ERF European Rotorcraft Forum
Not a member yet
4279 research outputs found
Sort by
Experimental test-bed for the identification of biodynamic feedthrough of helicopter-pilot systems
Get PDFThe design of rotorcraft, especially when the human-machine interaction is concerned, has to take into account the possible interactions between the pilot biomechanics and the rotorcraft dynamics. To this end, existing and novel design techniques and procedures geared toward robust prevention of Rotorcraft-Pilot Couplings need experimental validation to enable their effective application by OEMs. For this purpose, an experimental test bench, providing means to measure the biodynamic feedthrough of pilot-rotorcraft systems is presented. The system has been designed to be easily reconfigurable in order to represent different cockpit designs. Results obtained with a professional test pilot on two different cockpit layouts are presented. The identified biodynamic feedthrough transfer functions are then exploited along with a simplified representation of the helicopter heave dynamics to perform stability assessments regarding the collective bounce phenomenon
Load limiting control: a piloted simulation study
Get PDFThe aim of this paper is two fold; firstly, to integrate a previously developed life extending control scheme, viz., Load Limiting Control (LLC) scheme, with a visual cueing system, and secondly, to perform real-time piloted flight simulation experiments of the resulting architecture using the Georgia Tech Re-configurable Rotorcraft Flight Simulator. The piloted simulations assessed the effectiveness of the visual cue in limiting maneuver aggressiveness for component load limiting. Two maneuvers were considered in this study: a pitch doublet maneuver and a pull-up maneuver. From the results gathered during the experiment, it is found that, even though the implementation of an LLC scheme within a real system using a visual cueing architecture is viable, the time delay inherent in such a cueing paradigm can impede the overall performance of an LLC system
Retrofit of hydrogen-powered helicopters: An optimal approach
Get PDFIn the framework of developing a climate-neutral aviation industry, hydrogen could play a critical role in the future. Given hydrogen’s high specific energy but fuel cells’ low specific power, this technology can be effectively used in conjunction with batteries, which have opposing characteristics. To that end, it is critical to develop design methodologies that allow for effective component integration and weight optimization. Therefore, this article introduces an original algorithm, HERACLES, which solves a constrained non linear optimization problem, aiming to find the lightest hydrogen-driven powertrain able to replace the conventional thermal engine-driven powertrain of a generic rotorcraft, preserving its given Maximum Take Off Weight (MTOW) and airframe. In order to demonstrate the effectiveness of the methodology, this is applied to a reference helicopter representative of the heavy category, MTOW of about 9 ton, considering a FC-based architecture. The optimal results are presented and then compared to a first sizing guess, showing the improvements on the payload obtainable with a better system integration. Finally, some sensitivity studies are carried out to picture the impact of the main technological key performance indexes on aircraft payload
Aerodynamic predictions of the ship-helicopter dynamic interface with a dual-solver hybrid CFD methodology
Get PDFCharacterization of ship-helicopter dynamic interface (DI) aerodynamics is a challenging problem that must be addressed for safe naval helicopter operations. Current computational methods of simulating the DI employ highly expensive unsteady Reynolds-Averaged Navier-Stokes (uRANS) techniques that exceed the resources available for most applications. Newly-developed dual-solver hybrid computational fluid dynamics (CFD) techniques permit the resolution of the fundamental physics in the DI at up to 85% less computational costs compared to traditional methods through a reduction of the uRANS mesh size, faster initialization of the flow field, and decoupling of the ship and helicopter aerodynamic simulations. While detailed experimental data is not yet available, good qualitative agreement between fuselage loads in simulated DI scenarios with flight test vehicle accelerations is observed
Modelling of atmospheric turbulence in inhouse rotorcraft simulation tool: characterization and comparison
No full textIn the present work, integration of an atmospheric turbulence model approximating the von Kármán spectra into the TA Originated Rotorcraft Simulation (TOROS) tool is presented. The integrated atmospheric turbulence content consists of 3D velocity components based on the second order statistics. Prior to the implementation, the model is analyzed in detail. Turbulence model is compared with flight test data along with the helicopter flight dynamics model where the initial trim points and power spectral densities of the helicopter rates are used as validation parameters. The results indicate that injection of the atmospheric turbulence component significantly alter the helicopter control rates representing meaningful agreement with flight test data. In addition, the effect of the different aerodynamic surfaces is also analyzed. The results indicate that turbulence in main rotor is the major contributor to the energy spectrum for the heave and roll rates
Understanding flight-test data with CFD rotor simulations: an application case on the H175 helicopter
Get PDFIn this work, comparisons between flight test data and simulations for the H175 rotor in several flight conditions are proposed. The Computational Fluid Dynamics (CFD) analysis relies on isolated rotor models including different tab arrangements and elastic blades. URANS simulations are performed using the FLOWer solver and are coupled with the comprehensive analysis code CAMRADII, which provides the rotor CSD model and the helicopter trim. A loose-coupling method is applied by exchanging information between the CFD solver and the comprehensive code at each or after several full rotor revolutions until a converged trimmed solution is obtained. The flight test data includes blade control angles, sectional loads, control loads and damper loads allowing for an in-depth comparison between flight and simulations. A full helicopter trim is performed using the comprehensive aeromechanics code HOST in order to extract fuselage attitudes and aerodynamic forces used subsequently as trim targets for the isolated rotor coupled CSD/CFD simulations with 3 degrees of freedom (DoF) trim. Predictive capabilities are thus dependent on accurate modelling of the fuselage drag and download in the initial full helicopter trim, in order to obtain rotor positions and control angles similar to those seen in flight. A conventional (cruise) level flight as well as a high altitude level flight presenting dynamic stall have been simulated and analyzed with a focus on pitch link loads and inter-blade damper loads. Additional cases at higher load factors — namely turn manoeuvers at load factors 1.07g and 1.3g — are also presented
