bluuebunny/crossref_metadata_2025 huggingface dataset:
Disruptive Innovations in Human Resource Management
Authors: Brown B. Anthony , Heitner Keri L.
Published: September 2024

The theories and practices comprising modern human resource management (HRM) boast an extensive evolution and continue to evolve. Fayolism by Henri Fayol (1841-1925), Taylorism by Frederic Winslow Taylor (1857-1915), bureaucracy by Maximilian Weber (1864-1920), leadership styles and change management by Kurt Lewin (1890-1947), theory X and theory Y by Douglas McGregor (1906-1964), the hierarchy of needs by Abraham Maslow (1908-1970), need theory by David Clarence McClelland (1917- 1988), and motivation-hygiene theory by Frederick Herzberg (1923-2000) precipitated and consolidated HRM as known today. Although fundamental to present-day HRM, globally, the HRM tenets hewed in the three previous industrial revolutions remain largely misaligned with sustainable human asset management (sHAM). Given the preceding, the question is whether organizational leaders can use disruptive innovation to (a) enable sustainable human asset management while (b) maximizing efficiency and production to achieve organizational sustainability in the impending fourth industrial revolution.
Big Data Analytics in Human Resources Management With Qualitative Insights
Authors: Erol Hüseyin Özgür , Yildirim Ahmet
Published: September 2024

This study investigates how human resource employees experience the big data phenomenon in the recruitment function of human resource management and how their perceptions of the phenomenon have evolved. This study also examines how big data will affect organizational and human resource management and how it can be improved in other functions of human resources. In this exploratory study, which comprehensively addresses the big data phenomenon in human resources management, the phenomenological design approach, one of the qualitative research methods, was applied to test the research questions and a semi-structured interview form was used for research data.
Turbulence Modeling Strategies for Rotor Hub Flows
Authors:   University of Tennessee, Coder James ,   Georgia Institute of Technology, Cross Philip , Smith Marilyn
Published: September 2024

The influence of turbulence modeling strategy for computational fluid dynamics simulations of rotor hub flows is assessed. Two specific modeling strategies are discussed and applied to a representative rotor hub geometry that was the focus of the First Rotor Hub Flow Prediction Workshop and for which high-Reynolds number force data and wake measurements are available from a water-tunnel experiment. Simulations with both turbulence models were performed on the same structured, overset grid system using the same flow solver. Identical solution strategies were employed, including time accuracy, spatial discretization, and implicit algorithm. Several aspects of the solutions are compared, including mass-flow rate through the domain, unsteady drag characteristics, and unsteady wake characteristics.
Dynamic Stall Experiments on a Rotor with High Cyclic Setting in Axial Inflow
Authors:   German Aerospace Center (DLR), Schwermer Till , Gardner Anthony , Raffel Markus
Published: September 2024

A rotor test facility was developed to investigate dynamic stall under optimized boundary conditions compared to conventional hover chambers. It features a defined axial inflow, reduction of ground effect and recirculation of the rotor wake and good optical access to apply non-intrusive measuring techniques. The rotor consists of two blades with an aspect ratio of 6:8 and a tip radius of 0:65m. It was operated at a chord based Reynolds number of 350,000 and a Mach number of 0:21, both at 75% radius. The flow and blade deformation were analyzed by means of unsteady blade pressure transducers, particle image velocimetry and tip deflection measurements covering the whole azimuth and different radii. Three measurement approaches to detect flow separation: tufts, differential infrared thermography and surface pressure analysis showed comparable results and flow separation over one half of the cycle. A radius-dependent separation point in time and an altering of the dynamic stall behavior near the tip were observed. The recirculation area remained close to the blade's surface with radial jet flow increasing towards the tip. A maximum increase of the effective angle of attack of 1:4° was observed due to blade deformation. For a fully attached flow case the laminar-turbulent boundary layer transition differed along the radius and moved over 70% of the blade's chord.
Internal and Blade Surface Pressure Measurements of Centrifugal Flow Control on a Large Scale Rotor
Authors:   Sikorsky a Lockheed Martin Company, Lorber Peter , Wallace Brian , Scott Mark
Published: September 2024

A large scale rotor test has been performed to evaluate concepts for improving the high thrust and high speed capabilities of an edgewise single rotor helicopter. The primary approach was to alleviate dynamic stall using centrifugally pumped steady blowing, referred to as Retreating Side Blowing (RSB). This concept was studied earlier for an airfoil with a flow control slot able to generate momentum coefficients of 0.03 to 0.05 using computational simulation and experiment. The current experiment uses a 28 ft diameter rotor having an inlet at the blade root, a hollow spar, and a series of flow control slots from 65% to 95% of the radius. It was tested at the Sikorsky Main Rotor Whirl Stand and at the National Full Scale Aerodynamic Complex. Rotor performance and structural load data were acquired for multiple configurations at advance ratios of 0.24 to 0.61. This paper focuses on the internal pressure measurements used to determine the performance of the centrifugal pumping system in hover and in forward flight, and on the external pressure measurements used to define the effect of the slot blowing on the dynamic stall characteristics. While the centrifugal flow control system generated the expected mass flow, the impact on blade dynamic stall characteristics and rotor performance was less than desired. The rotor results are compared to those from the airfoil test and to prior flow control rotor tests.
Numerical Analysis of Dynamic Stall for Different Helicopter Rotor Flight Conditions
Authors:   ONERA, Richez François
Published: September 2024

