bluuebunny/crossref_metadata_2025 huggingface dataset:
Model-Based Structural Integrity Assessment of Helicopter Fuselage During Harsh Landing
Authors:   Air Force Institute of Technology, Klimaszewski Slawomir ,   Politecnico di Milano, Giglio Marco , Kurdelski Marcin , Leski Andrzej , Zielinski Wojciech , Manes Andrea , Sbarufatti Claudio , Stefaniuk Michal , Vallone Giorgio
Published: October 2024

Nowadays the assessment of a harsh landing condition for helicopters is based on the pilot's judgment. This can lead to a misclassification of the landing condition, thus affecting the system safety or requiring unnecessary maintenance. The availability of a tool for the automatic assessment of the harshness of the landing condition will improve the efficiency of the current helicopter operations. This paper describes a preliminary step for the validation of a coupled multibody - finite element modelling environment, useful to estimate the most critical zones within the fuselage as well as the occurrence of plastic damage. Experimental harsh landing tests have been carried out on a retired Mil Mi-8 helicopter and 3D-scan measures of the helicopter geometry have been taken during helicopter tests. Repeated drops from increasing altitude have been performed, each time recording the 3D surface geometry at some critical locations, thus allowing the validation of the numerical model.
Development of a Magneto-Rheological Fluid-Based Trim Actuator with Active Tactile Cueing Capabilities
Authors:   Exonetics Design Inc., Julió Guifré ,   Bell Helicopter Textron Inc., Latham Geoffrey , Plante Jean-Sébastien
Published: October 2024

A magneto-rheological (MR) fluid-based trim actuator is being developed for rotorcraft applications. The device can provide active tactile cues to the pilot in the form of infinitely variable force gradients, stick shaking, and soft stops. Tactile cueing has proved to be an effective method of increasing situational awareness, especially during emergency situations and can reduce pilot workload for increased operational safety. The MR actuator uses magneto-rheological fluid to permit variable slippage between rotating clutch surfaces. With an MR fluid, the torque transfer between the clutch surfaces is dependent upon a user controlled magnetic field that is used to modulate output forces applied to control linkages. This paper discusses the design of the MR trim actuator and the control logic used to implement active tactile cueing. The latest experimental results on a single axis test bench are presented and discussed. The prototype work shows that MR technology can provide broad tactile cueing functionality with size and weight similar to conventional trim actuators found on light aircraft that lack tactile cueing functions.
The LIFT! Project - Modular, Electric Vertical Lift System
Authors:   The Boeing Company, Duffy Michael , Samaritano Tony
Published: October 2024

The LIFT! Project explored scaling of all-electric multi-rotor propulsion and methods of cooperation between multiple VTOL aircraft. Multi-rotor aircraft have become pervasive throughout the hobby industry, toy industry and research institutions due - in part - to very powerful, inexpensive inertial measurement devices and increased energy density of Li-Ion batteries driven by the mobile phone industry. This research demonstrates the viability of large multi-rotor systems up to two magnitudes of gross weight larger than a typical COTS hobby multi-rotor vehicle. Furthermore, this research demonstrates modularity and cooperation between large multi-rotor aircraft. In order to study large multi-rotor technologies, The Boeing Company decided to build a series of large scale multi-rotor vehicles ranging from 6 lbs gross weight to over 525 lbs gross weight using low cost COTS components. The LIFT! Project successfully demonstrated the effectiveness, modularity and scalability of electric multi-rotor technologies while identifying a useful load fraction (useful load/gross weight) of 0.64 for large, electric, unmanned multi-rotor aircraft. This research offers new insights on the feasibility of large electric VTOL aircraft, empirical trends, potential markets, and future research necessary for the commercial viability of electric VTOL aircraft.
Göttinger Monograph N: A Historic Document is Back
Authors:   German Aerospace Center - DLR, G. Berend
Published: October 2024

The Göttinger Monograph N was written 1945-1946 summarizing the German Development and Research on Rotat-ing Wing Aircraft from 1939 to 1945. It was written in large parts by Gerhard Jakobus Sissingh, who thereafter moved to England working for the Royal Aircraft Establishment in Farnborough before immigrating to the US in 1951. In Braunschweig (location of the "Deutsche Forschungsanstalt für Luftfahrt", founded in 1935, that was re-named to "Luftfahrtforschungsanstalt Hermann Göring” in 1938) as well as in Göttingen (location of the "Aerody-namische Versuchsanstalt", founded by Ludwig Prandtl in 1907) Monographs were written after the war in volumes A to R in Göttingen and many more in Braunschweig. These Monographs documented the progresses of the German aeronautical research in all aspects (since 1939). The developments were often far ahead of those of the Allies and the Monographs were ordered to make available this knowledge to the US, British and French research establish-ments and industry. The Göttinger Monograph N is the only one about rotating wing aircraft, written in German lan-guage, and the only one not translated immediately into English. Later, some chapters had been translated. Recently, this Göttinger Monograph N was translated into English in its entirety by the author and newly published by AIAA.
The Unsung Hero of Hurricane Katrina: The Helicopter
Authors:   US ARMY (Retired), Fardink Paul
Published: October 2024

