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At least 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Estimation of characteristics and stochastic control of an aircraft flying in atmospheric turbulence

An adaptive control technique to improve the flying qualities of an aircraft in turbulence was investigated. The approach taken was to obtain maximum likelihood estimates of the unknown coefficients of the aircraft system and then, using these estimates along with the separation principle, to define the stochastic optimal control. The maximum likelihood estimation technique that accounted for the effects of turbulence provided good estimates of the unknown coefficients and of the turbulence. The assessment of the stochastic optimal control based on the maximum likelihood estimates showed that the desired effects were attained for the regulator problem of minimizing pitch angle and the tracking problem of requiring normal acceleration to follow the pilot input.

Iliff, K. W.↗
NASA NTRS1976

Design and test experience with a triply redundant digital fly-by-wire control system

A triplex digital fly-by-wire flight control system was developed and then installed in a NASA F-8C aircraft to provide fail-operative, full authority control. Hardware and software redundancy management techniques were designed to detect and identify failures in the system. Control functions typical of those projected for future actively controlled vehicles were implemented. This paper describes the principal design features of the system, the implementation of computer, sensor, and actuator redundancy management, and the ground test results. An automated test program to verify sensor redundancy management software is also described.

Szalai, K. J.↗
NASA NTRS1976

Design of active controls for the NASA F-8 digital fly-by-wire airplane

The design of a set of control laws for the NASA F-8 digital fly by wire research airplane is described. These control laws implement several active controls functions: maneuver load control, ride smoothing and departure boundary limiting. The criteria and methods which were used in the design of the control laws are also included. Results of linear analyses and nonlinear simulation are summarized.

Gera, J.↗
NASA NTRS1976

Remote sensing for control of tsetse flies

Remotely sensed information is discussed which has potential for aiding in the control or eradication of tsetse flies. Data are available from earth resources meteorological, and manned satellites, from airborne sensors, and possibly from data collection platforms. A new zone discrimination technique, based on data from meteorological satellites may also allow the identification of zones hospitable to one or another species of tsetse. For background, a review is presented of the vegetation of Tanzania and Zanzibar, and illustrations presented of automatic processing of data from these areas. In addition, a review is presented of the applicability of temperature data to tsetse areas.

Giddings, L. E.↗
NASA NTRS1977

Formation flying benefits based on vortex lattice calculations

A quadrilateral vortex-lattice method was applied to a formation of three wings to calculate force and moment data for use in estimating potential benefits of flying aircraft in formation on extended range missions, and of anticipating the control problems which may exist. The investigation led to two types of formation having virtually the same overall benefits for the formation as a whole, i.e., a V or echelon formation and a double row formation (with two staggered rows of aircraft). These formations have unequal savings on aircraft within the formation, but this allows large longitudinal spacings between aircraft which is preferable to the small spacing required in formations having equal benefits for all aircraft. A reasonable trade-off between a practical formation size and range benefit seems to lie at about three to five aircraft with corresponding maximum potential range increases of about 46 percent to 67 percent. At this time it is not known what fraction of this potential range increase is achievable in practice.

Maskew, B.↗
NASA NTRS1976

Estimated transonic flying qualities of a tailless airplane based on a model investigation, 8 June 1949

Flying qualities of a tailless airplane with the wing quarter chord line swept back 35 deg were analyzed in the Mach number range from 0.40 to 0.91 based on tests of a model of this airplane in the Langley high speed 7 by 10 foot tunnel. The results indicate that longitudinal control position instability exists at transonic speeds but the accompanying trim changes are not large. Control position maneuvering stability, however, is present for all speeds. Longitudinal and lateral control appear adequate, but the damping of the short period longitudinal and lateral oscillations at high altitudes is poor and would probably require artificial damping.

Donlan, C. J.↗
NASA NTRS1977

Probabilities of good, marginal, and poor flying conditions for space shuttle ferry flights

Empirical probabilities are provided for good, marginal, and poor flying weather for ferrying the Space Shuttle Orbiter from Edwards AFB, California, to Kennedy Space Center, Florida, and from Edwards AFB to Marshall Space Flight Center, Alabama. Results are given by month for each overall route plus segments of each route. The criteria for defining a day as good, marginal, or poor and the method of computing the relative frequencies and conditional probabilities for monthly reference periods are described.

Whiting, D. M.↗
NASA NTRS1976

Observations of Jupiter's radio emission at 327 MHz and 1410 MHz during the Pioneer 11 fly-by

During the 1974 fly-by of Jupiter by the Pioneer 11 spacecraft, radio observations were carried out daily at 327 and 1410 MHz for a period of 60 days centered on December 3, 1974, the day of closest approach to Jupiter. The 1410-MHz data reveal two significant short-term variations in the Jovian radio emission; the largest one is probably present also at 327 MHz although Faraday rotation in earth's ionosphere could have affected the data. The two radio bursts appear to be correlated with two long-duration electron bursts observed in the energy ranges from 2 to 7 and 6 to 30 MeV.

