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An outboard-horizontal-stabilizer aircraft configuration is one in which the horizontal and vertical tail surfaces are supported by booms projecting downwind from each wing tip of a monoplane such that these surfaces lie within the upwash and inwash flow generated by each wing tip. The horizontal surfaces project, therefore outboard of each wing tip, with a vertical surface mounted above each boom. A description is given of the inherent advantage of an outboard-horizontal-stabilizer configuration. A theoretical treatment, closely based on fundamental concepts, is presented that is designed to facilitate the evaluation of the net drag of an outboard-horizontal-stabilizer configuration in terms of the wing-lift coefficient of an equivalent conventional configuration of equal lift. The theoretical treatment is applied to several outboard-horizontal-stabilizer-type configurations to evaluate flight performance in terms of lift/drag versus wing-lift coefficient. These performances are compared with the idealized performances of equivalent conventional configurations. It was found that, depending upon the details of the basis of the comparison, the outboard-horizontal-stabilizer configurations were from 30 to 50% more efficient in terms of lift/drag than their conventional alternatives. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to analyze and discuss the performance and stability of a tailless micro aerial vehicle with flexible articulated wings. The dihedral angles can be varied symmetrically on both wings to control the aircraft peed independently of the angle of attack and flight-path angle, while an asymmetric dihedral setting can be used to control yaw in the absence of a vertical tail. A nonlinear aeroelastic model is derived, and it is used to study the steady- state performance and flight stability of the micro aerial vehicle. The concept of the effective dihedral is introduced, which allows for a unified treatment of rigid and flexible wing aircraft. It also identifies the amount of elasticity that is necessary to obtain tangible performance benefits over a rigid wing. The feasibility of using axial tension to stiffen the wing is discussed, and, at least in the context of a linear model, it is shown that adding axial tension is effective but undesirable. The turning performance of an micro aerial vehicle with flexible wings is compared to an otherwise identical micro aerial vehicle with rigid wings. The wing dihedral alone can be varied asymmetrically to perform rapid turns and regulate sideslip. The maximum attainable turn rate for a given elevator setting, however, does not increase unless antisymmetric wing twisting is employed. [ABSTRACT FROM AUTHOR]

Traditional extremum seeking depends on adding a perturbation to the control input, but it is untenable to continuously perturb the throttle in a controller meant to minimize fuel consumption. Inspired by a recent application of extremum seeking to a fusion reactor where internal nonperiodic perturbations were employed in the seeking process, a novel variant of extremum seeking is proposed that uses naturally occurring stochastic disturbances in lieu of the traditionally added perturbation signal. Relying on airspeed perturbations from atmospheric turbulence to reveal the local slope of the drag curve, the scheme induces a gradient descent to the minimum drag speed. Using stochastic averaging, it is proven analytically that the extremum-seeking controller stabilizes airspeed to the minimum drag speed, with an average offset proportional to the third derivative of the drag curve and the variance of the airspeed. Brief simulation results illustrate the performance of the algorithm. [ABSTRACT FROM AUTHOR]

Numerical simulations and experiments were conducted to analyze the dynamic characteristics of a newly developed bellows-type stabilizer, which maintains a steady propellant mixture ratio in the gas generator of a liquid rocket engine. A nonlinear mathematical model of the stabilizer and a linear version of the model were developed. The dynamic characteristics predicted by the linear model showed good agreement with experimental results, thus proving the validity of the model. It was found through sensitivity analyses that the main design parameters affecting the dynamic characteristics of the stabilizer system are the orifice diameter and the length of the pilot line. [ABSTRACT FROM AUTHOR]

Focuses on a study that discussed the estimation of the low-speed sidewash gradient on a vertical stabilizer using a vortex model. Theory used in evaluating the wingtip vortex strength and spacing; Result that can occur because the sidewash gradient is proportional to the wing lift coefficient.