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Viewing 241 to 270 of 61861
2011-06-13
Technical Paper
2011-38-0016
Tonja Reinert, Robert J. Flemming, Robert Narducci, Roger J. Aubert
A team from the USA rotorcraft industry, NASA, and academia was established to create a validated high-fidelity computational fluid dynamics (CFD) icing tool for rotorcraft. Previous work showed that an oscillating blade with a periodic variation in angle of attack causes changes in the accreted ice shape and this makes a significant change in the airfoil drag. Although there is extensive data for ice accumulation on a stationary airfoil section, high-quality icing-tunnel data on an oscillating airfoil is scarce for validating the rotorcraft icing problem. In response to this need, a two-dimensional (2D) oscillating airfoil icing test was recently performed in the Icing Research Tunnel at the NASA Glenn Research Center. Three leading-edge specimens for an existing 15-inch chord test apparatus were designed and instrumented to provide the necessary data for the CFD code validation.
2011-06-13
Technical Paper
2011-38-0020
Cory Wolff, Frank Mcdonough, Ben Bernstein
In the continental United States east of the Rocky Mountains cold fronts are quite common in wintertime due to the many cyclones moving through this region, and icing conditions in the vicinity of cold fronts are a major contributor to the overall occurrence of icing in the atmosphere. The conditions examined in this study will be those behind the cold front. Icing there is often found in stratocumulus clouds that form due to destabilization of the boundary layer through cold air advection and an inversion formed by subsidence aloft which caps their growth. Moist adiabatic lapse rates, small drop sizes, high drop concentrations, and moderate to high liquid water contents depending on the cloud depth often characterize these clouds.
2011-06-13
Technical Paper
2011-38-0067
Nathalie Alegre, David Hammond
This study reports aerodynamic properties of two runback ice shapes molded from a mid-span full scale B737 aerofoil leading edge together with a series of simplistic ice shapes of the type sometimes used by aircraft manufacturers to mimic performance loss due to runback ice. The runback ice shapes were taken from a study of runback ice growth which had produced flexible silicone rubber moulds. These moulds were used to produce ice shapes without curvature which, together with the “simplistic” shapes were mounted on flat plates and installed into the Cranfield University 8 by 6 foot wind tunnel. A boundary layer suction system was used to match the wall conditions more closely to what would be anticipated on a real aerofoil. The icing conditions approximate to a hold case with the two shapes representing a 4 and a 10 mm thick runback shape. The aerodynamic tests have been performed with a tunnel speed of 45 m/s.
2011-06-13
Technical Paper
2011-38-0068
Jakob Tendel, Cory Wolff
This study presents an evaluation of in-flight icing severity forecasts produced for the eastern United States for the winter 09/10 using the German ADWICE icing forecasting system. An instance of the underlying COSMO-EU 7km model was run over the eastern CONUS to produce four months worth of NWP data for the ADWICE algorithm. The generated icing fields were then verified using pilot reports (PIREPS) as “truth” data. In order to be able to characterize ADWICE performance over this non-native domain against a known quantity for this part of the world, a comparative verification was performed with the American FIP icing product over 1.5 months of data, using a unified set of observation PIREPS and forecast times. Subsequently, ADWICE forecasts were verified over the whole time period and analyzed with respect to seasonal, regional or altitude variations.
2011-06-13
Technical Paper
2011-38-0069
Daniel R. Adriaansen, Cory Wolff, Frank Mcdonough
The Current Icing Product (CIP) provides an hourly diagnosis of the severity of icing occurring based on multiple data sources. Pilot reports (PIREPs) and surface observations (METARs), as well as satellite, numerical weather prediction (NWP) model, radar, and lightning data are all utilized within the algorithm. The accurate identification of cloud base is a large factor in the algorithm's determination of icing severity. Current methods employ the METAR observation of ceiling to identify the cloud base over a specified area within the CIP domain. The temperature from the Rapid Update Cycle (RUC) NWP model at the height of the observed METAR ceiling can be utilized as a proxy for the amount of condensate in the cloud. The likelihood of a large amount of condensate in the identified cloud increases with increasing cloud base temperature. As the amount of liquid water diagnosed by CIP severity increases, so does the estimated icing severity.
