A stability and control augmentation system designed analytically in Reference (1) was evaluated on the NASA Ames Flight Simulator for Advanced Aircraft. Linear optimal control theory was applied to determine appropriate feedback gains for the stability augmentation system. A least square design method was then applied to determine partial crossfeed gains for the control augmentation system. The augmentation system thus designed was evaluated experimentally in the piloted simulation tests. Handling qualities of the augmented as well as the unaugmented helicopter were investigated in the following flight tasks involving both visual and instrument flights: NOE (nap-of-the-earth) maneuvers, VOR approaches and a set of basic maneuvers. Experimental data show that handling qualities of the augmented helicopter were substantially improved as compared with those of the basic helicopter.
Flowfields about a scramjet inlet model were numerically simulated by the Thin-Layer Navier-Stokes equations, and effect of inflow boundary layer thickness was investigated. The computations were conducted for inflow Mach number of 3.4. Although pressure at the throat region is relatively constant for various boundary layer thickness, corresponding flow pattern near the top wall was very different to each other, and the total pressure recovery decreased with the boundary layer thickness. The spilled impulse function increased with the thickness of inflow boundary layer, and stream thrust function of the spilled air slightly increased with the boundary layer thickness. The tendency was due to the increase of the separating region with the boundary layer thickness.
Unsteady aerodynamic characteristics of rolling delta wings were investigated by measuring normal forces and rolling moments acting on delta wing models of 14 and 7 degree apex half angles, which are forced to oscillate sinusoidally in roll. The experiment was conducted in a low-speed wind tunnel at several roll frequencies. Vortex breakdown is observed in more limited range of one roll cycle in forced oscillation than in static test, therefore, normal force and restoring rolling moment increase with applying roll oscillation. With increasing the roll rate, energy is supplied from rolling wings to free stream at low angles of attack, but energy is supplied from free stream to rolling wings at higher angle of attack, which will result in wing rock. The effects on wing rock of roll damping, the convective time lag in separated vortex movements and the time lag in vortex breakdown are also discussed in relation to the direction of roll hysteresis curves.
This paper considers a numerical method for optimal control problems which are solved by using a mathematical programming formulation. The sensitivity differential equations are obtained to calculate the derivative information of the objective and constraint functions. Numerical examples of the accent trajectory problem of a spaceplane compare the proposed method with the conventional method which calculates derivatives using finite difference approximation. The results demonstrate the improvement of accuracy and computational efficiency of the present method.
In sandwich plates, the strong demand of both lightweight and high bending rigidity makes its face sheet very thin and core very high. In such plates, resonance frequencies of in-plane vibration become very low. Consequently it is necessary to consider in-plane vibration as well as bending vibration. But there are few studies related to in-plane vibration problems. In this paper, the in-plane vibration characteristic of the flat plate which is made of the thick Al honeycomb core and thin Al face is evaluated by both the finite element method analysis and the experiment. Both results are compared with each other and both natural frequencies and vibration modes by the analysis coincides very well with those by the experiment.