bluuebunny/crossref_metadata_2025 huggingface dataset:
External Load Stabilization Control Laws for an H-6 Helicopter Testbed
Authors:   The Boeing Company, Patterson Byron ,   Aviation Development Directorate - AFDD US Army RDECOM, Ivler Christina , Hayes Pamela
Published: October 2024

A helicopter with an externally slung load represents a dynamic two-body problem where the pilot is required to manage the load motion in addition to normal flight operating tasks. One method of reducing the pilot workload for external load tasks is to control the load motion by providing feedback of the motion to the helicopter control laws. Under the Adaptive Vehicle Management System (AVMS) Phase II program, external load stabilization using feedback to the flight control system, termed the Flight Control Load Stabilization (FCLS), has been developed. The FCLS design includes two architectures: one improves load damping, and the other improves handling qualities. Development of the FCLS architectures consists of model correlation, design using the classic root locus technique, control law tuning by CONDUIT® optimization and a parametric study, and piloted simulation evaluation. The design technique proved effective in identifying two architectures and the associated settings for load damping and handling qualities improvements. Piloted simulation results attributable to the FCLS system indicate improved Cooper-Harper Pilot Ratings and time to completion for three ADS-33E-PRF Mission Task Elements.
Piloted Simulation Evaluation of a Robust Feedback Controller for Helicopters Handling Externally Slung Loads
Authors:   Sikorsky Aircraft Corporation, Rigsby James ,   Penn State University, Horn Joseph
Published: October 2024

This work reports on the design and piloted simulation evaluation of a feedback controller that utilizes measurements of the external load dynamic states to reduce load swinging, thereby increasing the precision with which an external load is handled. Results show a favorable impact on total mission-task-element time and load placement accuracy. Pilot ratings are favorable, but suggest that vehicle response types dominate the pilot's assessment of the task workload since the external load-stabilizing controller only provides load stabilization when the pilot controls are in detent.
Use of Redundant Controls to Enhance Transient Response and Handling Qualities of a Compound Rotorcraft
Authors:   The Pennsylvania State University, Horn Joe , Thorsen Adam , Ozdemir Gurbuz
Published: October 2024

This study investigates the transient response characteristics of a compound rotorcraft and seeks to establish methods of control that enhance handling qualities via the use of redundant control surfaces. Simulations of a hypothetical compound rotorcraft based on a UH-60A airframe and rotor compounded with a wing and pusher propeller are used. This study presents general background on the simulated compound rotorcraft model, the behavior of redundant controls in minimum power quasi-steady maneuvering flight, and then extends the analysis to focus on the transient response characteristics of the aircraft in various maneuvers. In addition to the four traditional controls, this study will examine the use of three redundant control effectors: propeller pitch, symmetric wing flap deflection, and differential wing flap deflection, which can be optimized for performance and handling qualities. Background material is presented for trim analysis of quasi-steady maneuvers to gain an understanding of the control allocation that minimizes power required in sustained maneuvers. The results of the optimization are incorporated into a g-command dynamic inversion controller to regulate longitudinal and vertical load factor in minimum power flight. Pull-up and turning maneuvers are simulated to analyze handling qualities both with and without redundant controls. Quickness metrics are investigated for pull-up and turning maneuvers to understand how the deployment of redundant controls might be used to enhance transient response and handling qualities.
Effects of Contrast and Spatial Frequency on Idealized Compensatory Tasks
Authors:   University of Maryland - College Park, Brown Daniel , Celi Roberto
Published: October 2024

The paper describes a series of experiments to quantify the effects of loss of contrast on highly-idealized, compensatory piloting tasks. The effects of spatial frequency are simultaneously studied via the Modulation Transfer Function (MTF). The MTF can quantify the contrast and spatial frequency (relative size) of the objects that provide visual cues necessary for closing pilot control loops. A brief analysis is also performed on different input devices and their effects on task performance. The results show compensatory task performance can be modeled with multiple MTFs, each representing a unique numeric characterization of the pilot response in a single task. The results also quantify the intuitively known fact that physiological limits of human vision directly correlate to piloting task performance. Therefore, the MTF may represent a key building block of quantitative, objective rotorcraft Handling Qualities metrics for Degraded Visual Environments (DVE).
Effect of Control System Augmentation on Handling Qualities and Task Performance in Good and Degraded Visual Environments
Authors:   San Jose State Foundation, Lawrence Ben ,   US Army AFDD, Blanken Christopher ,   NASA, Theodore Colin ,   Monterey Technologies, Lindsey James ,   UC Santa Cruz, Berger Tom , Tischler Mark , Malpica Carlos
Published: October 2024

