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Viewing 211 to 240 of 61883
1999-10-19
Technical Paper
1999-01-5554
Darrell Fernald, Preston Shultz
Airline aircraft maintenance and ground support services meet at the connection points for ground service. Ground power must be applied to the aircraft, but responsibility for the aircraft receptacle falls to aircraft maintenance. This responsibility gap is not currently being addressed by the industry. For years any difficulty in applying power to an aircraft on the ground has been blamed solely on the ground power cable or generator. Any potential problems with the receptacles was largely ignored by ground service personnel, since they are not allowed to touch the aircraft. No one thought to look closely at the receptacle as a potential source of the inability to reliably apply power to the aircraft (in fact, routine maintenance A,B,C or D maintenance did not routinely check or change the receptacle).
1999-10-19
Technical Paper
1999-01-5555
Matthew C. Tracy, Paul McTaggart
The Air Force Research Laboratory Deployment and Sustainment Division (AFRL/HES), in coordination with Arthur D. Little, Inc., has undertaken a system-of-systems approach to defining and designing aerospace ground equipment (AGE). This method is usually used to take advantage of the open architecture nature of ne and developing electronics through modular design. This paper discusses how we applied it across the electronic, mechanical, and structural aspects of AGE to research and develop a new concept to meet the burgeoning needs of the 21st century Air Force.
1999-10-19
Technical Paper
1999-01-5551
Michael Vujcich, Terry Scharton
Combining the quasi-static loads, workmanship verification, and model validation tests of aerospace hardware into a single vibration test sequence can considerably reduce schedule and cost. The enabling factor in the implementation of the combined dynamic testing approach is the measurement of the dynamic forces exerted on the test item by the shaker. The dynamic testing of the QuikSCAT spacecraft is discussed as an example of a successful combined loads, workmanship, and model validation test program.
1999-10-19
Technical Paper
1999-01-5546
Archie E. Dillard
The rapid implementation of multifunction display (MFD) designs in new aircraft has increased the need for aerospace recommended practices (ARP) for use by manufacturers and users. The large amount of information available for display creates a number of human factors problems that must be addressed in the design phase in order to produce a safe and usable display system. Color, clutter, prioritization, switching, symbology, and compatibility are only a few of the areas that require guidance. This presentation will review the work to date by the SAE G-10 Multifunction Display Subcommittee on an ARP that will address these issues and others.
1999-10-19
Technical Paper
1999-01-5550
Daniel Anthony, Terry Scharton, Albert Leccese
A novel direct acoustic test was performed on the Quik- SCAT spacecraft at Ball Aerospace Technology Corporation (BATC) in Boulder, Colorado, in October 1998. The QuikSCAT spacecraft was designed and built by BATC in an accelerated, one-year, program managed by the NASA Goddard Space Flight Center. The spacecraft carries the SeaWinds scatterometer developed by the Jet Propulsion Laboratory to measure the near-surface wind speed over Earth’s oceans. Instead of conducting the acoustic test with the spacecraft in a reverberant room, as is the usual practice, the test was conducted with the spacecraft mounted on a shaker slip-table in a nearly anechoic, vibration test cell. The spacecraft was surrounded with a three-meter high ring of large, electro-dynamic speakers, spaced approximately 1.3 meters away from the two-meter diameter, 900 kg. spacecraft. The thirty-one speaker cabinets were driven with 40,000 rms watts of audio amplifier power.
1999-10-19
Technical Paper
1999-01-5520
Mark S. Grahne, David P. Cadogan
The planned increase in satellite launches over the next decade will emphasize reduction of space hardware mass and launch costs. Inflatable structures present many benefits over current state-of-the-art +mechanical technologies and are principally attractive because they can be packaged into small volumes, thereby reducing program costs. Reduced costs are realized in development and production as well as in enabling smaller launch vehicle size. Inflatable structures will reduce total system mass and complexity, thereby increasing system reliability. This paper describes several types of inflatable structures and applications being developed for space flight. Rigidization methods and results from preflight test programs are also presented to support the viability of the technology.
