Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16808
W. Geyer, Barbara Gordon, C. Mattei, Dwight Robinson
In this work, a statistical time series method that is capable of effective multicopter rotor fault detection, identification, and quantification within a unified stochastic framework is introduced. The proposed framework is based on the functional model based method for fault magnitude estimation tackled within the context of statistical time series approaches. Estimator uncertainties are taken into account, and confidence intervals are provided for the fault magnitude of multicopter rotors. The framework employs functionally pooled (FP) models which are characterized by parameters that depend on the fault magnitude, as well as on proper statistical estimation and decision-making schemes. The validation and assessment is assessed via a proof-of-concept application to a hexacopter flying forward with a constant velocity under turbulence. The fault scenarios considered consist of the front and side rotor degradation ranging from healthy to complete failure with 20% fault increments. The method is shown to achieve fast fault detection, accurate identification, and precise magnitude estimation based on even a single measured signal obtained from aircraft sensors during flight. Furthermore, fault quantification is addressed via the use of both local ( boom acceleration) and global (IMU) sensors, with the signals collected from the boom supporting the identified faulty rotor proven to achieve better performance than the global signals, yet with a shorter signal length.
{"title":"Unified Statistical Framework for Rotor Fault Diagnosis on a Hexacopter via Functionally Pooled Stochastic Models","authors":"W. Geyer, Barbara Gordon, C. Mattei, Dwight Robinson","doi":"10.4050/f-0077-2021-16808","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16808","url":null,"abstract":"\u0000 In this work, a statistical time series method that is capable of effective multicopter rotor fault detection, identification, and quantification within a unified stochastic framework is introduced. The proposed framework is based on the functional model based method for fault magnitude estimation tackled within the context of statistical time series approaches. Estimator uncertainties are taken into account, and confidence intervals are provided for the fault magnitude of multicopter rotors. The framework employs functionally pooled (FP) models which are characterized by parameters that depend on the fault magnitude, as well as on proper statistical estimation and decision-making schemes. The validation and assessment is assessed via a proof-of-concept application to a hexacopter flying forward with a constant velocity under turbulence. The fault scenarios considered consist of the front and side rotor degradation ranging from healthy to complete failure with 20% fault increments. The method is shown to achieve fast fault detection, accurate identification, and precise magnitude estimation based on even a single measured signal obtained from aircraft sensors during flight. Furthermore, fault quantification is addressed via the use of both local ( boom acceleration) and global (IMU) sensors, with the signals collected from the boom supporting the identified faulty rotor proven to achieve better performance than the global signals, yet with a shorter signal length.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133513357","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}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16779
Matthew Asper, M. Ricci, J. Sirohi, G. A.
A novel thrust control method for an electrically-driven stacked rotor system is described. The stacked rotor comprises of two two-bladed rotors spinning in the same direction at the same speed, with a fixed axial spacing and variable azimuthal spacing. Changing the azimuthal spacing by around 22° results in a 17% change in the total rotor system thrust. An electromechanical model of the rotor and drive system is developed incorporating a blade element aerodynamic model and field oriented control of two phase-synchronized electric motors, each driving one rotor of the stacked system. The model is validated with measurements on a single, 2m diameter rotor in hover driven by a single electric motor at constant speed as well as during transient rotor speed changes. The validated model is used to explore the behavior of the system in response to a commanded change in rotor azimuthal spacing. At a blade loading of 0.08, and a rotor speed of 1200 RPM, computations indicated that a 5° change in azimuthal spacing could be achieved in less than 0.2s, or less than five rotor revolutions, requiring a transient power increase of 12% the mean power. These results indicate the feasibility of achieving small changes in thrust at a high bandwidth with a small increase in motor power output.
