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Advanced concept of drive shaft system for hybrid high speed helicopter
Get PDFIn this paper, a new advanced concept of supercritical drive shaft system has been described. It is intended to work inside an aircraft’s wing, in very demanding conditions, such as narrow available space with a simultaneous significant relative displacement between sub-systems, transmitting higher mechanical power than conventional shafts. The standard approach, to design drive shafts, has been reconsidered and adapted to new requirements. This technology has been applied first to the X3 demonstrator and is pushed to a new leading edge level on the Rapid and Cost- Effective Rotorcraft (RACER) demonstrator. It is a hybrid high speed helicopter funded jointly by Airbus Helicopters and European Commission in frame of Clean Sky 2
Integration and test of a degraded visual environment system on H145
Get PDFThis paper reports on the integration, test and evaluation of a Degraded Visual Environment (DVE) system installed on an Airbus H145 (BK117 D-2) civil certified helicopter. The DVE system consists of a LiDAR sensor, an EVS camera and a head-tracked helmet mounted display system (HMD) integrated into the onboard HELIONIX® digital avionics suite. The DVE system combines sensor enhanced and synthetic elements of the external scene and provides an accurate representation of the real world for visual reference and safe manoeuvring in DVE. All systems were prototypically integrated into the H145 demonstrator in a serial-like manner, allowing for a potential serialization of the system. Extensive flight trials were conducted focusing on military as well as on civil HEMS missions and were used to verify the intended function and evaluate installed DVE system performance. The activities described herein are partially performed in the frame of a research project supported by the German Federal Office of Bundeswehr Equipment, Information Technology and In-Service Support (BAAINBw). Between November 2018 and March 2019 the system was successfully deployed in both ground and flight tests
Performance analysis of inertial twist morphing concept in hovering flight
Get PDFThis paper presents the initial performance analysis of a twist morphing concept based on moving a mass in the chordwise direction in hovering flight. The blade structure is considered to be made of composite materials with bend-twist coupling present in the layup. The chordwise movement of the added mass introduces an additional lag moment along the spar of the blade which is able to change the twist of the blade through the bend-twist coupling. Therefore, the twist of the blade is related to the mass position in the chordwise direction and its magnitude. The blade is modelled by using the geometrically exact fully intrinsic beam equations, and the aerodynamic loads are simulated by using the quasi-steady aerodynamic model combined with uniform inflow. The governing aeroelastic equations are discretized using a time-space scheme. The results show that when the mass moves in the chordwise direction of the blade, the twist distribution of the blade changes. This twist change results in variation of the aerodynamic loads and hence change the aerodynamic performance of the rotor. The results highlighting the importance of the added mass location and magnitude, and the lag-twist coupling value on the reduction in the rotor power required is presented
Mass optimisation of variable rotor speed compound split drivetrains for rotorcraft
Get PDFThis publication is part of the international research project VARI-SPEED, which aims to enable rotor speed variation for a modern and ecologically efficient aviation. A mass estimation model for two different Sikorsky UH-60A drivetrain architectures was set up, calculating the mass of gears from the main-gearbox-input-shaft to the rotor-shaft and the tail-drive-shaft. One architecture includes a single compound split for transmission ratio variation, located close to the main rotor shaft. The other contains two compound splits, each located close to the turboshaft engines. Calculations were performed with different boundary conditions and the feasibility was analysed. The questions, if the compound split is the dominating factor of the mass optimisation and if the drivetrain architecture has an influence should be answered. The influence of design boundaries and the impact of the efficiency should be analysed. The compound split is not the dominating factor. Also the drivetrain architecture has an influence on the mass optimisation but not on the compound split configuration. Design boundaries have an impact, but the optimum is stable. The efficiency can have a higher impact than the mass. Variator engines have to be chosen according to the drivetrain architecture. Variation of the rotor speed via the gearbox enables the turboshaft engine, the rotor and the auxiliary units to operate at their optimal speeds. Rotor speed variation can overcome the divergent requirements between hover and fast forward flight, increase the efficiency and reduce noise and environmental impact of rotorcraft
How Artificial Intelligence supports us to develop and qualify faster then certify
Get PDFNowadays, Artificial Intelligence is increasingly used to develop and support progress in many fields and industries, such as finance, medical, transportation …, especially for complex problem resolution. The paper presents how Airbus Helicopters introduces Artificial Intelligence in Material & Process activities, aiming, amongst other things, to reduce the time to market and optimize qualification then certification costs/risks. The paper integrates the results of a proof of concept, achieved on flame resistance behavior of composite materials, related to interior compartment / cargo self-extinguishing requirements (CS27/29 §853 and 855) and demonstrates how Artificial Intelligence supports Engineering activities. The significant novelty introduced in this work is the use of advanced data-analysis software to support engineers and experts throughout development and qualification steps. Within this study, various AI models have been trained using available experimental datasets from Airbus Helicopters and suppliers as described in Figure 1. Following that, the trained AI model has permitted to identify the most influencing parameters and allowed to focus interest on both critical and optimal setups to help materials experts to reach targets in terms of material performance. In addition, AI model also allows to predict the fire behavior of the material, for resin/fiber reinforcement/fire agent combinations that have not been tested experimentally. This point could be particularly useful for material development purpose. The main concern when initiating this study was the very small amount of data available for material science compared to usual “big data” applications. In material science, the number of influencing parameters (eg input parameters of the AI model) describing the variability of the problem is rather large: detailed description of the material itself, parameters influencing the production process, material testing conditions, etc… Considering this amount of parameters and the small quantity of data available, one could expect that the capability of AI models trained on such limited data sets would be quite poor to predict accurately the actual behavior of materials. Nevertheless, as material behavior is enforced by physics and chemistry laws, it has been shown that a few hundred of experimental data are enough to get reasonably good predictions with the models. This work demonstrates that, thanks to Artificial Intelligence support, Airbus Helicopters has improved its understanding of complex phenomena like flame resistance behavior. Main influencing parameters have been identified for the different tests configurations. And for each parameter, strong/weak ranges have been established. Doing tests in such critical conditions during materials screening phase should help to avoid failing tests in representative helicopter configurations and permit to speed up helicopter development and certification. The presented study also paves the way for material and processes optimizations for helicopter designs
