bluuebunny/crossref_metadata_2025 huggingface dataset:
A Case Study of Developing Educator Digital Competences With Serious Game Design
Authors: Zapušek Matej
Published: July 2023

The chapter presents a case study on the implementation of the SADDIE method, combined with the utilization of a project management tool, in the collaborative learning process of developing an educational computer game to enhance educator-specific digital competences defined in DigCompEdu. The activities in each phase of the method are presented throught the work result of three groups of students each developing their own educational game on a selected topic from computer science. Authors also provide a detailed insight into how students utilized the selected project managament tool to improve the game development process. Furthermore, an analysis is conducted to determine how the selected project management tool enhances the acquisition of specific digital competences within each of the six competence areas defined in DigCompEdu. The results demonstrate that the project management tool significantly improves the learning process in each phase of the SADDIE method and effectively supports the acquisition of educator-specific digital competencies.
New Drug Discovery
Authors: Yingngam Bancha
Published: July 2023

The field of drug discovery is continually advancing with the emergence of new technologies and scientific developments. Moreover, there is a recent growing interest in exploiting natural products as a potential source of novel drug leads. This chapter provides an overview of the current state of new drug discovery, with a specific focus on natural products and integrative medicine. The drug discovery process is discussed, including target identification, lead generation, lead optimization, and preclinical and clinical development, along with the challenges associated with each step and potential solutions. The use of natural products as a source of novel drug leads is explored, including examples of natural products that have been transformed into drugs and current efforts to discover new natural product-based drugs. Furthermore, the chapter proposes valuable insights into the challenges and opportunities in this field, as well as potential solutions for discovering and developing new drug leads.
Plasmacytoid Dendritic Cells Enhance T-Independent B Cell Response through a p38 MAPK–STAT1 Axis
Authors: Chen Hsin-Hsiang , Yu Ya-Ru , Hsiao Yu-Ling , Chen Shun-Hua , Lee Chien-Kuo
Published: July 2023

TLR signaling in B cells triggers their activation and differentiation independent of help from T cells. Plasmacytoid dendritic cells (pDCs) cooperate with B cells to boost TLR-stimulated T-independent humoral immunity; however, the molecular mechanisms remain elusive. In this study, we demonstrate that in the mouse system, the adjuvant effects of pDCs also occurred following challenge with pathogens and that follicular (FO) B cells were more sensitive to pDC-induced enhancement than were marginal zone (MZ) B cells. Moreover, pDCs migrated to the FO zones and interacted with FO B cells upon stimulation in vivo. CXCL10, a ligand for CXCR3 expressed on pDCs, was superinduced in the coculture system and facilitated the cooperative activation of B cells. Moreover, pDCs also promoted TLR-stimulated autoantibody production in FO B and MZ B cells. Ingenuity Pathway Analysis and gene set enrichment analysis revealed that type I IFN (IFN-I)–mediated JAK–STAT and Ras–MAPK pathways were highly enriched in R848-stimulated B cells cocultured with pDCs compared with B cells alone. Whereas IFN-I receptor 1 deficiency reduced pDC-enhanced B cell responses, STAT1 deficiency displayed a more pronounced defect. One of the STAT1-dependent but IFN-I–independent mechanisms was TLR-induced STAT1-S727 phosphorylation by p38 MAPK. Serine 727 to alanine mutation attenuated the synergism between pDCs and B cells. In conclusion, we uncover a molecular mechanism for pDC-enhanced B cell response and define a crucial role of the IFN-I/TLR–mediated signaling pathway through a p38 MAPK–STAT1 axis in controlling T-independent humoral immunity and providing a novel therapeutic target for treating autoimmune diseases.
Flight Dynamics and Control of an eVTOL Concept Aircraft with a Propeller-Driven Rotor
Authors:   Georgia Institute of Technology, Saetti Umberto ,   Pennsylvania State University, Enciu Jacob , Horn Joseph
Published: July 2023

The objective of this investigation is three-fold. First, to assess the flight dynamics of an electric Vertical Take-Off and Landing (eVTOL) concept aircraft with a propeller-driven rotor. Second, to develop a Stability and Control Augmentation System (SCAS) for this concept aircraft. Third, to verify the potential safety benefits of the concept aircraft by analyzing the autorotation performance following a total loss of power. The paper begins with a description of the simulation model, including a detailed discussion on the inflow model of the propellers that drive the main rotor. Next, the flight dynamics are assessed at hover and in forward flight. A SCAS based on Dynamic Inversion (DI) is developed to provide stability and desired response characteristics about the roll, pitch, yaw, and heave axes for speeds ranging from hover to 80 kts. Additionally, an RPM governor is implemented to hold the main rotor angular speed constant at its nominal value. Finally, simulations that make use of the SCAS are performed to analyze the autorotation performance following total loss of power.
Design and Evaluation of Control Laws for the CH-53E Low Speed Precision Control System
Authors:   US Navy NAVAIR, Rhinehart Matthew , Brymer Robert , O'Neill Eric
Published: July 2023