Helicopter reaches its flight domain limit at high-thrust forward flight or maneuver with high load factors because of dynamic stall. This phenomenon is due to complex unsteady three-dimensional flow separation mechanisms that occur on the retreating blade. These flow separations can be of different natures depending on the flight conditions. This paper proposes to investigate numerically two significantly different cases of dynamic stall on a helicopter rotor in forward flight. The results show that the numerical simulation can capture the variations of section pitching moment associated with dynamic stall, for each of these two flight cases. A deep analysis of the numerical results allows to identify distinct flow separation regions appearing on the rotor disk. Similarities and differences are highlighted between the dynamic stall characteristics of these two rotor flight conditions.
The Effect of Laminar Flow on Rotor Hover Performance
Authors:   U.S. Army Aviation Development Directorate (ADD), Overmeyer Austin , Martin Preston
Published: September 2024

The topic of laminar flow effects on hover performance is introduced with respect to some historical efforts where laminar flow was either measured or attempted. An analysis method is outlined using combined blade element, momentum method coupled to an airfoil analysis method, which includes the full eᴺ transition model. The analysis results compared well with the measured hover performance including the measured location of transition on both the upper and lower blade surfaces. The analysis method is then used to understand the upper limits of hover efficiency as a function of disk loading. The impact of laminar flow is higher at low disk loading, but significant improvement in terms of power loading appears possible even up to high disk loading approaching 20 ps f . A optimum planform design equation is derived for cases of zero profile drag and finite drag levels. These results are intended to be a guide for design studies and as a benchmark to compare higher fidelity analysis results. The details of the analysis method are given to enable other researchers to use the same approach for comparison to other approaches.
Numerical Study of Retreating Side Blowing Concept for a Rotor in High Speed Flight
Authors:   United Technologies Research Center, Min Byung-Young ,   Sikorsky a Lockheed Martin Company, Lorber Peter , Wake Brian , Berezin Charles , Scott Mark
Published: September 2024

Retreating Side Blowing (RSB) is a concept to blow air through the blade to suppress dynamic stall on the retreating side of the rotor, and enhance a vehicle's flight envelope at high speed and high loading forward flight conditions. Passive RSB utilizes a rotating blade as a centrifugal pump to drive flow from the inlet at the root to the outboard region. Current numerical studies examined the effectiveness of RSB in conjunction with validation against wind-tunnel measured data at high advance ratio conditions. The impact of varying freestream velocity on the performance of a blown pitching airfoil was also examined using two-dimensional airfoil calculations. The variation and timing of the freestream velocity significantly decreased the stall suppression benefit of a blown airfoil versus a fixed freestream. The validation of three-dimensional rotor simulations showed good correlation with measured data in predictions of integrated performance, section loading, and duct flow properties. Both measured data and numerical simulation showed no significant performance benefit from RSB in the tested flight conditions. Detailed examination indicated the RSB was able to reduce retreating side separation, but pumping torque, geometric modification due to slots, and increased retreating side horizontal force overwhelmed the retreating side torque benefit. Additional numerical explorative studies showed that powered-blowing could achieve significant performance improvement from pure aerodynamic perspective. However, the additional blowing power cancelled out most of benefit. An inlet valve model for simulation of scheduled blowing was also studied, but meaningful benefit was not observed. The retreating side blowing was able to reduce aerodynamic sources of retreating side vibration torsional load. However, the peak blade torsional load emerged on the advancing side at high advance ratio conditions.
Individual Blade Control for Rotorcraft Using Mechanically Programmable Displacement Control
Authors:   Bell Helicopter Textron Inc., Fenny Carlos
Published: September 2024

The application of Higher Harmonic Control (HHC) and Individual/Independent Blade Control (IBC) offer the potential for significant improvements in rotary wing performance. Despite large investments by industry and government agencies over the past 20 years, a successful transition of HHC and IBC to a production aircraft has not yet occurred. Failures of prior IBC designs to achieve practical application has been attributed to deficiencies in existing material, mechanical power generation and system control technologies. Alternatively, the case can be made that prior IBC concepts failed due to their inherent design impracticality. The new IBC technology of Mechanically Programmable Displacement (MPDC) offers a rapid path to the practical implementation of an HHC/IBC system using currently existing proven technologies.
Dynamic Performance Assessment of Side Facing Troop Seats During Impact
Authors:   Air Force Research Laboratory, Wright Nathan , Burneka Chris
Published: September 2024

