REPUBLIC OF SERBIA

MINISTRY OF DEFENCE

www.mod.gov.rs

MINISTRY OF DEFENCE

Material Resources Sector

Defensive Technologies Department

Military Technical Institute

www.vti.mod.gov.rs

measurement of STABILITY derivativeS IN YAW using THE FORCED oscillatory technique

marija samardžić

Military Technical Institute, Belgrade, majasam@ptt.rs

Zoran Anastasijević

DRAGAN mARINKOVSKI

BILJANA ILIĆ

DIJANA DAMLJANOVIĆ

zoran Rajić

dušan ćurčić

Military Technical Institute, Belgrade,

Abstract: In the measurement of damping derivatives using the forced oscillation technique experiments are based on giving a small amplitude oscillatory motion to a model in the primary degree of freedom. This paper describes mathematical model for measurement of the direct damping derivative in yaw in the T-38 wind tunnel.  Equations for determination of the cross derivative due to yawing are presented, too. The apparatus for the stability derivatives measurement in the T-38 wind tunnel provides a primary oscillatory motion in pitch with secondary (resulting) forced oscillatory motion in yaw and roll. With the apparatus rotated 90° around its longitudinal axis (in relation to both model and internal wind tunnel balance) a primary oscillatory motion in yaw is provided with secondary forced oscillatory motions in pitch and roll. Excitation moments, causative moments, amplitude and frequency of the primary and secondary motion,  as well as the in-phase and out-phase components of the secondary motions with respect to the primary motion are measured in these tests. The T-38 wind tunnel experimental data for the Standard Dynamic Model at Mach number 0.6 are shown.

Key words: wind tunnel, forced oscillations, direct damping derivative, cross derivative.