This paper recounts the overwhelming success of the helicopter response during Hurricane Katrina. All branches of the United States Military and the National Guard flew those helicopters on nearly endless search and rescue missions, saving over 35,000 lives directly and tens of thousands more through air-lifted supplies and support. Surprisingly, the military development and utilization of the helicopter as a lifesaving machine once met great resistance; only the relentless, dogged determination of Coast Guard officers, William Kossler, Frank Erickson, and Stewart Graham, would turn the tide and launch a new chapter in aviation history, which came to demonstrable fruition with Hurricane Katrina. Of particular interest is the involvement of the oldest son of Dr. Igor Sikorsky, Sergei Sikorsky. During his WWII Coast Guard service, Sergei contributed greatly to helicopter capability by participating in the development and initial testing of the helicopter rescue hoist.
The First Chinese Tandem Helicopter Designed by Major General Chia-Jen Chu of RoCAF
Authors:   Sikorsky Aircraft Company, Virasak Jacques
Published: October 2024

In 1944, during the last days of WWII, Major General Chia-Jen Chu, general manager of China's First Aviation Factory, decided to begin exploring, designing and building helicopters after having witnessed the Sikorsky XR-4 helicopter flying over Kunming's sky in Yunnan Province of Southern China. On June 10, 1953 in Taichung, Taiwan, the first Chinese indigenous tandem configuration helicopter, nicknamed the Banana CJC-3A, took its first initial flight off the ground under the design leadership of Major General Chu. This tandem helicopter was a two-seat lightweight technology demonstrator. The event took place during the unprecedented military conflict era between the Chinese national and communist governments across the Taiwan Strait. The aircraft performance evaluation and design description of the Banana CJC-3A tandem helicopter will be presented. Because of the Chu Family's generosity in sharing Major General Chia-Jen Chu's personal technical notebook with the author, the public can finally rediscover the CJC-3A aircraft sixty three years later after its first flight.
Health Monitoring Survey of Bell 412EP Transmissions
Authors:   Bell Helicopter, Tucker Brian ,   NASA Glenn Research Center, Dempsey Paula
Published: October 2024

Health and usage monitoring systems (HUMS) use vibration-based Condition Indicators (CI) to assess the health of helicopter powertrain components. A fault is detected when a CI exceeds its threshold value. The effectiveness of fault detection can be judged on the basis of assessing the condition of actual components from fleet aircraft. The Bell 412 HUMS-equipped helicopter is chosen for such an evaluation. A sample of 20 aircraft included 12 aircraft with confirmed transmission and gearbox faults (detected by CIs) and eight aircraft with no known faults. The associated CI data is classified into "healthy" and "faulted" populations based on actual condition and these populations are compared against their CI thresholds to quantify the probability of false alarm and the probability of missed detection. Receiver Operator Characteristic analysis is used to optimize thresholds. Based on the results of the analysis, shortcomings in the classification method are identified for slow-moving CI trends. Recommendations for improving classification using time-dependent receiver-operator characteristic methods are put forth. Finally, lessons learned regarding OEM-operator communication are presented.
Measurement of Vibration Transfer Functions to Inform Machine Learning Based HUMS Diagnostics
Authors:   US Army, Wade Daniel ,   The Boeing Company, Ngo Hieu ,   US Army, Love Frances , Partain Jeremy , Wilson Andrew , Statham Matthew , Shanthakumaran Perumal
Published: October 2024

The US Army has improved a method for accelerating the maturity of vibration-based mechanical diagnostics, by measuring the Frequency Response Functions (FRFs) between potential failure locations and sensor locations within epicyclic gearboxes, and by building Condition Indicators (CIs) using these FRFs. The previous FRF methodology has been expanded to include frequencies up to 100 kHz, using the piezo-exciters, aircraft-installed Health and Usage Monitoring Systems (HUMS), and custom data acquisition hardware described herein. Previous CI development methodology has been improved by filtering captured vibration data with the FRFs. Using a recent process for generating diagnostic algorithms using machine learning, these FRF-based CIs outperform conventional CIs, and meet Aeronautical Design Standard 79D diagnostic classification criteria for use on board aircraft.
Modeling the Effect of Yawed Flow on Dynamic Stall with Secondary Lift Peak - Experimental Correlation
Authors:   Washington University in St. Louis, Modarres Ramin , Peters David
Published: October 2024

For a helicopter in forward flight, the rotor blade is unswept at only two locations, 90° and 270°; and the blade section undergoes wide variation in sweep angle during each revolution. Furthermore, as advance ratio (i.e. the forward flight speed) increases, the sweep angle becomes large enough to create significant effects on the aerodynamic forces and, consequently, on the dynamic stall characteristics. In linear aerodynamic analysis, it is assumed that the radial component of the velocity does not affect the sectional loads; and the airloads are calculated considering only the velocities in a plane containing the airfoil chord. However, experimental research shows that, although this assumption is quite acceptable in the low angle-ofattack region, in the high angle-of-attack, stall region, a much higher lift coefficient is obtained for larger sweep angles. Therefore, conventional, unswept theories may not be sufficient for rotor aerodynamic analysis in a three-dimensional flow field. The purpose of this study is to add the effect of yawed flow to the dynamic stall model of Ref. [1].
Finite State Coaxial Rotor Inflow Model Improvements via System Identification
Authors:   Georgia Institute of Technology, Kong Yong-Boon ,   Advanced Rotorcraft Technology Inc., Kim Jeewoong , Prasad J.V.R. , Sankar Lakshmi
Published: October 2024

