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At least 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1931

The aerodynamic wind vane and the inherent stability of airplanes

The design of the wind vane described rests on the following line of reasoning: An airplane, originally in equilibrium about its C.G. is assumed to be deflected from this position through an angle (delta)i, the variation (delta)i being so sudden that the path of the C.G. and the airplane speed do not change while it is taking place. The aerodynamic forces acting on the wings, tail surfaces, fuselage, etc., which, as a whole, exerted a zero moment (M(sub G) = 0) about the center of gravity at the instant of equilibrium, now exert a moment M(sub G) not equal to 0.

Lapresle, A↗
NASA NTRS1930

Recent tests of tailless airplanes

This report details the advantages and construction of tailless airplanes. Both a glider and a powered model were built and the specifications of both airplanes are listed.

Lippisch, Alexander↗
NASA NTRS1994

Windowless Airplane With A View

Proposed windowless passenger airplane gives passengers views of the outside but would be stronger, weigh less, and cost less than does conventional airplane of equivalent capacity. Ordinary see-through windows of today's commercial aircraft replaced by flat-panel color television screens connected to outward-looking video cameras in fuselage.

Carden, Huey D.↗
NASA NTRS1993

Preliminary Flight Results of a Fly-by-throttle Emergency Flight Control System on an F-15 Airplane

A multi-engine aircraft, with some or all of the flight control system inoperative, may use engine thrust for control. NASA Dryden has conducted a study of the capability and techniques for this emergency flight control method for the F-15 airplane. With an augmented control system, engine thrust, along with appropriate feedback parameters, is used to control flightpath and bank angle. Extensive simulation studies were followed by flight tests. The principles of throttles only control, the F-15 airplane, the augmented system, and the flight results including actual landings with throttles-only control are discussed.

Burcham, Frank W., Jr.↗
NASA NTRS1994

3D visualization of unsteady 2D airplane wake vortices

Air flowing around the wing tips of an airplane forms horizontal tornado-like vortices that can be dangerous to following aircraft. The dynamics of such vortices, including ground and atmospheric effects, can be predicted by numerical simulation, allowing the safety and capacity of airports to be improved. In this paper, we introduce three-dimensional techniques for visualizing time-dependent, two-dimensional wake vortex computations, and the hazard strength of such vortices near the ground. We describe a vortex core tracing algorithm and a local tiling method to visualize the vortex evolution. The tiling method converts time-dependent, two-dimensional vortex cores into three-dimensional vortex tubes. Finally, a novel approach calculates the induced rolling moment on the following airplane at each grid point within a region near the vortex tubes and thus allows three-dimensional visualization of the hazard strength of the vortices. We also suggest ways of combining multiple visualization methods to present more information simultaneously.

Ma, Kwan-Liu↗
NASA NTRS1996

A preliminary study of a wake vortex encounter hazard boundary for a B737-100 airplane

A preliminary batch simulation study was conducted to define the wake decay required for a Boeing 737-100 airplane to safely encounter a Boeing 727 wake and land. The baseline six-degree-of-freedom B737 simulation was modified to include a wake model and the strip-theory calculation of the vortex-induced forces and moments. The guidance and control inputs for the airplane were provided by an autoland system. The wake strength and encounter altitude were varied to establish a safe encounter boundary. The wake was positioned such that the desired flight path traversed the core of the port Vortex. Various safe landing criteria were evaluated for defining a safe encounter boundary. A sensitivity study was also conducted to assess the effects of encounter model inaccuracies.

Reimer, Heidi M.↗
NASA NTRS1996

Development and Flight Evaluation of an Emergency Digital Flight Control System Using Only Engine Thrust on an F-15 Airplane

A propulsion-controlled aircraft (PCA) system for emergency flight control of aircraft with no flight controls was developed and flight tested on an F-15 aircraft at the NASA Dryden Flight Research Center. The airplane has been flown in a throttles-only manual mode and with an augmented system called PCA in which pilot thumbwheel commands and aircraft feedback parameters were used to drive the throttles. Results from a 36-flight evaluation showed that the PCA system can be used to safety land an airplane that has suffered a major flight control system failure. The PCA system was used to recover from a severe upset condition, descend, and land. Guest pilots have also evaluated the PCA system. This paper describes the principles of throttles-only flight control; a history of loss-of-control accidents; a description of the F-15 aircraft; the PCA system operation, simulation, and flight testing; and the pilot comments.

Burcham, Frank W., Jr.↗
NASA NTRS1996

Wind Tunnel Tests of an Inflatable Airplane

In this video a wind tunnel investigation of aerodynamic and structural deflection characteristics of an inflatable airplane is shown. The film includes scenarios during wind tunnel tests of an inflatable airplane in the Langley Full Scale Tunnel with the main objective of obtaining load factors prior to wing buckle of 4.5 to 5.0 g. The inflation pressure during the test was indicated to be 7.0 psi.

