bluuebunny/crossref_metadata_2025 huggingface dataset:
Outer Loop Requirements for Vertical Lift Unmanned Aerial System Automated Flying Qualities
Authors:   University of Portland, Ivler Christina ,   United States Naval Test Pilot School, Geyer William
Published: September 2024

An unmanned aerial system automation qualities framework (previously known as the unmanned aerial system handling qualities framework) has been in development to determine a set of criteria and mission task elements for evaluating the airworthiness of unmanned aerial systems. The framework is being developed to apply across a range of unmanned aircraft from Group 1 to Group 4-5, via scalable predicted (quantitative) automation qualities metrics as well as scalable mission task elements. Prior work has developed scalable mission task elements and predictive attitude response criteria, scaled from MIL-DTL-32742 (which supersedes ADS-33E-PRF). This paper extends the UAS automation qualities framework to provide predictive (quantitative) criteria for velocity and position responses. The paper evaluates Froude scaled velocity disturbance rejection bandwidth and position disturbance rejection bandwidth requirements from MIL-DTL-32742 and describes and evaluates two new metrics, velocity bandwidth and tracking bandwidth, as possible new criteria. These metrics are defined in the paper and were evaluated as predictive quantities for automation handling qualities level using lateral reposition and depart/abort mission task elements. The evaluation was conducted by modifying the control system to achieve parametric variation of the metrics of interest and then assessing the performance with simulation and flight test of mission task elements. Three small unmanned vertical lift aircraft were used in this study; the University of Portland hexacopter, the USNTPS X8-M coaxial quadcopter and Synergy 626 single main rotor helicopter. It was found that the newly defined tracking bandwidth and velocity disturbance rejection bandwidth are key predictive criteria for automation qualities level for automated mission task elements on the test aircraft.
Piloted Simulation Evaluation of Maneuver Optimization Control for a Tiltrotor Aircraft
Authors:   The Pennsylvania State University, Horn Joseph ,   Piasecki Aircraft Corporation, Bridges Derek ,   US Army CCDC AvMC, Berger Tom , Hendrick Christopher , Hagwood Grey , Miller Doug
Published: September 2024

The Adaptive Digital Automated Pilotage Technology (ADAPTTM) flight control software package aims to take advantage of redundant controls to improve safety, survivability, and performance for advanced rotorcraft. Vehicle Maneuver Optimization (VMO) is one component of the ADAPTTM architecture intended to increase maneuverability. VMO uses feedforward actuation within the control null space of over-actuated aircraft to minimize power required during quasi-steady maneuvers. In this study, the system is applied to a generic tiltrotor aircraft and evaluated in piloted simulations at the Penn State Rotorcraft Simulator. In this application, VMO uses flap deployment and nacelle tilt to reduce power required in turn maneuvers. Piloted simulation results show that the system effectively reduces power required during Break Turn and Maximum Performance Turn Mission Task Elements (MTE), while handling qualities are equivalent to the baseline controller without VMO. The system was also tested for a terrain flight mission scenario. Pilot comments indicated better handling with VMO in the aggressive maneuvering phases of the flight.
Development and Validation of Full-Aircraft Free-Flight Maneuvering Simulation using Tightly Coupled CFD-CSD and FCS
Authors:   Sikorsky a Lockheed Martin Company, Zhao Jinggen , Luszcz Matt , Kinkead Matt , DeFreitas Marco
Published: September 2024

This paper demonstrates the recent success of developing a high-fidelity Co-Simulation (CoSim) technology to enable free-flight full-aircraft maneuvers using closed-loop tightly coupled Computational Fluid Dynamics (CFD), Computational Structural Dynamics (CSD) with full-production aircraft Flight Control Systems (FCS). This new development empowers the previous CFD-CSD maneuver simulation with a digital brain from the production aircraft FCS and enables a true high-fidelity predictive capability with significant improvement in the accuracy of the results, removing its dependency on other analysis as inputs. The newly developed CoSim methodology was correlated with S-97 RAIDER® helicopter flight test maneuvers. This study shows that development and usage of the current state-of-the-art methodology, when carefully validated and applied, can capture the complex rotorcraft physics due to fluid and structure interaction during maneuvering flights with sufficient accuracy to support both early stage of design and flight test planning.
Wind Tunnel Testing of X2™ Technology Spinning Coaxial Hubs with Aspirated Inlets - Comparison Between Two Wind Tunnel Models and with CFD
Authors:   Sikorsky A Lockheed Martin Company, Dziuba Dylan , Lorber Peter , Hein Benjamin , Wallace Brian , Kim Jeewoong , Rivera Antonio , Bunting Colin , Sandor Shawn , Min Byung-Young , Bowles Patrick
Published: September 2024