The Air Force Research Laboratory Aircrew Biodynamics and Protection Group of the Applied Neuroscience Branch (711HPW/RHCPT) conducted a dynamic impact comparative test program of currently-fielded side facing troop seats to evaluate how effectively the seats protect occupants ranging from the 5th percentile female to the 98th percentile male during crash events. The test program consisted of impact testing stock H-60A/L, CV-22, and CH-53E seats and quantifying the safety effectiveness of each seat using recommended injury criteria from the Full Spectrum Crashworthiness (FSC) report and other historical criteria. The program demonstrates a methodology to quickly and inexpensively compare occupant protection across different designs and platforms. The program also identifies serious structural and functional deficiencies of several operational seats that correlate with rotorcraft mishap injury and mortality data.
Pilot Head and Neck Response to Helicopter Whole Body Vibration and Head-Supported Mass
Authors:   National Research Council Canada, Law Andrew , E. Heather , Keillor Jocelyn , Wickramasinghe Viresh
Published: September 2024

Given the prevalence and severity of neck pain among helicopter pilots, the effects of helicopter whole body vibration (WBV) and pilot head-supported mass (HSM) on neck muscle strain and fatigue need to be understood to establish effective mitigating solutions and/or countermeasure protocols. The present study provides a preliminary assessment of pilot head and neck responses under different WBV conditions (i.e. Engines Off, Ground Idle, Hover, and Cruise) and HSM conditions (i.e. Helmet-only, Helmet+NVG) during flight operations on a Bell 412 helicopter. For both pilots, average neck electromyography (EMG) amplitudes were highest during the maximum WBV condition (Cruise) and the maximum HSM condition (Helmet+NVG). This indicates that helicopter WBV and HSM conditions jointly contribute to higher neck muscle loading, which may coincide with elevated neck muscle discomfort, strain, and fatigue. Therefore, effective mitigating solutions (e.g. vibration exposure limits, operational guidelines) must account for the combined effects of WBV and HSM to reduce or prevent neck pain among helicopter pilots.
3D-Sonification for Obstacle Avoidance in Brownout Conditions
Authors:   SJSU/NASA ARC, Godfroy-Cooper M. ,   NASA Ames Research Center, Wenzel E. ,   US Army Aeroflightdynamics Directorate - Ames Research Center, Szoboszlay Z. , Miller J.
Published: September 2024

Helicopter brownout is a phenomenon that occurs when making landing approaches in dusty environments, whereby sand or dust particles become swept up in the rotor outwash. Brownout is characterized by partial or total obscuration of the terrain, which degrades visual cues necessary for hovering and safe landing. Furthermore, the motion of the dust cloud produced during brownout can lead to the pilot experiencing motion cue anomalies such as vection illusions. In this context, the stability and guidance control functions can be intermittently or continuously degraded, potentially leading to undetected surface hazards and obstacles as well as unnoticed drift. Safe and controlled landing in brownout can be achieved using an integrated presentation of LADAR and RADAR imagery and aircraft state symbology. However, though detected by the LADAR and displayed on the sensor image, small obstacles can be difficult to discern from the background so that changes in obstacle elevation may go unnoticed. Moreover, pilot workload associated with tracking the displayed symbology is often so high that the pilot cannot give sufficient attention to the LADAR/RADAR image. This paper documents a simulation evaluating the use of 3D auditory cueing for obstacle avoidance in brownout as a replacement for or compliment to LADAR/RADAR imagery.
Parallel Implementation of Comprehensive Rotor Dynamics Simulation Based On the Motion Formalism
Authors:   University of Maryland, Sonneville Valentin , Bauchau Olivier
Published: September 2024

The use of a local frame motion formalism for finite element simulation of rotor dynamics leads to low order nonlinearity of the equations of motion. In order to exploit this reduced non-linearity, a domain decomposition strategy is implemented. The independence of the subdomains enables naturally parallel computations. The combination of these three key elements leads to significant savings in computational time, without compromising the accuracy.
Measurement of Transient Loads and Blade Deformation in a Coaxial Counter-Rotating Rotor
Authors:   The University of Texas at Austin, Cameron Christopher ,   Technical University of Munich, Feil Roland , Sirohi Jayant , Rauleder Jurgen
Published: September 2024

A model-scale, coaxial, counter-rotating rotor system with single-bladed rotors was tested in hover and compared to a comprehensive model developed in CAMRAD II. Measurements included vibratory hub and pitch link loads, as well as three-dimensional lower rotor blade deformations extracted using digital image correlation. The model flap dynamics were validated using a rotating frame modal extraction technique based on a modified Ibrahim Time Domain method. The CAMRAD model successfully predicted unsteady loads and deformations for the isolated lower rotor operated with cyclic pitch in hover. To investigate transient loads, measurements were taken in the coaxial configuration at a blade loading coefficient of 0.10 and for an isolated lower rotor at equivalent blade loading. The CAMRAD model accurately predicted the unsteady interaction thrust, as well as the blade flapping which was found to increase after upper-lower rotor blade passage. The CAMRAD model revealed aerodynamic forcing in the coaxial configuration consistent with vortex interaction of the upper and lower rotors, while higher harmonics observed in the experimental data were attributed to impulsive loading due to blade thickness effects.
Loads Prediction for a Gimbaled Tiltrotor in Conversion Flight Using CAD-Based 3-D Structural Analysis Models
Authors:   University of Maryland, Staruk William , Chopra Inderjit , Datta Anubhav
Published: September 2024

