bluuebunny/crossref_metadata_2025 huggingface dataset:
Advanced Multi Axis Trim and Drill Cell for Low Volume, Multiple Part Configuration in a JIT Environment
Authors:   Bell Helicopter Textron Canada, Laird Andrew
Published: October 2024

The aerospace manufacturing arena is a constantly evolving challenge to all of the participants. The conjuncture of continual cost-cutting pressures and product changes have created technical and system challenges to implant a manufacturing infrastructure that can cope and deliver widely different parts. All this in a climate of shorter delivery schedules and more complex parts geometries produced by advanced CAD systems. The challenge for equipment configuration is to create highly flexible robust machine configurations that can be adapted to multiple part configurations in the most efficient manner. This paper will research the inherent challenges in implementing automation into a highly manual operation where the technologies have to facilitate the flexibility yet ensure strict control of part variation. It will explain the technology mix required to integrate into an optimized machine configuration to process flow of parts in a JIT environment where hundreds of different parts have to go through a similar process in the minimum amount of time with maximum reliability
Manufacturing of Composite Helicopter Tailboom Using Automated Fiber Placement
Authors:   National Research Council Canada, Yousefpour Ali ,   Bell Helicopter Textron Canada Ltd., Beaulieu Pierre , Chen Jihua , Octeau Marc-Andre , Roy Steven
Published: October 2024

This paper briefly summarizes the manufacturing process of a composites helicopter tailboom prototype, with the focus on improving quality and productivity as well as reducing manufacturing cost. The ultimate goal of the project is to develop a stable and reliable automated fiber placement process for mass production of the composite tailboom. For this purpose, different fiber path generation scenarios were first explored in the early stage of the project. Information such as fiber angle deviations, gaps and overlaps were collected. Feedback was provided to the designers to further improve the tailboom design. Second, since fiber placement process is influenced by different variables, including layup speed, compaction force, heater temperature, humidity level, etc., the interactions of different process parameters were investigated. The optimum layup speed was identified under different conditions. Third, to achieve the quality requirements, methodologies were developed to reduce machine downtime and to track and repair manufacturing defects. As a result of the project, a one-piece, fiber placed composites tailboom was successfully manufactured.
Utilizing Selective Laser Sintering For Production Fabrication of Peculiar Support Equipment
Authors:   Bell Helicopter Textron Inc, Przano Dominic
Published: October 2024

Traditionally, helicopter peculiar support equipment is designed, developed, and fabricated using conventional methods, primarily with metallic materials. Specifically, component repair and overhaul tools containing unique, complex features (e.g. internal involute splines) are fabricated using conventional broaching, machining, or electrical discharge machining (EDM) techniques. These techniques combined with the low volume production and acquisition of these products, result in high cost and long lead times. As an alternative, Selective Laser Sintering (SLS), the process of using 3D CAD models to "grow" parts using a laser to sinter powdered material, can be utilized with the primary benefits being inherent cost savings and lead time reductions. This process also facilitates the ability to develop unique, innovative, and simpler tools that would have been impractical or impossible to fabricate using conventional methods. Feasibility, proofing, and practical implementations are the focus of this paper.
Real-Time Simulation of Coaxial Rotor Configurations with Combined Finite State Dynamic Wake and VPM
Authors:   Advanced Rotorcraft Technology Inc., Zhao Jinggen , He Chengjian
Published: October 2024

This paper describes a first-principle based finite state dynamic rotor wake model that addresses the complex aerodynamic interference inherent to coaxial rotor configurations in support of advanced vertical lift aircraft simulation, design, and analysis. The high fidelity rotor dynamic wake solution combines an enhanced real-time finite state dynamic wake model (DYW) with a first-principle based viscous Vortex Particle Method (VPM). The finite state dynamic wake model provides a state-space real-time modeling capability for advanced rotorcraft configurations and VPM provides a first-principle based solution for the complex rotor wake problem without using ad-hoc parameters. To account for the mutual aerodynamic interference between multiple rotors, the finite state dynamic wake model was enhanced with several essential modeling parameters to empirically account for important physical phenomena. These modeling parameters were determined based on high fidelity VPM simulations. The developed methodology provides a first-principle based real-time finite state dynamic wake model suitable for coaxial rotor configurations. To validate the developed model, simulation results for the rotor performance, the rotor wake dynamics, and the flow field of different coaxial rotor configurations in both hover and forward flight conditions were compared with available measured data. The simulation results demonstrate good correlation with the measurements for all the cases evaluated.
A Performance Analysis of Compound Helicopter Configurations
Authors:   University of Glasgow, Ferguson Kevin , Thomson Douglas
Published: October 2024

