bluuebunny/crossref_metadata_2025 huggingface dataset:
Photocatalytic Degradation of COD and NH4+-N Using TiO2/Sn4+ Nanomaterials: Optimization of Physicochemical Parameters and Kinetics Studies
Authors: Liu Yun Qing , Zhu Wen Yi , Yang Nian Wei , Wang Tian Xing , Yin Zhi Zhen
Published: September 2024

The photoactive nanocomposites TiO2/Sn4+ with various ratios of Sn4+ were prepared by a sol-gel method. Their morphology and crystal structure were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The effect of various parameters such as amount of doped Sn4+ ions, catalyst loading, initial pollutant concentration, pH value, H2O2 concentration on photocatalytic degradation performance were analyzed and optimized. The optimal experimental conditions obtained through orthogonal experiments that highest value was obtained at 3%-Sn4+ doping amount, catalyst dosage 1.5 g/L, initial chemical oxygen demand(COD) concentration 600 mg/L, initial ammonia nitrogen(NH4+-N) concentration 50 mg/L, H2O2 3%, and pH = 8. The photocatalytic degradation rates of NH4+-N and COD reached 87.54% and 75.32%, respectively.
A Numerical Method for Solving the Time Dependent Hartree-Fock Equations of the Helium Atom
Authors: Naranchimeg Dagviikhorol , Sukh Ochir , Munkhsaikhan Gonchigsuren , Tsogbadrakh Namsrai
Published: September 2024

This paper presents an efficient and accurate method for solving the time-dependent Hartree-Fock equations for the helium atom in the ground and single excited states. The radial coordinate is discretized by the discrete variable representation (DVR), which is constructed from Coulomb wave functions. To solve the equation, the spectral method with Coloumb wave functions is used as a basis. We illustrate that the calculated electronic energies for the helium atom are in good agreement with the best available experimental values. The CWDVR method proves to be more economical and efficient as it uses the optimal few numbers of grid points compared to other numerical calculations.
An Analysis of Classical and Alternate Hexacopter Configurations with Single Rotor Failure
Authors:   Rensselaer Polytechnic Institute, McKay Michael , Niemiec Robert , Gandhi Farhan
Published: September 2024

This study examines the operation of a hexacopter in hover and forward flight conditions with a single rotor failure. A classical configuration, with adjacent rotors spinning in opposite directions, and an alternate configuration are considered. The simulation model used in this study calculates aerodynamic forces (thrust, drag and side force) and moments (pitching and rolling moments, and torque) at the rotor hub using blade element theory coupled with a finite-state dynamic inflow model to capture the rotor induced velocities. Failure of various rotors is considered individually and an understanding is developed of how the aircraft trims post-failure. For the alternate configuration hexacopter, if one of four rotors (out of six) fails, the aircraft can be trimmed in hover as well as in forward flight, and is fully controllable. But recovery from failure of one of the other two rotors for fully trimmed flight is impossible. For the classical configuration hexacopter, if any of the forward facing rotors fail, the aircraft can be trimmed in forward flight and is fully controllable. If an aft rotor fails, the aircraft cannot be trimmed, but could be turned around to orient the failed rotor forward. While the classical configuration can always be trimmed in hover by turning off the rotor diametrically opposite rotor to the failed rotor, the aircraft is not independently controllable about all axes due to a rank deficient control matrix. Thus, in the event of a rotor failure, the classical configuration hexacopter could cruise back to base and land, but not maintain a sustained hover. Power penalties of up to 23% were observed in the event of failure due to the increased induced and profile drag on the operational rotors.
Modeling, Analysis and Implementation of a Thrust Vectoring Bi- Rotor with Active Oblate Tilting
Authors:   Georgia Institute of Technology, Afman Juan-Pablo ,   Georgia Tech Research Institute, Mayo Michael , Prasad JVR , Bivens Courtland
Published: September 2024

The modeling, design and implementation of a thrust-vectoring bi-rotor with active oblate tilting is described. The equations of motion for such vehicle are formulated, and later employed in a modular model-based design framework. Modeling of the vehicle enables the analysis of several design parameters, as well as for synthesis of stability and autonomous control law for the vehicle. System identification of existing hardware is performed, including motor and servo dynamics, enabling for a simulation with an acceptable level of fidelity by providing realistic dynamics, forces and moments associated with the vehicle. An open source simulator is employed to visualize the dynamics of flight of the bi-rotor in real time, through pilot in the loop interactions. Finally, insights from the model-based design are employed in a customized physical test-bed. The design decision enables a foundation for the study of challenges associated with a vertical mobility system capable of carrying the weight of a person.
Testing and Characterization of Hybrid Unmanned Aerial/Underwater Vehicle at the air-water interface
Authors:   University of Maryland, Crane Jason , Faruque Imraan
Published: September 2024