In June 2013, NASA and the U.S. Army jointly conducted a simulation experiment in the NASA-Ames Vertical Motion Simulator that examined and quantified the effects of limited-authority control system augmentation on handling qualities and task performance in both good and degraded visual environments. The vehicle model used for the experiment was the OH-58D with similar size, weight and performance, and the same 4-blade rotor system as the Bell 407 civilian helicopter that is commonly used for medical evacuation and emergency medical services. The control systems investigated as part of this study included the baseline aircraft Rate Command system, a short-term Attitude Command/Attitude Hold system that uses lagged-rate feedback to provide a short-term attitude response, Modernized Control Laws that provide an Attitude Command/Attitude Hold control response type, and Modernized Control Laws with an additional Position Hold function. Evaluation tasks included the ADS-33 Hover, Sidestep, Acceleration/Deceleration, and Pirouette Mission Task Elements, as well as a new proposed Emergency Medical Services task that includes an approach and landing at a minimally prepared remote landing site. Degraded visual environments were simulated with night vision goggles and an unaided night scene. A total of nine experimental test pilots participated in the four-week simulation experiment. Data recorded during the evaluation included Cooper-Harper handling qualities ratings, Bedford Workload scale ratings, and task performance. The Usable Cue Environment (UCE) was measured for this simulation experiment, and found to be UCE=1 in good visual environments and UCE=2 in degraded visual environments with night vision goggles. Results showed that handling qualities ratings were improved with a control system providing short-term attitude response over a rate command system, although the improvements were not sufficient to produce Level 1 handling qualities in degraded visual environments. Results for an Attitude Command/Attitude Hold control system showed that borderline Level 1 handling qualities could be achieved in degraded visual environments, and the 10% authority stability augmentation system was adequate to obtain these handling qualities ratings.
Investigation of Novel Concepts for Control of a Personal Air Vehicle
Authors:   University of Liverpool, Jones Michael , Perfect Philip , Jump Michael , White Mark
Published: October 2024

This paper reports results from a study to investigate the use of novel control systems designed to provide a safe and reliable method for the control of a future Personal Aerial Vehicle (PAV). Previous research into vehicle response type requirements, conducted within the EC FP-7 project myCopter, has centered around 'conventional' rotorcraft-type control configurations. In this paper, the use of response and control characteristics derived from road vehicles is investigated. Objective and subjective techniques are used to quantify and qualify the applicability of automobile-like response characteristics using traditional helicopter control inceptors modified to behave somewhat like automobile controls, using foot pedals to control an Acceleration Command, Speed Hold system, for example. Additionally, the effects of eliminating vehicle pitch and roll dynamics are investigated to determine whether this allows a reduction in workload for non-professional pilots. Results suggest that, particularly for the most inexperienced of pilots, the automobile-like configuration is more suitable for control of a PAV than an augmented set of helicopter-style response types. This is shown through increased performance, and a reduction in subjective NASA Task Load Index (TLX) ratings. Improved Handling Qualities Ratings (HQRs) were also obtained in the automobile-like system for the tasks undertaken. Overall, removal of pitch and roll dynamics was not found to significantly affect task performance in the automobile-like system, but their absence resulted in a decrease in performance for the rotorcraft-style response type configurations tested.
An Interview with Colonel Floyd Harold "Hal" Kushner, M.D., F.A.C.S U.S. ARMY Flight Surgeon and Vietnam Prisoner of War
Authors:   US ARMY (Retired), Fardink Paul
Published: October 2024

No Abstract
A Historical Investigation of the Mission Requirements and Enabling Technologies Influencing the Development of Unmanned Rotary-Wing Aircraft
Authors:   Avericon LLC, Pereira Jason ,   UASX, Bruce Scott
Published: October 2024

The earliest unmanned rotary wing aircraft were models that were used as toys, or to develop the technology required for larger and manned helicopters. Some of the earliest model helicopters lead to the technological insights required to develop manned helicopters. The first significant widespread operational use for fixed wing unmanned aircraft came out of the radio control/model aircraft industry and was adapted for use as a gunnery target. On the other hand, it was the unique hovering capability of the helicopter that lead to adapting a small manned helicopter, the Gyrodyne co-axial Rotorcycle, for shipboard anti-submarine operations. There was somewhat of a lull in Rotary Wing Unmanned Aircraft Systems during the 1970's and 1980's. But the refinement of a few key technologies has led to a resurgence of development starting in the 1990's as precise autonomous control and autonomous landing capabilities were refined. Since 2000, the development of the quadrotor and other significant enabling technologies has led to the capability for a very small team to develop a very capable, very cost-effective small Rotary Wing Unmanned Aircraft System.
A Novel Gear Condition Monitoring Method Based on Transient Impulse Response
Authors:   NASA Glenn Research Center, Dempsey Paula ,   United Technologies Research Center, Chen Yan , Chaudhry Zaffir
Published: October 2024

