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  1. ANALYSIS OF LONGITUDINAL PILOT-INDUCED OSCILLATION TENDENCIES OF YF-12 AIRCRAFT , Technical Note
    Authors: J. W. Smith and D. T. Berry
    Report Number: NASA-TN-D-7900
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: Aircraft flight and ground tests and simulator studies were conducted to explore pilot-induced oscillation tendencies. Linear and nonlinear calculations of the integrated flight control system's characteristics were made to analyze and predict the system's performance and stability. The investigations showed that the small-amplitude PIO tendency was caused by the interaction of the pilot with a combination of the aircraft's short-period poles and the structural first bending mode zeros. It was found that the large-amplitude PIO's were triggered by abrupt corrective control actions by the pilot, which caused the stability augmentation system servo to position and rate limit. The saturation in turn caused additional phase lag, further increasing the tendency of the overall system to sustain a PIO.
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    Subject Category: 08
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    Report Date: February 1975
    No. Pages: 40
    Keywords:      Fighter aircraft; Longitudinal control; Pilot induced oscillation; Pilot performance; Pitching moments.


  2. A NEW FLIGHT TEST DATA SYSTEM FOR NASA AERONAUTICAL FLIGHT RESEARCH , Conference Paper
    Authors: K. C. Sanderson
    Report Number: H-833
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: The airborne integrated flight test data system (AIFTDS) is described. This system integrates an airborne digital computer with a high-bit-rate pulse code modulation system. Its design was influenced by in-house technical experience with similar modules and by the multiproject environment in which it was expected to operate. The present work describes events leading to the development of the system, reviews factors that influenced the objectives for the system and the resulting design, and describes the elements themselves. Block diagrams supplement the text.
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    Subject Category: 06
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    Report Date: January 1975
    No. Pages: 17
    Keywords:      Airborne/spaceborne computers; Computer systems design; Data systems; Flight tests; NASA programs.
    Notes: In: International Aerospace Instrumentation Symposium, 8th, Cranfield, Beds., England, Mar. 24-27, 1975, Proceedings. London, Royal Aeronautical Society, 1975.


  3. HIGH ALTITUDE GUST ACCELERATION ENVIRONMENT AS EXPERIENCED BY A SUPERSONIC AIRPLANE , Technical Note
    Authors: L. J. Ehernberger and B. J. Love
    Report Number: NASA-TN-D-7868
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: High altitude turbulence experienced at supersonic speeds is described in terms of gust accelerations measured on the YF-12A airplane. The data were obtained during 90 flights at altitudes above 12.2 kilometers (40,000 feet). Subjective turbulence intensity ratings were obtained from air crew members. The air crew often rated given gust accelerations as being more intense during high altitude supersonic flight than during low altitude subsonic flight. The portion of flight distance in turbulence ranged from 6 percent to 8 percent at altitudes between 12.2 kilometers and 16.8 kilometers (40,000 feet and 55,000 feet) to less than 1 percent at altitudes above 18.3 kilometers (60,000 feet). The amount of turbulence varied with season, increasing by a factor of 3 or more from summer to winter. Given values of gust acceleration were less frequent, on the basis of distance traveled, for supersonic flight of the YF-12A airplane at altitudes above 12.2 kilometers (40,000 feet) than for subsonic flight of a jet passenger airplane at altitudes below 12.2 kilometers (40,000 feet). The median thickness of high altitude turbulence patches was less than 400 meters (1300 feet); the median length was less than 16 kilometers (10 miles). The distribution of the patch dimensions tended to be log normal.
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    Report Date: January 1975
    No. Pages: 26
    Keywords:      Atmospheric turbulence; Data acquisition; Gust loads; Supersonic speed; YF-12 aircraft.