1999-10-19
Technical Paper
1999-01-5515
James L. Hunt, Robert J. Pegg, Dennis H. Petley
This paper presents the status of the airbreathing hypersonic airplane and space-access vision-operational-vehicle design matrix, with emphasis on horizontal takeoff and landing systems being studied at Langley; it reflects the synergies and issues, and indicates the thrust of the effort to resolve the design matrix including Mach 5 to 10 airplanes with global-reach potential, pop-up and dual-role transatmospheric vehicles and airbreathing launch systems. The convergence of several critical systems/technologies across the vehicle matrix is indicated. This is particularly true for the low speed propulsion system for large unassisted horizontal takeoff vehicles which favor turbines and/or perhaps pulse detonation engines that do not require LOX which imposes loading concerns and mission flexibility restraints.
1999-10-19
Technical Paper
1999-01-5514
Mark J. Lewis
Hypersonic flight vehicles, capable of flight in excess of five times the speed of sound, can be categorized into two basic types: blunt, high drag shapes, and sharp, low drag forms. Though the majority of hypersonic flight experience is invested in blunt geometries for spacecraft reentry, sharp high-speed aerodynamic shaped can be applied to a wide range of missions, including missiles, cruisers, accelerators, and maneuvering space vehicles. The techniques for designing this class of vehicle, and the limiting technologies, will be described. Several upcoming programs, most notably the NASA Ames SHARP flight tests, will demonstrate some of the key aerodynamic and materials technologies that will enable the practical development of high-lift, low drag hypersonic vehicles. The NASA Glenn Trailblazer vehicle is also described as an opportunity to apply these technologies on a promising access-to-space vehicle.
1999-10-19
Technical Paper
1999-01-5512
Leger, Aymeric, H. Audrezet, P. Alba
HUD-based hybrid landing systems developed by SEXTANT Avionics have been successfully certified for AEROPOSTALE and ALITALIA. The philosophy of such system is to offer minima reductions (down to DH 35 ft and RVR 125 m) with automatic Cat 3A operations. From a human factors stand point, the basis of such an approach is that improved situational awareness provided by the HUD allows to maintain an acceptable safety level for operations despite lower DH and visibility. Though, it is well known that switching from a supervisory control mode to a manual control mode under time pressure is a very serious challenge for the human operator. In this regard, numerous human factors issues were addressed during the concept validation phase and results applied to certification.
1999-10-19
Technical Paper
1999-01-5531
Christopher McFarland, Jason McClurg, William McClelland, Steven A. Brandt
The General Atomics RQ-1A Predator has become an essential tool for battlefield commanders. However, its low maximum speed and poor performance in rain and icing conditions limit its usefulness. In the Spring of 1999, two 10-student sections of the aircraft design class at the United States Air Force Academy studied ways to improve Predator’s usefulness. They determined that small turbine engines, electro-expulsive de-icing systems, and several simple aerodynamic refinements would significantly improve Predator’s capabilities. These results and the methods used to generate them are described.
1999-10-19
Technical Paper
1999-01-5530
Ray Whitford
Different feasibility studies have been carried out over several years at the Royal Military College of Science (RMCS) into medium military airlifters aimed, in essence at replacing the C-130. The studies, each occupying a nominal 1,500 manhours (but probably 50% more) formed part of the final year of the AeroMechanical B.Eng degree at RMCS. The intention of this paper is to draw together their major findings and deals predominantly with the topics of: cargo hold sizing and body aerodynamics, powerplant selection, weight and performance.
1999-10-19
Technical Paper
1999-01-5524
Andrzej Tomczyk, Jan Gruszecki
The autonomous control of an aircraft under the flare and touch-down maneuvers is an interesting problem of both theoretical and practical nature. In this paper, a concept of the autonomous landing system (ALS) for unmanned air vehicles (UAV) is presented. The flight control system is addressed to the low-cost, civilian, medium-size UAV with relatively low approach speed and typical nose-wheel landing gear. Final approach is executed automatically using differential GPS guidance system. When the flight control system selects the LANDING option at chosen altitude (based on GPS and pressure altitude), a change in aircraft’s attitude is executed. New attitude ensures safe flare and touchdown of the unmanned aircraft. Flight control system is based on the model-following design technique. Two kinds of flight control systems are taken into consideration.
1999-10-19
Technical Paper
1999-01-5507
Margaret-Anne Mackintosh, Sandra Lozito, Alison McGann, Elizabeth Logsdon
This research focused on identifying communication strategies and procedures related to efficient and error-resistant data link communication. A coding scheme was developed that identified five steps in the data link communication cycle in which information may need to be transmitted between operators. This methodology was applied to a data link full mission study with 10 flight crews as participants. Initial results indicated that the amount of information transferred may impact communication timing and efficiency. The impact of data link upon the roles and procedures of the crewmembers is discussed.
