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- SIMILITUDE REQUIREMENTS AND SCALING RELATIONSHIPS AS APPLIED TO MODEL TESTING , Technical Paper
Authors: C. H. Wolowicz, J. S. Brown, Jr. and W. P. Gilbert
Report Number: NASA-TP-1435
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: The similitude requirements for the most general test conditions are presented. These similitude requirements are considered in relation to the scaling relationships, test technique, test conditions (including supersonic flow), and test objectives. Particular emphasis is placed on satisfying the various similitude requirements for incompressible and compressible flow conditions. For free flying models tests, the test velocities for incompressible flow are scaled from Froude number similitude requirements and those for compressible flow are scaled from Mach number similitude requirements. The limitations of various test techniques are indicated, with emphasis on the free flying model.
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Report Date: August 1979
No. Pages: 64
Keywords: Aircraft models; Flight characteristics; Parameterization; Scale models; Similitude law.
- EVALUATION OF A SIMPLIFIED GROSS THRUST CALCULATION TECHNIQUE USING TWO PROTOTYPE F100 TURBOFAN ENGINES IN AN ALTITUDE FACILITY , Technical Paper
Authors: F. J. Kurtenbach
Report Number: NASA-TP-1482
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: The technique which relies on afterburner duct pressure measurements and empirical corrections to an ideal one dimensional flow analysis to determine thrust is presented. A comparison of the calculated and facility measured thrust values is reported. The simplified model with the engine manufacturer's gas generator model are compared. The evaluation was conducted over a range of Mach numbers from 0.80 to 2.00 and at altitudes from 4020 meters to 15,240 meters. The effects of variations in inlet total temperature from standard day conditions were explored. Engine conditions were varied from those normally scheduled for flight. The technique was found to be accurate to a twice standard deviation of 2.89 percent, with accuracy a strong function of afterburner duct pressure difference.
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Subject Category: 07
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Report Date: June 1979
No. Pages: 30
Keywords: Afterburning; Engine tests; Test facilities; Thrust measurement; Turbofan engines.
- PERFORMANCE EVALUATION METHOD FOR DISSIMILAR AIRCRAFT DESIGNS , Reference Publication
Authors: H. J. Walker
Report Number: NASA-RP-1042
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: A rationale is presented for using the square of the wingspan rather than the wing reference area as a basis for nondimensional comparisons of the aerodynamic and performance characteristics of aircraft that differ substantially in planform and loading. Working relationships are developed and illustrated through application to several categories of aircraft covering a range of Mach numbers from 0.60 to 2.00. For each application, direct comparisons of drag polars, lift-to-drag ratios, and maneuverability are shown for both nondimensional systems. The inaccuracies that may arise in the determination of aerodynamic efficiency based on reference area are noted. Span loading is introduced independently in comparing the combined effects of loading and aerodynamic efficiency on overall performance. Performance comparisons are made for the NACA research aircraft, lifting bodies, century-series fighter aircraft, F-111A aircraft with conventional and
supercritical wings, and a group of supersonic aircraft including the B-58 and XB-70 bomber aircraft. An idealized configuration is included in each category to serve as a standard for comparing overall efficiency.
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Report Date: September 1979
No. Pages: 72
Keywords: Aerodynamic characteristics; Aerodynamic configurations; Aircraft performance; Research aircraft; Wing span.
- A CHARACTERIZATION OF THE REAL ZEROS OF A PARTICULAR TRANSCENDENTAL FUNCTION , Technical Paper
Authors: D. R. Hedgley
Report Number: NASA-TP-1420
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: The real zeros of the transcendental function y = ax + becx are characterized, and the results should alleviate the difficulty of determining their existence, location, and number.
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Subject Category: 67
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Report Date: March 1979
No. Pages: 12
Keywords: Algorithms; Differential equations; Numerical analysis; Real variables; Transcendental functions.
