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At least 613 records · Page 34

Airplane Measurements of Atmospheric Turbulence at Altitudes Between 20,000 and 55,000 Feet for Four Geographic Areas

Measurements of clear-air turbulence by use of airplane-borne instruments have been obtained from NACA VGH recorders during research flights of Lockheed U-2 airplanes at altitudes between 20,000 and 55,000 feet over Western United States, England and Western Europe, Turkey, and Japan. An analysis of these data has indicated that at the higher altitudes (40,000 to 55,000 feet) turbulence is both less frequent and less severe than at the lower altitudes (20,000 to 40,000 feet). Turbulence appears to be encountered at the high altitudes for only about 2 percent of the flight distance as compared with 5 percent or more at the lower altitudes. Moderately heavy turbulence exists on occasion at altitudes of about 50,000 feet over Japan and appears to be associated with the strong character of the jet stream in this area and also with a mountain-wave phenomenon.

Coleman, Thomas L.↗

Response of a WB-47E Airplane to Runway Roughness at Eielson AFB, Alaska, September 1964

An investigation has been conducted to measure the response of a WB-47E airplane to the roughness of the runway at Eielson AFB, Alaska. The acceleration level in the pilot's compartment and the pitching oscillation of the airplane were found to be sufficiently high to possibly cause pilot discomfort and have an adverse effect on the precision of take-off.

Morris, Garland J.↗

An Investigation of the Drag Characteristics of a Tailless Delta-Wing Airplane in Flight, Including Comparison with Wind-Tunnel Data

A series of flight tests were conducted to determine the lift and drag characteristics of an F4D-1 airplane over a Mach number range of 0.80 to 1.10 at an altitude of 40,000 feet. Apparently satisfactory agreement was obtained between the flight data and results from wind-tunnel tests of an 0.055-scale model of the airplane. Further tests show the apparent agreement was a consequence of the altitude at which the first tests were made.

Rolls, L. Stewart↗

Jet Interference Effects on a Model of a Single-Engine Four Jet V/STOL Airplane at Mach Numbers from 0.60 to 1.00

An investigation was conducted in the Langley 16-foot transonic tunnel to determine the interference from four exhaust jets on the aerodynamic characteristics of a model of a V/STOL airplane. The single- engine four-jet turbofan power plant of the airplane was simulated by inducing tunnel airflow through two large side inlets and injecting the decomposition products of hydrogen peroxide into the internal flow. The heated gas mixture was exhausted through four nozzles located on the sides of the fuselage under the wing, two near the wing leading edge and two forward of the trailing edge; the nozzles were deflected downward 1.5 deg and outward 5.0 deg to simulate cruise conditions. The wing of the model was a clipped delta with leading-edge sweep of 40 deg, aspect ratio of 3.06, taper ratio of 0.218, thickness-chord ratio of 0.09 at the root and 0.07 at the tip, and 10 deg negative dihedral. Aerodynamic and longitudinal stability coefficients were obtained for the model with the tail removed, and for horizontal-tail incidences of 0 deg and -5 deg. Data were obtained at Mach numbers from 0.60 to 1.00, angles of attack from 0 deg to 12 deg, and with jet total-pressure ratios up to 3.1. Jet operation generally caused a decrease in lift, an increase in pitching-moment coefficient, and a decrease in longitudinal stability at subsonic speeds. The jet interference effects on drag were detrimental at a Mach number of 0.60 and favorable at higher speeds for cruising-flight attitudes.