{"title":"Electromechanical Modeling and Testing of a Novel Electrically Driven Stacked Rotor System","authors":"Matthew Asper, M. Ricci, J. Sirohi, G. A.","doi":"10.4050/f-0077-2021-16779","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16779","url":null,"abstract":"\u0000 A novel thrust control method for an electrically-driven stacked rotor system is described. The stacked rotor comprises of two two-bladed rotors spinning in the same direction at the same speed, with a fixed axial spacing and variable azimuthal spacing. Changing the azimuthal spacing by around 22° results in a 17% change in the total rotor system thrust. An electromechanical model of the rotor and drive system is developed incorporating a blade element aerodynamic model and field oriented control of two phase-synchronized electric motors, each driving one rotor of the stacked system. The model is validated with measurements on a single, 2m diameter rotor in hover driven by a single electric motor at constant speed as well as during transient rotor speed changes. The validated model is used to explore the behavior of the system in response to a commanded change in rotor azimuthal spacing. At a blade loading of 0.08, and a rotor speed of 1200 RPM, computations indicated that a 5° change in azimuthal spacing could be achieved in less than 0.2s, or less than five rotor revolutions, requiring a transient power increase of 12% the mean power. These results indicate the feasibility of achieving small changes in thrust at a high bandwidth with a small increase in motor power output.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133685150","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}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16796
W. Geyer, Barbara Gordon, C. Mattei, Dwight Robinson
The U.S. Naval Test Pilot School (USNTPS) qualifies engineering test pilots and flight test engineers for the Department of Defense (DoD) and foreign militaries. The school operates UH-72A and UH-60L aircraft as core rotary wing platforms used for airborne instruction in performance, flying qualities (FQ) and advanced flight control systems flight testing. The stability and control portion of the syllabus teaches both time and frequency domain flight test techniques in the evaluation of aircraft handling qualities (HQ); however, only classic time domain techniques have been instructed in the aircraft to support the curriculum. As frequency domain testing has become common practice across the DoD and within industry, the importance of providing entry level instruction in those flight test techniques cannot be overstated. Having students conduct many of the frequency domain test techniques in the aircraft is not practical. Providing adequate control measures such as real-time data monitoring and instructor pilot involvement on each flight to ensure safe execution would place an unrealistic burden on the USNTPS staff and adversely impact the airworthiness of the school’s aircraft. The USNTPS simulation laboratory recently received a high fidelity UH-60 flight dynamics simulation model enabling the instruction of frequency domain flight test techniques and the collection of predictive HQ data as defined within the ADS-33E-PRF, Handling Qualities Requirements for Military Rotorcraft. These data are used to support assigned HQ flights flown on Naval Test Wing Atlantic’s ADS-33 Mission Task Element course. Conducting systems identification testing and the subsequent development of a high fidelity UH-72A flight dynamics simulation model allows the execution of the entire Low Airspeed FQ exercise across both core platforms. Simulator-based predictive HQ data are now utilized in support of assigned HQ flights in the respective aircraft. This paper covers the development of the UH-72A simulation model, flight test efforts supporting that development and the successful integration of the model as a means to collect predictive HQ data in support of the Low Airspeed FQ exercise at the USNTPS.