The United States Marine Corps often operate their helicopters in austere environments where degraded visual environments (DVE) such as brownout are regularly encountered. DVE significantly increase the risk to operations and have led to many mishaps across the Department of Defense. In response, engineers from the United States Navy are designing a system to augment the legacy flight control system (FCS) on the CH-53E. The system is designed to preserve the legacy FCS functionality to limit the impact on the current platform airworthiness and reduce developmental flight test. The Low Speed Precision Control (LSPC) system provides decel-to-hover with position hold functionality, allowing the pilot to modulate command references via trim beepers, cyclic fly through, and trim release. A piloted simulator test was performed with three test pilots to evaluate the handling qualities with and without LSPC engaged, in several fleet representative conditions. LSPC was found to reduce workload marginally in good visual environments and in low light conditions; however more substantial reductions were shown for approaches into brownout conditions. In addition, LSPC was shown to significantly reduce lateral drift during final approach into brownout and lateral and longitudinal drift in a hover. Inherent system bandwidth limitations were found to degrade the performance of the system for anything more than moderate control inputs. Overall, LSPC was successful in augmenting fleet representative approaches in the simulator for degraded visual environments.
CH-53K Control Laws: Improved Safety and Performance in the Degraded Visual Environment
Authors:   Naval Air Welfare Center, Engel David ,   Sikorsky a Lockheed Martin Company, Spoldi Steven , Cofelice Chris , Faynberg Alex
Published: July 2023

A core mission of the CH-53K involves flying in severe brownout conditions, which increases pilot workload and can reduce mission success rates. With state of the art Fly by Wire capability, the CH-53K leverages the computational power of a flight control computer to provide higher order control modes which reduce pilot workload in all degraded visual environments such as brownout. The preliminary design of the flight control system included the inceptor system and low speed control architecture, which created an expansive design space. High fidelity simulations, cockpit mockup, and use of the NRC Bell 412 in-flight simulation Advanced Systems Research Aircraft surrogate aircraft allowed for a comprehensive development environment to narrow down to final control system design. The final design of the low speed maneuvering provided a command strategy similar to translational rate commend yet provided an approach profile that more closely replicated a piloted approach to a landing zone in DVE. This paper provides details of the system design along with initial results from flight test.
Flight Mechanics of the RACER compound H/C
Authors:   Airbus Helicopters, Huot Remy , Eglin Paul
Published: July 2023

Research on high speed helicopters has gained a new momentum in the last two decades. In the EU H2020 / Clean Sky 2 Program, Airbus is taking advantage of numerous partners across Europe to develop a new technology demonstrator named RACER, playing the cost-efficiency and simplicity cards.
This paper presents the Flight Mechanics of this new compound helicopter technology demonstrator. Its excellent stability characteristics resulting from the implementation of optimized aerodynamic design features are introduced. More specifically, the results of the wind tunnel tests held in Filton UK are detailed, highlighting the benefits of the boxwing, the H-tail and the pusher configuration of the propellers.
In the second part of this paper, the light is shed on the piloting aspects and the various similarities with conventional helicopters that facilitate the flight crew adaptation. The illustrated propellers management renews the successes of the X3 demonstrator and is endowed with new functionalities, including a full domain and low workload autorotation procedure.
Real-Time Nonlinear Model Predictive Control of a Helicopter in Autorotation
Authors:   Georgia Institute of Technology, Eberle Brian , Rogers Jonathan
Published: July 2023

Autorotation is a challenging maneuver during which pilot workload is high. Consequences of an improperly performed maneuver are potentially catastrophic, thus partial automation and/or pilot cueing can potentially be used to reduce pilot workload and increase the probability of a successful landing. This paper describes the development of a nonlinear model predictive control (MPC) scheme and a trajectory generation method that can be used to perform autorotations autonomously, or in development of pilot aids. The proposed control scheme offers potential benefits over existing methods by balancing simultaneous control objectives of trajectory tracking and rotor speed regulation. Results are presented for a six-degree-of-freedom simulation of the AH-1G aircraft. The results are compared to a traditional cascaded PID control scheme to demonstrate the benefits of the MPC algorithm. A trade study is presented in which the target landing point is varied to quantify the benefits of the MPC over a range of landing profiles.
Development and Assessment of Flight Lead Cue for Real-time Guidance and Pilot Workload Reduction in Rotorcraft Shipboard Recovery
Authors:   Georgia Institute of Technology, Comandur Vinodhini , Feigh Karen , V. J. , Walters Robert
Published: July 2023

