelity levels, and experiments. We provide a unique end-to-end comparison across the full development cycle, correlating simulation predictions with both experimental and flight-test data. The fully faired architecture achieves a significant 42% reduction in rotor-hub form drag. At the full-vehicle level, flight tests confirm a 10% net drag reduction, including complex interactions with the airframe. This real-world measurement correlates highly with dynamic URANS predictions (11-12%), while effectively contextualizing the more optimistic 16% gains observed during static wind-tunnel and steady RANS evaluations. These findings provide a comprehensive validation of the low-drag fairing concept, offering valuable insights for 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
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
An internal layout design framework for a medium-class rotorcraft fuselage is attempted to build based on the idea of the energy-based load-transfer index. Load-transfer index will quantify the way in which the flight loads are distributed among the fuselage internal structural members. The static load-transfer analysis will identify an inefficient transfer region in the baseline fuselage configuration, and the resulting layout refinement will lead to a more unified load-transfer pattern and allow an additional weight reduction in the subsequent thickness-optimization stage. For a UH-60A aircraft, the existing literature provides well-established information for an airframe layout, finite-element modeling guideline, and ground vibration test correlation.
The Enhanced Tiltrotor blade, also known as the RGF3 blade, represents a major milestone in Leonardo Helicopters Division's pursuit of advanced rotorcraft technology. Developed at the Yeovil facility in the United Kingdom as part of a dedicated program and in collaboration with the European Clean Sky 2 initiative, it is a key enabler for the Next Generation Civil Tiltrotor Technology Demonstrator. Leveraging the AW609 airframe, the NGCTR integrates a new lateral rotor control system and a V-tail with ruddervators to expand maneuverability and control authority. The RGF3 blade combines aerodynamic efficiency with manufacturability, cost effectiveness, and certification readiness. Innovations include advanced airfoil families, highly swept anhedral tips, dual-redundant anti-ice systems, and full compatibility with legacy components. A comprehensive test campaign—covering structural loads, lightning and bird strikes, icing, and wind tunnel validation—confirmed its robustness and
The present study provides a detailed analysis of interactional aerodynamic effects present in the lift and cruise ROMEO demonstrator aircraft. A combination of high-fidelity unsteady Reynolds-averaged Navier-Stokes (URANS) simulations and mid-fidelity actuator disk and actuator line methods is applied to efficiently capture the dominant flow phenomena of a distributed electric propulsion configuration across multiple flight regimes. The mid-fidelity approaches are initially validated against fully-resolved propeller simulations to assess their accuracy and computational benefits. Subsequently, the influence of multi-propeller interactions on lifting arms and tail components is analyzed in hover, followed by an investigation of propeller-airframe interactions during forward and sideward hover maneuvers. A particular emphasis is placed on the modification of local inflow conditions and the subsequent distribution of loads. In the context of sideward flight, the present study explores
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.
Between the 1920s and 1930s, aluminum started replacing wood as the primary material in aircraft construction and soon became the backbone of modern aviation. Its popularity stemmed from a combination of properties, high strength-to-weight ratio, corrosion resistance, and ease of forming that made it ideal for demanding aerospace applications. Throughout much of the 20th century, high-strength aluminum alloys dominated aircraft design, accounting for 70-80 percent of commercial airframes and more than half of many military aircraft. Even after the introduction of fiber-polymer composites in the early 2000s, aluminum has remained a critical material because it continues to offer the strength, lightness, and versatility needed for modern aviation. Industry forecasts predict that commercial air travel will double in the next 25 years, which means more pollution will be released into the atmosphere. One way to help reduce these emissions is by building airplane fuselages and wings with
Forward flight rotorcraft analyses typically require time-marching aeroelastic trim of coupled rotor-airframe models, which is expensive for repeated evaluations. This paper presents a non-intrusive model-order reduction framework based on Dynamic Mode Decomposition with control (DMDc) identified from snapshot data. A POD projection reduces the state dimension; the DMDc operators are identified in the reduced coordinates and used for fast time-marching. Two sequential maps are constructed: DMDc-A reconstructs aeroelastic sectional airloads from low-cost rigid-blade airloads, and DMDc-S predicts coupled deformation, including blade and airframe degrees of freedom (DOFs), from the reconstructed airloads. The method is demonstrated for the XV-15 airplane mode configuration using a stick airframe model and a coupled rotor-airframe solver. Over 160-400 knots, it is found that the surrogate reproduces blade airloads and structural deformation of blade and airframe.