The compound helicopter is a high speed design concept that is once again being explored due to the new emerging requirements for rotorcraft to obtain speeds that significantly surpass the conventional helicopter. This increase in speed, provided efficient hover capability is maintained, would make the compound helicopter suitable for various roles and missions in both military and civil markets. The paper features two compound helicopters. The first configuration features a coaxial rotor with a pusher propeller providing additional axial thrust, and is referred to as the coaxial compound helicopter. The second configuration, known as the hybrid compound helicopter, features a wing and two propellers providing thrust compounding. In this study, the performance of these two compound helicopter configurations are assessed and compared with a conventional configuration. The paper presents the standard performance parameters of each configuration which include the power required in steady level flight, the maximum range, the maximum endurance and the hover ceiling of each of the aircraft configurations. Furthermore, a performance analysis of each configuration flying standard helicopter missions is conducted.
Assessing the Fidelity of a Human-in-the-Loop Helicopter Flight Research Simulator
Authors:   DSTO, Manso Sylvain , Bourne Kate
Published: October 2024

The Defence Science and Technology Organisation (DSTO) has modified the Simulator Fidelity Rating (SFR) scale developed by the University of Liverpool, UK, for application to Human-in-the-Loop (HiL) research tasks. The modified SFR (mSFR) was applied successfully over three trials to assess the fidelity of various tasks performed in the DSTO fixed-base helicopter research simulator. The mSFR scale was found to provide a repeatable method to measure simulation fidelity. To identify simulator deficiencies, the mSFR scale was accompanied by formal written feedback from test pilots describing the use of task strategy, control activity, and useable cue environments. The DSTO research simulator was found to be deficient in heave, aural, and small translational rate cues for the cases examined. It is proposed that consistent application of the mSFR in HiL research tasks will provide greater confidence in the research outcomes DSTO is able to provide to the Australian Defence Force community.
The Effect of Ship Size on the Flying Qualities of Maritime Helicopters
Authors:   The University of Lincoln, Owen Ieuan ,   The University of Liverpool, Scott Paul , White Mark
Published: October 2024

This paper describes the use of Computational Fluid Dynamics (CFD) to produce unsteady ship airwakes to investigate the effect of ship size on the pilot workload at the helicopter-ship dynamic interface. A ship model was created to represent modern naval vessels and geometrically scaled to represent smaller and larger scale ships that currently operate maritime helicopters. An unsteady airwake for each ship was computed at 40 knots for both the Headwind and Green 45° Wind Over Deck (WOD) conditions, while the mid-scale ship was also computed at 30 knots. Using Strouhal scaling, the mid-scale ship airwake was scaled both in terms of velocity and ship size. Comparisons of the resulting small and large scaled data were made with the computed CFD data and the use of Strouhal scaling was found to a feasible method for the modification of airwake data. An offline analysis using a SH60B Seahawk-like helicopter was used to determine the impact of the ship size on the pilot workload. As the ship size increased, so did the levels of predicted pilot workload due to the increasing energy contained within the turbulent wake as the ship size was increased.
Spacial Modelling and Simulation of On-deck Helicopter Securing and Manoeuvring
Authors:   Carleton University, Leveille Michael , Langlois Robert
Published: October 2024

For smaller ships in rough seas, flight deck motion can become considerable and result in significant dynamic behaviour of embarked helicopters. The current state-of-the-art in dynamic modelling of the on-deck helicopter/ship dynamic interface includes a fully-spacial securing simulation and a separate one capable of modelling planar traversing and manoeuvring operations. A fully-spacial securing and manoeuvring simulation named SSMASH (Spacial Securing and Manoeuvring Analysis for Shipboard Helicopters) has been developed to provide complete analysis capability of the on-deck helicopter/ship dynamic interface. Specifically, a new capability to model helicopter response to manoeuvring events in the presence of flight deck motion is realized. The model is compared to the state-of-the-art securing simulation Dynaface®and experimental data from land-based manoeuvring trials. Excellent correlation with the Dynaface® simulation is achieved, while good correlation with the experimental data is also observed.
V-22 and the Future of Carrier Onboard Delivery (COD): Improving the Way the Navy Re-Supplies Its Carriers and Maritime Forces
Authors:   The Boeing Company, Roby Brian ,   Bell Helicopter Textron Inc., Barber John , Karika Ken
Published: October 2024

The Carrier onboard delivery (COD) mission involves the use of aircraft to ferry personnel, mail, supplies, VIPs, and high-priority cargo, such as replacement parts from shore bases to aircraft carriers. Several types of aircraft, including helicopters, have been used by navies in the COD role. Helicopters in the USN fleet have also played a major role in re-supply with the Vertical Onboard Delivery, or VOD mission element. The COD/VOD combined mission has heretofore amounted to a maritime hub-and-spoke system whereby the COD aircraft deploy the major re-supply cache to a carrier (hub), followed by distribution of supplies and personnel (spoke) to other carriers and ships using helicopters in the VOD role. The Navy is currently considering options for future COD platforms as the Greyhounds approach the end of their current service life supporting the carriers. This paper discusses the potential for improvements in cost and time executing the Navy’s carrier re-supply using the V-22 Osprey in the COD and COD/VOD combined re-supply roles.
Lessons Learned from NH90 NFH Helicopter-Ship Qualification Testing across the Entire Dutch Fleet
Authors:   Royal Netherlands Navy, Hoencamp Alrik
Published: October 2024