  4. MECHANIZATION OF AND EXPERIENCE WITH A TRIPLEX FLY-BY-WIRE BACKUP CONTROL SYSTEM
    Authors: W. P. Lock, W. R. Petersen and G. B. Whitman
    Report Number: H-839
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: A redundant three-axis analog control system was designed and developed to back up a digital fly-by-wire control system for an F-8C airplane. Forty-two flights, involving 58 hours of flight time, were flown by six pilots. The mechanization and operational experience with the backup control system, the problems involved in synchronizing it with the primary system, and the reliability of the system are discussed. The backup control system was dissimilar to the primary system, and it provided satisfactory handling through the flight envelope evaluated. Limited flight tests of a variety of control tasks showed that control was also satisfactory when the backup control system was controlled by a minimum-displacement (force) side stick. The operational reliability of the F-8 digital fly-by-wire control system was satisfactory, with no unintentional downmodes to the backup control system in flight. The ground and flight reliability of the system's components is discussed.
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    Report Date: February 1975
    No. Pages: 31
    Keywords:      Aircraft control; Digital systems; F-8 aircraft; Fly by wire control; Redundant components.
    Notes: In its Description and Flight Test Results of the NASA F-8 Digital Fly-by-Wire Control System p 41-72.


  5. FLIGHT TEST EXPERIENCE WITH THE F-8 DIGITAL FLY-BY-WIRE SYSTEM
    Authors: K. J. Szalai
    Report Number: H-840
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: Flight test results of the F-8 digital fly-by-wire (DFBW) control system are presented and the implications for application to active control technology (ACT) are discussed. The F-8 DFBW system has several of the attributes of proposed ACT systems, so the flight test experience is helpful in assessing the capabilities of those systems. Topics of discussion include the predicted and actual flight performance of the control system, assessments of aircraft flying qualities and other piloting factors, software management and control, and operational experience.
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    Report Date: February 1975
    No. Pages: 54
    Keywords:      Aircraft control; Aircraft performance; Digital systems; F-8 aircraft; Fly by wire control.
    Notes: In its Description and Flight Test Results of the NASA F-8 Digital Fly-by-Wire Control System p 127-180.


  6. DESIGN AND DEVELOPMENT EXPERIENCE WITH A DIGITAL FLY-BY-WIRE CONTROLSYSTEM IN AN F-8C AIRPLANE
    Authors: D. A. Deets
    Report Number: H-841
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: To assess the feasibility of a digital fly-by-wire system, the mechanical flight control system of an F-8C airplane was replaced with a digital system and an analog backup system. The Apollo computer was used as the heart of the primary system. This paper discusses the experience gained during the design and development of the system and relates it to active control systems that are anticipated for future civil transport applications.
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    Report Date: February 1975
    No. Pages: 28
    Keywords:      Aircraft control; Digital systems; F-8 aircraft; Fly by wire control; Performance prediction.
    Notes: In its Description and Flight Test Results of the NASA F-8 Digital Fly-by-Wire Control System p 13-40.


  7. FLIGHT DETERMINED LIFT AND DRAG CHARACTERISTICS OF AN F-8 AIRPLANE MODIFIED WITH A SUPERCRITICAL WING WITH COMPARISON TO WIND-TUNNEL RESULTS , Technical Memorandum
    Authors: J. S. Pyle and L. L. Steers
    Report Number: NASA-TM-X-3250
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: Flight measurements obtained with a TF-8A airplane modified with a supercritical wing are presented for altitudes from 7.6 kilometers (25,000 feet) to 13.7 kilometers (45,000 feet), Mach numbers from 0.6 to 1.2, and Reynolds numbers from 0.8 x 10 to the 7th power to 2.3 x 10 to the 7th power. Flight results for the airplane with and without area-rule fuselage fairings are compared. The techniques used to determine the lift and drag characteristics of the airplane are discussed. Flight data are compared with wind-tunnel model results, where applicable.
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    Subject Category: 02
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    Report Date: June 1975
    No. Pages: 87
    Keywords:      Aerodynamic drag; F-8 aircraft; Flight tests; Lift; Supercritical wings.


  8. AN OVERVIEW OF NASA'S DIGITAL FLY-BY-WIRE TECHNOLOGY DEVELOPMENTPROGRAM
    Authors: C. R. Jarvis
    Report Number: H-845
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: The feasibility of using digital fly-by-wire systems to control aircraft was demonstrated by developing and flight testing a single channel system, which used Apollo hardware, in an F-8C test airplane. This is the first airplane to fly with a digital fly-by-wire system as its primary means of control and with no mechanical reversion capability. The development and flight test of a triplex digital fly-by-wire system, which will serve as an experimental prototype for future operational digital fly-by-wire systems, is underway.
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    Report Date: February 1975
    No. Pages: 11
    Keywords:      Aircraft control; Digital systems; F-8 aircraft; Flight tests; Fly by wire control.
    Notes: In its Description and Flight Test Results of the NASA F-8 Digital Fly-by-Wire Control System p 1-12.


