Search NASA⌕ Search

SEARCH · Search NASA

Results for “Yaw”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
NASA NTRS1941

Comparison of Vee-Type and Conventional Tail Surfaces in Combination with Fuselage and Wing in the Variable-Density Tunnel

The pitching and the yawing moments of a vee-type and a conventional type of tail surface were measured. The tests were made in the presence of a fuselage and a wing-fuselage combination in such a way as to determine the moments contributed by the tail surfaces. The results showed that the vee-type tail tested, with a dihedral angle of 35.3 deg, was about 71 percent as effective in pitch as the conventional tail and had a yawing-moment to pitching-moment ratio of 0.3. The conventional tail, the panels of which were all congruent to those of the vee-type tail, had a yawing-moment to pitching-moment ratio of 0.48. These ratios are in fair agreement with values calculated by methods shown in this and previous reports. The values of the measured moments were reduced from 15 to 25 percent of the calculated value by fuselage interference.

Greenberg, Harry↗
NASA NTRS1937

Ground-Handling Forces on a 1/40-scale Model of the U. S. Airship "Akron."

This report presents the results of full-scale wind tunnel tests conducted to determine the ground-handling forces on a 1/40-scale model of the U. S. Airship "Akron." Ground-handling conditions were simulated by establishing a velocity gradient above a special ground board in the tunnel comparable with that encountered over a landing field. The tests were conducted at Reynolds numbers ranging from 5,000,000 to 19,000,000 at each of six angles of yaw between 0 degree and 180 degrees and at four heights of the model above the ground board. The ground-handling forces vary greatly with the angle of yaw and reach large values at appreciable angles of yaw. Small changes in height, pitch, or roll did not critically affect the forces on the model. In the range of Reynolds numbers tested, no significant variation of the forces with the scale was disclosed.

Silverstein, Abe↗
NASA NTRS1948

Stability derivatives of triangular wings at supersonic speeds

The analysis of the stability derivatives of low-aspect-ratio triangular wings at subsonic and supersonic speeds, given in NACA TN no. 1423, is extended to apply to triangular wings having large vertex angles and traveling at supersonic speeds. The lift, rolling moment due to sideslip, and damping in roll and pitch for this more general case have been treated elsewhere on the basis of the theory of small disturbances. The surface potentials for angle of attack and rolling taken therefrom are used to obtain the several side-force and yawing-moment derivatives that depend on leading-edge suction, and a tentative value for the rolling moment due to yawing. The lift and moment due to downward acceleration are obtained on the basis of an unpublished unsteady-flow solution. All the known stability derivatives of the triangular wing at supersonic speeds, regardless of source, are summarized for convenience and presented with respect to both body axes and stability axes. The results are limited to Mach numbers for which the triangular wing is contained within the Mach cone for its vertex. The spanwise variation of Mach number in the case of yawing is neglected, although the effect must be of importance.

Ribner, Herbert S↗
NASA NTRS1954

Experimental investigation of the forces and moments due to sideslip of a series of triangular vertical and horizontal tail combinations at Mach numbers

An experimental investigation was made at Mach numbers of 1.62, 1.93, and 2.41 of a series of tail combinations consisting of triangular vertical tail attached symmetrically to a triangular horizontal tail to determine the lateral force, yawing moment, and rolling moment due to sideslip. The apex angles of both the vertical- and horizontal-tail surfaces were varied systematically in order to obtain results for an appreciable range of operating conditions. The results of the investigation indicated that, for tails having subsonic leading edges and supersonic trailing edges, the lateral-force derivative and the yawing-moment derivative were predicted satisfactorily by the method presented in NACA TN 3071 except when the leading edges approach a sonic condition. The theoretical rolling-moment derivative was in fair agreement with the experimental derivative. For the limited tests in which both the leading and trailing edges were supersonic, the prediction of the lateral-force derivative and the yawing-moment derivative obtained from NACA TN 2412 was in good agreement with the experimental derivatives, whereas the prediction of the rolling-moment derivative was fair.