Hybrid Unmanned Aerial/Underwater Vehicles (HUA/UV's) have the challenge of robustly operating within and transitioning between two vastly different environments. To meet this challenge, an amphibious quadrotor was constructed and its transition performance quantified using motion capture under manual control. The approach is novel in that it performs transition without active buoyancy control or increasing the number of rotors. The loads across air-water transition were quantified using a controlled single motor-propeller pod and a six-axis load cell. Experimental results were compared against blade element momentum theory (BEMT). The BEMT model correlated well with experimental thrust data when the propeller was in 'fully in air' or 'fully in water' environments. A simplifying dimensional analysis of the model predicted first order relations between electronic speed controller measurable parameter of revolutions per minute against the variation in fluid density. Derived parameters of effective density, entry offset depth, and critical depth were introduced and discussed. The first order relations showed agreement with experimentally derived data, suggesting that "effective density" may have a role in enabling attitude regulation across the air-water interface.
Elysium 24-Hour Hovering Machine Conceptual Design - 2017 Student Design Competition Graduate Proposal
Authors:   University of Maryland, Escobar Daniel , Sinotte Tyler , Oas Peter , Lee Bumseok , Mills Brent , Jude Dylan , Craig William , Govindarajan Bharath , Nagaraj Vengalattore , Chopra Inderjit
Published: September 2024

34th Annual AHS International Student Design Competition 2017 - 24 Hour Hovering Machine Conceptual Design, Graduate Entry
A Truly Biomimetic Hover-Capable Flapping Wing Robot
Authors:   Texas A&M University, Coleman David , Benedict Moble
Published: September 2024

This paper describes the development of a biomimetic robotic hummingbird that utilizes biologically inspired wing kinematic modulation strategies for active stability and control. By tilting the flapping planes, varying the relative wing flapping amplitude, and shifting the mean position of the flapping stroke, the robotic hummingbird is able to modulate the magnitude, direction, and location of the lift vector of each of the wings in the same way that hummingbirds do to maneuver and stabilize themselves. In addition to the control strategies, biologically inspired, flexible, aeroelastically tailored wings were developed for use on the vehicle. Flight tests were conducted in which the vehicle was flown in a controlled hover using combinations of control techniques to quantify the effectiveness of each in stabilizing the vehicle. In the present study, emphasis was placed on pitch control, where two different control strategies were investigated, which were (1) pure tilting of the stroke plane, and (2) stroke mean shifting. Based on the flight experiments, a combination of 90% mean shifting and 10% stroke tilting proved to be significantly more effective than pure stroke plane tilting with almost 40% decrease in drift and attitude oscillations. This is the first ever study where the exact kinematic control strategies used by real hummingbirds and two-winged insects are implemented on a robotic flyer and investigated through free-flight testing.
A Scalability Study of the Multirotor Biplane Tailsitter using Conceptual Sizing
Authors:   University of Maryland, Govindarajan Bharath , Sridharan Ananth , Chopra Inderjit
Published: September 2024

This paper presents a methodology for preliminary sizing of unconventional rotorcraft using a physics-based approach to size and estimate the weight of primary load-carrying members. The methodology is demonstrated for a Quadrotor Bi-plane Tailsitter (QBiT), a tilt-body configuration that can operate in both helicopter and airplane mode. A beam lattice framework for the airframe structure, and the spar geometry in the rotor blade are iteratively adjusted during design sizing to accommodate the expected wing loads and rotor blade loads. Using this analysis, a consistent combination of vehicle macro-dimensions (rotor radius, tip speed, wing span) as well as detailed design parameters (spar height, skin thickness and cross-section weight) are obtained simultaneously. To compare the effectiveness of various powerplants within a weight class, the sizing methodology was modified to identify the payload for three different vehicle take-off weights: 20 lb, 50 lb and 1000 lb. To enable operation within constrained urban canyons, the effect of restricting maximum vehicle dimensions to 10 ft for the 1000-lb designs is also examined. An electric transmission model is used in these designs owing to its relative insensitivity of transmission efficiency to the operating RPM.
Towards Automation of Helicopter Landings on Ship Decks Using Integer Programming and Model Predictive Control
Authors:   Ho Chi Minh City University of Technology, Ngo Tri ,   Virginia Tech, Sultan Cornel
Published: September 2024

A novel method for the automated control of helicopters in landing maneuvers on ship decks is proposed, which combines integer programming and model predictive control (MPC). The helicopter is first brought sufficiently close to the landing deck using a standard MPC. In the final phase of the mission, termed the rendezvous phase, implementation of the novel control design method allows the MPC to rapidly adapt to the landing deck state via a variable prediction horizon. The control design problem includes an integer variable vector which is used to frequently estimate an appropriate prediction horizon for the MPC during the maneuver. This process mimics the manner in which human pilots act, by repeatedly estimating how long ahead during the ship landing maneuver their actions are effective to safely accomplish the mission. The performance of the proposed procedure is evaluated via numerical simulations using a nonlinear helicopter-ship dynamics interface that captures significant characteristics of the helicopter and ship dynamics, as well as the ship airwake effects. These simulations show that the proposed method can be effective in satisfying rendezvous conditions for helicopter ship landing even when the moving deck has a very high energy index.
Swashplate Actuator Failure Compensation for UH-60 Black Hawk in Cruise using Horizontal Stabilator
Authors:   Rensselaer Polytechnic Institute, Vayalali Praneet , McKay Michael , Krishnamurthi Jayanth , Gandhi Farhan
Published: September 2024

