Engineering topics

Chambers, J. R.

Publications and source records attributed to Chambers, J. R..

At least 19 records

NASA NTRS1986

Summary of NASA stall/spin research for general aviation configurations

The major milestones of stall/spin research conducted in the past under NACA/NASA programs are reviewed, and recent results offering promise for further improvements in design methodology and concepts for stall/spin technology are identified. Specific results discussed include: (1) development and validation of test techniques and analysis methods; (2) studies of airplane spinning and spin recovery characteristics; and (3) concepts designed to increase the spin resistance of general aviation-type vehicles.

Chambers, J. R.↗

NASA NTRS1986

High-angle-of-attack aerodynamics - Lessons learned

Recently, the military and civil technical communities have undertaken numerous studies of the high angle-of-attack aerodynamic characteristics of advanced airplane and missile configurations. The method of approach and the design methodology employed have necessarily been experimental and exploratory in nature, due to the complex nature of separated flows. However, despite the relatively poor definition of many of the key aerodynamic phenomena involved for high-alpha conditions, some generic guidelines for design consideration have been identified. The present paper summarizes some of the more important lessons learned in the area of high angle-of-attack aerodynamics with examples of a number of key concepts and with particular emphasis on high-alpha stability and control characteristics of high performance aircraft. Topics covered in the discussion include the impact of design evolution, forebody flows, control of separated flows, configuration effects, aerodynamic controls, wind-tunnel flight correlation, and recent NASA research activities.

Chambers, J. R.↗

NASA NTRS1986

Technical evaluation report of AGARD Technical Evaluation Meeting on Unsteady Aerodynamics: Fundamentals and Applications to Aircraft Dynamics

From May 6 to 9, 1985, the Fluid Dynamics Panel and Flight Mechanics Panel of AGARD jointly arranged a Symposium on Unsteady Aerodynamics-Fundamentals and Applications to Aircraft Dynamics at the Stadthall, Goettingen, West Germany. This Symposium was organized by an international program committee chaired by Dr. K. J. Orlik-Ruckemann of the Fluid Dynamics Panel. The program consisted of five sessions grouped in two parts: (1) Fundamentals of Unsteady Aerodynamics; and (2) Applications to Aircraft Dynamics. The 35 papers presented at the 4 day meeting are published in AGARD CP 386 and listed in the Appendix. As the papers are already available and cover a very wide field, the evaluators have offered brief comments on every paper, followed by an overall evaluation of the meeting, together with some general conclusions and recommendations.

Mabey, D. G.↗

NASA NTRS1984

Aerodynamic characteristics of two general aviation canard configurations at high angles of attack

The results of wind tunnel tests of two propeller driven canard general aviation aircraft models at high angles of attack are reported. Both tractor and pusher prop configurations were examined. Angles of attack of -6 to 40 deg were used with the pusher model at Re of 1,600,000, and from -30 to 90 deg and Re of 550,000 for the tractor model. The tests showed that the canard would stall long before the wing and produce a nose-down tendency, thus effectively keeping the aircraft out of the stall regime. However, a sequence of pilot actions or design factors such as the airfoils, relative geometry of the canard and wing, the propeller location and the center of gravity location could introduce a wide variance in stall characteristics from one aircraft to another.

Chambers, J. R.↗

NASA NTRS1984

Wind-Tunnel Investigation of an Advanced General Aviation Canard Configuration

Wind-tunnel tests of a model of an advanced canard configuration designed for general aviation were conducted in the Langley 30- by 60-Foot Tunnel. The objective of the tests was to determine the aerodynamic stability and control characteristics of the configuration for a large range of angles of attack and sideslip at several power conditions. Analysis of the aerodynamic data indicates significant effects of power and of center-of-gravity location. For forward center-of-gravity locations, the configuration had extremely stall-resistant stability and control characteristics. For aft center-of-gravity locations and high-power conditions, the combined effects of increased pitch control and reduced longitudinal stability overpowered the stall resistance provided by the canard, which led to a high-angle-of-attack, deep-stall trim condition. Other aspects of the aerodynamic characteristics studied include the following: flow-visualization study, effect of negative angles of attack, lateral-directional characteristics, and comparison of the stall characteristics with another canard configuration.