Source record↗
NASA NTRS1997

Dynamic Ground Effect for a Cranked Arrow Wing Airplane

Flight-determined ground effect characteristics for an F-16XL airplane are presented and correlated with wind tunnel predictions and similar flight results from other aircraft. Maneuvers were conducted at a variety of flightpath angles. Conventional ground effect flight test methods were used, with the exception that space positioning data were obtained using the differential global positioning system (DGPS). Accuracy of the DGPS was similar to that of optical tracking methods, but it was operationally more attractive. The dynamic flight determined lift and drag coefficient increments were measurably lower than steady-state wind-tunnel predictions. This relationship is consistent with the results of other aircraft for which similar data are available. Trends in the flight measured lift increments caused by ground effect as a function of flightpath angle were evident but weakly correlated. An engineering model of dynamic ground effect was developed based on linear aerodynamic theory and super-positioning of flows. This model was applied to the F-16XL data set and to previously published data for an F-15 airplane. In both cases, the model provided an engineering estimate of the ratio between the steady-state and dynamic data sets.

Curry, Robert E.↗
NASA NTRS1959

Measurements Obtained During the First Landing of the North American X-15 Research Airplane

The first landing of the X-15 airplane was made at 8:43 a.m., June 8, 1959, on the hard surface of Rogers Dry Lake. One purpose of the first-glide flight was to evaluate the effectiveness of the landing-gear system. Some results are presented of the landing-approach characteristics, the impact period, and the runout phase of the landing maneuver. The results indicate that the touchdown was accomplished at a vertical velocity of 2.0 feet per second for the main gear and 13.5 feet per second for the nose gear. These vertical velocities were within the values of sinking speeds established by structural design limitations. However, permanent structural deformation occurred in the main-landing-gear system as a result of the landing, and a reevaluation of the gear is being made by the manufacturer. The landing occurred at a true ground speed of 158 knots for main-gear touchdown at an angle of attack of 8.50. The incremental acceleration at the main gear was 2.7g and 7.39 at the nose gear as a result of the landing. The incremental acceleration at the center of gravity of the airplane was 0.6g for the main-gear impact and 2.4g for the nose-gear impact. The incremental acceleration at the main gear as a result of the nose-gear impact was 4.8g. The extreme rearward location of the main-gear skids appears to offer satisfactory directional stability characteristics during the run- out phase of the landing. No evidence of nosewheel shimmy was indicated during the impact and runout phase of the landing despite the absence of a shimmy damper on the nose gear. The maximum amount of skid wear as a result of the landing was on the order of 0.005 inch. No appreciable amount of tire wear was indicated for the dual, corotating nosewheels.

McKay, James M.↗
NASA NTRS1961

Repeatability of the Over-All Errors of an Airplane Altimeter Installation in Landing-Approach Operations

Flight tests have been conducted to determine the repeatability of the over-all altimetry errors in the landing-approach condition of two sensitive altimeters (Air Force type C-12) installed in the cockpit of a transport airplane and of four precision altimeters (Air Force type MA-1) installed in a photo-observer. Data were obtained through a speed range of 62 to 100 knots during 42 landing-approach operations conducted on four different days. The results of the tests show that the repeatability errors of the two sensitive altimeters are +/- 35 feet and +/- 39 feet. These errors are of the same order as the maximum repeatability error measured in previous tests of eleven airplanes of the same type. For each of the four flights of the present tests the mean values of the data obtained with the two sensitive altimeters shifted by relatively large amounts, apparently because of the interaction of the stability and aftereffect- recovery characteristics of the instruments. For concurrent measurements of the over-all errors of the four precision altimeters, it is concluded that for comparable installations, the repeatability errors measured with these altimeters would be smaller than those measured with the sensitive altimeters.

Gracey, William↗
NASA NTRS1959

Low-Speed Measurements of Oscillatory Lateral Stability Derivatives of a 1/7-Scale Model of the North American X-15 Airplane

An investigation to determine the low-speed rolling, yawing, and sideslipping derivatives of a 1/7-scale model which was used to represent the original configuration and a modified configuration of the North American X-15 airplane has been conducted in the Langley free-flight tunnel. The original model was modified to approximately represent the final airplane configuration by reducing the size of the fuselage side fairings and changing the vertical-tail arrangement. The effects of various tail arrangements were determined for both configurations and the effect of small forebody strakes was determined for the modified configuration only.

Paulson, John W.↗
NASA NTRS1960

Atmospheric Turbulence Measurements Obtained from Airplane Operations at Altitudes Between 20,000 and 75,000 Feet for Several Areas in the Northern Hemisphere

Measurements of clear-air turbulence by use of airplane-borne instrumentation have been obtained from NASA VGH recorders during research flights of Lockheed U-2 airplanes to altitudes of 75,000 feet over several areas of the Northern Hemisphere. An analysis of these data has indicated that for the higher altitudes (50,000 to 75,000 feet), turbulence is both less frequent and less severe than for the lower altitudes (20,000 to 50,000 feet). Turbulence appears to be present at the high altitudes (60,000 to 75,000 feet) less than 1 percent of the time. Moderately heavy turbulence appears to exist on occasion at altitudes of about 50,000 feet over Japan. As a consequence, the gust experience appears to be more severe for operations over Japan than for the other areas. Less than 50 percent of the turbulent areas exceeded 10 miles in length.