1999-10-19
Technical Paper
1999-01-5510
Michael T. Chan
To make speech recognition a viable input modality in the cockpit, we propose to include visual speech input to improve robustness of the approach in the presence of noise. The visual speech interface includes a headmounted lip imaging apparatus and algorithms to recognize spoken words visually. Our algorithms are based on a few components which address all issues related to lip localization, lip shape model extraction, tracking, feature extraction and recognition. We demonstrate the practicability of the concept with a visual speech recognizer for a discrete-word recognition task that is relatively simple but achievable in real time.
1999-10-19
Technical Paper
1999-01-5503
John Paterson
Survivability of combat aircraft has significantly increased with the use of low observable (LO) technology. This technology has dramatically reduced the ability of an air defense to detect, track, intercept and destroy a penetrating stealth aircraft. The Iraqi Desert Storm conflict demonstrated to the world that LO aircraft are a significant threat and they are developing counters to that threat. Many countries are rapidly improving their air defenses by purchasing more advanced radars, surface-to-air missiles (SAM) and integrated air defense systems (IADS). Another defense technique is to concentrate defense elements so there is significant overlap, making it difficult for even stealth aircraft to penetrate. A counter to these defense improvements and highly defended areas is already being used by non-stealth aircraft: standoff weapons. Stealth aircraft can penetrate a hostile airspace and use standoff weapons to attack heavily defended areas with little survivability risk.
1999-10-19
Technical Paper
1999-01-5506
Thomas R. Yechout, Jonathan C. Dowty
Approximately 120 hours of wind tunnel testing were accomplished to determine the drag contributions of various external protuberances on the AC-130H Gunship and to recommend modifications to achieve optimal drag reduction potential. Also, the operational impact of the recommended configuration was quantified using a performance modeling code. The overall objective of this effort was to establish a solid foundation via experimental and computational ground efforts to support flight test of drag reduction modifications to an aircraft. Thirteen basic AC-130H protuberances were evaluated to determine their incremental drag. A recommended reduced-drag configuration was developed which provided a drag reduction potential of 58.2 counts.
2011-09-11
Technical Paper
2011-24-0218
Mikael Karlsson, Mats Abom, Ragnar Glav
The inclusion of flow-acoustic interaction effects in linear acoustic multiport models has been studied. It is shown, using a T-junction as illustration example, that as long the acoustic system is linear the required information is included in a scattering matrix obtained by experimental or numerical studies. Assuming small Mach numbers and low frequencies-as in most automotive silencer applications-the scattering matrix for the T-junction can be approximated using quasi-steady models. Models are derived that holds for all possible configurations of grazing and bias flow in the T-junctions. The derived models are then used to predict the performance of a novel silencer concept, where a resonator is formed by acoustically short-circuiting the inlet and outlet ducts of a flow reversal chamber. The agreement between experiments and simulations is excellent, justifying the use of the quasi-steady modeling approach.
2011-10-04
Technical Paper
2011-36-0088
Jairo Eduardo Moraes Siqueira, Marcelo Lopes de Oliveira e Souza
In this work, the problem of fault detection, isolation, and reconfiguration (FDIR) for Networked-Control Systems (NCS) of aerospace vehicles is discussed. The concept of fault-tolerance is introduced from a generic structure, and a review on quantitative and qualitative methods (state estimation, parameter estimation, parity space, statistic testing, neural networks, etc.) for FDIR is then performed. Afterwards, the use of networks as loop-closing elements is introduced, followed by a discussion on advantages (flexibility, energy demand, etc.) and challenges (networks effects on performance, closed-loop fault-effects on safety, etc.) represented thereby. Finally, examples of applications on aerospace vehicles illustrate the importance of the discussion herein exposed.
2011-10-04
Technical Paper
2011-36-0129
Luiz Carlos Sandoval Góes, Eduardo Augusto Gallo
It was purposed in this study the use of thermal comfort index as feedback parameter for multivariable control of aeronautical air conditioned system. Simulating the developed thermal model, the efficiency gain by using this control law was observed by comparing it with standard control models.
