AND OSCILLATORY CONDITIONS

An experimental investigation has been made to determine the effects of vertical fins near the nose of the fuselage on the directional and dsmping-in-yaw stability derivatives of a swept-wing airplane model. The investigation included measurements of these characteristics for the model oscillating about a vertical axis in a steady airstresn. The results of this investigation showed that, for angles of attack up to at least 12°, fins placed above the fuselage nose decreased the directional stabillty but increased the damping in yaw of the model in both the steady-state and oscillatory conditions because of the sidewash acting on the tail as welIlas the direct lift of the fins. Also, fins placed above the fuselage nose were more effective in increasing the steady-state or oscillatory damping in yaw than the addition of an equal * amount of area at the vertical tail. Fins pticed below the nose of the fuselage decreased the directional a stability snd increased the damping in yaw to a lesser extent than fins placed above the fuselage nose in the steady-state condition but reduced the dsmoim in v“awin the oscillator condition. For a constamt value of dire&i&al;t*ility, the dampin ~ in yaw by the use of a fin placed above the nose of in tail size