In this paper a new method for gear condition monitoring is presented. The method exploits the system transient dynamic response due to impulse-like excitation produced by the repetitive gear meshing. The transient response pattern is easily observed at the underlying system or subsystem's natural frequency, also referred to as the "carrier frequency". At these carrier frequencies, the vibration magnitude is directly related to the intensity of the meshing force impulse, which is implemented as a condition indicator. Also, the modulation frequency of the filtered vibration at the "carrier frequency" can be used to determine the source of the component modulating the output. Four gear vibration data sets from a spiral bevel gear test rig at NASA Glenn Research Center were analyzed. The condition indicator (CI) based on transient impulse response method (TIRM) was competitive with other prevalent condition indicators in providing effective detection of the gear damage severity, and offered superior performance in locating the damage source in the gear/pinion pairs.
Vertical Lift Aircraft Rotor and Blade Mechanical and Dynamic Fault Detection in the field through the use of Revolution to Revolution Blade Track Data Analysis
Authors:   Swangate International, Mesec Gilbert
Published: October 2024

Rotor and blade fault detection using optical blade tracking revolution-to-revolution data is described in this paper. The process allows analysis of the dynamic health of an individual blade and its attachments, indicates rotor eccentricities, and faulty collective and cyclic functions. The process is detailed in US Patent 8,041,520 B2 issued October 18, 2011. Smoothing algorithms are applied to the data to remove sensor and rotor induced motion. The data are then reordered by amplitude ranging from most positive to most negative. Forced motion values are then at the extremes of the data set placing the normal range of motion about the median value of each data set. Identification of forced motion; e.g., pilot control input, meteorological disturbances, etc., and normal unforced motion is critical for fault analysis. Motion analysis aids blade and rotor fault discovery and repair. The process can be used for recovery of faulted blades in the field.
Aircraft Wire Fault Detection and Isolation using Spread Spectrum Time Domain Reflectometry
Authors:   Impact Technologies - A Sikorsky Innovations Company, Drost Brian ,   US Army Aviation Development Directorate, Thompson Bruce ,   Sikorsky Aircraft, Mastrianni Mike
Published: October 2024

The electrical wire harness system on a modern aircraft is one of the most complex, integral, and hardest to troubleshoot. One of the goals of the COST-A electrical system effort is to develop an approach to monitor wiring at the aircraft level in flight. A number of sensor technologies were studied as well as existing aircraft data that might be used to assess wire integrity and minimize the number of sensors required. The sensor technology selected for further evaluation and validation during the program was the spread spectrum time domain reflectometer (SSTDR). It would be impractical to add a sensor to every wire path. Therefore, sensor data is leveraged with existing electrical health data such as built in test (BIT), and constraint based logic is used to render a comprehensive view of the wiring health of the aircraft. During flight and BIT collection intervals, shorts, opens and intermittents are detected for analysis. After the aircraft lands, this data is processed in the aircraft ground station to provide fault isolation and troubleshooting guidance to the maintainer.
Airframe Structural Integrity Management: A UH-60 Application and Demonstration
Authors:   Sikorsky Aircraft Corporation, Brookhart Andrew ,   US Army Aviation Development Directorate - AATD, Bordick Nathaniel , Bates Preston
Published: October 2024

Sikorsky Aircraft Corporation (SAC) and the U.S. Army Aviation Development Directorate-Aviation Applied Technical Directorate (ADD-AATD) are jointly sponsoring the Capability-Based Operations and Sustainment Technology-Aviation (COST-A) technology development program. The objective of COST-A is to demonstrate an integrated set of high-value diagnostics, prognostics, and system health management technologies that reduce the maintenance burden while maintaining safety of six different rotorcraft systems, including the structural system. This paper describes the formulation of a system and method to manage the structural integrity of rotorcraft airframe structure. Current maintenance practices designed to ensure structural integrity are based on intensive scheduled visual inspection activities and could be adapted to be risk-driven, using inputs from a structural integrity management system. The system combines usage, load and climate histories, fused with focused sensors and modeling to provide a risk based assessment of a rotorcraft's structural integrity. The system was demonstrated through full-scale fatigue and impact testing of a UH-60A cabin roof in a representative environment. Extensions of the developed system to other areas of the airframe and other aircraft are discussed to demonstrate the possible applications of the matured technology.
V-22 Dynamic Components Fatigue Design Usage Spectrum vs. Fleet History
Authors:   Bell Helicopter, Kelly Stacey
Published: October 2024

A critical task for initiating an aircraft design is to determine how the fielded product will be used. For the V-22 Osprey, a usage spectrum was developed. The spectrum considered time spent in level flight, number of maneuvers per flight hour, type of maneuvers that would be flown, etc. With the V-22 fleet now exceeding 200,000 flight hours the actual usage spectrum can be compared to the design spectrum to gain key insights. The V-22 onboard recording system includes maneuver recognition software that permits this analysis. Results from fleet usage data are compared to the design usage spectrum to show areas where the original design spectrum is conservative and where it was not. The differences show how a usage-based appraisal of fatigue effects can be used for determining replacement intervals of life limited components.
Automating Rotorcraft Parts Life Tracking using RF rechargeable semi-passive RFID
Authors:   Benz Airborne Systems, Augustin Mike ,   Navy, Phan Nam , Sanzone Charles , Coleman Bud , Liebschultz Daniel
Published: October 2024

