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Light eVTOL possible aerodynamic configurations analysis
Get PDFThe present study endeavors to consider the most popular eVTOL aerodynamic concepts employed nowadays. This research gives a theoretical evaluation of the possible VTOL design with different electric or hybrid power plant configurations. Conventional rotorcraft, quadcopter with ducted fans or just rotors have been considered. Relationship between eVTOL mass parameters and available power of the power plant is calculated. Performance of the VTOL with full electric and different hybrid power plants in forward flight mode is estimated. Available and required power needs for speed envelope in hover and maximal speed modes are calculated. Optimal specific parameters (batteries, generators, electric motors) of fully electric and hybrid power plant elements are defined to provide acceptable eVTOL flight performance
Helicopter parameters estimation from subspace identification by constrained nonlinear optimization
Get PDFSubspace identification uses well-understood techniques based on linear algebra and numerical methods. However, the state space model matrices which are obtained from conventional subspace identification algorithms are not necessarily associated with the physical states. This may be evaluated as a deficiency for the area of helicopter flight dynamics where physical parameter estimation is mainly conducted for mathematical model improvement, aerodynamic parameter validation and flight controller tuning. There are a limited number of studies in literature, which tackle this problem. Some of these studies are based on nonlinear optimization. However this optimization problem may have infinitely many solutions if we do not define well-founded constraints. It may be possible to estimate the real physical parameters by establishing the constraints which compatible with practical values. This study focuses on to the determination physical constraints for the parameters which are confined to the problem described here. For this purpose, the subjected parameters are examined according to their physical meaning. Both the expected theoretical values and the experimental knowledge are evaluated to determine the constraints. Then, many runs are conducted for these predefined constraints with randomly selected initial condition
Aerodynamic design and optimisation of main rotors for light rotorcrafts
No full textThe main goal of the presented research has been to prove that optimal design of main-rotor blades may significantly improve a performance of light rotorcraft. The paper presents results of several studies aimed at improvement of performance of several rotorcrafts including: UAV helicopter, light gyroplane and ultralight helicopter. All the presented studies have been conducted using similar methodologies of optimal parametric design of main rotor. Blades of all main rotors have been built based on the airfoils optimised towards specific design criteria and conditions resulting from the priority flight conditions and assumed primary mission of the designed rotorcraft. Whole the design process has been conducted based on advanced computational methods and software
Preparation of input and validation data for PZL SW-4 helicopter dynamic model in scope of HELIMARIS project
No full textHELIMARIS project ("Modification of an optionally piloted helicopter to maritime mission performance") aims in preparation of maritime operation of PZL SW-4 helicopter. Due to operational and economic issues, it is a reasonable approach to simulate the most hazardous flight stages before proceeding to flight test. Warsaw University of Technology (WUT) developed PZL SW-4 helicopter dynamic model implemented in FLIGHTLAB environment in scope of HELIMARIS project. The model should represent actual performance and dynamics of helicopter in basic flight states (hover, cruise, climb/descent, turn, etc.). Compliance with this requirement allows to predict PZL SW-4 behavior in harsh maritime environment, especially focused on ship approach, in a reliable manner. Presented effort is complementary with analyses and laboratory tests done simultaneously by the other project subcontractor - Ship Design and Research Centre (CTO), which purpose is to obtain ship air wake and helideck motion data to be integrated in FLIGHTLAB environment. Investigation will result in definition of safe and efficient operational procedure for light maritime helicopter. The purpose of the paper is to present each particular phase of required input data preparation done by PZL-?widnik (Original Equipment Manufacturer; OEM). Therefore, it provides necessary background for detailed control algorithms description and regulator system adjustment, performed by Warsaw University of Technology. PZL-?widnik provided definition of mass, inertial and geometrical data set in basic helicopter configuration. This included geometry of main rotor hub, tail rotor hub, stabilizers and landing gear. Position of sensors, indicators and all relevant systems was defined. Main rotor system definition contains also damping characteristics of lag damper. Main rotor and tail rotor blades were defined in terms of necessary properties distribution (mass, inertia, chord). Aerodynamic characteristics of airfoils in entire range of section Mach number were verified and tailored in order to achieve flight test compliance. Static stiffness and strength of landing gear was obtained from stand test results, including also limits for landing conditions. Fuselage was defined in terms of aerodynamics. Due to high predicted angles of attack and sideslip in ship air wake, supplementation of already used characteristics was required. CFD (Computational Fluid Dynamics) ANSYS Fluent solver was employed to obtain missing data. Results were tailored to obtain compliance with existing characteristics in narrow range of inflow angles and with actual power required for flight. Fuselage aerodynamics is to be supplemented by floats once detailed configuration is available. Helicopter control system was defined in terms of kinematic ratio between controls and swashplate position. Kinematics of swashplate was supplemented by longitudinal/lateral feathering coupling and main rotor flap feathering coupling formulation. Dynamic characteristic of hydraulic actuators was also provided. PZL-?widnik calculated vortex ring conditions envelope. Propulsion system definition was a distinct phase of dynamic model development. It included description of kinematic ratio between collective lever and engine control lever position. PZL-?widnik provided detailed kinematics of engine controls and nominal engine control characteristics (nominal output power vs engine control lever position). Fuel system mass flow limits and tank capacity were based on PZL SW-4 Rotorcraft Flight Manual. Simultaneously, set of flight test data was prepared. Dedicated flight test program was prepared and performed. It contained measurements of state parameters relevant for dynamic identification in time domain and validation of the model. First of all, sign convention and measurement system characteristics were provided to obtain compliance and integrity with simulation results. Then, controls input signals were defined for dynamic response investigation. There were two types of inputs - long step and fast doublet. Two groups of dynamic response flight states were established: near-ground maneuvers (hover in-ground effect, hover off-ground effect, directional movements) and forward flights (level flight, climbing/descent, turns). Each contained both long step and fast doublet control input in every control channel (collective, longitudinal cyclic, lateral cyclic, pedals). General description of test helicopter configuration and external conditions were provided. Second stage of flight test was equilibrium conditions and control margins investigation. PZL-?widnik provided detailed controls positon (swashplate pitch and roll), helicopter attitude (fuselage pitch and roll), and rotors collective angles in trimmed level flight. The same data set was prepared for autorotation. Static equilibrium conditions were compared with results obtained from own O50 FORTRAN code. The last group of static tests was in-ground controllability and maneuverability. It contains presentation of controls position vs wind azimuth. Distinct phase was a definition of static performance and dynamic characteristics of propulsion system. Static performance of RR M250-C20R/2 engine was calculated using Rolls-Royce application. Dynamic characteristic includes propulsion system time response in relevant flight states (start-up, vertical take-off, landing from high hover, entry into autorotation, recovery from autorotation). Dedicated on-ground propulsion system stability test was used for engine sub-model calibration. Initial validation of entire model was done with support of selected steady flight test data. Flight test data obtained from landings on a moving platform was used for initial definition of ship landing procedure. Approach and take-off profile were established. Data set contained state parameters measurements correlated with video recording of each particular approach. Additionally, influence of control chain dynamic stiffness and slack of the controls was assessed. Swashplate position calibrated from controls was compared with that calculated kinematically from actuator extension. MATLAB script was employed to calculate transfer function between actuators extension and swashplate position and to compare with flight measurements of actuator forces. Static slack of the controls was defined from stand tests. PZL provided also qualitative and quantitative criteria for dynamic model similarity assessment for both dynamic response and static equilibrium part. Page 2 of 17 Presented at 45th European Rotorcraft Forum, Warsaw, Poland, 17-20 September, 2019 This work is licensed under the Creative Commons Attribution International License (CC BY). Copyright © 2019 by author(s). These were defined in terms of simulation results as follows: response vector signs compliance, attitude deviation from measurement at certain time from input signal beginning, controls position difference in trimmed steady flight. A vital phase of the project is PZL SW-4 autopilot sub-model development. It required detailed definition of sub-system functionality, general architecture, emergency scenarios, requirements and limitations. Autopilot sub-model should allow to perform basic flight states in whole PZL SW-4 operational envelope with Stability Augmentation System (SAS) functionality. Additional automatic flight modes will be tailored to support wide spectrum of maritime missions in both manned and unmanned configuration. The most critical phase is automatic vertical take-off and landing with sea state up to 5. Manual landing procedure will be extensively examined during simulation campaign