A flight simulation model for the UH-60 Black Hawk based on Sikorsky's GenHel model is modified to simulate a locked failure of a main rotor swashplate servo actuator and is compensated by using the stabilator as a redundant control effector. Steady state trim analysis is performed to demonstrate feasibility of trimmed flight in various conditions with different locked servo actuator positions for the forward, aft, and lateral actuators. A model-following, linear dynamic inversion controller is implemented and modified to account for locked actuator position. Post-failure, the control mixing and feed-forward control coupling terms are reconfigured to partially reallocate the control authority in the longitudinal axis from the main rotor longitudinal cyclic to a symmetric deflection of the stabilator. This is done by manipulation of only the control allocation relating pilot stick inputs to servo actuator positions, the feedback control gains and mechanical rigging between servo actuators and rotor pitch controls remain identical to the baseline controller. Flight simulation results demonstrate the ability of this reconfiguration to compensate for locked failure of the forward main rotor swashplate servo actuator, as well as the ability of the aircraft to decelerate from cruise at 120 knots to 50 knots which is less than the published safe rolling landing speed of 60 knots. A similar range of locked positions of the forward and aft actuators is demonstrated to be feasible for aircraft recovery using control of the stabilator. Feasibility of aircraft recovery for locked positions of the lateral servo actuator is also considered.
Post-ESC-Failure Performance of a UAM-Scale Hexacopter with Dual Three-Phase Motors
Authors:   Rensselaer Polytechnic Institute, Fong Weston ,   North Carolina State University, Gandhi Farhan , Walter Ariel , Niemiec Robert
Published: September 2024

Dual three-phase motors are simulated on a 1200 lb hexacopter to examine its ability to tolerate any single electronic speed controller (ESC) failure. Redundancy is added, as each motor includes two sets of stator windings, powered by electrically independent ESCs, which drive a single motor shaft. Flight control laws are tuned on the healthy aircraft to meet standard flying-qualities specifications. Power constraints are embedded in the controller to enforce both instantaneous and continuous power limits for each ESC. With the proposed dual three-phase motor, the aircraft is shown to be capable of trimming in all single ESC failure cases, including the case of aft motor failure in forward flight. Time-domain simulations demonstrate the aircraft's ability to re-establish trim and recover from any single ESC failure in hover and forward flight. Flying-qualities specifications are re-evaluated for the post-failure aircraft, showing minor, but not debilitating, degradation in several flying-qualities metrics. The post-failure aircraft's ability to follow commands without violating power constraints is verified through time-domain simulations.
Active Vibration Damping and Harmonic Vibration Reduction in an eVTOL Aircraft Model Using Electric Rotor Torque
Authors:   The Pennsylvania State University, Cho Changik ,   Overair Inc., Singh Puneet , Rahn Christopher , Smith Edward
Published: September 2024

Rotorcraft experience significant vibrations due to periodic aerodynamic forces and moments on the rotor blades and wings. Rotor torque damping is a novel vibration damping method which uses small torque perturbations from the main electric motor to reduce vibrations. The large inertial and aerodynamic rotor loading and relatively high frequency torque perturbations mean that the rotor speed changes are small, so the rotor thrust and flight control performance are not significantly affected. This paper investigates the application of electric motor torque control for damping structural vibrations of an aircraft. The structural dynamics of the aircraft are represented using a finite element model of a quad tiltrotor eVTOL. Using collocated angular rate feedback on all four rotors provides more than 10% damping in controllable modes. The RMS value of flap-wise angular rate can be reduced by 91% with less than 1.2 RPM rotor speed change in response to a 20% vertical step gust in airplane mode. For N/rev disturbance cancellation, an optimal controller is designed assuming known disturbance location and frequency for active vibration control (AVC). The transfer matrix of a single cantilevered wing is calculated and used to feed forward harmonic rotor torques. The wing undergoes aerodynamic disruptions at N/rev and the harmonic controller reduces N/rev shear force and bending moment at the root by 20% and 58% with less than 1 RPM rotor speed change, respectively.
Reducing Vibrations Experienced by an Infant During Air Transportation
Authors:   Gannon University, Piatt Sophia , Ji Xiaoxu , Deemer Alexander , Young Sarah , Merlos Hilcia , West Isaac , Piovesan Davide
Published: September 2024

Some infants are born prematurely or with medical conditions that require them to stay in neonatal intensive care units (NICUs). Typically, these infants spend most of their time in an incubator as it provides a safe and controlled environment. At times, these infants will need to be transported via helicopter from one hospital to another, which exposes their already fragile bodies to higher levels of vibration. Helicopters, while advantageous for medical transport, generate substantial vibration due to rotor dynamics. Current models of incubators lack specific design for reducing vibrations. This project proposes a functional vibration damper that can be integrated into existing neonatal incubators, aiming to enhance infant safety during air transport. ANSYS modeling identified low-density polyethylene foam as an effective material for vibration reduction. Flight simulation tests demonstrated the 2" polyethylene mattress reduced vibrations at low amplitudes and frequencies, but challenges arose at higher values. The prototype addresses the critical need for reducing vibrations in neonatal incubators during air transport. While successful in initial tests, further extensive testing is required for potential implementation in the medical industry.
Automated Calculation of Aerodynamic Coefficients for sUAV Using Ardupilot Logging Data and Inexpensive Sensors
Authors:   Technical University Munich, Rieger Christian , Zimmermann Paula , Hornung Mirko
Published: September 2024