In general, the helicopter industry delivers a helicopter that has undergone elaborate in-flight test campaigns performed to demonstrate safe flight within the expected operational envelope. However, establishing the operational potential and limitations for safe shipboard helicopter operations is still considered a national responsibility. For some reason, there are still no internationally agreed regulations or standard procedures to establish the required helicopter-ship operational limitations. Consequently the kind of interpretation given to such limitations differs strongly between countries. As it is assumed that each country aims for maximum operational flexibility of a particular helicopter-ship combination, with minimum expenses and without any concessions to flight safety, this paper summarizes the lessons learned from the NH90 NFH helicopter-ship qualification testing across the entire Dutch fleet. Aided by a predictive software tool, named "SHOL-X", which eliminates subjective elements to the largest possible extend in order to determine operational envelopes for in-service conditions, the Netherlands Ministry of Defence was able to achieve tremendous savings in time and expenses of helicopter-ship qualification test campaigns. This paper is specifically aimed at pilots and engineers who are involved in flight trials of helicopter-ship combinations as part of a complex flight test programme for which they are required to plan, conduct and report on ship helicopter operational limitations.
Analysis of Health and Usage Monitoring System (HUMS) Users Perspective towards Mission Benefits Using Regression Analysis
Authors:   University of South Carolina, Zaman Tanzina , Bayoumi Abdel
Published: October 2024

Mission benefits are seen as an important indicator of overall effectiveness of Condition-Based Maintenance (CBM) implementation. This creates incentives for Army personnel at all levels to adopt CBM. The research approach presents a step in the direction of better understanding of how mission benefit areas like morale, sense of safety etc. are influenced by perspective of army personnel who fly and maintain Blackhawk, Kiowa, Chinook and Apache helicopters around the world equipped with Health and Usage Monitoring Systems (HUMS). The study also investigates if this attitude can be described by a linear regression model. Response data collected from seventy-six helicopter personnel was analyzed to determine whether regression analysis can describe the users’ attitude towards different aspects of benefits. When cross validation was performed, the multiple linear regression model was able to predict performance response with a correlation coefficient as high as 0.95.
Methods and Techniques for Analysis of Field Data for Commercial Rotorcraft Components
Authors:   Bell Helicopter Textron Inc., Muñiz Richard , Neus Mike
Published: October 2024

Rigorous reliability and maintainability engineering practices are staples of military rotorcraft development and production programs. However for many commercial rotorcraft development programs, R&M tends to be a box-checking exercise, due to tighter schedule and budget constraints. Once a commercial rotorcraft program has entered the production and field support phase, reliability engineering often takes a backseat to more reactive practices which involve issue resolution instead of risk prevention. This paper will present a high-level discussion of common reliability engineering methods and techniques for analyzing field data for commercial rotorcraft and components. The intended audience includes product and customer support personnel who may lack the level of technical knowledge and expertise of reliability engineers, but who nonetheless would like a deeper understanding of reliability analysis of field data, so that they can begin planning for the development of new processes and tools to enable them to switch to a more proactive workflow model.
Development of a Neural-Network (NNET) Based Engine Model for a Two-Stroke Engine of a Rotary Wing UAV
Authors:   Aselsan Inc. - MGEO Div., Olcer Fahri
Published: October 2024

In general, control laws developed for stabilizing rotary wing platforms are dependent on the constant rotor speed assumption that is maintained by a dedicated rotor speed controller, known as governor. Likewise, textbooks on the helicopter theory and most of the technical publications present existing theories and develop new ones under the constant rotor speed assumption, relying on a perfectly working governor. Exceptions to this assumption appear in the literature where the use of rotor transcends the conventional form, such as tiltrotor aircrafts or slowed rotor concepts. In these examples rotor speed degree of freedom had to be included for the stability and performance analysis. In the literature necessity of the rotor speed degree of freedom is shown even for a conventional helicopter in which case the governor did not work well enough to consider the rotor speed constant in the simulations. In case of small size rotary wing UAVs, maintaining a constant rotor speed may not be that much possible or in another perspective the amount of rotor speed variation might have significant effects on the flying qualities of a small size RW-UAV whereas such variations may not pose a problem for the most conventional helicopters. In this regard this study proposes Neural-Network Based engine modeling for a RW-UAV in order to account for the rotor speed degree of freedom in flight dynamics analyses. A test case study for the implementation is also presented.
Optimized Powerplant Configurations for Improved Rotorcraft Operational Performance
Authors:   Cranfield University, Ali Fakhre ,   Noesis Solutions, d'lppolito Roberto , Goulos Ioannis , Vassilios Pachidis , Konstantinos Tzanidakis
Published: October 2024

