ERF European Rotorcraft Forum
Not a member yet
4279 research outputs found
Sort by
The H145 Bearingless Main Rotor - Earnings of the H135 heritage
Get PDFThe H135 helicopter family is the first serial helicopter with a Bearingless Main Rotor (BMR) after fully articulated and hingeless systems. Since 1996 the fleet of more than 1.300 aircraft has accumulated over 5 million flight hours. In parallel to this success a series of research projects have coalesced to the current status of the next generation BMR which is now the latest improvement for the H145 type to enter the market in 2020. The main rotor system of a helicopter has direct effects on a multitude of characteristics which form a set of requirements posing a sophisticated optimization challenge. In the financial category we have the manufacturing cost, which not only drive sales prices for a new helicopter and spare parts but also contribute to the cost of operation for the customer. Technically/operationally the performance - in absolute values as well as in relation to the fuel consumption -, reliability, comfort of ride, compact blade folding and maintainability play an important role. Finally, regulatory rules regarding safety and noise are an indispensable base layer. Solutions acquired encompass several new design solutions: the modular concept by separating the integrated blade of the H135 from the flexbeam/control cuff, a modified attachment area with a reduced flapping hinge offset and a new blade attachment design with bearing laminate. On the manufacturing side the introduction of Liquid Resin Infusion (LRI) technologies for cuff and blade helps to reduce cost while in the aeromechanic field a 5-bladed rotor layout with an advanced, optimized aerodynamic blade improves comfort of ride and performances. Flight tests have confirmed the expectations of a rotor system with low complexity, well balanced performances and excellent comfort of ride. The gains materialize in form of reduced cost, low weight and diminished maintenance effort and expenses. Due to this combination of benefits and the achieved maturity the H145 will profit from implementation of this next generation BMR
Comprehensive rotorcraft aeroacoustics: investigation of surface pressure distribution methods for rotor noise
No full textHaving full helicopter trim capability, comprehensive codes are indispensable for helicopter aeromechanics yet they operate over spanwise concentrated aerodynamic loads calculated at blade segment aerodynamic centers. In this study, an approach to generate distributed aerodynamic loads from comprehensive models, over real blade geometry for further aeroacoustic calculations of a helicopter rotor is proposed. Distribution of concentrated aerodynamic loads over upper and lower surface of the blade geometry with the help of an airfoil pressure database to prepare higher resolution data for acoustic solvers is studied. In order to assess the improvement, first, the concentrated aerodynamic loads are distributed over two-dimensional representative upper and lower surfaces then over three-dimensional blade geometry and acoustic signatures are compared with each other, HART-II wind tunnel test data and benchmark tool PSU-WOPWOP
A tool for pilot’s performance and engagement assessment in helicopter flight simulator
Get PDFThe accurate training procedures for future pilots are essential. There is need for objective performance and engagement assessment method. Only the combination of these two factors gives a full picture of pilot’s behaviour during the flight. This is the idea behind the general Objective Assessment Tool (gOAT) system. In the paper we present a tool for pilot’s performance assessment and the obtained results. One of the main advantages of the proposed method is high resolution enabling detailed, quantitative comparison of different flights. The solution combines many diverse criteria (varying largely in the range of obtained values) in order to generate one, scalar, easy comparable mark. The presented method was evaluated on data collected in helicopter flight simulator while performing the slalom Mission Task Element (MTE) adopted from ADS 33 [7]. The results analysis confirmed that the algorithm can accurately distinguish between the best and worst flights in terms of their handling quality, also appropriately points flights with similar performance. Thus it opened a path to create a fully objective system for detailed training assessment and pilot’s progress analysis. The advantage of the system is that its applications are not only limited to helicopter flight simulators. It could be also used in UAVs or mobile robots
UH-60A rotor and coupled rotor-fuselage simulation framework validation and analysis
