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Linear parameter varying control for XV-15 tiltrotor vehicle during transition
Get PDFThis manuscript applies Linear-Parameter-Varying control methods to a validated XV-15 tilt rotor vehicle, aiming to develop the flight control system specifically for the transition period. The proposed control law uses self-scheduling H? design synthesis, which not only guarantees the closed-loop stability over the entire parameter space, but also ensures a prescribed level of performance. Simulation results show that the controller can offer very good performance in terms of reference tracking and disturbance rejection, indicating that the pilot’s workload can be reduced significantl
Experimental investigation of the influence of different helicopter ramp geometries on the wake structure
Get PDFIn this work, the influence of two different rear fuselage upsweep geometries on the aerodynamic characteristics of a multipurpose medium lift helicopter fuselage is investigated. The fuselage geometry was very similar to Mil Mi-8 helicopter fuselage. The balance measurements, which were obtained at T-1K wind tunnel of KNRTU-KAI named after A.N. Tupolev, were supplemented with PIV measurements. Obtained results indicate that the flat ramp has higher drag coefficient values at negative angles of attack, compared to conventional rear fuselage upsweep geometry. The vortex core circulation of the vortices, obtained from PIV velocity fields showed the flow field behind the flat ramp of the fuselage had much higher vortex circulation values compared to conventional rear fuselage upsweep
Life cycle assessment of an integrated upper skin wing box for next generation civil tiltrotor
Get PDFThe Next-Generation Civil Tiltrotor (NextGenCTR) will be one of the main flying demonstrators to be developed in the Clean Sky 2 Research Programme for the Fast Rotorcraft Innovative Aircraft Demonstrator Platform (IADP). Technology demonstration activities will be addressed to provide significant improvement with respect to current state-of-the-art Tiltrotors technologies. One of the key enabling feature of a civil Tiltrotor will be the advanced wing architecture having high level of integration able to minimize number of components, junctions and masses. Such optimization is mandatory to avoid the related structural weaknesses induced by its size, different operational configurations and unconventional/challenging flight conditions. Within Fast Rotorcraft (FRC) IADP Work Package 1, the T-WING project is aimed at developing, manufacturing, testing, and qualifying an Innovative Composite Wing for NextGenCTR. Specific T-WING new design and production techniques are fully relevant to the wider scope of Eco-Design Concept Implementation (FRC-IADP WP3) aiming to demonstrate the greening of rotorcraft production processes. The Life Cycle Assessment (LCA) method defined for T-Wing complies with standard rules for assessing the environmental impact of the life cycle of a generic product (ISO 14040, 14044) from the extraction of raw materials, manufacturing and assembly processes (i.e. following a ‘cradle-to-gate’ approach). The use of such standards has been recognized as an effective way to assure a systemic and robust assessment. The standardized general rules drive a fruitful and effective approach to compare info, data collection criterions, data tracking methods and for result reporting. The life cycle inventory describes, in a detailed way, the wing box part characteristics, processes and the impact contributions referring to one single wing box with related air emissions, discharge in waters and soils through the full manufacturing process. Preliminary LCA results, will be presented in order to identify, quantify, and evaluate environmental differences between a conventional structural concept and the innovative highly integrated upper skin wing box designed in the T-WING project
Improvement of aerodynamic performance of a winged compound helicopter due to single-rotor lift-offset
Get PDFA system of single-rotor lift-offset combined with differential flaps on the fixed wing is investigated through numerical simulations. A simplified computational model consisting of a main rotor and a winged-body is utilized. The aerodynamic performance is evaluated in high-speed cruising flight where the advance ratio is 0.7. The effect of lift-offset on overall aerodynamic performance and the influence of aerodynamic interaction on the wing are investigated for the UH-60A rotor blade and the optimized rotor blade designed at JAXA. Numerical results show that the single-rotor lift-offset combined with the differential flaps significantly improves the overall aerodynamic performance for both rotors. The lift-offset dramatically enhances the rotor performance and minimizes the reduction of the aerodynamic performance of the winged-body due to the interaction with the rotor. Different interactional effects between the rotors with the wing are observed. It is observed that highly twisted blades significantly impact the wing under the advancing side due to the aerodynamic interactions
Helicopter ergonomics - a pilot’s view
Get PDFIt is widely recognized that human factors contribute either directly or indirectly to a majority of aircraft accidents and incidents. Moreover, the design of the flight deck and systems can influence the crew performance. When pilots read that human factors are a major contributing factor, they always think “this could have been me”. Discomfort of the flight deck is something to deal with on a daily basis. To shed a different light on this matter we ask questions, and hope to help the engineers, manufactures and operators to understand our everyday struggle
Towards uncertainty quantification of the ONERA 7A rotor using comprehensive analysis