For real-time rotor inflow calculations, the finite state inflow models are commonly used due to the fact that they are more computationally efficient compared to CFD models. For coaxial rotor configuration, the finite state Active-Receiving Rotor Inflow Model (ARRIM) developed from potential flow theory, was shown to correctly predict power variations with rotor thrust in hover. However, potential flow theory cannot capture the complex aerodynamic interactions between upper and lower rotors in forward flight. In order to address this problem, a system identification approach is used to quantify both rotors' mutual interference effects using results from GT-Hybrid, a high-fidelity free-wake model. There are significant differences in wake skew angles predicted by GT-Hybrid and those calculated using momentum theory. Corrections needed in ARRIM influence coefficient matrix (L-matrix) in capturing wake distortions due to rotor-to-rotor flow interactions are identified. The identified results show a linear correlation between the required corrections to the wake skew angle and advance ratio. ARRIM with the identified wake skew angle and L-matrix corrections is implemented in FLIGHTLAB R and is seen to improve its inflow predictions.
Model-Enhanced Analysis of Flight Data for Helicopter Flight Operations Quality Assurance
Authors:   Georgia Institute of Technology, Gavrilovski Alek , Collins Kyle , Mavris Dimitri
Published: October 2024

Helicopter Flight Operations Quality Assurance (HFOQA) systems promise safety improvements in flight operations through the use of on-board data from regular flights. HFOQA systems can provide data pertaining to many types of accidents where human factors have been implicated because they track the manner in which the vehicles are operated. For helicopters, most implementations of such systems on helicopters rely on experts to determine pre-set limits on combinations of flight parameters. These limits are also known as "safety events". A common practical problem that arises in HFOQA systems is the need to have sufficient knowledge of a condition before events can be defined and used in a proactive manner. There has been recent interest in using alternative approaches to detecting faults and unsafe events in aviation and to solve this inherent limitation of HFOQA. In this work, a model-based approach is taken in an effort to extend the capabilities of traditional HFOQA analysis, particularly in terms of definition and detection of monitored conditions. For localized conditions, the use of simple models in place of traditional safety events is investigated and demonstrated. The detection based on the model evaluation shows a good correspondence to the flight condition it was designed to capture, and at the same time incurring a minimal amount of additional computation. The model-based boundaries typically account for changes in vehicle parameters and operating conditions, whereas traditional safety events have to be modified through an iterative process. For a more general approach, a dynamic model was considered. By evaluating the vehicle's response to a set of control inputs spanning a range about the trim state, it was possible to determine the boundaries of safe input. The inputs falling outside this boundary were also evaluated for the risk associated with them based on the time required to reach a critical state. In both cases, the results offer improvements over the current state-of-practice, and can be deployed in a data-monitoring system directly or following intermediate post-processing steps.
Improvements in the Rotorcraft Fuel Economy and Environmental Impact through Multiple-Landing Mission Strategy
Authors:   Chalmers University of Technology, Ali Fakhre
Published: October 2024

This paper presents an integrated rotorcraft multidisciplinary simulation framework, deployed for the comprehensive assessment of combined rotorcraft–powerplant systems performance at mission level. The proposed methodology comprises a wide-range of individual modelling theories applicable to rotorcraft performance and flight dynamics, gas turbine engine performance, and estimation of gaseous emissions (i.e. nitrogen oxides, NOx). The overall methodology has been deployed to conduct a comprehensive mission level feasibility study for a twin-engine light (TEL) rotorcraft, modeled after the Airbus Helicopters Bo105 configuration operating on a multiple-landing flying (MLF) mission approach compared to rotorcraft employing a conventional flying (CF) mission approach. The results of the analyses allow mission level assessment of the both aforementioned approaches for a wide-range of useful payload (UPL) values, mission range as well as mission level outputs (e.g. fuel burn, mission time, and gaseous emissions i.e. NOx). Furthermore, evaluation of engine cycle parameters (i.e. overall pressure ratio (OPR), turbine entry temperature (TET), and engine mass flow) are also carried out with respect to both approaches. The results acquired through the parametric analyses suggest that the MLF mission approach has the potential to significantly reduce rotorcraft mission fuel burn as well as gaseous emission (i.e. NOx). It has also been established through the acquired results that rotorcraft employing the MLF mission approach requires lower engine operating power throughout the entire mission duration, and therefore operates on a relatively lower engine OPR, combustor entry temperature, mass flow, rotational speed, and the TET compared to rotorcraft employing CF mission approach. It is emphasized that such operation of the engine can potentially improve the rate at which the engine components (i.e. compressor, combustor, and turbine) may deteriorate, thus the MLF mission approach can potentially provide further benefit in terms of engine maintenance and overall engine life. Finally it has been emphasised that the mission total range is a critical parameter in determining the level of benefit that can be attained from the employment of MLF mission approach.
Helicopter Operation at Fukushima Nuclear Disaster
Authors:   Utah State University, Sagane Hajime
Published: October 2024