This paper presents a method for modeling gimbaled rotor dynamics under trim conditions in X3D, a next-generation 3-D finite element based rotor structural dynamics solver. The rotor is modeled using a free flap hinge at the hub with a single blade, the motion of which is suppressed at integer multiples of the Nb per rev, where Nb is the number of blades. This is accomplished by introducing harmonics of the joint rotation angle as additional trim variables. Rotor frequencies are examined for a three-bladed gimbaled rotor model and are found to combine the modes of both free flap hinge and fixed flap hinge (cantilevered) one-bladed rotor models, similar to the behavior of a teetering rotor, justifying the gimbal modeling methodology. Gimbal flapping is examined for a proprotor in edgewise flight: successfully suppression of steady and 3/rev flapping indicates the gimbal model is performing as intended. The 6/rev and higher harmonics are negligible to begin with for this case and are left uncontrolled, but the same method can also be applied to suppress them if required. Airloads and blade loads are examined with a free flap hinge blade with the gimbal model, revealing an increase in 3/rev sectional normal aerodynamic force on the blade but a decrease in 3/rev flap and lag bending moment when the gimbal is added. Three-dimensional axial stress distribution at the blade root is examined, revealing only minor differences between the two hub rotor models, primarily in the flexbeam.
Flight Testing of Coupled Collective toward Reducing Pilot Workload during Landing in DVE
Authors:   US Army ADD - AMRDEC, Lusardi Jeff , Fujizawa Brian , Morford Zachariah
Published: September 2024

Landing helicopters in Degraded Visual Environments (DVE) is one of the most challenging maneuvers pilots perform. The US Army Aviation and Missile Research, Development and Engineering Center (AMRDEC) has been working to develop flight guidance and sensor systems to provide the pilot with guidance and pilot displays to land a helicopter, hover, and take off in DVE. During flight testing of the Brown Out Symbology System (BOSS) on an EH-60L, pilots reported very high workload requiring full concentration on the displays during approaches to landing in brownout. In order to reduce pilot workload, an approach to provide the pilot with a collective tactile cue based on coupling of the output of the symbology display algorithms to the EH-60L collective trim servo has been developed and flight tested. Details of the system are provided along with the results of flight testing conducted at the Yuma Proving Grounds comparing workload from approaches to landing in brownout with and without the collective coupling engaged.
Pilot Control Behavior Model and its Model-Matching Procedure via Mission-Task-Element Flight Tests
Authors:   Turkish Aerospace Industries, Onur Can , Ture Umut , Akin Onur , Zengin Ugur
Published: September 2024

The Model-Based Pilot Controller (MBPC) had been developed to mathematically model pilot control behavior. Using optimal estimation and modern control theories, the MBPC takes the psychophysical limitations into account while modeling the multimodal control characteristics of a human operator. This paper herein discusses the validation process of the MBPC by conducting a set of Mission-Task-Element (MTE) experiments with a test pilot on a fixed-based flight simulator. The control activities of both the MBPC and the test pilot are compared in terms of pilot workload that is available through the frequency-domain-based metric, the power frequency. Three of the MTEs executed in this study reveal similar temporal workload variations for both parties, making the MBPC a promising tool to assess the handling qualities of a vehicle solely based on mathematical models of the system.
Joint Military and Commercial Rotorcraft Mechanical Diagnostics Gap Analysis
Authors:   US Army AMRDEC, Wade Daniel ,   Bell Textron Inc., Tucker Brian ,   Sikorsky Aircraft Company, Davis Mark ,   The Boeing Company, Knapp Doug ,   Airbus Helicopters, Hasbroucq Sophie ,   Leonardo Helicopters, Saporiti Moreno ,   HeliOffshore, Garrington Malcom ,   Canada Department of National Defense, Rudy Alexander
Published: September 2024

A group of rotorcraft original equipment manufacturers (OEMs) and military and commercial operators have come together to review the current state of mechanical diagnostics (MD) for on board rotorcraft Health and Usage Monitoring Systems (HUMS). HUMS has become an integral part of the modern rotorcraft both in commercial and military operations to enhance safety and enable Condition-Based Maintenance (CBM). Commercial oil and gas operators depend on the HUMS vibration monitoring and MD to comply with regulations and customer requirements for ensured safety of off-shore transportation. Under the auspices of the HUMS Technical Committee within the American Helicopter Society (AHS), the authors have assessed the performance of HUMS MD through both quantitative and qualitative means. First, results from the U.S. Army fleet, which comprises thousands of deployed HUMS on multiple aircraft models, were examined. Second, qualitative surveys of both commercial/military operators and rotorcraft/HUMS original equipment manufacturers (OEMs) were completed. Finally, a literature survey focused on HUMS research and development (R&D) and operational analysis was conducted. Based on this assessment, gaps in the performance of current HUMS MD, needs for future R&D, and challenges to closing those gaps are identified. Collaborative, pre-competitive efforts are also recommended to help close the gaps and generally raise the performance of HUMS MD to enable further enhancements to safety and to support expanded CBM initiatives.
Flight Testing of Health Management Technologies
Authors:   Sikorsky a Lockheed Martin Company, Brookhart Andrew ,   US Army Aviation Development Directorate - ADD, Lyman Chris , Davis Mark , Bates Preston , Cycon Jim , Pantelis Paul , Baker Treven , Bordick Nathaniel
Published: September 2024