No full textThe uncertainty and sensitivity of rotor blade torsion stiffness on rotor power and maximum torsion moment is studied. Comprehensive analysis tools are used to establish rotor performance and structural loads. A global-based uncertainty propagation scheme was applied using a scaling factor to uniformly induce spanwise variability in blade torsion stiffness using Monte Carlo simulations. A local-based uncertainty propagation scheme was also applied with a third-order polynomial function to induce a non-uniform distribution of material stiffness. The analysis confirmed that uncertainty in torsion stiffness has negligible impact on rotor power and maximum amplitude torsion moment along the blade span for the considered high-speed case. The analysis does confirm a pronounced effect on half peak-to-peak torsion moment at specific blade span stations where experimental measurements are available. Additionally, a sensitivity analysis using a non-uniform distribution approach with a scaling factor facilitated a comprehensive quantification of the direct and interaction effects between the uncertain parameters on the response outputs
Load limiting control : a handling qualities analysis
No full textThe aim of this paper is to study the impact of two component load limiting controllers (LLC), viz., command limiting LLC and control limiting LLC, on the quantitative handling qualities speci1cations during pitch maneuvers in the forward flight regime. Specifically, the maximum achievable load factor, the pitch attitude quickness, the agility quickness, and the load quickness parameters are used as metrics to quantify the impact of both LLC schemes on the handling qualities performance of the helicopter. The pitch attitude and agility quickness criteria are used to quantify the agility of the helicopter. The load quickness is used to measure the performance of the component load limiting controllers by quantifying the build up of load on the component during maneuvering flight. Results demonstrate that both component load limiting controllers have similar impact on the pitch attitude quickness, load quickness, and maximum achievable load factor. Furthermore, it is observed that the command limiting LLC has less detrimental effect on the agility quickness when compared to the control limiting LLC
Evaluation of acoustic shielding effects from a generic GARTEUR helicopter configuration
Get PDFThis paper presents the activities in the GARTEUR Action Group HC/AG-24 to study the noise scattering of helicopter rotors in the presence of the fuselage. The focus of the Action Group is on the development and the validation of numerical prediction methods and on establishing an experimental data base for numerical validations. This paper will focus on the results from the wind tunnel and the numerical activities achieved in the last stage of the project. Shielding experiments were conducted in DLR’s Acoustic Wind tunnel in Braunschweig (AWB) using point and rotor noise sources. The numerical methods used in the group include Boundary Element Method (BEM) for solving the Helmholtz equation and Computational AeroAcoustic method (CAA) for solving the linearized Euler equations. The acoustic scattering predictions are compared to test data
Exploratory evaluation of side-stick flight sciences on variable stability research aircraft: a study of inceptor throw and force gradient
Get PDFThere is increasing evidence of the benefits of active side-stick inceptors in rotorcraft in areas such as pilot comfort, handling qualities, safety, limit protection, and cockpit design. In-flight evaluations of an active force-sensing (large-displacement, position-output) side-stick inceptor were conducted on the NRC Bell 412 Advanced Systems Research Aircraft. The aircraft was configured with a Rate Damped control response type in pitch and roll axes. A number of qualitative and quantitative results due to side-stick setting preferences were gathered. For a survey of modified ADS-33E-PRF Depart-Abort and Lateral-Reposition mission task elements in good cueing conditions, static setting preferences included average longitudinal and lateral force-gradients of 0.43 N/mm and 0.32 N/mm, respectively. The associated longitudinal and lateral throw limits were 19.3 mm and 25.8 mm, respectively. Dynamic setting preferences included maximum longitudinal and lateral natural frequencies of 16 rad/sec and 15 rad/sec, respectively, combined with average damping ratios of 0.65. In a high bandwidth variable stability helicopter application, this study exposed both benefits (rapid tailoring, comfort) and limiting conditions (physical static and dynamic constraints) of active side-stick technology
APQP & geometrical management supporting entry into service
Get PDFGeometrical Management of Key Characteristics (KC) starts with System Engineering and continues with functional analysis of the vehicle during the development phase. As next APQP (Advanced Product Quality Planning), focusing on industrial maturity and repeatability during the industrialization phase is performed and finally, the process ends with a control plan, which is deployed after entry into service for the serial life of the product. This is a top-down approach leading to systems specification during the three main phases of the Helicopter lifecycle: • Design development, • Industrialization (MAP - Industrial Process Improvement) • Serial life During Industrialization, we focus on the demonstration of process robustness considering system requirements and program specifications. It includes process definition and requires product/process optimization (MAP) a Specification Verification phase. During Serial life, we shall provide optimized methods and tools matching with quality and production objectives (OTD, OQM, ramp-up) and viewing results format. Since the tolerances are represented by a network, we have defined a format for injecting the results at a given level as input data to the next level. Due to the nature and interconnections of this network, the volume of data to be processed can be significant. So we have implemented an appropriate numerical technique to deal with a continuous influx of measurement data. The objective was to propose a comprehensible representation of the re-evaluated risks at each stage of the process, i.e.: - Initial risks related to the current helicopter definition - Re-evaluated risks related to an aircraft serial number completed with each new measurement of characteristics for this aircraft. - Re-evaluated risks related to the observed variability of the product/process. The aim of this paper is to present the geometrical risk evaluation at each step of the development for preparation to H/C EIS (Entry Into Service) phase, which is also called “Ramp-up” phase, based on one system example: A cockpit door integration