Structural filters preliminary design for the aeroservoelastic decoupling of a next generation civil tiltrotor technology demonstrator
Get PDFThe paper discusses the methodology used to design the structural notch filters used to guarantee the aeroservoelastic (ASE) stability of the NGCTR-TD tiltrotor. The complex configuration of a tiltrotor aircraft from one side, and the fly-by-wire control architecture from the other side, imply that several structural elastic modes can be sensed and excited by the Flight Control System (FCS), which on the contrary is intended to affect only the rigid aircraft motion. This control spill over can potentially affect the stability properties of the aircraft and a set of notch filters is then introduced to remove any adverse ASE coupling. The paper describes the numerical model used to assist the design of the notch filters and the optimization procedure used to get a configuration that achieves the best trade-off between ensuring ASE robust stability and keeping adequate (FCS) performances, that are inevitably affected by the introduction of the notch filters. The ASE stability assessment and the notch filters design need to be performed as early as possible during aircraft development, in particular this activity should be performed in conjunction with FCS design to allow the best compromise between aircraft handling qualities and stability. For this reason the analysis and filter design methodology described here allowed the management of several design iterations and will also accommodate further design adjustments that will be performed after prototype ground and flight tests
Stochastic simulation of ship airwake in helicopter shipboard operation
No full textFor the development of a high-fidelity simulation environment for shipboard operations, modelling the unsteady aerodynamic loads caused by mutual interaction of the rotor wake and ship airwake is of great importance. In this paper, a stochastic modelling approach is proposed which can significantly reduce the computational cost required for real-time implementation of turbulent airwake obtained by standard approaches based on time-accurate Computational Fluid Dynamics. Starting from the availability of measured data collected in a scaled wind tunnel experiment with a rigid rotor, it has been possible to identify a model for the airspeed disturbance generated by the mutual interaction between the rotor and the ship airflow that results in the same load spectrum measured in the experiment. First Frequency Response Functions are estimated to represent the aerodynamic loads of the rotor. Then, these functions are used to identify the frequency response of an external disturbance vector, composed of vertical, lateral and longitudinal velocity components, able to return the same load components on a model of the rotor. The identified disturbance speed components that represent the effect of the unsteady interaction can then be incorporated into the model of a full-scale flight simulator through a set of Auto-Regressive filters designed for each particular wind condition and rotor position over the deck. Exciting the AR filters by white noise results in the same frequency content as the identified gust. Validation is performed for two hovering positions over the deck of SFS1 in three different wind conditions. Comparing the unsteady loads with the experimental results demonstrates that this stochastic modelling approach is able to predict the unsteadiness across the frequency bandwidth which affects the pilot activitie
Hover performance predictions of coaxial rotor configurations using the updated cmtsvt multirotor inflow model
No full textThis paper uses the combined momentum theory and simple vortex theory (CMTSVT) multirotor inflow model for hover performance predictions of coaxial rotor configurations. The CMTSVT inflow model is updated with the wake contraction and decay functions, and their effects on performance predictions are discussed. For comparison, wind tunnel measurements available in the literature are used to study the effects of loading changes at the fixed axial separation distance and different axial separation distances at fixed loading settings. Apart from the figure of merit, power, and thrust sharing ratio predictions, factors such as the interference loss and rotor-rotor influence loss are determined to identify rotor-rotor interaction effects on the performance. Furthermore, the total, self, interference uniform inflow components along with the lower rotor inflow distributions plots are provided for further insight. It has been shown that additions of the wake contraction and decay functions tremendously improve the predictions of the CMTSVT inflow model. With additions of these real-flow effects, the CMTSVT inflow model can capture the effects of rotor-rotor interactions for different loading settings and axial separation distances
Application of global optimisation algorithms to multi-rotor systems
No full textThe presented study proposes a novel method for optimising rotors’ position in a generic, non-overlapping multi-rotor system. The approach uses global optimisation algorithms with an objective function based on a recently developed low-order aerodynamic model for rotor-on-rotor interference “RORI”. Two classical optimisation algorithms, Particle Swarm Optimisation and Genetic Algorithm, were used to ensure an algorithm-independent solution. The analysis was conducted on Twin-rotor, Tri-rotor and Tetra-rotor systems in a two-dimensional, unbounded optimisation space at a constant operating point. The results indicated that the best available minimum of the power ratio existed when rotors were reassembled into an inverse V-shaped formation pattern. The performance assessment of optimisation algorithms revealed that the Particle Swarm Optimisation outperformed the Genetic Algorithm in terms of mean execution time and solution repetitiveness for a given optimisation problem. The comparison against the Free-Vortex Wake model showed an agreement within 5% across all verification cases, indicating the potential of the proposed approach