Schmeer, James W.↗

A Flight Investigation to Determine the Lateral Oscillatory Damping Acceptable for an Airplane in the Landing Approach

An F-86E airplane, in which servo actuation of the ailerons and rudder provides artificial variation of the important lateral and directional aerodynamic stability parameters, has been flown by test pilots of the NASA, U.S. Air Force, and one aircraft manufacturer to determine satisfactory and acceptable levels of lateral oscillatory damping in the landing approach. In addition to normal operational use, particular consideration was given to the emergency condition of failure of stability-augmentation equipment. In this study, the pilots' opinions of the airplane dynamic stability and control characteristics in smooth and simulated rough air have been recorded according to a numerical rating scale. The results are presented in the form of boundaries in terms of cycles to damp to half amplitude, 1/C(sub 1/2), or time to damp to half amplitude, 1/T(1/2) and bank-to-sideslip ratio, and are discussed in relation to existing flying-qualities criteria. Though the present results, which were obtained at 170 knots indicated airspeed and 10,000-feet altitude, indicated that increased damping is required with increased bank-to-sideslip ratio (as found in previous work), consideration of the dampers-failed condition indicated a great reduction in the minimum acceptable damping. At moderate values of bank-to-sideslip ratio, effects of lateral-oscillation period on pilot-opinion variation with damping appeared to be taken into account by use of the parameter 1/T(sub 1/2).

McNeill, Walter E.↗

Effect of the Proximity of the Wing First-Bending Frequency and the Short-Period Frequency on the Airplane Dynamic-Response Factor

The results are presented in the form of preliminary design charts which give a comparison between the dynamic-response factors of the semi-rigid case and the airplane longitudinal short-period case and between the dynamic-response factors of the semi-rigid case and the steady-state value of the airplane longitudinal short-period response. These charts can be used to estimate the first-order effects of the addition of a wing-bending degree of freedom on the short-period dynamic-response factor and on the maximum dynamic-response factor when compared with the steady-state response of the system.

Huss, Carl R.↗

Analysis of Acceleration, Airspeed, and Gust-Velocity Data From a Four-Engine Transport Airplane Operating Over a Northwestern United States Alaska Route

Acceleration, airspeed, and altitude data obtained with an NACA VGH recorder from a four-engine commercial transport airplane operating over a northwestern United States-Alaska route were evaluated to determine the magnitude and frequency of occurrence of gust and maneuver accelerations., operating airspeeds, and gust velocities. The results obtained were then compared with the results previously reported in NACA Technical Note 3475 for two similar airplanes operating over transcontinental routes in the United States. No large variations in the gust experience for the three operations were noted. The results indicate that the gust-load experience of the present operation closely approximated that of the central transcontinental route in the United States with which it is compared and showed differences of about 4 to 1 when compared with that of the southern transcontinental route in the United States. In general, accelerations due to gusts occurred much more frequently than those due to operational maneuvers. At a measured normal-acceleration increment of 0.5g, accelerations due to gusts occurred roughly 35 times more frequently than those due to operational maneuvers.

Engel, Jerome N.↗

Flight Data Reduction of Wake Velocity Measurements Using an Instrumented OV-10 Airplane

A series of flight tests to measure the wake of a Lockheed C- 130 airplane and the accompanying atmospheric state have been conducted. A specially instrumented North American Rockwell OV-10 airplane was used to measure the wake and atmospheric conditions. An integrated database has been compiled for wake characterization and validation of wake vortex computational models. This paper describes the wake- measurement flight-data reduction process.

Vicroy, Dan D.↗

Flight Investigation to Determine the Aerodynamic Characteristics of Rocket-Powered Models Representative of a Fighter-Type Airplane Configuration Incorporating an Inverse-Taper Wing and a Vee Tail

Two rocket-powered models representative of a fighter-type airplane were investigated in flight at Mach numbers up to 1.01 and 1.07 by the Langley Pilotless Aircraft Research Division at its testing station at Wallops Island, Va. These models incorporated an inverse-taper wing and a vee tail and were flown with controls undeflected and wing and stabilizer set at 0 deg incidence. Values of lateral acceleration, normal acceleration velocity, and drag were obtained by use of telemeters and a Doppler velocimeter radar unit. The results of this investigation indicated no unusual variation in the lateral acceleration characteristics. After the cessation of powered flight, the lateral oscillation quickly damped to zero. The data indicated that the airplane, at low lift coefficients, should not experience any abrupt trim changes until it attains a Mach number of 0.97. The change in normal-force coefficient associated with this trim change will amount to about 0.03 with the center of gravity located at 4.48% of the mean aerodynamic chord. At higher lift coefficients, on the basis of other data, the Mach number at which this trim change occurs would be expected to be decreased. The neutral point of the model at Mach numbers near 1.05 was estimated to fall at 45% of the mean aerodynamic chord, assuming a lift-curve slope of 0.05. A value of the static-directional-stability parameter dCn/d(psi) of approximately -0.002 was estimated for a Mach number of 0.93. The values of drag coefficient obtained from both model flights were in a good comparative agreement. The highest drag coefficient occurred at a Mach number of 1.01 and was equal to 0.044.

