The effect of a light aircraft stability augmentation system on pilot performance.
Light aircraft lateral stability augmentation system for wing leveling, noting operation and pilot performance
STABILITY AUGMENTATION↗
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Flight test experience with high-alpha control system techniques on the F-14 airplane
Improved handling qualities of fighter aircraft at high angles of attack can be provided by various stability and control augmentation techniques. NASA and the U.S. Navy are conducting a joint flight demonstration of these techniques on an F-14 airplane. This paper reports on the flight test experience with a newly designed lateral-directional control system which suppresses such high angle of attack handling qualities problems as roll reversal, wing rock, and directional divergence while simultaneously improving departure/spin resistance. The technique of integrating a piloted simulation into the flight program was used extensively in this program. This technique had not been applied previously to high angle of attack testing and required the development of a valid model to simulate the test airplane at extremely high angles of attack.
Gera, J.↗
A Concept of a Manned Satellite Reentry Which is Completed with a Glide Landing
A concept for a manned satellite reentry from a near space orbit and a glide landing on a normal size airfield is presented. The reentry vehicle configuration suitable for this concept would employ a variable geometry feature in order that the reentry could be made at 90 deg. angle of attack and the landing could be made with a conventional glide approach. Calculated results for reentry at a flight-path angle of -1 deg. show that with an accuracy of 1 percent in the impulse of a retrorocket, the desired flight-path angle at reentry can be controlled within 0.02 deg. and the distance traveled to the reentry point, within 100 miles. The reentry point is arbitrarily defined as the point at which the satellite passes through an altitude of about 70 miles. Misalignment of the retrorocket by 10 deg. increased these errors by as much as 0.02 deg. and 500 miles. Intra-atmospheric trajectory calculations show that pure drag reentries starting with flight-path angles of -1 deg. or less produce a peak deceleration of 8g. Lift created by varying the angle of attack between 90 and 60 deg. is effective in decreasing the maximum deceleration and allows the range to the "recovery" point (where transition is made from reentry to gliding flight) to be increased by as much as 2,300 miles. A sideslip angle of 30 deg. allows lateral displacement of the flight path by as much as 60 deg. miles. Reaction controls would provide control-attitude alignment during the orbit phase. For the reentry phase this configuration should have low static longitudinal and roll stability in the 90 deg. angle-of-attack attitude. Control could be effected by leading-edge and trailing-edge flaps. Transition into the landing phase would be accomplished at an altitude of about 100,000 feet by unfolding the outer wing panels and pitching over to low angles of attack. Calculations indicate that glides can be made from the recovery point to airfields at ranges of from 150 to 200 miles, depending upon the orientation with respect to the original course.
Cheatham, Donald C.↗
Aerodynamic Performance and Flow-Field Characteristics of Two Waverider-Derived Hypersonic Cruise Configurations
The component integration of a class of hypersonic high-lift configurations known as waveriders into hypersonic cruise vehicles was evaluated. A wind-tunnel model was developed which integrates realistic vehicle components with two waverider shapes, referred to as the straight-wing and cranked-wing shapes. Both shapes were conical-flow-derived waveriders for a design Mach number of 4.0. Experimental data and limited computational fluid dynamics (CFD) predictions were obtained over a Mach number range of 1.6 to 4.63 at a Reynolds number of 2.0 x 10(exp 6) per foot. The CFD predictions and flow visualization data confirmed the shock attachment characteristics of the baseline waverider shapes and illustrated the waverider flow-field properties. Experimental data showed that no significant performance degradations, in terms of maximum lift-to-drag ratios, occur at off-design Mach numbers for the waverider shapes and the integrated configurations. A comparison of the fully-integrated waverider vehicles to the baseline shapes showed that the performance was significantly degraded when all of the components were added to the waveriders, with the most significant degradation resulting from aftbody closure and the addition of control surfaces. Both fully-integrated configurations were longitudinally unstable over the Mach number range studied with the selected center of gravity location and for unpowered conditions. The cranked-wing configuration provided better lateral-directional stability characteristics than the straight-wing configuration.
Cockrell, Charles E., Jr.↗
Analysis and Design of Launch Vehicle Flight Control Systems
This paper describes the fundamental principles of launch vehicle flight control analysis and design. In particular, the classical concept of "drift-minimum" and "load-minimum" control principles is re-examined and its performance and stability robustness with respect to modeling uncertainties and a gimbal angle constraint is discussed. It is shown that an additional feedback of angle-of-attack or lateral acceleration can significantly improve the overall performance and robustness, especially in the presence of unexpected large wind disturbance. Non-minimum-phase structural filtering of "unstably interacting" bending modes of large flexible launch vehicles is also shown to be effective and robust.
