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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 271 records · Page 15

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NASA NTRS1978

Implementation of an optimum profile guidance system on STOLAND

The implementation on the STOLAND airborne digital computer of an optimum profile guidance system for the augmentor wing jet STOL research aircraft is described. Major tasks were to implement the guidance and control logic to airborne computer software and to integrate the module with the existing STOLAND navigation, display, and autopilot routines. The optimum profile guidance system comprises an algorithm for synthesizing mimimum fuel trajectories for a wide range of starting positions in the terminal area and a control law for flying the aircraft automatically along the trajectory. The avionics software developed is described along with a FORTRAN program that was constructed to reflect the modular nature and algorthms implemented in the avionics software.

Flanagan, P. F.↗

NASA NTRS1978

Engineering description of the OMS/RCS/DAP modes used in the HP-9825A High Fidelity Relative Motion Program (HFRMP)

Simplified mathematical models are reported for the space shuttle's Orbital Maneuvering System (OMS), Reaction Control System (RCS), and on-orbit Digital Autopilot (DAP) that have been incorporated in the High-Fidelity Relative Motion Program (HFRMP) for the HP-9825A desk-top calculator. Comparisons were made between data generated by the HFRMP and by the Space Shuttle Functional Simulator (SSFS), which models the cited shuttle systems in much greater detail. These data include propellant requirements for representative translational maneuvers, rotational maneuvers, and attitude maintenance options. Also included are data relating to on-orbit trajectory deviations induced by RCS translational cross coupling. Potential close-range stationkeeping problems that are suggested by HFRMP simulations of 80 millisecond (as opposed to 40 millisecond) DAP cycle effects are described. The principal function of the HFRMP is to serve as a flight design tool in the area of proximity operations.

Wilson, S. W.↗

NASA NTRS1979

The Look-point Aircraft Coordinate Estimator (LACE) and potential applications

A look-point aircraft coordinate estimator (LACE) consisting of a windshield runway symbol projector, pilot input controls, microprocessor, and eye-alignment device is described. The estimator is used by a pilot to determine his aircraft's position relative to a runway or other visible terrain or target. The pilot initially superimposes and then corrects the superposition of the runway symbol over the runway during approach during periods when the runway is visible. Using the pilot's inputs the microprocessor calculates the position of the aircraft in terms of runway coordinates, then generates an approach trajectory and issues instructions to an autopilot. The microprocessor contains a model of the aircraft's dynamics and calculates a theoretical aircraft trajectory. The theoretical position of the aircraft is then used to drive the runway symbol, with the pilot's input being additive. The system thus acts as an aid in making low visibility approaches and landings when only an occasional glimpse of the runway is possible and no ground referenced landing systems are available. The system can also be used as an independent landing monitor for ground referenced landing systems.

Anderson, W. W.↗

NASA NTRS1979

Capturing and tracking performance of the horizontal guidance and control systems of the terminal configured vehicle

A twin-jet commercial transport equipped with digital navigation, guidance, and control systems and advanced electronic display system was used for airborne operational research. The results of flight tests which evaluated a second-order horizontal-path guidance control law and the autopilot and airplane response are presented. This evaluation was accomplished through analysis of recorded flight data and through pilot opinion of the airplane maneuvers during automatic path-capture scenarios and path tracking. Four different path captures were flown at a ground speed of approximately 160 knots and repeated at approximately 300 knots. Path tracking tracking error was measured in terms of cross track error along two paths: one pat at cruise speeds and one at airport-terminal-area speeds. The path tracking accuracy and the smoothness of the airplane maneuvers were judged satisfactory for high speeds; however, at lower speeds the control law design should be improved so that tracking will be more accurate for operations in the airport terminal area.

Knox, C. E.↗

NASA NTRS1978

Flight management research utilizing an oculometer

This paper presents an overview of the flight management work being conducted using NASA Langley's oculometer system. Tests have been conducted in a Boeing 737 simulator to investigate pilot scan behavior during approach and landing for simulated IFR, VFR, motion versus no motion, standard versus advanced displays, and as a function of various runway patterns and symbology. Results of each of these studies are discussed. For example, results indicate that for the IFR approaches a difference in pilot scan strategy was noted for the manual versus coupled (autopilot) conditions. Also, during the final part of the approach when the pilot looks out-of-the-window he fixates on his aim or impact point on the runway and holds this point until flare initiation.