A two-phase wind tunnel test was conducted to evaluate aerodynamic performance on a 1/5th scale model of the Sikorsky/Boeing X2™ technology representative aircraft for Future Vertical Lift (FVL). The test program provided valuable aerodynamic data for two important elements of the design: the faired coaxial hub system and the main inlet flow leading to the engine interface. Studies from previous X2™ technology aircraft have shown that hubs, pylons and sail fairings have strong interactions, and if well integrated can lead to low drag aircraft designs. Rotorcraft main inlets generally have aggressive turns; therefore, this inlet design was investigated for distortion and total pressure loss. Accuracy of modeling these aerodynamic interactions using Computational Fluid Dynamics (CFD) and other forms of computational aerodynamic assessment requires supporting empirical testing for validation. The two wind tunnel facilities used in Phase 1 and 2 offered different and unique advantages compared to each other, which allowed the Sikorsky/Boeing team to generate a large, complementary aerodynamic and propulsion database for comprehension as well as simulation validation.
How Computer Vision is Changing the New Way of Health Data Analysis
Authors:   Airbus Helicopters, BOUTALEB Abdelhafid , DIAZ Alexandre
Published: September 2024

As part of maintenance improvement on helicopters, Airbus Helicopters has made available a proactive analysis service based on Health and Usage Monitoring System data generated during the flight. The present paper describes the new approach used to detect and classify any changes in time series behavior thanks to A.I. (Artificial Intelligence) especially computer vision. This new approach is more efficient and relevant than the classical approach based one statistical law [Ref 1]; in fact, it is acting, as the human eye, which is able to identify easily any abrupt change on the time series, and classifies it, whether Machine learning or Deep Neural Networks both have shown excellent results in term of classification accuracy. First part of this paper highlights how the learning data were prepared, then the second and the third parts give more details about how the time series are transformed into image presentation and how the different Artificial Intelligence models were selected and feed, ultimately the obtained results.
Overview of the Subscale RAVEN Flight Controls and Modeling Testbed
Authors:   NASA Langley Research Center, Geuther Steven , Simmons Benjamin , Ackerman Kasey
Published: September 2024

The Research Aircraft for eVTOL Enabling TechNologies (RAVEN) Subscale Wind-Tunnel and Flight Test (SWFT) model is a subscale aircraft built for flight dynamics and controls research demonstrated in wind-tunnel and flight-test experiments. The intent of this paper is to provide a summary of past, current, and future efforts being pursued by the RAVEN-SWFT project. Initially, vehicle development guidelines were crafted by a multidisciplinary team to ensure that the RAVEN-SWFT vehicle was well suited for research in multiple areas, including aero-propulsive modeling, flight controls, and autonomy, among others. The vehicle has been used to obtain extensive wind-tunnel data, enabling aero-propulsive model development across the transition flight envelope and validation of computational tools. The vehicle will be used to conduct flight testing in order to evaluate modeling strategies and flight control logic. The RAVEN-SWFT model also serves as a risk reduction activity for a conceptual, full-scale vehicle in the 1000-lb class. The next steps in the project are to successfully demonstrate free flight in hover, transition, forward flight, and the reverse thereof, utilizing custom control laws integrated onto the RAVEN-SWFT avionics hardware. The project intends to publicize all of the geometry, data, and methods in future reports.
Virtual Reality on a Motion Platform for Rotorcraft Shipboard Simulation
Authors:   NAVAIR, Gaublomme Donald ,   J.F. Taylor Inc, Meyers Kyle ,   American Systems, Zinchiak Andrew , Calvillo Robert , Smith Zachary
Published: September 2024

Piloted simulation has been used for decades to support flight test activities at the Naval Air Warfare Center Aircraft Division located at Naval Air Station Patuxent River, MD. Conventional lab stations at the Manned Flight Simulator facility have been used effectively to support a wide range of flight test requirements. However, there were limitations with these conventional lab stations when the purpose was to assess handling qualities and pilot workload while landing rotorcraft aboard a ship. Two critical simulation elements were determined to be necessary: (1) an expanded field of view so the pilot could see the ship deck below the aircraft and (2) a motion system to provide the pilot with vital proprioceptive cueing in the turbulent ship environment. A new Virtual Reality Lab was developed at Patuxent River that included these key features. The primary components of the lab included virtual reality headsets, an Unreal Engine image generator, ocean and ship visual models, a six degree-of-freedom motion platform, and a generic cockpit. This paper describes development of the lab, various issues that were encountered, and plans for future improvements.
A Rotary Union to Provide Active Flow Control to a Mach Scale Rotor
Authors:   US Army CCDC AvMC, Copp Peter
Published: September 2024

A rotary union was developed and tested that allows for active flow control to be tested on the Army General Rotor Model System (GRMS) Mach scale rotor test stand. The union has a center pass through for the rotor shaft and control links. Three air channels formed by mortised seals allow air transit between the fixed frame and the rotating frame. Each channel can move 10 SCFM at 30 psi with a pressure loss of 0.2 psi. The union torque depends on seal differential pressure. The torque is 11 lbf-ft at 11 psi or 2.5 HP at 1250 RPM which is sufficient for a rotor tip Mach of 0.64. The union was tested on GRMS to 1250 RPM. The seals require differential pressure of 2 psid to engage and at 10 psid the leak rate was less than 0.5 SCFM. Considering future research, a non-dimensional flow control scaling parameter is derived which accounts for Coriolis effects.
Introduction of new infusion manufacturing processes for Main Rotor Blades: Opportunities, Drawbacks and a common Endeavor to make it a Success
Authors:   Airbus Helicopters, Zellhuber Markus , Thivend Julien
Published: September 2024