Chambers, J. R.↗

NASA NTRS1981

Self-induced wing rock of slender delta wings

As part of a research program aimed at exploring basic mechanisms that cause wing rock in combat aircraft, an investigation was conducted to study the aerodynamic factors which cause the low-speed wing rock exhibited by slender delta wings. A flat-plate delta wing with 80 deg leading-edge sweep was subjected to conventional static-force tests and dynamic wind-tunnel experiments which included forced-oscillation, rotary, and free-to-roll tests. In addition, visualization of the flow phenomena involved was obtained by observing tuft patterns and using a helium-bubble technique. This paper summarizes the results of this study. Fundamental information is presented on the aerodynamic mechanisms that cause the wing rock and the problem of mathematically modeling the aerodynamics and motions is discussed.

Nguyen, L. T.↗

NASA NTRS1981

Curved-flow, rolling-flow, and oscillatory pure-yawing wind-tunnel test methods for determination of dynamic stability derivatives

The test capabilities of the Stability Wind Tunnel of the Virginia Polytechnic Institute and State University are described, and calibrations for curved and rolling flow techniques are given. Oscillatory snaking tests to determine pure yawing derivatives are considered. Representative aerodynamic data obtained for a current fighter configuration using the curved and rolling flow techniques are presented. The application of dynamic derivatives obtained in such tests to the analysis of airplane motions in general, and to high angle of attack flight conditions in particular, is discussed.

Chambers, J. R.↗

NASA NTRS1981

Estimation of dynamic stability parameters from drop model flight tests

The overall remotely piloted drop model operation, descriptions, instrumentation, launch and recovery operations, piloting concept, and parameter identification methods are discussed. Static and dynamic stability derivatives were obtained for an angle attack range from -20 deg to 53 deg. It is indicated that the variations of the estimates with angle of attack are consistent for most of the static derivatives, and the effects of configuration modifications to the model were apparent in the static derivative estimates.

Chambers, J. R.↗

NASA NTRS1981

Applications of dynamic stability parameters to problems in aircraft dynamics

The application and analysis of dynamic stability parameters were examined. The effects of wing leading edge modifications on the stalling and spinning characteristics of a single engine general aviation research airplane are evaluated. It is illustrated how dynamic stability parameters measured in wind tunnel tests are used to predict the spin resistance of this class of aircraft, and that autorotation criteria are derived from the relationships which exist between static and dynamic aerodynamic characteristics.

Chambers, J. R.↗

NASA NTRS1981

Curved-flow, rolling-flow, and oscillatory pure-yawing wind-tunnel test methods for determination of dynamic stability derivatives

Dynamic stability derivatives are evaluated on the basis of rolling-flow, curved-flow and snaking tests. Attention is given to the hardware associated with curved-flow, rolling-flow and oscillatory pure-yawing wind-tunnel tests. It is found that the snaking technique, when combined with linear- and forced-oscillation methods, yields an important method for evaluating beta derivatives for current configurations at high angles of attack. Since the rolling flow model is fixed during testing, forced oscillations may be imparted to the model, permitting the measurement of damping and cross-derivatives. These results, when coupled with basic rolling-flow or rotary-balance data, yield a highly accurate mathematical model for studies of incipient spin and spin entry.

Chambers, J. R.↗

NASA NTRS1981

Estimation of dynamic stability parameters from drop model flight tests

A recent NASA application of a remotely-piloted drop model to studies of the high angle-of-attack and spinning characteristics of a fighter configuration has provided an opportunity to evaluate and develop parameter estimation methods for the complex aerodynamic environment associated with high angles of attack. The paper discusses the overall drop model operation including descriptions of the model, instrumentation, launch and recovery operations, piloting concept, and parameter identification methods used. Static and dynamic stability derivatives were obtained for an angle-of-attack range from -20 deg to 53 deg. The results of the study indicated that the variations of the estimates with angle of attack were consistent for most of the static derivatives, and the effects of configuration modifications to the model (such as nose strakes) were apparent in the static derivative estimates. The dynamic derivatives exhibited greater uncertainty levels than the static derivatives, possibly due to nonlinear aerodynamics, model response characteristics, or additional derivatives.

Chambers, J. R.↗

NASA NTRS1981

Applications of dynamic stability parameters to problems in aircraft dynamics

The paper presents highlights of a recent study which illustrates the application and analysis of dynamic stability parameters. More specifically, the investigation consisted of an evaluation of the effects of wing leading-edge modifications on the stalling and spinning characteristics of a single-engine general aviation research airplane. The results of the investigation illustrate how dynamic stability parameters measured in wind-tunnel tests are used to predict the spin resistance of this class of aircraft; and that autorotation criteria can be derived from the relationships which exist between static and dynamic aerodynamic characteristics.

