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- DRAG REDUCTION OBTAINED BY THE ADDITION OF A BOATTAIL TO A BOX SHAPED VEHICLE
Authors: Randall L. Peterson
Report Number: NASA-CR-163113
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: Coast-down tests have been performed on a box-shaped ground vehicle used to simulate the aerodynamic drag of high volum transports such as delivery vans, motor homes and trucks. The results of these tests define the reduction in aerodynamic drag that can be obtained by the addition of either a full boattail or a trucated boattail to an otherwise blunt-based vehicle.
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Subject Category: AO3
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Report Date: August 1981
No. Pages: 32
Keywords: Aerodynamic drag; Streamlining; Fuel economy
- A REVIEW OF FLIGHT-TO-WIND TUNNEL DRAG CORRELATION , Conference Paper
Authors: Edwin J. Saltzman and Theodore G. Ayers
Report Number: AIAA812475
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: Comparisons are made of wind-tunnel-model and flight drag data for various configurations representing aircraft from the mid-1940s to the 1970s. Discrepancies between model and flight data such as Reynolds number effects, wall interference, and aeroelastic problems are discussed. String support effects and the inability of models to simulate surface deflections for longitudinal trim are also studied. A wind tunnel-to-flight correlation of turbulent friction drag confirms the incompressible Karman-Schoenherr variation of turbulent skin friction with Reynolds number and the T' method for accounting compressibility effects. NASA tested 10 deg cone research indicates that model tests which are affected by tunnel noise may require the lower disturbance level environment available in flight, and it is concluded that new cryogenic facilities will improve the fidelity of model simulations of full-scale flight flow phenomena.
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Subject Category: 05
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Report Date: November 1981
No. Pages: 18
Keywords: Aerodynamic drag; Aircraft performance; Flight simulation; Friction drag; Wind tunnel models; Wind tunnel tests
Notes: AIAA Paper 81-2475. AIAA, SETP, SFTE, SAE, ITEA, and IEEE, 1st Flight Testing Conference, Las Vegas, Nevada, November 11-13, 1981.
- PROGRAMMER'S MANUAL FOR MMLE3, A GENERAL FORTRAN PROGRAM FOR MAXIMUM LIKELIHOOD PARAMETER ESTIMATION , Technical Paper
Authors: R. E. Maine
Report Number: NASA-TP-1690
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: The MMLE3 is a maximum likelihood parameter estimation program capable of handling general bilinear dynamic equations of arbitrary order with measurement noise and/or state noise (process noise). The basic MMLE3 program is quite general and, therefore, applicable to a wide variety of problems. The basic program can interact with a set of user written problem specific routines to simplify the use of the program on specific systems. A set of user routines for the aircraft stability and control derivative estimation problem is provided with the program. The implementation of the program on specific computer systems is discussed. The structure of the program is diagrammed, and the function and operation of individual routines is described. Complete listings and reference maps of the routines are included on microfiche as a supplement. Four test cases are discussed; listings of the input cards and program output for the test cases are included on
microfiche as a supplement.
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Subject Category: 59
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Report Date: June 1981
No. Pages: 118
Keywords: Computer programs; Flow charts; FORTRAN; Manuals; Maximum likelihood estimates.
Notes: Document includes a microfiche supplement.
- FLIGHT EVALUATION OF A SIMPLIFIED GROSS THRUST CALCULATION TECHNIQUE USING AN F100 TURBOFAN ENGINE IN AN F-15 AIRPLANE , Technical Paper
Authors: F. J. Kurtenbach and F. W. Burcham, Jr.
Report Number: NASA-TP-1782
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: A simplified gross thrust calculation technique was evaluated in flight tests on an F-15 aircraft using prototype F100-PW-100 engines. The technique relies on afterburner duct pressure measurements and empirical corrections to an ideal one-dimensional analysis to determine thrust. In-flight gross thrust calculated by the simplified method is compared to gross thrust calculated by the engine manufacturer's gas generator model. The evaluation was conducted at Mach numbers from 0.6 to 1.5 and at altitudes from 6000 meters to 13,700 meters. The flight evaluation shows that the simplified gross thrust method and the gas generator method agreed within plus or minus 3 percent. The discrepancies between the data generally fell within an uncertainty band derived from instrumentation errors and recording system resolution.