Wie, Bong↗
The Tidbinbilla interferometer
A proposal to operate a two element interferometer using the 64 m and 26 m antennas of the Tidbinbilla Deep Space Station is discussed. The instrument is to be operated as a correlation interferometer, the sine and cosine products being sampled once per second and recorded for later analysis. The receiver systems are currently under development. Preliminary measurements of the delay line and local oscillator systems and the site cables suggest that a phase stability to within about 1 deg should be achievable with temperature control of the receiver packages.
Batty, M. J.↗
Lateral control system design for VTOL landing on a DD963 in high sea states
The problem of designing lateral control systems for the safe landing of VTOL aircraft on small ships is addressed. A ship model is derived. The issues of estimation and prediction of ship motions are discussed, using optimal linear linear estimation techniques. The roll motion is the most important of the lateral motions, and it is found that it can be predicted for up to 10 seconds in perfect conditions. The automatic landing of the VTOL aircraft is considered, and a lateral controller, defined as a ship motion tracker, is designed, using optimal control techniqes. The tradeoffs between the tracking errors and the control authority are obtained. The important couplings between the lateral motions and controls are demonstrated, and it is shown that the adverse couplings between the sway and the roll motion at the landing pad are significant constraints in the tracking of the lateral ship motions. The robustness of the control system, including the optimal estimator, is studied, using the singular values analysis. Through a robustification procedure, a robust control system is obtained, and the usefulness of the singular values to define stability margins that take into account general types of unstructured modelling errors is demonstrated. The minimal destabilizing perturbations indicated by the singular values analysis are interpreted and related to the multivariable Nyquist diagrams.
Bodson, M.↗
Low-speed wind-tunnel study of the high-angle-of-attack stability and control characteristics of a cranked-arrow-wing fighter configuration
The low-speed, high-angle-of-attack stability and control characteristics of a fighter configuration incorporating a cranked arrow wing were investigated in the Langley 30- by 60-foot tunnel as part of a NASA/General Dynamics cooperative research program to investigate the application of advanced wing designs to combat aircraft. Tests were conducted on a baseline configuration and on several modified configurations. The results show that the baseline configuration exhibited a high level of maximum lift but displayed undesirable longitudinal and lateral-directional stability characteristics at high angles of attack. Various wing modifications were made which improved the longitudinal and lateral-directional stability characteristics of the configuration at high angles of attack. However, most of the modifications were detrimental to maximum lift.
Grafton, S. B.↗
An improved CAMRAD model for aeroelastic stability analysis of the XV-15 with advanced technology blades
In pursuit of higher performance, the XV-15 Tiltrotor Research Aircraft was modified by the installation of new composite rotor blades. Initial flights with the Advanced Technology Blades (ATB's) revealed excessive rotor control loads that were traced to a dynamic mismatch between the blades and the aircraft control system. The analytical models of both the blades and the mechanical controls were extensively revised for use by the CAMRAD computer program to better predict aeroelastic stability and loads. This report documents the most important revisions and discusses their effects on aeroelastic stability predictions for airplane-mode flight. The ATB's may be flown in several different configurations for research, including changes in blade sweep and tip twist. The effects on stability of 1 deg and 0 deg sweep are illustrated, as are those of twisted and zero-twist tips. This report also discusses the effects of stiffening the rotor control system, which was done by locking out lateral cyclic swashplate motion with shims.
Acree, C. W., Jr.↗
Nonlinear decoupled control synthesis for maneuvering aircraft
A control law for decoupling roll rate, angle of attack and sideslip in rapid, nonlinear airplane maneuvers is derived. For simplicity, only moments caused by ailerons, rudder and elevator are considered, and control forces are neglected. Simulated responses of the closed loop system, including the control forces, show that the neglected forces have no significant effects and that large, simultaneous lateral and longitudinal maneuvers can be precisely performed. The violent divergences which occur in open-loop maneuvers of this type are eliminated by the decoupling. The control law showed little sensitivity to 20 percent perturbation in three important stability derivatives.
Singh, S. N.↗
Exploratory study of the effects of wing-leading-edge modifications on the stall/spin behavior of a light general aviation airplane
Configurations with full-span and segmented leading-edge flaps and full-span and segmented leading-edge droop were tested. Studies were conducted with wind-tunnel models, with an outdoor radio-controlled model, and with a full-scale airplane. Results show that wing-leading-edge modifications can produce large effects on stall/spin characteristics, particularly on spin resistance. One outboard wing-leading-edge modification tested significantly improved lateral stability at stall, spin resistance, and developed spin characteristics.
