Pitching moment

About: Pitching moment is a research topic. Over the lifetime, 3213 publications have been published within this topic receiving 38721 citations.

High lift, low pitching moment airfoils

Abstract: This invention relates to airfoils which have particular application to rotors of helicopters and rotorcraft and to aircraft propellers. Two airfoil profiles, the RC(4)XX and RC(5)XX are shaped to permit (1) the development of high air loads without causing an extensive separation of the boundary layer air, (2) a distribution of airloads which results in a near zero pitching moment coefficient about the quarter chord for a range of lift coefficients from -0.2 to 1.0 for Mach numbers up to 0.63, and (3) the development of a local supersonic flow field which is so shaped that the wave losses are minimal until higher free stream Mach numbers over a range of lift coefficients from 0.0 to 0.30. Thus, both airfoils have high maximum lift coefficients, low pitching moment coefficients, and high drag divergence Mach numbers to result in improved rotor or propeller performance. The two invention airfoils are related in shape and purpose. The use of either airfoil by itself or the use of one in conjunction with the second would depend upon the design requirements of the particular application.

Forward-Flight Analysis of Slatted Rotors Using Navier-Stokes Methods

Abstract: The objective of this study is to evaluate the aerodynamic effects of leading-edge slats on rotor blades under high-speed forward- ight conditions. A partial-span leading-edge slat is proposed for the inboard portion of the existing UH-60A rotor. Some two-dimensional slat studies are done to optimize the slat orientation at low subsonic Mach numbers. A multizone unsteady three-dimensional compressible Navier ­ Stokes solver is developed to compute such rotor/slat conŽ gurations. The rotor wake is captured from Ž rst principles. Some forward- ight results are presented for the UH-60A slatted rotor and compared with the baseline rotor case. The surface pressures and the force coefŽ cients indicate that the slat is beneŽ cial in reducing the retreating side dynamic stall. It was found that the slat reduces the torque and pitching moments on the retreating side compared to the baseline conŽ guration.

Shock inducing pod for causing flow separation.

Abstract: A wing-mounted pod (30) for preventing an unstable increase in the pitching moment of a swept-wing aircraft due to increasing speed and angle of attack. This invention is for use on a swept-wing aircraft of the type having nonlinear, unstable increase in its pitching moment due to a loss of lift at the outboard wing (16) above a predetermined angle of attack at high Mach numbers. For an aircraft having a single, strut-mounted engine (26, 29) on each wing, the pod (30) is placed along the intersection of the upper surface of the wing (12) and the inboard side of the engine mounting strut (26). The pod (30) prevents an increase in the pitching moment by inducing the formation of a shock (S) in the air flowing over the upper surface of the inboard wing (14) at the same angle of attack at which the outboard wing (16) loses lift. The shock causes localized flow separation on the inboard wing, thereby preventing the increase in pitching moment otherwise experienced by the aircraft.