The succession of the BK117 D-2 main rotor concept from the semi-rigid rotor to the BK117 D-3 bearingless main rotor (BMR) system, derived from the H135, held many new and innovative additional benefits in its wake. Although the H135 system is the best on the market regarding maintenance effort and maintenace cost (DMC), it was the purpose to push this benchmark even further. To achive additional benefits, three major improvements needed to be successfully implemented and none of them was a given. First to mention is the concept of the blade being separated in three parts. In case of foreign object damage (FOD), most of the time only the outer part needs to be repaired. In parallel a new possibility to fold the system with a full folding capacity was introduced with the challenge to realize the extremely low DMCs of the H135, in a decisively bigger helicopter and to benefit from the experience of millions of flight hours and thousands of helicopters operated throughout the world. Second a reduced flapping hinge offset was introduced to improve the comport of ride. The third point is the attachment bearing stress laminate providing the benefit of slim shape in the connection area between Flex control unit (FCU) and blade airfoil section. All this with the reduction of vibration in mind that results from changing a four-bladed rotor to a five-bladed one [1]. We were motivated to include also a, for such kind of critical part, new liquid infusion molding technology, to have all process parameters in our own hands, to make the production of blades more reliable and at the same time reduce the number of nonconformities by introducing more and more automation in production, which was enabled using the bearing laminate design of the attachment [2]. This innovative new design, in combination with a new manufacturing process introduced in a different production site under considerable time and cost pressure, needed the dedication of a multi-disciplinary transnational team, to finally overcome all deviations that became visible throughout the industrialization and/or prototype phase. This finally led to a mature serial production within a two years time frame. The paper is intended to highlight the often shortened and only briefly recognized period of preproduction, prototyping and the serialization and maturation of critical composite parts.
Prediction of Structural Rotor Loads: When to Consider Drivetrain Dynamics?
Authors:   German Aerospace Center - DLR, Weiss Felix
Published: September 2024

The constant, undisturbed rotor hub rotational speed is a commonly applied boundary condition and simplification in computational analyses of helicopter rotors. Revoking this simplification and considering rotor-drivetrain interactions in the hub's rotational degree of freedom can - but doesn't necessarily - improve the predictions of structural blade loads, especially in the lead-lag direction. To estimate the drivetrain's potential to influence the lead-lag loads, this paper proposes the systematic evaluation of the modified collective lead-lag modes. These eigenmodes, as well as the resulting modification of lead-lag loads in the aeromechanic simulation, are presented and compared for the rotordrivetrain configurations of the Eurocopter Bo105 and the Sikorsky UH-60A. The study focuses on understanding the drivetrain's influence rather than on making high fidelity predictions. In the Bo105 case, the drivetrain impact on the lead-lag moments is significantly more pronounced than for the UH-60A. The discussion of this difference includes the assessment of the blade passage frequency magnitudes (4/rev for a number of nb = 4 rotor blades) and their sensitivity to the modified collective second lead-lag eigenfrequency, which in turn is changed by a varying drivetrain stiffness. While a very stiff drivetrain causes an eigenfrequency of 4/rev with high-magnitude resonance for the Bo105, the UH-60A configuration maintains an eigenfrequency above 4/rev for the whole range of applied stiffness values. For rotor-drivetrain systems, especially near resonance, the nb/rev magnitudes of the lead-lag loads are very sensitive to changes in the drivetrain properties as well as changes in the nb/rev excitations. The accurate modeling of these nb/rev excitations, e. g. by airloads, is essential to capture changes in the nb/rev dynamic response that are caused by the drivetrain. Therefore, including the drivetrain in the structural model may only be useful if the fidelity of other models is increased simultaneously.
Carbon Fiber Roving for Magnet Retention on BLDC Motors
Authors:   Windings Inc., Alderks Blaine
Published: September 2024

This white paper discusses the application of carbon fiber roving for rotor magnet retention in high-performance Brushless DC (BLDC) motors, focusing on sectors like Advanced Air Mobility and motorsports. Highlighting the benefits of carbon fiber's tensile strength, thermal characteristics, and electrical resistivity, it compares thermoset and thermoplastic matrices, analyzing their trade-offs. It delves into manufacturing methods, particularly the advantages of in-situ winding of Hexcel® HexTow® IM7 12k carbon fiber directly onto rotors, versus pre-wound sleeves, emphasizing controlled processes for even stress distribution and preventing failure. Key design factors such as operating speed, temperature, and air gap dimensions are considered to optimize carbon fiber's application. Windings' expertise in fabricating high-tolerance carbon fiber wound rotors is showcased, highlighting its potential to enhance motor power output and offering collaboration for innovative retention solutions in BLDC motors.
Manned-Unmanned Teaming Applied To HEMS Missions: A Path Planning Approach Based On The Pilot's Workload Assessment
Authors:   Politecnico di Milano, Roncolini Francesca , Quaranta Giuseppe
Published: September 2024