This paper discusses the design of a 2000-lb manned eVTOL aircraft propelled by a novel cycloidal rotor propulsion system. To systematically evaluate the performance of the proposed configuration, a coupled trim model was developed to quantitatively evaluate the performance of the configuration across a range of forward flight speeds. The trim framework integrates an efficient physics-guided neural-network-based aerodynamic model for cycloidal rotor performance with a vehicle-level dynamic response model. This framework is used to conduct a systematic parametric study to identify key cycloidal rotor and airframe design parameters. The selected configuration is verified using high-fidelity CFD simulations, and a detailed structural design, powertrain design, and CAD model of the aircraft is developed. In addition to CFD validation, the proposed cycloidal rotor underwent structural optimization to confirm the validity of such a concept at this scale. The results demonstrate that the
To strengthen the transition from conceptual to preliminary rotorcraft design, this work develops an integrated methodology combining early mass and load predictions with structural optimization. Embedded within the DLR frameworks IRIS and PANDORA, the approach orchestrates mass estimation, flight load prediction, and structural assessment in a semi-automated process. Topology optimization techniques are employed to design internal reinforcements between the aerodynamic fuselage and the cabin, enhancing structural fidelity ahead of preliminary design. A primary rescue helicopter serves as a case study, using representative ground and flight load cases as a basis for optimization. Although a full certification load spectrum is not covered, the selected cases capture the main design-driving conditions, demonstrating the benefits of early structural optimization. The presented method enables more informed structural decisions immediately after conceptual design, laying a solid foundation
By its seventh flight after the first take-off, the RACER (Rapid And Cost-Effective Rotorcraft) demonstrator smoothly reached the targeted 220kts speed in stabilized forward flight, validating the high-speed compound architecture developed by Airbus Helicopters in the frame of Clean Sky 2 programme. During the flight envelope exploration, the dynamic behavior of the main rotor was carefully assessed, by monitoring the vibratory loads and validating its aeroelastic stability. Particular care was taken to validate the predicted stability domain of the Dual Rotor phenomenon, a particular case of flap-lag coupling associated with high-speed flight conditions. This paper presents the most significant results shaping the success of RACER flight test campaign. After having introduced the theoretical background and the associated analytical equations, the simulation framework based on the comprehensive analysis tool STORM is presented to discuss the numerical resolution of the stability
The influence of ground, wall, and corner boundaries on multirotor vehicle performance was investigated through a series of controlled flight tests. Changes in rotor inflow profiles were represented by near-field rotor pressure measurements captured by a custom Kiel probe wake rake. Ground effect was characterized by reduced thrust and power requirements, primarily driven by the vehicle fuselage, which induced regions of reduced pressure and increased flow unsteadiness around the airframe. Operating near a wall boundary was found to restrict airflow into the portion of the rotor disk closest to the wall, leading to increased power requirements to maintain hover and a consequent reduction in performance. While vehicle orientation had minimal impact on overall rotor performance, it did influence local rotor inflow behavior near the wall, depending on the relative position of the interaction region formed with adjacent rotors. As the vehicle descends from the isolated wall effect into
In this work, comparisons between simulations & measurements in flight are proposed for different low-speed flight conditions out of ground effect on an Airbus Helicopters H175 PT1 rotorcraft equipped with a 5-bladed Spheriflex® rotor. Numerical results have been obtained by full-helicopter unsteady simulations relying on a single-rotor loose coupling approach between the Computational Structure Dynamics& Computational Fluid Dynamics parts, assuming blade elasticity and six degrees-of-freedom trim. One flight condition is tackled with both rigid-blade and elastic-blade modelling so as to highlight the influence of the blade softness on the results. The paper showcases good agreement between the simulation results & flight-test measurements regarding variations of main-rotor collective pitch, airframe attitude angles, rotor power & rotor loads with true airspeed. Airframe download is also numerically analysed.