  9. A PILOT'S OPINION OF THE F-8 DIGITAL FLY-BY-WIRE AIRPLANE
    Authors: G. E. Krier
    Report Number: H-846
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: The handling qualities of the F-8 digital fly-by-wire airplane are evaluated by using the Cooper-Harper rating scale. The reasons for the ratings are given, as well as a short description of the flying tasks. It was concluded that the handling qualities of the airplane were good in most situations, although occasional ratings of unsatisfactory were given.
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    Report Date: February 1975
    No. Pages: 15
    Keywords:      Aircraft control; Aircraft performance; Digital systems; F-8 aircraft; Fly by wire control.
    Notes: In its Description and Flight Test Results of the NASA F-8 Digital Fly-by-Wire Control System p 181-195.


  10. EFFECTS OF TIME-SHIFTED DATA ON FLIGHT DETERMINED STABILITY AND CONTROL DERIVATIVES , Technical Note
    Authors: S. T. Steers and K. W. Iliff
    Report Number: NASA-TN-D-7830
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: Flight data were shifted in time by various increments to assess the effects of time shifts on estimates of stability and control derivatives produced by a maximum likelihood estimation method. Derivatives could be extracted from flight data with the maximum likelihood estimation method even if there was a considerable time shift in the data. Time shifts degraded the estimates of the derivatives, but the degradation was in a consistent rather than a random pattern. Time shifts in the control variables caused the most degradation, and the lateral-directional rotary derivatives were affected the most by time shifts in any variable.
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    Subject Category: 08
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    Report Date: March 1975
    No. Pages: 86
    Keywords:      Aerodynamic stability; Aircraft stability; Data processing; Flight control; Maximum likelihood estimates.


  11. FLIGHT EVALUATION OF THE M2-F3 LIFTING BODY HANDLING QUALITIES AT MACH NUMBERS FROM 0.30 TO 1.61 , Technical Note
    Authors: R. W. Kempel, W. H. Dana and A. G. Sim
    Report Number: NASA-TN-D-8027
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: Percentage distributions of 423 pilot ratings obtained from 27 flights are used to indicate the general level of handling qualities of the M2-F3 lifting body. Percentage distributions are compared on the basis of longitudinal and lateral-directional handling qualities, control system, control system status, and piloting task. Ratings of longitudinal handling qualities at low speed were slightly better than those for transonic and supersonic speed. The ratings of lateral-directional handling qualities were unaffected by speed and configuration. Specific handling qualities problems are discussed in detail, and comparisons are made with pertinent handling qualities criteria.
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    Report Date: July 1975
    No. Pages: 45
    Keywords:      Aircraft configurations; Aircraft control; Controllability; M-2 lifting body; Postflight analysis.


  12. DESCRIPTION AND FLIGHT TEST RESULTS OF THE NASA F-8 DIGITAL FLY-BY-WIRE CONTROL SYSTEM , Technical Note
    Authors: Various
    Report Number: NASA-TN-D-7843
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: A NASA program to develop digital fly-by-wire (DFBW) technology for aircraft applications is discussed. Phase I of the program demonstrated the feasibility of using a digital fly-by-wire system for aircraft control through developing and flight testing a single channel system, which used Apollo hardware, in an F-8C airplane. The objective of Phase II of the program is to establish a technology base for designing practical DFBW systems. It will involve developing and flight testing a triplex digital fly-by-wire system using state-of-the-art airborne computers, system hardware, software, and redundancy concepts. The papers included in this report describe the Phase I system and its development and present results from the flight program. Man-rated flight software and the effects of lightning on digital flight control systems are also discussed.
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    Report Date: February 1975
    No. Pages: 198
    Keywords:      Aircraft control; Digital systems; Equipment specifications; F-8 aircraft; Fly by wire control.