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Subject Category: 07
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Report Date: January 1981
No. Pages: 21
Keywords: F-15 aircraft; Gas generators; In-flight monitoring; Jet thrust; Turbofan engines.
- THE THEORY AND PRACTICE OF ESTIMATING THE ACCURACY OF DYNAMIC FLIGHT-DETERMINED COEFFICIENTS , Reference Publication
Authors: R. E. Maine and K. W. Iliff
Report Number: NASA-RP-1077
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: Means of assessing the accuracy of maximum likelihood parameter estimates obtained from dynamic flight data are discussed. The most commonly used analytical predictors of accuracy are derived and compared from both statistical and simplified geometrics standpoints. The accuracy predictions are evaluated with real and simulated data, with an emphasis on practical considerations, such as modeling error. Improved computations of the Cramer-Rao bound to correct large discrepancies due to colored noise and modeling error are presented. The corrected Cramer-Rao bound is shown to be the best available analytical predictor of accuracy, and several practical examples of the use of the Cramer-Rao bound are given. Engineering judgement, aided by such analytical tools, is the final arbiter of accuracy estimation.
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Subject Category: 65
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Report Date: July 1981
No. Pages: 63
Keywords: Accuracy; Confidence limits; Data reduction; Mathematical models; Maximum likelihood estimates.
- APPLICATION OF A PERFORMANCE MODELING TECHNIQUE TO AN AIRPLANE WITH VARIABLE SWEEP WINGS , Technical Paper
Authors: P. C. Redin
Report Number: NASA-TP-1855
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: A performance modeling concept previously applied to an F-104F G and a YF-12C airplane was applied to an F-111A airplane. This application extended the concept to an airplane with variable sweep wings. The performance model adequately matched flight test data for maneuvers flown at different wing sweep angles at maximum afterburning and intermediate power settings. For maneuvers flown at less than intermediate power, including dynamic maneuvers, the performance model was not validated because the method used to correlate model and in-flight power setting was not adequate. Individual dynamic maneuvers were matched sucessfully by using adjustments unique to each maneuver.
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Subject Category: 05
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Report Date: May 1981
No. Pages: 33
Keywords: Aircraft maneuvers; Aircraft performance; Computerized simulation; Drag; F-111 aircraft.
- CLIMATOLOGICAL CHARACTERISTICS OF HIGH ALTITUDE WIND SHEAR AND LAPSE RATE LAYERS , Technical Memorandum
Authors: L. J. Ehernberger and N.B. Guttman
Report Number: NASA-TM-81353
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: Indications of the climatological distribution of wind shear and temperature lapse and inversion rates as observed by rawinsonde measurements over the western United States are recorded. Frequencies of the strongest shear, lapse rates, and inversion layer strengths were observed for a 1 year period of record and were tabulated for the lower troposphere, the upper troposphere, and five altitude intervals in the lower stratosphere. Selected bivariate frequencies were also tabulated. Strong wind shears, lapse rates, and inversion are observed less frequently as altitude increases from 175 millibars to 20 millibars. On a seasonal basis the frequencies were higher in winter than in summer except for minor influences due to increased tropopause altitude in summer and the stratospheric wind reversal in the spring and fall.
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Subject Category: 47
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Report Date: February 1981
No. Pages: 99
Keywords: Clear air turbulence; Climatology; High altitude; Lapse rate; Temperature inversions.
- DIVERSITY TECHNIQUES FOR OMNIDIRECTIONAL TELEMETRY COVERAGE OF THE HIMAT RESEARCH VEHICLE , Technical Paper
Authors: P. F. Harney
Report Number: NASA-TP-1830
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: The highly maneuverable aircraft technology (HiMAT) remotely piloted research vehicle (RPRV) was flight tested and a number of technological advances applicable to future fighter aircraft were demonstrated. The aircraft control system uses airborne and ground-based computers which communicate via uplink and downlink telemetry. Antenna radiation patterns are normally much less than ideal for continuous reception or transmission for all aircraft attitudes. After flight qualification and testing on other aircraft, a frequency diversity concept and an antenna diversity concept were implemented on the HiMAT vehicle to obtain omnidirectional telemetry coverage.