This paper presents a path planning concept based on the Manned-Unmanned Teaming (MUM-T) between the helicopter and a drone. The drone flies ahead of the helicopter to detect possible unexpected obstacles in the mission area and sends the data to the helicopter. The path of the helicopter is automatically replanned to avoid the meteorological and physical obstacles detected by the drone. The path planning is based on the Rapidly-exploring Random Tree (RRT) and the Bidirectional Rapidly-exploring Random Tree (BiRRT) algorithms. The reference trajectory is planned by means of the RRT algorithm and the replanning is performed with the BiRRT. The node connection is realized with the Dubins curves, that force the path to comply with the prescribed limitations on the helicopter's roll angle and flight path angle. The Savitzky-Golay filter is used to smooth the trajectory achieving curvature continuity. A closed-loop simulation model containing the dynamics of the pilot is used to evaluate the feasibility of a candidate trajectory basing on the pilot's workload. The pilot's dynamics is modeled through the frequency-based multi-axis Hess model. A workload assessment method is proposed basing on the aggression factor, which depends on the time histories of the control inputs. The workload quantitative assessment is carried out by comparison with the aggression factor on a "simple" manoeuvre, the spiral.
Comparison of Electronic Chip Detectors and Online Debris Monitoring for Rolling Element Bearing Spall Diagnostics
Authors:   Gastops Ltd., Mahmoud Hassan , Oszmian Adam , Rodger Steve
Published: September 2024

Wear debris monitoring and analysis is a common practice for the condition assessment of engine and transmission health. Oil debris monitoring (ODM) and electronic chip detectors (ECD) are two common methods deployed for continuous monitoring of oil wetted component health in-flight. This study evaluates the diagnostic performance of the two sensing technologies within controlled rolling element bearing (REB) fault experiments. Progressive visual inspection of the REB spall progression through failure provided a ground truth against which both systems could be compared. Quantifiable metrics of reliability, diagnostic accuracy, provided maintenance interval were defined to create a framework for condition-based maintenance (CBM) program decision making. In summary, it was found that the ODM sensor system provided earlier fault notice, but more so, vastly outperformed the ECD in reliability and avoidance of false positives.
Development Flight Test Campaign for Automatic Flight Control System
Authors:   Turkish Aerospace Industries, Tirman Kaan , Çetin Derya , Gültekin Oğuzhan , Türe Umut
Published: September 2024

T-625 Gökbey is a light utility helicopter developed by Turkish Aerospace Industries since 2013. For T-625, automatic flight control system performance evaluation and development test campaign was conducted. In this paper, test campaign is investigated thoroughly. To assess and quantify the automatic flight control system performance and handling qualities, various different metrics and specifications were selected. This metrics covered both time and frequency domains. After metric selection, a set of test points were created. Most of the test points required delicate piloting and were easy to fail. Furthermore, a large flight envelope in terms of altitude and air pseed was needed to be covered. Hence, both test point number and required flight time estimates were very large. Hence, to not further increase flight time and need of test point repetitions, various different precautions were taken, such as using computer generated sweeps. While conducting tests, altitude kept constant while speed envelope tested. Then, altitude were changed to a new value and speed envelope is tested again. After each sortie, flight data were analyzed whereas control parameter updates were performed after finishing tests for all airspeed values for an altitude. After control parameter updates, validation tests were done to ensure that updated parameters provided expected performance. At this point, most of the test campaign is done and selected specifications were met for almost all the tested flight envelope.
Investigation of Drive Train Coupled Torsional Stability Analysis Methodology for Tiltrotor: the Helicopter Mode Case
Authors:   Leonardo Helicopters S. p. A., Viganó Luca , Punzi Claudio , Riccardi Fabio , Poracchia Federico
Published: September 2024

Coupled powerplant and rotorcraft flight dynamics simulations are commonly carried out in the non-linear time-domain framework (e.g. for pilot-in-the-loop handling qualities assessments), although these integrated models are generally not fully accurate from drivetrain dynamics perspective. Nevertheless, there is interest to verify that usual assumption of decoupled torsional stability (including rigid drivetrain analysis) and aircraft rigid body stability is valid, and up to what extent. The process described in the paper entails the automatic assembly of relevant subsystems (bare aircraft flight dynamics, Flight Control System including fly-by-wire actuation, sensors, and Control Laws software, drivetrain dynamics, powerplant dynamics) state space matrices through a Company developed Matlab toolbox. The proposed approach is control system design oriented, i.e. it does not require detailed flexible multibody modelling of the entire aircraft including dynamic systems and it is a natural extension of the process generally carried out by Control Laws and Flight Mechanics discipline for rigid-body stability assessment. The paper specifically addresses, as case study, the coupled torsional dynamics analysis of Next Generation Civil Tiltrotor Technology Demonstrator (NGCTR-TD) in Helicopter configuration. The NGCTR-TD project is developed under the EU Clean Sky 2 program for defining novel technology for future civil Tiltrotor platforms. The proposed coupled torsional stability modelling process is described, and the main outcomes valid for NGCTR-TD trimmed in hover and near-hover conditions presented. It is shown that the proposed methodology provides consistent outputs against the original NGCTR-TD linear stability results (from individual flight dynamics and drive system models). Analysis of Modal Participation Factors is used to quantify the coupling existing between drive system and flight dynamics state vectors, in nominal and failure conditions (Inter Connect Drive Shaft failure).
Performance Analysis of a High-Speed Tiltrotor Aircraft Featuring VerdeGo Aero's VH-5 Hybrid-Electric Turbofan Engine
Authors:   VerdeGo Aero, Roiati Riccardo , Rice Tyler , Steinfeldt Brock , Nitzsche Jasper , Anderson Richard
Published: September 2024

