Showing papers on "Pitching moment published in 1970"

Measurement of Aerodynamic Forces on an Oscillating Airfoil

Abstract: : A literature survey was conducted to determine the state of the art of measuring and predicting aerodynamic characteristics of oscillating airfoils. Aerodynamic forces on a two-dimensional NACA 0012 airfoil oscillating sinusoidally in pitch were measured by two techniques. The forces were obtained from pressure measurements and by means of strain gage balances. Pressure measurements were made on the airfoil oscillating in pitch about the quarter-chord point at various mean angles of attack. Strain gage balance readings were obtained for models with pitch axis located at 25, 37, and 50 percent chord points oscillating about various mean angles. Direct force measurements were employed in an effort to obtain drag data. Instantaneous pressure distributions are presented for representative oscillating conditions.

Supersonic Magnus Measurements of the 10-Caliber Army-Navy Spinner Projectile with Wrap-Around Fins

Abstract: : A research configuration was formed by attaching wraparound fins in a cruciform arrangement to a 10-caliber Army-Navy spinner projectile. This configuration was tested in a supersonic tunnel to get the Magnus force and moment, as well as the normal force and pitching moment. Model spin rate was generated by means of fin cant.

An Investigation of the Aerodynamic Characteristics of the AGARD Model B for Mach Numbers from 0.2 to 1.0

Abstract: : A test was conducted to determine the aerodynamic characteristics of the AGARD Model B calibration model at Mach numbers from 0.2 to 1.0 for angles of attack from -4 to +24 deg. The tunnel blockage of the model at zero angle of attack was 0.15 percent. The data showed no evidence of tunnel interference and are considered to be interference free. The data agreed with other published data obtained at Mach numbers above 0.7. The curves of lift coefficient and pitching moment were found to be nonlinear near zero lift at Mach numbers below 1.0. Therefore, the lift curve slope and the neutral-point location should be used with caution when comparing data.

The determination of unsteady aerodynamics of a two-dimensional jet-flap wing.

Abstract: : One of the purposes of the study was to conduct wind-tunnel tests on a two-dimensional, oscillating, jet-flap airfoil to determine the unsteady forces, moments, and pressure distributions. These tests were to (1) provide data for testing the validity of the theoretical results, and (2) to furnish guide-lines for the further development of unsteady jet-flap airfoil theory. The study was also to extend the solutions to the general theoretical equations describing the unsteady motions of a jet-flapped airfoil executing simple harmonic pitching motions. The attainment of these objectives was pursued in three phases. The first consisted of the development, calibration and testing of the model and its recording system. The second phase dealt with the theoretical effort required to allow computation of the lift and moment acting on a two-dimensional jet-flap airfoil executing harmonic pitching motions. The third and final phase consisted of the correlation of theory and experiment and the assessment of the theory. (AUTHOR)

An experiment to determine density variations in the earth's atmosphere and other atmospheric and aerodynamic information

Abstract: Atmospheric density variations and functional dependence of aerodynamic moment coefficient on incident angle from Saturn Workshop flight experiment

Force calibration of AGARD B model in transonic flow mach numbers

Abstract: Lift, drag and pitching moment characteristics of AGARD model B obtained from the 41 x 41 Trisonic Tunnel in the transonic Mach number range are presented and compared with the results of other tunnels. The results obtained were found to compare well with the interference free13; results of AEDC tunnel.

Longitudinal stability control device for fixed wing aircraft

Abstract: This device permits the aft center of gravity loading limit of an aircraft to be increased beyond its normal range without reducing the location of the most forward center of gravity loading limit. The means by which this is accomplished comprises an elongated spring member which has one end connected to the underside of the elevator control surface and which has its other end connected to a spring tension adjusting linkage mounted in the aircraft. The adjusting linkage causes the spring to pull the elevator downwardly to increase the nose down pitching moment about the center of gravity of the aircraft when the device senses a nose up pitch attitude, and releases the tension in the spring in response to a nose down condition. The device includes a feedback member which acts to relocate the spring member to hold the elevator in the desired position in order to trim the aircraft for a given center of gravity and airspeed.