2011-06-13
Technical Paper
2011-38-0070
Ben C. Bernstein, Erik Gregow, Ian Wittmeyer, Jarkko Hirvonen
Concepts from algorithms that use observations and numerical model output to diagnose icing conditions aloft also apply well in the near-surface environment, where icing can affect wind turbines, power lines, communications towers and more. The LOWICE system is being developed to leverage proven in-flight icing knowledge to create real-time assessments of the near-surface icing environment.
2011-06-13
Technical Paper
2011-38-0064
Jafar Alzaili, David Hammond
The objective of this work is to investigate the thin water film characteristics by performing a range of experiments for different icing conditions. Our focus is on the SLD conditions where the droplets are larger and other effects like splashing and re-impingement could occur. Three features for the thin water film have been studied experimentally: the water film velocity, wave celerity and its wavelength. The experiments are performed in the icing facilities at Cranfiled University. The stability of the water film for the different conditions has been studied to find a threshold for transient from continues water film to non-continues form. A new semi-empirical method is introduced to estimate the water film thickness based on the experimental data of water film velocity in combination of theoretical analysis of water film dynamics. The outcome of this work could be implemented in SLD icing simulation but more analysis is needed.
2011-06-13
Technical Paper
2011-38-0065
Andy P. Broeren, Sam Lee, Gautam H. Shah, Patrick C. Murphy
An experimental research effort was begun to develop a database of airplane aerodynamic characteristics with simulated ice accretion over a large range of incidence and sideslip angles. Wind-tunnel testing was performed at the NASA Langley 12-ft Low-Speed Wind Tunnel using a 3.5% scale model of the NASA Langley Generic Transport Model. Aerodynamic data were acquired from a six-component force and moment balance in static-model sweeps from α = -5 to 85 deg. and β = -45 to 45 deg. at a Reynolds number of 0.24x10⁶ and Mach number of 0.06. The 3.5% scale GTM was tested in both the clean configuration and with full-span artificial ice shapes attached to the leading edges of the wing, horizontal and vertical tail. Aerodynamic results for the clean airplane configuration compared favorably with similar experiments carried out on a 5.5% scale GTM.
2011-06-13
Technical Paper
2011-38-0066
Phillip J. Ansell, Michael B. Bragg, Michael F. Kerho
A stall prediction method based on unsteady hinge moment measurements was previously developed from experimental hinge moment measurements on a NACA 3415 airfoil model under a clean configuration and four iced configurations. The stall prediction algorithm was based on three separate detector functions. Additional hinge moment measurements have been obtained experimentally for a NACA 23012 airfoil model, using these same clean and iced configurations. Tests were also conducted with boundary-layer trips on the model upper and lower surfaces. The addition of simulated icing degraded the performance of the NACA 23012. Upon application of the hinge moment stall prediction method, two of the six configurations provided detector function outputs that were inconsistent with the other four configurations. Further investigation revealed differences in the hinge moment signal between contamination configurations due to the presence of different types and extents of primary stall mechanisms.
2011-06-13
Technical Paper
2011-38-0054
Daniel Martins Silva, Luis Gustavo Trapp
In order to correctly predict an aircraft ice accretion, the ice prediction tool shall be capable of predicting the aerodynamic characteristics of both clean and iced airfoil and be able to predict the shape of the ice accreted on both wind tunnel and actual aircraft geometries. This requires the analysis tool to be able to correctly predict the local airflow on aerodynamic surfaces that have large separation regions, as well as local water impingement, freezing, convective cooling and evaporation rates. The capability of different RANS models to predict the aerodynamic degradation of an iced airfoil is evaluated.