This paper presents an integrated multidisciplinary rotorcraft design and optimization framework, deployed for the design and assessment of a conceptual rotorcraft powerplant configuration at mission level. The proposed approach comprises a wide-range of individual modeling theories applicable to rotorcraft flight dynamics, gas turbine engine performance and weight estimation as well as a novel physics-based, stirred reactor model for the rapid estimation of gas turbine gaseous emissions. A novel Single-Objective and Multi-Objective Particle Swarm Optimizer is coupled with the aforementioned integrated rotorcraft multidisciplinary design framework. The combined approach is applied to the multidisciplinary design and optimization of a reference Twin Engine Light civil rotorcraft modeled after the Eurocopter Bo105 helicopter, operating on representative mission scenario. Through the application of Single-Objective optimization, optimum engine design configurations are acquired in terms of mission fuel consumption, engine weight and gaseous emissions at constant technology level. Multi-Objective studies are carried out in order to quantify the optimum interrelationship between mission fuel consumption and gaseous emissions for the representative Twin Engine Light rotorcraft operation and a variety of engine configurations. The proposed approach essentially constitutes an enabler in terms of focusing the multidiscipalinry design of rotorcraft powerplants to realistic, three-dimensional operations and towards the realization of associated engine design tradeoffs at mission level.
A Computational System Model for Gearbox Loss-of-Lubrication
Authors:   The Pennsylvania State University, McIntyre Sean , Yu Qingtao , Kunz Robert , Chang Liming , Bill Robert
Published: October 2024

A multi-physics, multi-scale numerical simulation technique is presented for modeling gearboxes operating under loss-of-lubrication conditions. Accordingly, the tool includes components for contact mechanics, tribology associated with EHL through boundary lubrication regimes, CFD modeling of the gearbox flow, conduction within the gears, housing and other gearbox components, and free convection to the external environment. These component physics models are coupled in a fashion that accommodates their disparate space and time-scales. This paper describes each sub-model in detail, and the space-time coupling strategies used. Results are presented for a spur-gear test stand operated at NASA Glenn Research Center. The physics of the eventual runaway temperature excursions subsequent to loss-of-lubrication are captured. Model shortcomings and attendant future work are identified.
Nanolubricant Oil Additives for Performance Improvement of the Intermediate Gearbox in the AH-64D Helicopter
Authors:   University of South Carolina, Gouda Kareem , Bayoumi Abdel , Tarbutton Joshua , McVay Jacob
Published: October 2024

This paper presents a new nanolubricant for the intermediate gearbox of the Apache aircraft. Historically, the intermediate gearbox has been prone for grease leaking and this natural-occurring fault has negatively impacted the airworthiness of the aircraft. In this study, the incorporation of graphite nanoparticles in mobile aviation gear oil is presented as a nanofluid with excellent thermo-physical properties. Condition-based maintenance practices are demonstrated where four nanoparticle additive oil samples with different concentrations are tested in a full-scale tail rotor drive-train test stand, in addition to, a baseline sample for comparison purposes. Different condition monitoring results suggest the capacity of the nanofluids to have significant gearbox performance benefits when compared to the base oil.
Improving Wear and Fretting Characteristics with Fiber Reinforced Aluminum Liners
Authors:   Bell Helicopter, Owen Dwayne , Modrzejewski Brian , Gardner Scott
Published: October 2024

A study has recently been performed to investigate improvements between the interfaces of the transmission case and rolling element bearings that provides for extended wear life. This study included demonstration testing of the improvements shown in wear and fretting characteristics at the bearing/case interface by using a Fiber Reinforced Aluminum (FRA) liner. This liner material is an engineered metal matrix composite that exhibits the best mechanical properties of each of the constituent materials, and provides enhanced capabilities in terms of structural, thermal, and chemical performance. An additional benefit of using FRA liners is a reduced weight compared to traditional steel bearing liners. This weight improvement is achieved with little to no redesign work, and without increasing manufacturing complexity. With proper sizing, the FRA bearing liners are a direct replacement for the existing part. This paper recollects all the results of this recent study, as well as plans for the future.
In Search of Rotorcraft Airframe Fatigue Assessment Methodology
Authors:   NAVAIR, Phan Nam ,   Engility, Moon Suresh
Published: October 2024

Rotorcraft hub loads are functions of main and tail rotor rotational frequencies and introduce n per revolution stresses into an airframe structure. Airframe fatigue life is currently computed using the stress-life method. This approach uses an S-N curve with an endurance limit where low amplitude cycles below the endurance limit do not contribute to damage accumulation. This method does not consider the low-cycle (high stress) and high-cycle (low stress) interaction effects. To overcome these deficiencies, an ε-N (strain-life isoprobability) approach is proposed. The recorded strain history was analyzed using Fourier analysis to identify n per revolution vibratory stress components. It was further analyzed with a peak-valley algorithm to extract once per maneuver and GAG cycle values. The recorded strain history was transferred to a critical location using the strain transfer function developed by finite element analysis (FEA). The stress-life, strain-life, and proposed approach (ε-N) were utilized to compute stub wing fatigue lives with various probabilities of failure. The prediction was verified using 21 cracked and 293 uncracked stub wings in the fleet at various flight hours. The probability of fleet stub cracking was determined using a Weibull distribution fit. The analytical predicted fatigue lives correlated well with observed stub fatigue cracking in the fleet at 1.86% probability of failure. The ε-N approach can predict fatigue cracking observed in fleet rotorcraft in comparison to significantly higher fatigue life prediction by stress-life and strain-life methods.
A Damage Tolerance and Fatigue Evaluation Approach for Composite Rotorcraft Airframe Structures
Authors:   AIRBUS Helicopters Deutschland, Engleder Alexander ,   Tec. University Ingolstadt, Burger Uli , Francescatti Davide
Published: October 2024