The U.S. Army traditionally has used a time-based, on-condition maintenance paradigm that relies on at-aircraft inspections and periodic in-depth phased inspections to determine condition and ensure airworthiness. The result is a significant maintenance burden, both scheduled and unscheduled, and excessive aircraft downtime. The objective of the Aviation Development Directorate (ADD) and Sikorsky Aircraft Corporation (SAC) Capability-Based Operations and Sustainment Technology-Aviation (COST-A) program was to develop and demonstrate an integrated set of high value diagnostics, prognostics, and system health management technologies that reduce scheduled inspections and preventive maintenance while enhancing safety. More than two dozen Prognostics and Health Management (PHM) technologies across six primary rotorcraft systems (propulsion, drive train, airframe/structural, rotor, electrical, and vehicle management) were matured to technology readiness level (TRL) 6. These technologies were integrated into a prototype laboratory on-board system built around the Integrated Vehicle Health Management Unit (IVHMU) currently installed in all UH-60 Black Hawk aircraft and successfully demonstrated to perform concurrently in representative simulated flight scenarios, using playback data from healthy and faulty components. A subset of these technologies, jointly selected by ADD and SAC, was flight tested on an HH-60M aircraft to further reduce the risk of transitioning these technologies. This paper summarizes the flight-test efforts, with a focus on results obtained for the technologies under test. Upon deployment to the UH-60 aircraft fleet, these PHM technologies can enable the Army to transition to a more effective automated condition-based maintenance (CBM) paradigm.
Simulation Study and Degradation Test of Fluid Dampers Equipped with HUMS
Authors:   Hutchinson Aerospace, Shahosseini Iman , Nall John
Published: September 2024

This paper presents the simulation and test results of HUMS versus different failure modes performed on a fluid damper, i.e. UH-60 lead-lag damper, to assess its health condition versus simulated degradation. To study the damper performance and the influence of failure modes, the damper behavior was analyzed using hydro-mechanical modeling. Furthermore, a degradation kit was installed on the damper to verify and validate the model predictions. The damper equipped with HUMS, transmits via a RF radio the sensor data to the base computer where the data is post-processed, analyzed, and plotted in a graphical user interface (GUI). Based on the damper performance and pre-defined thresholds, the damper is color flagged as 'Healthy', 'Prepare for Service', or 'Service Time'. The results showed a good correlation between simulation and test measurements regarding both non-degraded and degraded dampers. Moreover, the developed GUI demonstrated the capability to monitor and track the damper health conditions in real time with sub-second delay.
Wear Sensors for Pitch Control Bearing Condition Based Maintenance
Authors:   New Hampshire Ball Bearings, Lewis Brandyn ,   Bell Helicopter, Tucker Brian
Published: September 2024

Self-lubricating rotor blade pitch control bearings are critical to safe operation and fleet readiness. However, detecting bearing liner wear can be subjective and time consuming. Standard measurement techniques could lead to unsafe operational conditions or poor bearing life utilization. Excessive inspections, unplanned downtime and poor part utilization may be driven for safety and result in increased cost. New Hampshire Ball Bearings (NHBB) has developed a novel new approach that provides clear indication of when a bearing should be replaced. An embedded bearing liner wear sensor is connected to an Ultra High Frequency (UHF) passive Radio Frequency Identification (RFID) communication device to communicate bearing status to a hand held reader. Status of each individual bearing is reported. This new technology will allow operators and maintainers to conduct bearing maintenance when it is required by actual bearing condition instead of a fixed schedule based on Condition Based Maintenance (CBM) systems. Application specific and component functional testing on the wear sensor system (conducted at NHBB) shows wear performance similar to traditional blade pitch control applications with no impact to overall system operational capabilities. NHBB and Bell Helicopter are collaborating to introduce this technology on the Bell 525 with flight testing tentatively planned for 2017. Future work on this project will focus on aircraft and maintenance system integration.
Overview of Bird Strike Modelling, Testing and Certification Approaches in Airbus Helicopters
Authors:   Airbus Helicopters, Vagnot Alice , Boyer Florent , Markmiller Johannes
Published: September 2024

