Proceedings of the Vertical Flight Society 76th Annual Forum最新文献

{"title":"Appropriate Calculation of Risk per Flight Hour for Rotorcraft Safety Risk Management","authors":"J. Hewitt, D. Loan","doi":"10.4050/f-0076-2020-16347","DOIUrl":"https://doi.org/10.4050/f-0076-2020-16347","url":null,"abstract":"\u0000 Quantitative Risk Assessment has become essential in rotorcraft safety risk management. Measures of risk include Cumulative Fleet Risk (also called Risk Factor), Risk per Flight, and Risk per Flight Hour. Each measure applies to a different situation and can produce the same or different predictions of future risk. Risk for a large fleet of aircraft might be accurately predicted by Cumulative Fleet Risk, whereas Risk per Flight or Risk per Flight Hour might be best for a small fleet of rotorcraft, a flight test program, or a fleet with low flight hours. Calculating risk per flight hour seems as simple as dividing the number of previous occurrences by the flight hours for the total fleet, but this is appropriate only in the case of random distribution. Most failures that lead to hazards are not random because the failure mechanism has a specific cause. A more appropriate method is to develop the future event forecast using Quantitative Risk Assessment, then divide that by the future fleet hours. The simple division process requires only two numbers and can be completed quickly, but with a possibly inappropriate or misleading result for anything but a random distribution. The approach presented here results in a risk prediction that is appropriate for hazard rates that are increasing, decreasing, or constant, and for non-random distributions, which could prevent misleading or unconservative risk management decisions.\u0000","PeriodicalId":293921,"journal":{"name":"Proceedings of the Vertical Flight Society 76th Annual Forum","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125453726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Development and Assessment of Flight Lead Cue for Real-time Guidance and Pilot Workload Reduction in Rotorcraft Shipboard Recovery","authors":"Vinodhini Comandur, K. Feigh, J. Prasad, R. Walters","doi":"10.4050/f-0076-2020-16398","DOIUrl":"https://doi.org/10.4050/f-0076-2020-16398","url":null,"abstract":"\u0000 Helicopter shipboard launch and recovery are some of the most challenging operations to date, owing to the pilot workload associated with the tasks. A variety of environmental conditions such as random deck motion, heavy sea states and unsteady aerodynamic interactions can be attributed to the same. This paper highlights the development and assessment of a visual flight lead cue for real-time guidance and pilot workload reduction. For a chosen approach-turnland maneuver, the pilot workload is assessed using data from pilot-in-the-loop (PIL) flight simulations. Quantitative metrics based on Time-Frequency Representation (TFR) are used to evaluate pilot workload and the analysis of workload in the presence and absence of the cue is presented. Furthermore, the deviations from the desired path are studied using root-mean-square error (RMSE) for the cue on/off cases. The relation between pilot workload and path following is analyzed to determine the efficacy of the cue provided.\u0000","PeriodicalId":293921,"journal":{"name":"Proceedings of the Vertical Flight Society 76th Annual Forum","volume":"76 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124088452","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparing RotCFD Predictions of the Multirotor Test Bed with Experimental Results","authors":"Sarah Conley, Kristen Kallstrom, Witold J. F. Koning, Ethan A. Romander, C. Russell","doi":"10.4050/f-0076-2020-16485","DOIUrl":"https://doi.org/10.4050/f-0076-2020-16485","url":null,"abstract":"\u0000 The Multirotor Test Bed (MTB) is a new capability for testing a wide array of advanced vertical take-off and landing (VTOL) rotor configurations, with a primary focus on testing in the U.S. Army 7- by 10-Foot Wind Tunnel at NASA Ames Research Center. The MTB was designed to allow adjustment of the vertical, lateral, and longitudinal placement of each rotor, as well as allow tilt adjustment of each rotor and pitch adjustment of the whole assembly. Each rotor can tilt forward 90 deg and backwards 5 deg. In addition, the entire MTB can tilt forward 20 deg and backwards 10 deg. This flexibility allows the system to be tested in many different configurations. There is a six-axis load cell under each rotor assembly, to measure both the steady and dynamic loads produced by each rotor. The wind tunnel scales can measure loads on the full assembly. The overall goal of the MTB project is to help gain a better understanding of the performance, control, interactional aerodynamics, and acoustics of multirotor systems. A hybrid CFD tool called RotCFD (Rotorcraft Computational Fluid Dynamics) was used to simulate the MTB in several testing configurations. This paper explains the method of running the RotCFD simulations and explores the results from the simulations. The objective of this paper is to compare the RotCFD simulation results with the MTB wind tunnel test data, seeking to further validate RotCFD for multirotor systems and assess the influence of aerodynamic interactions on individual rotor performance.