Coletti, Donald E↗
NASA NTRS1993

Aerodynamic control of NASP-type vehicles through Vortex manipulation. Volume 1: Static water tunnel tests

Water tunnel tests were conducted on a NASP-type configuration to evaluate different pneumatic Forebody Vortex Control (FVC) methods. Flow visualization and yawing moment measurements were performed at angles of attack from 0 deg to 30 deg. The pneumatic techniques tested included jet and slot blowing. In general, blowing can be used efficiently to manipulate the forebody vortices at angles of attack greater than 20 deg. These vortices are naturally symmetric up to alpha = 25 deg and asymmetric between 25 deg and 30 deg angle of attack. Results indicate that tangential aft jet blowing is the most promising method for this configuration. Aft jet blowing produces a yawing moment towards the blowing side and the trends with blowing rate are well behaved. The size of the nozzle is not the dominant factor in the blowing process; the change in the blowing 'momentum,' i.e., the product of the mass flow rate and the velocity of the jet, appears to be the important parameter in the water tunnel (incompressible and unchoked flow at the nozzle exit). Forward jet blowing is very unpredictable and sensitive to mass flow rate changes. Slot blowing (with the exception of very low blowing rates) acts as a flow 'separator'; it promotes early separation on the blow side, producing a yawing moment toward the non-blowing side for the C(sub mu) range investigated.

Suarez, Carlos J.↗
NASA NTRS1994

Controls design with crossfeeds for hovering rotorcraft using quantitative feedback theory

This work is extending the research accomplished on project NCC2-751. A newly implemented helicopter model has been used to simulate 25 flight configurations near hover for the UH-60 RASCAL aircraft. A new engine model has been installed in the FORECAST simulation (alias UMGENHEL) for the better prediction of the yaw and heave responses. By applying the decoupling metric from project NCC 751 it was determined that the aileron to pitch and the elevator to yaw responses do not indicate the need for crossfeeds since both of them have a decoupling metric value over 20 dB (less than 10 percent coupling). In the case of the aileron to heave and the elevator to heave responses, the large size and the overlapping of the templates indicate that a low-order dynamic crossfeed cannot be found. The low-order dynamic crossfeed selection is proceeding, however, for the remaining eight crossfeeds. Note that most of them have successfully decoupled the system by 20 dB or more, except for the rudder to heave crossfeed (18.2 dB). It is probable that the engine model needs more accuracy to further improve the heave to yaw crossfeed decoupling metric value. To see how the new low-order dynamic crossfeeds perform, a simulation was accomplished using MATLAB SIMULINK.

Biezad, Daniel J.↗
NASA NTRS1994

Wind tunnel measurements on a full-scale F/A-18 with a tangentially blowing slot

A full-scale F/A-18 was tested in the 80 by 120-Foot Wind Tunnel at NASA Ames Research Center to measure the effectiveness of a tangentially blowing slot in generating significant yawing moments while minimizing coupling in the pitch and roll axes. Various slot configurations were tested to determine the optimum configuration. The test was conducted for angles of attack from 25 to 50 deg, angles of sideslip from -15 to +15 deg, and freestream velocities from 67 ft/sec to 168 ft/sec. By altering the forebody vortex flow, yaw control was maintained for angles of attack up to 50 deg. Of particular interest was the result that blowing very close to the radome apex was not as effective as blowing slightly farther aft on the radome, that a 16-inch slot was more efficient, and that yawing moments were generated without inducing significant rolling or pitching moments.

Lanser, Wendy R.↗
NASA NTRS1994

Controlling forebody asymmetries in flight: Experience with boundary layer transition strips

The NASA Dryden Flight Research Center has an ongoing program to investigate aircraft flight characteristics at high angles of attack. As part of this investigation, longitudinal boundary layer transition strips were installed on the F-18 HARV forebody, a preproduction F/A-18 radome with a nose-slice tendency, and the X-31 aircraft forebody and noseboom to reduce asymmetric yawing moments at high angles of attack. The transition strips were effective on the F-18 HARV at angles of attack above 60 deg. On the preproduction F/A-18 radome at an angle of attack near 50 deg the strips were not effective. When the transition strips were installed on the X-31 noseboom, a favorable effect was observed on the yawing moment dynamics but the magnitude of the yawing moment was not decreased.