Manual analysis of the aerodynamic behavior of small unmanned aircraft is a lengthy and repetitive task. This paper shows the current state of an automated flight analysis tool that calculates the aerodynamic coefficients of small unmanned aerial vehicles. It covers the tool's workflow, shows the current quality of the data processing, and lessons learned. It compares the results of different aircraft types, including standard electric motor and glider aircraft, and shows specifically designed and tested flight patterns. The results of the tool are compared to manually computed data from the glider using a low-wind flight before sunrise. Finally, the impact of thermals on the measured data is presented. An outlook will show the remaining limitations and possible future additions to the tool.
Flight Trajectory Tracking for Training Simulator Qualification Using Model Predictive Control Strategy: A Case Study
Authors:   University of Laval, Desbiens Andre ,   CAE, Nadeau-Beaulieu Michel , Myrand-Lapierre Vincent
Published: September 2024

A high-fidelity flight simulator is used to effectively train and evaluate pilots. The simulator must, however, be previously qualified by authorities by comparing the responses of the simulator to those of flight tests for several maneuvers. The use of a controller is permitted to make corrections to the simulator input signals. The simulator inputs and outputs must, however, be within tolerance bands defined by the authorities, compared to flight test data. This article presents a model predictive controller (MPC) and its evaluation on a takeoff and landing case. The method is already promising because these results were obtained after very few tuning iterations, which could result in significant time and cost savings. This is made possible by the clear meaning of the impact of the MPC tuning parameters on the simulator inputs and outputs and also by the ability to intrinsically consider the interactions and constraints of the multivariable system.
Application of BOS Velocimetry to Full-scale Helicopter Flight Tests
Authors:   German Aerospace Center - DLR, Braukmann Johannes , Wolf C. , Gardner Anthony
Published: September 2024

Time-resolved background-oriented schlieren (BOS) data are used to calculate the two-dimensional velocity field in the wake of free-flying full-scale helicopters in ground effect. The calculation is performed based on the density gradient pattern of the helicopter engine exhaust gas passing the BOS field of view. A classical BOS evaluation allows the visualization of density gradients such as vortices and the exhaust plume. The result is the BOS displacement field. Applying the two-dimensional divergence to this data results in a pattern that is constant in shape across multiple BOS images, but convects downstream with the outwash velocity of the helicopter. Using this data as input to a second, timeresolved evaluation, quantitative two-dimensional velocity fields are calculated. Choosing an appropriate strategy for preparing and evaluating the data is critical to reliable velocity estimation. Another important aspect is to distinguish between reliable velocity data and erroneous results in areas of reduced signal intensity due to a lack of thermal structures. The velocity data obtained are compared with an analytical outwash model and constant temperature anemometry data acquired simultaneously with the BOS images. The data show good quantitative agreement in areas of sufficient thermal structures within the field of view.
Forward Flight System Identification for an Electric Medium-Sized Variable-Rotational Speed Rotor
Authors:   San Jose State University, Glover Emily ,   University of Maryland, Teodorescu Radu ,   US Army CCDC ARL, Floros Matthew ,   US Army CCDC AvMC, J. Mark , Padthe Ashwani , Berger Tom
Published: September 2024

The Joint Tactical Aerial Resupply Vehicle (JTARV) project is supporting the expansion of the Army's unmanned aerial reconnaissance capability by working to obtain high-quality test data that is scarce for group 2 and group 3 UAVs to validate physics-based models. This paper will evaluate the system identification results from transient testing at a wind tunnel speed of 29.2 kts (15 m/s) of the commercial off the shelf T-motor '28x9.2' rotor which is used on the TRV-80 platform, a group 3 UAV. Rotor angles of attack of -90° to 0°, which represent climb to edgewise flight respectively, were tested in the wind tunnel. Chirp Pulse-Width Modulation (PWM) sweep inputs that varied the ΔPWM amplitude by 50, 100, and 150 (approximately 3%, 6%, and 10% of the steady state PWM) were analyzed to derive an electric motor model that can be used in a physics-based simulation. Additionally, it was found that the identified coefficients of thrust and torque were higher in transient conditions versus steady for most angle of attack test conditions. Lastly, the closed loop wind tunnel system, thrust due to ΔPWM amplitude sweep, was compared to the closed loop system of the TRV-80. A similar motor lag frequency was identified in both systems which shows the relevance of the electric motor model and rotor performance data derived from wind tunnel data presented herein.
Flight Testing and Analysis for a Family of Group 2 and 3 Multicopter UAS
Authors:   San Jose State University, Glover Emily ,   US Army CCDC AvMC, Gong Anthony , Cho Sung , J. Mark , Berger Tom
Published: September 2024