Spady, A. A., Jr.↗

NASA NTRS1979

Advanced transport operation effects on pilot scan patterns

Long straight-in and close-in, curved, descending instrument approaches were made in NASA's fixed-base Terminal Configured Vehicle simulator. The pilot either manually controlled the simulator or monitored the automatic system control of the simulated aircraft during the approach. Tests were performed with or without the display of traffic. The results indicate that the pilots' use of the Electronic Horizontal Situation Indicator (EHSI) increased appreciably for the close-in, curved, descending approach compared to the conventional straight-in approach. When operating as a monitor of the autopilot system, the pilot scanned around more with less attention devoted to the Electronic Attitude Direction Indicator (EADI). The pilots preferred the manual mode because it kept them in the control loop. The addition of displayed traffic to the EHSI increased the pilots' use of the EHSI with a corresponding reduction in his use of the EADI. Also, the pilot's pupil diameter increased during the landing flare indicating a higher stress level even though the tests were conducted in a fixed-base simulator.

Harris, R. L., Sr.↗

NASA NTRS1980

Electrofluidic accelerometer

Electrofluidic accelerometer senses components of linear and angular acceleration field. Typical application of such acceleration is as active controlling element in airplane autopilot. In contrast to conventional accelerometers, electrofluidic accelerometer is lightweight, small, inexpensive, rugged, and requires little power. It consists of two temperature sensors on opposite sides of heating element. Sensors detect temperature gradient created by acceleration field on fluid; when device is accelerated, gradient changes because of bouyant force on hotter (thus lighter) portion of fluid.

Hewes, D. E.↗

NASA NTRS1980

MCC level C formulation requirements. Shuttle TAEM guidance and flight control, STS-1 baseline

The TAEM guidance and body rotational dynamics models required for the MCC simulation of the TAEM mission phase are defined. This simulation begins at the end of the entry phase and terminates at TAEM autoland interface. The logic presented is the required configuration for the first shuttle orbital flight (STS-1). The TAEM guidance is simulated in detail. The rotational dynamics simulation is a simplified model that assumes that the commanded rotational rates can be achieved in the integration interval. Thus, the rotational dynamics simulation is essentially a simulation of the autopilot commanded rates and integration of these rates to determine orbiter attitude. The rotational dynamics simulation also includes a simulation of the speedbrake deflection. The body flap and elevon deflections are computed in the orbiter aerodynamic simulation.

Carman, G. L.↗

NASA NTRS1980

Analysis of space shuttle orbiter entry dynamics from Mach 10 to Mach 2.5 with the November 1976 flight control system

A six-degree-of-freedom simulation analysis was performed for the space shuttle orbiter entry from Mach 10 to Mach 2.5 with realistic off-nominal conditions using the flight control system referred to as the November 1976 Integrated Digital Autopilot. The off-nominal conditions included: (1) aerodynamic uncertainties in extrapolating from wind tunnel of flight characteristics, (2) error in deriving angle of attack from onboard instrumentation, (3) failure of two of the four reaction control-system thrusters on each side (design specification), and (4) lateral center-of-gravity offset. Many combinations of these off-nominal conditions resulted in a loss of the orbiter. Control-system modifications were identified to prevent this possibility.

Powell, R. W.↗

NASA NTRS1980

Development of the reentry flight dynamics simulator for evaluation of space shuttle orbiter entry systems

A nonlinear, six degree of freedom, digital computer simulation of a vehicle which has constant mass properties and whose attitudes are controlled by both aerodynamic surfaces and reaction control system thrusters was developed. A rotating, oblate Earth model was used to describe the gravitational forces which affect long duration Earth entry trajectories. The program is executed in a nonreal time mode or connected to a simulation cockpit to conduct piloted and autopilot studies. The program guidance and control software used by the space shuttle orbiter for its descent from approximately 121.9 km to touchdown on the runway.

Rowell, L. F.↗

NASA NTRS1980

Effects of magnification and visual accommodation on aimpoint estimation in simulated landings with real and virtual image displays

Twenty professional pilots observed a computer-generated airport scene during simulated autopilot-coupled night landing approaches and at two points (20 sec and 10 sec before touchdown) judged whether the airplane would undershoot or overshoot the aimpoint. Visual accommodation was continuously measured using an automatic infrared optometer. Experimental variables included approach slope angle, display magnification, visual focus demand (using ophthalmic lenses), and presentation of the display as either a real (direct view) or a virtual (collimated) image. Aimpoint judgments shifted predictably with actual approach slope and display magnification. Both pilot judgments and measured accommodation interacted with focus demand with real-image displays but not with virtual-image displays. With either type of display, measured accommodation lagged far behind focus demand and was reliably less responsive to the virtual images. Pilot judgments shifted dramatically from an overwhelming perceived-overshoot bias 20 sec before touchdown to a reliable undershoot bias 10 sec later.