David F Fisher↗
NASA NTRS1994

Comparison of full-scale, small-scale, and CFD results for F/A-18 forebody slot blowing

It has been shown experimentally that forebody flow control devices provide a significant increase in yaw control for fighter aircraft at high angle-of-attack. This study presents comparisons of the various experimental and computational results for tangential slot blowing on the F/A-18 configuration. Experimental results are from the full-scale and 6 percent-scale model test and computational solutions are from both isolated forebody and and full aircraft configurations. The emphasis is on identifying trends in the variation of yawing moment with blowing-slot exit conditions. None of the traditional parameters (mass flow ratio, blowing momentum coefficient, velocity ratio) succeeded in collapsing all of the results into a common curve. Several factors may effect the agreement between the 6 percent- and full-scale results including Reynolds number effects, sensitivity of boundary layer transition from laminar to turbulent flow, and poor geometric fidelity, particularly of the blowing slot. The disagreement between the full-scale and computed yawing moments may be due to a mismatch in the slot exit conditions for the same mass flow ratio or aircraft configuration modeling. The general behavior of slot blowing on the 6 percent-scale and computational models is correct, but neither matches the full-scale results.

Lanser, Wendy R.↗
NASA NTRS1995

Extension to the dynamic modeling of the large angle magnetic suspension test fixture

The Large Angle Magnetic Suspension Test Fixture (LAMSTF) is a laboratory scale proof-of-concept system. The configuration is unique in that the electromagnets are mounted in a circular planar array. A mathematical model of the system had previously been developed, but was shown to have inaccuracies. These inaccuracies showed up in the step responses. Eddy currents were found to be the major cause of the modeling errors. In the original system, eddy currents existed in the aluminum baseplate, iron cores, and the sensor support frame. An attempt to include the eddy current dynamics in the system model is presented. The dynamics of a dummy sensor ring were added to the system. Adding the eddy current dynamics to the simulation improves the way it compares to the actual experiment. Also presented is a new method of determining the yaw angle of the suspended element. From the coil currents the yaw angle can be determined and the controller can be updated to suspend at the new current. This method has been used to demonstrate a 360 degree yaw angle rotation.

Foster, Lucas E.↗
NASA NTRS1995

Tire footprint studies

This presentation covers the results of tire footprint studies conducted in the Landing Gear Development Facility of the USAF Wright Laboratory at the Wright Patterson Air force Base, OH. Tire footprint studies are essential in understanding tire wear mechanisms and computing tire tread wear rates. The power input into the tread is the driving force for tread wear. Variables needed for power input calculations include the footprint pressure and slip velocity distributions. Studies were performed on the effects of power input distributions due to vertical load, camber, yaw, inflation pressure, and tire construction. For the present study, two tire constructions, one radial and the other bias, were selected. These tires were for the F-16 Block 30 fighter aircraft, both of which were previously worn. The present study was limited to steady straight roll with a 14,000 lb vertical load, a 310 psi inflation pressure, and zero yaw and camber. All tests were conducted on the Tire Force Machine (TFM) with a specialized sensor plate with embedded pressure sensors (X, Y, and Z) and slip sensors (X and Y). All tests were conducted for a table speed of 1 in/s. Tests on the TFM show that the power intensity distributions and total power for both tire constructions are quite similar for straight roll. Later on, tests were also conducted on a modified dynamometer which was overlaid with a grit wear surface. The tire speed was maintained at 40 miles per hour and yaw was set to four degrees. Dynamometer tests showed that radial tires have more tread wear than the bias tire; however, in the field, radial tires have longer life.

Chawla, Mangal↗
NASA NTRS1996

Controls design with crossfeeds for hovering rotorcraft using quantitative feedback theory

A multi-input, multi-output controls design with dynamic crossfeed pre-compensation is presented for rotorcraft in near-hovering flight using Quantitative Feedback Theory (QFT). The resulting closed-loop control system bandwidth allows the rotorcraft to be considered for use as an inflight simulator. The use of dynamic, robust crossfeeds prior to the QFT design reduces the magnitude of required feedback gain and results in performance that meets most handling qualities specifications relative to the decoupling of off-axis responses. Handling qualities are Level 1 for both low-gain tasks and high-gain tasks in the roll, pitch, and yaw axes except for the 10 deg/sec moderate-amplitude yaw command where the rotorcraft exhibits Level 2 handling qualities in the yaw axis caused by phase lag. The combined effect of the QFT feedback design following the implementation of low-order, dynamic crossfeed compensators successfully decouples ten of twelve off-axis channels. For the other two channels it was not possible to find a single, low-order crossfeed that was effective. This is an area to be investigated in future research.