2011-06-13
Technical Paper
2011-38-0055
Richard Moser, Roger Gent
The European Union (EU) ‘Clean Sky’ [1] Joint Technology Initiative (JTI) is a research programme aimed at developing breakthrough technologies which will minimise the impact of aviation on the environment. Within this, the System for Green Operations (SGO) Integrated Technology Demonstrator (ITD) looks to improve aircraft operation through management of energy and mission trajectory. As part of the SGO ITD, a series of environmental icing tests have been conducted on an ice protected, acoustically protected, electrically powered, scoop intake and channel. The range of conditions tested included in-flight icing (CS-25 Appendix C, same as 14 CFR 25), super-cooled large droplets (proposed 14 CFR 25 Appendix O, [2]), snow and ice crystal conditions as well as ground icing in freezing fog conditions.
2011-06-13
Technical Paper
2011-38-0051
Jamie Braid, Patrick Van Wie, Jeffrey Rex
Aircraft icing continues to be a challenge for the aviation community. Icing is predominantly reported by pilots based on subjective visual observations of relatively small ice thicknesses at distances greater than such estimates can consistently be made. While some technologies exist to sense the presence of aircraft icing, there is a need to objectively sense the presence of ice, determine the rate of ice accumulation, and concurrently measure weather conditions to support, validate, and report the icing indication. AirDat LLC has developed an airborne atmospheric sensing device that includes a built-in ice detector which transmits icing information directly to the ground in real time. These data can be received directly by the aircraft operator or provided to any number of aviation entities to improve the safety of the National Air Space (NAS).
2011-06-13
Technical Paper
2011-38-0053
John Hallett
An operational definition of a mixed phase environment, as ice and water, from the viewpoint of its role in aircraft icing is approached from a consideration that the physical properties of any accreted mix are necessarily dependent, through the aircraft penetration velocity, on the spatial distribution of such a mix. Aircraft measurement of such an environment depends on a high response (0.1seconds, some10m of flight path) instrument (the T probe) capable of independent measurement of ice and water and thus capable of distinguishing between all water and all ice environments. The physical properties of such a mix are ill understood, yet are critical to their surface flow and ultimate freezing behavior. Such highly resolved measurements are necessary, since although the frequency occurrence of such mixes may be less than ice and water alone, their consequences may be enduring should the aircraft trajectory happen to lie along a frontal or developing hurricane weather system.
2011-06-13
Technical Paper
2011-38-0044
Michael P. Kinzel, Ralph W. Noack, Christian M. Sarofeen, David Boger, Richard Eric Kreeger
In this work, a newly developed iced-aircraft modeling tool is applied to wings, engine inlets, and helicopter rotors. The tool is based on a multiscale-physics, unstructured finite-volume CFD approach and is applicable to general purpose aircraft icing applications. The present approach combines an Eulerian-based droplet-trajectory solver that is loosely coupled, in a time-accurate manner, to a surface-film and ice-evolution model. The goal of the model is to improve the fidelity of ice accretion modeling on dynamic geometries and for three-dimensional ice shapes typical of helicopter rotors. The numerical formulation is discussed and presented alongside 2D and 3D static validation cases, and dynamic helicopter rotors. The present results display good validation for predicting ice shape on a variety of geometries, and a strong initial capability of modeling ice forming on helicopters in forward flight.
2011-06-13
Technical Paper
2011-38-0043
Chao Wang, Shi-nan Chang, Xin-ming Su
Euler method was used in calculating the gas-liquid two-phase flow field. With the help of the user defined function (UDF) in FLUENT software, the water local collection efficiency and ice accretion on three dimensional wings were solved. The flow motion of runback water was divided along the chordwise and spanwise direction respectively during the computation procedure and the classical Messinger model was modified to be applicable to simulate three dimensional ice accretion. The analysis about three dimensional mass and heat transfer was also performed according to the modified Messinger model. Based on the traditional method of calculating heat transfer coefficient on two dimensional surfaces, an improved method was applied to compute the heat transfer coefficient on three dimensional wings. The direction of ice accretion was defined to be normal to the wing surface. The comparative results showed that the three dimensional ice accretion code developed in this paper was effective.