In the pursuit of High-Speed Vertical Takeoff and Landing (HSVTOL) platforms, VerdeGo Aero offers its VH-5 hybrid-electric turbofan as the answer to missions requiring high power, vertical lift, and jet-like speeds. To evaluate the possibility of designing a real HSVTOL aircraft around VerdeGo's VH-5 powerplant, this paper investigates the size and expected performance of a militarized spinoff of NASA's Class B, High-Efficiency Civil TiltRotor (HECTR) concept, which has been renamed the VerdeGo Hybrid-Electric Combative TiltRotor, or "VHECTR" for short. Through an in-depth conceptual weight buildup of four commonly proposed tiltrotor architectures, this paper suggests that an entirely new, turbofan-driven propulsion system is needed if modern day HSVTOL demands are to be met. Hence, a separate, yet more conventional "Modified HECTR" tiltrotor configuration is considered to contest the proposed, VH-5 powered VHECTR concept. However, the results of a full-scale aircraft comparison, aerodynamic analysis, and mission analysis alongside the V-22 Osprey indicate the VHECTR concept is more HSVTOL mission capable with greater time and fuel savings than any advanced tiltrotor system to date.
Automatic Flight Control Modes for Pilot Assistance During Helicopter Shipboard Operations
Authors:   German Aerospace Center - DLR, Kalra Arti ,   French Aerospace Lab - ONERA, Binet Laurent
Published: September 2024

The inherent complexities of maritime environments make the helicopter shipboard operations exceptionally demanding to the pilots. This paper presents current research on development of a combination of different advanced control modes to automatize different parts of a ship deck landing maneuver in the maritime simulation environments of both DLR (German Aerospace Center) and ONERA (The French Aerospace Lab). The proposed advanced control modes involve ship relative Velocity Hold and Position Hold capabilities for pilot assistance and further enhancing the safety levels of the shipboard operations. Control augmentation is based on a model following control system featuring a translational rate command at DLR, however at ONERA a feedforward control strategy is used. The paper describes the simulation setup of a helicopter-ship dynamic interface, test methodologies and evaluation methods at both DLR and ONERA. Simulation results demonstrate an evaluation and comparison of the implemented control augmentation for different helicopter types namely, an EC135 at DLR and an EC225 at ONERA for shipboard operations.
Dynamics of a Variable Speed Hybrid-Electric Helicopter Propulsion System
Authors:   University of Tennessee, DeSmidt Hans , Ai Zhisheng
Published: September 2024

In this paper, a comprehensive dynamic simulation of a parallel hybrid gas-electric single main rotor helicopter involving a motor/generator (MG) pair and a differential planetary gear transmission (PGT) arrangement forming an electronic continuously variable transmission (E-CVT) was performed. This notional hybrid electric helicopter was sized based on a retrofit of a dual engine, 10000 lb, 2500 Hp class helicopter. The total weight added by the electric components was 182 lbs which increased the propulsion system weight from 1184 to 1366 lbs. The simulation results found that at 110 kts cruise, the hybrid electric system enabled a 27% reduction in main rotor rpm which resulted in an 18% reduction in the fuel burn rate. It is concluded that use of an E-CVT parallel hybrid propulsion system offers potential for increased flight range and reduced fuel consumption in medium to large-scale helicopter applications.
Maturing Scalable Model-Based Acquisition
Authors:   Dassault Systems, Thurston Gerrett ,   STC, Engle Jake ,   Zaltana Consulting, Fowler Kevin , Cotan Andre , Kolligs Jason
Published: September 2024

This paper describes both technology and methods when integrated into a holistic acquisition approach stands to affect acquisition success. Mission engineering, drives the ability to use innovation-driven outcome approaches with an end-effects delivery focus; crafting the necessary mission capabilities working back into the development of systems and technologies. Developing product line-centric products enables improved system engineering of more holistic product line scope against Business, Mission, and Stakeholder needs, applying product line scoping against both Market and Mission Segmentation. Organizational operational effectiveness in shifting to a product line approach to product development.
A New Perspective on Coupling Numerator Models
Authors:   German Aerospace Center - DLR, Döring Frederik
Published: September 2024

Coupling numerator models are a well-established tool for predicting the closed-loop dynamics of multiple-input multiple-output systems. They describe the input-output dynamics of the open-loop path in a partially controlled system given tight controls and thus may serve as an approximation of the actual dynamics "seen" by the single-axis controller in a controlled multiple-input multiple-output plant. Such models can therefore be employed for a decentralized initial design of multivariable controllers. This paper presents a new, unifying approach for the computation of such constrained input-output dynamics. Connections to existing methods in the literature are established and a general procedure for state-space calculations is given. The use of coupling numerator models for controller design is motivated and different decoupling structures are discussed. The controller design is illustrated using a coupled high-order helicopter model.
Flight Testing of Explicit Model-Following Trajectory Control System for Lift-Plus-Cruise and Tilt-Wing Configurations
Authors:   Auburn University, Comer Anthony , Chakraborty Imon , Kovryzhenko Yevhenii , Taheri Ehsan , Putra Stefanus , Bhandari Rajan , Kunwar Bikash
Published: September 2024