\u0000","PeriodicalId":293921,"journal":{"name":"Proceedings of the Vertical Flight Society 76th Annual Forum","volume":"90 3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129188558","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Contract Based Approach to Collision Avoidance for UAVs","authors":"T. Alimbayev, Nicholas J. Moy, Kaushik Nallan, Sandipan Mishra, A. Julius","doi":"10.4050/f-0076-2020-16317","DOIUrl":"https://doi.org/10.4050/f-0076-2020-16317","url":null,"abstract":"\u0000 In this work, a contract-based reasoning approach is developed for obstacle avoidance in unmanned aerial vehicles (UAV's) under evolving subsystem performance. This approach is built on an assume-guarantee framework, where each subsystem (guidance, navigation, control and the environment) assumes a certain level of performance from other subsystems and in turn provides a guarantee of its own performance. The assume-guarantee construct then assures the performance of the overall system (in this case, safe obstacle avoidance). The implementation of the assume-guarantee framework is done through a set of contracts that are encoded into the guidance subsystem, in the form of a set of inequality constraints in the trajectory planner. The inequalities encode the relationships between subsystem performance and operational limits that ensure safe and robust operation as the performance of the control and navigation subsystems and environment evolve over time. The contract inequalities can be obtained analytically or numerically using an optimization based path planner and UAV simulation. The methodology is evaluated in the context of head-on obstacle avoidance, where the contracts are constructed in terms of (1) minimum obstacle detection range, (2) expected obstacle size, (3) maximum allowed cruise velocity, (4) maximum allowable thrust, roll and pitch angles, and (5) inner-loop tracking performance. Numerical and analytical generation of these contracts for this scenario is demonstrated. Finally, in-flight contract enforcement is illustrated for typical scenarios.\u0000","PeriodicalId":293921,"journal":{"name":"Proceedings of the Vertical Flight Society 76th Annual Forum","volume":"147 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129919796","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reduced-Order Modeling and Analysis of Unsteady Rotor Hub Flows","authors":"Tristan D. Wall, J. Coder","doi":"10.4050/f-0076-2020-16465","DOIUrl":"https://doi.org/10.4050/f-0076-2020-16465","url":null,"abstract":"\u0000 Modal Decomposition is used to characterize high-fidelity flow fields for several different helicopter rotor hub variations in forward flight. Computational Fluid Dynamics (CFD) are carried out using the NASA OVERFLOW 2.2, Reynolds averaged Navier-Stokes solver. The simulated flow conditions and computational grids are based on experiments performed in a water tunnel at flight-relevant Reynolds numbers. The grids and computational methods used are discussed in further detail. Fast Fourier Transforms (FFT) are used to examine the force harmonics on the the surfaces of various hubs, revealing a dependence on geometric forcing. Mean-subtracted, space-only POD of the predicted lift and drag show a slow decay of modal energy, implying that a large number of modes is necessary to model the rotor hub. Space-only POD and Spectral Proper Orthogonal Decomposition (SPOD) are also used in an attempt to isolate and identify coherent flow structures in the rotor hub wake.