A Wind-Tunnel Investigation of the Aerodynamic Environment of a Full Scale Helicopter Rotor in Forward Flight

Abstract: : Aerodynamic data were measured at one blade radius station as the initial phase of a program designed to define the aerodynamic environment over the entire rotor disc. The rotor was instrumented to measure stagnation point location, radial flow direction, and pressure distributions. These data were then used to determine angle of attack; effective airfoil profile; section normal force, chord force, and pitching moment; and stall and unsteady aerodynamics effects. The test data were compared with two-dimensional empirical data and theory. Four cases were analyzed in some detail. They showed the variations in airfoil pressure, angle of attack, and radial flow as functions of aximuth and advance ratio. Deviations in the pressure distributions between test data and theory are believed to be due to the rotor wake and unsteady aerodynamic effects.

Jet Circulation Control Airfoil for VTOL Rotors

Abstract: Based on the potential flow theory calculation, the capacity of the air supply, the limitation of the internal pressure of the model and the limitation due to the compressibility effect of the jet stream at high velocities, the elliptical airfoils of 18 and 12% thickness ratios were designed and constructed. Experimental investigations for both models with trailing-edge jets include force and pitching moment measurements. In addition, static pressure measurements were made in both span wise and chord wise directions. These results were used to compare with available theories as well as other experimental data. Circulation control with dual jets for the elliptical airfoil of 18% thickness ratio was tested with very satisfactory results. The determination of the aerodynamic response of the airfoil model to cyclic changes in jet mass flow was also made. The cyclic results were very satisfactory and are presented in the form of pulsating lift coefficient, drag coefficient, and pressure coefficient as a function of pulsating jet coefficient.

C-5A Main Landing Gear Bogie Pitching Control

Abstract: The C-5A six-wheel main landing gear bogie, as the result of a high flotation requirement, poses a problem for designing a wheel braking torque compensating mechanism which stabilizes bogie pitching during braking. For ground operation, the bogie is also required to pitch ±12° with respect to the shock strut. During retraction of the main gear, however, the bogie is required to be at a right angle with the shock strut for the first 60% of the gear travel and then rotate about the pitch pivot with a defined pattern for 85°. To meet these requirements, avoiding weight penalty and complexity, a single braking torque link is used; and the bogie pitching control for on ground and in air operation is simplified to a two-stage pneumatic centering spring cartridge with the utilization of the torque compensating mechanism and a guiding track in the wheel well.

Isolated Cyclic Pitch Propeller: Results of Wind Tunnel Test

Abstract: : The report presents the results of wind tunnel test BVWT 057 performed in the Boeing Vertol V/STOL wind tunnel on an isolated 3-bladed cyclic pitch propeller with a total activity factor of 480. The primary objectives of the test were to determine: the pitching moment capability from the propeller over a wide shaft angle range from 0 up to 120 deg through the transition flight regime of a tilt wing aircraft and, the effect of cyclic pitch on power. The effects of cyclic pitch on propeller thrust, normal force, yawing moment, and side force were also measured.

Vehicle flight scaling with aerodynamic flow hysteresis

Abstract: Missile oscillations in plane during pitching moment hysteresis, discussing test coefficients suitability for predicting motion

Barge trains in a coastal seaway, part 1: model tests in oblique seas

Abstract: Tests of a 1/50-scale model of push-tow barge trains were carried out under various wave conditions, including wave-to-heading angle change, to obtain forces on tow connections and motions of the train. Test results are presented for lateral bending moment, longitudinal and vertical forces on tow connections and for oscillatory motions such as roll, pitch and heave, with variations in wave conditions (wave length, wave height and wave-to-heading angle), number of barges, types of connections (hinge, short and long linkage), loading conditions and speeds. Test results of forces and moments indicate that the lateral bending moment is the most critical component in the resultant force generated on connections of barge trains in waves. For example, the maximum magnitude of measured moment coefficient (moment/(beam x one barge displacement)) was approximately 0.25 at the middle connection of the three-barges and tug train in moderate waves (wave height/wave length = 1/100) at wave-to-heading angles of 120 degrees and 60 degrees. The maximum longitudinal force coefficient (force/one barge displacement) obtained in tests was approximately 0.05 in moderate head seas (wave height/wave length = 1/100). Lateral bending moment and longitudinal and vertical forces were roughly doubled when the wave height relative to the wave length was increased from 1/100 to 1/50.