Performance optimization of plate airfoils for Martian rotor applications using a genetic algorithm
Get PDFThe Mars Helicopter Technology Demonstrator will be flying on the NASA Mars 2020 rover mission scheduled to launch in July of 2020. The goal is to demonstrate the viability and potential of heavier-than-air vehicles in the Martian atmosphere. Research is performed at the Jet Propulsion Laboratory and NASA Ames Research Center to extend these capabilities and develop the Mars Science Helicopter as the next possible step for Martian rotorcraft. The Mars Science Helicopter mass is scaled up to the 5 to 20 kg range, allowing a greater payload (approximately 0.5 to 2.0 kg), and greater range (approximately 3 km). Key to achieving these targets is careful aerodynamic rotor design. The Martian atmosphere’s low density and the small helicopter rotors result in very low chord-based Reynolds number flows, which reduces rotor performance. A continuous genetic algorithm is developed to optimize airfoil shapes at representative conditions for the Martian atmosphere. Previous research indicates that sharp leading edges and plate-like airfoils can out-perform conventional airfoil shapes. The present optimization allows for camber and thickness variation of curved and polygonal thin airfoils with sharp leading edges. The airfoil performance is evaluated at the highest attainable liftto-drag ratio near a moderate lift coefficient at compressible Mach numbers, as expected for Martian rotor application. Increases between 16% and 29% in airfoil lift-to-drag ratio at fixed lift coefficients are observed when compared with the Mars Helicopter Technology Demonstrator airfoils. Improvements in hover figure of merit are estimated to be between 4% and 10%, when applied to the Mars Helicopter Technology Demonstrator
Helicopter big data processing and predictive analytics: feedback & perspectives
Get PDFThis paper offers a comprehensive return of experience on the deployment of big data technologies enabling various descriptive and predictive analytics within the helicopter industry. It shows how these technologies can efficiently be employed to allow storing and processing the large quantity of flight data which are made available, and consequently how they offer additional analytics capabilities to the analysts. In order to demonstrate these benefits, the paper presents applications concerning statistical fleet data analysis and predictive maintenance. Concluding remarks are then given with particular attention to limitations of distributed big data technologies and challenges regarding their adoption within the industry
Low noise design and acoustic testing of the airbus helicopter H160-B
No full textThe noise certification and low noise levels of the newly developed Airbus Helicopters model, the H160-B, are presented in this paper. In the first part, the helicopter low-noise characteristics, as well as the certification methodology are described. In the second part, the noise certification results of the helicopter are presented and compared to available world fleet data, underlining the low noise levels of the H160-B helicopter. A detailed analysis, focusing on the approach condition, is then presented in a third part, relying on one hand on measurement data treated with a time-based source separation software (ROSI) and on the second hand on comprehensive code (ONERA HMMAP) numerical results. This analysis allows again validating of the effectiveness of the Blue Edge™ main rotor blade design in terms of nois
Multimodal pilot cueing for 360° situation awareness
No full textThe improved agility and flight control augmentation of Future Vertical Lift (FVL) aircraft will allow a variety of mission sets, extending the current helicopter reach to new terrains of operations such as high-altitude desert plateau and the urban canyons of megacities. Operations in megacities will require many of the same aviation capabilities of attack, reconnaissance, assault, and medical evacuation used in operations in less dense terrain, but with considerable constraints. Megacities offer limited landing and pickup zones. Flying close to the ground to provide air support is made more difficult by powerlines, antennas and satellites dishes, and narrow flight patterns between buildings. In this context, it is crucial to develop integrated multimodal interfaces that extend the current operational envelope while enhancing flight safety, providing a 360° SA coverage. Visual displays present inherent limitations due to partial representation of the threat space, because of their limited field-of-view (FOV) or their 2D exocentric perspective. Spatial auditory displays support a natural, ecologically valent, egocentric representation of space where auditory