At 14:46 JST on March 11, 2011, a massive earthquake hit the northeastern coast of Japan. The magnitude of the earthquake was 9.0 (Mw). It was the most powerful earthquake ever recorded in Japanese history. The earthquake triggered a deadly tsunami and swept away thousands of houses and lives. At the same time, the Fukushima Dai-ichi (No1) nuclear power plant was struck by the tsunami and the reactor took serious damage. This caused reactors to have a core meltdown and explode. There had been a radiation leak in the nuclear power plant. On March 15, the Japanese government set the restricted area within 30 km from the Fukushima nuclear power plant due to the radiation leakage. On March 17, two Japan Self Defense Force (JSDF) CH-47J helicopters dropped water to cool the failing reactor. The mission was successful, and the radiation around the reactor was gradually decreased, allowing for further operations. On April 14, one month after the disaster, the Japanese government requested the dispatchment of the Japan Coast Guard (JCG) for a search and rescue mission within the restricted area. This was the first search and rescue mission held at sea within a radioactive-contaminated environment in Japan, for which nine patrol boats, two airplanes, and three helicopters were sent for the mission. This paper describes the general outline about the cooling, thermo-monitoring, and the search and rescue missions as well as the equipment used, maximum permissible dose of radiation, and the mission environment. Then it compares this data with the helicopter operations during the Chernobyl accident. The purpose of this paper is to expand readers' knowledge about helicopter operations during nuclear disasters with the hopes for it to be a useful material for future missions. The story of this paper is based on the author's experience as a dispatched Japanese Coast Guard helicopter pilot.
The AgustaWestland AW609: Commercial Tiltrotor Operations in the Civil Aviation Environment
Authors:   AgustaWestland Philadlephia Corp, Wells Dan ,   AgustaWestland Philadelphia Corp, Dubeck Scott , Barbour Don
Published: October 2024

The AgustaWestland AW609 is a nine-passenger civil tiltrotor aircraft capable of both vertical takeoff and landing and cruising at 25,000 feet above sea level at 250+ knots true airspeed. The AW609 will be the first tiltrotor aircraft to be FAA type certificated for use as a passenger and emergency medical aircraft. This paper will outline how the AW609 will integrate into the existing aviation infrastructure including a description of the applicable airworthiness and operational standards for the world's first commercial tiltrotor. It will discuss how its point to point ability has the potential to reduce the cost, time and complexity of air travel while reducing air traffic density and how that same ability will increase aeromedical efficiency in both the air ambulance and organ transfer fields. It will also address existing airspace structure improvements that would allow the user community to utilize tiltrotor technology to maximum advantage.
MQ-8 Fire Scout Icing Solution Challenges
Authors:   PMA 266 - NAWCAD, Ernst Robert ,   Wyle Aerospace Group, Sehgal Ajay
Published: October 2024

The MQ-8 (Fire Scout) is a vertical takeoff and landing unmanned aircraft system (UAS) operated by the U S Navy (USN) as an Intelligence, Search and Reconnaissance (ISR) platform operating in both sea and land based environments. In its current configuration, the standard operating procedure is for the air vehicle (AV) to avoid operations in known and forecasted icing conditions. The Navy and Marine Corps Multi-Mission Tactical Unmanned Air Systems Program (PMA-266) has launched a trade study to develop a system that will notify the operator well in advance of flying into an impending icing environment, thereby, reducing the probability of loss of AV. This paper discusses how the MQ-8 UAS current concept of operations (CONOPS) is addressing in-flight icing challenges along with details of the study undertaken to develop an enhanced icing solutions roadmap for improved mission effectiveness while maintaining safe operations.
Mission Ready - Completing 505 Jet Ranger X Optional Equipment Kits Development in Time for 1st Deliveries
Authors:   Bell Helicopter Textron, Reilly Thomas , Ward Nicholas
Published: October 2024

Developing a new aircraft is an intricate ballet of defining key performance parameters and integrating the many systems and subsystems to meet product objective. Development activity becomes even more complex when optional equipment kits are added into the development cycle. Almost by definition, anything defined as "optional" does not receive the same priority as the basic aircraft. Integrating, testing and certifying the kits and their maintenance requirements "concurrently" with the aircraft may be hazardous to the timeline of the basic ship certification schedule. Nevertheless, optional equipment kits are essential for a successful new product launch since they add the final capabilities to each customer's specific flight operations. And it is not just kit designs and hardware, but the whole package must be complete, including: life-limit definitions and scheduled maintenance, flight manual supplements, applicable training, and spare parts readiness. The overlapping and sometimes conflicting demands between the aircraft and its optional equipment must be carefully planned, coordinated, managed and executed to achieve the mission: to have optional equipment kits certified in time for first customer delivery.
Load Distribution and Mesh Stiffness Analysis of an Internal-External Bevel Gear Pair in a Pericyclic Drive
Authors:   The Pennsylvania State University, Mathur Tanmay ,   The University of Tennessee Knoxville, DeSmidt Hans , Smith Edward , Bill Robert
Published: October 2024

