FLIGHT DETERMINATION OF THE LONGITUDINAL STABILITY IN ACCELERATED MANEUVERS AT TRANSONIC SPEEDS FOR THE DOUGLAS D-558 =Ⅱ RESEARCH AIRPLANE INCLUDING THE EFFECTS OF AN OUTBOARD WING FENCE

摘要

Flight tests were performed with the Douglas D-558-II research airplane in the clean configuration to investigate the longitudinal sta-bility characteristics of the airplane in accelerated flight at tran¬sonic speeds. The airplane was tested in the original configuration and also in a modified configuration (with outboard wing fences at 0-73 wing semispan) in an attempt to alleviate the reduction of stability encoun-tered with the original airplane configuration at moderate lift coefficients.nAt moderate values of angle of attack, the airplane experienced a decrease in stability which was accompanied by a rapid uncontrolled ~ increase in the angle of attack and normal acceleration (termed "pitch-up"). The normal-force coefficient for the occurrence of the reduction in stability was found for the original airplane configuration to decrease from a value of 0.91 to 0.47 as the Mach number increased from 0.52 to 0.94. The incorporation of outboard fences appeared to provide only a slight improvement in stability over the original airplane configuration.