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At least 1,171 records · Page 65

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NASA NTRS1981

An overview of general aviation propulsion research programs at NASA-Lewis Research Center

This paper presents a brief overview and technical highlights of general aviation (g/a) propulsion research efforts and studies which have been underway at NASA's Lewis Research Center (LeRC) for the past several years. The review covers near-term improvements for current-type piston engines, as well as studies and limited corroborative research on several advanced g/a engine concepts, including diesels, small turboprops and both piston and rotary stratified-charge engines. Also described is basic combustion research, cycle modeling and diagnostic instrumentation work that will be required to make the new engines a reality. The discussion emphasizes the most recently-completed studies and the basic underlying research work, which have not been reported previously.

Willis, E. A.↗

NASA NTRS1981

Flight test evaluation of advanced symbology for general aviation approach to landing displays

This paper describes a set of flight test experiments which were designed to evaluate the relative utility of candidate displays with advanced symbology for General Aviation IFR operations in the terminal area. This symbology was previously evaluated as part of the NASA Langley Research Center's Terminal Configured Vehicle Program for use in commercial airlines. The advanced symbology included vehicle track-angle, flight path angle and a perspective representation of the runway. These symbols were selectively drawn on a CRT display along with the roll attitude, pitch attitude, localizer-deviation and glideslope deviation. In addition to the CRT display, the instrument panel contained standard turn and bank, altimeter, rate of climb, airspeed, heading and engine instruments. The symbology was evaluated using tracking performance and pilot subjective ratings for an ILS capture and tracking task.

Downing, D. R.↗

NASA NTRS1981

Space-time spectral structure of a GLAS general circulation model and a comparison with observations

The wavenumber-frequency spectra of geopotential height computed from a winter simulation of a general circulation model are compared with the observed winter spectra averaged over 15 winters. The space and time scales studied include: (1) stationary planetary waves; (2) stationary synoptic-scale waves; (3) low-frequency planetary waves; (4) low frequency synoptic-scale waves; (5) medium-frequency planetary waves; and (6) medium frequency synoptic-scale waves. Variances in these categories are presented and their distributions with latitude and height are discussed.

Straus, D. M.↗

NASA NTRS1981

The design and development of a mixer compound exhaust system for a quiet clean general aviation turbofan

Lower engine fuel consumption has become a dominant factor in turbofan engine design due to rapidly increasing fuel costs. One engine component with a large impact on engine performance is the exhaust system. Previous exhaust system studies have demonstrated the significant exhaust system efficiency gains available through mixing of the core and bypass flows. Typically, a large, costly rig and engine program are required to develop and optimize these gains. The purpose of this paper is to present the results of the low-cost design system used for the quiet, clean general aviation turbofan mixer nozzle design and development. The scale model and full-scale engine test results confirm the predicted 3 to 5% reduction in cruise fuel consumption. This unique design system, which is based on integrating advanced three-dimensional viscous numerical methods with empirical optimization techniques, is summarized and detailed comparisons with test data are presented. The ability to accurately predict relative performance of mixer systems with substantially reduced development time and cost savings is demonstrated.

Blackmore, W. L.↗

NASA NTRS1981

Correct generalized solar radiation pressure force on a circular cylinder in an arbitrary orientation

In response to the inconsistency seen in Geogevic (1973) with respect to the solution for solar radiation pressure in the case of a circular cylinder, a succinct derivation of the correct solution is presented. Numerical comparisons of the two sets of results confirm that the new formulation yields physically reasonable results for both general and special cases. A detailed graphic representation of the mathematical model used is included.

Tang, C. C. H.↗

NASA NTRS1981

An objective method for determining the generalized transport tensor for two-dimensional Eulerian models

An objective method for deriving the components of a generalized transport tensor for a two-dimensional model is presented. Representative meridional and vertical velocities and thermodynamic scalars at a uniform grid are used to reduce the problem to the solution of two flux equations for two unknowns. One unknown is the stream-function, coefficient of an antisymmetric tensor, which corrects the Eulerian mean motions for Stokes drift; the other is a time constant, which converts the deviatory velocity tensor to a symmetric transport tensor. The complete asymmetric tensor, called a transport tensor, has a divergence which yields both advection and diffusion by the deviatory velocities. Advantages and disadvantages of Lagrangian and Eulerian averages are discussed, and meridional-vertical velocity correlations are provided.