Helicopter shipboard launch and recovery are some of the most challenging operations to date, owing to the pilot workload associated with the tasks. A variety of environmental conditions such as random deck motion, heavy sea states and unsteady aerodynamic interactions can be attributed to the same. This paper highlights the development and assessment of a visual flight lead cue for real-time guidance and pilot workload reduction. For a chosen approach-turnland maneuver, the pilot workload is assessed using data from pilot-in-the-loop (PIL) flight simulations. Quantitative metrics based on Time-Frequency Representation (TFR) are used to evaluate pilot workload and the analysis of workload in the presence and absence of the cue is presented. Furthermore, the deviations from the desired path are studied using root-mean-square error (RMSE) for the cue on/off cases. The relation between pilot workload and path following is analyzed to determine the efficacy of the cue provided.
Working Group on eVTOL Noise Assessment
Authors:   Josephson Engineering Inc., Josephson David
Published: July 2023

Acceptance of close-proximity eVTOL aircraft depends on public perception that they are quiet in relation to the environment. When they are audible, their influence on community soundscapes must not be intrusive. To solve for that, measurement of "quiet" is needed using a physiological model of hearing rather than a sound pressure measurement intended for entirely different applications. While we are starting with baseline noise metrics using earlier methods, we propose a cooperative effort to coordinate development, testing and education about techniques that correlate better with perception of quiet. Two major differences are proposed between current practice and future methods: measure vehicle loudness rather than sound pressure, and measure operations with respect to ambient rather than to meet an arbitrary level for a given land use. These are not new concepts, but require computational resources that until recently were too expensive to be practical.
A Life-Cycle Economic Study of eVTOL Air Taxi Service in the U.S. North-East Region
Authors:   PRICE Systems LLC, Sirirojvisuth Nate ,   Georgia Institute of Technology, Justin Cedric ,   Jaunt Air Mobility LLC, Briceno Simon
Published: July 2023

The Urban/Advanced Air Mobility (UAM/AAM) transportation concept has been studied and shown to offer advantages in travel time-savings to individuals over the automobile, mass transit, and in many cases, commercial air transport alternatives. This paper presents a study of this new market using a parametric approach that accounts for the performance of Electric Vertical Takeoff and Landing (eVTOL) aircraft, takeoff and landing infrastructure (vertiports), and the demand for ridership given a ticket price and time saved. One of the key mode choice drivers in switching from existing transportation options to an AAM service is the value gained in saving time, which is also tightly correlated with people's income level. The analysis framework can facilitate market feasibility analysis by considering various scenarios and constraints. The results suggest that near-term profitability is possible even though vertiport throughput capacities are limited by existing footprint and operational constraints. Vertiport expansion can increase throughput and demand up to a point of maximum aircraft utilization. This new limit is due in part to ground turnaround time and battery charging requirements. Improvement in battery charging rates or implementing battery swap strategies could dramatically improve profitability while maximizing vehicle utilization. As operations increase to hundreds of flights at certain vertiports, local airspace congestion and aircraft vertiport mobility become the next bottleneck.
Simulation and Characterization of Variable-Voltage Hybrid-Electric Powertrains
Authors:   University of Maryland, Mills Brent , Datta Anubhav
Published: July 2023

A phenomenological simulation for a variable-voltage hybrid-electric powertrain was developed and compared with test data acquired on a 4 hp powertrain to understand the fundamental characteristics of such a system. The powertrain was modeled component by component, and compared with over 500 experimental data points, from the engine alone to the engine generator, to the engine-generator with four distributed propulsors. The principal conclusion of the predictive simulation and the experimental data was that generator voltage is a key parameter that needs careful control relative to rotor speed. For any operating state -- defined by rotor torque and RPM -- the generator voltage should be minimized to minimize engine specific fuel consumption. In general the system is influenced more by the engine generator than electric motors. Hence greater rotor torque and lower rotor RPM is desired. It was found that steady state performance can be confidently predicted with the engine model, if the thermal efficiency is calibrated with engine data. The overall understanding gained from this work is that the optimal operation of hybrid-electric powertrains in VTOL is closely coupled with controls and rotor aeromechanics as well as engine gas dynamics and thermodynamics, but can be captured with relatively simple phenomenological models.
Flight Simulation Assessment of Autorotation Algorithms and Cues
Authors:   University of Liverpool, Alam Mushfiqul ,   Georgia Institute of Technology, Eberle Brian , Jump Michael , Rogers Jonathan
Published: July 2023

Autorotation is a challenging flight maneuver that involves highly coordinated control actions and competing constraints. It is generally recognized that pilot performance in autorotation may benefit from additional cues that improve decision-making as well as timing and coordination of control inputs. This paper describes the development and simulator testing of various pilot cues designed for autorotation. A set of discrete and continuous cues are defined to assist in the initiation and execution of various phases of the maneuver. Furthermore, a reachability cue is created to assist a pilot in rapidly evaluating the vehicle glide distance, thereby facilitating selection of a landing site. Piloted simulated flight trials are performed using various combinations of cues in both good and degraded visual environments. Results are evaluated through assessment of pilot workload as well as quantitative measures of landing performance with and without the cues. Overall, results and pilot evaluations show the potential utility of several of the cueing methods but point to specific improvements to them that may facilitate more precise pilot tracking as well as reductions in task workload.
Pupillometric Workload Measurement in the 360 Degree Integrated Cueing Environment (ICE)
Authors:   Goldbelt Frontier Inc., Hayes Amanda ,   US Army Aeromedical Research Laboratory, Feltman Kathryn , Aura Christopher
Published: July 2023