- FLIGHT-MEASURED AFTERBODY PRESSURE COEFFICIENTS FROM AN AIRPLANE HAVING TWIN SIDE-BY-SIDE JET ENGINES FOR MACH NUMBERS FROM 0.6 TO 1.6 , Technical Paper
Authors: L. L. Steers
Report Number: NASA-TP-1549
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: Afterbody pressure distribution data were obtained in flight from an airplane having twin side-by-side jet exhausts. The data were obtained in level flight at Mach numbers from 0.60 to 1.60 and at elevated load factors for Mach numbers of 0.60, 0.90, and 1.20. The test altitude varied from 2300 meters (7500 feet) to 15,200 meters (50,000 feet) over a speed range that provided a matrix of constant Mach number and constant unit Reynolds number test conditions. The results of the full-scale flight afterbody pressure distribution program are presented in the form of plotted pressure distributions and tabulated pressure coefficients with Mach number, angle of attack, engine nozzle pressure ratio, and unit Reynolds number as controlled parameters.
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Report Date: November 1979
No. Pages: 88
Keywords: Afterbodies; Fighter aircraft; In-flight monitoring; Jet exhaust; Mach number.
- EFFECT OF NUMBER OF PROBES AND THEIR ORIENTATION ON THE CALCULATION OF SEVERAL COMPRESSOR FACE DISTORTION DESCRIPTORS , Technical Memorandum
Authors: F. Stoll, J. W. Tremback and H. H. Arnaiz
Report Number: NASA-TM-72859
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: A study was performed to determine the effects of the number and position of total pressure probes on the calculation of five compressor face distortion descriptors. This study used three sets of 320 steady state total pressure measurements that were obtained with a special rotating rake apparatus in wind tunnel tests of a mixed-compression inlet. The inlet was a one third scale model of the inlet on a YF-12 airplane, and it was tested in the wind tunnel at representative flight conditions at Mach numbers above 2.0. The study shows that large errors resulted in the calculation of the distortion descriptors even with a number of probes that were considered adequate in the past. There were errors as large as 30 and -50 percent in several distortion descriptors for a configuration consisting of eight rakes with five equal-area-weighted probes on each rake.
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Report Date: May 1979
No. Pages: 42
Keywords: Compressors; Error analysis; Pressure measurement; Surface distortion; Wind tunnel tests.
- PRECISION CONTROLLABILITY OF THE F-15 AIRPLANE , Technical Memorandum
Authors: Thomas R. Sisk and Neil W. Matheny
Report Number: NASA-TM-72861
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: A flying qualities evaluation conducted on a preproduction F-15 airplane permitted an assessment to be made of its precision controllability in the high subsonic and low transonic flight regime over the allowable angle of attack range. Precision controllability, or gunsight tracking, studies were conducted in windup turn maneuvers with the gunsight in the caged pipper mode and depressed 70 mils. This evaluation showed the F-15 airplane to experience severe buffet and mild-to-moderate wing rock at the higher angles of attack. It showed the F-15 airplane radial tracking precision to vary from approximately 6 to 20 mils over the load factor range tested. Tracking in the presence of wing rock essentially doubled the radial tracking error generated at the lower angles of attack. The stability augmentation system affected the tracking precision of the F-15 airplane more than it did that of previous aircraft studied.
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Report Date: May 1979
No. Pages: 46
Keywords: Aircraft maneuvers; Controllability; F-15 aircraft; Guns (ordnance); Tracking (position).
- IMPORTANT FACTORS IN THE MAXIMUM LIKELIHOOD ANALYSIS OF FLIGHT TEST MANEUVERS , Technical Paper
Authors: K. W. Iliff, R. E. Maine and T. D. Montgomery
Report Number: NASA-TP-1459
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: The information presented is based on the experience in the past 12 years at the NASA Dryden Flight Research Center of estimating stability and control derivatives from over 3500 maneuvers from 32 aircraft. The overall approach to the analysis of dynamic flight test data is outlined. General requirements for data and instrumentation are discussed and several examples of the types of problems that may be encountered are presented.