2011-06-13
Technical Paper
2011-38-0034
Michael Papadakis, Alonso O. Zamora Rodriguez, Rodrigo Hoffmann Domingos
Results from a two-dimensional computer model developed at Wichita State University (WSU) for bleed air system analysis are compared with experimental data from icing tunnel tests performed with a wing model equipped with a hot air ice protection system. The computer model combines a commercial Navier-Stokes flow solver with a steady-state thermodynamic analysis model that applies internal flow heat transfer correlations to compute wing leading edge skin temperatures and the location and extent of the runback ice. The icing tunnel data used in the validation of the computer model were obtained at the NASA Icing Research Tunnel using representative in-flight icing conditions and a range of bleed air system mass flows and hot air temperatures. Correlation between experiment and analysis was good for most of the test cases used to assess the performance of the simulation model.
2011-09-11
Technical Paper
2011-24-0029
Julien Bohbot, Yohan Blacodon, Bruno Scheurer
The numerical simulation of internal aerodynamic of automotive combustion chamber is characterised by complex displacements of moving elements (piston, intake/exhaust valves…) and by a strong variation of volume that cause some problems with classical numerical based mesh methods. With those methods (FEM, FVM) which use geometric polyhedral elements (hexaedron, tetrahedron, prismes…), it is necessary to change periodically the mesh to adapt the grid to the new geometry. This step of remeshing is very fastidious and costly in term of engineer time and may reduce the precision of calculation by numerical dissipation during the interpolation process of the variables from one mesh to another. Recently, the researcher community has renewed his interest for the development of a generation of numerical to circumvent the drawbacks of the classical methods.
2011-10-18
Technical Paper
2011-01-2770
Lejun Chen PhD, Ronald Patton
This work is motivated through a research study ADDSAFE funded by the European Commission, following an interest in implementing mixed linear parameter varying (LPV) H_/H✓ model-based fault detection and diagnosis (FDD) methodology for detecting nonlinear actuator faults for flight control system. The main design goal is to maximize the robustness of the residual signal to uncertainty and disturbances whilst also achieving the specific minimum sensitivity of the residual signal to faults. The specific minimum sensitivity index used is based on the H_ index concept and is extended to the LPV FDD system problem. This allows the fault signature for multiple sensor and actuator faults to be reconstructed simultaneously, facilitating the robust isolation of faults rather than just their detection.
2011-10-18
Technical Paper
2011-01-2769
Georges Hardier, Cédric seren, Pierre Ezerzere
The introduction of Fly-By-Wire (FBW) and the increasing level of automation contribute to improve the safety of civil aircraft significantly. These technological steps permit the development of advanced capabilities for detecting, protecting and optimizing A/C guidance and control. Accordingly, this higher complexity requires extending the availability of aircraft states, some flight parameters becoming key parameters to ensure a good behaviour of the flight control systems. Consequently, the monitoring and consolidation of these signals appear as major issues to achieve the expected autonomy. Two different alternatives occur to get this result. The usual solution consists in introducing many functionally redundant elements (sensors) to enlarge the way the key parameters are measured. This solution corresponds to the classical hardware redundancy, but penalizes the overall system performance in terms of weight, power consumption, space requirements, and extra maintenance needs.
2011-10-18
Technical Paper
2011-01-2805
Maxime Lastera, Eric Alata, Jean Arlat, Yves Deswarte, David Powell, Bertrand Leconte, Cristina Simache
Traditionally, software in avionics has been totally separated from open-world software, in order to avoid any interaction that could corrupt critical on-board systems. However, new aircraft generations need more interaction with off-board systems to offer extended services, which makes these information flows potentially dangerous. In a previous work, we have proposed the use of virtualization to ensure dependability of critical applications despite bidirectional communication between critical on-board systems and untrusted off-board systems. We have developed a test bed to assess the performance impact induced by the use of virtualization. In this work, various configurations have been experimented that range from a basic machine without an OS up to the complete architecture featuring a hypervisor and an OS running in a virtual machine. Several tests (computation, memory, network) are carried out, and timing measures are collected on different hypervisors.