Source record↗
Harnessing Chemical Short‐Range Disorder to Improve Lithium Retention in Epitaxial LLTO Solid‐Electrolyte Thin Films
Lithium lanthanum titanate Li 3x La 2/3-x TiO 3 (LLTO) is a promising perovskite-based solid-state electrolyte for next-generation lithium-ion batteries, but controlling crystallinity and Li stoichiometry in thin-film form is challenging because high growth temperatures are required to achieve good crystallinity while Li remains strongly volatile. Here, we systematically investigate the effect of substrate temperature on epitaxial LLTO thin films grown by pulsed laser deposition. We identify a narrow growth window (750–800°C) in which LLTO films grow as c-axis oriented with atomically flat surfaces. Lower growth temperatures (<750°C) stabilize laterally extended, chemically disordered stripe domains that coexist with ordered LLTO regions, whereas higher temperatures (≥825°C) suppress these defects but promote island morphologies and Al/Ti interdiffusion. While spectroscopy measurements show that Ti remains in the 4+ oxidation state and Li is globally deficient for all films, our depth-resolved time-of-flight secondary ion mass spectrometry studies reveal that the 700°C film retains the highest Li content across its thickness. These results clarify how growth temperature controls crystallinity, chemical short-range disorder, and Li retention, and highlight moderate growth temperatures (∼700°C) as a route to mitigate Li loss in epitaxial solid-electrolyte films.
chemical short-range disorder↗
Development of a HTSMA-Actuated Surge Control Rod for High-Temperature Turbomachinery Applications
In recent years, a demand for compact, lightweight, solid-state actuation systems has emerged, driven in part by the needs of the aeronautics industry. However, most actuation systems used in turbomachinery require not only elevated temperature but high-force capability. As a result, shape memory alloy (SMA) based systems have worked their way to the forefront of a short list of viable options to meet such a technological challenge. Most of the effort centered on shape memory systems to date has involved binary NiTi alloys but the working temperatures required in many aeronautics applications dictate significantly higher transformation temperatures than the binary systems can provide. Hence, a high temperature shape memory alloy (HTSMA) based on NiTiPdPt, having a transformation temperature near 300 C, was developed. Various thermo-mechanical processing schemes were utilized to further improve the dimensional stability of the alloy and it was later extruded/drawn into wire form to be more compatible with envisioned applications. Mechanical testing on the finished wire form showed reasonable work output capability with excellent dimensional stability. Subsequently, the wire form of the alloy was incorporated into a benchtop system, which was shown to provide the necessary stroke requirements of approx.0.125 inches for the targeted surge-control application. Cycle times for the actuator were limited to ~4 seconds due to control and cooling constraints but this cycle time was determined to be adequate for the surge control application targeted as the primary requirement was initial actuation of a surge control rod, which could be completed in approximately one second.
Padula, Santo, II↗
Nonlinear lift control at high speed and high angle of attack using vortex flow technology
Nonlinear lift control at subsonic, transonic and low supersonic speeds owes its origin to the separated but organized vortical flows interacting with the wing upper surface. Since most of this flow originates near the wing or control-surface leading-edge, a variety of devices have been studied experimentally which interact with and/or control this flow in order to gain a beneficial effect. The benefits (effects) originally studied were only associated with lift enhancement. Whereas, now the studied benefits encompass performance increase, attention to changes in trimmed conditions and longitudinal stability, improvements in lateral stability, and the attendant variation with changing Mach number. For those devices that can be theoretically modeled, state-of-the-art computer codes have been used for device design and/or analysis. Comparisons at design and off-design conditions are presented for validation purposes.
Lamar, J. E.↗
Nonlinear lift control at high speed and high angle of attack using vortex flow technology
Nonlinear lift control at subsonic, transonic and low supersonic speeds owes its origin to the separated but organized vortical flows interacting with the wing upper surface. Since most of this flow originates near the wing or control-surface leading edge, a variety of devices has been studied experimentally which interact with and/or control this flow in order to gain a beneficial effect. The benefits (effects) originally studied were associated only with lift enhancement. Whereas, now the studied benefits encompass performance increase, attention to changes in trimmed conditions and longitudinal stability, improvements in lateral stability, and the attendant variation with changing Mach number. For those devices that can be theoretically modeled, state-of-the-art computer codes have been used for device design and/or analysis. Comparisons at design and off-design conditions are presented for validation purposes.
