THE EFFECTS OF HORIZONTAL-TAIL POSITION ON THE LONGITUDINAL AERODYNAMIC CHARACTERISTICS AT TRANSONIC SPEEDS OF A VARIABLE-SWEEP AIRCRAFT HAVING AN INBOARD PIVOT

A variable-wing-sweep aircraft having an inboard pivot location and a chord-plane tail (configuration VII-C) was tested at transonic speeds. Performance and longitudinal stability and control characteristics were determined over a Mach number range from 0.60 to 1.20 and for wing-sweep positions of 25, 50, and 85 degrees. Comparisons with previously published data of the same configuration but with the horizontal tail in a low position (configuration VII-B) were made to evaluate the effect of tail height. The aerodynamic efficiency was highest for the low tail arrangement. The results indicated only minor effects of tail height on longitudinal stability except for the low-speed moderate lift condition with the wings in the 25-degree position where the chord-plane tail indicated a slight pitch-up tendency. The longitudinal control effectiveness of the chord-plane tail configuration decreased rather rapidly at supersonic speeds because an elevator had to be resorted to as a result of the wing-tail mating.