{"title":"Development of UH-72A Simulator Model in Support of ADS-33 Training","authors":"W. Geyer, Barbara Gordon, C. Mattei, Dwight Robinson","doi":"10.4050/f-0077-2021-16796","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16796","url":null,"abstract":"\u0000 The U.S. Naval Test Pilot School (USNTPS) qualifies engineering test pilots and flight test engineers for the Department of Defense (DoD) and foreign militaries. The school operates UH-72A and UH-60L aircraft as core rotary wing platforms used for airborne instruction in performance, flying qualities (FQ) and advanced flight control systems flight testing. The stability and control portion of the syllabus teaches both time and frequency domain flight test techniques in the evaluation of aircraft handling qualities (HQ); however, only classic time domain techniques have been instructed in the aircraft to support the curriculum. As frequency domain testing has become common practice across the DoD and within industry, the importance of providing entry level instruction in those flight test techniques cannot be overstated. Having students conduct many of the frequency domain test techniques in the aircraft is not practical. Providing adequate control measures such as real-time data monitoring and instructor pilot involvement on each flight to ensure safe execution would place an unrealistic burden on the USNTPS staff and adversely impact the airworthiness of the school’s aircraft. The USNTPS simulation laboratory recently received a high fidelity UH-60 flight dynamics simulation model enabling the instruction of frequency domain flight test techniques and the collection of predictive HQ data as defined within the ADS-33E-PRF, Handling Qualities Requirements for Military Rotorcraft. These data are used to support assigned HQ flights flown on Naval Test Wing Atlantic’s ADS-33 Mission Task Element course. Conducting systems identification testing and the subsequent development of a high fidelity UH-72A flight dynamics simulation model allows the execution of the entire Low Airspeed FQ exercise across both core platforms. Simulator-based predictive HQ data are now utilized in support of assigned HQ flights in the respective aircraft. This paper covers the development of the UH-72A simulation model, flight test efforts supporting that development and the successful integration of the model as a means to collect predictive HQ data in support of the Low Airspeed FQ exercise at the USNTPS.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"62 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115557909","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}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16825
H. Xin, A. Black, T. Herrmann, Patricia Jaeger, M. Luszcz, T. Smith, A. Thorsen, Chi Zhang
Flight dynamics models for engineering simulation are vital to rotorcraft design and testing. This paper focuses on a multi-year effort to develop and improve the S-97 RAIDER® flight dynamics model in State-Space GenHel and to correlate the model with flight test data. State-Space GenHel (SSGH) is an upgraded version of legacy GenHel with a series of new/enhanced modeling capabilities. The S-97 model has been used to support conceptual, preliminary, and detailed air vehicle design, control laws (CLAWS) design and tuning, handling qualities evaluation, flight loads development, system integration lab (SIL) testing, flight testing, and test pilot training. During the ongoing flight test program, the SSGH model has been continuously updated to improve correlation with the test data. The correlation spans a wide range of flight conditions including hover, low speed flight, level flight, chirp tests at different speeds, and various maneuvers. A series of reduced-order models and corrections were implemented in SSGH to capture the complicated physics missed in the baseline model. High-fidelity analytical tools and component test data were used to derive the parameters for these reduced-order models and corrections, with which the model-data correlation has been significantly improved. The paper also discusses the challenges in tip clearance prediction and in modeling the rotor on propeller interference. This study shows that an engineering model, continuously improved using appropriate methods, can capture the flight dynamics characteristics of a high-speed compound helicopter with sufficient accuracy for supporting CLAWS design and flight test.
{"title":"S-97 RAIDER® GenHel Model Development and Correlation with Flight Test Data","authors":"H. Xin, A. Black, T. Herrmann, Patricia Jaeger, M. Luszcz, T. Smith, A. Thorsen, Chi Zhang","doi":"10.4050/f-0077-2021-16825","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16825","url":null,"abstract":"\u0000 Flight dynamics models for engineering simulation are vital to rotorcraft design and testing. This paper focuses on a multi-year effort to develop and improve the S-97 RAIDER® flight dynamics model in State-Space GenHel and to correlate the model with flight test data. State-Space GenHel (SSGH) is an upgraded version of legacy GenHel with a series of new/enhanced modeling capabilities. The S-97 model has been used to support conceptual, preliminary, and detailed air vehicle design, control laws (CLAWS) design and tuning, handling qualities evaluation, flight loads development, system integration lab (SIL) testing, flight testing, and test pilot training. During the ongoing flight test program, the SSGH model has been continuously updated to improve correlation with the test data. The correlation spans a wide range of flight conditions including hover, low speed flight, level flight, chirp tests at different speeds, and various maneuvers. A series of reduced-order models and corrections were implemented in SSGH to capture the complicated physics missed in the baseline model. High-fidelity analytical tools and component test data were used to derive the parameters for these reduced-order models and corrections, with which the model-data correlation has been significantly improved. The paper also discusses the challenges in tip clearance prediction and in modeling the rotor on propeller interference. This study shows that an engineering model, continuously improved using appropriate methods, can capture the flight dynamics characteristics of a high-speed compound helicopter with sufficient accuracy for supporting CLAWS design and flight test.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117266697","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}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16731
T. Fitzgibbon, G. Barakos, M. Woodgate
This paper presents the demonstration of a high-fidelity optimisation framework applied to the AH-64A rotor blade planform. The framework implementation includes an adjoint-harmonic balance method, which allows for efficient performance predictions and evaluation of the design sensitivities for unsteady rotor flows, whilst maintaining the f idelity of the Navier-Stokes equations. A re-design of the AH-64A blade is performed, leading to significant performance benefits, and showing the great potential of high-fidelity CFD coupled with optimisation methods. The key design features that lead to performance improvements in hover and forward flight are discussed, including the advantages and disadvantages of blades with an offloaded blade tip. The influence of the optimisation setup, including the impact of the blade surface parameterisation, treatment of trim and number of harmonic balance modes within the CFDsolution on the final optimised shape is analysed throughout the paper.