objects behave realistically in terms of direction, distance, and motion. Tactile displays also support a partial representation of 3D space, although with a lower resolution and typically limited to direction and motion. A study was conducted at the US Army Aeromedical Research Laboratory to evaluate the effectiveness of a trimodal display suite consisting of the Integrated Cueing Environment-Collision Avoidance Symbology (ICECAS) blended with the Primary Flight Display (PFD) symbology, an Integrated Collision Avoidance Display (ICAD) overlaying a panel-mounted terrain display (PMD), an Augmented-Reality Spatial Auditory Display (ARSAD), and the Tactile Situational Awareness System (TSAS). Ten UH60M Army evaluation pilots participated in a high-fidelity simulation at the U.S. Army Aeromedical Laboratory (USAARL) in the full-motion UH60 simulator. The results showed that deviations from Commanded Heading were the lowest when the Spatial Auditory Display was used, even more pronounced when the TSAS was activated. This suggests that the Auditory warning gives more time to the pilot to plan the avoidance trajectory. Overall, Exposure Time, which represents the frequency of Time on Task where at least one obstacle was present within the Threat Space (Caution and Warning regions around the ownship), was the lowest when using a combination of Visual, Spatial Auditory and Tactile Displays. Exposure Time to two obstacles (vs. one) was also the lowest with the trimodal Visual-Auditory-Tactile Display combination. When the Tactile Display was activated, the Time of Exposure in the Warning region was lower in the Visual-Auditory-Tactile than in the Visual-Tactile condition, indicating that the spatial auditory information led to a faster avoidance maneuver. These qualitative results validate the previously reported and new subjective data, and demonstrate the substantial advantage provided by multimodal displays for obstacle avoidance. The evolution of the multimodal Display suite and its physical integration for in flight demonstration are discussed in the context of pilot cueing synergies for the FVL multirole platform
Next generation active twist helicopter rotor blade - simulated results validated by experimental investigation
Get PDFVibration and noise are omnipresent in a helicopter environment and therefore their reduction is an important goal in helicopter research. Actuators embedded into the skin of a helicopter rotor blade can produce a twist, which influences the propagation of the air turbulence. Hence, vibration and noise levels can be reduced significantly. An important issue during operation of these rotor blades is the centrifugal load which affects the actuators and can cause a failure [3]. Based on the German Aerospace Center (DLR) project STAR (Smart Twisting Active Rotor), the design of an active twist rotor blade has been adapted, such that the loads in the actuator system can be significantly reduced and furthermore distributed evenly. This paper builds on previous publications [1-5]. After a brief summary of the improved blade design and the manufacturing process, this publication mainly refers to the determination of the structural blade properties of the first manufactured rotor blades. Specifically, torsional stiffness, lead lag bending stiffness as well as chordwise elastic axis position and twist performance are determined. These results are compared to the simulation findings and especially analyzed with regard to blade-to-blade differences. The experimental setup and also the measuring method are explained in detail
Modal passport application for dynamic properties validation and structural health monitoring of helicopter blades
Get PDFThe paper considers experimental techniques for research of modal properties of rotating helicopter blades. Sensors of vibration deformations and operational modal analysis techniques are chosen as the optimal tools for evaluation of modal properties of rotating blades. As a complex approach to the study of structural modal properties and its further usage the concept of modal passport is proposed. Authors discuss the setup and technical solutions of the experimental system for determining the modal properties of helicopter blades in statics and rotation. The stages of data processing obtained by the experimental system are described, including preliminary reduction of the periodic component, application of Experimental Modal Analysis (EMA) and Operational Modal Analysis (OMA) algorithms as well as formation of a typical modal passport of the blade. The samples of experimentally determined mode shapes of vibrations and deformations in statics and rotation are considered, as well as the analysis of various factors influence on the modal parameters of the blade. The modal deformation shape parameter, which has a diagnostic value and allows detecting even small changes in the mechanical properties of the blade, is outlined. Authors conclude about OMA techniques capability for deformation sensors application for determination of modal parameters of rotating blades. There are conclusions also about benefits of modal passport approach and its application for structural health monitoring (SHM) of helicopter structures, including blades