Multirotor UAS spanning Groups 3 and 4 have received increased attention as candidates for tactical resupply missions due to their VTOL capability and payload capacity. The objective of this work is to better understand how the parameters of multicopter UAS flight dynamics models scale with size in support of expanding the Army's unmanned aerial reconnaissance capability. A family of coaxial multirotor UAS spanning Groups 2 and 3 have been flight tested to gather data for flight dynamics modeling and validation. These UAS consist of the TRV-80, TRV-150, and the subscale Eagle platform. A series of test points including static stability, trim shot, frequency sweeps, doublets, and maximum climb rate maneuvers were collected. Wind data was simultaneously collected using a 3-axis ultrasonic anemometer to characterize wind conditions and characteristics during testing. Flight data were collected in varying payload configurations ranging from 0-120 pounds and at flight conditions ranging from hover to 50 knots. Point state space models were identified from frequency sweeps and verified using doublet time histories. Point models of the TRV-150 were combined with trim data and experimentally measured moments of inertia to develop a stitched simulation model. The stitched model was used to extrapolate for the flight tested off-nominal payload configurations for analysis. The unstable roll and pitch hover eigenvalues between the vehicles within the TRV family and smaller Group 1-2 UAS were analyzed and compared to Froude-scaled results to establish trends based on vehicle aspect ratio.
Utilizing Advanced Air Mobility Rotorcraft Tools for Wildfire Applications
Authors:   NASA Ames Research Center, Aires Jeremy , Withrow-Maser Shannah , Peters Nicholas
Published: September 2024

Over the past decade, due in large part to heavy investment in the field of Advanced Air Mobility (AAM), significant progress in rotorcraft-focused modeling tools has been made. Such progress has notably increased AAM rotorcraft modeling capabilities in the topics of conceptual design, preliminary design, and more recently flight dynamics. Yet, due to recent and persistent increases in extreme weather events, an emerging interest has been raised in utilizing such modeling capabilities for aiding in emergency relief efforts and other public good missions. This paper uses wildfire fighting as a representative public good mission and demonstrates the relevance of the NASA Revolutionary Vertical Lift Technology (RVLT) rotorcraft toolchain to such missions. An emphasis is placed on flight dynamics modeling and control because of the hazards and challenges associated with the atmospheric environment of wildfires. In this work, the NASA FlightCODE tool was used to analyze both a UH-60 and the NASA six-passenger quadrotor reference model hovering in an experimentally informed wildfire turbulent environment. Preliminary results of this study estimate actuator usage exceedances and disturbance rejection capabilities of the vehicles' translational rate command systems. Leveraging the RVLT toolchain, refinement and expansion of this work could lead to handling qualities envelope estimation and design optimization for wildfire turbulent environments. This would provide pilots with additional information to make real-time decisions in high-risk scenarios and begins preparations for simulating these dangerous environments for pilot training and experimentation.
Minimum Energy Performance for Autonomous Control of Tiltrotor eVTOL Operations
Authors:   Cranfield University, Kang Namuk , Lu Linghai , Whidborne James
Published: September 2024

The paper presents a novel strategy for minimum energy consumption in automatic conversion control of tiltrotor eVTOL aircraft, exemplified by the Aston Martin Volante Vision model. We introduce a tilt schedule methodology that strategically balances conversion and reconversion performance with climb, descent, and cruise phases to minimize overall energy expenditure. Our approach accounts for critical factors such as blade loading, operation handling qualities, and passenger ride comfort within a predefined conversion corridor. The optimized trajectories approximate the minimum energy pathway, essential for operational efficiency in urban air mobility. Analytical results demonstrate that our proposed conversion and reconversion phase profiles significantly reduce energy consumption, contributing to the sustainability of tiltrotor flight operations. This research not only enhances understanding of tiltrotor dynamics but also serves as a pivotal step toward achieving globally optimized energy usage, marking a significant advancement in autonomous flight technology for advanced air mobility systems.
Overview of RCAS Capabilities and Validations for Rotorcraft and eVTOL Applications
Authors:   Advanced Rotorcraft Technology Inc., Hasbun Matthew ,   US Army CCDC AvMC, Yeo Hyeonsoo , Saberi Hossein
Published: September 2024

This paper presents an overview of the Rotorcraft Comprehensive Analysis System (RCAS) capabilities, recent enhancements, validations, and application to practical rotorcraft and electric vertical take-off and landing (eVTOL) problems. Nine years have passed since a similar paper was presented in Ref. 1; and 20 years since the first RCAS overview paper was published in Ref. 2. RCAS has been continually enhanced over the last nine years and there have been several significant developments. This paper summarizes these developments, which include improvement of existing structural modeling, better support for multi-rotor variable RPM modeling, enhanced vortex wake and airloads modeling options, expansion of coupling with CFD modules, and improvements to the graphical user interface. This paper also surveys the body of recent RCAS validations, which has greatly expanded since the last paper. RCAS validations now include detailed work on tiltrotor hover and cruise performance, loads, and whirl flutter stability, and coaxial rotor and compound helicopter performance and loads, in addition to conventional rotorcraft configurations. Validation studies are being conducted for eVTOL configurations. This paper provides the rotorcraft technical community with an up-to-date and consolidated resource on RCAS by summarizing capabilities, recent developments, and validations, while also demonstrating selected applications.
From Dampers Estimated Loads to In-Service Degradation Correlations
Authors:   Airbus Helicopters, Mechouche Ammar , Camerini Valerio , Del Caroline , Cansell Elsa , Nikolajevic Konstanca
Published: September 2024