Coleman, Thomas L.↗
NASA NTRS1961

Aerodynamic Characteristics of a Canard and an Outboard-Tail Airplane Model at High Subsonic Speeds

An investigation has been made in the Langley high-speed 7- by 10-foot tunnel through a range of Mach numbers from 0.60 to 0.95 of the static longitudinal and lateral stability and control characteristics of a canard airplane configuration and an outboard-tail configuration. The canard model had a twisted wing with approximately 67 deg of sweepback and an aspect ratio of 2.91 and was tested with three trapezoidal canard surfaces having ratios of exposed area to wing area of 0.032, 0.076, and 0.121. The canard model had a single body-mounted vertical tail. The outboard-tail model had its horizontal- and vertical-tail surfaces mounted on slender bodies attached to the wing tips and located to the rear and outboard of the 67 deg sweptback wing of aspect ratio 1.00. The data, which are presented with limited analysis, provide information at high subsonic speeds on these two types of high-speed airplanes which have previously been tested at supersonic speeds and reported in NACA RM L58BO7 and NACA RM L58E20.

Fournier, Paul G.↗
NASA NTRS1961

Analog-Computer Investigation of Effects of Friction and Preload on the Dynamic Longitudinal Characteristics of a Pilot-Airplane Combination

With an electric analog computer, an investigation has been made of the effects of control frictions and preloads on the transient longitudinal response of a fighter airplane during abrupt small attitude corrections. The simulation included the airplane dynamics, powered control system, feel system, and a simple linearized pseudopilot. Control frictions at the stick pivot and at the servo valve as well as preloads of the stick and valve were considered individually and in combinations. It is believed that the results which are presented in the form of time histories and vector diagrams present a more detailed illustration of the effects of stray forces and compensating forces in the longitudinal control system than has previously been available. Consistent with the results of previous studies, the present results show that any of these four friction and preload forces caused some deterioration of the response. However, even a small amount of valve friction caused an oscillatory pitching response during which the phasing of the valve friction was such that it caused energy to be fed into the pitching oscillation of the air-plane. Of the other friction and preload forces which were considered, it was found that stick preload was close to 180 deg. out of phase with valve friction and thus could compensate in large measure for valve friction as long as the cycling of the stick encompassed the trim point. Either stick friction or valve preload provided a smaller stabilizing effect primarily through a reduction in the amplitude of the resultant force vector acting on the control system. Some data were obtained on the effects of friction when the damping or inertia of the control system or the pilot lag was varied.

Crane, Harold L.↗
NASA NTRS1959

The Static and Dynamic Rotary Stability Derivatives at Subsonic Speeds of an Airplane Model Having Wing and Tail Surfaces Swept Back 45 degrees

Wind-tunnel measurements were made of the static and dynamic rotary stability derivatives of an airplane model having sweptback wing and tail surfaces. The Mach number range of the tests was from 0.23 to 0.94. The components of the model were tested in various combinations so that the separate contribution to the stability derivatives of the component parts and the interference effects could be determined. Estimates of the dynamic rotary derivatives based on some of the simpler existing procedures which utilize static force data were found to be in reasonable agreement with the experimental results at low angles of attack. The results of the static and dynamic measurements were used to compute the short-period oscillatory characteristics of an airplane geometrically similar to the test model. The results of these calculations are compared with military flying qualities requirements.

Lopez, Armando E.↗
NASA NTRS1961

STOL Characteristics of a Propeller-Driven, Aspect-Ratio-10, Straight-Wing Airplane with Boundary-Layer Control Flaps, as Estimated from Large-Scale Wind-Tunnel Tests

A study is presented of the improvements in take-off and landing distances possible with a conventional propeller-driven transport-type airplane when the available lift is increased by propeller slipstream effects and by very effective trailing-edge flaps and ailerons. This study is based on wind-tunnel tests of a 45-foot span, powered model, with BLC on the trailing-edge flaps and controls. The data were applied to an assumed airplane with four propellers and a wing loading of 50 pounds per square foot. Also included is an examination of the stability and control problems that may result in the landing and take-off speed range of such a vehicle. The results indicated that the landing and take-off distances could be more than halved by the use of highly effective flaps in combination with large amounts of engine power to augment lift (STOL). At the lowest speeds considered (about 50 knots), adequate longitudinal stability was obtained but the lateral and directional stability were unsatisfactory. At these low speeds, the conventional aerodynamic control surfaces may not be able to cope with the forces and moments produced by symmetric, as well as asymmetric, engine operation. This problem was alleviated by BLC applied to the control surfaces.

Weiberg, James A↗