A 1:4.25-scale model of a generic helicopter rotor hub was tested at Reynolds numbers ranging from 1.75 × 106 to 7 × 106 at advance ratio of 0.2 in The Pennsylvania State University Applied Research Laboratory Garfield Thomas 48-inch diameter water tunnel. Measurements including drag and wake characteristics were performed up to full-scale Reynolds number with respect to an industry-representative helicopter rotor hub. In particular, the variation of drag and flow field with Reynolds number was characterized. Load measurements were conducted using an improved load cell design, with greater accuracy than in previous experiments. Wake velocity was measured using laser Doppler velocimetry at two downstream planes, yielding velocity statistics to the second order. Improved load measurement accuracy and wake velocity spatial resolution, at full-scale Reynolds number, provide a unique dataset for computational fluid dynamics validation as part of the Penn State Rotor Hub Flow Prediction Workshops and physical insight into rotor hub flows.
{"title":"Full-Scale Reynolds Number Testing of Rotor Hub Drag and Wake Turbulence","authors":"D. Reich, M. Krane, S. Willits, S. Schmitz","doi":"10.4050/jahs.67.042008","DOIUrl":"https://doi.org/10.4050/jahs.67.042008","url":null,"abstract":"A 1:4.25-scale model of a generic helicopter rotor hub was tested at Reynolds numbers ranging from 1.75 × 106 to 7 × 106 at advance ratio of 0.2 in The Pennsylvania State University Applied Research Laboratory Garfield Thomas 48-inch diameter water tunnel. Measurements including drag and wake characteristics were performed up to full-scale Reynolds number with respect to an industry-representative helicopter rotor hub. In particular, the variation of drag and flow field with Reynolds number was characterized. Load measurements were conducted using an improved load cell design, with greater accuracy than in previous experiments. Wake velocity was measured using laser Doppler velocimetry at two downstream planes, yielding velocity statistics to the second order. Improved load measurement accuracy and wake velocity spatial resolution, at full-scale Reynolds number, provide a unique dataset for computational fluid dynamics validation as part of the Penn State Rotor Hub Flow Prediction Workshops and physical insight into rotor hub flows.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70218184","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To model unsteady airfoil aerodynamics in forward and reverse flows in a simple and robust manner requires a strong understanding of the complex flow dynamics and their relation to first-order concepts. The current work explores the relation between the leading-edge suction force, represented nondimensionally by the leading-edge suction parameter (LESP), and the flow physics of forward and reverse dynamic stall as a function of freestream Reynolds number, airfoil thickness, and motion kinematics for the NACA 0012, 0015, and 0018 airfoils using computational tools. The relation between the LESP and critical events associated with leading-edge vortex (LEV) shedding was found to be independent of flow direction barring the signature to identify LEV initiation. Leading-edge suction was observed to continue to increase after LEV initiation in reverse flow and could be attributed to the combined effect of a weak LEV and strong trailing-edge vortice. While LESP, forces, and moments were found to be moderately dependent on airfoil thickness and strongly dependent on the Reynolds number in forward flow conditions and the critical LESP, in addition, was weakly dependent on motion kinematics, the aerodynamics were observed to be largely independent of said parameters in reverse flow. This allows for a single critical LESP value to be used for symmetric airfoils to indicate LEV initiation when the blunt edge is experiencing reversed flow, a finding which serves to largely reduce the empirical dependencies while modeling unsteady reverse dynamic stall in low-order methods.