With performance advances proposed for the Future Vertical Lift suite of aircraft and advancements in the electronic battlefield, it is imperative that advanced materials and concepts be included in the vehicle designs to meet the aggressive weight reduction objectives, structural requirements, and operational environment capabilities. Integrating electromagnetic (EM) shielding during the design process offers an opportunity to make progress towards the performance goals. To this end, efforts must be made to minimize the impact of this shielding to platform weight and structural performance. This article presents work to develop a hybrid multifunctional composite material technology that incorporates copper mesh into a carbon fiber and thermoplastic matrix structural composite material to achieve required levels of EM shielding and high levels of structural efficiency while reducing the overall weight of the system. This article focuses on the design of a representative helicopter
Current paper summarizes a correlation study of two flow solvers (CREATETE-AV Helios and Simcenter STAR-CCM+), routinely used at Sikorsky, with multiple model-scale wind-tunnel tests. The Helios modeling approach was aiming for a high-fidelity accurate simulation, whereas the STAR-CCM+ modeling approach was aiming for a fast turn-around time with reasonable solution accuracy with a relatively coarse mesh and simplifications. The two solvers generally agreed well with the test data within reasonable accuracy and captured the airloads and flowfield trends. The calculations presented herein show the impact of the turbulence model on component loads, the aerodynamic interactions among components, and the effect of transition modeling on rotor performance. The Reynolds-Averaged Navier-Stokes CFD model generally delayed separation and resulted in lower drag. By modeling the airframe supporting structure in CFD simulations, an improvement on correlation for inflow on the propeller plane was
We present our ongoing efforts towards the development of crash-tolerant rotorcraft airframe structures through topology optimization, with the goal of enhancing energy absorption and occupant survival during vertical impact events. A high strain rate explicit dynamics solver has been developed, fully accelerated on GPUs, to enable rapid and accurate simulation of impact events critical to crashworthiness evaluation. In parallel, we have built a scalable three-dimensional topology optimization framework that enforces stiffness, weight, and frequency constraints simultaneously, driving structurally efficient and vibration-resistant designs. Benchmarking results demonstrate significant GPU-enabled speedups, facilitating high-fidelity crash simulations and large-scale optimization at practical turnaround times. This work establishes a computational foundation for future integration of crash-centric objectives and constraints into the optimization framework.
Full-scale static test (FSST) is a key test program for the certification of new helicopter airframe. The strength and deformation requirements in airframe certification are substantiated by full-scale tests of the airframe structures. It provides experimental evidence that the structure is able to support limit loads without detrimental permanent deformation and carry ultimate loads for at least three seconds. In design stage, the total number of flight and ground limit load conditions is around 500. In FSST, the number of test load cases should be remarkably reduced. However, the selected load scenarios should cover all of the critical design load scenarios. In this paper, test load generation procedures in FSST of a light utility helicopter is explained. The comparison of design load envelope and static test load envelopes are provided.
A study published in Journal of Fluid Mechanics, reveals for the first time how noise is generated and propagated from these engines, technically known as boundary layer ingesting (BLI) ducted fans. BLI ducted fans are similar to the large engines found in modern airplanes but are partially embedded into the plane’s main body instead of under the wings. As they ingest air from both the front and from the surface of the airframe, they don’t have to work as hard to move the plane, so it burns less fuel.
The mystery of how futuristic aircraft embedded engines, featuring an energy-conserving arrangement, make noise has been solved by researchers at the University of Bristol. University of Bristol, Bristol, UK A study published in Journal of Fluid Mechanics, reveals for the first time how noise is generated and propagated from these engines, technically known as boundary layer ingesting (BLI) ducted fans. BLI ducted fans are similar to the large engines found in modern airplanes but are partially embedded into the plane's main body instead of under the wings. As they ingest air from both the front and from the surface of the airframe, they don't have to work as hard to move the plane, so it burns less fuel. The research, led by Dr. Feroz Ahmed from Bristol's School of Civil, Aerospace and Design Engineering under the supervision of Professor Mahdi Azarpeyvand, utilized the University National Aeroacoustic Wind Tunnel Facility. They were able to identify distinct noise sources originating
A new framework for performing high-fidelity computational aeromechanics simulations of the V-22 tiltrotor aircraft in hover mode has been developed. It is built on the HPCMP CREATE-AV Helios tool and utilizes scripted input generation and automatic replacement of modular model components. This new framework has been used to investigate the impact of various approaches to modeling the rotor aerodynamics, airframe aerodynamics, and periodic blade motion on predictions of aircraft hover performance in and out of ground effect. The findings indicate that an actuator line method can provide rotor performance predictions with comparable accuracy to a meshed-blade approach. However, body-fitted meshes are required to compute accurate airframe download. Furthermore, active trimming of rotor collective to a target thrust provides more representative aircraft aerodynamic performance than directly applying a collective angle as measured during flight test. The computational framework can
This paper presents the results of a research and development (R&D) effort focused on fluid structure interactions between airframe structures and bladder type fuel tanks during a crash environment. During this R&D effort, fuel tank and surrounding structure crash impact tests were conducted using an innovative test configuration that allowed low-cost fabrication of test articles which represented several different design architectures. LS-DYNA models of the crash test article configurations were also developed and correlated with the tests data. Good correlation between the test data and LS-DYNA analysis results was achieved. The paper also includes recommendations for design of the airframe structures around the fuel tanks based on the fluid structure interaction insights gained from the crash tests and analyses.