Lamar, John E.↗
Experimental Aerodynamic Characteristics of an Oblique Wing for the F-8 OWRA
An experimental investigation was conducted during June-July 1987 in the NASA Ames 11-Foot Transonic Wind Tunnel to study the aerodynamic performance and stability and control characteristics of a 0.087-scale model of an F-8 airplane fitted with an oblique wing. This effort was part of the Oblique Wing Research Aircraft (OWRA) program performed in conjunction with Rockwell International. The Ames-designed, aspect ratio 10.47, tapered wing used specially designed supercritical airfoils with 0.14 thickness/chord ratio at the root and 0.12 at the 85% span location. The wing was tested at two different mounting heights above the fuselage. Performance and longitudinal stability data were obtained at sweep angles of 0deg, 30deg, 45deg, 60deg, and 65deg at Mach numbers ranging from 0.30 to 1.40. Reynolds number varied from 3.1 x 10(exp 6)to 5.2 x 10(exp 6), based on the reference chord length. Angle of attack was varied from -5deg to 18deg. The performance of this wing is compared with that of another oblique wing, designed by Rockwell International, which was tested as part of the same development program. Lateral-directional stability data were obtained for a limited combination of sweep angles and Mach numbers. Sideslip angle was varied from -5deg to +5deg. Landing flap performance was studied, as were the effects of cruise flap deflections to achieve roll trim and tailor wing camber for various flight conditions. Roll-control authority of the flaps and ailerons was measured. A novel, deflected wing tip was evaluated for roll-control authority at high sweep angles.
Kennelly, Robert A., Jr.↗
Bioinspired mineralizing microenvironments generated by liquid-liquid phase coexistence
Biominerals such as bones, teeth and shells exhibit improved mechanical properties and intricate morphologies not seen in nonbiologically-produced minerals of ostensibly the same composition. These remarkable properties of biogenic minerals are thought to arise due to precise local control over the mineral deposition process, including organic and inorganic inclusions. Understanding how Biology controls the local reaction environment during formation of these materials to control their composition, structure, and properties is a grand challenge that promises to enable new routes to high-performance materials. This project developed multi-compartment bioinspired microreactors as artificial mineralizing vesicles, and used them to understand and control formation of inorganic/organic composite solid materials. A major emphasis was on developing all-aqueous emulsions in which each droplet was a structured microreactor with two or more adjacent phases. This approach provided local control over reaction environment including availability of inclusions such as polypeptides and metal ions, while being sufficiently simple to produce large populations of essentially identical multiphase reactor droplets simultaneously within a batch. Organic/inorganic composite materials could be produced with very high organic content that stabilized the inorganic portions as amorphous materials (e.g., amorphous calcium carbonate) by preventing the typical conversion to more thermodynamically crystalline forms (e.g., calcite). These stabilized amorphous composites could be stored indefinitely and converted to crystalline forms later by removal of the organic inclusions via, for example, heating. Compositional gradients in the organic and inorganic components were embedded during synthesis due to the evolution of the reaction microenvironment, and despite the complexity of this process it occurred similarly across the population of reactive droplets and was hence encoded into the population of resulting composite particles. The approach developed here allows pre-structuring of reactive microenvironments to control the spatiotemporal reaction environment, which is an important step towards rational design and on-demand production of complex functional materials with desired composition, optical properties, and mechanical response.
36 MATERIALS SCIENCE↗
Determination of longitudinal and lateral directional aerodynamic characteristics of the B19B pressure-fed booster and the B19B booster/040A orbiter launch configuration
The 0.003366 scale models of the space shuttle pressure-fed booster and booster/orbiter configurations were tested in the MSFC 14-inch trisonic wind tunnel. The test was conducted as a static stability and control investigation over a Mach range of 0.60 to 5.00. The booster alone configuration was tested with various tail sizes, tail wedge angles, tail flaps, spoilers, and a body flare drag skirt. Two launch configurations were tested; one being the MSC orbiter location on the booster tank and the other being the North American Rockwell orbiter location. Orbiter buildup, longitudinal position, incidence angle, and booster tail on and off were the variables for launch configuration. Booster alone models were pitched over an angle of attack range of -4 to +14 and +20 to +60 deg at zero deg yaw angle and yawed over an angle of sideslip range of -10 to +10 deg at 52 deg angle of attack. Launch configuration models were yawed -10 to +10 deg at zero degrees angle of attack and yawed -10 to +10 deg at zero and -6 deg angle of attack. All models were rolled 45 deg during selected runs.
Mcginnis, R. F.↗