Pitching moment

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

Aerodynamic Hinge Moment Coefficient Estimation Using Automatic Fly-by-Wire Control Inputs

Abstract: This paper describes the modeling and parameter estimation of the aileron and elevator flight control system of TU Delft’s Cessna Citation II laboratory aircraft. The flight test data originate from maneuvers performed autonomously with a custom-designed experimental fly-by-wire system. The identification of the aerodynamic hinge moment coefficients will be of special interest, as these hinge moments greatly affect the in-flight performance of the flight control system. First, the elevator and aileron flight control system models will be presented, introducing the main parameters that need to be determined. Most of the parameters reflect the mechanical properties and can be obtained through some cleverly-designed ground tests, which are discussed next. The hinge moment coefficients can only be determined through flight tests. The paper continues with a description of the optimal input signals used to generate flight data for the parameter estimation procedure. The flight test setup will be introduced briefly, after which the results of the hinge moment coefficient parameter estimation are summarized. Finally, the validity of the resulting flight control system models for elevator and aileron are shown.

Simulation Analysis of the Controllability of a Tandem Ducted Fan Aircraft

Abstract: A generic simulation model was developed for stability / control analysis and real-time simulation of ducted fan aircraft. The generic simulation model features a modified inflow model for ducted rotors, a basic model of control vane forces and moments, and empirical correction factors to account for duct thrust augmentation, duct pitching moment, and flow turning effects. Two empirical flow turning efficiency factors, one applied before the plane of the rotor and the other from freestream to far-wake flow, were investigated. A model of duct pitching moment was developed in which the duct thrust offset normalized by the rotor radius is given as a function of airspeed. Wind tunnel data and literature from several sources have been analyzed and compared in order to refine the pitching moment model and tune the empirical factors. Validation of the simulation model is provided through correlation studies with experimental data of a 29-inch ducted fan UAV. Steady-state and trim results obtained using the generic simulation model are presented and discussed.

Rotary-wing blade of rotary-wing aircraft

Abstract: A rotary-wing blade of a rotary-wing aircraft has an airfoil section which has an asymmetrical region of positive camber from its leading edge to its approximately 30-percent chord length point and an essentially symmetrical airfoil region from its 30-percent chord point to approximately its 90-percent chord length point. The region aft of the 90-percent chord point can be optionally curved or reflexed upward or downward to a limited degree. This blade has a large lift coefficient and a small pitching moment and is readily adaptable to meet various design conditions of lift coefficient and pitching moment.

Aerodynamic Performance of an Airfoil with Step-Induced Vortex for Lift Augmentation

Abstract: Physical and numerical experiments on flow developments around an NACA-0012 airfoil were conducted to explore the possibility of enhancing the airfoil's aerodynamic performance by vortex lift augmentation. The paper focuses on the effects of the separated flow and subsequent vortex formation, generated by backward-facing steps on pressure distributions and corresponding flow occurrences around the airfoil. Various step configurations are examined to determine their effect on lift and on lift-to-drag ratios. A discussion of the effects of main geometrical parameters of upper and lower surface steps on the airfoil performance, based on computational and physical flow visualization experiments, are presented. The results suggest that incorporation of backward-facing steps on the lower surface that are located at the midchord and extend back to the trailing edge with 50 depth of the airfoil chord may lead to considerable enhancements in lift coefficients and lift-to-drag ratios. The data produced may serve as...

Transonic Navier-Stokes Computations for a Spinning Body of Revolution

Abstract: : A zonal, implicit, time-marching Navier-Stokes computational technique has been used to compute three dimensional transonic flow fields over a projectile. Flow field computations have been performed at M = 0.94 for spin rates of 0 and 4900 rpm and at angles of attack, alpha = 0,4, and 10 degrees. All the computations have been performed on the Cray-2 supercomputer. Details of the flow field such as Mach number contours and surface pressure distributions are presented. Computer surface pressures are compared with available experimental data for the same conditions and the same configuration. Computer results show the large circumferential pressure distribution over the boattail region as well as the nonlinear effect of the angle of attack. Aerodynamic force and moment coefficients (normal force, pitching moment, Magnus force, and Magnus moment) have been obtained from the computed pressures and are compared with the data. The computed results are generally in good agreement with the data at low angle of attack for both nonspinning and spinning conditions. At high angle of attack the agreement is good for the nonspinning case and is less satisfactory for the spinning case.