\u0000","PeriodicalId":293921,"journal":{"name":"Proceedings of the Vertical Flight Society 76th Annual Forum","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126305625","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Aeroacoustic Analysis of a Side-by-Side Hybrid VTOL Aircraft","authors":"Zhongqi Jia, Seongkyu Lee, Davis","doi":"10.4050/f-0076-2020-16491","DOIUrl":"https://doi.org/10.4050/f-0076-2020-16491","url":null,"abstract":"\u0000 This paper investigates the acoustics of a side-by-side Urban Air Mobility (UAM) aircraft with 0%, 5%, 15%, and 25% rotor overlaps in forward flight based on high-fidelity Computational Fluid Dynamics (CFD) simulations. The CFD and acoustics simulations are carried out using the HPCMP CREATETM-AV rotorcraft simulation and analysis tool Helios and the acoustic prediction tool PSU-WOPWOP. The influence of the finest wake-grid spacing size on acoustic prediction of the side-by-side rotor with 0% overlap is studied based on two wake-grid spacing cases: 5% Ctip and 10% Ctip. No significant difference in overall sound pressure level (OASPL) is found between the two cases. The effect of rotor overlap on rotor acoustics is also assessed, and it is shown that the 25% overlap case yields higher OASPL than the other overlap cases particularly due to stronger rotor-to-rotor blade-vortex interactions (BVIs). Furthermore, the noise of the side-by-side rotor with 0% and 25% overlaps is compared against similar-sized helicopter noise and various background noise levels. It is shown that the side-by-side rotor noise is comparable with the noise of a similar-sized four-bladed helicopter in cruise. The OASPL difference of the overhead case is less than 10 dB, which does not meet the guideline that the UAM noise should be 15 dB lower than similar-sized helicopter noise. The results also show that the side-by-side rotor noise could not be fully masked by the freeway background noise at an altitude of 1,500 ft. Thus, noise reduction technology should be developed to overcome the barrier of public acceptance of UAM noise.\u0000","PeriodicalId":293921,"journal":{"name":"Proceedings of the Vertical Flight Society 76th Annual Forum","volume":"188 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124310780","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparison of Variator Technologies for Variable Rotor Speed Drivetrains for Rotorcraft","authors":"H. Amri, Lorenz Braumann, Florian Donner, F. Huber, M. Weigand","doi":"10.4050/f-0076-2020-16337","DOIUrl":"https://doi.org/10.4050/f-0076-2020-16337","url":null,"abstract":"The investigation presented in this paper is part of the international research project VARI-SPEED, which aims to invent a mass optimized speed variable drivetrain comprising a main gearbox with variable transmission ratio and a rotor suitable for rotor speed variation. A mass estimation model for the Sikorsky UH-60A drivetrain including a compound split was set up. Hydraulic, electric and mechanic variator technologies were investigated regarding their mass, torque and RPM properties. An optimization model was set up to find: 1.) The best variator technology for the mass optimized drivetrain. 2.) The best drivetrain for the mass optimized variator technology and 3.) The mass minimum if variator and drivetrain are considered both in the optimization loop. The research is performed to find out the influence of the variator technology on the mass and the design of the speed variable drivetrain. Furthermore, it is investigated, whether there is a preferable variator technology for rotor speed variation in rotorcraft. The investigation showed that the variator module has a significant influence on the optimal solution and that an individual optimization strategy is necessary for different drivetrain architectures as well as for different variator technologies. The electric variator technology seems to have the highest potential to enable an efficient variable rotor speed technology. At the moment the design is too heavy to gain benefits in efficiency. The mass estimation and optimization of the whole drivetrain including the variator is the basis to enable an assessment of usability of the variable rotor speed technology. Variation of the rotor speed within the drivetrain enables the turboshaft engine, the rotor and the auxiliary units each to operate at their optimal speeds. Rotor speed variation can overcome the divergent requirements between hover and fast forward flight, which is important for future rotorcraft like inventions in Future Vertical Lift (FVL) in the USA and CleanSky in Europe. Furthermore, it increases the efficiency, decreases fuel consumption andCO2- emission and reduces noise and environmental impact of rotorcraft.","PeriodicalId":293921,"journal":{"name":"Proceedings of the Vertical Flight Society 76th Annual Forum","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122831281","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fuel Cell Application for Small eVTOL