Mauverability and Control Surface Strength Criteria for Large Airplanes

Abstract

A method has been developed which makes possible the determination of the horizontal tail strength required by the basic flight envelope which governs the strength of the wings. The method involves only the use of simple wind-tunnel data. I t is shown tha t the maneuvering tail loads can be obtained without reference to the effect of the trimming tab. The controllability in pitch should be sufficient to subject the airplane to the flight envelope load factor a t any speed. The controllability criterion for the vertical tail is tha t the critical control speed with flaps in the landing position should not exceed the landing speed, and with the flaps in the take-off position, should not exceed take-off speed. The strength of the vertical tail should be based upon the use of the tab angle for trim with engines inoperative, together with a maneuvering pedal force. I t is suggested tha t the airplane should not run out of aileron control a t a higher speed than it runs out of rudder control. Rational load criteria for the ailerons have not been developed. I t must be realized tha t the methods presented are in a crude stage of development, and that much refinement will be necessary before they can be regarded as completely satisfactory. I t is felt, however, tha t the general principles discussed will afford reasonable bases for maneuverability and maneuvering load criteria.