Installation effects of the Volocopter 2-X beam structures are studied by performing high-fidelity CFD simulations of a single and three-rotor configurations in hover. The studied cases are compared with simulations without airframe to investigate the installation effects. In addition, the noise emission of the configurations is simulated by using a Ffowcs Williams-Hawkings based CAA code. Scattering effects are also included by using a BEM code. The rotors are simulated at an identical RPM and are placed in their mounting position. Furthermore, an additional setup with individual rotor RPMs is simulated for the three-rotor configuration. The installation mainly affects the rotor wake, thrust and pressure fluctuations on the rotor, while the integral aerodynamic quantities remain almost unchanged. This resulted in additional oscillations in the acoustic pressure signal. Overall, the installation increases the OSPL by about 1.5 dB, but has a greater effect on the 3-20 harmonics. The
Rotorcrafts frequently operate in environments with severe atmospheric turbulence, for instance transferring people offshore to and from oil rigs as well as operating from and around ships. The presence of high turbulence can deteriorate performance, stability, and controllability of the rotorcraft. Additionally, such challenging conditions also generate loads that both airframe and rotor components must withstand. Following this, it is crucial to consider the impact of these operational atmospheric conditions during rotorcrafts design and development. In this context, numerical models are a fundamental tool to provide an easier and quicker way to explore the operative envelopes of the helicopter compared to performing experimental activities. This paper presents a rotor loads correlation activity between an experimental test designed and carried out by Leonardo Helicopters in which an AW189 helicopter was placed in the wake of a C-27J Spartan aircraft and a multibody structural model
A state-of-the-art emerging progressive damage failure analysis tool CDMat has been successfully applied to multiple material systems on open-hole tension and compression, and double shear bearing laminate coupons under static and fatigue loading including simulation to ultimate failure. CDMat also successfully demonstrated component-level strength/fatigue analysis under the Air Force Composite Airframe Life Extension (CALE) and the Fail-Safe Technologies for Bonded and Unitized Composite Structures (FASTBUCs) Programs. Building on the success of CDMat an integrated software solution for certification and sustainment of rotorcraft primary composite structures is being developed. A method and an algorithm for fatigue crack growth simulation in laminated structures are proposed to improve the accuracy of CDMat fatigue predictions. The method is based on using cohesive material model, tracking material points at the crack front, and calculating the pointwise energy release rate employing
As part of the design process, structural assessment represents an important aspect in the development of new airand rotorcraft. It plays a critical role in supporting the weight of the aircraft, transmitting loads from the rotors to the airframe, and ensuring the overall safety and integrity of the vehicle. The conceptual design phase is characterized by exploration and evaluation of broad design concepts, with minimal detail regarding structural design. In contrast, the preliminary design phase involves refining the chosen design concept and conducting more detailed structural analysis and optimization to prepare for the subsequent detailed design phase. In order to evaluate the airframe, the opensource based design environment PANDORA has been developed at DLR. This paper presents an overview of model generation, topology optimization, sizing, and crashworthiness aspects in PANDORA using validation examples and generic rotorcraft models.