The reliability of manually tracking life critical components on rotorcraft over their operational lifetimes has been troublesome. The accepted system is subject to human errors involved in keeping up with the configuration of installed fatigue critical components. The identity of installed components whether found on component name plates or hand scribed into the parts themselves are not always transferred correctly by responsible personnel into the maintenance tracking system. Even where 2D barcodes are now used, the location and accessibility of the parts, their low readability due to continuous exposure to in-service dirt and grime, and the inability of fixed markings to carry maintenance, condition, and usage date on each component make even this more recent approach lacking. Most importantly, no mechanism exists to automatically transfer this critical airworthiness data to the health and usage monitoring systems currently installed on a growing number of modern rotorcraft models. The use of Radio Frequency Identification (RFID) based component tracking has the potential to eliminate many of these problems and insure that all component maintenance data is available, even if the aircraft must operate for extended periods without access to a network as is often the case when helicopters operate in remote areas. Passive UHF RFID Tags of an acceptable size for this application have read range limitations which do not allow the best design approaches to be taken. This paper investigates an alternative design using a novel semi-passive RFID design approach.
Effects of Structural Properties on Rotor Airloads Prediction Based on CFD/CSD Coupling Method
Authors:   Nanjing University of Aeronautics and Astronautics, Wang Junyi , Zhao Qijun
Published: October 2024

For accurate aeroelastic analysis, the unsteady rotor flowfield is solved by Computational Fluid Dynamics (CFD) module based on RANS/Euler equations and moving-embedded grid system, while Computational Structural Dynamics (CSD) module is introduced to handle blade flexibility. In CFD module, dual time-stepping algorithm is employed in temporal discretization, JST scheme is adopted in spatial discretization and B-L turbulent model is used to introduce the viscous effect. The CSD module is developed based on Hamilton's variational principles, moderate deflection beam theory and advanced geometric blade-tip analysis. Grid deformation is implemented using algebraic method through coordinate transformations to achieve deflections with high quality and efficiency. A CFD/CSD loose coupling strategy is developed to transfer information between rotor flowfield and blade structure. The CFD and CSD module is validated respectively, then the CFD/CSD loose coupling is adopted in airloads prediction of UH-60A rotor under high speed forward flight condition and the calculated results are compared with test data which show good agreements. Finally, effects of torsional stiffness properties on airloads of rotors with different tip swept angles (from 10 degree forward to 30 degree backward) are investigated. The results are evaluated through pressure distribution and airloads variation, and some meaningful conclusions about the moderated shock wave strength and pressure gradient caused by varied tip swept angle and structural properties are drawn.
An Assessment of RCAS Performance Prediction for Conventional and Advanced Rotor Configurations
Authors:   Science and Technology Corporation, Ho Jimmy ,   US Army, Jain Rohit , Yeo Hyeonsoo , Bhagwat Mahendra
Published: October 2024

The US Army's Rotorcraft Comprehensive Analysis System (RCAS), was validated for aerodynamic performance for a variety of isolated rotor configurations in hover and forward flight. Validation cases included a wide variety of key rotor configurations, covering various scales (small-scale to full-scale), twist distributions (zero twist, moderate linear twist, non-linear twist, and high non-linear twist), tip shapes (rectangular, swept, swept-tapered, tapered, and anhedral), and flight conditions (hover to high-speed forward flight). A free-vortex wake model was used for hover performance, while a prescribed vortex wake model was sufficient for forward flight performance. The validation study showed good correlation with test data using the best practices for the vortex wake modeling parameters.
Evaluation of Laminate Quality for Out of Autoclave Manufacturing for a Complex Shaped Crew Door
Authors:   Bell Helicopter Textron Canada, Quinlan Erin ,   University of British Columbia, Farhang Leyla ,   Concordia University, Desai Rajan ,   McGill University, Hughes Stella ,   Delastek, Héroux Stéphane , Kay James , Fernlund Goran , Hoa and , Kratz James , Smith Adam , Centea Timotei , Hubert Pascal
Published: October 2024

This paper summarizes a industry-academic collaborative project to evaluate Out-of-Autoclave (OOA) prepreg material and its behavior during processing of complex parts. This was done by manufacturing two crew door demonstrator parts; one made from traditional epoxy autoclave cure prepreg while the other was with OOA prepreg. The goal was to evaluate the main differences between manufacturing with OOA prepreg versus standard prepreg material. The results from this study showed the impact of using sharp radii and difficult corners for both processing methods. Ultimately, this project established the capability to manufacture a part with OOA material that was of similar quality to the part manufactured with the traditional epoxy prepreg material.
Conuduction Heating for Adhesive Bonding of Rotorcraft Primary Structure
Authors:   Bell Helicopter Textron Canada, Verdino Joseph ,   National Research Council of Canada, Hind Simon , Djokic Drazen , Yousefpour Ali
Published: October 2024