Tischler, Mark B.↗
NASA NTRS1995

Computational Investigation of Tangential Slot Blowing on a Generic Chined Forebody

The effect of tangential slot blowing on the flowfield about a generic chined forebody at high angles of attack is investigated numerically using solutions of the thin-layer, Reynolds-averaged, Navier-Stokes equations. The effects of jet mass now ratios, angle of attack, and blowing slot location in the axial and circumferential directions are studied. The computed results compare well with available wind-tunnel experimental data. Computational results show that for a given mass now rate, the yawing moments generated by slot blowing increase as the body angle of attack increases. It is observed that greater changes in the yawing moments are produced by a slot located closest to the lip of the nose. Also, computational solutions show that inboard blowing across the top surface is more effective at generating yawing moments than blowing outboard from the bottom surface.

Agosta-Greenman, Roxana M.↗
NASA NTRS1996

X-29A Lateral-Directional Stability and Control Derivatives Extracted From High-Angle-of-Attack Flight Data

The lateral-directional stability and control derivatives of the X-29A number 2 are extracted from flight data over an angle-of-attack range of 4 degrees to 53 degrees using a parameter identification algorithm. The algorithm uses the linearized aircraft equations of motion and a maximum likelihood estimator in the presence of state and measurement noise. State noise is used to model the uncommanded forcing function caused by unsteady aerodynamics over the aircraft at angles of attack above 15 degrees. The results supported the flight-envelope-expansion phase of the X-29A number 2 by helping to update the aerodynamic mathematical model, to improve the real-time simulator, and to revise flight control system laws. Effects of the aircraft high gain flight control system on maneuver quality and the estimated derivatives are also discussed. The derivatives are plotted as functions of angle of attack and compared with the predicted aerodynamic database. Agreement between predicted and flight values is quite good for some derivatives such as the lateral force due to sideslip, the lateral force due to rudder deflection, and the rolling moment due to roll rate. The results also show significant differences in several important derivatives such as the rolling moment due to sideslip, the yawing moment due to sideslip, the yawing moment due to aileron deflection, and the yawing moment due to rudder deflection.

Iliff, Kenneth W.↗
NASA NTRS1997

Moving-Base Simulation Evaluation of Control/Display Integration Issues for ASTOVL Aircraft

A moving-base simulation has been conducted on the Vertical Motion Simulator at Ames Research Center using a model of an advanced, short takeoff and vertical landing (STOVL) lift fan fighter aircraft. This experiment expanded on investigations during previous simulations with this STOVL configuration with the objective of evaluating (1) control law modifications over the low speed flight envelope, (2) integration of the throttle inceptor with flight control laws that provide direct thrust command for conventional flight, vertical and short takeoff, and flightpath or vertical velocity command for transition, hover, and vertical landing, (3) control mode blending for pitch, roll, yaw, and flightpath control during transition from wing-borne to jet-borne flight, and (4) effects of conformal versus nonconformal presentation of flightpath and pursuit guidance symbology on the out-the-window display for low speed STOVL operations. Assessments were made for takeoff, transition, hover, and landing, including precision hover and landing aboard an LPH-type amphibious assault ship in the presence of winds and rough seas. Results yielded Level 1 pilot ratings for the flightpath and vertical velocity command modes for a range of land-based and shipboard operation and were consistent with previous experience with earlier control laws and displays for this STOVL concept. Control mode blending was performed over speed ranges in accord with the pilot's tasks and with the change of the basic aircraft's characteristics between wing-borne and hover flight. Blending of yaw control from heading command in hover to sideslip command in wing-borne flight performed over a broad speed range helped reduce yaw transients during acceleration through the low speed regime. Although the pilots appreciated conformality of flightpath and guidance symbols with the external scene during the approach, increased sensitivity of the symbols for lateral path tracking elevated the pilots' control activity in the presence of turbulence. The pilots preferred the choice of scaling that was originally established during the display development and in-flight evaluations.