2011-06-13
Technical Paper
2011-38-0001
Jie Xiao, Katherine E. Mackie, Joseph H. Osborne, Jill Seebergh, Santanu Chaudhuri
In-flight icing occurs when supercooled water droplets suspended in the atmosphere impinge on cold aircraft surfaces. Thin layers of accreted ice significantly increase aerodynamic drag while thick layers of ice severely alter the aerodynamics of control surfaces and lift. Chunks of ice can break away from the airframe and cowlings and be ingested into engines causing considerable damage. Developing durable surfaces that prevent the nucleation of supercooled water or reduce ice adhesion to a point where airstream shear forces can remove it would allow the design of a more robust, energy efficient deicing/anti-icing system for aircraft and other applications. In this work, a simulations based framework is developed to predict anti-icing performance of various nanocomposite coatings under the in-flight environment.
2011-06-13
Technical Paper
2011-38-0013
Marco Fossati, Wagdi G. Habashi, Guido Baruzzi
The high computational cost of 3-D viscous turbulent aero-icing simulations is one of the main limitations to address in order to more extensively use computational fluid dynamics to explore the wide variety of icing conditions to be tested before achieving aircraft airworthiness. In an attempt to overcome the computational burden of these simulations, a Reduced Order Modeling (ROM) approach, based on Proper Orthogonal Decomposition (POD) and Kriging interpolation techniques, is applied to the computation of the impingement pattern of supercooled large droplets (SLD) on aircraft. Relying on a suitable database of high fidelity full-order simulations, the ROM approach provides a lower-order approximation of the system in terms of a linear combination of appropriate functions. The accuracy of the resulting surrogate solution is successfully compared to experimental and CFD results for sample 2-D problems and then extended to a typical 3-D case.
2011-06-13
Technical Paper
2011-38-0015
Robert Narducci, Tonja Reinert
The desire to operate rotorcraft in icing conditions has renewed the interest in developing high-fidelity analysis methods to predict ice accumulation and the ensuing rotor performance degradation. A subset of providing solutions for rotorcraft icing problems is predicting two-dimensional ice accumulation on rotor airfoils. While much has been done to predict ice for fixed-wing airfoil sections, the rotorcraft problem has two additional challenges: first, rotor airfoils tend to experience flows in higher Mach number regimes, often creating glaze ice which is harder to predict; second, rotor airfoils oscillate in pitch to produce balance across the rotor disk. A methodology and validation test cases are presented to solve the rotor airfoil problem as an important step to solving the larger rotorcraft icing problem. The process couples Navier-Stokes CFD analysis with the ice accretion analysis code, LEWICE3D.
2011-06-13
Technical Paper
2011-38-0014
Jason Wright, Roger J. Aubert
As part of icing certification flight test programs, artificial ice shapes are typically installed onto aircraft fixed leading edges in order to quantify changes to the handling qualities and performance characteristics of the aircraft in icing conditions. Artificial ice shapes allow a test team to evaluate what are generally the worst combinations of flight conditions for different ice protection system configurations. The goal of this paper is to discuss the details behind the design, development, construction, and installation of artificial ice shapes as they pertained to the evaluation of the need for horizontal stabilizer ice protection on the BA609 Tiltrotor with a focus on the extrapolation methods used to design the shapes.
2011-06-13
Technical Paper
2011-38-0005
Jason Mickey, Eric Loth, Colin Bidwell
A new technique is proposed for computing particle concentrations and fluxes with Lagrangian trajectories. This method calculates particle concentrations based on the volume of a parcel element, or cloud, at the flux plane compared against the initial volume and is referred to as the Lagrangian Parcel Volume (LPV) method. This method combines the steady-state accuracy of area-based methods with the unsteady capabilities of bin-based methods. The LPV method results for one-dimensional (1D) unsteady flows and linear two-dimensional (2D) steady flows show that a quadrilateral element shape composed of a single parcel (with four edge particles) is capable of accurately predicting particle concentrations. However, nonlinear 2D flows can lead to concave or crossed quadrilaterals which produce significant numerical errors.
2011-06-13
Technical Paper
2011-38-0004
Peng Ke, Xinxin Wang
Lagrangian approach has been widely adopted in the droplet impingement analysis for aircraft icing simulation. Some improvements were proposed, including: 1) The heat and mass transfer consideration in droplet dynamics; 2) More efficient droplet localization method, which could and facilitated to find the initial cell in Eulerian grid; 3) New computation method of impingement efficiency, which uses the cover ratio to transform the impingement efficiency of arbitrary impinged region to that of the cell element of body surface and avoids the iterative computation to find the trajectories reaching the corner of the panel or cell element. A numerical solver was built and integrated with the capabilities to deal with super-cooled large droplet (SLD) conditions by considering the splashing and bouncing of SLD. The computational results were validated with the experiment data, which shown good agreements in the impingement limitations and tendency.