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Subject Category: 06
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Report Date: March 1981
No. Pages: 18
Keywords: Antenna radiation patterns; Command and control; Omnidirectional antennas; Reception diversity; Remotely piloted vehicles.
- COMPARISON OF THREE THRUST CALCULATION METHODS USING IN-FLIGHT THRUST DATA , Technical Memorandum
Authors: D. L. Hughes
Report Number: NASA-TM-81360
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: The gross thrust of an experimental airplane was determined by each method using the same flight maneuvers and generally the same data parameters. Coefficients determined from thrust stand calibrations for each of the three methods were then extrapolated to cruise flight conditions. The values of total aircraft gross thrust calculated by the three methods for cruise flight conditions agreed within + or - 3 percent. The disagreement in the values of thrust calculated by the different techniques manifested itself as a bias in the data. There was little scatter (0.5 percent) for the thrust levels examined in flight.
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Subject Category: 05
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Report Date: July 1981
No. Pages: 35
Keywords: Jet thrust; Nozzle thrust coefficients; Thrust measurement.
- DESCRIPTION OF THE HIMAT TAILORED COMPOSITE STRUCTURE AND LABORATORY MEASURED VEHICLE SHAPE UNDER LOAD , Technical Memorandum
Authors: R. C. Monaghan
Report Number: NASA-TM-81354
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: The aeroelastically tailored outer wing and canard of the highly maneuverable aircraft technology (HiMAT) vehicle are closely examined and a general description of the overall structure of the vehicle is provided. Test data in the form of laboratory measured twist under load and predicted twist from the HiMAT NASTRAN structural design program are compared. The results of this comparison indicate that the measured twist is generally less than the NASTRAN predicted twist. These discrepancies in twist predictions are attributed, at least in part, to the inability of current analytical composite materials programs to provide sufficiently accurate properties of matrix dominated laminates for input into structural programs such as NASTRAN.
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Subject Category: 05
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Report Date: February 1981
No. Pages: 60
Keywords: Aeroelasticity; Aircraft structures; Canard configurations; Composite structures; Structural analysis.
- HISTORICAL BACKGROUND AND DESIGN EVOLUTION OF THE TRANSONIC AIRCRAFT TECHNOLOGY SUPERCRITICAL WING , Technical Memorandum
Authors: T. G. Ayers and J. B. Hallissy
Report Number: NASA-TM-81356
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: Two dimensional wind tunnel test results obtained for supercritical airfoils indicated that substantial improvements in aircraft performance at high subsonic speeds could be achieved by shaping the airfoil to improve the supercritical flow above the upper surface. Significant increases in the drag divergence Mach number, the maximum lift coefficient for buffer onset, and the Mach number for buffet onset at a given lift coefficient were demonstrated for the supercritical airfoil, as compared with a NACA 6 series airfoil of comparable thickness. These trends were corroborated by results from three dimensional wind tunnel and flight tests. Because these indicated extensions of the buffet boundaries could provide significant improvements in the maneuverability of a fighter airplane, an exploratory wind tunnel investigation was initiated which demonstrated that significant aerodynamic improvements could be achieved from the direct substitution of a
supercritical airfoil on a variable wing sweep multimission airplane model.
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Subject Category: 02
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Report Date: August 1981
No. Pages: 33
Keywords: Aircraft maneuvers; Boundary layer separation; Histories; Supercritical wings; Supersonic aircraft.
- THE DEVELOPMENT AND FLIGHT TEST EVALUATION OF AN INTEGRATED PROPULSION CONTROL SYSTEM FOR THE HIMAT RESEARCH AIRPLANE , Conference Paper
Authors: J. L. Baer-Riedhart
Report Number: H-1157
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: The Highly Maneuverable Aircraft Technology airplane is a .44-scale version of an advanced fighter design. It is remotely piloted from a ground cockpit and is powered by a J85-GE-21 turbojet engine. The engine is electronically controlled by a digital computer onboard the airplane to operate at selected engine operation modes. The HiMAT design and development philosophy emphasized high-risk, low-cost and minimum testing, and also required that no single failure would cause loss of the vehicle. This philosophy generated unique requirements for design, computer simulation methods, specialized test techniques, and support systems which are discussed in this paper.