Airbus Helicopters has succeeded to validate a numerical bird model based on the Smooth Particle Hydrodynamics method with the explicit dynamic finite element code RADIOSS®. For that purpose, the so-called building block approach was followed, based on numerous successive comparisons between simulation results and test measurements on increasing complex assemblies (rigid or deformable targets, metallic or composites parts). A satisfying level of predictability was obtained, proving that the code is able to capture the fluid-structure interaction, failure modes, impact loads and strains levels. Based on these studies, modelling methods have been defined. However, the accuracy of those highly complex simulations depend on extensive materials characterization test campaigns to develop the appropriate numerical models, and their domain of validity must be precisely defined.
High-Fidelity Simulations of the Interaction of Atmospheric Turbulence with Ship Airwakes
Authors:   The Pennsylvania State University, Thedin Regis , Kinzel Michael , Schmitz Sven
Published: September 2024

In the present work, the influence of a neutral atmospheric boundary layer (ABL) on a ship airwake is studied. The ship investigated is the Simple Frigate Shape 2 (SFS2), which is immersed into a large-eddy simulation resolved ABL. The ship is modeled using the immersed boundary method (IBM) to allow for complex geometry handling in the context of a Cartesian mesh. Uniform inflow cases are executed as baselines and overall good agreement with both previous CFD results using detached eddy simulation and experimental data from the Naval Surface Warfare Center (NSWC) are observed. Comparison of ABL and uniform inflow cases at the same Reynolds number provided insight into the fundamental topology differences present in real airwakes. It is observed that the velocities in a ship airwake are considerably different when exposed to an ABL, and this influence should be taken into consideration for dynamic interface modeling.
Aeroelastic Optimization of Composite Wind Turbine Blades using Variable Stiffness Laminates
Authors:   Rensselaer Polytechnic Institute, Ferede Etana ,   Delft University of Technology, Abdalla Mostafa ,   German Aerospace Center - DLR, Dillinger Johannes , Gandhi Farhan , Bussel Gerard
Published: September 2024

A variable stiffness composite optimization framework for wind turbine rotor blades is presented. The framework consists of a multi-fidelity approach for wind turbine rotor analysis, where both structural and aerodynamic constraints are considered during the optimization. The potential of twist coupled blades to regulate the power on stall controlled wind turbines is investigated by exploiting the characteristic of unbalanced laminates to induce twist coupling. A complete stiffness variation along the blade span is considered during the optimization, while using the cost of energy as the objective function. Results show that unbalanced laminates provide a greater capabilitiy (compared to balanced laminates) to reduce the cost of energy of stall controlled wind turbines by exploiting extention-twist and bend-twist coupling of composite blades.
Preparing for the U.S. Army's Improved Turbine Engine
Authors:   US Army ITE FVL PO, Plummer Ben , Smith Joan , Carter Casey
Published: September 2024

The U.S. Army's Improved Turbine Engine (ITE) Program (ITEP) will develop, integrate, test, and qualify the next generation turbo-shaft engine to be utilized in the Black Hawk (H-60) and Apache (AH-64E) helicopter fleets. The ITEP is a developmental program that will leverage the knowledge, technical expertise, and technological advancements gained during the Advanced Affordable Turbine Engine (AATE) Science and Technology (S&T) program. Because of the increased demand placed on the AH-64E and H-60 fleet over the last 15 years, the current engine can no longer produce the power necessary to execute rotary wing operations at the increased gross weights and in the unforgiving operational environments of the aviation lift and attack fleets. With changes in mission equipment packages driving continued airframe weight growth, power margins are decreasing and flight and sustainment costs are growing. While providing significant increases to power available, the ITE decreases sustainment costs relative to the current engine through advanced engine and sustainment technology. The ITE will fit inside the existing engine compartments of both the H-60 and AH-64E, but the enhanced ITE capability will require modifications to legacy aircraft. Integration trade study and analysis efforts were initiated with H-60 Black Hawk and AH-64E Apache platform Original Equipment Manufacturers (OEMs) to reduce Engineering and Manufacturing Development risk. These efforts are helping define the mechanical, electrical, and software impacts to the air vehicle systems, as well as aircraft and engine performance impacts, while helping control program costs associated with development, test, reliability, and maintainability.
Experimental Investigation of Shrouding on Meshed Spur Gear Windage Power Loss
Authors:   NASA Glenn Research Center, Delgado Irebert , Hurrell Michael
Published: September 2024

Windage power loss in high-speed gearboxes result in efficiency losses and increased heating due to drag on the gear teeth. Meshed spur gear windage power loss test results are presented at ambient oil inlet temperatures both with and without shrouding. The rate of windage power loss is observed to increase above 10,000 ft./min., gear surface speed, similar to results presented in the literature. Shrouding is observed to become more effective above 15,000 ft./min., decreasing power loss by 10% at 25,000 ft./min. The need for gearbox oil drain slots limits the effectiveness of shrouding on reducing windage power loss. Also, windage power loss is observed to decrease with increasing gearbox temperatures and to increase with oil flow. Windage power losses for the unshrouded meshed spur gears are 7x more than losses determined from unshrouded single spur gear tests. A 6x to 12x increase in windage power loss is observed comparing shrouded single spur gear data with shrouded meshed spur gear data. Based on this preliminary study additional research is suggested to determine the effect of oil drain slot configurations, axial and radial shroud clearances, and higher gear surface speeds on windage power loss. Additional work is also suggested to determine the sensitivity of windage power loss to oil temperature and oil flow. Windage power loss of meshed spur gears tested in both the shrouded and unshrouded configurations is shown to be more than double versus the same spur gears run individually in the same shroud configurations. Further study of the physical processes behind these results is needed for optimizing gearbox shrouds for minimum windage power loss.
Flow and Heat Transfer Simulation in a Splash Lubricated Bell 525 Accessory Gearbox
Authors:   Bell Helicopter Textron Inc., Mukherjee Siddhartha , Mueller Russell , Chakram Mukundhan
Published: September 2024