This study is a part of an ongoing series of studies examining cueing modalities to circumvent the in-flight effects of degraded visual environments (DVEs) in a rotary wing aircraft. The suite of cueing modalities investigated include visual cueing symbology, auditory cueing, and tactile cueing. This study compared the use of combinations of these cueing modalities to find which resulted in the best performance and the least amount of workload required of the pilot. This specific paper focuses on the analysis of pupillometric data collected through video-based eye-tracking to measure cognitive workload. Results are discussed.
Cheeseman Award Paper: Integration and Test of a Degraded Visual Environment System on H145
Authors:   Airbus Helicopters Germany GmbH, Waanders Tim ,   Hensoldt Sensors GmbH, Singer Bernhard ,   Elbit Systems, Shpak Maya , Roth Frank , Fadljevic Dennis , Plorin Jürgen , Hasharoni Omer , Limonad Avishay
Published: July 2023

This paper reports on the integration, test and evaluation of a Degraded Visual Environment (DVE) system installed on an Airbus H145 (BK117 D-2) civil certified helicopter. The DVE system consists of a LiDAR sensor, an EVS camera and a head-tracked helmet mounted display system (HMD) integrated into the onboard HELIONIX® digital avionics suite. The DVE system combines sensor enhanced and synthetic elements of the external scene and provides an accurate representation of the real world for visual reference and safe manoeuvring in DVE. All systems were prototypically integrated into the H145 demonstrator in a serial-like manner, allowing for a potential serialization of the system. Extensive flight trials were conducted focusing on military as well as on civil HEMS missions and were used to verify the intended function and evaluate installed DVE system performance.
The activities described herein are partially performed in the frame of a research project supported by the German Federal Office of Bundeswehr Equipment, Information Technology and In-Service Support (BAAINBw). Between November 2018 and March 2019 the system was successfully deployed in both ground and flight tests.
Aeromechanical Behavior and Aeroelastic Stability of Coaxial Rotors in Hover and Forward Flight
Authors:   University of Michigan, Singh Puneet , Friedmann Peretz
Published: July 2023

Coaxial rotor aeroelasticity is complex due to the counter-rotating wake system, rotor lift offset, periodic blade passage loads, unsteady rotor-wake interactions, reduced rotor speed and stiff hingeless blades. In this study, the aeroelastic stability of a coaxial rotor is examined in hover and forward flight. The rotor wake is modeled with the Viscous Vortex Particle Method, a grid-free approach for calculating vortex interactions over long distances. The spanwise blade aerodynamic loading is calculated using a computational fluid dynamics based reduced order model in attached f low, and the ONERA dynamic stall model in separated flow. Two propulsive trim procedures are developed: one with the propulsor not operating, and the other with the vehicle at level attitude. An aeroelastic stability analysis based on Floquet theory is applied to the periodic system. A novel graphical method is developed to identify coupling between blade modes of the two rotors. The effects of lift offset and advance ratio on the hub loads, inflow distribution and aeroelastic stability are examined to provide an improved physical understanding of the aeroelastic interactions. Results indicate that the blade passage effect is caused by the bound circulation induced inflow. The first and second lag modes are the least stable modes in hover and forward flight.
Modal Elastic Component Enhancements for RCAS
Authors:   Advanced Rotorcraft Technology Inc., Hasbun Matthew , Blumenstein Ryan , Saberi Hossein
Published: July 2023

This paper describes a modal synthesis method for efficiently representing elastic sub-structures within a comprehensive analysis. This capability provides modeling flexibility and can be used to include complex modal sub-structures that would not be easily represented by the elastic beam models available in comprehensive analysis. The modal synthesis method is formulated such that the dynamics of the combined system are preserved, including inertial crosscoupling effects and boundary condition modeling. The application and validity of the modal synthesis approach is demonstrated using the Rotorcraft Comprehensive Analysis System (RCAS). The modal synthesis approach is also evaluated and compared against that of the existing full-vehicle modal approach available in RCAS.
An Evaluation of Finite-State Dynamic Inflow for Usage in Design
Authors:   STC Ames Research Center, Ho Jimmy ,   US Army CCDC AvMC, Yeo Hyeonsoo
Published: July 2023

