Browse Topic: Airframes

Items (444)
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
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
Skladanek, YanCoisnon, RemiFerullo, David
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.
Yolum, UgurAydın, EnesÇimen, FatihÖkten, Tolga Temmuz
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.
Das, GhanendraJames, KaiKennedy, GraemeWebb, LonnieOluwalana, Daniel
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.
Desvigne, DamienEmbacher, Martin
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
Kim, JeewoongColeman, DustinKlimchenko, VeraMin, Byung-YoungWake, Brian E
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
Herz, SageMcCrink, Matthew
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
Schwinn, DominikPetsch, MichaelKohlgrüber, DieterWeiand, PeterAtci, Kagan
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
Haynes, RobertLuzetsky, HarryPhifer, Ellen
To comply with the Paris Agreement targets set in 2015, significant reductions in aircraft emissions are required. This demands a fundamental shift in aircraft design. Therefore, it is essential to study how future aircraft designs will affect the integration and design of landing systems. This research project examines the landing gear issues that arise from adopting specific future aircraft configurations. The study focuses on two primary configurations: the high-aspect-ratio wing and the ultra-high-aspect-ratio wing, with selected aircraft concepts from Cranfield University as baselines. It investigates the design and integration of conventional landing systems into these new aircraft concepts, highlighting the limitations posed by the modified airframes. The selected concepts include either telescopic or trailing arm arrangements, with attachment points on the wings or fuselage. A methodology for preliminary sizing of landing systems is presented, emphasizing automation and
Martin, RaphaëlStockford, JackSmith, Howard
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 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.
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
Toni, Darryl
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.
Schwinn, DominikAtci, KaganWeiand, PeterPetsch, MichaelKohlgrüber, Dieter
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
Nikishkov, GennadiyMatthews, PeterMakeev, AndrewSeon, GuillaumeNikishkov, Yuri
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
Hong, Seong HyunKim, Do-HyungJung, Sung NamKim, Dong Kyun
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
Bhatnagar, KirtiAbhishek, AbhishekArya, BidhanBansal, Divyanshi
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
Muth, MoritzKrämer, EwaldKeßler, Manuel
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
Moushegian, AlexBodling, AndrewHayden, EricFarish, David
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
Capizzi, Cristiano MariaPrederi, DavideFrassoldati, GregorioBucciaglia, Giuseppe
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.
Bolukbasi, AkifWeisenburger, Richard
Ground vibration testing (GVT) is an important phase of the development, or the structural modification of an aircraft program. The modes of vibration and their associated parameters extracted from the GVT are used to modify the structural model of the aircraft to make more reliable dynamics predictions to satisfy certification authorities. Due to the high cost and the extensive preparations for such tests, a new method of vibration testing called taxi vibration testing (TVT) rooted in operational modal analysis (OMA) was recently proposed and investigated by the German Institute for Aerospace Research (DLR) as alternative to conventional GVT. In this investigation, a computational framework based on fully coupled flexible multibody dynamics for TVT is presented to further investigate the applicability of the TVT to flexible airframes. The time domain decomposition (TDD) method for OMA was used to postprocess the response of the airframe during a TVT. The framework was then used to
Al-bess, LohayKhouli, Fidel
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.
Elrod, JoshuaWaterman, MichaelParker, Dylan
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
Suat, YunusÖzkan, Ayşe DilekSirkeci, Ersin
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.
Toni, Darryl
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
Stoll, AlexVeble Mikić, Gregor
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
Arelt, RainerGoerlich, StefanArent, Jan-ChristophHailer, BenjaminDambaur, Mathias
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.