Operating temperatures in a drive system gearbox are impacted by multiple factors like mechanical power, operating environment, geometrical design and lubricant properties. Cooling and lubrication performance is critical to operation and durability. Oil properties like viscosity, specific gravity and thermal conductivity play a major role in determining the quality of lubrication inside the gearbox and the efficiency of waste heat exchange. The interaction of lubricating oil with gears and surrounding structures is however a complex multi-physical problem. Complete coupled modeling of the various micro and macro physical phenomena at play inside the gearbox is challenging and computationally expensive. For this reason, manufacturers have traditionally relied on experimental evaluations of prototype gear boxes for product development. A more desirable approach is to develop a full simulation capability to aid the design process and minimize development risk. To this end, a CFD methodology for the prediction of lubricating oil flow and heat transfer is developed. The methodology is applied and validated with the "splash lubricated" accessory gearbox of the Bell 525.
Future Advanced Rotorcraft Drive System (FARDS) Full Scale Gearbox Demonstration
Authors:   Bell Helicopter Textron, Chavez Andrea ,   US Army ADD, Baker Treven , Fetty Jason
Published: September 2024

The Future Advanced Rotorcraft Drive System (FARDS) program focused on improving the performance and affordability of current aircraft drive systems. During the course of the program eighteen enabling technologies were developed to achieve these objectives within an existing helicopter transmission system. The transmission system was designed to enhance the Bell 407 light commercial aircraft configuration which has a similar configuration to the OH-58D Kiowa Warrior. Full scale main rotor gearbox testing was completed in 2016, which demonstrated many of these enabling technologies to a Technology Readiness Level (TRL) of 6. The demonstration testing was designed to closely follow the civil certification process (similar to military qualification testing), and included gear tooth pattern development, gear tooth bending fatigue, endurance, and three loss-of-lubrication tests. This testing successfully demonstrated a significant improvement in drive system technologies. The developed technologies are now ready to transition to future rotorcraft, such as Future Vertical Lift.
Epidemiology of Helicopter Accidents: Trends, Rates, and Covariates
Authors:   Georgia Institute of Technology, Churchwell Jared , Zhang Katherine , Saleh Joseph
Published: September 2024

The objective of this work is to provide a better understanding of helicopter accidents (rates, trends, and covariates) and to identify areas that deserve careful attention for accident prevention. Several questions were here investigated, including: (1) whether there are differences in accident rates for helicopters with different number of main rotor blades? (2) whether different engine types are associated with different accident rates, controlling for number of blades? And (3) whether there are seasonality effects in helicopter accident rates? To this effect, Record Linkage of two Federal data sources, the FAA civil helicopter registration data and the NTSB accident data, enabled the investigation of these and other questions. First, the accident rates and trend analysis highlighted the safety challenges that continue to face helicopters (significantly worse track record than commercial airlines, passenger cars, and motorcycles). Second, it was found that helicopter accident rates vary by number of rotor blades. Third, one result upended traditional wisdom, which posited that reciprocating engines are associated with higher accident rates; in its stead, it was shown that helicopter accident rates vary with engine type and number of blades, and that turboshaft are associated with significantly higher accident rates than reciprocating engines for the 4-, 5-, and 6-bladed helicopters. Furthermore, it was shown that helicopter accident rates display seasonality effect. Statistical significance and possible confounders for these results were discussed. The issues here examined deserve careful attention from the helicopter community, and several topics were identified as important areas for future work. Any serious effort to improve helicopter safety will entail action on multiple safety levers, including design, operational, and policy/inspection-related ones. All of these actions should be evidence-based, and they will require better helicopter accident investigations and better flight data.
A Structural Perspective on U.S. Army Airworthiness Impacts Resulting from Changes in Rotorcraft Component Fatigue Strength, Loads, and Usage
Authors:   US Army Aviation Engineering Dir, E. Robert , Rogers Martin
Published: September 2024