Sikorsky has successfully planned and executed several significant aircraft structural certification programs for military aircraft in the past few decades. These certifications included the CH-53K® with NAVAIR, the HH-60W with the Air Force and the Raider X® Competitive Prototype Aircraft with the Army. The methodologies for these certifications addressed the different requirements of each of these branches of the military as well as satisfying emerging techniques for structural life management ("Sikorsky Airframe Full Spectrum Customer/Supplier Collaboration", Reference 1). Safe Life Crack Initiation, Flaw Tolerant (Enhanced) Safe Life Crack Initiation and Fail Safe Life Limit Crack Propagation analysis had been rigorously pursued and demonstrated in these programs. This paper takes a retrospective look at what turns out to be many similarities in these methodologies that previously have been the subject of significant debate in the industry. The combined knowledge of these
This study explores the best vibration reduction using a multicyclic controller through an individual blade control (IBC) actuation scheme for a lift-offset coaxial helicopter in high-speed flight. The rotorcraft dynamics model consists of coaxial, three-bladed counter-rotating rotors and a finite element fuselage stick model constructed based on the measured data of the XH-59A helicopter. The two-way coupled rotor-body vibration analysis results exhibit excellent correlations with the test data for rotor hub loads and airframe vibrations. The best actuation scenarios are sought for the minimum vibration of the vehicle using either open- or closed-loop control scheme. It is shown that the IBC actuation effectively reduces the vibrations at both locations of the rotorcraft. The co-reduction of 3P (per rotor revolution) and 6P vibration of the rotorcraft is achieved using the multicyclic control with offline system identification. A multicyclic harmonic IBC actuation enables to suppress
This paper presents the design and development of a swashplateless micro helicopter with a target endurance of more than 30 minutes using an optimized direct drive rotor connected to a unique rotor hub that has blades with a flap hinge and proprietary skewed-lag hinge with pitch-lag kinematic coupling. This obviates the need for conventional swashplate based cyclic pitch control, as the cyclic variation in control angle is achieved by cyclically varying the motor RPM. UP12 underactuated propulsion system developed by VertiQ is used for the baseline design. The blades in this propulsion system are optimized using Blade Element Momentum Theory (BEMT) analysis with lookup table to enhance its performance. BEMT is validated using experimental measurements and then used to optimize the geometry of the rotor. The optimized blades offer better performance and are 30% lighter than the original 3D-printed plastic blades. The prototyping of the Micro Aerial Vehicle (MAV) is completed by
A rotorcraft comprehensive analysis was used to generate aeroelastic stability predictions for both Ingenuity and the Mars Sample Recovery Helicopters. The analysis was performed multiple times for each rotor system with sequential increases to the level of modeling complexity. Initial cases used an independent blade analysis, trim inflow distribution, no airframe degrees of freedom, and a hover condition (a time-invariant problem). The final model used all blades, dynamic inflow, airframe rigid body degrees of freedom, and a Floquet theory approach to the flutter analysis. The approach of sequentially increasing modeling complexity was employed to ensure the causes of any observed instabilities could be identified. For each case, stability results were determined across a range of air densities, tip Mach numbers, and rotor collective pitch settings. For the Sample Recovery Helicopter, a forward flight condition analysis with the highest level of modeling complexity was also performed
Equipment used in aerospace non-destructive inspection presents opportunity for modernization. Many inspection cells in production operate using a widely available control system software that is suitable for most inspection applications with minimal customization. The size and complex geometry of airframe components demand more application-specific system design to ensure the reliability and cycle time required for an aerospace production schedule. Ordinary inspection systems require manual teaching for program generation and lack datum-finding systems required to rerun programs without modification. Integration of offline programming software and machine vision instruments can save inspection technicians hours or shifts per part by eliminating the need for program retraining due to variation in part delivery position. Modernized inspection cells will reduce labor burden on technicians and provide reliable cycle time information to production planners.
Most of current jet aircraft circulate fuel on the airframe to match heat loads with available heat sink. The demands for thermal management in wide range of air vehicle systems are growing rapidly along with the increased mission power, vehicle survivability, flight speeds, and so on. With improved aircraft performance and growth of heat load created by Aircraft Mounted Accessory Drive (AMAD) system and hydraulic system, effectively removing the large amount of heat load on the aircraft is gaining crucial importance. Fuel is becoming heat transfer fluid of choice for aircraft thermal management since it offers improved heat transfer characteristics and offers fewer system penalties than air. In the scope of this paper, an AMESim model is built which includes airframe fuel and hydraulic systems with AMAD gearbox of a jet trainer aircraft. The integrated model will be evaluated for thermal performance. JP-8 fuel is recirculated on the airframe to maintain cooling the oil for AMAD
Determining the optimum cross section for each primary structural member of an airframe structure has always been an iterative process since changing the stiffness of one member redistributes loads. Each iteration of internal loads calculations with a global aircraft finite element model (GFEM) followed by strength and stability checks results in further cross section changes (sizings) to reduce weight or regain positive margins of safety. The handoffs between tools and the update process for the next iteration is time consuming and has many opportunities for errors. This paper will describe a tool developed at Sikorsky to automatically iterate sizings saving development time and executing more sizing iterations than historically possible which saves weight. The tool can operate on metallic and composite structures. The development time and weight savings is critical to support ever shrinking time to fielding/market for commercial and military models.
