Aircraft response to the wing trailing vortices generated by large jet transports
Flight tests for evaluating effect of wing-tip vortex wake generated by large jet transports on smaller aircraft
Andrews, W. H.↗
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Longitudinal Aerodynamic Characteristics to Large Angles of Attack of a Cruciform Missile Configuration at a Mach Number of 2
The lift, pitching-moment, and drag characteristics of a missile configuration having a body of fineness ratio 9.33 and a cruciform triangular wing and tail of aspect ratio 4 were measured at a Mach number of 1.99 and a Reynolds number of 6.0 million, based on the body length. The tests were performed through an angle-of-attack range of -5 deg to 28 deg to investigate the effects on the aerodynamic characteristics of roll angle, wing-tail interdigitation, wing deflection, and interference among the components (body, wing, and tail). Theoretical lift and moment characteristics of the configuration and its components were calculated by the use of existing theoretical methods which have been modified for application to high angles of attack, and these characteristics are compared with experiment. The lift and drag characteristics of all combinations of the body, wing, and tail were independent of roll angle throughout the angle-of-attack range. The pitching-moment characteristics of the body-wing and body-wing-tail combinations, however, were influenced significantly by the roll angle at large angles of attack (greater than 10 deg). A roll from 0 deg (one pair of wing panels horizontal) to 45 deg caused a forward shift in the center of pressure which was of the same magnitude for both of these combinations, indicating that this shift originated from body-wing interference effects. A favorable lift-interference effect (lift of the combination greater than the sum of the lifts of the components) and a rearward shift in the center of pressure from a position corresponding to that for the components occurred at small angles of attack when the body was combined with either the exposed wing or tail surfaces. These lift and center-of-pressure interference effects were gradually reduced to zero as the angle of attack was increased to large values. The effect of wing-tail interference, which influenced primarily the pitching-moment characteristics, is dependent on the distance between the wing trailing vortex wake and the tail surfaces and thus was a function of angle of attack, angle of roll, and wing-tail interdigitation. Although the configuration at zero roll with the wing and tail in line exhibited the least center-of-pressure travel, the configuration with the wing and tail interdigitated had the least change in wing-tail interference over the angle-of-attack range. The lift effectiveness of the variable-incidence wing was reduced by more than 70 percent as a result of an increase in the combined angle of attack and wing incidence from 0 deg to 40 deg. The wing-tail interference (effective downwash at the tail) due to wing deflection was nearly zero as a result of a region of negative vorticity shed from the inboard portion of the wing. The lift characteristics of the configuration and its components were satisfactorily predicted by the calculated results, but the pitching moments at large angles of attack were not because of the influence of factors for which no adequate theory is available, such as the variation of the crossflow drag coefficient along the body and the effect of the wing downwash field on the afterbody loading.
Spahr, J. R.↗
Experiments on a turbulent jet in a cross flow.
Results are reported of experiments on turbulent circular jets issuing into a cross flow, both for unheated and heated jets. Longitudinal and transverse distributions of velocity, temperature, and turbulence intensity are presented. The velocity distributions depend mainly on the ratio of jet to cross flow momentum flux. The temperature distributions depend also on the density ratio. The jet structure is dominated by a vortex wake which forms behind the jet, which is evident both from the detail measurements and from smoke photographs of the flow. The experiments also indicate that the components of cross flow normal and parallel to the jet trajectory independently control the entrainment rate.
Kamotani, Y.↗
Fundamental Consideration of Noise radiation by rotary wings
An historical review of progress in understanding of rotor noise is presented. Initial work was principally on propellers, but has many obvious applications to noise from rotary wings. Current understanding of rotor noise radiation is then reviewed in some detail. The principal noise sources appear to be: (1) discrete frequency due to distorted inflow; (2) low frequency broadband due to turbulent inflow, and (3) high frequency broadband due to tip effects. On a helicopter rotor each of these sources seems to be intimately connected with the shed vortex wakes. Tip modifications offer one method for controlling the effects. The implications for the designer are discussed. Rotor subjective noise levels appear to obey a velocity to the eighth power law, independent of thrust. Experiments to rectify some of the present deficiencies in knowledge are suggested.
Lowson, M. V.↗
Separated flow over bodies of revolution using an unsteady discrete-vorticity cross wake. Part 2: Computer program description
A method is developed to determine the flow field of a body of revolution in separated flow. The computer was used to integrate various solutions and solution properties of the sub-flow fields which made up the entire flow field without resorting to a finite difference solution to the complete Navier-Stokes equations. The technique entails the use of the unsteady cross flow analogy and a new solution to the two-dimensional unsteady separated flow problem based upon an unsteady, discrete-vorticity wake. Data for the forces and moments on aerodynamic bodies at low speeds and high angle of attack (outside the range of linear inviscid theories) such that the flow is substantially separated are produced which compare well with experimental data. In addition, three dimensional steady separated regions and wake vortex patterns are determined. The computer program developed to perform the numerical calculations is described.