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Subject Category: 07
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From NTRS: Locate an electronic (PDF) copy of the document.
Report Date: November 1981
No. Pages: 10
Keywords: Airborne/spaceborne computers; Engine control; Flight tests; Remotely piloted vehicles; Research aircraft.
Notes: AIAA, SETP, SFTE, SAE, ITEA, and IEEE, Flight Testing Conference, 1st, Las Vegas, NV, Nov. 11-13, 1981. AIAA PAPER 81-2467.
- USER'S MANUAL FOR FSLIP-3, FLEXSTAB LOADS INTEGRATION PROGRAM , Technical Memorandum
Authors: R. L. Sims
Report Number: NASA-TM-81364
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: The FSLIP program documentation and user's manual is presented. As a follow on program to the FLEXSTAB computer analysis system, the primary function of this FORTRAN IV program is to integrate panel pressure coefficients computed by FLEXSTAB to obtain total shear, bending, and torque airloads on various surfaces, summed relative to user specified axes. The program essentially replaces the ALOADS module in FLEXSTAB with expanded capabilities and flexibility. As such, FSLIP is generalized to work on any FLEXSTAB model or other pressure data if in a compatible format.
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Subject Category: 61
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Report Date: August 1981
No. Pages: 121
Keywords: Aerodynamic loads; Computer systems programs; Pressure distribution; User manuals (computer programs).
- ANALYTIC STUDY OF ORBITER LANDING PROFILES , Technical Memorandum
Authors: H. J. Walker
Report Number: NASA-TM-81365
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: A broad survey of possible orbiter landing configurations was made with specific goals of defining boundaries for the landing task. The results suggest that the center of the corridors between marginal and routine represents a more or less optimal preflare condition for regular operations. Various constraints used to define the boundaries are based largely on qualitative judgements from earlier flight experience with the X-15 and lifting body research aircraft. The results should serve as useful background for expanding and validating landing simulation programs. The analytic approach offers a particular advantage in identifying trends due to the systematic variation of factors such as vehicle weight, load factor, approach speed, and aim point. Limitations such as a constant load factor during the flare and using a fixed gear deployment time interval, can be removed by increasing the flexibility of the computer program. This analytic definition of
landing profiles of the orbiter may suggest additional studies, including more configurations or more comparisons of landing profiles within and beyond the corridor boundaries.
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Subject Category: 01
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Report Date: September 1981
No. Pages: 115
Keywords: Glide paths; Horizontal spacecraft landing; Landing simulation; Space shuttle orbiters.
- ANALYSIS OF A LONGITUDINAL PILOT-INDUCED OSCILLATION EXPERIENCED ON THE APPROACH AND LANDING TEST OF THE SPACE SHUTTLE , Technical Memorandum
Authors: J. W. Smith
Report Number: NASA-TM-81366
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: During the final free flight (FF-5) of the shuttle's approach and landing tests, the vehicle experienced pilot-induced oscillations near touchdown. The light test data showed that pilot inputs to the hand controller reached peak-to-peak amplitudes of 20 deg at a frequency between 3 and 3.5 radians per second. The controller inputs were sufficient to exceed the priority rate limit set in the pitch axis. A nonlinear analytical study was conducted to investigate the combined effects of pilot input, rate limiting, and time delays. The frequency response of the total system is presented parametrically as a function of the three variables. In general, with no dead time, for controller inputs of 5 deg or less, the total system behaves in a linear fashion. For 10 deg of controller input, independent of the delay time, the elevon loop will be rate saturated above a frequency of 4 radians per second.
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Subject Category: 08
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Report Date: December 1981
No. Pages: 45
Keywords: Approach and landing tests (STS); Lateral control; Longitudinal stability; Oscillations; Pilot induced oscillation.
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