Chambers, J. R.↗

NASA NTRS1980

Overview of stall/spin technology

A general overview of the current state of the art in stall/spin technology for highly-maneuverable military configurations and light general aviation configurations is presented. The key areas of predictive methods, aerodynamics, and flight controls are discussed, using illustrations of results obtained during recent studies. In addition, some of the more-pertinent near-term and future challenges and opportunities in stall/spin technology are discussed. This survey of the existing technology shows that rapid progress has been achieved in each of the key technical areas during the last decade, especially for military airplanes. However, a significant amount of innovative research is urgently required in order to improve the productivity and capabilities of existing predictive techniques, and to provide the technology required for advanced, unconventional configurations.

Chambers, J. R.↗

NASA NTRS1978

Results of piloted simulator studies of fighter aircraft at high angles of attack

The experience gained at the NASA Langley Research Center during the application of simulator techniques to high angle of attack flight conditions for several current fighters is discussed. The discussion includes (1) the simulator hardware, (2) requirements for static and dynamic aerodynamic data inputs, (3) evaluation procedures, (4) correlation with flight, and (5) the effects of dynamic stability parameters. Results obtained with the simulator technique have correlated well with flight test experience, resulting in early identification of potential problems, identification of critical flight conditions, and solutions to various deficiencies in stability and control characteristics. Dynamic stability parameters, results indicate that certain parameters can have a large influence on the flying qualities and tactical effectiveness of fighters at high angles of attack.

Chambers, J. R.↗

NASA NTRS1977

Aerodynamic characteristics of airplanes at high angles of attack

An introduction to, and a broad overiew of, the aerodynamic characteristics of airplanes at high angles of attack are provided. Items include: (1) some important fundamental phenomena which determine the aerodynamic characteristics of airplanes at high angles of attack; (2) static and dynamic aerodynamic characteristics near the stall; (3) aerodynamics of the spin; (4) test techniques used in stall/spin studies; (5) applications of aerodynamic data to problems in flight dynamics in the stall/spin area; and (6) the outlook for future research in the area. Although stalling and spinning are flight dynamic problems of importance to all aircraft, including general aviation aircraft, commercial transports, and military airplanes, emphasis is placed on military configurations and the principle aerodynamic factors which influence the stability and control of such vehicles at high angles of attack.

Chambers, J. R.↗

NASA NTRS1977

Aerodynamic characteristics at high angles of attack

An overview is presented of the aerodynamic inputs required for analysis of flight dynamics in the high-angle-of-attack regime wherein large-disturbance, nonlinear effects predominate. An outline of the presentation is presented. The discussion includes: (1) some important fundamental phenomena which determine to a large extent the aerodynamic characteristics of airplanes at high angles of attack; (2) static and dynamic aerodynamic characteristics near the stall; (3) aerodynamics of the spin; (4) test techniques used in stall/spin studies; (5) applications of aerodynamic data to problems in flight dynamics in the stall/spin area; and (6) the outlook for future research in the area.

Chambers, J. R.↗

NASA NTRS1976

Results of recent NASA studies on spin resistance

Some of the factors which contribute to good stall/spin characteristics of a current fighter configuration indicate that the design of airframe components for inherent spin resistance is very configuration dependent and that few generalizations can be made. Secondary design features, such as fuselage forebody shape, can have significant effects on stability characteristics at high angles of attack. Recent piloted simulator studies and airplane flight tests have indicated that current automatic control systems can be tailored so as to provide a high degree of spin resistance for some configurations without restrictions to maneuverability. Such systems result in greatly increased pilot confidence and increased tactical effectiveness.

Chambers, J. R.↗

NASA NTRS1976

Results of recent NASA studies on automatic spin prevention for fighter aircraft

A broad based research program was developed to eliminate or minimize inadvertent spins for advanced military aircraft. Recent piloted simulator studies and airplane flight tests have demonstrated that the automatic control systems in use on current fighters can be tailored to provide a high degree of spin resistance for some configurations without restrictions to maneuverability. Such systems result in greatly increased tactical effectiveness, safety, and pilot confidence.

Chambers, J. R.↗