Danielsen, E. F.↗

NASA NTRS1981

The magnetic field of Jupiter - A generalized inverse approach

The estimation of planetary magnetic fields from observations of the magnetic field gathered along a spacecraft flyby trajectory is examined with the aid of generalized inverse techniques, with application to the internal magnetic field of Jupiter. Model non-uniqueness resulting from the limited spatial extent of the observations and noise on the data is explored and quantitative estimates of the model parameter resolution are found. The presence of a substantial magnetic field of external origin due to the currents flowing in the Jovian magnetodisc is found to be an important source of error in estimates of the internal Jovian field, and new models explicitly incorporating these currents are proposed. New internal field models are derived using the vector helium magnetometer observations and the high field fluxgate observations of Pioneer 11, and knowledge of the external current system gained from the Pioneer 10 and Voyagers 1 and 2 encounters.

Connerney, J. E. P.↗

NASA NTRS1981

General aviation aircraft antennas for the global positioning system

Several antenna designs that utilize the NAVSTAR Global Positioning System in a low-cost system for general aviation aircraft were evaluated. Experimental investigations were made of crossed-dipoles, various types of crossed-slots, and microstrip antennas with modifications to improve their coverage. Principal plane radiation patterns for several of these antennas were measured on a one-seventh scale model of a Gates Lear Jet.

Gilreath, M. C.↗

NASA NTRS1981

The Numerical Studies Program for the Atmospheric General Circulation Experiment (AGCE) for Spacelab Flights

The atmospheric general circulation experiment (AGCE) numerical design for Spacelab flights was studied. A spherical baroclinic flow experiment which models the large scale circulations of the Earth's atmosphere was proposed. Gravity is simulated by a radial dielectric body force. The major objective of the AGCE is to study nonlinear baroclinic wave flows in spherical geometry. Numerical models must be developed which accurately predict the basic axisymmetric states and the stability of nonlinear baroclinic wave flows. A three dimensional, fully nonlinear, numerical model and the AGCE based on the complete set of equations is required. Progress in the AGCE numerical design studies program is reported.

Fowlis, W. W.↗

NASA NTRS1980

Consolidation of data base for Army generalized missile model

Data from plume interaction tests, nose mounted canard configuration tests, and high angle of attack tests on the Army Generalized Missile model are consolidated in a computer program which makes them readily accessible for plotting, listing, and evaluation. The program is written in FORTRAN and will run on an ordinary minicomputer. It has the capability of retrieving any coefficient from the existing DATAMAN tapes and displaying it in tabular or plotted form. Comparisons of data taken in several wind tunnels and of data with the predictions of Program MISSILE2 are also presented.

Klenke, D. J.↗

NASA NTRS1981

Wind-tunnel investigation of the tail-spoiler concept for stall-prevention on general aviation airplanes

The longitudinal aerodynamic characteristics of a full scale, single engine general aviation airplane equipped with an angle of attack limiting concept which used a tail mounted spoiler for stall prevention were investigated. The tail spoiler was deployed as a nonlinear function of changes in angle of attack in a narrow angle of attack range immediately preceding the stall angle. Spoiler deployment produced a nose down moment which limited the nose up trim capability of the elevator to an angle of attack below the stall angle of the airplane. The tail spoiler system produced significant increases in longitudinal stability and elevator hinge moments near the stall. The effects of power, flaps, and center of gravity position are also studied.