{"title":"Leading-Edge Suction Behavior of Unsteady Airfoils in Forward and Reverse Flows","authors":"S. Narsipur, Ashok Gopalarathnam","doi":"10.4050/jahs.68.022009","DOIUrl":"https://doi.org/10.4050/jahs.68.022009","url":null,"abstract":"To model unsteady airfoil aerodynamics in forward and reverse flows in a simple and robust manner requires a strong understanding of the complex flow dynamics and their relation to first-order concepts. The current work explores the relation between the leading-edge suction force, represented nondimensionally by the leading-edge suction parameter (LESP), and the flow physics of forward and reverse dynamic stall as a function of freestream Reynolds number, airfoil thickness, and motion kinematics for the NACA 0012, 0015, and 0018 airfoils using computational tools. The relation between the LESP and critical events associated with leading-edge vortex (LEV) shedding was found to be independent of flow direction barring the signature to identify LEV initiation. Leading-edge suction was observed to continue to increase after LEV initiation in reverse flow and could be attributed to the combined effect of a weak LEV and strong trailing-edge vortice. While LESP, forces, and moments were found to be moderately dependent on airfoil thickness and strongly dependent on the Reynolds number in forward flow conditions and the critical LESP, in addition, was weakly dependent on motion kinematics, the aerodynamics were observed to be largely independent of said parameters in reverse flow. This allows for a single critical LESP value to be used for symmetric airfoils to indicate LEV initiation when the blunt edge is experiencing reversed flow, a finding which serves to largely reduce the empirical dependencies while modeling unsteady reverse dynamic stall in low-order methods.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70218914","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. McKay, Praneet Vayalali, F. Gandhi, T. Berger, Mark J. S. Lopez
An elastic blade flight dynamics model for a coaxial helicopter platform based on the Sikorsky X2 Technology™ Demonstrator is presented and validated with steady trim and frequency response flight-test data. A full authority explicit model following control architecture along with pseudoinverse control allocation is implemented for the model in hover and cruise at 180 kt using CONDUIT® in order to stabilize the vehicle and meet a set of stability, handling qualities, and performance requirements. Different fault scenarios are considered including failure of rotor swashplate actuators and tail surface actuators in hover and forward flight, which are compensated for by recalculating the pseudoinverse control mixing accordingly. The approach is shown to maintain aircraft stability through the fault transient and into a new steady trim state for the vehicle. Though the implemented controller is successful in maintaining the aircraft state, different fault cases lead to violations in rotor tip clearance limits, which will require additional effort to account for in flight.
{"title":"Control Allocation Reconfiguration for Actuator Failure on a Coaxial-Pusher Helicopter","authors":"M. McKay, Praneet Vayalali, F. Gandhi, T. Berger, Mark J. S. Lopez","doi":"10.4050/jahs.68.032004","DOIUrl":"https://doi.org/10.4050/jahs.68.032004","url":null,"abstract":"An elastic blade flight dynamics model for a coaxial helicopter platform based on the Sikorsky X2 Technology™ Demonstrator is presented and validated with steady trim and frequency response flight-test data. A full authority explicit model following control architecture along with pseudoinverse control allocation is implemented for the model in hover and cruise at 180 kt using CONDUIT® in order to stabilize the vehicle and meet a set of stability, handling qualities, and performance requirements. Different fault scenarios are considered including failure of rotor swashplate actuators and tail surface actuators in hover and forward flight, which are compensated for by recalculating the pseudoinverse control mixing accordingly. The approach is shown to maintain aircraft stability through the fault transient and into a new steady trim state for the vehicle. Though the implemented controller is successful in maintaining the aircraft state, different fault cases lead to violations in rotor tip clearance limits, which will require additional effort to account for in flight.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70219082","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The high-fidelity computational fluid dynamics (CFD) tool CREATE™-AV HELIOS is used to investigate the interactional aerodynamics of the XV-15 tiltrotor in this work. The full vehicle is studied in a quasi-static manner with various airspeeds, nacelle angles, and vehicle attitudes to simulate hover-to-forward flight transition. The rotor is trimmed using CFD/CSD coupling with CAMRAD II. Significant wing-on-rotor interactions are observed where the thickness and loading effects of the wing create an impulsive doublet loading on the rotor as it passes over the wings. Furthermore, the wing is shown to alter the blade–vortex interactions of the rotor at high nacelle angles. The rotor in turn noticeably alters the lift and drag characteristics of the wing. At moderate to low nacelle angles, the rotor downwash enhances the dynamic pressure primarily on the upper surface of the wing, increasing the total wing lift by up to 14%. The effect on the drag varies depending on the nacelle angle. At high nacelle angles, the rotor is shown to decrease both lift and drag of the wing by 15% and 20%, respectively. Overall, this work serves to illuminate and quantify some of the complex aerodynamic interactions that occur during the conversion maneuver of tiltrotor aircraft.
