著者

HORIKOSHI Jiro

出版者

宇宙航空研究開発機構

雑誌

ISAS report (ISSN:03721418)

巻号頁・発行日

vol.30, no.5, pp.115-194, 1965-03

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The present paper is intended to show that a deliberate reduction of the elevator control system stiffness effectively improves the flying qualities relevant to longitudinal maneuver of a piloted airplane (excluding a fully power controlled airplane with an at present commonly used feel mechanism) through the matching of the stability and control characteristics of the airplane with the physical and perceptive characteristics of the pilot. A properly selected stiffness of the control system will cause upward shift and flattening of the curves of stick travel per airplane response versus speed over wide ranges of speed and normal acceleration, and hence it will add a good measure of longitudinal maneuverability sensed by the pilot to the already established stick force per airplane response. Analytical investigations are made of the effect of the stiffness on the stick travel per airplane response in steady longitudinal maneuvers, and on the frequency response characteristics of the airplane to stick movement during unaccelerated flight. Numerical calculations, including an analog computer analysis of the effect on the responses stated above in the initial or transient state of longitudinal control, are made based on the data of a prototype airplane for which the author was responsible. The developments of the concept and the flight-tests of the said airplane which took place about twenty-six years ago are briefly described. Both results are fairly coincident with each other, and are further backed-up by ample service experiences on this airplane and its successors. Thus the effectiveness of the concept is sufficiently demonstrated. Also investigations are made of such characteristics as might be apprehended by some people to be adversely affected by the reduced stiffness. Confirmation is made that it is applicable to a subsonic airplane which is normally designed and not seriously affected by aerodynamic compressibility. It may be remarked that, being easy to apply and extremely simple in its applied form, the concept may give neat solutions to some of the problems in the field of mechanical as well as aeronautical engineering, in which means to provide self-adaptability and/or to soften responses are required. A spring tab may be cited as the second successful application of the concept to an airplane within the author's knowledge.