The pericyclic drive is characterized by very high single stage gear ratios (∼50:1). This is enabled by nutational motion kinematics, load sharing over many teeth (∼10% of teeth), and high power density capabilities. A novel methodology for loaded tooth contact and mesh stiffness analysis of an internal - external straight bevel gear pair, with a difference of 1 or 2 teeth, meshing at small shaft angles (2° - 5°) in this non-conventional transmission is described. A computationally fast algorithm to generate modified external bevel gear with profile and lead crowning was developed to localize bearing contact. Thereafter, an efficient nearest neighbor search algorithm was used to find contact points. Load distribution was calculated by minimizing the total elastic potential energy during meshing. Finite Strip Method (FSM) was applied to accurately calculate tooth deflection for non-standard gears in point contact. Further, maximum bending stress has been formulated as a useful tool for designers by curve fitting the results from several Finite Element (FE) simulations. Results from FE analysis are also used to validate contact stress and gear tooth deflection solutions. The results also show that mesh stiffness variation is small (10 - 15%). Therefore, lower mesh excitation and gear noise can be expected in a Pericyclic drive.
Damage Behaviour of Rotorcraft End Plate under High Velocity Bird Impact
Authors:   Rotary Wing - Hindustan Aeronautics Limited, Kumar R. , Thenarasu D. , Ravindranath R. , Chalwade D.B.
Published: October 2024

The finite element model is developed for simulating the bird strike test of rotorcraft End plate using the bird numerical modeling techniques. The main design goal is the satisfactory impact resistance of the composite structures in the case of bird strike. The design concept is based on the absorption of the major portion of the bird kinetic energy by the composite skins, in order to protect the inner honeycomb core from damage, thus preserving the End plate functionality for safe landing. To this purpose, the End plate skin is fabricated from composite layers, which unfold under the impact load and increase the energy absorption capability. The numerical modelling of bird strike using the Lagrangian approach and Smooth Particle Hydrodynamics formulation and the critical design parameters are considered in carrying out the analysis. A numerical model of this problem has been developed with an explicit finite element code Autodyn. Analysis is carried out for the developed model using the test parameters. Numerical results by means of bird modelling approaches are substantiated with experimental test results. The results obtained from the analysis and test shows close conformity implying their appropriateness in the simulation of bird strike.
Analysis of Human Guidance and Perceptual Behavior in Navigation of Unknown Environments
Authors:   University of Minnesota, Verma Abhishek , Mettler Berenice
Published: October 2024

The human brain is able to generate guidance strategies in unknown environments and improve performance over multiple trials. Such capabilities are challenging to implement in autonomous systems. This research uses a computational framework based on a spatial value function and invariants, described as interaction patterns, in the function to investigate human planning and learning in unknown environments. A simulation system was used for human guidance experiments in a simulated obstacle field unknown to the subjects before the experiments. The system recorded vehicle trajectory, control inputs, and human gaze over multiple trials, between specified start and goal locations. Human guidance policy is evaluated in comparison with an optimal control baseline, formulated using interaction patterns in a Dubins optimal solution. The subjects' control characteristics explain why exploratory behavior varies from one individual to the next. The authors utilize gaze spatial density and an information gain model, employing gaze location data, to investigate the visual cues that support guidance and navigation.
Cockpit Alarm Detection and Identification Algorithm for Helicopters
Authors:   Purdue University, Shin Sanghyun , Ding Yiqing , Hwang Inseok
Published: October 2024

In recent years, the National Transportation Safety Board (NTSB) has emphasized the importance of analyzing flight data such as cockpit voice recordings as an effective method to improve the safety of helicopter operations. Cockpit voice recordings contain the sounds of engines, crew conversations, alarms, switch activations, and others within a cockpit. Thus, analyzing cockpit voice recordings can contribute to identifying the causes of an accident or incident. Among various types of the sounds in cockpit voice recordings, this paper focuses on cockpit alarm sounds as an object of analysis. Identifying the cockpit alarm sound which is activated when a helicopter enters an atypical state of flying could help identify the state and timing of the incident. Nonetheless, alarm sound analysis presents challenges due to the corruption of the alarm sounds by various noises from the engine and wind. In order to assist in resolving such a problem, this paper proposes an alarm sound analysis algorithm as a way to identify types of alarm sounds and detect the occurrence times of an abnormal flight. For this purpose, the algorithm finds the highest correlation with the Short Time Fourier Transform (STFT) and the Cumulative Sum Control Chart (CUSUM) using a database of the characteristic features of the alarm sounds. The proposed algorithm is successfully applied to a set of simulated audio data which was generated by the X-plane flight simulator in order to demonstrate its desired performance and utility in enhancing helicopter safety.
Future Vertical Lift Airworthiness Certification - Should it be based on A Civil Aviation Functional Safety Certification Standard?
Authors:   Georgia Institute of Technology, Schrage Daniel ,   University of Alabama, Arterburn David
Published: October 2024