  13. DEVELOPMENT OF A REMOTE DIGITAL AUGMENTATION SYSTEM AND APPLICATION TO A REMOTELY PILOTED RESEARCH VEHICLE , Technical Note
    Authors: J. W. Edwards and D. A. Deets
    Report Number: NASA-TN-D-7941
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: A cost-effective approach to flight testing advanced control concepts with remotely piloted vehicles is described. The approach utilizes a ground based digital computer coupled to the remotely piloted vehicle's motion sensors and control surface actuators through telemetry links to provide high bandwidth feedback control. The system was applied to the control of an unmanned 3/8-scale model of the F-15 airplane. The model was remotely augmented; that is, the F-15 mechanical and control augmentation flight control systems were simulated by the ground-based computer, rather than being in the vehicle itself. The results of flight tests of the model at high angles of attack are discussed.
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    Subject Category: 05
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    Report Date: April 1975
    No. Pages: 54
    Keywords:      Aircraft control; Digital command systems; Digital computers; Remote control; Research aircraft.


  14. AN ALGORITHM AND COMPUTER PROGRAM TO LOCATE REAL ZEROS OF REAL POLYNOMIALS , Technical Note
    Authors: D. R. Hedgley, Jr.
    Report Number: NASA-TN-D-8009
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: A method for reliably extracting real zeros of real polynomials using an expanded two-point secant and bisection method is formed into an algorithm for a digital computer, and a computer program based on this algorithm is presented. The results obtained with the program show that the proposed method compares favorably with the Laguerre, Newton-Raphson, and Jenkins-Traub methods when the polynomial has all real zeros, and is more efficient when the polynomial has complex zeros.
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    Subject Category: 64
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    Report Date: June 1975
    No. Pages: 24
    Keywords:      Algorithms; Computer programs; Digital computers; Polynomials; Real numbers.


  15. A FORTRAN PROGRAM FOR DETERMINING AIRCRAFT STABILITY AND CONTROL DERIVATIVES FROM FLIGHT DATA , Technical Note
    Authors: R. E. Maine and K. W. Iliff
    Report Number: NASA-TN-D-7831
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: A digital computer program written in FORTRAN IV for the estimation of aircraft stability and control derivatives is presented. The program uses a maximum likelihood estimation method, and two associated programs for routine, related data handling are also included. The three programs form a package that can be used by relatively inexperienced personnel to process large amounts of data with a minimum of manpower. This package was used to successfully analyze 1500 maneuvers on 20 aircraft, and is designed to be used without modification on as many types of computers as feasible. Program listings and sample check cases are included.
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    Subject Category: 61
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    Report Date: April 1975
    No. Pages: 177
    Keywords:      Aircraft control; Aircraft stability; Computer programs; Flight characteristics; FORTRAN.


  16. EVALUATION OF A HEMISPHERICAL HEAD FLOW DIRECTION SENSOR FOR INLET DUCT MEASUREMENTS , Technical Memorandum
    Authors: D. L. Bennett
    Report Number: NASA-TM-X-3232
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: A hemispherical head flow direction sensor was tested in a wind tunnel to evaluate its effectiveness for measuring dynamic duct flow direction angles of plus and minus 27 degrees. The tests were conducted at Reynolds numbers of 3.8 million per meter (1.0 million per foot) and 4.92 million per meter (1.5 million per foot) and at Mach numbers from 0.30 to 0.70. The design criteria for the probe are discussed and the wind tunnel results are presented. Three techniques for deriving the flow angles are described.
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    Subject Category: 02
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    Report Date: May 1975
    No. Pages: 24
    Keywords:      Calibrating; Ducted flow; Flow direction indicators; Flow distribution; Wind tunnel tests.


  17. MEASUREMENTS AND ANALYSIS OF AIRCRAFT AIRFRAME NOISE , Conference Paper
    Authors: T. W. Putnam, P. L. Lasagna and K. C. White
    Report Number: H-863
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: Flyover measurements of the airframe noise of AeroCommander, JetStar, CV-990, and B-747 aircraft are presented. Data are shown for both cruise and landing configurations. Correlations between airframe noise and aircraft parameters are developed and presented. The landing approach airframe noise for the test aircraft was approximately 10 EPNdB below present FAA certification requirements.
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    Report Date: March 1975
    No. Pages: 8
    Keywords:      Aerodynamic noise; Aircraft noise; Airframes; Flight tests; Noise measurement.
    Notes: American Institute of Aeronautics and Astronautics, Aero-Acoustics Conference, 2nd, Hampton, Va., Mar. 24-26, 1975. AIAA Paper 75-510.