Quasi-static loads analysis of a 5-bladed rotor in maneuver using CFD/CSD coupling
Get PDFThe airloads and structural loads of Light Civil Helicopter (LCH) rotor in a pull-up maneuver are investigated using a coupled approach between the computational structural dynamics (CSD) and computational fluid dynamics (CFD) methods. The LCH rotor characterized by 5-bladed system with elastomeric bearing and inter-bladed damper is modeled in the structural dynamics analysis. The periodic rotor solution along with its converged CFD/CSD delta airloads for steady level flight (? = 0.287) is used to perform the transient maneuver analysis. The resulting vehicle attitude angles and velocity profiles are then prescribed for the quasi-static maneuver analysis of the rotor. The predicted section airloads, vortex trajectories, angle of attack (AOA)distributions, and structural moments at specified instants and spatial locations are compared between transient CSD-alone predictions and quasi-static CFD/CSD maneuver results. It is demonstrated that CFD/CSD coupled results indicate more pronounced dynamic stall peaks and stronger 5 /rev oscillations on structural moments than those by the CSD-alone approach
Generalized measure of vibration exposure for helicopter pilots
Get PDFHelicopter pilots operate in a vibrating environment and the consequences vary depending on the affected body part. The usual method of evaluating the effects of vibration exposure is to calculate comfort levels as a result of whole body vibration. However, some other body parts are also adversely affected from vibration, such as hands and eyes, which in turn might degrade piloting quality. Therefore, a complete vibration assessment is necessary to reach a better estimation of pilot vibration exposure when comparing different configurations, tracking the changes during design and deciding on a safe flight envelope. This work presents a complete assessment by considering the vibrations on the seat surface, hand-grip of controls and vibration of the eye. As a result, the vibration measure includes comfort, handling and vision in a single formulation. The proposed measure is demonstrated by coupling a high-fidelity biodynamic pilot model to a helicopter aeroservoelastic model in a comprehensive simulation environment
Performance class 2 with defined limited exposure for offshore operation: use case and perspectives
Get PDFOriginally devised for offshore helicopter operation and with the objective to improve global safety (and not only the consequences of an engine failure), Airbus has developed the Performance Class 2 Defined Limited Exposure concept (PC2 DLE). PC2 DLE uses simple, robust and short take-off and landing procedures, associated with a given take-off and landing weight to calculate the exposure time and the objective risk in case of engine failure. The paper details some of the methodology developed for flight testing, tools developed for Flight manual documentations and customer use (PC2DLE iPhone/iPad applications). The H145 case will show the homogeneity developed between PC1 and PC2 DLE, with the goal of simplifying procedures and assure standardization for take-off and landing. It concludes by demonstrating how the PC2 DLE concept is a means to objectivize and reduce catastrophic risk - a key to flight safety! …and a concept that could be expanded to other types of operations
Experimental and numerical investigations of electromagnetic crimping process for joining of helicopter structures
Get PDFThe present study investigates the electromagnetic crimping process as an alternative to thermally welded joints with different form-fit elements like grooves, pockets, and knurlings. The electromagnetic joining technology is based on pulsed magnetic fields to shape components made of electrically conductive materials and it is able to manufacture form-fit or welded joints. First, the analytical methods are presented to design a lightweight helicopter’s cyclic stick by the electromagnetic joining process based on maximum applied pilot control forces. Furthermore, approaches to calculate the maximum axial and torsional load transfer between the joining partners are given. The results are used in a two dimensional finite-element simulation to determine the process parameters and to optimize the groove design with respect to shear stresses. A good agreement between the numerical results and the experimental investigations is shown. The pull-out force is set as the failure criterion of the connection and the specific joint strength of different groove shapes is compared with the analytical model. Due to the slight increase of the total weight at the presented weight analysis, proposals for design optimization with focus on the joining zone are made. Despite this fact, the cost analysis shows a reduction of production costs. The achieved main goal of the presented study is the proof of feasibility of substituting thermally welded connections with electromagnetically crimped joints made of lightweight components and the proof of the remarkable potential of reducing production costs and time of aeronautic components
Electric, swashplate-less individual blade control system to be wind tunnel tested in full-scale
No full textThis paper describes a novel principle of helicopter main rotor primary control, which is scheduled to be demonstrated within a full-scale wind tunnel test campaign. The presented concept uses individual high performance electrical actuators to control the pitch angle independently for each rotor blade. Thereby many limitations of conventional hydraulic control systems are overcome and new functionalities can be introduced which largely improve the rotor performance and attenuate its inherent limitations. First, the rationale behind that idea and the basic concept is described. Then the chosen test platform is introduced and its unique suitability for this technology is highlighted. The key requirements that have primarily driven the design are presented. Further, the practical realization and the system integration into the test rotor is detailed. Key components such as the actuator, actuator control unit and power electronics are described in more detail. Finally, the preparatory test setup in the System Integration Lab (SIL) test is discussed