Franklin, James A.↗
NASA NTRS1958

Hovering and Transition Flight Tests of a 1/5-Scale Model of a Jet-Powered Vertical-Attitude VTOL Research Airplane

An experimental investigation has been made to determine the dynamic stability and control characteristics of a 1/5-scale flying model of a jet-powered vertical-attitude VTOL research airplane in hovering and transition flight. The model was powered with either a hydrogen peroxide rocket motor or a compressed-air jet exhausting through an ejector tube to simulate the turbojet engine of the airplane. The gyroscopic effects of the engine were simulated by a flywheel driven by compressed-air jets. In hovering flight the model was controlled by jet-reaction controls which consisted of a swiveling nozzle on the main jet and a movable nozzle on each wing tip; and in forward flight the model was controlled by elevons and a rudder. If the gyroscopic effects of the jet engine were not represented, the model could be flown satisfactorily in hovering flight without any automatic stabilization devices. When the gyroscopic effects of the jet engine were represented, however, the model could not be controlled without the aid of artificial stabilizing devices because of the gyroscopic coupling of the yawing and pitching motions. The use of pitch and yaw dampers made these motions completely stable and the model could then be controlled very easily. In the transition flight tests, which were performed only with the automatic pitch and yaw dampers operating, it was found that the transition was very easy to perform either with or without the engine gyroscopic effects simulated, although the model had a tendency to fly in a rolled and sideslipped attitude at angles of attack between approximately 25 and 45 deg because of static directional instability in this range.

Smith, Charles C., Jr.↗
NASA NTRS1961

Hovering and Transition Flight Tests of a 1/5-Scale Model of a Jet-Powered Vertical-Attitude VTOL Research Airplane

An experimental investigation has been made to determine the dynamic stability and control characteristics of a 1/5-scale flying model of a jet-powered vertical-attitude VTOL research airplane in hovering and transition flight. The model was powered with either a hydrogen peroxide rocket motor or a compressed-air jet exhausting through an ejector tube to simulate the turbojet engine of the airplane. The gyroscopic effects of the engine were simulated by a flywheel driven by compressed-air jets. In hovering flight the model was controlled by jet-reaction controls which consisted of a swiveling nozzle on the main jet and a movable nozzle on each wing tip; and in forward flight the model was controlled by elevons and a rudder. If the gyroscopic effects of the jet engine were not represented, the model could be flown satisfactorily in hovering flight without any automatic stabilization devices. When the gyroscopic effects of the jet engine were represented, however, the model could not be controlled without the aid of artificial stabilizing devices because of the gyroscopic coupling of the yawing and pitching motions. The use of pitch and yaw dampers made these motions completely stable and the model could then be controlled very easily. In the transition flight tests, which were performed only with the automatic pitch and yaw dampers operating, it was found that the transition was very easy to perform either with or without the engine gyroscopic effects simulated, although the model had a tendency to fly in a rolled and sideslipped attitude at angles of attack between approximately 25 deg and 45 deg because of static directional instability in this range.

Smith, Charles C., Jr.↗
NASA NTRS1959

Tables for the Rapid Estimation of Downwash and Sidewash Behind Wings Performing Various Motions at Supersonic Speeds

Equations for the downwash and sidewash due to supersonic yawed and unswept horseshoe vortices have been utilized in formulating tables and charts to permit a rapid estimation of the flow velocities behind wings performing various steady motions. Tabulations are presented of the downwash and sidewash in the wing vertical plane of symmetry due to a unit-strength yawed horseshoe vortex located at 20 equally spaced spanwise positions along lifting lines of various sweeps. (The bound portion of the yawed vortex is coincident with the lifting line.) Charts are presented for the purpose of estimating the spanwise variations of the flow-field velocities and give longitudinal variations of the downwash and sidewash at a nuMber of vertical and spanwise locations due to a unit-strength unswept horseshoe vortex. Use of the tables and charts to calculate wing downwash or sidewash requires a knowledge of the wing spanwise distribution of circulation. Sample computations for the rolling sidewash and angle-of-attack downwash behind a typical swept wing are presented to demonstrate the use of the tables and charts.

Bobbitt, Percy J.↗