Effects of wing elevation, incidence, and camber on the aerodynamic characteristics of a representative hypersonic cruise configuration at Mach numbers from 0.65 to 10.70

Abstract: Wing elevation, incidence, and chamber effects on aerodynamic characteristics of representative hypersonic cruise configuration at Mach numbers from 0.65 to 10.70

Static and dynamic pitching moment measurements on a family of elliptic cones at Mach number 11 in helium

Abstract: Static and dynamic pitching moment measurements were made on a family of constant volume elliptic cones about two fixed axes of oscillation in the NAE helium hypersonic wind tunnel at a Mach number of 11 and at Reynolds numbers based on model length of up to 14 million. Viscous effects on the stability derivatives were investigated by varying the Reynolds number for certain models by a factor as large as 10. The models investigated comprised a 7.75 deg circular cone, elliptic cones of axis ratios 3 and 6, and an elliptic cone with conical protuberances.

Investigation of Unsteady Aerodynamic Forces Acting on a Thin Aerofoil at Stall Flutter

Abstract: The problem of high-angle-of attack aerodynamic derivatives is approached as follows: Qualitative equation of aerodynamic derivatives are derived, assuming that the vortex sheet theory is applicable approximately to the flow field with the separation around a vibrating thin aerofoil at high-angle-of-attack. The one of above equations, the equation of pitching moment derivative, is examined and compared with experimental data. And then, theoretically undeterminate parameters in the equation are estimated.Using the variables and constants determined above, lift derivatives are predicted and compared with experimental values.

Four Prop Tilt Wing with Cyclic Pitch Propellers: Results of Full Span Wind Tunnel Test/Phase 1

Abstract: : The report presents the results of wind tunnel test BVWT 061 (Phase I test of two phase test program) performed in the Boeing-Vertol V/STOL wind tunnel on a powered four prop tilt wing full span model equipped with cyclic pitch propellers for longitudinal control. Items evaluated include cyclic pitch control in hover (in and out of ground effect), yaw control in performance, plus basic longitudinal stability and control throughout transition with a high horizontal tail. Propeller hub pitching moment and normal force were also measured during this test so that in conjunction with a previous isolated propeller test,the influence of the wing/flaps/fuselage on the propeller forces and moments could be determined.

An experimental investigation of rotor forces and flow field in the vicinity of a step ground plane

Abstract: : The rotor force parameters considered were thrust, torque, pitching moment, and normal force, for the simulated flight conditions of hover, takeoff, and landing. The flow parameters investigated included tip vortex trajectories and streamline patterns. Additional studies were made to consider the effects of rotor blade mismatching upon thrust and power requirements of a rotor system. (Author)

The effects of products of inertia on the roll behavior of ballisticre-entry vehicles

Abstract: Ballistic reentry vehicles having lateral center-of-gravity offsets (mass asymmetries) exhibit anomalous roll behavior a s a result of tr im angle-generated lateral aerodynamic forces. The t r im angles caused by mass and aerodynamic asymmetries have been thoroughly investigated. However, inertia asymmetries, which result when the principal axes of the vehicle become inclined with respect to the body reference axes, a r e a source of t r im angle which has not been considered. A linear quasi-steady theory is developed which demonstrates that inertia asymmetries are: (1) more effective than equivalent mass and aerodynamic asymmetries in generating t r im angles over the super-resonant region of reentry flight; (2) equally a s effective at resonance; and (3) less effective over the subresonant region. The predictions of this theory a re verified by numerical integrations of the complete equations of motion and by three angular degree-of-freedom wind tunnel experimental results. L, Nomenclature C. g. Center of gravity Axial force coefficient, axial forcelq'S C A Normal force coefficient, normal force/q's CN C Normal force slope coefficient, N a acN/aa. l / r a d Yawing moment coefficient, yawing moment / q'Sd Yawing moment coefficient at p = 0 ' n