{"title":"Optimisation of the AH-64A Blade Planform Based on High-Fidelity CFD Methods ","authors":"T. Fitzgibbon, G. Barakos, M. Woodgate","doi":"10.4050/f-0077-2021-16731","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16731","url":null,"abstract":"\u0000 This paper presents the demonstration of a high-fidelity optimisation framework applied to the AH-64A rotor blade planform. The framework implementation includes an adjoint-harmonic balance method, which allows for efficient performance predictions and evaluation of the design sensitivities for unsteady rotor flows, whilst maintaining the f idelity of the Navier-Stokes equations. A re-design of the AH-64A blade is performed, leading to significant performance benefits, and showing the great potential of high-fidelity CFD coupled with optimisation methods. The key design features that lead to performance improvements in hover and forward flight are discussed, including the advantages and disadvantages of blades with an offloaded blade tip. The influence of the optimisation setup, including the impact of the blade surface parameterisation, treatment of trim and number of harmonic balance modes within the CFDsolution on the final optimised shape is analysed throughout the paper.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117308724","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}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16845
B. Jalalahmadi, J. Rios
Sentient has developed a predictive modeling tool for components built using AM to assess their performance, with rigorous consideration of the microstructural properties governing the nucleation and propagation of fatigue cracks. This tool, called DigitalClone® for Additive Manufacturing (DCAM), is an Integrated Computational Materials Engineering (ICME) tool that includes models of crack initiation and damage progression with the high-fidelity process and microstructure modeling approaches. The predictive model has three main modules: process modeling, microstructure modeling, and fatigue modeling. The feasibility and validation of our modeling tool is verified using experimental coupon testing. The predictive tool is able to account for temperature and microstructure variation as the function of process parameters and scanning strategies at various AM processes. The relationship of processmicrostructure in additive manufacturing is successfully linked implicitly in our tool. We simulate the AM build process considering the parameters (laser intensity, laser speed, hatching space, powder layer thickness, orientation of build, etc.) involved during the build process in order to generate the microstructure of AM part which is the outcome of the build process. There is a good agreement between our prediction and the experimental data. The physics-based computational modeling encompassed within DCAM provides an efficient capability to fully explore the design space across geometries and materials, leading to components that represent the optimal combination of performance, reliability, and durability.