Randle, R. J.↗

NASA NTRS1980

Pilot-aircraft system response to wind shear

The nonlinear aircraft motion and automatic control computer model of Frost and Reddy has been expanded to incorporate the human pilot into simulations of aircraft response to wind shear. Fixed-stick, autopilot, and manned computer simulations are made with an aircraft having characteristics of a Queen Air (small commuter-type aircraft) flown through longitudinal winds measured by a Doppler radar beamed along the glide slope during the SESAME '79 experiments in Oklahoma. Simulations are also made flying a model Boeing 727 through sinusoidal head wind to tail wind shears at the phugoid frequency to evaluate the response of manned aircraft in thunderstorm wind environments.

Turkel, B. S.↗

NASA NTRS1982

Analyzing Multirate-Sampled Systems

New method available for monitoring stability of system on basis of data sampled at multiple rates--in particular, at two rates, one of which is twice frequency of other. Method is called Multirate Matrix Frequency Response (MMFR) analysis. MMFR was used in Space Shuttle to evaluate effect of decreasing sample rate of error loop in ascent-phase digital autopilot. Should also be useful to designers of other control systems and to structural, civil, and mechanical engineers for structure and vibration analysis.

Hendrix, N.↗

NASA NTRS1980

Pilot-aircraft system reponse to wind shear

The nonlinear aircraft motion and automatic control model is expanded to incorporate the human pilot into simulations of aircraft response to wind to wind shear. The human pilot is described by a constant gains lag filter. Two runs are carried out using pilot transfer functions. Fixed-stick, autopilot, and manned computer simulations are made with an aircraft having characteristics of a small commuter type aircraft flown through longitudinal winds measured by a Doppler radar beamed along the glide slope. Simulations are also made flying an aircraft through sinusoidal head wind and tail wind shears at the phugoid frequency to evaluate the response of manned aircraft in thunderstorm wind environments.

Turkel, B. S.↗

NASA NTRS1980

YF-12 cooperative airframe/propulsion control system program, volume 1

Several YF-12C airplane analog control systems were converted to a digital system. Included were the air data computer, autopilot, inlet control system, and autothrottle systems. This conversion was performed to allow assessment of digital technology applications to supersonic cruise aircraft. The digital system was composed of a digital computer and specialized interface unit. A large scale mathematical simulation of the airplane was used for integration testing and software checkout.

Anderson, D. L.↗

NASA NTRS1981

The NASA digital VGH program, early results

Data from airline digital flight data recorders provides relevant statistical data for estimating fatigue life consumption of the current airliner fleet and for design criteria updating for future designs. The data indicates real operating effects due to the autopilot, i.e., gust response frequency peak increase by 2 or 3 times, and the existence of the low frequency low amplitude limit cycle motion in altitude hold. The extension of more data types for ground operations is considered. Onboard processing of simple data types is also considered.

Crabill, N. L.↗

NASA NTRS1981

Fixed-trim re-entry guidance analysis

The terminal guidance problem for a fixed-trim re-entry body is formulated with the objective of synthesizing a closed-loop steering law. A transformation of variables and subsequent linearization of the motion, with the sight-line to the target as a reference, reduces the order of the state system for the guidance problem. The reduced order system, although nonlinear and time-varying, is simple enough to lend itself to synthesis of a class of guidance laws. A generalization of the feedforward device of classical control theory is successfully employed for compensation of roll autopilot lags. The proposed steering law exhibits superior miss-distance performance in a computational comparison with existing fixed-trim guidance laws.

Gracey, C.↗

NASA NTRS1983

Flexible Aircraft Takeoff and Landing Analysis

Flexible Aircraft Takeoff and Landing Analysis Program, FATOLA, simulates aircraft takeoff and landing dynamics. Program includes maneuver logic and autopilots for glide slope, flare, landing, and takeoff and is modular so performance of aircraft in flight and during landing and ground maneuvers can be studied separately or in combination.

Carden, H. D.↗