Joseph, AnthonyDaley, RobertKoeppel, Anne
Aircraft are high value-adding and long-living assets, while aircraft cabins are expensive consumer products tailored to each customer. Vastly changing requirements and needs force aircraft holders regularly to instruct modifications in order to remain attractive on the market. Adaptations, modifications, and development of innovations are handled by multiple organizations, not by a central one like the aircraft’s manufacturer or owner. Although the Continuing Airworthiness Management Organization manages all aircraft instance-specific documents as required by aviation regulations, their format and types of management differ. Besides, not all information that arises during a parts design phase is included. That means, overall, the consistent model-based maintenance of data within all phases of PLM up to disposal is not guaranteed. The loss of information during all lifecycle phases can cause the prolongation of planning phases and the actual ground-time during retrofit processes since
Moenck, Keno H. W.Laukotka, Fabian N.Deneke, ConstantinSchüppstuhl, ThorstenKrause, DieterNagel, Thorsten J.
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.
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.
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
Stachiw, TerrinKhouli, FidelLanglois, Robert G.Afagh, Fred F.
ABSTRACT
Sharifi, MajidTandon, GyaneshwarBrown, IanJordan, Delaney
Sealant is applied between joined aircraft parts in the final stage of the assembly, before installation of permanent fasteners. In this paper a novel approach for aircraft assembly simulation is suggested, which allows to resolve the transient interaction between parts and sealant in the course of airframe assembly process. The simulation incorporates such phenomena as compliance of parts, contact interaction between them and fluidity of sealant with presence of free surface. The approach based on fluid-structure interaction techniques consists of two basic steps: at the first one the pressure of sealant is found after corresponding fluid dynamics problem is solved and at the second the displacements of parts and sealant are calculated through the solving of contact problem. Iterations between structural and fluid dynamics solvers are performed to achieve convergence. The developed approach is demonstrated on example of joining of two test aircraft panels. The viscosity of sealant was
Eliseev, ArtemLupuleac, SergeyGrigor'ev, BorisShinder, JuliaBouriquet, Jacques
The National Research Council of Canada and Université de Sherbrooke performed flight testing of an Actively Stabilized Slung Load on the NRC Bell 206 Research Aircraft. Hover, Attitude Capture, NRC designed Lateral Precision Hover, and Frequency Sweep mission tasks were performed for bare airframe and slung load aircraft configurations. The load mass ratio was 0.12 while the slung load pendulum mode was 1.3 rad/sec at a damping ratio of 0.2 for the 40-pound per active tether saturation load system setting. Time domain response indicated that the load remained controllable with damped and underdamped behaviors. Frequency domain analyses confirmed pilot comments indicating HQR 4 handling qualities ratings for bare airframe and stable slung load behavior. This rating degraded to HQR 5 for task execution with slung load oscillation. Pilot workload was due to lateral cycle input requirements of 2 to 3 inch amplitudes at 1 to 2 Hz frequency. Operationally, the coincidence of pilot inputs
Alexander, MarcPerron, EitenneCraig, GregoryRancourt, David
Advancements in Damage Tolerant Airframe Structures in combination with Structural Health Monitoring (SHM) have created an opportunity to exploit the synergies in these technologies to change the paradigm for Airframe Life Management for future Aircraft. In the last decade or more, Sikorsky has validated multiple production helicopter Airframes using Damage and Flaw Tolerant certification requirements. The experience of the authors of this paper contributed to the recent joint services and industry development of the Rotorcraft Structural Integrity Program (RSIP as specified in MIL-STD-3063) for design of future military rotorcraft. In addition, Sikorsky has also developed a range of technologies relevant to SHM to reduce over-inspection and maintenance to drive increased operational availability. Combined, these developments will allow new Airframe designs to meet the US Army's new requirements for Maintenance Free Operational Periods (MFOP), for example 200 flight hours for the
Toni, DarrylSarlashkar, Avinash
The U.S. Army monitors the structural integrity of its rotary-wing aircraft fleet through annual evaluations and reporting via the Airframe Condition Evaluation (ACE) program. ACE evaluations capture the location and character of structural defects for each aircraft, which are then available for trending and detailed analysis by engineers with the U.S. Army Combat Capabilities Development Command Aviation & Missile Center (CCDC AvMC). As analytic methods are increasingly advanced through the digital thread, CCDC AvMC has sought to improve available trending, modeling, and analysis tools beyond status quo to provide higher fidelity visuals to both aid communication with decision makers, and also to reveal structural defect trends which may not otherwise be evident. This paper will detail the development and utility of the ACE Color Mapping Application within the ACE Mapping Module and its impact on product support of U.S. Army aircraft with regard to airframe structural integrity.