A final stage in the manufacturing of a rotorcraft structural article is presented. A single-part composite skin is stiffened with a series of pre-cured composite frames. Legacy designs feature either mechanically fastened metallic skin and frames, or longitudinally split composite skin bonded and fastened to composite frames. In the new design, all frames are simultaneously bonded using a high-performance, thermally-activated film adhesive. No fasteners are used. This approach improved the load transfer, damage tolerance, and part count. The success of this complex bonding operation is highly dependent on the control of the process parameters, mainly the bondline temperature. Required temperature uniformity across all bondlines was achieved by independently controlled conductive Heat Transfer Tiles (HTT's) dedicated to each frame. The National Research Council's HTT technology delivers non-uniform heat flux based on variable thermal boundary conditions which results in improved temperature uniformity compared to traditional heater blankets. Custom HTTs, control system and fixturing were evaluated and used to manufacture seven test articles. The success of the exercise was confirmed by process data, non-destructive, destructive, and full-scale testing.
Development of Thermoplastic Composite Cones for Helicopter Tail Boom Application
Authors:   Bell Helicopter Textron Canada Limited, Quinlan Erin ,   McGill University, Hubert Pascal ,   Concordia University, Hoa Suong , Beaulieu Pierre , Dion Michel , Shadmehri Farjad , Cai Xiao , Simpson Jeff , Hojjati Mehdi
Published: October 2024

Thermoplastic composites offer many attractive characteristics such as no shelf life, high fracture toughness, high temperature resistance, recyclability etc. The short coming of thermoplastic composites is their high viscosity, even at processing temperature. Due to the high viscosity, techniques for the manufacturing of thermoplastic composite have been limited to molding processes such as compression molding, high temperature stamping, where high temperature, high pressure and long duration are used. The advent of automated fiber placement machine brings forward possibilities to manufacture of large thermoplastic composite components. This is due to the fact that heating and compaction is done on the go directly on the surface of the substrate, and the flexibility of the feeding head to conform to the shape of the mold. It is in the spirit of exploration for new manufacturing possibilities that Bell Helicopter has supported an inter industry- university project for the development of thermoplastic composite cones aimed at helicopter tail boom applications. The cone represents a segment of the helicopter tail boom. It is made using carbon/PEEK material and automated fiber placement. The work consists of the Determination of the lay-up sequence to address the loads, the Development of the manufacturing processes, the Measurement of temperature variation during the making of a ring, the Checking of the quality of the cone, Development of tube bending test set up, Development of theoretical calculations to determine the buckling load of the cone subjected to bending, Testing the cone under bending load, and Comparing the experimental buckling with calculated buckling load.
Compression Molding of Composite Tailboom Frames
Authors:   National Research Council Canada, Yousefpour Ali ,   Bell Helicopter Textron Canada Ltd., Beaulieu Pierre , Roy Steven , Bednar Felix
Published: October 2024

Composite helicopter tailboom frames were manufactured by compression molding using a carbon fiber thermoset bulk molding compound. A mold was designed for compression molding and installed in a hydraulic press. The mold features two shear edges, guide pins and an integrated part ejection system. A material preforming method was developed to improve consistency in material distribution, which improved process robustness. A number of parts were produced and inspected for void content and dimensional stability. No significant porosity or voids were found in the samples examined. Part thickness uniformity was studied and improved, in order to meet the required tolerances. Dimensional inspection before and after a free standing post cure showed no significant part distortion. This work showed that compression molded tailboom frames are a viable alternative to current tailboom frames using continuous pre-impregnated fabric materials and cured by autoclave. This alternate processing method has the potential to reduce touch time and manufacturing costs.
Physics-Based Modeling of Viscous Ground Effect for Rotorcraft Applications
Authors:   Advanced Rotorcraft Technology Inc., Zhao Jinggen , He Chengjian
Published: October 2024