This paper presents an original method that takes advantage of existing large in-service flight data, damper load Machine Learning models as well as the inventory of degraded dampers (elastomeric part), to link the estimated loads and operational conditions to damper degradation cases. The Machine Learning models are trained on flight test campaigns data, and then applied on in-service helicopter data to estimate damper loads as a function of flight parameters. The estimated load history is then used as an input to generate engineering load indicators. These latter, jointly with operational and usage data, are correlated with the reported dampers' degradation observations. Finally, an explainability mechanism is investigated to better understand the Machine Learning models inferences, opening perspectives towards precise damper degradation root causes identification. The obtained results are promising, showing that the occurrence of damper degradation correlates with load history and helicopter operations.
Six Nines Reliable Army Fatigue Critical Component Using Operational Loads Data
Authors:   Peraton Inc., Finckenor Jeff ,   US Army CCDC AvMC, Chandler Michael , Evans Holly , Ruffin Aniekan
Published: September 2024

This paper describes the work performed to determine a 0.999999, 6 nines, reliable fatigue critical component life using field monitored loads. The Tie Bar of the MH-47 is substantiated by Centrifugal Force (CF), which is a direct function of rotor speed, Nr, which is a monitored parameter in the Structural Usage Monitoring System (SUMS). Six nines of reliability has been the Army target for component reliability and it is generally assumed that legacy safe-life methods are near this level of reliability. With monitored loads it is possible to develop a statistical model for loads and determine an actual reliability value. This paper presents multiple methods for the Army's first attempt at establishing a retirement time using an absolute component reliability. Reliability is gained using a reduction of the Endurance Limit and mean and standard deviations of binned loads across multiple aircraft. Most notably fatigue lives can vary widely if the independent variable reliability contributions are assigned arbitrarily.
A SUMS Based Usage Spectrum for the UH-60M ITE Equipped Black Hawk
Authors:   Peraton Inc., Finckenor Jeff
Published: September 2024

Previous work documented the use of IVHMS data on the U.S. Army's fleet of UH-60 Black Hawk helicopters to update the fatigue lives of six specific components on the A/L and M models. This paper documents a significant expansion of the level of data applied to the usage spectrum, as well as applying it to all components on the aircraft. As a design spectrum for the yet to be fielded Improved Turbine Engine (ITE) equipped UH-60M, changes due to new engine capability needed to be addressed. The new spectrum has been developed and is being used for planning of flight testing. The spectrum along with flight test loads will be used to generate fatigue lives for the new aircraft. Once deployed for several years the spectrum will be reviewed to determine if any changes are needed. This work highlights what the Army considers to be the most significant issues when applying monitored usage to critical fatigue components, and rationale for dealing with issues such as insufficient data for various purposes.
Flow Diagnostics of Scaled-Model Coaxial Rotor Hub Flows
Authors:   The Pennsylvania State University, Schmitz Sven , Jaffa Nicholas , Reich David , Nickels Adam , Pabon Rommel , Piqué Alexander , Durachko Tim
Published: September 2024

Rotor hub parasite drag remains one of the challenges in further improving the forward-flight capabilities of coaxial rotorcraft. Comprehensive datasets on notional coaxial hub configurations are rare, and more so at Reynolds numbers sufficiently high to preserve dominating flow structures downstream into the wake where they interact with the rotorcraft empennage and tail. The present investigation was designed specifically to improve the understanding of interactional aerodynamics effects and wake flow physics of counter-rotating coaxial rotor hubs. A unique dataset is presented on a rotor hub design equipped with the DBLN 526 airfoil at a diameter-based Reynolds number of 1.13x106, corresponding to approximately quarter-scale Reynolds conditions of a coaxial compound helicopter at 200 knots. The experiments measured the time-averaged and time-varying drag on the hub configuration, with focus on a cruise advance ratio of 0.25 and a high-speed condition at 0.60. In addition to measuring hub drag and its harmonic content, a unique aspect of the experiment was the use of multiple non-invasive flow-diagnostics techniques for the particular hub configuration, advance ratios, and Reynolds number. Specifically, stereoscopic particle-image velocimetry (SPIV) measured the three velocity components at two downstream locations in the hub wake, thus providing insight into and visualizing the development of the wake. In addition, a limited laser-doppler velocimetry (LDV) and a tomographic PIV (Tomo-PIV) data campaign were conducted that confirm the earlier SPIV measurements. A subset of all measurements is presented. Some new insight into the flow physics was gained, one example being the dependence of higher-harmonic per-rev flow structures in the wake on hub advance ratio.
Wind Tunnel Testing of RPAS in Representative Urban Flow Fields
Authors:   National Research Council Canada, Barber Hali ,   Carleton University, Tabachnich Isaac , Wall Alanna , Kumar Sukriti , McKercher Richard
Published: September 2024