{"title":"Interactional Aerodynamics of the XV-15 Tiltrotor Aircraft during Conversion Maneuvers","authors":"S. Tran, Joon W. Lim","doi":"10.4050/jahs.67.032005","DOIUrl":"https://doi.org/10.4050/jahs.67.032005","url":null,"abstract":"The high-fidelity computational fluid dynamics (CFD) tool CREATE™-AV HELIOS is used to investigate the interactional aerodynamics of the XV-15 tiltrotor in this work. The full vehicle is studied in a quasi-static manner with various airspeeds, nacelle angles, and vehicle attitudes to simulate hover-to-forward flight transition. The rotor is trimmed using CFD/CSD coupling with CAMRAD II. Significant wing-on-rotor interactions are observed where the thickness and loading effects of the wing create an impulsive doublet loading on the rotor as it passes over the wings. Furthermore, the wing is shown to alter the blade–vortex interactions of the rotor at high nacelle angles. The rotor in turn noticeably alters the lift and drag characteristics of the wing. At moderate to low nacelle angles, the rotor downwash enhances the dynamic pressure primarily on the upper surface of the wing, increasing the total wing lift by up to 14%. The effect on the drag varies depending on the nacelle angle. At high nacelle angles, the rotor is shown to decrease both lift and drag of the wing by 15% and 20%, respectively. Overall, this work serves to illuminate and quantify some of the complex aerodynamic interactions that occur during the conversion maneuver of tiltrotor aircraft.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70217236","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The power required to hover a helicopter is fundamental to any new or modified performance flight-testing effort. The conventional method of relating two nondimensional variables (coefficients of power and weight) is overly simplified and neglects compressibility effects in the power required to hover under a wide range of gross weights and atmospheric conditions. An alternative flight-test method for assessing hover performance while addressing this deficiency of the conventional method is proposed. The method uses an original list of 15 corrected variables derived from fundamental dimensional analysis, which is further reduced by means of dimensionality reduction to include only the most essential and effective predictors. The method is demonstrated using data of a Bell Jet-Ranger and shows that at the 95% confidence level; the averaged prediction error is only 0.9 hp (0.3% of the maximum continuous power). Using the same data, the conventional method yields a much larger averaged prediction error of 1.7 hp.
{"title":"A Dimensionality Reduction Approach in Helicopter Hover Performance Flight Testing","authors":"I. Arush, M. Pavel, M. Mulder","doi":"10.4050/jahs.67.032010","DOIUrl":"https://doi.org/10.4050/jahs.67.032010","url":null,"abstract":"The power required to hover a helicopter is fundamental to any new or modified performance flight-testing effort. The conventional method of relating two nondimensional variables (coefficients of power and weight) is overly simplified and neglects compressibility effects in the power required to hover under a wide range of gross weights and atmospheric conditions. An alternative flight-test method for assessing hover performance while addressing this deficiency of the conventional method is proposed. The method uses an original list of 15 corrected variables derived from fundamental dimensional analysis, which is further reduced by means of dimensionality reduction to include only the most essential and effective predictors. The method is demonstrated using data of a Bell Jet-Ranger and shows that at the 95% confidence level; the averaged prediction error is only 0.9 hp (0.3% of the maximum continuous power). Using the same data, the conventional method yields a much larger averaged prediction error of 1.7 hp.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70217663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper discusses the development of a numerical method for the approximation of the nonlinear time-periodic rotorcraft flight dynamics with higher order linear time-invariant (LTI) models. The method relies on a per-rotor revolution perturbation scheme, which is of particular importance for the linearization of simulation models that do not allow for per-time-step perturbations, and for those output measures that necessitate the solution of partial differential equations and thus require several time steps to be computed. The paper demonstrates the application of the proposed methodology to obtain high-order LTI models capable of predicting vibrations for a generic utility helicopter. Simulations are used to validate the response of the linearized models against those from nonlinear simulations and from competing approaches in the literature. The proposed method is shown to predict accurately the nonlinear response for the case shown and for small amplitude maneuvers. Frequency-domain validation is also performed to compare the linear models derived with the proposed method with those obtained with harmonic decomposition, a competing approach based on a per-time-step perturbation scheme. Interestingly, the proposed algorithm yields nearly identical numerical results compared to harmonic decomposition, suggesting that the two methods are in fact equivalent but rely on different formulations.