Get PDFIn helicopter engineering advanced simulation means are available today which allow to run analysis and optimization tasks using modern computational capabilities [1-7]. In this context it is important to demonstrate the validity of the simulation model and the simulation approach by comparison with experimental data. This work establishes a validated reference model similar to the UH-60A for research activities on rotor blade design and analysis of rotor-fuselage coupling mechanisms. The focus is on structural representation. Literature is reviewed for data to define and validate the model. Main rotor performance and structural characteristics are in good agreement with the experimental data. Two independently established modal fuselage representations are mutually consistent and agree with literature at lower but not at higher frequencies. Coupled rotor-fuselage simulations show reasonable results compared to test data. However, the approach does not represent experimental mean half peak-to-peak hub accelerations exactly
Indicated airspeed estimation filter
Get PDFIndicated Airspeed (IAS) data play a critical role in aircraft flight control, both for pilot and Automatic Flight Control Systems. In unmanned aerial vehicles (UAVs) loss of IAS data could result in loss of aircraft control. This paper addresses the problem of IAS estimation after airdata sensor failure. A complementary filter with cutoff frequency dynamically adapted to flight condition is proposed. The complementary filter produces Airspeed estimation using aircraft attitudes, vertical speed and along heading acceleration. Filter output accuracy has been validated using about 100 hours of flight data at different speeds and altitudes. Comparison between actual flight data and the estimated IAS has shown a good match for all flight conditions, demonstrating the feasibility of using filter output data in case of airdata sensor failure
Evaluation of UAV configurations for package delivery missions though conceptual design
No full textConceptual sizing and performance estimation of four configurations for a package delivery mission is presented in this work. The multi-fidelity VTOL design framework HYDRA is used to size a notional quadcopter, hexacopter, quad-rotor bi-plane tailsitter (QBiT), and a lift-augmented tricopter for weight classes of 10 kg, 15 kg, 20 kg, and 25 kg. Sizing is performed using a combination of physics-based empty weight models for the airframe, rotor blades and wings, along with empirical models. A longitudinal trim methodology was implemented that minimizes the power required for a configuration for a given flight condition. Representative payload drop scenarios were constructed from different cruise speeds and ranges to identity a vehicle design in each configuration that can complete the most number of payload drop missions successfully. It is identified that the hexacopter performed better over the quadcopter in terms of requiring lower installed power and deliver heavier payload packages for a given radius of action. Wing-based designs such as the QBiT and tricopter are capable of delivering packages in a short time owing to either full/partial conversion to airplane mode during cruise flight
The use of co-simulation methodology in the project oF PZL SW-4 helicopter adaptation to maritime version
No full textThe article will present issues related to the implementation of the HELIMARIS project that assume modernization of PZL SW-4 to maritime mission and landing on vessel. The project encompasses issues related with helicopter adaptation (passive and active elements increase crew safety) to maritime version, basing on the context of the multidisciplinary analysis philosophy. The CO-SIMULATION calculation methodology involves the use of CFD analyzes for calculations of helicopter aerodynamic characteristics, both during flight and landing approach to vessel deck. The calculation model is a mapping of the CAD geometry of the helicopter model with the built-in RR 250 C20R engine, taking into account simplifications aimed at limiting the number of elements. The issues presented in the article will focus on the aerodynamic analysis of the helicopter in the case of unintentional activation of the floats and the assessment of the impact on the helicopter static and dynamic stability depending on the flight phase and on the current configuration, as well as the problem of turbulence interference between vessel and the helicopter during the approach to landing. The use of CFD (figure 1) analyzes includes hydrodynamic aspect of helicopter buoyancy and vessel motion on waves and allows to describe the dynamics of phenomena occurring during flight of helicopter conducting operations in cooperation with vessels. The collected information will help to develop procedures for safe and optimal landing approaches on the vessel deck. The article also presents exemplary results of analyzes and attempts carried out so far as part of the implementation of the Helimaris project, as well as an approximation of issues related to the verification of tasks set based on real objects, adapted to perform maritime missions. The main aspect of modeling focuses on the assessment of aerodynamic characteristics of a helicopter equipped with an flotation system from point of view failure that can occur during flight and as result flotation system can be symmetric or antisymmetric activate. Maritime modification and nonintentional flotation system activation cause modification of aerodynamic characteristics that have influence on flight mechanics aspect of the static and dynamic stability of the