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Subject Category: 08
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Report Date: April 1979
No. Pages: 44
Keywords: Aircraft performance; Dynamic tests; Flight tests; Maximum likelihood estimates; NASA programs.
- STABILITY AND CONTROL DERIVATIVE ESTIMATES OBTAINED FROM FLIGHT DATA FOR THE BEECH 99 AIRCRAFT , Technical Memorandum
Authors: R. R. Tanner and T. D. Montgomery
Report Number: NASA-TM-72863
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: Lateral-directional and longitudinal stability and control derivatives were determined from flight data by using a maximum likelihood estimator for the Beech 99 airplane. Data were obtained with the aircraft in the cruise configuration and with one-third flap deflection. The estimated derivatives show good agreement with the predictions of the manufacturer.
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Report Date: April 1979
No. Pages: 38
Keywords: Aerodynamic configurations; Aircraft control; Beech 99 aircraft; Maximum likelihood estimates; Stability derivatives.
- CORRELATION OF PREDICTED AND MEASURED THERMAL STRESSES ON AN ADVANCED AIRCRAFT STRUCTURE WITH SIMILAR MATERIALS , Technical Memorandum
Authors: Jerald M. Jenkins
Report Number: NASA-TM-72862
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: A laboratory heating test simulating hypersonic heating was conducted on a heat-sink type structure to provide basic thermal stress measurements. Six NASTRAN models utilizing various combinations of bar, shear panel, membrane, and plate elements were used to develop calculated thermal stresses. Thermal stresses were also calculated using a beam model. For a given temperature distribution there was very little variation in NASTRAN calculated thermal stresses when element types were interchanged for a given grid system. Thermal stresses calculated for the beam model compared similarly to the values obtained for the NASTRAN models. Calculated thermal stresses compared generally well to laboratory measured thermal stresses. A discrepancy of signifiance occurred between the measured and predicted thermal stresses in the skin areas. A minor anomaly in the laboratory skin heating uniformity resulted in inadequate temperature input data for the structural
models.
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Report Date: April 1979
No. Pages: 40
Keywords: Aircraft structures; Data correlation; Hypersonic heat transfer; NASTRAN; Structural analysis.
- EXTREME MEAN AND ITS APPLICATIONS , Technical Memorandum
Authors: Ram Swaroop, James D. Brownlow and William R. Winter
Report Number: NASA-TM-81346
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: Extreme value statistics obtained from normally distributed data are considered. An extreme mean is defined as the mean of p-th probability truncated normal distribution. An unbiased estimate of this extreme mean and its large sample distribution are derived. The distribution of this estimate even for very large samples is found to be nonnormal. Further, as the sample size increases, the variance of the unbiased estimate converges to the Cramer-Rao lower bound. The computer program used to obtain the density and distribution functions of the standardized unbiased estimate, and the confidence intervals of the extreme mean for any data are included for ready application. An example is included to demonstrate the usefulness of extreme mean application.
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Subject Category: 65
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Report Date: December 1979
No. Pages: 37
Keywords: Computer programs; Mean; Normal density functions; Probability distribution functions; Range (extremes).
- PRECISION CONTROLLABILITY OF THE F-15 AIRPLANE , Technical Memorandum
Authors: Thomas R. Sisk and Neil W. Matheny
Report Number: NASA-TM-72861
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
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Report Date: January 1979
- CORRELATION OF PREDICTED AND MEASURED THERMAL STRESSES ON AN ADVANCED AIRCRAFT STRUCTURE WITH DISSIMILAR MATERIALS , Technical Memorandum
Authors: Jerald M. Jenkins
Report Number: NASA-TM-72865
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: Additional information was added to a growing data base from which estimates of finite element model complexities can be made with respect to thermal stress analysis. The manner in which temperatures were smeared to the finite element grid points was examined from the point of view of the impact on thermal stress calculations. The general comparison of calculated and measured thermal stresses is guite good and there is little doubt that the finite element approach provided by NASTRAN results in correct thermal stress calculations. Discrepancies did exist between measured and calculated values in the skin and the skin/frame junctures. The problems with predicting skin thermal stress were attributed to inadequate temperature inputs to the structural model rather than modeling insufficiencies. The discrepancies occurring at the skin/frame juncture were most likely due to insufficient modeling elements rather than temperature problems.