2011-10-18
Technical Paper
2011-01-2711
Marc Boyer, Jorn Migge, Marc Fumey
Avionics systems distributed on AFDX networks are subject to stringent real-time constraints that require the system designer to have techniques and tools to guarantee the worst case traversal time of the network (WCTT) and thus ensure a correct global real-time behavior of the distributed applications/functions. The network calculus is an active research area based on the (min,+) algebra, that has been developed to compute such guaranteed bounds. There already exists several academics implementations but no up to date industrial implementation. To address this need, the PEGASE project gathers academics and industrial partners to provide a high quality, efficient and safe tool for the design of avionic networks using worst case performance guarantees. The PEGASE software is an up-to-date software in the sense that it integrates the latest results of the theories, in tight cooperation with academics researchers.
2011-10-18
Technical Paper
2011-01-2713
Felix Jakob, Silvia Mazzini, Andreas Jung
This paper describes an approach for a SysML-based methodology, recently defined and applied at the European Space Agency (ESA). In 2009 a SysML-based methodology based on the European Cooperation for Space Standardization (ECSS) and International Organization for Standardization (ISO) standards was developed in the frame of the European Space Agency (ESA)/European Space Research and Technology Centre (ESTEC) study “System and Software Functional Requirements Techniques” (SSFRT).The SSFRT study investigated the feasibility of the application of model-based system engineering in spacecraft design to support the space system and software development processes, from mission level requirements to software implementation. The use of models to support the system requirements engineering process was aimed at improving the system requirements allocation process toward the software requirements engineering process.
2011-10-18
Technical Paper
2011-01-2718
Benjamin Knoblauch, Patricia Best, Vijay Ragothaman, Ravi Pendse
While most industries have already adopted the use of IP networks to exploit the many advantages of network connectivity, the aircraft industry still has not significantly deployed networked devices in the aircraft. Security and reliability are two main concerns that have slowed the transition to this technology. The ability for Air Traffic Control to send digital communications to aircraft could significantly improve the aircraft safety by improving the speed and efficiency of communications. In addition, if devices could offload flight data to servers on the ground for analysis, the accuracy and efficiency of maintenance and other decisions impacting the aircraft could significantly improve. The purpose of this research is to propose an IP-based LAN architecture for the aircraft which provides a scalable solution without jeopardizing flight safety.
2011-10-18
Technical Paper
2011-01-2717
Gernot Ladstaetter, Nicolas Reichert, Thomas Obert
Over the last few years, IT systems have quickly found their way onboard aircrafts, driven by the continuous pursuit of improved safety and efficiency in aircraft operation, but also in an attempt to provide the ultimate in-flight experience for passengers. Along with IT systems and communication links came IT security as a new factor in the equation when evaluating and monitoring the operational risk that needs to be managed during the operation of the aircraft. This is mainly due to the fact that security deficiencies can cause services to be unavailable, or even worse, to be exploited by intentional attacks or inadvertent actions. Aircraft manufacturers needed to develop new processes and had to get organized accordingly in order to efficiently and effectively address these new risks.
2011-10-04
Technical Paper
2011-36-0256
Sérgio Roberto Ferreira Machado, Marcelo de Oliveira e Souza
Avionics Systems are increasingly used to perform safety-critical functions at high altitudes. But their increasing capacity and concentration of memory and logics leads to more frequent occurrences of single event upsets, especially in high altitudes. In this work we discuss the effects and mitigation of single event upsets on avionics systems to help in developing future requirements. To do that we initially present the concepts of radiation environment of the atmosphere, radiation induced errors, single event upsets, etc. Then, we discuss some of their effects on avionic systems and ways of mitigation. Finally, we discuss provisions to demand the adoption of such mitigation measures, and their sufficiency. This will help in developing future requirements to accomplish the objectives of a safe operation of civil transportation aircraft.