The paper presents a methodology to perform a damage tolerance evaluation for composite airframe principal structural elements (PSE). This methodology consists out of five steps, first a logic how to identify PSE (step 1), then a threat assessment (step 2) for them, followed by a coupon testing approach (step 3) for showing dent depths visibility thresholds. Then a coupon test approach is presented for showing no growth behavior of barely visible impact damages (BVID) for one design service goal (DSG) and design ultimate load (DUL) capability and for clearly visible impact damages (CVID) no growth behaviour for one inspection interval and minimum design limit load (DLL) capability is demonstrated (step 4). Those coupon test results are then used to determine allowable strain limits for sizing of PSE. Finally the results of step 4 are then validated by structural component tests (step 5) by application of a certain test sequence to cover both, static- and fatigue damage tolerance requirements, i.e. first application of DLL, then simulation of one DSG with BVID, then application of DUL, followed by a simulation of one inspection interval with CVID and repairs and finally check of residual strength capability which is minimum DLL for such parts.
Structures Perspective for Strength and Fatigue Prognosis in Composites
Authors:   University of Texas at Arlington, Nikishkov Yuri , Seon Guillaume , Makeev Andrew
Published: October 2024

Recent advances in understanding deformation and failure mechanisms of polymer-matrix composites used in rotor structures enable accurate and efficient measurement of material stiffness, strength, and fatigue characteristics based on testing small unidirectional laminate specimens. Successful failure predictions increased our confidence in the development of virtual test methods replacing some of the standard tests of multi-directional laminated composite materials with three-dimensional models accurately predicting deformation, damage topography, strength, and cycles to failure. However, the remaining key questions are related to the ability of transitioning the material scale virtual test information to larger composite structures. This work presents results of the feasibility assessment targeting the scaling of knowledge and methods acquired at the material scale, to larger structural elements.
Investigation of Probabilistic Failure Predictions with Progressive Damage in Composites
Authors:   US Army Research Laboratory, Haynes Robert , Shiao Chi-yu , Chen Tzikang
Published: October 2024

Three probabilistic techniques are compared that allow for the estimation of sensitivity of a system to statistically distributed input parameters. These methods could be useful for estimating sensitivity of the system with an intractable response surface that must be calculated numerically using computational algorithms such as Monte Carlo experiments. All three methods estimate the baseline response using a Monte Carlo experiment. Two of the methods estimate the perturbed response using additional Monte Carlo experiments based on perturbed input parameters, generated either with a different seed or the same seed used to generate the instances of the input parameters for the baseline Monte Carlo experiment. The third method uses the ratio of the probability of occurrence of the perturbed and baseline input parameters to estimate the perturbed response. These techniques are demonstrated using a composite material progressive damage model with one, two, and three random input variables. This work explores the correlation between number of simulations in a Monte Carlo experiment and the variability in sensitivity. The same-seed Monte Carlo method is shown to be the most accurate method. The probability-ratio method is shown to be significantly less computationally expensive.
AFP Monocoque Composite Tailboom Full Scale Fatigue Testing
Authors:   Bell Helicopter, Colle Alain ,   National Research Council Canada, Beltempo C. , Lapalme Maxime , Drouin Pierre , Rogers John , Rutledge Robert.
Published: October 2024

This paper describes two phases of full scale testing performed on a Bell Helicopter Textron Canada Limited (BHTCL) composite monocoque tailboom manufactured using Automated Fiber Placement (AFP). This technical demonstrator tailboom was designed for use on a Bell 407 model as part of a collaboration program with Bombardier Inc., Composite Atlantic Ltd. and the National Research Council Canada (NRC). The tailboom cone consisted of a skin made from an AFP layup of carbon epoxy fiber tape combined to a hand layup made from fabric. The skin is then bonded to six hand layup frames. The fatigue test objectives were to validate the component to flaw tolerant safe life requirements and establish damage tolerance to light and medium caliber ballistic impacts. The test article, containing embedded flaws, impact damages, and representative repairs, was subjected to a full four lifetime fatigue test at NRC. All testing during this phase was conducted at 250 °F 'hot-dry' conditions to simulate operating temperatures seen in service. The test article successfully sustained four lifetimes of fatigue testing, followed by residual strength testing to both limit and ultimate loads. In the second phase of the full scale testing, the article was subjected to six ballistic impacts with deadweights replicating a critical load condition in the field, interspersed with short 'go-home' fatigue cycling in the laboratory. Regular inspections and near-real-time data analyses were performed throughout testing. No permanent deformation, new damage or existing damage growth was sustained by the tested composite components during the fatigue tests, subsequent residual strength tests, or fatigue loads following ballistic impact, thereby proving the flaw and damage tolerance capability of the structure.
Structural Health Sensing of Damage Precursors using Magnetostrictive Particles Embedded in Composite Structures
Authors:   U.S. Army Research Laboratory, Hall Asha , Haile Mulugeta , Haynes Robert , Coatney Michael , Yoo Jin
Published: October 2024