Satran, D. R.↗

NASA NTRS1981

Feasibility study: Atmospheric general circulation experiment, volume 1

The atmospheric general circulation experiment (AGCE) uses a rotating fluid flow cell assembly. The key technical areas affecting the feasibility of the design and operation of the AGCE are investigated. The areas investigated include materials for the flow cell assembly, thermal design, high voltage power supply design, effective retrieval and handling of experiment data and apparatus configuration. Several materials, DMSO and m-tolunitrile, were selected as candidate fluids for the flow cell principally for their high dielectric constant which permits the high voltage power supply design to be held to 15 kV and still simulate terrestrial gravity. Achievement of a low dissipation factor in the fluid to minimize internal heating from the applied electrical field depends strongly on purification and handling procedures. The use of sapphire as the outer hemisphere for the flow cell provides excellent viewing conditions without a significant impact on attaining the desired thermal gradients. Birefringent effects from sapphire can be held to acceptably low limits. Visualization of flow fluid is achieved through the motion of a dot matrix formed by photochromic dyes. Two dyes found compatible with the candidate fluids are spiropyran and triarylmethane. The observation of the dot motion is accomplished using a flying spot scanner.

Homsey, R. J.↗

NASA NTRS1981

Feasibility study: Atmospheric general circulation experiment, volume 2

The feasibility analysis of the atmospheric general circulation experiment (AGCE) are documented. The analysis performed in each technical area, the rationale and substantiation for the design approaches selected for the hardware, and the design details for the baseline AGCE are presented.

Homsey, R. J.↗

NASA NTRS1982

Summary of theoretical considerations and wind tunnel tests of an aerodynamic spoiler for stall proofing a general aviation airplane

An airplane stall proofing system utilizing a spoiler was investigated for application on a low wing airplane representative of typical general aviation aircraft. Tests of the full scale airplane were conducted in the NASA Langley 30 x 60 foot full scale wind tunnel. The test velocity was 86 feet per second, corresponding to a Reynolds number of 2.20 million. The stall proofing capability of the spoiler is shown and a theoretical approach to the design of the spoiler and analysis of the spoiler's contribution to the airplane's trim and longitudinal stability is verified. Controlled spoiler deployment in a narrow angle of attack range, 4 degrees, immediately preceding the stall angle will stall proof the airplane. The results also show some of the limitations of flight tests to determine spoiler deployment rate for good handling qualities.

Chevalier, H. L.↗

NASA NTRS1982

A concept for a fuel efficient flight planning aid for general aviation

A core equation for estimation of fuel burn from path profile data was developed. This equation was used as a necessary ingredient in a dynamic program to define a fuel efficient flight path. The resultant algorithm is oriented toward use by general aviation. The pilot provides a description of the desired ground track, standard aircraft parameters, and weather at selected waypoints. The algorithm then derives the fuel efficient altitudes and velocities at the waypoints.

Collins, B. P.↗

NASA NTRS1982

An experimental study of the effect of tail configuration on the spinning characteristics of general aviation aircraft

The feasibility of using static wind tunnel tests to obtain information about spin damping characteristics of an isolated general aviation aircraft tail was investigated. A representative tail section was oriented to the tunnel free streamline at angles simulating an equilibrium spin. A full range of normally encountered spin conditions was employed. Results of parametric studies performed to determine the effect of spin damping on several tail design parameters show satisfactory agreement with NASA rotary balance tests. Wing and body interference effects are present in the NASA studies at steep spin attitudes, but agreement improves with increasing pitch angle and spin rate, suggesting that rotational flow effects are minimal. Vertical position of the horizontal stabilizer is found to be a primary parameter affecting yaw damping, and horizontal tail chordwise position induces a substantial effect on pitching moment.

Ballin, M. G.↗

NASA NTRS1982

A general solution to the hidden-line problem

The requirements for computer-generated perspective projections of three dimensional objects has escalated. A general solution was developed. The theoretical solution to this problem is presented. The method is very efficient as it minimizes the selection of points and comparison of line segments and hence avoids the devastation of square-law growth.

Hedgley, D. R., Jr.↗

NASA NTRS1977

Experience with a vectorized general circulation weather model on Star-100

A version of an atmospheric general circulation model was vectorized to run on a CDC STAR 100. The numerical model was coded and run in two different vector languages, CDC and LRLTRAN. A factor of 10 speed improvement over an IBM 360/95 was realized. Efficient use of the STAR machine required some redesigning of algorithms and logic. This precludes the application of vectorizing compilers on the original scalar code to achieve the same results. Vector languages permit a more natural and efficient formulation for such numerical codes.

Soll, D. B.↗