In this paper, a physics-based flow solver was used to address the challenging rotor wake and interference problems for rotorcraft operating in ground effect (IGE). The flow solver combines a state-of-the-art viscous vortex particle method (VPM) with a viscous ground model. VPM is based on the incompressible Navier-Stokes equations and adopts a grid-free Lagrangian formulation, which makes it well suited for aerodynamic interaction simulations to address complex rotor/ground interaction problems. The viscous ground model is applied to effectively enforce the no-slip unsteady boundary condition in VPM in a very efficient manner. With the enhancement for the viscous ground model, VPM accurately handles the physical no-slip boundary condition for both moving and static ground surfaces, which is missing in most image-based ground effect models. This paper discusses the detailed formulation and implementation of the viscous ground model in VPM. The flow solver thus developed was used to simulate various challenging aspects in the modeling of the rotor ground effect, which include the rotor tip vortex dynamics, the ground vortex structure, the rotor performance in hover and forward flight, the moving/static ground effect, and the rotor outwash and flow field. In addition, the impact of the interference between the main/tail rotors and the ground vortex on the tail rotor performance was also studied. Simulation results were compared with available measurements and excellent correlations were obtained from the current physics-based modeling technology.
A Novel, High Fidelity 6-DoF Simulation Model for Tethered Load Dynamics
Authors:   Georgia Institute of Technology, Prosser Daniel , Smith Marilyn
Published: October 2024

A novel, physics-based reduced-order model for the simulation of tethered loads and other dynamic bluff bodies in six-degree-of-freedom motion has been developed. The reduced-order aerodynamic model is founded on physical insights and supporting data from quasi-steady computational fluid dynamics simulations, experiments, or flight tests. The reduced-order model incorporates quasi-steady aerodynamics, unsteady vortex shedding phenomena, and unsteady aerodynamic effects of body motion. The reduced-order model accurately reproduces dynamics predicted by computational fluid dynamics simulations, while computational cost is reduced by more than five orders of magnitude. The methodology can readily be applied or extended to any bluff body geometry beyond those demonstrated in this work. Guidance is provided for the relatively minor modifications to include rotor downwash, atmospheric turbulence, and wind tunnel walls.
Simulation of Coupled Helicopter-Slung Load-Pilot Dynamics
Authors:   Technion - Israel Institute of Technology, Rosen Aviv , Enciu Kobi
Published: October 2024

A nonlinear simulation of a helicopter carrying a fin stabilized underslung load was developed. A human pilot model was incorporated in the simulation, for the study of the dynamics and stability of the combined helicopter-slung load-pilot system. Simulation results and their subsequent analysis show that the underslung load is stabilized by the helicopter. Analysis using extended bifurcations confirms observations from flight tests regarding the critical role of the piloting technique in determining the system's stability. Pilot attempts to counteract load lateral oscillations by applying lateral stick commands, turn the system unstable and result in pilot induced oscillations. Freezing the lateral stick causes load oscillations to completely decay, or damp down to very low residual amplitudes. Pilot time delay is found to be the main factor affecting the system's instability.
Investigation of Ship Airwakes Using a Hybrid Computational Methodology
Authors:   Georgia Institute of Technology, Quon Eliot ,   Continuum Dynamics Inc., Whitehouse Glen ,   Naval Surface Warfare Center Carderock Division, Rosenfeld Nicholas , Smith Marilyn , Cross Philip
Published: October 2024

The simple frigate shape geometry (SFS2) has been studied in free-air and wind tunnel environments for both headwind and yawed flow configurations. The ability of an unsteady Reynolds-Averaged Navier-Stokes (URANS) solver and a URANS/Vorticity Transport hybrid computational methodology to capture the bluff body wake characteristics has been assessed. Comparisons have been made with two different SFS2 experimental data sets, including new data from the Naval Surface Warfare Center Carderock Division. Overall good agreement between the hybrid and traditional URANS approaches was observed. Complex wake interactions were captured by the computational methodologies, and they have been assessed to provide insight into differences between the computational and experiment results. The influence of the unsteady vortex shedding from the bluff hangar has been characterized with respect to the changes in the flow field at hangar height and along the landing deck.
Helicopter Downwash Effects on Ship Airwake: Predictions, Modeling from a Database, and Simulation
Authors:   Florida Atlantic University, Schau Kyle ,   Naval Air Warfare Center Aircraft Division, Polsky Susan , Gaonkar Gopal
Published: October 2024

Helicopter downwash impact on ship airwake is addressed from a three-pronged approach: 1.) Predictions of one-point statistics of autospectrum and two-point statistics of cross-spectrum and coherence from a Computational Fluid Dynamics database of flow velocity predictions; 2.) Development of a mathematical framework for extracting interpretive autospectral models in closed form from a database; 3.) Simulation through white-noise-driven filters for the extracted models. The framework begins with an earlier-exercised perturbation series expansion of the autocorrelation for all three velocity components, and the first term of the series has a form of the von Karman longitudinal or lateral correlation function. After transformation into equivalent series of autospectrum, the perturbation coefficients are evaluated by satisfying the theoretical constraints and fitting a curve on a set of selected autospectral data points generated from the database. These constraints ensure that the extracted models and the autospectral data points have the same time scale, intensity, energy, and asymptotic decay according to the Kolmogorov -5/3 law. The framework represents a sensible combination of series expansion, exploitation of a database, and theoretical constraints to provide a foothold on airwake-downwash phenomenon for engineering analysis. The framework's strengths and weaknesses and its advancement over the earlier series-expansion schemes are also included. Downwash increases airwake energy by one order of magnitude, and all of this airwake-downwash energy is concentrated within the bandwidth ( 0 < f (Hz) < 1.6 that affects flight mechanics.
Simulation Methods Used In the Development of the Quiescent Period Prediction Systems for the Royal Navy
Authors:   MoD DES Maritime Combat Systems, Curnow Allan ,   Hoffman Engineering Corp, Ferrier Bernard ,   MoD Defence Equipment and Support - Maritime Combat SystemsD, Duncan Jamie ,   University of Exeter, Belmont Michael , Duncan John
Published: October 2024