2011-10-04
Technical Paper
2011-36-0179
Eloy Martins de Oliveira Junior, Marcelo Lopes de Oliveira e Souza
Current systems such as satellites, aircrafts, automobiles, turbines, wind power generators and traffic controls are becoming increasingly complex and/or highly integrated as prescribed by the SAE-ARP-4754 Standard. Such systems frequently require accurate generation, distribution and time or phase synchronization of signals with different frequencies that may be based on one reference signal and frequency. But the environment fluctuations or the non-linear dynamics of these operations cause uncertainties (skew and jitter) in the phase or time of the reference signal and its derived signals. So, techniques to reduce those causes or their effects are becoming important aspects to consider in the design of such systems. The PLL techniques are useful for establishing coherent phase or time references, jitter reduction, skew suppression, frequency synthesis, and clock recovery in numerous systems such as communication, wireless systems, digital circuits, rotors, and others.
2011-10-04
Technical Paper
2011-36-0182
Gitsuzo B. S. Tagawa, Marcelo L. O. Souza
The use of control architectures with the Integrated Modular Avionics (IMA) concept (“IMA architectures”) in aerospace and the Integrated Modular Electronics (IME) concept (“IME architectures”) in automotive applications is growing due to its reduced number of hardware such as processors, Line Replaceable Units (LRUs) and Electronic Control Units (ECUs), thereby reducing weight and costs. Furthermore, IMA architectures can perform complex reconfigurations in the case of failures and adapt themselves to changes in network functioning or operating modes, which make a control system very robust. The objective of this work is to discuss the use of an IMA architecture to simulate an aerospace control system responsible for maintaining a vehicle in a predetermined trajectory. To do that, we review the current literature related to IMA architectures and give an overview of their characteristics. Then, we choose an aerospace control system and discuss its simulation using an IMA platform.
2011-10-04
Technical Paper
2011-36-0187
Jairo Cavalcanti Amaral, Marcelo Lopes de Oliveira e Souza
Many control systems switch between control modes according to necessity. That is often simpler than designing a full control to all situations. However, this creates new problems, as determining the composed system stability and the transient during switching. The latter, while temporary, may introduce overshooting that degrade performance and damage the plant. This is particularly true for the MultiMission Platform (MMP), a generic service module currently under design at INPE. Its control system can be switched among nine main Modes of Operation and other submodes, according to ground command or information coming from the control system, mainly alarms. It can acquire one and three axis stabilization in generic attitudes, with actuators including magnetotorquers, thrusters and reaction wheels.
2011-10-04
Technical Paper
2011-36-0216
Alessandro Gonçalves Adinolfi, Marcelo Lopes de Oliveira e Souza
The increasing use of Global Navigation Satellite Systems-GNSS in future Aeronautical Navigation Systems-ANS is a current trend in the aeronautical operation and regulation communities. This trend implies the adoption of elements and interactions of a degree of complexity that is still being discussed around the world. Faced with that, we believe that a requirements based approach is an effective tool to deal with such highly complex and integrated systems. In this work we discuss a requirements based approach to future Aeronautical Navigation Systems based on Global Navigation Satellite Systems. To do that, we first briefly present the concept of Communication, Navigation, Surveillance/Air Traffic Management - CNS/ATM, and the current and potential benefits of the adoption of its paradigms.
2011-11-08
Technical Paper
2011-32-0601
Cary W. Wilson, Frederick R. Schauer, Paul J. Litke, John L. Hoke, Jon-Russell J. Groenewegen
Many of the engines used in Remotely Piloted Aircraft (RPA), come directly from the remote-control (R/C) aircraft market, which turn a propeller but are not necessarily built for the greatest efficiency or reduced fuel consumption. The DoD “single fuel concept” is pushing these platforms to be able to operate with JP-8 using an Otto Cycle engine. Additionally, with increased environmental concern with fossil fuels, possible future DoD requirements could require the use of bio-derived liquid fuels. The research presented in this paper takes steps to satisfying both the efficiency and single fuel requirements. The Fuji BF-34EI engine was successfully shown to operate effectively with JP-8, Diesel, Algae-based Diesel and Camelina based Hydroprocessed Renewable Jet fuel. When generally compared over the entire engine operating map, between AVGAS and JP-8, the latter is shown to present a 10-20% lower brake specific fuel consumption (BSFC).
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