Kundu, M. R.↗
NASA NTRS1976

NASA's advanced control law program for the F-8 Digital Fly-By-Wire aircraft

This paper briefly describes the NASA F-8 Digital Fly-By-Wire (DFBW) program and Langley Research Center's role in investigating and promoting advanced control laws for possible flight experimentation. The primary purpose of the paper is to provide background material for papers describing some of the F-8 DFBW adaptive control law studies. The paper provides a brief description of the Phase II DFBW F-8 aircraft and its control system, discusses some of the advanced control law study objectives and guidelines, and provides some mathematical models which are useful in the control analysis problem.

Elliott, J. R.↗
NASA NTRS1977

NAVTOLAND and flying qualities

The V/STOL operational capability is reviewed with emphasis on pilot workload and all-weather landing guidance systems. A research and development program to correlate and integrate the development of all systems and techniques involved in enabling the pilot to fly V/STOL aircraft onto ships and tactical sites is described. Aircraft design parameters that affect its control in the vertical takeoff and landing flight regimes are emphasized. Topics considered include: (1) integrated flight controls and displays; (2) low speed sensor; (3) air traffic control appraoch and landing guidance systems; (4) visual landing aids; (5) ground effect induced thrust variation problems; and (6) handling qualities.

Momiyama, T. S.↗
NASA NTRS1977

Flight experience with a fail-operational digital fly-by-wire control system

The NASA Dryden Flight Research Center is flight testing a triply redundant digital fly-by-wire (DFBW) control system installed in an F-8 aircraft. The full-time, full-authority system performs three-axis flight control computations, including stability and command augmentation, autopilot functions, failure detection and isolation, and self-test functions. Advanced control law experiments include an active flap mode for ride smoothing and maneuver drag reduction. This paper discusses research being conducted on computer synchronization, fault detection, fault isolation, and recovery from transient faults. The F-8 DFBW system has demonstrated immunity from nuisance fault declarations while quickly identifying truly faulty components.

Brown, S. R.↗
NASA NTRS1977

NASA's advanced control law program for the F-8 digital fly-by-wire aircraft

This paper briefly describes the NASA F-8 Digital Fly-By-Wire (DFBW) and Langley Research Center's role in investigating and promoting advanced control laws for possible flight experimentation and also provides a brief description of the Phase II DFBW F-8 aircraft and its control system. Some of the advanced control law study objectives and guidelines are discussed, and some mathematical models which are useful in the control analysis problem are provided.

Elliott, J. R.↗
NASA NTRS1978

The flying hot wire and related instrumentation

A flying hot-wire technique is proposed for studies of separated turbulent flow in wind tunnels. The technique avoids the problem of signal rectification in regions of high turbulence level by moving the probe rapidly through the flow on the end of a rotating arm. New problems which arise include control of effects of torque variation on rotor speed, avoidance of interference from the wake of the moving arms, and synchronization of data acquisition with rotation. Solutions for these problems are described. The self-calibrating feature of the technique is illustrated by a sample X-array calibration.

Coles, D.↗
NASA NTRS1978

Technical problems encountered with the LALA-1 flying laboratory

A description is given of structural design changes necessitated by the conversion of the An-2R agricultural support aircraft into a flying test bed to be used in feasibility studies evaluating jet engines in agricultural support aircraft. The entire rear of the fuselage was radically modified to permit mounting of the Al-25 jet engine directly behind the trailing edge of the upper wing. The standard piston engine was retained to permit comparison between the two types of power plants in typical agricultural support operations.

Swidzinski, J.↗
NASA NTRS1978

Digital Fly-By-Wire Flight Control Validation Experience

The experience gained in digital fly-by-wire technology through a flight test program being conducted by the NASA Dryden Flight Research Center in an F-8C aircraft is described. The system requirements are outlined, along with the requirements for flight qualification. The system is described, including the hardware components, the aircraft installation, and the system operation. The flight qualification experience is emphasized. The qualification process included the theoretical validation of the basic design, laboratory testing of the hardware and software elements, systems level testing, and flight testing. The most productive testing was performed on an iron bird aircraft, which used the actual electronic and hydraulic hardware and a simulation of the F-8 characteristics to provide the flight environment. The iron bird was used for sensor and system redundancy management testing, failure modes and effects testing, and stress testing in many cases with the pilot in the loop. The flight test program confirmed the quality of the validation process by achieving 50 flights without a known undetected failure and with no false alarms.

Szalai, K. J.↗
NASA NTRS1979

Effect on head-wind profiles and mean head-wind velocity on landing capacity flying constant-airspeed and constant-groundspeed approaches

A study was conducted to determine the effect of head-wind profiles and mean head-wind velocities on runway landing capacity for airplanes flying constant-airspeed and constant-groundspeed approaches. It was determined that when the wind profiles were encountered with the currently used constant airspeed approach method, the landing capacity was reduced. The severity of these reductions increased as the mean head-wind value of the profile increased. When constant-groundspeed approaches were made in the same wind profiles, there were no losses in landing capacity. In an analysis of mean head winds, it was determined that in a mean head wind of 35 knots, the landing capacity using constant-airspeed approaches was 13% less than for the no wind condition. There were no reductions in landing capacity with constant-groundspeed approaches for mean head winds less than 35 knots. This same result was observed when the separation intervals between airplanes was reduced.

Hastings, E. C., Jr.↗