UAVs","authors":"T. Seren, M. Hornung","doi":"10.4050/f-0076-2020-16320","DOIUrl":"https://doi.org/10.4050/f-0076-2020-16320","url":null,"abstract":"\u0000 This paper analyses the possibility of using hydrogen fuel cells as main energy provider for small to medium-sized eVTOL UAVs. A simplified model for eVTOL UAVs, which covers all relevant areas of aircraft design, including aerodynamics, structural mechanics, propulsion and systems modelling, is presented. Sensitivity studies with various design parameters, including aspect ratio and design cruise speed are performed to show their influence on the configurations’ performance. A comparison between pure battery electric and fuel cell hybrid UAVs is taken. The result of this paper is, that a hydrogen fuel cell hybrid configuration can have a better performance than a battery electric and it can be worth the effort to implement the fuel cell. To achieve this, the mission should require a long endurance and have hover and transition times reduced as far as possible, which both enable the high energy density of the hydrogen system to unfold its full potential. Also, the aircraft needs to be as aerodynamic efficient as possible in order to reduce the fixed weight of the hydrogen fuel cell. Respecting these requirements and accepting a reduced versatility of the aircraft, a fuel cell hybrid eVTOL UAV can easily outperform one with a pure battery electric power supply.\u0000","PeriodicalId":293921,"journal":{"name":"Proceedings of the Vertical Flight Society 76th Annual Forum","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123043518","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Health-Aware Digital Enterprise - A Blueprint for Digital Thread Integration for Future Vertical Lift Sustainment","authors":"M. Thomson, L. Caraway, B. Tucker, Bell","doi":"10.4050/f-0076-2020-16271","DOIUrl":"https://doi.org/10.4050/f-0076-2020-16271","url":null,"abstract":"\u0000 A primary factor for the development of military avionics systems is the requirement for a Modular Open System Architecture (MOSA). The US Department of Defense (DoD) is driving MOSA-compliant systems to achieve benefits in cost and flexibility within their procurements. MOSA definitions are examined in light of advances in computing disciplines that open the interfaces necessary for the aircraft operator to update and manage their fleet's Health Awareness Systems (HAS). Opening the relevant HAS interfaces via software configuration toolsets and MOSA building blocks avoids contracting for costly software changes and gives control of the update to the operator. Two business related factors are presented for consideration in developing the best way forward while using MOSA principles to guide development. These factors are (1) Intellectual Property (IP) and (2) the underlying investments companies make to develop IP. The need to routinely update the HAS to incorporate fleet lessons learned is inherent in the system's support. Updates may also reflect new methodologies that deliver the desired system control to the operator. The paper demonstrates a MOSA-compliant architecture via an example. Within the example, efficiencies are driven by an end-to-end Digital Thread that minimizes errors and rework while reducing the overall cost of change for the full platform lifecycle. The approach enables organic operator support, lowering the overall cost of aircraft operations. The design and support of the platform’s Health Awareness System benefits from the application of linked-automation. \u0000","PeriodicalId":293921,"journal":{"name":"Proceedings of the Vertical Flight Society 76th Annual Forum","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117173265","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Identifying Operator Workload State through Psychophysiological Metrics in Rotary-wing Simulated Flight","authors":"Kathryn A. Feltman, Kyle A. Bernhardt, A. Kelley","doi":"10.4050/f-0076-2020-16422","DOIUrl":"https://doi.org/10.4050/f-0076-2020-16422","url":null,"abstract":"\u0000 One study was completed, and another is underway, to examine whether psychophysiological measures can be used to identify operator workload during simulated rotary-wing flight. Results from the first study found some associations with psychophysiological measures and workload, while preliminary results from the current study suggest several associations with electroencephalogram measures and workload.\u0000","PeriodicalId":293921,"journal":{"name":"Proceedings of the Vertical Flight Society 76th Annual Forum","volume":"80 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115377160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}