In an effort to evaluate the accuracy of the finite-state dynamic inflow of Peters and He for use in rotor design, comparisons between dynamic inflow-based calculations and measured test data are presented for a wide variety of single rotor configurations and operating conditions. The quantities compared include rotor performance parameters, blade flap bending moments, blade airloads, and blade pitch angles. The dynamic inflow calculations are performed using the U. S. Army's Rotorcraft Comprehensive Analysis System (RCAS). Rotor performance calculations are mostly accurate prior to stall, except for rotor torque calculations from an individual blade pitch control (IBC) phase sweep. Blade airloads calculations do exhibit the correct dominant features including those from blade tip vortices, but the calculated amplitudes of the wake-induced loading are significantly less than the test data; this leads to significantly lower amplitudes in the flap bending moment response and is problematic for calculating half peak-to-peak values in conditions with significant blade-wake interactions. Blade collective and cyclic pitch angles are reasonably accurate in edgewise flight. Some practical, but not necessarily well-known, aspects of dynamic inflow are also discussed; this includes convergence characteristics with the number of inflow states and providing a formula for determining the number of inflow states.
Lichten Runner-up: A Scalable Time-Parallel Solution of Periodic Rotor Dynamics in X3D
Authors:   University of Maryland, Patil Mrinalgouda , Datta Anubhav
Published: July 2023

A time-parallel algorithm is developed for large-scale three-dimensional rotor dynamic analysis. A modified harmonic balance method with a scalable skyline solver forms the kernel of this algorithm. The algorithm is equipped with a solution procedure suitable for large-scale structures that have lightly damped modes near-resonance. The algorithm is integrated in X3D, implemented on a hybrid- shared and distributed memory architecture, and demonstrated on a three-dimensional structural model of a UH-60A-like fully articulated rotor. Flight test data from UH-60A Airloads Program transition flight C8513 are used for validation. The key conclusion is that the new solver converges to the time-integration solution more than 75 times faster, and achieves a performance of greater than 1 teraFLOPS. The significance of this conclusion is that the principal barrier of computational time for trim solution using high-fidelity three-dimensional structures can be overcome with the scalable harmonic balance method demonstrated in this paper.
Scalable Mesh Partitioning for Large-Scale 3D Finite Element-Multibody Structures
Authors:   University of Maryland, Lumba Ravi , Datta Anubhav
Published: July 2023

A mesh partitioner was developed for large-scale 3D rotor structural dynamic models containing higher-order 3D finite elements and multibody joints. A parallel iterative substructuring solver was built to operate on the partitioned data structures. The algorithmic scalability of the solver was demonstrated on three sample problems of progressively increasing complexity; an elementary uniform beam, a real rotor blade - the NASA TRAM (1/4 scale V-22 model blade), and the full TRAM blade and hub assembly containing four flexible parts connected using six joints. The key conclusion is that a multibody blade and hub assembly can be partitioned and solved in a parallel and scalable manner. Rotor structures of up to 6.6 million degrees of freedom are solved on up to 2048 processors with detailed studies of scalability and efficiency. The uniform cantilevered beam is able to achieve a speedup of 1000 times, while the realistic rotor is able to achieve a speedup of over an order of magnitude, reducing the computational time to a matter of seconds. The use of the specialized mesh partitioner, with a robust corner node selection strategy, is key to minimizing computational time.
Sensitivity Study of Helicopter Vibrations and Loads with Elastic Fuselage Coupling and Dynamic Empennage Loads from Free Wake Analysis
Authors:   Technical University of Munich (TUM), Rex Willem , Hajek Manfred , Rinker Markus
Published: July 2023

T-tail configurations are a promising approach to increase vertical tail efficiency, reduce fuselage download and hub load cycle amplitudes in low speed transition. However, the horizontal tail can be subject to rotor wake impingement in cruise flight which might lead to high dynamic loads and structural fatigue. The involved aerodynamics are in addition highly complex and hence difficult to be predicted by simulation. In this work a simulation approach for empennage structural loads and vibration prediction is established based on free-wake analysis and modal fuselage approximation, focusing on the expectedly most dominant aerodynamic interaction effects at the T-tail. The results are compared to flight test data to evaluate the approach, and sensitivities of the framework are assessed. The results indicate that the motion of the horizontal tail is characterized only by a few modeshapes, predominantly driven by rotor wake influence, rather than rotor loads via the structural load path. At the same time, high sensitivities are associated with these particular modes and are evaluated in this work to identify the driving mechanisms of T-tail vibrations of the investigated configuration. Discrepancies in the structural model are identified against bang test data. Taking these discrepancies into account, the simulation approach yields reasonable results for T-tail vibrations and loads in comparison to flight test data. In the front part of the fuselage, flight test data is significantly underpredicted as expected and attributed to the employed simplifications in the main rotor blade model.
VTOL Aerodynamic Configurations Analysis for Urban Air Mobility
Authors:   National Helicopter Center - Mil&Kamov, Myasnikov Dr. , Esaulov Dr. , Ilyin Mr.
Published: July 2023

The present study endeavors to consider the most popular eVTOL (electric vertical takeoff and landing) aerodynamic concepts employed nowadays. This research gives a theoretical evaluation of the possible eVTOL design with different electric or hybrid power plant configurations. Conventional helicopter, quadcopter and tiltrotor quadcopter with ducted fans or open rotors have been considered. Relationship between eVTOL mass parameters and available power of the power plant is calculated. Performance of the eVTOL with full electric and hybrid power plants in forward flight mode is estimated. Available and required power needs for speed envelope in hover and maximal speed modes are calculated. Optimal specific parameters (batteries, generators, electric motors) of fully electric and hybrid power plant elements are defined to provide acceptable eVTOL flight performance.
Demonstration of Prop-Rotor System Development for 52kg MTOW Quad-Tilt Prop UAV
Authors:   Korea Aerospace Research Institute, Kim Deog-Kwan , Choi Seong-Wook , Hong Danbi , Kang Hee , Kee Youngjung , Kim Taijoo , Lee Myeong-Gyu , Wie Seong-Yong , Yun Chul
Published: July 2023