The ongoing development of numerous novel vertical takeoff and landing configurations necessitates flight control system design that enables the Simplified Vehicle Operations paradigm. This paper shows flight test results for one subscale lift-plus-cruise and one tilt-wing configuration employing such a flight control system architecture. Pilot inceptor inputs are used to synthesize trajectory commands that are processed by a full-envelope trajectory control system that generates propulsor thrust commands, a wing angle command, and attitude and rate commands for linear quadratic integral and explicit model-following inner-loop control systems. Commonalities and differences in the flight control implementation for the two configurations are highlighted. Results are shown for both configurations subject in manually piloted flights. The flight test results demonstrate that the flight control system designs allow a minimally trained operator to operate the two flight test vehicles safely and proficiently.
Vortex Ring State Prediction Using a Mid-fidelity Comprehensive Approach
Authors:   University of Maryland, Cocco Alessandro ,   Politecnico di Milano, Gentile Federico , Dall'Ora Matteo , Quaranta Giuseppe
Published: September 2024

Vortex Ring State (VRS), a hazardous condition during rotorcraft descent, appears more problematic for high disc loadings aircraft like tiltrotors and eVTOL multi-rotors. Traditionally, semi-empirical models were calibrated using flight data to predict VRS. Recent advancements in modeling techniques and computational resources made it possible to predict the VRS by solving Navier-Stokes equations via Eulerian (VTM) or Lagrangian (VPM) approaches and conventional Computational Fluid Dynamics (CFD). The study aims to validate the capability of the open-source VPM code DUST to predict VRS boundaries and rotor loads and support the development of appropriate simulation models for the assessment of aircraft handling qualities. Finally, the effect of the rotor dynamics will be introduced to better simulate and design an escaping VRS strategy to enhance the correct training to increase future rotorcraft safety.
Identification of Weak Cell Blocks in Electric Aircraft Battery Packs
Authors:   Astrolabe Analytics Inc., Masse Robert , Bonageri Shrilakshmi , Shea Dan , Beslow Lucas
Published: September 2024

Electric aviation represents a new arena for battery engineering and development. In contrast to automotive applications, the electrification of aviation and aerospace is both less mature and requires higher safety and performance regulations. This work addresses a first step towards the development of standards and algorithms for measuring remaining useful energy for the battery system. Battery pack flight test data from 134 tests and two different manufacturers was analyzed to determine the weakest cell blocks in the pack, defined as cell blocks having the lowest voltage at the end of the test. It was found that the maximum initial voltage and voltage integral were two features with predictive power. Using the first five minutes of flight test data, accurate predictions were made ~85% of the time, in contract to the status quo where ~30 minutes of flight test data may be required. Sources of error and pathways to improve upon this result are discussed, such as improving data logging, adding additional logic to handle well-balanced packs, and engineering new voltage features with greater predictive power. It is possible to increase the accuracy beyond 95% this way. Future work will build on this to develop algorithms and standards for on-line fuel gauging for electric aircraft.
Data-Driven Probabilistic Health Monitoring on a Hexacopter via Time-Series Assisted Machine Learning Methods
Authors:   Rensselaer Polytechnic Institute, Huang Shinan , Zhu Jingxi , Zhou Peiyuan , Vining Cassie , Kopsaftopoulos Fotis
Published: September 2024

This study presents a statistical approach for detecting and estimating damage to multicopter propellers through a comprehensive probabilistic model. The methodology is derived from model-based analysis and applied within the time series statistical techniques. This research accounts for uncertainties in the estimation process and offers confidence intervals for assessing the extent of damage to the propellers. The framework employs functionally pooled (FP) models characterized by parameters that depend on damage sizes, proper statistical estimation, and decision-making schemes. The validation and assessment are assessed via a hexacopter flying in circles with a constant velocity and altitude under turbulence. The damage size ranges from healthy to 10 mm. The method achieves fast damage detection and precise magnitude estimation based on a segment of a single measured signal obtained from aircraft sensors during flight.
CH-53K Aircraft Performance Verification
Authors:   Sikorsky A Lockheed Martin Company, Pollack Michael ,   NAVAIR, Steward John , Neiswonger Jacob , Gerardo Michael , Klimchenko Vera , Regan Marc
Published: September 2024