{"title":"Multi-physics Predictive Modeling Platform for Qualification of Material Microstructure and Mechanical Performance of Aerospace Additive Manufacturing Parts","authors":"B. Jalalahmadi, J. Rios","doi":"10.4050/f-0077-2021-16845","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16845","url":null,"abstract":"\u0000 Sentient has developed a predictive modeling tool for components built using AM to assess their performance, with rigorous consideration of the microstructural properties governing the nucleation and propagation of fatigue cracks. This tool, called DigitalClone® for Additive Manufacturing (DCAM), is an Integrated Computational Materials Engineering (ICME) tool that includes models of crack initiation and damage progression with the high-fidelity process and microstructure modeling approaches. The predictive model has three main modules: process modeling, microstructure modeling, and fatigue modeling. The feasibility and validation of our modeling tool is verified using experimental coupon testing. The predictive tool is able to account for temperature and microstructure variation as the function of process parameters and scanning strategies at various AM processes. The relationship of processmicrostructure in additive manufacturing is successfully linked implicitly in our tool. We simulate the AM build process considering the parameters (laser intensity, laser speed, hatching space, powder layer thickness, orientation of build, etc.) involved during the build process in order to generate the microstructure of AM part which is the outcome of the build process. There is a good agreement between our prediction and the experimental data. The physics-based computational modeling encompassed within DCAM provides an efficient capability to fully explore the design space across geometries and materials, leading to components that represent the optimal combination of performance, reliability, and durability.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115784667","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}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16705
M. Floros, Hao Kang
Coaxial, counter-rotating rotors from six to nine inches in diameter were evaluated to measure thrust and torque with variations in rotor spacing, thrust level, and the propeller pitch of the upper and lower rotors. The upper rotor was trimmed to specific thrust targets while the lower rotor was trimmed to produce zero overall torque. For the range of propeller pitch models tested, the data showed that increasing the propeller pitch on the lower rotor decreased the combined thrust of the coaxial system, but increased its efficiency. The rotor efficiency was insensitive to thrust level and rotor spacing, down to 0.116R. The lower rotor share of the overall thrust increased with increasing rotor diameter and with decreasing lower rotor pitch.
{"title":"Experimental Evaluation of Coaxial Micro-UAS Propellers","authors":"M. Floros, Hao Kang","doi":"10.4050/f-0077-2021-16705","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16705","url":null,"abstract":"Coaxial, counter-rotating rotors from six to nine inches in diameter were evaluated to measure thrust and torque with variations in rotor spacing, thrust level, and the propeller pitch of the upper and lower rotors. The upper rotor was trimmed to specific thrust targets while the lower rotor was trimmed to produce zero overall torque. For the range of propeller pitch models tested, the data showed that increasing the propeller pitch on the lower rotor decreased the combined thrust of the coaxial system, but increased its efficiency. The rotor efficiency was insensitive to thrust level and rotor spacing, down to 0.116R. The lower rotor share of the overall thrust increased with increasing rotor diameter and with decreasing lower rotor pitch.","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115320131","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}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16788
T. Jusko, Michael Jones
Helicopter operations with winch suspended loads are highly demanding for the flight crew. Without having a direct view on the load, pilots require assistance from a winch operator for load handling to achieve operational requirements (e.g. precise and safe positioning of a suspended person). An automatic load stabilization and positioning system for winching operations has been designed with the aim to reduce pilot and winch operator workload, damp load pendulum motion and to improve the load positioning performance. This system uses the concept of load motion feedback. To allow the winch operator to interact with the automatic positioning functions, a dedicated control interface is used. The system was implemented and evaluated in DLR’s Air Vehicle Simulator (AVES). Three pilots and one winch operator evaluated the system in different control law and crew task configurations in an offshore hoisting scenario. Handling Qualities (HQs) and pilot workload were evaluated using the Cooper-Harper Rating Scale and NASA Task Load Index respectively. The results show that the system can improve HQs, allowing better task performance and lower workload for the pilot and the winch operator when compared to an unassisted configuration.