helicopter, as well as to determine the swash plate control margin. The CFD analysis methodology with additional rotor model defined by VBM(Virtual Blade Model) User Define Function algorithms, will allow to determine the impact of disturbances of the active float system on the rotor performance and the possibility to trimming the rotor, also in the vicinity of the vessels deck. Another aspect analyzed based on the Co-Simulation philosophy is the use of CFD algorithms and equations describing helicopter flight mechanics, to assess the impact of aerodynamic disturbances generated by the vessel superstructures on the helicopter rotor during landing approach, including the case of symmetry and asymmetry inflow on to the rotor (taking into account the influence of vessel exhaust gases), as well as describe power and thrust fluctuation related with partially presence of the helicopter rotor above the vessel helideck. Analysis also including different environmental conditions depend on operation zone (for example Baltic Sea, Mediterranean Sea), that define boundary conditions velocity fluctuation. Definition of Turbulence (especially in the landing zone) related to the presence of a vessels that were determined based on tunnel tests and CFD analyzes, has been calculating by the CTO (Ship Design and Research Center), for sea states in accordance with the definition presented in Advisory Circular AC 27.801 (figure 2)
Reduced-order modelling of mineral dust deposition in turboshaft engine hot sections
No full textOperating in brownout conditions is a hazardous yet often unavoidable consequence of using rotorcraft in dry, arid environments. Significant quantities of the lofted dust cloud can be ingested into the helicopters engines where they cause damage in both the main gas path and secondary air systems. Molten particle accumulation on nozzle guide vanes has the potential to restrict the core mass flow and cause the engine to surge. Predicting the conditions under which this happens is complicated by the many separation and sorting processes that occur in the preceding sections of the engine. This contribution demonstrates a reduced-order, probabilistic methodology that can be used in conjunction with in-field particle sampling to predict the extent of nozzle guide vane damage and assess the risk of engine surge when operating in a particular environment. The processing of the raw ingested dust in the compressor and particle separator system is shown to be significant in accurately predicting the extent of damage and suggests that taking particle samples from the bulk dust cloud is likely to provide under-estimations of the actual damage seen in the engine
Interactional structural loads of the XV-15 rotor in airplane mode
Get PDFAn investigation of the rotor/airframe interactions of the XV-15 tiltrotor aircraft in airplane mode is conducted using high fidelity CFD. To separate the rotor installation effects, an isolated rotor and a half-span full aircraft are simulated at the cruise speeds of 160 and 220 knots. The installed rotor displays a doublet aerodynamic loading near the 270o azimuth along with low-frequency mode harmonic airloads in the first half of the cycle. The doublet aerodynamic loading is due to the interactions with the wing and the low-frequency harmonic airloads are due to the rotor dynamics and longitudinal cyclic pitch control. The installed rotor thrust and power display significant 3/rev loading that is typical for a three-bladed rotor. More importantly, the resulting low-frequency mode harmonic airloads trigger vibrations on the rotor as a forcing function. The installed rotor displays significant installation effects on the 2 to 4/rev harmonics of the blade torsional, flap, and lead-lag moments at 220 knots
Multibody model of the flap stop contact dynamics of an articulated rotor
No full textThe paper discusses a multibody aeroelastic model of an articulated main rotor system. The model is developed with the specific aim to capture the main dynamic features characterising flap stop contact conditions and to provide a means to predict the associated loads. A five bladed fully articulated rotor is considered: blades flexibility is accounted for using beam modal representations and the aerodynamics is modelled with a blade element approach. Particular emphasis is given to the definition of the flap stop mechanism structural and geometrical features, by detailing the contact reaction load paths and importing the contact surfaces from verified 3D CAD geometries. The kinematics of collective and cyclic controls is accurately represented considering servo actuators, rotating and fixed swashplates with the respective scissor links, pitch links and pitch horns. Linear blade lag dampers are implemented reproducing the associated experimental operating damping curve. Special attention is addressed to the model validation activities which lead to the achievement of an encouraging level of correlation with experimental data: the findings highlighted in this paper confirm the validity of the methodology adopted and give confidence in its potential for describing the flap stop contact dynamics of fully articulated rotors