  18. AERODYNAMIC DRAG REDUCTION TESTS ON A FULL-SCALE TRACTOR-TRAILER COMBINATION AND A REPRESENTATIVE BOX-SHAPED GROUND VEHICLE , Conference Paper
    Authors: L. L. Steers, L. C. Montoya and E. J. Saltzman
    Report Number: H-875
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: No Abstract Available.
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    Subject Category: 02
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    Report Date: August 1975
    No. Pages: 15
    Keywords:      Aerodynamic drag; Drag measurement; Drag reduction; Fuel consumption; Trucks.
    Notes: Society of Automotive Engineers, West Coast Meeting, Seattle, Wash., Aug. 11-14, 1975, 15 p. NASA-supported research.


  19. EXPLORATORY WIND TUNNEL TESTS OF A SHOCK-SWALLOWING AIR DATA SENSOR AT A MACH NUMBER OF APPROXIMATELY 1.83 , Technical Memorandum
    Authors: J. Nugent, L. M. Couch and L. D. Webb
    Report Number: NASA-TM-X-56030
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: The test probe was designed to measure free-stream Mach number and could be incorporated into a conventional airspeed nose boom installation. Tests were conducted in the Langley 4-by 4-foot supersonic pressure tunnel with an approximate angle of attack test range of -5 deg to 15 deg and an approximate angle of sideslip test range of + or - 4 deg. The probe incorporated a variable exit area which permitted internal flow. The internal flow caused the bow shock to be swallowed. Mach number was determined with a small axially movable internal total pressure tube and a series of fixed internal static pressure orifices. Mach number error was at a minimum when the total pressure tube was close to the probe tip. For four of the five tips tested, the Mach number error derived by averaging two static pressures measured at horizontally opposed positions near the probe entrance were least sensitive to angle of attack changes. The same orifices were also used to derive parameters that gave indications of flow direction.
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    Subject Category: 06
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    Report Date: March 1975
    No. Pages: 41
    Keywords:      Airspeed; Data acquisition; Flight characteristics; Mach number; Wind tunnel tests.


  20. A FLIGHT TEST INVESTIGATION OF THE ROLLING MOMENTS INDUCED ON A T-37B AIRPLANE IN THE WAKE OF A B-747 AIRPLANE , Technical Memorandum
    Authors: H. J. Smith
    Report Number: NASA-TM-X-56031
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: A flight test investigation of the B-747 vortex wake characteristics was conducted using a T-37B as a probe aircraft. The primary purpose of the program was the validation of the results of B-747 model tests which predicted significant alleviation of the vortex strength when only the inboard flaps were deflected. Measurements of the vortex-induced rolling moments of the probe aircraft showed that the predicted alleviation did occur. The effects of landing gear extension, increased lift coefficient, idle thrust, and sideslip were investigated, and all had an adverse effect on the alleviated condition as evidenced by increased induced rolling moments of the T-37B probe aircraft. Idle thrust also increased the strength of the B-747 wake vortexes with both inboard and outboard flaps extended.
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    Subject Category: 01
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    Report Date: April 1975
    No. Pages: 23
    Keywords:      Aircraft wakes; Boeing 747 aircraft; Flight tests; Flow characteristics; Rolling moments.


  21. COMPARISONS OF WING PRESSURE DISTRIBUTION FROM FLIGHT TESTS OF FLUSH AND EXTERNAL ORIFICES FOR MACH NUMBERS FROM 0.50 TO 0.97 , Technical Memorandum
    Authors: L. C. Montoya and D. P. Lux
    Report Number: NASA-TM-X-56032
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: Wing pressure distributions obtained in flight with flush orifice and external tubing orifice installations for Mach numbers from 0.50 to 0.97 are compared. The procedure used to install the external tubing orifice is discussed. The results indicate that external tubing orifice installations can give useful results.
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    Subject Category: 02
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    Report Date: April 1975
    No. Pages: 26
    Keywords:      Flight tests; Mach number; Orifices; Pressure distribution; Wings.