The CH-53K® King Stallion™ is the most advanced heavy lift helicopter developed by Sikorsky, a Lockheed Martin Company, to address the requirements of the United States Marine Corps. The aircraft was designed to support missions with a maximum design gross weight of 88,000 lbs and can carry external loads up to 36,000 lb. Performance flight tests for the CH-53K® have been completed as part of its System Design and Development (SDD) phase. Tethered hover and level forward flight performance measurements have been acquired that are used as a basis for Naval Air Training and Operating Procedures Standardization (NATOPS) flight manual performance charts. They were also used in the Key Performance Parameter (KPP) verification analysis, demonstrating that the CH-53K® exceeds its KPP for mission effectiveness. In addition to overview descriptions of the performance flight test program, the test results are herein compared with predictions from aircraft performance modeling tools that were largely based on earlier comprehensive model scale hover stand and wind tunnel tests. In some cases, the flight test results dictated that adjustments be made to the aircraft performance prediction tools so they consistently represent the overall vehicle flight performance characteristics. Recent computational fluid dynamics (CFD) simulations were employed to assist with the overall understanding of the complex aerodynamic flow field in both hover and forward flight. This includes modeling simulations using CREATE-AV™ Helios full-aircraft tool for rotor performance and interactional effects and the Simcenter STAR-CCM+ tool for isolated fuselage drag and fuselage variations. The insights gained from the CFD analysis, such as parasitic drag contributions, main rotor and tail rotor interactions, and other aerodynamics interactions, were used to make appropriate input adjustments to the aircraft performance modeling tools for enhanced correlation to the flight-test results.
An Indirect Stability Method Applied to Whirl Flutter using Computational Fluid Dynamics Actuator Disc Models
Authors:   ATA Engineering Inc., Reveles Nicolas , Weiss Adam , Shah Parthiv
Published: September 2024

A recently developed indirect eigenvalue method is applied to propeller whirl flutter stability using computational fluid dynamics. The use of computationally efficient actuator disc models is compared to actuator blade and wall-resolved models. Actuator disc and blade results are confirmed to be both mesh and time-step independent. Actuator disc models produce stability results that closely emulate analytic quasi-steady approximations, whereas actuator blade models are observed to most closely resemble analytic unsteady approximations. The wall-resolved model of the propeller produces the most accurate results but is between three to four orders of magnitude more computationally expensive than the actuator disc model. It is concluded that actuator disc models could be used in concert with the indirect eigenvalue method to compute eigenvalues of low-frequency modes with reasonable accuracy, especially in situations with complicated fluid dynamics and disparate time scales where wall-resolved models are currently computationally infeasible.
Analysis of Flap-Lag-Torsion Aeroelastic Stability at High Advance Ratios
Authors:   University of Maryland, Fishman Spencer , Chopra Inderjit
Published: September 2024

The aeroelastic stability of rotor blades in the flap, lag, and torsion degrees of freedom is analyzed in preparation for high-advance ratio wind tunnel testing of Mach-scaled rotors. A wide range of advance ratios (0 ≤ μ ≤ 3) are evaluated for articulated and hingeless rotor configurations. Linearized equations of motion in the rotating frame are derived, which consider periodic coefficients, reverse flow, pitch-flap and pitch-lag coupling, and control inputs. The steady state trim is compared with wind tunnel data. Floquet theory is used to evaluate the stability of the equations of motion in response to perturbations from trim. Results are compared to past analyses and expanded to higher advance ratios. Damping and frequency response behavior are evaluated, and rotor stability boundaries are presented.
Identification of Higher-Order Rotor Flapping Dynamics Model Structures using Explicit Soft Inplane Hingeless Rotor Hub State Measurements of the NRC Bell 412 Advanced System Research Aircraft
Authors:   National Research Council of Canada, Alexander Marc
Published: September 2024

NRC developed a higher-order mathematical model structure of coupled rotor-body flapping dynamics for inflight control applications. The hybrid (rigid body fuselage state and rotating hub rotor state) 8DOF model was developed utilizing explicit measurements from a novel rotor hub state measurement system enabling estimation rotor blade dynamics. The method identified second-order rotor flap dynamics, attitude-rate and rotor flap dynamics response correlation, and response lead of rotor flap dynamics over rigid body dynamics. Reducing implementation resource burdens of past approaches, this novel rotor state measurement and modelling methodology may prove useful in applied development cycles across a spectrum of needs for articulated (helicopter) and non-articulated rotor (tiltrotor, eVTOL) aeromechanics, modelling, monitoring, and operations.
Probabilistic Trajectory Analysis of Debris Items for Crash Investigation
Authors:   Sikorsky a Lockheed Martin Company, Coleman Dustin , Bowles Patrick , Barrett Arild , Casanova Javier
Published: September 2024

Air safety investigators must seek out all available sources of evidence from an aircraft crash incident in order to make informed root cause determinations. This is especially important when the incident aircraft was not equipped with flight and voice data recorders. Previous investigations have utilized trajectory analysis methods as a technique to determine where debris items may be found on the ground after an in-flight breakup. Alternatively, if the ground placement of debris items is known, then the airspeed and heading of the aircraft may be back-calculated. In this paper, a probabilistic trajectory analysis is developed to infer crash debris initial conditions at time of impact. Digital methods including computational fluid dynamics have been employed to calculate debris item aerodynamic coefficients and probabilistic sampling techniques to determine a likely range of initial angles and initial velocities. Finally, two example cases are presented to illustrate application of the technique and its utility for design making with respect to crash investigation.
Suffering in the doctor-patient relationship: Medicine as the science of suffering
Authors: Brera Giuseppe R.
Published: September 2024

