ERF European Rotorcraft Forum
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Rotorcraft safety: A simulator-based training perspective
No full textTraining has the potential to inject a “safety vaccination” into the rotorcraft community by reducing the number of accidents. The term training should not be intended only in a strict sense, i.e., as pilot technical skills training, but more broadly as risk avoidance and safety culture training. As in the case of vaccination, where immunity is created only when applied on a large scale, helicopter accidents will not be eradicated until every player in the rotorcraft community is involved in the safety enhancement process. In particular, as outlined by accident and safety reports, a reduction in the helicopter accident rate cannot be accomplished disregarding pilots’ training and the contribution that flight simulators can provide to both training and certification. This paper provides an overview of the research into simulator training for helicopter pilots conducted as part of the European Joint Doctorate NITROS (Network for Innovative Training on Rotorcraft Safety). An approach that requires an in-depth analysis of the actual training task is adopted for two different maneuvers, namely hover and autorotation. This approach enables the training developer to understand what are the aspects of the actual training situation that should be reproduced in the simulated training situation to avoid ineffective training and negative transfer of skills. Moreover, such an approach allows to identify differences in terms of requirements between the training of basic and advanced maneuvers and between initial and recurrent training. The results of three different pilot-in-the-loop experiments, performed to explicitly confirm the effectiveness of developed training programs and to understand whether certain elements of the simulation can foster the development of superior flying skills, are summarized in this paper
Effect of aerodynamic interference to tail propeller on a compound helicopter
No full textComputational Fluid Dynamics (CFD) simulations are conducted focusing on a tail propeller on a conceptual model of a high-speed compound helicopter proposed by JAXA. Since a number of components such as fixed wing and propellers are added to a conventional helicopter, it is important to understand the aerodynamic interactions between the components. In this paper, the influence of aerodynamic interactions on the performance of the tail propeller with the main rotor and fuselage, and the influence on the fuselage drag from the tail propeller, are investigated. The propeller performance tends to improve when subjected to the main rotor wake, however, the effect becomes trivial as the advance ratio increases. As for the interaction between the fuselage and the propeller, it is shown that the propeller performance placed in the shadow of a fuselage improves instead of increasing the drag of the fuselage due to the induced flow by the propeller. After considering these conflicting effects, it was found that although they cancel each other out in terms of thrust and drag, the propeller efficiency itself has a large possibility of decreasing during high-speed fligh
Multicyclic vibration control of a helicopter rotor with active twist actuation
No full textThe vibration control performance of a Mach scaled Bo-105 rotor is evaluated using active twist multicyclic control. The simulation data for the baseline flight condition are generated using CAMRAD II. A linear, quasistatic, frequency domain model with up to six multicyclic higher harmonic control inputs and twelve harmonic response outputs of nonrotating hub loads are identified offline by the least squared error estimate. The optimal control input for minimizing the quadratic performance function along with the output response to the optimal control are calculated. The vibration reduction performances with the obtained optimal control input are calculated. The single harmonic control results show close agreement with the low vibration conditions by the amplitude and phase sweep method. When multicyclic control is applied, vibration reduction performance is improved compared to single harmonic control, and nonrotating hub vibration is reduced by up to 64%. A coupling of MATLAB and CAMRAD II is introduced to evaluate closed-loop multicyclic control systems. The coupled closed-loop analysis result shows good agreement with the simulation result using identified linear system model. The closed-loop control using the gradient descent algorithm shows very good vibration reduction performance and the reduced vibration level converges to the optimal solution
Alternative algorithms for helicopter control system based on inverse dynamics and its upgrade with the use of a sidestick controller
Get PDFThe modern trend of developing highly automated aircraft is characterized by a transition from traditional methods and technical solutions to innovative approaches of creating control systems, inceptors, and displays. This paper deals with the development of helicopter control systems based on inverse dynamics and its integration with a novel type of side stick shaping the pilot output signal such that it is proportional to the control force (Force Sensing Control - FSC). The synergetic effect arising from this integration is also evaluated. The evaluation of the effectiveness of inverse dynamics was carried out through mathematical modeling of the pilot-aircraft system and ground-based simulations
Experimental evaluation of the aerodynamic rotor/propeller interactions in hybrid compound helicopters
Get PDFThis paper focuses on the experimental evaluation of the rotor/propeller interactions in hybrid compound configurations. Experiments were conducted in the ONERA L2 large size-low speed wind tunnel with a 1/7.7 Dauphin 365N model and a four-bladed small-scale propeller. The exhaustive characterization of the propeller’s performance was previously realized. Measurements were conducted using two six-component scales, accelerometers, and toppers to monitor the rotational speeds. Different flight conditions were set with variating wind speed, propeller rotational speed, and propeller position. Comparing the isolated characterizations of the rotor and the propeller with the complete assembly highlighted the influence of the interactions on the performances of the rotating elements. Variating the location of the propeller around the helicopter allowed the determination of the optimal position to maximize the performance