A simple model of the transition aerodynamics of Joby Aviation's electric tilt-propeller VTOL aircraft was developed by combining a surrogate model of CFD propeller solutions with semi-empirical models of airframe aerodynamics and interactional aerodynamics. The model was calibrated to match CFD results of the entire aircraft, as well as flight test results of the actual aircraft. Using this model, loads and power requirements across the range of shaft tilt angle and airspeed combinations for trimmed flight - -the "conversion corridor" often described in tiltrotor performance reports - -are analyzed, and resulting performance limitations are discussed. Additionally, a novel approach to transition flight is introduced in which the angle of attack and shaft angle are automatically determined by the flight controller, rather than manually controlled. Using the simple transition aerodynamics model, transition loads and power requirements with this control approach are discussed, and
The H160-B is the latest helicopter design from AIRBUS HELICOPTERS with the extensive use of sandwich technology in the airframe. A sandwich with face sheets from CFRP and honeycomb cores is a robust outer skin of a helicopter. Furthermore it shows a very good tolerance to impact damages and a very good reparability. At Airbus Helicopters great experience is available which is required to understand and to control all manufacturing parameters, that are driving the quality of such parts. Powerful inspection technologies are in place to maintain the high level of manufacturing quality. In this paper an overview of the parts on this Helicopter made with sandwich technology will be given. These are cowlings and structural parts as well as principal structural elements (PSE) on main load paths. The respective certification requirements and related means of compliance demonstrations will be explained in detail. Special attention is paid to the applied methods for the damage tolerance
Sikorsky airframe collaboration with suppliers and military customers has been evolving over the past 20 years to continually decrease the cycle time for design development including customer concurrent oversight and airworthiness certification ("Information Week - Communication Aids Design", Reference 1). Future Vertical Lift (FVL) aircraft rapid development schedules including the Raider-X Future Attack Reconnaissance Aircraft (FARA) Competitive Prototype (CP) fly-off and subsequent production design have mandated the need for concurrency in contractor / customer awareness of design details. To address this need, Sikorsky has developed a uniquely collaborative system to share structural analysis applications, structural models and substantiating data as it emerges real-time in development from multiple sources with customer oversight to assure consistency and accuracy to satisfy requirements for rapid certification.
The F-35 Lightning II is an all-weather stealth combat aircraft that is intended to perform warfare strike missions and electronic surveillance capabilities at speeds up to 1.6 Mach. Composites comprise 35% of the airframe weight, with the majority being bismaleimide, as well as some carbon nanotube-re-enforced epoxy, which has a tensile strength approximately 100-times greater than steel. Any deviations in external dimensions can interfere with stealth capabilities, and at supersonic speeds, prove catastrophic to both plane and pilot.
Avionics systems provide electronic guidance, navigation, and communications through harsh and hostile environments for a wide range of airframes. Operating environments present elevated levels of shock and vibration; vacuum-like conditions of high altitudes; corrosive effects of hydraulic fluids, fuels, and other chemicals; and the effects of wide temperature ranges. Avionics systems must handle such challenging environments even as they are being designed with greater functionality into smaller payload spaces.
An Overview of Surface Tolerant Adhesives for Bonded Airframe Structures.
The conventional approach in aircraft landing loads analysis, such as for shock absorber development, is using a nonlinear set of equations and a modal representation of the airframe. For preliminary shock absorber design studies, a linearized set of equations may provide a highly efficient simulation method to limit the parameter space of linear shock absorber models. This article develops a set of linearized equations of motion to simulate the landing touchdown event while capturing airframe flexibility effects using a transfer function. The linearized flexible model demonstrates the ability to generally capture flexibility effects and output responses of interest with a significantly reduced simulation time compared to both fully flexible and nonlinear reduced-order models. The linearization of a Fiala tire model is accomplished by scaling the longitudinal tire stiffness such that the peak tire drag force matches that of the nonlinear model, and the vertical tire stiffness is
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