Alexander, Sidney R.↗

Flight Measurements of the Flying Qualities of a Lockheed P-80A Airplane (Army No. 44-85099): Lateral- and Directional-Stability and Control Characteristics

This report contains the flight-test results of the lateral and directional-stability and control phase (including tests with wing-tip tanks) of a general flying-qualities investigation of the Lockheed P-80A airplane (Army No. 44-85099). These tests were conducted at indicated airspeeds up to 494 miles per hour (0.691 Mach number) at low altitude and up to 378 miles per hour (0.816 Mach number) at high altitude. These tests showed that the flying qualities of the airplane were for the most part in accordance with the requirements of the Army Air Forces Stability and Control Specifications. The only major deficiency noted was the negative lateral stability with the wing-tip tanks installed.

Anderson, Seth B.↗

Flight Measurements of the Flying Qualities of a Lockheed P-80A Airplane (Army No. 44-85099): Longitudinal-Stability and -Control Characteristics

This report contains the flight-test results of the longitudinal-stability and -control phase of a general flying qualities investigation of the Lockheed P-80A airplane (Army No. 44-85099). The tests were conducted at indicated airspeeds up to 530 miles per hour (0.76 Mach number) at low altitude and up to 350 miles per hour (0.82) Mach number) at high altitude. These tests showed that the flying qualities of the airplane were in accordance with the requirements of the Army Air Forces Stability and Control Specification except for excessive elevator control forces in maneuvering flight and the inadequacy of the longitudinal trimming control at low airspeeds.

Anderson, Seth B.↗

Engine Installation Effects of Four Civil Transport Airplanes: Wallops Flight Facility Study

The National Aeronautics and Space Administration (NASA), Langley Research Center (LaRC), the Environmental Measurement and Modeling Division of the United States Department of Transportation s John A. Volpe National Transportation Systems Center (Volpe), and several other organizations (see Appendix A for a complete list of participating organizations and individuals) conducted a noise measurement study at NASA s Wallops Flight Facility (Wallops) near Chincoteague, Virginia during September 2000. This test was intended to determine engine installation effects on four civil transport airplanes: a Boeing 767-400, a McDonnell-Douglas DC9, a Dassault Falcon 2000, and a Beechcraft King Air. Wallops was chosen for this study because of the relatively low ambient noise of the site and the degree of control over airplane operating procedures enabled by operating over a runway closed to other uses during the test period. Measurements were conducted using a twenty microphone U-shaped array oriented perpendicular to the flight path; microphones were mounted such that ground effects were minimized and low elevation angles were observed.

Fleming, Gregg G.↗

Ground Measurements of the Shock-Wave Noise from Supersonic Bomber Airplanes in the Altitude Range from 30,000 to 50,000 Feet

Shock-wave ground-pressure measurements have been made for supersonic bomber airplanes in the Mach number range from 1.24 to 1.52, for altitudes from about 30,000 to 50,000 feet, and for a gross-weight range from about 83,000 to 120,000 pounds. The measured overpressures were generally higher than would be predicted by the theory which accounts only for volume effects. There is thus a suggestion that lift effects on sonic-boom intensity may be significant for this type of airplane for the altitude range of the present tests.