Simulation technology has been used effectively and extensively across many NATO nations over the past 10 years to measure performance and support the management and reduction of risk across a wide range of ship acquisition projects. Clear emphasis is being placed on managing and reducing project risks, particularly during the design stages, to minimise the likelihood of cost and time overruns. The use of simulation is routinely considered in the UK, as an alternative to traditional approaches such as scale model testing and full scale sea trials, to predict the safety and performance envelopes of platforms and systems. A NATO programme of work known as NIREUS, which is being led by UK, is now considering the use of simulation to justify and develop Quiescent Period Prediction (QPP) Systems for navies. The ability of shipboard communities to safely conduct motion sensitive tasks in high sea states is an on-going concern. It is known that in high sea states there are periods in which the ship's motion is quiescent. The purpose of NIREUS is to provide ship motion conditions and predict future ship motion with sufficient time to launch, recover and complete other motion sensitive tasks regardless of the seaway. The objective is to expand ship operating deck limits. Based on lessons learned from the use of QPP, it is conceivable, that once integrated, shipboard communities could operate in much higher sea conditions for example recovering air and sea vehicles with elevated confidence and reliability. The basis of a real QPP system is to use a wave sensor to measure the wave field ahead of the ship, so that the ship's motion can be predicted well ahead of the wave field reaching the ship. This prediction can be mapped to a speed-polar representation of the seaway around the vessel permitting ship's crew to modify ship's heading and speed to ensure the best ship condition to complete motion sensitive tasks at hand. The proposed QPP system is composed of verified/validated measurement devices reducing the need for extensive certification and testing formalities. Activities requiring either significant length of time to complete or is particularly sensitive to ship's motions, would significantly benefit from a QPP system. Several examples are presented highlighting deck recoveries of both air and sea vehicles in up to 5 metre significant wave height.
Tactics, Techniques, and Procedures to Extend Component Remaining Useful Life based on Aircraft Maneuvers
Authors:   Bell Helicopter, Conrad Kevin , Love Alan , Tucker Brian , Marin Juan , Doubet Dustin
Published: October 2024

Sustainment Operations rely on reliability centered maintenance approaches to determine component retirement regardless of actual remaining useful life. With maintenance actions accounting for a significant portion of overall operating costs, operators seek approaches that maximize service intervals. Integrated Vehicle Health Management concepts afford an adaptive approach that can reduce the frequency of required maintenance actions based on proactively managing the damage incurred during flight operations. Tactics to gain airworthiness approval for extending remaining useful life and instructions for maintaining continued airworthiness are proposed. Techniques to identify, quantify, substantiate, and validate component failure rates for basic flight maneuvers are discussed. Finally, a pilot cueing system and the procedures for recommending pilot actions to manage health during flight operations are presented.
Predictions of Rotor and Rotor/Airframe Configurational Effects on Brownout Dust Clouds
Authors:   University of Maryland - College Park, Govindarajan Bharath , Leishman J.
Published: October 2024

Brownout dust cloud simulations were conducted for rotorcraft undergoing representative landing maneuvers, primarily to examine the effects of different rotor placement and rotor/airframe configurations. A time-dependent free-vortex wake for the rotors and surface singularity method for the airframe was employed to represent the carrier phase of the flow. A rigorous coupling strategy for the free-vortex method was developed to include the effects of rotors operating at different rotational speeds, such as a tail rotor. For the dispersed phase of the flow, particle tracking was used to model the dust cloud based on solutions to a decoupled form of Basset-Boussinesq-Oseen equations appropriate to dilute gas–particle suspensions of low Reynolds number Stokes flow. Various techniques were explored to reduce the computational cost of the dust cloud simulations, such as particle clustering and parallel programming using graphic processor units. The predicted flow fields near the ground and resulting dust clouds during the landing maneuvers were analyzed to better understand the physics behind their development, and to examine differences produced by various rotor and airframe configurations. Metrics based on particle counts and particle velocities in the field of view were developed to help quantify the severity of the computed brownout dust clouds. The presence of both a tail rotor and the fuselage was shown to cause both local and global changes to the aerodynamic environment near the ground and also influenced the development of the resulting dust clouds.
Conducting Helicopter Operations in Northern Labrador and the Arctic
Authors:   Universal Helicopters Newfoundland and Labrador LP, Goodyear Geoff
Published: October 2024