This paper provides insight into the methods used by U.S. Army Aviation Engineering Directorate personnel to assess airworthiness impacts due to changes in loads, usage, or strength, and resulting effects on calculated safe-life retirement times. Statistical analysis of system reliability for overflight of the safe-life time for components with assumed failure distributions forms the mathematical basis for the method. Topics include failure rate, baseline failure rate, percent change in system level risk, immeasurable risk, and mathematical relationships between each. Results include figures to aid in visualization and tables to enable the reader to check an implementation of the method for specific examples. The paper presents the results of analysis used to derive Weibull slope parameters based on recently developed fatigue reliability methods and available mission loads spectra. Finally, the paper presents a new method to establish life factors required to convert retirement intervals with a delta failure rate (for an airworthiness impact) into retirement intervals with immeasurable risk. Modified life factors address special cases of incompatible confidence and analysis uncertainty.
High Speed Impact Testing of Thermoplastic Composite Plates
Authors:   TH Ingolstadt, Franke Florian ,   Airbus, Heimbs Sebastian ,   Siemens, Seidel Christian ,   SGL Carbon, Brudzinski Patrik-Vincent ,   ESI GmbH, Huehn Dominic , Burger Uli
Published: September 2024

This paper presents the methodology and results for ballistic impact testing of thermoplastic composite materials. Ten different materials are investigated. The impact behavior of Aluminum 6082 is used as a reference to compare the results. The impact tests are performed with a gas cannon. Force - time, displacement - time as well as velocity data are recorded. Analytic suggestions for the calculation of the penetration speed of the materials are compared with measured results. It can be seen that it is possible to calculate the penetration speed within a certain percentage of the measured value. Also, the absorbed energies during the penetration process are compared. The results show that glass fiber composites have a better impact material behavior than carbon fiber-reinforced composites (CFRP). Thermoplastic matrix systems are a cheap option for composites but they do not have a significant better high speed impact and damage behavior than duroplastic resins.
Automatic Fatigue Test Control System (AFTCS)
Authors:   Bell Helicopter Textron Inc., Ha Chi ,   Good Automation, DeWeese Albert , Wright Mark , Malone Kimberly , Killeen Chad , McBee Luke , Freeman Gregory , Hawkins Kameron
Published: September 2024

Bell Helicopter's next-generation Automatic Fatigue Test Control System (AFTCS) is presented. Fatigue testing places a helicopter part or specimen under repeated, controlled cyclic loading to determine if and when it will fail. A National Instruments PXIe embedded processor and LabVIEW software are used to control up to 48 linear/rotary hydraulic actuators in real-time. The actuators apply structural loads that are sensed by up to 256 strain gauges on the helicopter specimen. The structure and instrumentation respond to prescribed cyclic loads that range in frequency from 0.5 to 30 Hz, with a minimum resolution of 0.1 Hz. The fatigue test controller design is based on the well-known Linear-Quadratic-Gaussian control (LQG) methodology. Its feedback and filter gains are computed using a state-space model of the specimen identified separately. The controller computes any necessary changes in the actuator motions (at every time sample), maintaining acceptable margin between the measured and desired strain gauge responses. The system is demonstrated on a Bell Helicopter 429 tail rotor blade.
Validation of Simulated Ship Air Wake Effects on Helicopter Recoveries
Authors:   Royal Australian Navy, Jarrett David ,   Defense Science and Technology Group Melbourne, Manso Sylvain
Published: September 2024

The Royal Australian Navy completed a series of First of Class Flight Trials in 2015 to establish Ship Helicopter Operating Limitations for Australian Defence Force rotary wing aircraft to the Canberra Class Landing Helicopter Dock (LHD). A Risk Reduction Tool (RTT) was developed to understand the impact of LHD airflow behavior on rotary wing operations. Specifically, the tool combined a ship air wake, a flight dynamic and a Pilot Model to provide an indicative effect of the air wake on pilot controls throughout an MRH90 recovery evolution. A verification of this tool suggests that the RRT in isolation was not able to characterize the flight environment with sufficient fidelity to predict pilot workload during recovery operations to the LHD. However, the RRT improved upon the information provided through stand-alone ship air wake analysis and as such the tool is suitable as a risk reduction measure prior to flight testing.
Control Engineering Approach in Safety Management Systems
Authors:   Airbus Helicopters Inc., Girondin Victor , Morel Stephane
Published: September 2024

Safety Management Systems (SMS) are mainly based on an operational feedback approach for continuous safety enhancement. Closed loop approaches have been dramatically developed and applied in aeronautics by control engineers. In this article, SMS is redefined in terms of automatic control and this analogy leads to the identification of three classical feedback strategies. The theoretical effect of these strategies on performances is also discussed. As in any closed loop systems, the importance of understanding how the mission stakeholders react will be found to be particularly crucial. The last aspect of this analogy is discussed through quantitative SMS, or the standard use of SMS indicators. Several aspects of decision making and quantitative analysis are then discussed.
RFID Tag Implementation on Bell 525
Authors:   Bell Helicopter, McFarlane Cleve , Tucker Brian , Slatton Dennis
Published: September 2024

The basics of Radio Frequency Identification (RFID) are discussed relative to its use in aerospace. RFID governing standards are presented with the vision of its use in the Bell 525 commercial helicopter program. Specific challenges regarding RFID implementation for part marking on the Bell 525 are put forward. These efforts are a first in the rotorcraft industry, and have made RFID a reality on the 525.