Over the last two decades, tremendous progress has been made in structural health monitoring (SHM) using various sensing techniques such as acoustic emission, eddy current, strain gages, to diagnose damage in aerospace, mechanical and civil infrastructures. Despite this progress, there are still many challenges to address in SHM. Among these challenges is detection of precursors to matrix cracking, fiber/matrix debonding, and delamination. Magnetostrictive smart materials such as Terfenol-D (Tb0.3Dy0.7Fe1.92) (Etrema Products Inc., IA, USA) have proven useful as non-contact strain sensors using Hall Effect or pick-up coil to measure change in magnetization due to strain. In this study, our team will conduct a specific number of fatigue cycles at 1, 100, 1,000, 10,000, 100,000, and 1,000,000 cycles. After each fatigue loading a destructive examination of the specimen surface will be conducted by Scanning Electron Microscope (SEM). By this systematic evaluation, the phenomenon of crazing, the propagation of micro-cracks and delaminations, and the factors that lead to catastrophic failure will be investigated, thereby enabling correlation of the current damage state to the magnetization.
Design, Development, and Qualification of Computationally Designed Alloys
Authors:   QuesTek Innovations LLC, Grabowski Jeff , Sebastian Jason , Taskin Kerem , Houser Clay , Asphahani Aziz , Snyder Dave
Published: October 2024

QuesTek Innovations LLC has applied its Materials by Design® computational design technology and its Integrated Computational Materials Engineering (ICME)-based methods to successfully design, develop and implement two new high-performance gear steels (Ferrium® C61™ and Ferrium C64® steels) and two new high-performance structural steels (Ferrium S53® and Ferrium M54® steels) that are commercially available from Carpenter Technology. All four Ferrium alloys have been approved for use in demanding flight critical rotorcraft applications and have been awarded SAE AMS numbers for procurement. QuesTek has also designed several other high performance alloys using ICME technologies, including a stainless nitridable bearing and gear steel, a new high strength/high SCC-resistant aluminum alloys (upgrade from 7050 and 7075 aluminum), a beryllium-free Cu-Ni alloy, a castable titanium alloy, and a high strength/high toughness castable stainless steel.
An Alternative Approach for System Architecture Design
Authors:   Eurocopter, Serge Germanetti , Guillanton Erwan
Published: October 2024

In the frame of the avionics development, more and more risks have to be managed. The technology risk is the one which concerns most of the engineers. But industrial risk is perhaps more critical for a company. In the current context, the high level of integration to reduce weight and cost is the key factor that drives most of the Hardware developments. This paper addresses this problem, explains past experience, and provides rationale for evolution. The possibility to introduce a set of independent reusable sub-systems is proposed to ease incremental certification. The driven elements for selecting such a strategy are explained and will serve as Key Performance Indicators to manage system architecture choice, finalization of each independent reusable sub-systems perimeter and the sequence to implement them on the legacy and new helicopter fleet. Concrete applications are identified to deploy a scalable and configurable application of the modular and flexible architecture via a set of independent reusable sub-systems and Field Loadable Softwares. The EC175, developed according to this approach, is presented as an example. Finally, the topics to be discussed with the certification authorities are introduced.
Transitioning to MBSE in a Large Systems Engineering Organization that Develops Complex Mission System for Helicopters
Authors:   Lockheed Martin, Felter Stephen
Published: October 2024

Transitioning from a Document Based Systems Engineering approach to a Model Based Systems Development (MBSD) approach in a large systems engineering organization with both legacy and start up programs presents a serious challenge. MBSD differs from Model Based Systems Engineering (MBSE) in that it applies across the design disciplines (SW, I&T, HW, CM). Barriers include concerns about increased cost and schedule to new programs and minimizing impacts to legacy programs with a large investment in non-model based artifacts. In spite of these concerns, future programs will demand a systems engineering environment that enhances the ability of the engineering team to collaborate across both disciples and geography. For this reason Lockheed Martin's Mission Systems and Training (MST) facility in Owego NY, whose primary product includes complex mission systems for manned and unmanned helicopter systems, has begun the transition from a Document Based Approach to a Model Based Approach. Several key goals associated with the transition include providing a turnkey approach to programs, automated generation of systems engineering work products from the model and support for reusable software components. This paper discusses the approach to defining and achieving these goals and provides recommendations for organizations that are interested in transitioning to MBSD.
Rotor Wireless Load and Motion Monitoring Sensor Network
Authors:   Bucknell University, Marchiori Alan ,   Sikorsky Aircraft Corporation, Bouquillon Brian ,   UTRC, Bajekal Sanjay , Davis Mark , Soldner Nicholas , Tokgoz Cagatay
Published: October 2024