Small electric drones (UAVs) were introduced to public people and developed world widely. Companies more than 200 have developed various types of electric drones. Specially the multi-copter which has four propellers, called as quad-copter, was very popular in public people that enjoy personal leisure, sport and hobby. The drone’s technical tendency of worldwide market requested to increase payload, better hover performance and high forward flight speed gradually. Through world market's requirement and technical tendency, KARI had interests in electric drone (UAV) market such as the high flight speed electric drones which have hover and vertical take-off and landing (VTOL) capabilities. In special, the electric UAV which has the reconnaissance and observation mission gives a deep attention to government people, industries and military people. For these targets and goals, KARI had launched to develop 52kg Maximum Take-off Weight (MTOW) Quad-Tilt Prop UAV (QTP UAV) through the previous KARI's smart UAV, rotor system development experience and tilt-rotor technologies. The paper describes that the whole research activity works of its prop-rotor system for QTP UAV. KARI had developed some rotor systems for rotorcraft and UAV more than 20 years. This paper introduces the development of the multidisciplinary design and analysis optimization work for developing prop-rotor system of KARI QTP UAV by using optimization tools which cover better hover and forward flight performance. To research and develop the new prop-rotor system, the new aerodynamic and structural design of propeller had been conducted and these activities were described briefly. Finally, flight demonstration was shown to verify the performance of this prop-rotor system of QTP. For these whole development period, KARI had verified and shown the whole research and development works of the prop-rotor system which as a high performance for QTP UAV founded on main rotor system's previous knowledge and new optimization process.
Evaluation of Sizing Strategies for eVTOL UAV Configurations
Authors:   Airbus A3, Sridharan Ananth ,   Indian Institute of Technology Madras, Govindarajan Bharath
Published: July 2023

eVTOL sizing is tackled with a Multi-Disciplinary Optimization problem with nonlinear constraints in this work, focusing on UAVs with distributed vertical lift. Several optimization schemes are investigated for including airframe sizing with finite element analysis, vehicle trim, and blade aerodynamic shape design. The iterative weight convergence loop is replaced by a slack variable and equality constraint for the sizing optimizer. Airframe sizing and weight minimization (with stress inequality constraints) may be driven either by the sizing optimizer, or by a separate optimizer within the various constraint functions in a nested structure. It is preferable to drive the trim variables using the sizing optimizer; if a particular design cannot be trimmed, this information is propagated to the sizing optimizer through the corresponding equality constraints. The all-at once optimization strategy yields results in the shortest time compared to the other methods. Using modified momentum theory for rotor performance, all gradient-based optimizations from different starting points converged to the same minimum, indicating that the design space is convex for the chosen bounds and objective function. Blade shape design with BEMT is also included in the sizing, either directly with blade twist and taper as additional design variables, or indirectly through a response surface. The methodology is demonstrated on the sizing of two package delivery vehicle configurations (a quadrotor and a lift-augment quadrotor biplane tailsitter) for a mission with 10 km radius of action. The cruise airspeeds for the two configurations are also identified as part of the sizing/optimization. The quadrotor is more suited for this point mission owing to its lower empty weight compared to the quad-biplane, which has better cruise efficiency but higher empty weight.
The Innovative Blade Attachment for the new H145 Bearingless Main Rotor
Authors:   Airbus Helicopters Deutschland GmbH, Emmerling Stefan , Kuntze-Fechner Gerald , Wedekind Max
Published: July 2023

With the market introduction of the EC135 the bearingless main rotor (BMR) as a novel main rotor system was put into series production. Since then a chain of interconnected research programs led to the next generation of BMR. It now enhances the qualities of the H145 regarding the aspects of useful load, comfort of ride, purchase and maintenance cost as well as operational features. The design targets definition and their implementation by innovative solutions are summarized hereafter. The focus is put on the modular design of the main rotor system which is realized by an integrated flexbeam and control cuff assembly and a separate rotor blade joined together by a bolted connection using flat laminate lay-up instead of fiber loops. A detailed view is given on the development of the novel blade attachment from design considerations and manufacturing aspects over parametric subcomponent tests to full scale testing.
Helicopter Short Line Underslung Payload Transportation: Exploration of Magneto-Rheological Actuators for payload motion control
Authors:   Universite de Sherbrooke, Perron Etienne ,   Exonetik Inc., Plante Jean ,   National Research Council of Canada, Alexander M. , Rancourt David
Published: July 2023