{"title":"Linear Time-Invariant Approximations of Nonlinear Time-Periodic Systems","authors":"Umberto Saetti, J. Horn","doi":"10.4050/jahs.68.012006","DOIUrl":"https://doi.org/10.4050/jahs.68.012006","url":null,"abstract":"This paper discusses the development of a numerical method for the approximation of the nonlinear time-periodic rotorcraft flight dynamics with higher order linear time-invariant (LTI) models. The method relies on a per-rotor revolution perturbation scheme, which is of particular importance for the linearization of simulation models that do not allow for per-time-step perturbations, and for those output measures that necessitate the solution of partial differential equations and thus require several time steps to be computed. The paper demonstrates the application of the proposed methodology to obtain high-order LTI models capable of predicting vibrations for a generic utility helicopter. Simulations are used to validate the response of the linearized models against those from nonlinear simulations and from competing approaches in the literature. The proposed method is shown to predict accurately the nonlinear response for the case shown and for small amplitude maneuvers. Frequency-domain validation is also performed to compare the linear models derived with the proposed method with those obtained with harmonic decomposition, a competing approach based on a per-time-step perturbation scheme. Interestingly, the proposed algorithm yields nearly identical numerical results compared to harmonic decomposition, suggesting that the two methods are in fact equivalent but rely on different formulations.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70218756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper investigates tonal and broadband noise for rotor designs used on urban air mobility vehicles. Quiet helicopter rotor designs with varying tip speeds and blade numbers are studied for the tonal and broadband noise at the same mission specification. The rotor aerodynamics in edge-wise forward flight are calculated using the blade element theory coupled with a dynamic inflow model and the moment-balance trim analysis. Loading noise and thickness noise are obtained using the lifting-line loading distribution and the dual-compact thickness noise model in PSU-WOPWOP. With the forward flight capability developed in UCD-QuietFly, broadband noise, including trailing-edge noise, trailing-edge bluntness noise, and airfoil stall noise, is predicted. Psychoacoustic metrics, such as fluctuation and roughness, are used to quantify the human subjective annoyance levels. The relative importance between tonal noise and broadband noise is investigated for various design cases and operating conditions. It is found that broadband noise is the dominant noise source for the rotor designs with low tip speeds and fewer blades, while tonal noise is dominant for the high-tip-speed designs. A low tip speed and more blades are found to be the preferable design features in terms of psychoacoustic metrics.
{"title":"Acoustic Analysis and Sound Quality Assessment of a Quiet Helicopter for Air Taxi Operations","authors":"Sicheng Li, Seongkyu Lee","doi":"10.4050/jahs.67.032001","DOIUrl":"https://doi.org/10.4050/jahs.67.032001","url":null,"abstract":"This paper investigates tonal and broadband noise for rotor designs used on urban air mobility vehicles. Quiet helicopter rotor designs with varying tip speeds and blade numbers are studied for the tonal and broadband noise at the same mission specification. The rotor aerodynamics in edge-wise forward flight are calculated using the blade element theory coupled with a dynamic inflow model and the moment-balance trim analysis. Loading noise and thickness noise are obtained using the lifting-line loading distribution and the dual-compact thickness noise model in PSU-WOPWOP. With the forward flight capability developed in UCD-QuietFly, broadband noise, including trailing-edge noise, trailing-edge bluntness noise, and airfoil stall noise, is predicted. Psychoacoustic metrics, such as fluctuation and roughness, are used to quantify the human subjective annoyance levels. The relative importance between tonal noise and broadband noise is investigated for various design cases and operating conditions. It is found that broadband noise is the dominant noise source for the rotor designs with low tip speeds and fewer blades, while tonal noise is dominant for the high-tip-speed designs. A low tip speed and more blades are found to be the preferable design features in terms of psychoacoustic metrics.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70217264","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Xin, J. Horn, Roy Brewer, D. Klyde, Cody E. Fegely, Paul Ruckel, Frank Conway, Sean P. Pitoniak, William C. Fell, J. Rigsby, R. Mulato, P. Schulze, Carl Ott, C. Blanken
Cofunded by the U.S. Army and industry, a Sikorsky-led team that features industry and academia developed and evaluated a set of mission task elements (MTE) to address rotorcraft high-speed handling qualities. The MTEs were designed to meet different levels of precision and aggressiveness. The Break Turn MTE was defined for nonprecision, aggressive applications. The MTE objectives, descriptions, and performance criteria were developed via piloted simulation sessions at each team's simulator, each featuring a unique high-speed platform including a coaxial compound helicopter, two tiltrotors, and a generic winged compound helicopter. Formal evaluations were conducted by U.S. Army test pilots. Baseline control laws were varied to achieve different handling qualities levels. Quantitative measures based on task performance and qualitative measures based on pilot ratings, comments, and questionnaires were used to assess MTE effectiveness. It was demonstrated that the Break Turn MTE provided an effective means to discern nonprecision, aggressive handling qualities in high-speed flight.