Peltier, JaredChhotu, Prasant
High-fidelity CFD simulations of hovering flights of the multi-rotor Volocopter 2X (VC2X) aircraft with three different heights above the ground and an out of ground reference case are presented. The tool chain applied consists of the CFD solver FLOWer, which is loosely coupled to the flight mechanic tool VFAST. For all simulations an adequate representation of the flight mechanics is of crucial importance since the high number of trim degrees of freedom of the VC2X has a significant influence on the flight physics. A short introduction and validation of VFAST is carried out, which shows that VFAST already provides valuable stand-alone results for the considered flight envelope. The in ground and out of ground CFD simulations showed a highly complex flow field for the VC2X. With increasing ground proximity the number of vortex structures induced by the ground increases and the rotor wake is characterized by strong fluctuations. Basic rotorcraft in ground effect phenomena, like a high
Miesner, SebastianSchäferlein, UlrichKeßler, ManuelKrämer, Ewald
Mercer Engineering Research Center (MERC) is supporting Naval Air Systems Command (NAVAIR) in the determination of external airframe loading requirements and test rig design support for an MH-60 full scale fatigue test demonstrator project being conducted in collaboration with the Australian Defence Science and Technology Group (DST Group). The analyses included determination of loads for quasistatic and vibratory flight conditions, sensitivity of the structural response to the loads, displacements at actuators across the MH-60R usage spectrum, and feasibility of driving aircraft vibrations at frequencies lower than those measured in flight - specifically, obtaining vibration levels measured at 17.2 Hz by imposing forces at only 2.15 Hz. The studies also addressed the minimum number and locations of actuators required for static and vibratory loading.
McGinty, RobertVine, JohnLiebschutz, DanConjelko, PhilipBrenna, Jeffery
Presently the fatigue lives of MH-60R dynamic components and airframe are based on a usage spectrum developed using pilot surveys. In order to better define the usage spectrum and to extend component and airframe fatigue life, the Health & Usage Spectrum (HUMS) System was installed on the U.S. Navy MH- 60R Rotorcraft. So far 207 aircraft are equipped with the HUMS systems and 121,334 flight hours of good data have been recorded. The regime recognition programs recognize 315 maneuvers, but are consolidated to 94 maneuvers of MH-60R usage spectrum, for which the component measured loads are available. To better define usage spectrum in detail and compute realistic component fatigue life, an additional maneuver of low Angle Of Bank (AOB) from 10 to 25 degrees was added, but the measured component loads were not available at this AOB to implement HUMS. Thus, measured flight loads data of level flight and AOB turns at 30, 45, and 60 degrees were utilized to derive component loads at 20
Moon, SureshLiebschutz, Daniel
Under the Rotorcraft Structural Integrity Program (RSIP) Pilot Demonstration effort, the requirements defined in MILSTD-3063 were applied to a Future Vertical Lift (FVL) representative, model performance specification objective aircraft to demonstrate a standardized RSIP process. This paper covers application of the MIL-STD-3063 approach on SB>1 DEFIANTTM airframe structural components and presents the evolution of the resulting RSIP Master Plan. Elements of the resulting Master Plan are discussed in detail. The Master Plan is the basis for collaborative establishment of structural integrity with an efficient and effective airworthiness substantiation footprint. The discussion includes case studies of the application of logic flow to requirements in MIL-STD-3063 for the determination of specific, relevant action items to airframe structural demonstration components. Execution of this pilot effort led to lessons learned and highlighted feedback to inform the ongoing development of the
Chiu, LisaKrastel, MatthiasLorthridge, DerrellMcCarthy, Dennis
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