This study investigates the magneto-rheological actuator's application into the helicopter slung load operations. The intent is to determine if magneto-rheological actuators (MRA) could enables a new approach to external payload stabilization. A particular solution presented as the Slung Load Stabilisation System (SLSS) is detailed for short line operation. The concept takes shape in a prototype with four MRAs pulling on the four ends of a helicopter landing gear. A prototype is built to tests various conditions and controllers and to be the baseline for further numerical modeling. Numerical trials reveal the SLSS has limited control authority on pendulum motion but gives an appreciable amount of control on the payload azimuth. Lastly, the SLSS prototype is fitted under a conditions Bell-206 helicopter at the National Research Council of Canada to observe its functionality in real-world constraints.
Numerical Investigation of Unsteady Boundary Layer Transition on a Dynamically Pitching Rotor
Authors:   University of Tennessee, Carnes Jared , Coder James
Published: July 2023

Unsteady boundary layer transition predictions are performed on a four-bladed rotor in hover using a computational fluid dynamics approach. Simulations are performed using the NASA OVERFLOW 2.3 solver with hybrid RANS/LES and laminar-turbulent transition modeling. Solutions are based on a hover tip Mach number of 0.143 with prescribed dynamic pitching conditions. The configuration is based on experiments performed at the German Aerospace Center (DLR)in the 1.6-mx3.4-m wind tunnel in the rotor test facility (RTG). Computational methods and grid generation are described. The rotor flowfield is analyzed and the effect of transition modeling on unsteady boundary layer transition prediction is assessed. Laminar-turbulent transition predictions and rotor performance are compared to experimental measurements obtained at the DLR RTG.
Numerical and Experimental Investigation into the Aerodynamic Benefits of Rotorcraft Formation Flight
Authors:   Netherlands Defence Academy, Voskuijl Mark ,   Delft University of Technology, Duivenvoorden Ramon ,   Royal Netherlands Air Force, Moree Lars , Vries Jan , van Finbar
Published: July 2023

The use of formation flight to achieve aerodynamic benefit as applied to rotorcraft is, unlike its fixed-wing counterpart, an unproven principle. This document presents a proof-of-concept of rotorcraft formation flight through a numerical research study, supported by results from an independent wind-tunnel experiment. In both cases, two helicopters are placed in an echelon formation aligned on the advancing side of the main rotor, though they do not simulate directly comparable flight conditions. The vertical and lateral alignment is varied in order to observe the achievable reductions in main rotor power required during cruise flight. The wind-tunnel experiment data yields an estimated maximum total power reduction for the secondary aircraft of 24%, while the numerical models yield reductions between 20% and 34% dependent on flight velocity. Both experiments predict a higher potential for aerodynamic benefit than observed for fixed-wing formations, which is contributed to the asymmetric upwash profile in the rotor wake. Optimal lateral alignment of both experimental and numerical results is found to feature overlap of the rotor disk areas due to circular area effects. Experimental data shows an optimal vertical alignment of the secondary rotorcraft below the primary, due to wake displacement. This is not present in the numerical simulations as a result of the applied leader wake modeling.
Simulation of Step Input in Collective Pitch for Hovering Rotor
Authors:   University of Glasgow, Woodgate Mark ,   Nanjing University of Aeronautics and Astronautics, Li Pan , Barakos George , Fitzgibbon Thomas , Shi Yonghie
Published: July 2023

Advanced CFD tools are nowadays used routinely for analysis and design of rotorcraft. Computations for flows around rotors in trim are also common place and slowly the research community is shifting towards simulations of rotorcraft during maneuvering flight. One of the impediments of this effort is the lack of detailed data for validation, evaluation and thorough assessment of CFD methods when it comes to rotors with time-varying inputs. This paper presents a first effort to validate CFD tools for step-inputs in rotor control angles and presents both novel simulations, and un-published experimental data. The results show that there is always a lag involved between the wake and loads response and the operation of low-thrust rotors with dynamic wakes and collective input is a challenging task for modern CFD. The results used in this work originate from a study carried out at the Nanjing University of Aeronautics and Astronautics in China and represent a unique set of great value to the research community. The agreement with simulation results further contributes to the value of the test data.
Investigation of the Interactional Aerodynamics of the XV-15 Tiltrotor Aircraft
Authors:   NASA Ames Research Center, Tran Steven ,   US Army CCDC AvMC, Lim Joon
Published: July 2023