  22. STATUS OF A DIGITAL INTEGRATED PROPULSION/FLIGHT CONTROL SYSTEM FOR THE YF-12 AIRPLANE , Conference Paper
    Authors: P. J. Reukauf, F. W. Burcham, Jr. and J. K. Holzman
    Report Number: H-891
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: The NASA Flight Research Center is engaged in a program with the YF-12 airplane to study the control of interactions between the airplane and the propulsion system. The existing analog air data computer, autothrottle, autopilot, and inlet control system are to be converted to digital systems by using a general purpose airborne computer and interface unit. First, the existing control laws will be programmed in the digital computer and flight tested. Then new control laws are to be derived from a dynamic propulsion model and a total force and moment aerodynamic model to integrate the systems. These control laws are to be verified in a real time simulation and flight tested.
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    Report Date: September 1975
    No. Pages: 9
    Keywords:      Airborne/spaceborne computers; Aircraft control; Digital systems; Engine control; Flight control.
    Notes: American Institute of Aeronautics and Astronautics and Society of Automotive Engineers, Propulsion Conference, 11th, Anaheim, Calif., Sept. 29-Oct. 1, 1975. AIAA Paper 75-1180.


  23. TECHNIQUES FOR DETERMINING PROPULSION SYSTEM FORCES FOR ACCURATE HIGH SPEED VEHICLE DRAG MEASUREMENTS IN FLIGHT , Conference Paper
    Authors: H. H. Arnaiz
    Report Number: H-893
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: As part of a NASA program to evaluate current methods of predicting the performance of large, supersonic airplanes, the drag of the XB-70 airplane was measured accurately in flight at Mach numbers from 0.75 to 2.5. This paper describes the techniques used to determine engine net thrust and the drag forces charged to the propulsion system that were required for the in-flight drag measurements. The accuracy of the measurements and the application of the measurement techniques to aircraft with different propulsion systems are discussed. Examples of results obtained for the XB-70 airplane are presented.
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    Report Date: August 1975
    No. Pages: 14
    Keywords:      Aircraft engines; Drag measurement; Flight tests; Propulsion system performance; Supersonic drag.
    Notes: American Institute of Aeronautics and Astronautics, Aircraft Systems and Technology Meeting, Los Angeles, Calif., Aug. 4-7, 1975. AIAA Paper 75-964.


  24. REVIEW OF AIRCRAFT NOISE PROPAGATION , Technical Memorandum
    Authors: T. W. Putnam
    Report Number: NASA-TM-X-56033
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: The current state of knowledge about the propagation of aircraft noise was reviewed. The literature on the subject is surveyed and methods for predicting the most important and best understood propagation effects are presented. Available empirical data are examined and the data's general validity is assessed. The methods used to determine the loss of acoustic energy due to uniform spherical spreading, absorption in a homogeneous atmosphere, and absorption due to ground cover are presented. A procedure for determining ground induced absorption as a function of elevation angle between source and receiver is recommended. Other factors that affect propagation, such as refraction and scattering due to turbulence, which were found to be less important for predicting the propagation of aircraft noise, are also evaluated.
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    Subject Category: 07
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    Report Date: September 1975
    No. Pages: 60
    Keywords:      Aircraft noise; Atmospheric scattering; Noise propagation; Turbulence.


  25. RESULTS OF NASTRAN MODAL ANALYSES AND GROUND VIBRATION TESTS ON THE YF-12A AIRPLANE , Conference Paper
    Authors: E. E. Kordes and A. R. Curtis
    Report Number: H-897
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: The YF-12A aircraft, a delta-winged vehicle powered by two jet engines, was utilized in an investigation of the structural dynamic characteristics of a large, flexible, supersonic research vehicle. A large NASA structural analysis (NASTRAN) finite-element model was used to compute the ten lowest frequency symmetric and ten lowest frequency antisymmetric modes for the YF-12A aircraft. The results of the analysis were compared with experimental data obtained in a ground vibration test conducted with the completed aircraft. It was found that the finite-element structural model employed provides an adequate prediction of the dynamic behavior of the aircraft structure in the case of basic wing and body modes.
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    Subject Category: 05
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    Report Date: November 1975
    No. Pages: 25
    Keywords:      Body-wing configurations; Dynamic structural analysis; Ground tests; NASTRAN; Vibration tests.
    Notes: American Society of Mechanical Engineers, Winter Annual Meeting, Houston, Tex., Nov. 30-Dec. 4, 1975. ASME Paper 75-WA/AERO-8.