Marshall, F. J.↗
Separated flow over bodies of revolution using an unsteady discrete-vorticity cross wake. Part 1: Theory and application
A method is developed to determine the flow field of a body of revolution in separated flow. The technique employed is the use of the computer to integrate various solutions and solution properties of the sub-flow fields which made up the entire flow field without resorting to a finite difference solution to the complete Navier-Stokes equations. The technique entails the use of the unsteady cross flow analogy and a new solution to the required two-dimensional unsteady separated flow problem based upon an unsteady, discrete-vorticity wake. Data for the forces and moments on aerodynamic bodies at low speeds and high angle of attack (outside the range of linear inviscid theories) such that the flow is substantially separated are produced which compare well with experimental data. In addition, three dimensional steady separation regions and wake vortex patterns are determined.
Marshall, F. J.↗
A flight research program to develop airborne systems for improved terminal area operations
The research program considered is concerned with the solution of operational problems for the approximate time period from 1980 to 2000. The problems are related to safety, weather effects, congestion, energy conservation, noise, atmospheric pollution, and the loss in productivity caused by delays, diversions, and schedule stretchouts. The terminal configured vehicle (TCV) program is to develop advanced flight-control capability. The various aspects of the TCV program are discussed, giving attention to avionics equipment, the piloted simulator, terminal-area environment simulation, the Wallops research facility, flight procedures, displays and human factors, flight activities, and questions of vortex-wake reduction and tracking.
Reeder, J. P.↗
Recent wake turbulence flight test programs
In early flight tests the size and intensity of the wake vortexes generated by aircraft ranging in size from the Learjet to the C-5A and the B-747 were studied to determine the effects of aircraft configuration, weight, and speed. Early problems were related to vortex marking, the measurement of separation distance, and test techniques. Recent tests conducted with B-747 showed that vortexes were alleviated by reducing the deflection of the outboard flaps. It was found that a more rapid dissipation of the vortex system can be obtained through alterations in the span lift distribution.
Tymczyszyn, J. J.↗
Separated flow over a body of revolution
A method is developed to determine the flowfield of a body of revolution in separated flow. The technique employed is the use of the computer to integrate various solutions and solution properties of the sub-flowfields which make up the entire flowfield without resorting to a finite difference solution to the complete Navier-Stokes equations. The technique entails the use of the unsteady cross flow analogy and a new solution to the required two-dimensional unsteady separated flow problem based upon an unsteady discrete-vorticity wake. Data for the forces and moments on bodies of revolution at high angle of attack (outside the range of linear inviscid theories) such that the flow is substantially separated are produced which compare well with experimental data at low speeds. In addition, three-dimensional steady separation regions and wake vortex patterns are determined.
Marshall, F. J.↗
A subvortex technique for the close approach to a discretized vortex sheet
The close-approach problem associated with vortex-lattice methods was examined numerically with the objective of calculating velocities at arbitrary points, not just at midpoints, between the vortices. The objective was achieved using a subvortex technique in which a vortex splits into an increasing number of subvortices as it is approached. The technique, incorporated in a two-dimensional potential flow method using "submerged" vortices and sources, was evaluated for a cambered Joukowski airfoil. The method could be extended to three dimensions, and should improve non-linear methods, which calculate interference effects between multiple wings and vortex wakes, and which include procedures for force-free wakes.
Maskew, B.↗
Passenger ride comfort technology for transport aircraft situations
Research in ride comfort and of the resultant technology is overviewed. Several useful relations derived from the technology are: input environments to the vehicle; aircraft operations; and aircraft configurations. Input environments which influence the ride motion environment consist of naturally occuring phenomena such as gusts or turbulence and man generated phenomena such as trailing vortex wakes or runway roughness. Aircraft operations influence ride environments in the form of motions caused by maneuvers, of pressure changes caused by rapid descents, or of too high temperature. Aircraft configurations influence the ride environment by size and shape of external surfaces which generate aerodynamic perturbing forces; by onboard equipment, such as power plant noise and vibrations; and by passive equipment which directly interfaces the passengers such as marginal size seats with limited elbowroom and legroom.