2011-06-13
Technical Paper
2011-38-0006
Robert J. Flemming, Philip Alldridge
Sikorsky Aircraft certificated the Model S-92A™ helicopter for flight in icing conditions in 2005. Since that time, the aircraft has flown in icing conditions throughout the world and the approval to launch a flight when icing conditions are forecast or reported has been valuable to operators. However, when the rotor ice protection system was inoperative due to a system failure, use of the aircraft on days of forecast icing was prohibited. Sikorsky Aircraft, therefore, elected to obtain certification of the S-92A helicopter to an EASA limited icing Special Condition so that UK and Norwegian operators in the North Sea sector could complete a mission when icing conditions were forecast, should the RIPS be inoperative on that day. A review of previously available icing data indicated that the S-92A helicopter could meet the requirements of the EASA Special Condition, but that additional flights were required to demonstrate full compliance.
2011-06-13
Technical Paper
2011-38-0022
Marco Fossati, Rooh-ul-Amin Khurram, Wagdi G. Habashi
The irregular shapes that glaze ice may grow into while accreting over the surface of an aircraft represent a major difficulty in the numerical simulation of long periods of in-flight icing. In the framework of Arbitrary Lagrangian-Eulerian (ALE) formulations, a mesh movement scheme is presented, in which frame and elasticity analogies are loosely coupled. The resulting deformed mesh preserves the quality of elements, especially in the near-wall region, where accurate prediction of heat flux and shear stresses are required. The proposed scheme handles mesh movement in a computationally efficient manner by localizing the mesh deformation. Numerical results of ice shapes and the corresponding aerodynamic coefficients are compared with the experimental results.
2011-06-13
Technical Paper
2011-38-0021
Ben C. Bernstein, Frank Mcdonough, Cory Wolff
A large database is being created from icing flight programs completed by aircraft manufacturers for certification and by the NASA-Glenn Research Center for basic research. Although not yet complete, this database already provides an excellent opportunity to study aircraft icing conditions sampled in a wide variety of environments across eastern Canada and most of the United States, including Alaska. In this study, the focus is a comparison of conditions found within boundary-layer stratocumulus icing clouds over the Great Lakes, Pacific Northwest and Alaskan Interior. The clouds will be characterized in terms of temperature, liquid water content, median volumetric diameter, and drop concentration. Critical factors driving these parameters will be discussed.
2011-06-13
Technical Paper
2011-38-0024
Isik A. Ozcer, Guido S. Baruzzi, Thomas Reid, Wagdi G. Habashi, Marco Fossati, Giulio Croce
Numerically predicted roughness distributions obtained in in-flight icing simulations with a beading model are used in a quasi-steady manner to compute ice shapes. This approach, called "Multishot," uses a number of steady flow and droplet solutions for computing short intervals (shots) of the total ice accretion time. The iced geometry, the grid, and the surface roughness distribution are updated after each shot, producing a better match with the unsteady ice accretion phenomena. Comparisons to multishot results with uniform roughness show that the evolution of the surface roughness distribution has a strong influence on the final ice shape. The ice horns that form are longer and thinner compared to constant roughness results. The constant roughness approach usually fails to capture the formation of the pressure side horns and under-predicts the thickness of the ice in this region.
2011-06-13
Technical Paper
2011-38-0023
Guilherme Araujo Lima da Silva, Marcos Noboru Arima, Natashe Nicoli Branco, Marcos de Mattos Pimenta
This paper proposes wall function models to simulate the heat transfer around a cylinder in cross flow with an isothermal and rough surface. The selected case has similitudes with aircraft wing icing: the ice roughness shape, height and distribution. Moreover, the flow is somewhat similar to that found on iced airfoil; and the surface is isothermal like when icing. The Reynolds-Averaged Navier-Stokes, turbulence, energy and mass conservation 7-equation system is solved by two Computational Fluid Dynamics (CFD) codes. To represent accurately the effects of roughness on the heat transfer, the present authors had to modify both codes and to propose new thermal wall functions for them. In addition, it was implemented a momentum wall function that is not so common in CFD codes but it is a standard in aircraft icing simulation.
Viewing 211 to 240 of 61883

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