As integration of software and hardware plays a bigger role in the design of complex systems and system of systems the terms Cyber Physical System (CPS) and Cyber Physical Vehicle System (CPVS) are used to describe this software enabled control (SEC) paradigm shift. A CPS is "the next generation of system that requires tight integration of computing, communication, and control technologies to achieve stability, performance, reliability, robustness, and efficiency in dealing with physical systems of many application domains"1. Pertaining to vehicle systems, a CPVS, ranging from automobile to aircraft and marine craft, is composed of tightly-coupled locomotion, computational and communication components. This SEC tight coupling has a major impact on the development and certification for future aircraft systems, such as Future Vehicle Lift (FVL). In the civil aircraft sector this tight SEC coupling is being addressed by new or substantially updated guidelines for civil aircraft and systems development, such as DO 297 and ARP 4754A. The tight interaction with ARP 4761 and dependence between certification and safety assessment at different levels, e.g. functional and item, are promoted through the use of supporting Development Assurance Levels (DALs). While in the military aircraft sector some attempts have been made to keep pace with this transition to CPVS tight coupling, the question is will this be adequate or relevant for FVL∼ Following an introduction, this paper will start with a review of functional safety certification standards and their evolution into the civil aircraft sector. This will be followed by a review of military aircraft airworthiness qualification standards. Finally, whether they are sufficient for future aircraft development, such as FVL, will be questioned.
Effort sponsored by the US Government under Other Transaction number W15QKN-10-9-0003 between Vertical Lift Consortium, Inc. and the Government. The US Government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright notation thereon.
The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the US Government.
Probabilistic Rotorcraft Usage Spectrum Development Using Recognized Maneuvers
Authors:   Technical Data Analysis Inc., Moon Suresh ,   Structures Division - NAVAIR, Phan Nam ,   Technical Data Analysis Inc., Stull Mike , Leonard Mark
Published: October 2024

Presently the fatigue lives of H-53E dynamic components and airframe are based on a usage spectrum developed using pilot surveys. In order to better define the usage spectrum and to extend component and airframe fatigue life, the Integrated Mechanical Diagnostic (IMD/HUM) System is being installed on the U.S. Navy H-53 rotorcraft. So far, 157 aircraft are equipped with IMD systems and 77,680 flight hours of good data have been recorded. This paper analyzes the HUMS data using regime recognition. The wide variations in regime utilizations from rotorcraft to rotorcraft were characterized using the Normal and the Weibull probability distributions. The unique distributions parameters' mean and standard deviation, Weibull slope and Weibull characteristic values were determined for 46 regimes of the H-53E usage spectrum. The probabilistic fleet usage spectrum of various severities, 50th, 93.3th, 97.7th, and 99.9th percentiles were created using distribution parameters and damaging status of the regimes. The approach helped to create a mean plus 2 sigma spectrum and a Fleet Composite Worst Case Usage Spectrum (FCWCS) to fulfill U.S. Army ADS-79E requirements. The impact of usage spectrum severities on rotorcraft component fatigue life and reliability are assessed. The individual components Fatigue Life Expended (FLEs) were computed to determine the feasibility of Condition Based Maintenance (CBM).
Comparative Study of Finite Element Analysis and Geometrically Exact Beam Analysis of a Composite Helicopter Blade
Authors:   METU, Atac Meryem , Kayran Altan
Published: October 2024

In this paper, comparative study of the finite element analysis and geometrically exact beam analysis of a composite helicopter blade is performed. The objective of this study is to investigate the applicability of the geometrically exact beam analysis of the composite helicopter blade in predicting the structural response of the composite blade. To evaluate the structural response determined by the geometrically exact beam analysis of the composite blade, detailed finite element model of the blade is prepared and the structural response of two methods are compared for different static and transient load cases and dynamic analysis. Geometrically exact beam analysis utilizes variational asymptotic beam section analysis for the calculation of sectional stiffness and mass matrices, and general deformation of the blade for the static and transient load cases can be determined with high accuracy. Three dimensional stresses in the selected blade sections can also be determined via the stress recovery feature of the variational asymptotic beam section method. It is shown that the neutral axis, shear center, still air natural frequency, static and transient displacement and static stress analysis results of the cross-sectional analysis tools, VABS and GEBT together, match perfectly with the FEM results for the rectangular section and airfoil section blade models studied. It is considered that especially for the structural design of the airfoil sections of the blade, which requires many re-analyses due to frequent design changes in the detailed design stage, geometrically exact beam analysis can replace finite element method which requires longer modelling times to reflect the design changes.
Isogeometric Analysis Based Finite Element Approach for Ductile Failure Prediction of the Second Sandia Fracture Challenge Problem
Authors:   Global Engineering and Materials Inc., Fang Eugene ,   Carnegie Mellon University, Lai Yicong ,   Naval Air Warfare Center (PAX), Phan Nam , Lua Jim , Zhang Yongjie
Published: October 2024