Conner, W.↗
Forecast of the general aviation air traffic control environment for the 1980's
The critical information required for the design of a reliable, low cost, advanced avionics system which would enhance the safety and utility of general aviation is stipulated. Sufficient data is accumulated upon which industry can base the design of a reasonably priced system having the capability required by general aviation in and beyond the 1980's. The key features of the Air Traffic Control (ATC) system are: a discrete address beacon system, a separation assurance system, area navigation, a microwave landing system, upgraded ATC automation, airport surface traffic control, a wake vortex avoidance system, flight service stations, and aeronautical satellites. The critical parameters that are necessary for component design are identified. The four primary functions of ATC (control, surveillance, navigation, and communication) and their impact on the onboard avionics system design are assessed.
Hoffman, W. C.↗
Investigating complex aerodynamic flows with a laser velocimeter
The paper discusses the application of the laser velocimeter in the study of two highly complex aerodynamic flows. In the first experiment, the laser velocimeter has been used with frequency tracking electronics to survey the multiple vortex wake structure behind a model of a large jet transport. The second application is to the study of the induced instantaneous inflow velocities near the blades of a model helicopter rotor; counter type processing was used in these measurements. In each experiment, the data output channels of these processors were handled in an on-line fashion, including both velocity computations and the plotting of fully reduced data.
Orloff, K. L.↗
Investigating complex aerodynamic flows with a laser velocimeter
The application of the laser velocimeter in the study of two highly complex aerodynamic flows is discussed. In the first experiment, the laser velocimeter was used with frequency tracking electronics to survey the multiple vortex wake structure behind a model of a large jet transport. The second application is to the study of the induced instantaneous inflow velocities near the blades of a model helicopter rotor; counter-type processing was used in these measurements. In each experiment, the data output channels of these processors were handled in an on-line fashion, including both velocity computations and the plotting of fully reduced data.
Orloff, K. L.↗
Determining the Lift and Drag Distributions on a Three-Dimensional Airfoil from Flow-Field Velocity Surveys
The application of the incompressible momentum integral equation to a three-dimensional airfoil was reviewed to interpret the resulting equations in a way that suggests a reasonable experimental technique for determining the spanwise distributions of lift and drag. Consideration was given to constraints that must be placed on the character of the vortex wake structure shed by the wing, to provide the familiar relationship between lift and bound vorticity. It is shown that the induced drag distribution is not directly measurable, but can be obtained, via the lift distribution, approximately for a deflected wake and exactly for a planar wake. Moreover, it is shown that it is only necessary to survey a short distance above and below the wing trailing edge. Examples are presented for several typical loading distributions and the results of a numerical simulation of the suggested experiment are discussed.
Orloff, K. L.↗
Modular high accuracy tracker for dual channel laser Doppler velocimeter
In the study described, a scanning dual-channel cross-beam laser Doppler velocimeter (developed for measuring simultaneously the two orthogonal components of flow velocity and turbulence intensity) was used to measure the instantaneous velocity characteristics of a model helicopter rotor and in a vortex wake survey experiment on a Boeing 747 aircraft model. Particular attention is given to a special purpose dual-loop frequency tracker developed to track and demodulate 10 microsecond wide pulse burst Doppler signals with a study cycle of 25% (or narrower signals at a higher duty cycle) generated by the laser Doppler velocimeter.
Fridman, J. D.↗
NASA's aviation safety research and technology program
Aviation safety is challenged by the practical necessity of compromising inherent factors of design, environment, and operation. If accidents are to be avoided these factors must be controlled to a degree not often required by other transport modes. The operational problems which challenge safety seem to occur most often in the interfaces within and between the design, the environment, and operations where mismatches occur due to ignorance or lack of sufficient understanding of these interactions. Under this report the following topics are summarized: (1) The nature of operating problems, (2) NASA aviation safety research, (3) clear air turbulence characterization and prediction, (4) CAT detection, (5) Measurement of Atmospheric Turbulence (MAT) Program, (6) Lightning, (7) Thunderstorm gust fronts, (8) Aircraft ground operating problems, (9) Aircraft fire technology, (10) Crashworthiness research, (11) Aircraft wake vortex hazard research, and (12) Aviation safety reporting system.
Fichtl, G. H.↗
The promise of advanced technology for future air transports
Progress in all weather 4-D navigation and wake vortex attenuation research is discussed and the concept of time based metering of aircraft is recommended for increased emphasis. The far term advances in aircraft efficiency were shown to be skin friction reduction and advanced configuration types. The promise of very large aircraft, possibly all wing aircraft is discussed, as is an advanced concept for an aerial relay transportation system. Very significant technological developments were identified that can improve supersonic transport performance and reduce noise. The hypersonic transport was proposed as the ultimate step in air transportation in the atmosphere. Progress in the key technology areas of propulsion and structures was reviewed. Finally, the impact of alternate fuels on future air transports was considered and shown not to be a growth constraint.
Bower, R. E.↗