The Sikorsky Aircraft Corporation (SAC) and the U.S. Army Aviation Development Directorate - Aviation Applied Technology Directorate (ADD-AATD) are jointly sponsoring the Capability-Based Operations and Sustainment Technology-Aviation (COST-A) program. The objective of COST-A is to demonstrate an integrated set of high-value diagnostics, prognostics, and system health management technologies that reduce the maintenance burden, without sacrificing safety. A key technology for the COST-A project was the development of a rotor local wireless sensor network (RLWSN) for purposes of data acquisition from self-powered, wireless rotor sensors. Two key requirements were identified: deterministic quality of service for wireless communications and a scalable architecture that supports growth in the number of sensors for future applications. This paper presents a model-based approach to design and implementation of a RLWSN gateway that addresses these requirements. The approach, which included simulation and validation of models, has resulted in an architecture for an antenna array that ensures the desired quality of service at the physical layer of wireless transmissions without the need for protocol based recovery methods, thereby improving bandwidth efficiency and utilization raising the upper bound on scalability of the sensor network.
Unsteady Boundary Layer Transition Measurements by Differential Infrared Thermography
Authors:   German Aerospace Center (DLR), Richter Kai , Merz Christoph , Raffel Markus
Published: October 2024

Maintaining laminar flow over a large portion of a rotor blade reduces drag appreciably. Therefore, the location of boundary layer transition is an important design parameter for rotor blades. Unsteady laminar/turbulent boundary layer transition is of special interest, since modern rotor blade design methodologies increasingly take dynamic performance of into account. Once the design is concluded, the real transition position on the blade is of great interest as the knowledge of the exact transition position is needed for both the validation of the design and the performance assessment. The paper demonstrates the detection of unsteady boundary layer transition with a high framing rate infrared camera and the differential infrared thermography (DIT) method. DIT is based on image intensity differences between two subsequently recorded measurement images. A pitching NACA0012 airfoil served as the test object. The measurement results are compared with the results of unsteady CFD simulations based on the DLR TAU code.
Stability, Control, and Simulation of a Dual Lift System Using Autonomous R-MAX Helicopters
Authors:   Stanford University, Powell J. ,   San Jose Sate Research Foundation, Cicolani Luigi ,   Army Aviation Development Directorate, Berrios Marcos , Tischler Mark
Published: October 2024

Cargo missions of the near future will require transportation of increasingly heavy loads to remote locations that are at distances farther, and at altitudes higher, than what can be accomplished by current helicopters. Using two helicopters to carry a single load, termed dual lift, provides heavy lift on demand and avoids the very costly design and development of a special purpose heavy lift helicopter. This paper discusses the stability and control aspects of a dual lift system using autonomous R-MAX helicopters. Unique dual lift modes lie in a frequency range that affect helicopter attitude responses and should be considered while designing an inner-loop (attitude) dual lift controller. One such mode is unstable and is characterized by the helicopters drifting away from each. In order to stabilize this mode, helicopter separation feedback is used. Unlike in a single lift system, there exists only one pendulum mode in a dual lift configuration and a cable angle that is relative to a no swing plane is needed to isolate the swinging motion and improve damping of the payload. With the identified control challenges as a foundation, a multi-objective parametric optimization approach is used to design a controller for a dual lift system that meets a comprehensive set of ADS-33E stability and performance specifications.
Motion feedback improves performance in teleoperating UAVs
Authors:   Max Planck Institute for Biological Cybernetics, Venrooij Joost , Lächele Johannes , Pretto Paolo , Bülthoff Heinrich
Published: October 2024

Teleoperation of a remote vehicle is challenging, due to on-board sensing, the transmission to the control station, and the display of information to the operator in an informative way. In an effort to increase the situational awareness of the operator we included physical motion feedback in addition to visual feedback. In this study we investigated the effects of motion feedback on operator performance in teleoperation hover tasks. An experiment was conducted where we systematically varied the scaling of the motion feedback and measured the performance and control stick activity of participants controlling a simulated remote vehicle in a virtual environment. Simulated lateral wind disturbances acted on the remote vehicle, forcing participants to constantly correct the position. Our results show increased performance and stick activity in conditions that include motion feedback. Based on the results, we conclude that providing motion feedback allows the operator to reject external disturbances more effectively, resulting in the increased performance.
Solution of Glauert?s Contraction/Expansion Equations for Wind Turbines and Powered Rotors with Swirl
Authors:   Washington University in St. Louis, Peters David , Howard Andrew , Modarres Ramin , Rahming Benjamin
Published: October 2024