It is a great challenge to perform an accurate and efficient ductile failure prediction of an aerospace structural component with multiple stress concentrators resulting from geometric discontinuities, fillers, or holes. The fidelity of a finite element analysis depends strongly on the quality of mesh construction for accurate representation of the component geometry. In order to create a finite element model from CAD geometry directly without data conversion, an isogeometric analysis toolkit for Abaqus (IGAFA) has been developed by integrating existing computer aided design (CAD) software with a customized Abaqus toolkit using a volumetric T-spline based IGA element for Abaqus. Under this study, we have augmented the existing IGAFA toolkit for Abaqus by implementing the Hill's plasticity model to capture the competition of tensile and shear driven ductile failure mechanisms. The capability of using IGAFA for ductile failure prediction is demonstrated via its application to the failure prediction of the recent second Sandia Fracture Challenge (SFC2).
Results Of A Parametric Design Study To Adapt The Structural Properties And Strain Distribution Of Active Twist Blades
Authors:   German Aerospace Center (DLR), Kalow Steffen , Opitz Steffen , Riemenschneider Johannes , Hoffmann Frauke
Published: October 2024

Rotor Blades, especially active twist blades, have been investigated by DLR (German Aerospace Center) for many years and the feasibility of this technology was shown in several projects. (1-8) However, many relevant features must be taken into account within the design process. The most challenging aspect is the proper tuning of the structure to integrate the fragile actuators, because they have to sustain a variety of loads, while still providing the expected performance. Further different constraints on bending and torsional stiffness or axes positions of the rotor blade exist. At DLR a tool called SaMaRA (Structural Modelling and Rotor Analysis) was developed. It's a parametric finite element model to meet these partially conflicting requirements as part of a structural optimization framework. The proposed paper provides an overview of the adaption of structural properties and shows representative results for active twist blades.
US Army Composite Repair Standardization
Authors:   US Army, Stone David , Marshall Kristina
Published: October 2024

This paper explores the need for the US Army to standardize repair of composite aircraft structure. The paper includes a discussion of the needs for standardization as well as historical attempts and current plans. Repair materials, processes, equipment, tooling, facilities and contamination sources that are unique to the Army operating environmental are described in detail. A brief history of advanced composite repair in the Army as well as current standardization efforts will be described in this paper. By standardizing advanced composite repair materials, processes, tools, and training the Army is ultimately easing the burden on the maintainer while maintaining airworthiness.
Designing the Bell 525 Pylon Bipod Mount Test Fixture
Authors:   Bell Helicopter - Textron India Private Limited, Mukherjee Siddhartha ,   Bell Helicopter Textron Inc, Barbarin Alejandro
Published: October 2024

The behavior of dynamic rotorcraft components is often governed by the coupled structural response of mating parts. Component level testing of such parts must account for the full rotorcraft structural response on the test bed. The main rotor and transmission of the Bell 525 are supported by Pylon Bipod Mounts that accept the loads from the rotor and transmission system, and transfer them to the fuselage roof beams. The Bipod Mounts must accommodate dynamic loads and deflections of the full system. This paper exercises principles of statics and Finite Element Simulation to put forward a methodology for the subsystem structural test approach of the Bell 525 Pylon Bipod Mount. This structural test approach enables near exact replication of the Bipod Mount fatigue performance anticipated for the full structure in flight conditions.
Overview of S-97 RAIDER Scale Model Tests
Authors:   Sikorsky Aircraft, Lorber Peter ,   United Technologies Research Center, Matalanis Claude , Law Gary , O'Neill John , Bowles Patrick
Published: October 2024

A sequence of scale model wind tunnel tests have been conducted to help design the S-97 RAIDER™ aircraft and better understand the aerodynamics of X2 Technology™ rotorcraft incorporating coaxial rigid lift offset rotors, low drag airframes, and a pusher propeller. The tests provided inputs to aerodynamics and flight dynamics simulations, validation data for CFD, and aerodynamic loads for design. The first test obtained high Reynolds number aerodynamic coefficients for airfoil families planned for the main rotor blades. A particular focus was on forward and reverse flow data for a thick single ended airfoil and a double-ended airfoil. A 1/10 scale unpowered airframe was then tested in the UTRC Pilot Wind Tunnel to obtain basic aerodynamic loads, plus flow interaction diagnostics on the fuselage, tail, and at the propeller plane. A hub and sail fairing drag test was conducted to obtain quantitative drag measurements on multiple fairing geometries, and to get insight into the effect of rotation, gaps, and the presence of blade stubs. A diagnostic test using a 1/5 scale model of the X2 Technology™ demonstrator investigated the aerodynamic interaction between the airframe and the propeller, and helped better understand the flight test data. The final tests were of a Mach-scale powered main rotor and fuselage in the National Full Scale Aerodynamics Facility 40x80' test section. The two entries included airframe-only, airframe plus upper rotor, and airframe plus coaxial rotor. The powered model results discussed in this paper will concentrate on the interactions between the main rotor, fuselage, and empennage.
Certification Flight Testing of the Bell 412EPI Increased Gross Weight Helicopter
Authors:   Bell Helicopter Textron, Schillings John , Lindauer Pat , Grogran Jason , Runge Hans , Newman Jeff
Published: October 2024