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Report Date: June 1979
No. Pages: 47
Keywords: Aircraft structures; Airframe materials; Data correlation; Hypersonic heat transfer; Stress measurement.
- FLIGHT TEST EVALUATION OF AN RAF HIGH ALTITUDE PARTIAL PRESSURE PROTECTIVE ASSEMBLY , Technical Memorandum
Authors: George R. Ashworth, Terrill W. Putnam, William J. Dana, Einar K. Enevoldson and William R. Winter
Report Number: NASA-TM-72864
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: A partial pressure suit was evaluated during tests in an F-104 and F-15 as a protective garment for emergency descents. The garment is an pressure jerkin and modified anti-g suit combined with an oronasal mask. The garment can be donned and doffed at the aircraft to minimize thermal buildup. The oronasal mask was favored by the pilots due to its immobility on the face during high g-loading. The garment was chosen to provide optimum dexterity for the pilot, which is not available in a full pressure suit, while protecting the pilot at altitudes up to 18,288 meters, during a cabin decompression, and subsequent aircraft descent. During cabin decompressions in the F-104 and F-15, cabin pressure altitude was measured at various aircraft angles of attack, Mach numbers, and altitudes to determine the effect of the aerodynamic slipstream on the cabin altitude.
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Report Date: June 1979
No. Pages: 37
Keywords: High altitude; Partial pressure; Pressure suits; Protective clothing; Slipstreams.
- SHUTTLE ORBITER RADAR CROSS-SECTIONAL ANALYSIS , Technical Memorandum
Authors: Dale W. Cooper and Robert James
Report Number: NASA-TM-72870
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: Theoretical and model simulation studies on signal to noise levels and shuttle radar cross section are described. Pre-mission system calibrations, system configuration, and postmission system calibration of the tracking radars are described. Conversion of target range, azimuth, and elevation into radar centered east north vertical position coordinates are evaluated. The location of the impinging rf energy with respect to the target vehicles body axis triad is calculated. Cross section correlation between the two radars is presented.
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Subject Category: 17
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Report Date: October 1979
No. Pages: 44
Keywords: Radar cross sections; Radar tracking; Space shuttle orbiters; Space transportation system flights.
- AIFTDS STAND-ALONE RMDU FLIGHT TEST REPORT , Technical Memorandum
Authors: Douglass O. Wilner
Report Number: NASA-TM-72867
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: The remote multiplexer/digitizer unit for the airborne integrated flight test data system was subjected to a flight test environment in order to study its dynamic response and that of its associated instrumentation circuitry during an actual flight test. The shielding schemes and instrumentation used are described and the data obtained are analyzed.
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Subject Category: 05
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Report Date: July 1979
No. Pages: 63
Keywords: Analog to digital converters; Dynamic response; Electronic modules; Flight tests; Multiplexing.
- EFFECT OF ELEMENT DENSITY ON THE NASTRAN CALCULATED MECHANICAL AND THERMAL STRESSES OF A SPAR , Technical Memorandum
Authors: Jerald M. Jenkins
Report Number: NASA-TM-72868
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: A NASTRAN model of a spar was examined to determine the sensitivity of calculated axial thermal stresses and bending stresses to changes in element density of the model. The thermal stresses calculated with three different element densities resulted in drastically differing values. The position of the constraint also significantly affected the value of the calculated thermal stresses. Mechanical stresses calculated from an applied loading were insensitive to element density.
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Report Date: October 1979
No. Pages: 14
Keywords: Density (mass/volume); Finite element method; NASTRAN; Structural members; Thermal stresses.