This paper describes wind tunnel testing of small remotely piloted aircraft systems (RPAS) to understand better the maximum wind speeds in which they can be safely operated. Urban flow fields can contain complex flow structures such as speed changes, direction changes, shear layers, turbulence and vorticity; all of these can impact the safety of urban RPAS operations. The work described in this paper is part of an ongoing effort to provide Canadian regulators with knowledge to guide safe RPAS operations in urban environments. In the wind tunnel, flow fields representative of urban flows were created using simple flow manipulators like bluff bodies and vanes. The flow manipulators and the resulting flow fields, in relation to representative urban flows, are described in this paper. Wind tunnel testing of a number of RPAS in these representative airflows was conducted to evaluate the sustained wind speed limit at which the vehicle could maintain a stable hover. These tests enabled a step in the understanding of the wind speed limit for various RPAS in different flows. The paper shows a clear impact of turbulence level on the maximum safe operating wind speed of RPAS.
Scenario-Based Helicopter Flight Simulation of Accident-Prone Vortex Ring State (VRS) Encounters
Authors:   Georgia Institute of Technology, Sotiropoulos-Georgiopoulos Eleni ,   Federal Aviation Administration, Johnson Charles , Payan Alexia , Mavris Dimitri
Published: September 2024

From 2008 to 2021, 48 helicopter accidents have involved Vortex Ring State (VRS) encounters in the United States. For dangerous situations such as VRS encounters and recoveries, Scenario-Based Training (SBT) in flight simulators could supplement flight training, allowing pilots to practice in a safe environment. In this study, we created and tested a proof of concept for scenario-based training in flight simulators, dedicated to VRS-related accident prevention. The goal is to evaluate pilots' awareness, avoidance, detection, and recovery skills during VRS-inducing scenarios. Moreover, this study intends to provide a holistic analysis of VRS encounters and recoveries by examining the situations and factors leading to VRS-related crashes, and to lay out the pilot's decision-making process during the event. For that purpose, a comprehensive set of scenarios was developed based on an analysis of VRS-related accidents from the National Transportation Safety Board (NTSB) database. Overall, the scenarios successfully triggered VRS encounters as well as avoidance actions, providing insight into pilots' behavior in and around VRS conditions.
Applying and Testing the ASTM F3673 - 23 Weather Standard Specification for Enhanced Safety and Efficiency in eVTOL and Helicopter Operations
Authors:   TruWeather Solutions, Berchoff Don ,   Harper4D Solutions, Harper Clint , Zarzar Christopher
Published: September 2024

This article addresses the critical need for enhanced weather observation and prediction systems for rotary-wing aircraft. Current weather systems lack granularity in low-altitude airspace, posing safety risks. The application of the ASTM F3673 - 23 Weather Standard Specification is proposed to standardize weather data collection and transition towards a weather sensor performance-based approach rather than instrument certifications, facilitating the deployment of advanced weather sensors. Today, heliports have a binary weather measurement system choice, expensive certified surface weather stations or a windsock. The standard has the potential to change this paradigm, by allowing the deployment of cost-effective digital sensor technology to reduce uncertainty about what is happening at a heliport or vertiport/vertiplex destination. Operationalizing this specification requires rigorous testing and collaboration through public-private partnerships. Bridging the weather educational gap is essential for enhancing safety in low-altitude aviation. Additionally, the integration of Digital Flight Rules (DFR) alongside the ASTM F3673 - 23 Weather Standard presents opportunities for modernizing air traffic management.
Further Applications of SUMS-based Regime Recognition in Updating the MH-47G Chinook Usage Spectrum
Authors:   Peraton Inc., Evans Holly ,   DEVCOM AvMC, Chandler Michael , Finckenor Jeff
Published: September 2024

This paper documents the re-evaluation and updates to the previous Partial Regime Recognition Spectrum effort for the MH-47G using Structural Usage Monitoring System (SUMS). Further validation of the SUMS algorithm allowed for additions to the spectrum. These additions include more refined categorization of turn and partial power descent regimes based on angle of bank and descent rates, respectively; high load prorates for turns, partial power descents, level flight, and climbs based on the Cruise Guide Indicator; exceedances of maximum density altitude; and use of occurrences for Landing and Run-On Landing regimes. Additional years of flight data from 2013 to 2019 were included in this effort. The updated usage spectrum for the Army MH-47G aircraft has been delivered to the OEM (Original Equipment Manufacturer). The OEM calculated new fatigue lives and updated the "Fatigue Substantiation Report", which will soon be fielded.
A Multidisciplinary Mid-fidelity Approach for Tiltrotor Wing Aeroelastic Design Based on structural Mesh Morphing
Authors:   Leonardo Helicopters, Punzi Claudio , Giovanardi Eleonora , D'Amico Federico , Mancini Andrea , Crooks Mark
Published: September 2024