Maglieri, Domenic J.↗

Experimental and Calculated Flow Fields Produced by Airplanes Flying at Supersonic Speeds

Results are presented of a flight investigation conducted to survey the flow field generated by airplanes flying a t supersonic speeds. The pressure signatures of an F-100, an F-104, and a B-58 airplane, representing widely varying configurations, a t distances from 120 t o 425 f e e from the generating aircraft and at Mach numbers from 1.2 t o 1.8 are shown. Calculations were made by using Whitham's method and were compared with the experimental results.

Smith, Harriet J.↗

Recent Dynamic Measurements and Considerations for Aerodynamic Modeling of Fighter Airplane Configurations

As airplane designs have trended toward the expansion of flight envelopes into the high angle of attack and high angular rate regimes, concerns regarding modeling the complex unsteady aerodynamics for simulation have arisen. Most current modeling methods still rely on traditional body axis damping coefficients that are measured using techniques which were intended for relatively benign flight conditions. This paper presents recent wind tunnel results obtained during large-amplitude pitch, roll and yaw testing of several fighter airplane configurations. A review of the similitude requirements for applying sub-scale test results to full-scale conditions is presented. Data is then shown to be a strong function of Strouhal number - both the traditional damping terms, but also the associated static stability terms. Additionally, large effects of sideslip are seen in the damping parameter that should be included in simulation math models. Finally, an example of the inclusion of frequency effects on the data in a simulation is shown.

Brandon, Jay M.↗

A Numerical Simulation Study to Develop an Acceptable Wake Encounter Boundary for a B737-100 Airplane

The National Aeronautics and Space Administration (NASA) is conducting research with the goal of enabling safe improvements in the capacity of the nation's air transportation system. The wake-vortex upset hazard is an important factor in establishing the minimum safe spacing between aircraft during landing and take-off operations, thus impacting airport capacity. A batch simulation study was conducted to assess the sensitivity of various safe landing criteria in the development of an acceptable wake encounter boundary. A baseline six-degree-of-freedom simulation of a B737-100 airplane was modified to include a wake model and the vortex-induced forces and moments. The guidance and control input for the airplane was provided by an auto-land system. The wake strength and encounter geometry were varied. A sensitivity study was also conducted to assess the effects of encounter modeling methods and accuracy.

Vicroy, Dan D.↗

Rapid Airplane Parametric Input Design(RAPID)

An efficient methodology is presented for defining a class of airplane configurations. Inclusive in this definition are surface grids, volume grids, and grid sensitivity. A small set of design parameters and grid control parameters govern the process. The general airplane configuration has wing, fuselage, vertical tail, horizontal tail, and canard components. The wing, tail, and canard components are manifested by solving a fourth-order partial differential equation subject to Dirichlet and Neumann boundary conditions. The design variables are incorporated into the boundary conditions, and the solution is expressed as a Fourier series. The fuselage has circular cross section, and the radius is an algebraic function of four design parameters and an independent computational variable. Volume grids are obtained through an application of the Control Point Form method. Grid sensitivity is obtained by applying the automatic differentiation precompiler ADIFOR to software for the grid generation. The computed surface grids, volume grids, and sensitivity derivatives are suitable for a wide range of Computational Fluid Dynamics simulation and configuration optimizations.

Smith, Robert E.↗

Development of Outboard Nacelle for the XB-36 Airplane

An investigation of two 1/14 scale model configurations of an outboard nacelle for the XB-36 airplane was made in the Langley two-dimensional low-turbulence tunnels over a range of airplane lift coefficients (C (sub L) = 0.409 to C(sub L) = 0.943) for three representative flow conditions. The purpose of the investigation was to develop a low-drag wing-nacelle pusher combination which incorporated an internal air-flow system. The present investigation has led to the development of a nacelle which had external drag coefficients of similar order of magnitude to those obtained previously from tests of an inboard nacelle configuration at the corresponding operating lift coefficients and from approximately one-third to one-half of those of conventional tractor designs having the same ratio of wing thickness to nacelle diameter.

Nuber, Robert J.↗