  26. FLIGHT-DETERMINED STABILITY AND CONTROL DERIVATIVES FOR AN EXECUTIVE JET TRANSPORT , Technical Memorandum
    Authors: H. J. Smith
    Report Number: NASA-TM-X-56034
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: A modified maximum likelihood estimation (MMLE) technique which included a provision for including a priori information about unknown parameters was used to determine the aerodynamic derivatives of the Lockheed JetStar airplane. Two hundred sixty-five maneuvers were performed with the JetStar airplane, which was modified to include direct lift controls, to obtain lateral-directional and longitudinal derivatives. Data were obtained at altitudes of 3048 meters, 6096 meters, and 9144 meters (10,000 feet, 20,000 feet, and 30,000 feet) and over an angle of attack range from approximately 3 deg to 13 deg and a Mach number range from 0.25 to 0.75. Side force generators were installed and tested in 87 maneuvers to determine their effectiveness and their effect on the other derivatives. Lateral-directional data for four flight conditions were analyzed without using a priori information to assess the effect of this feature on the results. The MMLE method generally gave consistent (repeatable) estimates of the derivatives, with the exception of the rolling moment due to yaw rate, which showed large variances.
    Distribution/Availability: Unclassified - Unlimited
    Subject Category: 08
    Availability:
        Format(s) on-line:
          PDF (1,399 KBytes)
    Report Date: July 1975
    No. Pages: 47
    Keywords:      Aircraft control; Control equipment; Control stability; Flight stability tests; Jet aircraft.


  27. STABILITY AND CONTROL DERIVATIVES OF THE T-37B AIRPLANE , Technical Memorandum
    Authors: M. F. Shafer
    Report Number: NASA-TM-X-56036
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: Subsonic stability and control derivatives were determined by a modified maximum likelihood estimator from flight data for the longitudinal and lateral-directional modes of the T-37B airplane. Data from two flights, in which 166 stability and control maneuvers were performed, were used in the determination. The configurations investigated were: zero flaps, gear up; half flaps, gear up; full flaps, gear up; and zero flaps, gear down.
    Distribution/Availability: Unclassified - Unlimited
    Subject Category: 08
    Availability:
        Format(s) on-line:
          PDF (1,108 KBytes)
    Report Date: September 1975
    No. Pages: 32
    Keywords:      Aircraft maneuvers; Control stability; Lateral stability; Stability derivatives; T-37 aircraft.


  28. MEASURED NOISE REDUCTIONS RESULTING FROM MODIFIED APPROACH PROCEDURES FOR BUSINESS JET AIRCRAFT , Technical Memorandum
    Authors: F. W. Burcham, Jr., T. W. Putnam, P. L. Lasagna and O. O. Parish
    Report Number: NASA-TM-X-56037
    Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
    Abstract: Five business jet airplanes were flown to determine the noise reductions that result from the use of modified approach procedures. The airplanes tested were a Gulfstream 2, JetStar, Hawker Siddeley 125-400, Sabreliner-60 and LearJet-24. Noise measurements were made 3, 5, and 7 nautical miles from the touchdown point. In addition to a standard 3 deg glide slope approach, a 4 deg glide slope approach, a 3 deg glide slope approach in a low-drag configuration, and a two-segment approach were flown. It was found that the 4 deg approach was about 4 EPNdB quieter than the standard 3 deg approach. Noise reductions for the low-drag 3 deg approach varied widely among the airplanes tested, with an average of 8.5 EPNdB on a fleet-weighted basis. The two-segment approach resulted in noise reductions of 7 to 8 EPNdB at 3 and 5 nautical miles from touchdown, but only 3 EPNdB at 7 nautical miles from touchdown when the airplanes were still in level flight prior to glide slope intercept. Pilot ratings showed progressively increasing workload for the 4 deg, low-drag 3 deg, and two-segment approaches.
    Distribution/Availability: Unclassified - Unlimited
    Subject Category: 71
    Availability:
        Format(s) on-line:
          PDF (1,116 KBytes)
    Report Date: November 1975
    No. Pages: 31
    Keywords:      Aerodynamic noise; Approach control; Commercial aircraft; Jet aircraft noise; Noise reduction.
 
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