In medical science today, much attention is paid not only to what can be experimental, reproducible, observable or describable in data, but also to what concerns the subjectivity of the physician and the patient. We thus break away from a positivistic conception that does little to illuminate our path in this order of phenomena to enter with an observation that wants to be phenomenological into what seems to best characterise the meaning of Medicine and that from bio-science reveals it to us as anthropo-science, a science of man-for-man.
Consent of the sick ‘who cannot consent’ (elderly and children) in international human rights law
Authors: Scalabrino Spadea Michelangela
Published: September 2024

Not available.
Sedentarism and Chronic Health Problems
Authors: Goyal Jyoti , Rakhra Gurseen
Published: September 2024

Increased mechanization and technological advances have simplified our lives on the one hand and increased sedentary behaviors on the other hand, paving the way for emerging global health concerns, i.e., sedentarism, which could be the leading cause of all major chronic health problems worldwide. Sedentarism is a habitual behavior of choosing and indulging in low-energy expenditure activities (≤1.5 metabolic equivalents), such as chairtype (sitting, studying, traveling) or screen-type activities (TV, computers, mobile). With technological advancements, there is a significant transition in the lifestyles of people from being active (walking) to being more deskbound (sitting). Prolonged sitting can have unintended consequences for health with sitting time >7 h/d, leading to a 5% increase in all-cause mortality with each additional hour spent sitting (i.e., +7 h/d), while considering physical activity levels. This review will highlight how sedentarism is emerging as a major risk factor for the rising incidence of non-communicable diseases, especially among young adults and adults. Chronic diseases, such as obesity, diabetes, coronary heart disease, and cancer, are the leading causes of death worldwide. Hence, there is an urgent need for collective action to mitigate the burgeoning public health crisis posed by sedentarism in the 21st century. This paper intends to set in motion a call for all policymakers and public health professionals placed nationally or internationally to reach a consensus on ending sedentarism and provide viable resolutions for effective management of excessive sedentary behaviors and healthy adoption and maintenance of active lifestyles among individuals of all age groups.
e Vehicle Cooling System Approach for Off-Highway Machines
Authors: Dewangan Nitin , Joshi Prathamesh
Published: September 2024

Traditionally the off-highway vehicles like tractors, construction and road building machinery have been using diesel engine as the power source. In recent times there has been more and more focus to adopt either all electric or hybrid powertrain for off highway vehicles to reduce the carbon footprint. The e machines involve various electrical components like Battery pack, On board Charger, DC/DC converter, Inverters, Traction motors, PTO Motor and e transmission. The cooling requirement and the fluid temperature limits for these electric components is different compared to the conventional engine. In most of the cases the battery cell temperature needs to be around 20 to 30 °C which in most cases would be below the ambient temperature. Whereas the hydraulic oil temperature can be as high as 100 °C. The hydraulic oil temperature can be maintained using a separate air-cooled hydraulic oil cooler or a plate cooler. Therefore, the cooling system for the e components will be unique and different compared to the conventional diesel engines. The cooling system for a Battery electric vehicle (BEV) involves multiple cooling loops due to difference in fluid temperature limit. A typical Battery electric vehicle (BEV) may involve the Water Ethyl glycol loop, Battery loop, HVAC loop & e- transmission loop. This study talks about the approach that has been followed to design the cooling system for the all-electric e machines using 1D KULI simulations.
Transient Multi-Dimensional Conjugate Heat Transfer (CHT) Simulation of an Oil-Cooled Automotive Electric Motor Operated in a Drive Cycle
Authors: Pasunurthi Shyam Sundar , Srinivasan Chiranth , Chaudhari Nirav , Maiti Dipak
Published: September 2024

In an electric vehicle, nevertheless, the primary component is the electric motor (e-motor). Understanding the thermal performance of the e-motor is paramount in ensuring the overall efficient functioning of the electric vehicle. Usually, the high-power e-motors are oil-cooled due to relatively high thermal loads. The e-motor thermal response is monitored under extreme conditions like warm-up cycle allowing the vehicle to move in a circular track multiple-times. In this condition, the vehicle undergoes heavy lateral and longitudinal accelerations, the e-motor speed varies and the consequent thermal losses from the rotor and stator components also vary accordingly. Importantly, the cooling oil sloshes rigorously that affects the heat removal capacity of the oil. The advanced capabilities of Computational Fluid Dynamics (CFD) allow to virtually simulate the warm-up cycle and capture the extremely transient thermal response of the e-motor in the given conditions.

In the current effort, a general purpose 3-D CFD software, SimericsMP+ from Simerics, Inc. is used for the virtual simulation. A Conjugate Heat Transfer (CHT) model of the e-motor is created with all the important components such as windings, rotor, stator laminate, endrings, gears etc. The multiphase Volume of Fluids (VOF) approach is used to capture the oil flow across the components. A novel CHT approach is devised that allows to simulate the transient fluid-solid coupled simulation for a rotation of the vehicle in the circular track and the later solid alone heat transfer is simulated with a convective heat transfer boundary condition derived from the coupled simulation. The approach proved to be promising in terms of the accuracy of the temperature prediction on the windings compared to the test and the overall simulation time is acceptable to conduct multiple design studies of the e-motor.