The high fidelity computational fluid dynamics (CFD) tool CREATE™-AV HELIOS is used to investigate the interactional aerodynamics of the XV-15 tiltrotor in this work. The full vehicle is studied in a quasi-static manner with various airspeeds, nacelle angles, and vehicle attitudes to simulate hover-to-forward flight transition. The rotor is trimmed using CFD/CSD coupling with CAMRADII. Significant wing-on-rotor interactions are observed where the thickness and loading effects of the wing create an impulsive doublet loading on the rotor as it passes over the wings. Furthermore, the wing is shown to alter the blade-vortex interactions of the rotor at high nacelle angles. The rotor in turn noticeably alters the lift and drag characteristics of the wing. At moderate to low nacelle angles, the rotor downwash enhances the dynamic pressure primarily on the upper surface of the wing, increasing the wing lift by up to 13%. The effect on the drag varies depending on the nacelle angle. At high nacelle angles, the rotor is shown to decrease the both lift and drag of the wing by 15%. Overall, this work serves to illuminate and quantify some of the complex aerodynamic interactions that occur during the conversion maneuver of tiltrotor aircraft.
Reduced-Order Modeling and Analysis of Unsteady Rotor Hub Flows
Authors:   University of Tennessee, Wall Tristan , Coder James
Published: July 2023

Modal Decomposition is used to characterize high-fidelity flow fields for several different helicopter rotor hub variations in forward flight. Computational Fluid Dynamics (CFD) are carried out using the NASA OVERFLOW 2.2, Reynolds averaged Navier-Stokes solver. The simulated flow conditions and computational grids are based on experiments performed in a water tunnel at flight-relevant Reynolds numbers. The grids and computational methods used are discussed in further detail. Fast Fourier Transforms (FFT) are used to examine the force harmonics on the the surfaces of various hubs, revealing a dependence on geometric forcing. Mean-subtracted, space-only POD of the predicted lift and drag show a slow decay of modal energy, implying that a large number of modes is necessary to model the rotor hub. Space-only POD and Spectral Proper Orthogonal Decomposition (SPOD) are also used in an attempt to isolate and identify coherent flow structures in the rotor hub wake.
Aerodynamic Interactions on Airbus Helicopters' Compound Helicopter RACER in Hover
Authors:   Institute of Aerodynamics and Gas Dynamics - University of Stuttgart, Frey Felix , Keßler Manuel , Krämer Ewald , Thiemeier Jakob , Öhrle Constantin
Published: July 2023

In recent years, helicopter manufacturers have developed an increasing number of non-conventional configurations in order to extend flight envelopes of helicopters towards higher cruise speed. Airbus Helicopters' approach is the compound helicopter RACER, which is equipped with a boxwing and lateral pusher rotors. As the combination of these components with the main rotor induces a variety of mutual interactions, influencing their individual aerodynamic performance depending on the flight conditions, the understanding of these interactions is vital for the evaluation of the overall system. For this reason, the respective mutual influence of main rotor, wings and lateral rotors is analysed in this paper for hover. With the help of high-fidelity coupled aerodynamic simulations for the full RACER configuration as well as for setups omitting individual components, first- and second-order interactions of these components are isolated and analysed for their effect on the helicopter’s aerodynamic performance.
Rotating Wing Dynamic Stall: State of the Art and Future Directions
Authors:   Georgia Institute of Technology, Smith Marilyn ,   German Aerospace Center (DLR), Gardner Anthony ,   ONERA The French Aerospace Lab, Richez Francois ,   US Amy CCDC AvMC, Jain Rohit ,   Washington University, Peters David
Published: July 2023

Dynamic stall has been studied for more than fifty years; in the last decade significant advances have been accomplished in the understanding, prediction, modeling and control of dynamic stall on rotors. In September 2019, an Army Research Office-funded workshop was held at the Georgia Institute of Technology to evaluate the state of the art and future directions in the understanding and control of dynamic stall found on rotors, specifically for vertical lift vehicles. Approximately forty attendees drawn from top experts in the field to graduate students convened to discuss experimental, computational, theoretical, and control research in the field over a two-day period. This paper provides a summary of the findings from this workshop, including a synopsis of best practices for experiments and first-principles-based computational prediction of rotor dynamic stall. Experimental data sets are discussed, as well the direction of research for empirical (non-first-principles) modeling and control of dynamic stall.
An Overview of Wake Breakdown in High-Fidelity Simulations of Rotor-in-Hover
Authors:   HPCMP CREATE QA, Hariharan Nathan ,   The Boeing Company, Narducci Robert , Abras Jennifer
Published: July 2023

Wake breakdown is a well-documented computational phenomenon associated with highly resolved computational hover predictions. As the computational state-of-the-art for hover predictions has progressed, allowing for higher resolution of the rotor wake, the formation of secondary braids in computed helical wake systems has manifested in various forms. The formation of 3D secondary braids between two parallel convecting vortex filaments, under the right conditions, is physical. Recent hi-definition rotor-hover experiments do confirm their presence. However, computed wake breakdown is more pervasive, and the question of whether high-fidelity methods exaggerate the extent of the secondary vortex production has been a topic of research in the past decade. In this paper, we survey the computational ingredients that make up a high-fidelity hover solver, highlight interesting recent developments, and try to summarize what we know (and what we do not know) about computed wake breakdown. Recent advances in the use of direct volume rendering to visualize the vortical content of the helical wake and the insights they provide into the wake breakdown vortical interplay are also highlighted. Future directions for unsteady, high fidelity hover simulation wake breakdown research are speculated to include an emphasis on temporal fidelity/convergence.