{"title":"Evaluation of a Slung Load Control System for Piloted Winch Operations","authors":"T. Jusko, Michael Jones","doi":"10.4050/f-0077-2021-16788","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16788","url":null,"abstract":"\u0000 Helicopter operations with winch suspended loads are highly demanding for the flight crew. Without having a direct view on the load, pilots require assistance from a winch operator for load handling to achieve operational requirements (e.g. precise and safe positioning of a suspended person). An automatic load stabilization and positioning system for winching operations has been designed with the aim to reduce pilot and winch operator workload, damp load pendulum motion and to improve the load positioning performance. This system uses the concept of load motion feedback. To allow the winch operator to interact with the automatic positioning functions, a dedicated control interface is used. The system was implemented and evaluated in DLR’s Air Vehicle Simulator (AVES). Three pilots and one winch operator evaluated the system in different control law and crew task configurations in an offshore hoisting scenario. Handling Qualities (HQs) and pilot workload were evaluated using the Cooper-Harper Rating Scale and NASA Task Load Index respectively. The results show that the system can improve HQs, allowing better task performance and lower workload for the pilot and the winch operator when compared to an unassisted configuration.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124738527","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}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16762
Seyhan Gul, A. Datta
A hingeless hub tiltrotor with swept-tip blades was examined comprehensively with a new rotorcraft aeromechanics solver developed at the University of Maryland. The solver was verified with hypothetical U.S. government results and validated with Boeing M222 test data from 1972. A 20◦ sweep back from 80%R increased instability speed to 395 knots, an improvement of 70 knots. The key mechanism is the aerodynamic center shift. The trade-off is the increase in control system loads. Fundamental understanding of the physics is provided. Air resonance emerged as the critical phenomenon, not whirl flutter. Predictions in powered mode is necessary. At least first rotor flap, lag, and torsion modes need to be included. Rotor aerodynamics should use airfoil tables; wing aerodynamics is not important for air resonance. Analysis shows high speed flight is achievable with 13.5% wings but systematic wind tunnel tests with modern equipment is necessary for further validation.
{"title":"Aeroelastic Loads and Stability of Swept-Tip Hingeless Tiltrotors Toward 400 knots Flutter-Free Cruise","authors":"Seyhan Gul, A. Datta","doi":"10.4050/f-0077-2021-16762","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16762","url":null,"abstract":"\u0000 A hingeless hub tiltrotor with swept-tip blades was examined comprehensively with a new rotorcraft aeromechanics solver developed at the University of Maryland. The solver was verified with hypothetical U.S. government results and validated with Boeing M222 test data from 1972. A 20◦ sweep back from 80%R increased instability speed to 395 knots, an improvement of 70 knots. The key mechanism is the aerodynamic center shift. The trade-off is the increase in control system loads. Fundamental understanding of the physics is provided. Air resonance emerged as the critical phenomenon, not whirl flutter. Predictions in powered mode is necessary. At least first rotor flap, lag, and torsion modes need to be included. Rotor aerodynamics should use airfoil tables; wing aerodynamics is not important for air resonance. Analysis shows high speed flight is achievable with 13.5% wings but systematic wind tunnel tests with modern equipment is necessary for further validation.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"307 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123057449","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}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16820
Maximilian Fischer, Denis Heckmann, A. Nase
Several cities and regions have announced to launch electric Vertical Take-Off and Landing (eVTOL) based air taxi services in the future. To successfully implement such services, the financial viability must be assessed. As part of the project "SkyCab", an eVTOL based air taxi service concept was designed, associated costs to set-up such service assessed, major impact factors on the pricing identified and the willingness-to-pay of the target customers evaluated. The paper outlines the approach to evaluate the financial viability within five steps. First, the target customer group is identified based on the local mobility demand. Second, route network and vertiport locations are selected meeting the target customer trip demand and providing travel time saving benefits. Third, the willingness-to-pay is estimated: Therefore, the average financial power of the target customer groups is determined, and time and comfort advantages of an air taxi service compared to other means of transportation are evaluated. Fourth, the operational costs under consideration of the entire air taxi ecosystem are identified where pilot, aircraft and overhead costs contribute to 2/3 of the overall operational costs. Last, main operational impact factors such as the utilization rate, occupation rate and level of automation driving the financial viability are evaluated.
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