Simulation and testing of helicopter-ship aerodynamic interaction
No full textDevelopment of a high-fidelity simulation environment, suitable for Helicopter-Ship Dynamic Interface testing has shown numerous advantages with respect to at-sea test campaigns. To correctly replicate the workload of the pilot, it is crucial to model the unsteady loads caused by complex aerodynamic interaction between airwake of the ship and inflow of the rotor. This paper aims to investigate the behaviour of the unsteady aerodynamic loads on a scaled-helicopter operating in the airwake of a generic frigate model. A series of wind tunnel tests have been conducted to characterise the unsteady loading for a wide range of wind speeds, directions and positions of the helicopter over the deck. A stern landing trajectory was simulated by trimming the rotor at different positions along an oblique path towards the landing spot. The unsteady measurements have been used to evaluate a numerical model developed by integrating the time-accurate CFD airwake of the isolated ship into the simulation environment. The numerical and experimental results show similar behaviour, as moving towards the landing spot the unsteadiness is increased. However, the numerical model underestimates the unsteadiness in most of the test points and the difference becomes more significant when testing with a 60_ wind-angle. Furthermore, a fully dynamic landing maneuver was tested in the wind tunnel to evaluate the effect of the approach velocity of the helicopter on the unsteady loads. In comparison to the measurements at fixed positions, the effect of approach velocity was found to be more significant when testing with the wind from the port side compare to the headwind condition
Aerodynamic simulation and adjoint-based optimisation of rotorcraft configurations
Get PDFThis paper presents high-fidelity, as well as, simplified CFD modelling approaches within an optimisation framework for compound rotorcraft configurations with rotor/propeller aerodynamic interactions. The actuator disk/line models are used to represent the main rotor for simulations of a generalised rotor/propeller combination. The propeller performance is analysed in detail, and large variations are observed in the single blade loading due to the main rotor wake. A simplified model for the rotor/propeller interaction simulation is also put forward, and an inflow distortion metric is proposed to quantify the aerodynamic interactions. With the help of a Kriging surrogate model and the inflow distortion metric, aerodynamic interferences through the propeller disk are quantitatively visualised with variations in the propeller position, propeller thrust, and main rotor advance ratio. Optimisation of the propeller position under the main rotor for minimised interference with rolling/pitching moment constraints are also attempted using both gradient-based (adjoint) and gradient-free (efficient global optimisation) approaches. The optimisation results are validated using blade resolved simulations, and fluctuations of the propeller single blade loading were effectively reduced due to the optimisation. The work is a first step towards high-fidelity methods for vehicle and configuration optimisation
LubForLife: more reliable and cost competitive VTOL electro-mechanical equipment, from multidisciplinary sizing to tribology impacts to lower cost of operation
Get PDFRe-lubrication of Electro-mechanical actuators (EMA) is synonymous with aircraft downtime, mobilising resources, increased aircraft operating costs and higher risk of fault conditions caused by human error. With the challenging task of eliminating re-lubrication during the entire electro-mechanical actuator operating life, UMBRAGROUP is leading a Research & Technology (R&T) project, called LubForLife, in collaboration with academics and industrial partners. This R&T project seeks to achieve more realistic results by addressing the needs of a real flight-control actuator based upon requirements set with one of the major airframer who is closely associated with the project and milestones. In this paper, UMBRAGROUP lists all the key design aspects identified as drivers for a ball screw based EMA and focuses, then, on some main aspects linked to tribology, architecture and configuration, laying the foundations for the definition of a new standard for electromechanical actuators with no maintenance tasks or very limited one
Particle tracking analysis of a rotor in ground effect
No full textComputational fluid dynamics (CFD) is used here to predict the behaviour of ground particles, uplifted by a two-bladed rotor. The main focus is to define a safety area where the presence of particles can be considered safe, and compare this area with other distance based criteria. Using data of three different aircraft, scaling factors have been used to take into account the different size of the small-rotor studied and real case scenarios. The results show how heavier helicopters may generate the most dangerous situations, in terms of presence of particles in a delimited area. Furthermore, parallel strategy is analysed, code performances are compared in terms of number of particles computed and amount of processors used for calculations
A coupled multibody - mid fidelity aerodynamic tool for the simulation of tiltrotor manoeuvres
No full textA nonlinear aeroelastic numerical tool was used in the present work for the evaluation of loads and vibratory levels of a tiltrotor aircraft during critical transient manoeuvres. The numerical tool applicable to fixed and rotary-wing aircraft was obtained by joining the multibody solver MBDyn and the mid-fidelity aerodynamic tool DUST, through the partitioned Multiphysics coupling library preCICE. The aim of this work was to assess the ability of the nonlinear approach implemented in the coupled MBDyn-DUST tool for the simulation of tiltrotor aerodynamics and dynamics during a roll manoeuvre to be used for the preliminary design of novel tiltrotor configurations. This activity was performed in the framework of the EU funded CleanSky 2 FORMOSA project, aimed to the design of a novel wing movable surface system for the NextGen Civil Tiltrotor aircraft