While helicopters are used for a myriad of purposes in rural and urban environments, their true potential can be measured by the support they can offer in extreme and remote areas. This paper describes a Northern Canadian operator, Universal Helicopters Newfoundland and Labrador LP, the equipment used, the tasks performed, the working conditions and the risks and challenges faced . The principal areas of operation include the Province of Newfoundland and Labrador, the Ungava Peninsula and Canada's high and eastern Arctic. The company operates 19 light and intermediate helicopters in one of the most challenging environments in the world. The aircraft are equipped with operational equipment and accessories for operation in temperature extremes which test not only the machinery but the crews that fly and maintain them. A Safety Management System is in place to properly identify and manage the unique risks of operating in the north as well as logistical support that recognizes associated added costs. The presence of multiple aircraft and their adjacency to remote communities often results in requests from authorities to assist in Search and Rescue operations. Despite challenges from wildlife, weather, topography and a long distance supply and communications chains, operators are able to conduct helicopter operations to support scientific research and natural resource development.
Hydrodynamic Characterization of a Sonar Body for Rotorcraft-based Towing
Authors:   United States Naval Academy, Falls Jaye
Published: October 2024

This paper describes experimental measurements of a fully submerged body designed to be towed by a helicopter. The goals of the tow tank testing program are (1) to characterize the towed body model so that a hydrodynamic lookup table can be constructed for a simulation, and (2) to provide measurements and observations that can validate the simulation. In this phase of the experimental investigation, the towed body model was first mounted on a rigid sting, and hydrodynamic forces were measured for a range of speeds, pitch angles and yaw angles. It was shown that using the mechanically practical Froude scaling method can produce reliable force coefficients for the range of Reynolds number at which the full scale towed body is likely to operate. A second series of tests towed the model from a cable, and demonstrated that cable slack will produce transient motions of the towed body in the two directions measured, while gradual increases in cable tension do not disturb the equilibrium of the body.
Portable Peening Capabilities in Maintenance, Repair, and Overhaul Environments using Ultrasonic Shot Peening
Authors:   Avion Solutions Inc., McClurg Kelly ,   SONATS, Brier Olivier , Buckner Randy , Chateau Frederic
Published: October 2024

STRESSONIC® Ultrasonic Shot Peening provides an economical shot peening solution to FAA Part 145 Repair Stations including Maintenance, Repair, and Overhaul facilities. This technology brings shot peening repairs to the shop floor, which eliminates the need to ship components to approved Conventional Shot Peening vendors, reducing shipping cost and turnaround time for a repair, as well as reducing the likelihood of damaged components due to shipping. Through a Small Business Innovative Research project with the U.S. Army, Avion and SONATS-Empowering Technologies qualified the use of the Ruggedized StressVoyager® on repairs for flight Critical Safety Items. Testing revealed that Ultrasonic Shot Peening induces a compressive residual stress comparable to Conventional Shot Peening methods used by Original Equipment Manufacturers, eliminating the concern of creating any stress concentration gradient when using this technology for repairs.
Readiness Integration Center (RIC)
Authors:   Bell Helicopter, Holveck Phil , Armijo Larry
Published: October 2024

The Naval Air System Command (NAVAIR) Naval Aviation Enterprise (NAE) Automated Logistics Environment (ALE) is applying Big Data Analytics and Cloud Computing Technology to support critical elements of Condition Based Maintenance Plus (CBM+) and Reliability Centered Maintenance (RCM) for NAVAIR platforms. The Comprehensive Automated Maintenance Environment -- Optimized (CAMEO) Readiness Integration Center (RIC) ALE capability focus is on the V-22 platform with an implementation strategy to apply Collaborative, Agile, Open Source, Big Data Analytics, and Cloud Technology to Collect, Connect, Warehouse, Analyze, and Act to improve platform readiness. The RIC is leveraging NAVAIR NAE ALE capability to Collect, Connect, and Warehouse critical Platform data. NAE collaboration with V-22, E2D, and Triton automated data extracts to support Platform analytic and decision support tool use and development. The RIC sponsors V-22 collaborative, agile, open source development using big data analytics and cloud technology to support the V-22 Readiness Steering Committee and Readiness Teams. The RIC actively supports Agile methodology for analytic and decision support tool development. The RIC use of Open Source tenants includes protections for intellectual property and licensing for use. The RIC development environment is consistent with Big Data and Cloud Technology computing and the RIC infrastructure and selected toolsets have completed proof of concept implementation in the Cloud. The focus of this paper is to describe a "day in the life of Big Data Analytics" from data recording and collection through RIC analytics and use by in service support engineering to effect corrective action.