Glauert (1934) developed a set of wake contraction or expansion equations for lifting rotors in either wind turbine or powered mode. Up until now, no one has been able to solve these equations. Goorjian and Wu (1972) proved that, for hover, Glauert's equations have no solution with a bounded wake rotation over the range 0 ≤ F ≤ 1. Goorjian also showed that momentum theory is internally inconsistent and cannot result in a wake contraction solution that matches both the centrifugal force balance and conservation of angular momentum in the far wake, or, in other words, the stream tubes will mix together in the real world. In this work, it is shown that an internally consistent momentum theory can be developed if the pressure balance in the far wake is relaxed. Glauert actually makes this assumption later in his work but does not revisit the wake contraction implications. With this new, internally consistent momentum theory, it is shown that the wake contraction equations can be solved for both wind turbines and helicopters in climb, descent, or hover.
Turbulence Transport Phenomena in the Wakes of Wind Turbines
Authors:   Intelligent Light, Duque Earl ,   The Pennsylvania State University, Jha Pankaj , Bashioum Jessica , Schmitz Sven
Published: October 2024

A true physical understanding of the subtleties involved in the recovery process of the wake momentum deficit downstream of utility-scale wind turbines in the atmosphere has not been obtained to date. While the wind energy community has now a better understanding of some of the effect of the atmospheric stability state on wind turbine power production and wake recovery within an array of wind turbines, available field data are, in general, not acquired at sufficient spatial and temporal resolution that would allow to dissecting some of the mysteries of wake turbulence. It is here that the Actuator Line Method (ALM) has evolved to become the technology standard in the wind energy community for modeling the wakes of single wind turbines as well as arrays of wind turbines and wind farms immersed in an atmospheric boundary-layer flow. This work presents the ALM embedded into an OpenFOAM-LES solver (ALM/LES) and applies it to two small wind farms, the first one consisting of an array of two NREL 5-MW turbines separated by seven rotor diameters in neutral and unstable atmospheric boundary-layer (ABL) flow and the second one consisting of five NREL 5-MW wind turbines arranged in two staggered arrays of two and three turbines, respectively, in unstable ABL flow. Detailed statistics involving power spectral density (PSD) of turbine power along with standard deviations reveal the effects of atmospheric turbulence and its space and time scales. Furthermore, the effect of turbulence generated directly by upstream wind turbines on the power response of downstream wind turbines is quantified. High-resolution surface data extracts in addition to selected Reynolds-stress statistics provide new insight into the complex recovery process of the wake momentum deficit governed by turbulence transport phenomena.
Application of rFlow3D code to performance prediction and the wake structure investigation of wind turbines
Authors:   Tokyo University of Science, Oe Harutaka ,   Ryoyu Systems Co., Sugawara Hideaki ,   Japan Aerospace Exploration Agency, Tanabe Yasutada , Yamamoto Makoto , Sugiura Masahiko , Aoyama Takashi , Matsuo Yuichi
Published: October 2024

Numerical simulations based on NREL (National Renewable Energy Laboratory) Phase VI and MEXICO (Model Experiment in Controlled Conditions) experiments using rFlow3D CFD code are conducted. The rFlow3D code is a multi-disciplinary analysis tool of flow-structure coupling, trim analysis, and noise prediction for rotorcraft developed at Japan Aerospace Exploration Agency. In this study, the numerical computation based on NREL Phase VI experiment with SA turbulence model is conducted to validate the accuracy of performance prediction of the horizontal axis wind turbines. Additionally, numerical computation for MEXICO experiment with a Navier-Stokes (NS) flow solver is conducted to confirm the ability of rFlow3D to predict the wake structure. The NREL Phase VI computational results indicate that the utilization of turbulence model improves the performance prediction in fully separated flow conditions. Meanwhile, MEXICO computation results show the solver can accurately predict the vortex structure and the axial velocity deficit in the wake.
Understanding the Wind Turbine Wake Breakdown Mechanism with CFD
Authors:   University of Liverpool, Barakos George , Carrion Marina , Woodgate Mark , Steijl Rene
Published: October 2024

This work explores the breakdown of the wake downstream of the MEXICO rotor and assesses the capability of CFD in predicting its correct physical mechanism. The wake is resolved on a fine mesh able to capture the vortices up to 8 radii downstream of the blades. At a wind speed of 15m/s, the main frequency present in the CFD signals for up to 4 radii was the blade passing frequency (21.4Hz), where the vortex cores fall on a perfect spiral. Between 4 and 5 radii downstream, higher frequency content was present, which indicates the onset of instabilities and resulted in vortex pairing. The effect of modeling a single-blade domain and a full rotor domain was studied, showing similar prediction of the location of the onset of instabilities, but an increased frequency content was captured in the latter case. Empirical and wake models were also explored, and compared with CFD and a combination of kinematic and field models was proposed. The encouraging results obtained suggest that the wake instability of wind turbines can be predicted with CFD methods, provided adequate mesh resolution is used.