- CRITERIA FOR REPRESENTING CIRCULAR ARC AND SINE WAVE SPAR WEBS BY NON-CURVED ELEMENTS , Technical Memorandum
Authors: J. M. Jenkins
Report Number: NASA-TM-72869
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: The basic problem of how to simply represent a curved web of a spar in a finite element structural model was addressed. The ratio of flat web to curved web axial deformations and longitudinal rotations were calculated using NASTRAN models. Multiplying factors were developed from these calculations for various web thicknesses. These multiplying factors can be applied directly to the area and moment of inertia inputs of the finite element model. This allows the thermal stress relieving configurations of sine wave and circular arc webs to be simply accounted for in finite element structural models.
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Subject Category: 39
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Report Date: October 1979
No. Pages: 15
Keywords: Aircraft design; Contours; NASTRAN; Shapes; Thermal stresses.
- FRICTION CHARACTERISTICS OF STEEL SKIDS EQUIPPED WITH SKEGS ON A LAKEBED SURFACE , Technical Memorandum
Authors: Walter J. Sefic
Report Number: NASA-TM-81347
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: The coefficient of friction was determined for steel skids with and without skegs. The addition of a 1.27 centimeter deep skeg caused the coefficient of friction to increase from an average value of .36 to .53, a 47 percent increase over the flat skid. The addition of a .64 centimeter deep skeg increased the friction coefficient from .36 to .46, a 16 percent increase over the flat skid. Comparisons are made with data for similar test conditions obtained during the X-15 program.
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Report Date: December 1979
No. Pages: 16
Keywords: Aircraft structures; Coefficient of friction; Landing gear; Skid Landings; Steel structures.
- EVALUATION OF A SIMPLIFIED GROSS THRUST CALCULATION TECHNIQUE USING TWO PROTOTYPE F100 TURBOFAN ENGINES IN AN ALTITUDE FACILITY , Technical Paper
Authors: Frank J. Kurtenbach
Report Number: NASA-TP-1482
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: The technique which relies on afterburner duct pressure measurements and empirical corrections to an ideal one dimensional flow analysis to determine thrust is presented. A comparison of the calculated and facility measured thrust values is reported. The simplified model with the engine manufacturer's gas generator model are compared. The evaluation was conducted over a range of Mach numbers from 0.80 to 2.00 and at altitudes from 4020 meters to 15,240 meters. The effects of variations in inlet total temperature from standard day conditions were explored. Engine conditions were varied from those normally scheduled for flight. The technique was found to be accurate to a twice standard deviation of 2.89 percent, with accuracy a strong function of afterburner duct pressure difference.
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Report Date: January 1979
- IMPLEMENTATION OF A PARALLEL CHANNEL MAXIMUM LIKELIHOOD ESTIMATION ALGORITHM IN A MICROPROCESSOR , Contractor Report
Authors: S. G. Pratt, Gary L. Hartmann and Gunter Stein
Report Number: NASA-CR-179437
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: The NASA Dryden Flight Research Center has flight tested a modern adaptive control law in an F-8C aircraft using a remote digital augmentation technique. A ground-based computer containing the adaptive control algorithm estimated aircraft parameters using parallel channel maximum likelihood estimation (PCMLE). Control gains were computed from surface effectiveness estimates and uplinked to the test vehicle. The ground computer was a general-purpose mini-computer with 16-bit word length and floating-point hardware. The successful flight test of this identifier motivated a study to assess the feasibility of implementing the PCMLE algorithm in a microprocessor. The 16-bit TMS-9900 microprocessor of Texas Instruments was selected. The PCMLE algorithm was programmed using FORTRAN in conjunction with assembly language routines to minimize cycle time and maintain accuracy. The algorithm uses 10K (16-bit word) of memory and has a cycle time of 77 msec. The
algorithm has been evaluated in a real-time simulation operating at 10 sps. The report describes the development of the microprocessor software and its simulation performance.
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Report Date: December 1979
No. Pages: 187
Keywords: F-8; Maximum likelihood estimation; Microprocessor; PCMLE algorithm.
Notes: NASA Technical monitor: Kenneth J. Szalai.
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