This paper presents a summary of the certification flight test program of the new Bell 412EPI Increased Gross Weight helicopter. Flight testing is described which supports an increase in the maximum gross weight of the Bell 412EPI from 11,900 lb to 12,200 lb. Measured data for a variety of flight conditions are presented, including CAT A rejected and continued takeoffs, height-velocity landings, simulated engine failures at high speed, static and dynamic stability, and ground resonance. Hover performance, low-speed controllability, and external loads testing are also discussed. A new CAT A backup procedure is developed that is applicable to both ground level and elevated heliports. This new procedure results in increased performance and reduced helipad size requirements. CAT A capability increased by 650 lb gross weight at 2,000 ft altitude, and increased altitude capability by 5,000 ft at 9,150 lb gross weight.
Bell Model 505 Fatigue Test Loads Derivation using Flight Test Data Reduction and Convex Envelopes
Authors:   Bell Helicopter Textron Canada Limited, Lapalme Maxime , Biron Guillaume , Ouellet Marc
Published: October 2024

In this paper, a methodology to derive loads to apply to a full scale fatigue test from flight test data is presented. Bell model 505 tailboom is used to illustrate the methodology. First, the tailboom instrumentation for flight testing is described. A complete Load Level Survey is performed to gather the data required for the fatigue test. Then, the whole flight test data (18,000,000 data points) is reduced to a critical convex envelope (roughly 5,000 data points). To further reduce the loads data set to a manageable number for a fatigue test, a Finite Element model is built to obtain relations between applied loads and stresses at specific locations on the tailboom. A total number of 6 load cases are finally identified and a proper loading sequence is defined according to various considerations. Finally, the whole methodology and limitations are discussed.
Autonomous Rotorcraft Flight Control with Multi-Level Pilot Interaction in Hover and Forward Flight
Authors:   US Army, Takahashi Marc ,   San Jose State University, Goerzen Chad , Whalley Matthew , Mansur Hossein , Minor Joseph , Morford Zachariah , Ott Carl , Schulein Greg
Published: October 2024

This paper describes the development and flight testing of an autonomous flight control system that allows for different levels of pilot interaction in both hover and forward flight. Three modes of operations are described, fully coupled autonomy, additive control, and piloted decoupled attitude-command. These modes are demonstrated on the Rotorcraft Aircrew Systems Concepts Airborne Laboratory (RASCAL) JUH-60A Black Hawk integrated with Obstacle Field Navigation (OFN) and Safe Landing Area Determination (SLAD) algorithms that both use a line scanning LADAR as their primary sensor. The paper will describe the control system, its performance, and demonstrate how it was used to transition into these modes while flying mission scenarios through mountainous terrain at speeds from hover to 100 kts.
Numerical Simulation of Multiple Interacting Wind Turbines on a Complex Terrain
Authors:   Iowa State University, Murali Avinaash , Rajagopalan R.
Published: October 2024

Modern wind farms are subjected to significant aerodynamic interference due to unsteady wakes of individual turbines as well as the complex terrains on which they are erected. The present study uses a new mixed basis formulation of the Navier-Stokes equations for accurate numerical simulation of convection-dominated flows on a complex terrain. The turbines are modeled using a distribution of momentum sources and the incompressible, turbulent flow-field is solved using the Reynolds Averaged Navier-Stokes (RANS) equations. A finite-volume procedure is used on body fitted grids and the SIMPLER algorithm is used to obtain the flow-field. Three different turbulence models including the standard, RNG, and realizable K - ε are implemented and compared. Results validating the ability of the numerical procedure to simulate flows over complex terrains and wind turbines are presented. Applications providing insights into the performance and loading on wind turbines subjected to turbine-terrain interference are studied. The evolution and interaction of the turbine wake with the complex terrain are also analyzed.
A Study of Individual Pitch Control of a Horizontal Axis Wind Turbine in Atmospheric Boundary Layer
Authors:   Japan Aerospace Exploration Agency (JAXA), Tanabe Yasutada ,   Tokyo University of Science, Oe Harutaka , Aoyama Takashi , Sugiura Masahiko , Yamamoto Makoto
Published: October 2024

An Individual Pitch Control (IPC) system to reduce the yawing and tilting moments on the hub of Horizontal Axis Wind Turbines (HAWTs) in Atmospheric Boundary Layer (ABL) is constructed and a trim routine is numerically simulated to check the effectiveness of the system. With 1/rev cyclic pitch control, it is found that for a three-bladed turbine, the averages can be trimmed to nearly zero while the 3/rev fluctuations cannot be effectively reduced . However, for a two-bladed turbine, the averaged moments can be reduced to nearly zero, and furthermore, the load fluctuations on rotor hub can also be significantly reduced. For both type of HAWTs, the oscillations of flapwise bending moment on the blade root can be remarkably reduced when IPC is applied.