{"title":"Further Development and Piloted Simulation Evaluation of the Break Turn ADS-33 Mission Task Element","authors":"H. Xin, J. Horn, Roy Brewer, D. Klyde, Cody E. Fegely, Paul Ruckel, Frank Conway, Sean P. Pitoniak, William C. Fell, J. Rigsby, R. Mulato, P. Schulze, Carl Ott, C. Blanken","doi":"10.4050/jahs.67.042003","DOIUrl":"https://doi.org/10.4050/jahs.67.042003","url":null,"abstract":"Cofunded by the U.S. Army and industry, a Sikorsky-led team that features industry and academia developed and evaluated a set of mission task elements (MTE) to address rotorcraft high-speed handling qualities. The MTEs were designed to meet different levels of precision and aggressiveness. The Break Turn MTE was defined for nonprecision, aggressive applications. The MTE objectives, descriptions, and performance criteria were developed via piloted simulation sessions at each team's simulator, each featuring a unique high-speed platform including a coaxial compound helicopter, two tiltrotors, and a generic winged compound helicopter. Formal evaluations were conducted by U.S. Army test pilots. Baseline control laws were varied to achieve different handling qualities levels. Quantitative measures based on task performance and qualitative measures based on pilot ratings, comments, and questionnaires were used to assess MTE effectiveness. It was demonstrated that the Break Turn MTE provided an effective means to discern nonprecision, aggressive handling qualities in high-speed flight.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70218362","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shipboard launch and recovery of helicopters continue to pose operational challenges even to experienced pilots. The present research seeks to develop novel visual and control augmentation techniques and determine their impact on human factors for shipboard recovery operations. The paper first outlines the development and integration of a helicopter–ship dynamic interface model into a wide field of view, fixed-base rotorcraft simulation environment. The paper then describes the development of novel visual and control augmentation techniques for pilot assistance during shipboard recovery. Visual augmentation includes two-dimensional primary flight information and three-dimensional conformal shipboard landing symbology presented on a low-cost, off-the-shelf, see-through head-mounted display system to facilitate “eyes-out” piloting. Control augmentation includes robust nonlinear control laws producing translational rate command position hold, and acceleration command velocity hold response types with good predicted handling qualities. Finally, the paper reports experimental results of simulated visual shipboard approaches conducted with four experimental test pilots for low- and high-intensity ship motions. The results indicate improved piloting performance, mitigation of pilot-induced oscillations, lower workload, improved handling, and improved perceived safety for fleet pilots for the proposed visual and control augmentation techniques.
{"title":"Visual and Control Augmentation Techniques for Pilot Assistance During Helicopter Shipboard Recovery","authors":"T. Mehling, Omkar Halbe, M. Hajek, M. Vrdoljak","doi":"10.4050/jahs.67.042004","DOIUrl":"https://doi.org/10.4050/jahs.67.042004","url":null,"abstract":"Shipboard launch and recovery of helicopters continue to pose operational challenges even to experienced pilots. The present research seeks to develop novel visual and control augmentation techniques and determine their impact on human factors for shipboard recovery operations. The paper first outlines the development and integration of a helicopter–ship dynamic interface model into a wide field of view, fixed-base rotorcraft simulation environment. The paper then describes the development of novel visual and control augmentation techniques for pilot assistance during shipboard recovery. Visual augmentation includes two-dimensional primary flight information and three-dimensional conformal shipboard landing symbology presented on a low-cost, off-the-shelf, see-through head-mounted display system to facilitate “eyes-out” piloting. Control augmentation includes robust nonlinear control laws producing translational rate command position hold, and acceleration command velocity hold response types with good predicted handling qualities. Finally, the paper reports experimental results of simulated visual shipboard approaches conducted with four experimental test pilots for low- and high-intensity ship motions. The results indicate improved piloting performance, mitigation of pilot-induced oscillations, lower workload, improved handling, and improved perceived safety for fleet pilots for the proposed visual and control augmentation techniques.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70218519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The load transfer principles of coaxial rotors are analyzed from a theoretical point of view. The theoretical expressions of hub forces and moments are derived by summing the Fourier series of the root forces and moments from all the blades of a coaxial rotor system with the assumption that the rotor loads are identical between the two rotors. The analytical relations indicate that changing the rotor-to-rotor phase angle may be used to reduce (and even eliminate) the magnitudes of specific harmonics of rotor thrust, drag, and pitching moment, but the reduction is accompanied by an increase in the magnitudes of rotor side force, rolling moment, and torque for the same harmonic and vice versa.
{"title":"Loads Transfer Principles of Coaxial Helicopter Rotors","authors":"D. Han, G. Barakos","doi":"10.4050/jahs.68.012008","DOIUrl":"https://doi.org/10.4050/jahs.68.012008","url":null,"abstract":"The load transfer principles of coaxial rotors are analyzed from a theoretical point of view. The theoretical expressions of hub forces and moments are derived by summing the Fourier series of the root forces and moments from all the blades of a coaxial rotor system with the assumption that the rotor loads are identical between the two rotors. The analytical relations indicate that changing the rotor-to-rotor phase angle may be used to reduce (and even eliminate) the magnitudes of specific harmonics of rotor thrust, drag, and pitching moment, but the reduction is accompanied by an increase in the magnitudes of rotor side force, rolling moment, and torque for the same harmonic and vice versa.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70218824","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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