This paper introduces a Multidisciplinary Design and Optimization (MDO) approach for the design of a tiltrotor wing, utilizing as test case a semi-wing with integrated nacelle and rotor. Structural integrity is assessed via stress analysis on a GFEM, which also forms the basis for a coupled wing-rotor aeroelastic model to ensure whirlflutter stability. Aerodynamic performance is assessed through CFD analysis of two-dimensional wing's airfoil shape. The MDO workflow leverages three levels of design space control that can influence the structural response of the wing: other than controlling the structural properties of composite materials, the internal wing-box architecture and external airfoil shape are modified acting directly on the FEM by means of a mesh morphing technique. This methodology allows for the use of mid-fidelity finite element models, bypassing CAD reshaping and remeshing. Validation tests confirm the approach's effectiveness in producing optimized designs. Additionally, the study explores surrogate models as efficient alternatives to CFD simulations, yielding sufficiently accurate results while reducing computational costs and the MDO simulation time.
Evaluation of the Potential of Photovoltaics for Extended Flight Times of Small eVTOL UAVs
Authors:   Technical University of Munich, Seren Thomas , Hornung Mirko
Published: September 2024

This paper analyses the possibility of using photovoltaics as additional energy provider for small to medium-sized eVTOL UAVs. A simplified model for eVTOL UAVs, which covers all relevant areas of aircraft design, including aerodynamics, structural mechanics, propulsion and systems modelling, is presented. Sensitivity studies covering various design parameters, such as airfoil, wing geometry and propulsion system selection are performed to show their influence on the configurations' performance. The first result of this paper is, that a photovoltaic powered configuration can outperform a battery electric and it can be worth the effort to implement the solar cells. To achieve this, the aircraft needs to be as aerodynamic efficient as possible. Also higher efficiency solar cells increase the possible performance. Additionally there is a big influence of the time of year and the latitude onto the performance. Secondly a multi mission study is performed. This uses a more detailed model, as the preliminary study. It is to find the best solar eVTOL for a set of missions. A summary of this study's results is presented. Finally the best aircraft configuration, following this study, is presented. The main take aways are, that solar cells can have a positive effect on the overall performance of eVTOL UAVS. However some possible drawbacks are also identified, as the resulting aircraft require rather low speeds and a more complicated mission planning, because solar irradiance needs to be taken into account and monitored during the whole mission.
Safety Data Analysis with Machine Learning
Authors:   Sikorsky a Lockheed Martin Company, Brulotte Abby , Monaghan Alex , Soleti Yeshi , Downs Amanda , Hewitt John
Published: September 2024

Safety professionals receive data from internal and external sources, then manually determine whether the issue constitutes a safety hazard. Many reports are received, and each report is reviewed, then investigated further, using a tedious, labor intensive, and possibly error prone process. In the course of reaching a decision, human bias is inevitable - any two humans could reach different conclusions, and the same individual human could draw different conclusions on different days. As technology has advanced, numerous approaches have been pursued, attempting to reduce human bias and improve both efficiency and effectiveness of the process. In recent years, moderate success was achieved, which provided accuracy rates near 85% but continued refinement did not achieve acceptable results. In early 2023, the challenge was given to a new team, and within a few months, state-of-the-art Artificial Intelligence/Machine Learning data analytics techniques were utilized to aid in safety data analysis efforts, which resulted in high accuracy and efficiency, with reduced human bias.
The Advancement of Aerial Firefighting Concept of Operations
Authors:   Sikorsky a Lockheed Martin Company, Gil Monica , Melhorn Shawn , Gorelick Jordan
Published: September 2024

Advancing technology has driven continuous improvements across most aspects of human endeavors. In the time since the first modern helicopter flew in 1939, the world has seen inventions like the microwave, personal computers, cell phones, and the internet. If helicopters predate these society-changing innovations, then it stands to reason that the manner in which helicopters operate has drastically shifted as well. Specifically, this paper reviews historical concepts of operations (CONOPS) in rotorcraft aerial firefighting and analyzes where technology advancements have made an impact on firefighting operations and the performance of helicopters in suppressing fires. These shifts were evaluated using analytical assessments and highlighting snapshots in time of how capability impacted the aerial firefighting mission effectiveness. As companies innovate and technology advances, further benefits to rotorcraft CONOPS in aerial firefighting will be realized.
Autonomy Demos and the Evolution of Optimally Crewed Vehicles
Authors:   Bell Textron Inc., Christensen Kevin ,   US Army CCDC AvMC, Lusardi Jeffery , Govers Francis
Published: September 2024

The integration of automation and autonomy into modern aircraft has significant potential to simplify many piloting tasks. On the other hand, poor integration of automation and autonomy systems with the human crew has sometimes led to unintended consequences. With the goal of improving human-machine integration in piloting tasks, Bell Textron has conducted several autonomy demonstrations in both the simulator and aircraft. The team assessed automated terminal operations, enhanced station keeping, and maneuver tactile limit cueing in a flight simulator. Additionally, the V-280 technology demonstrator conducted autonomous flight profiles to explore these systems in an airborne environment. To mature autonomy systems for integration on future platforms, a Bell 429 was converted into the Aircraft Laboratory for Future Autonomy, completing its first flight last year with fly-by-wire controls at the evaluation pilot station. The influence of Bell autonomy demonstrations on the evolution of Optimally Crewed Vehicles is presented. These efforts have evolved the concept of a digital co-pilot capable of assisting the human crew when called upon, while also acting to enhance aircraft safety through warnings and automated control input, when appropriate.