Lateral oscillations occurring on the aircraft model of NASA TP 1803 at angles of attack ranging from 25 Π to 60 Π have been investigated in a low-speed wind tunnel for configurations including fuselage with wing or with a combination of wing and leadingedge extension (LEX) . The wind tunnel experiment was conducted in the range of Mach number from 0 ΠΈ 1 to 0 ΠΈ 2 , and the range of the Reynolds number based on the body diameter from 2 ΠΈ 8 Ο« 10 5 to 5 ΠΈ 6 Ο« 10 5 . The time-varying side force coef ficients , which may represent the displacements of oscillation in the lateral direction , were measured to obtain the root-mean-square values and the power spectra . Flow visualization of the vortices generated from the forebody , wing and LEX of the model has also been performed in a water tunnel . It was found that the entire system of the flow and the sting-supported model locks-in at the resonant oscillation frequency as the lateral oscillation occurs . The presence of LEX significantly enhances the oscillation amplitude especially at high enough angles of attack , i . e ., β£ ΟΎ 40 Π . The enhancement of the lateral oscillation , as suggested by the water tunnel visualization , seems closely related to the breakdown of the LEX vortices in general and the location of breakdown in particular . The power spectra of the test model with wind and LEX exhibit a transition from weakly nonlinear to broad band oscillations as β£ is increased from 45 Π to 60 Π . The appearance of a broad range of frequencies around or below the dominant frequency , that can be indicative of possible chaotic oscillation , corresponds to a sharp drop of the lateral oscillation amplitude . The ef fect of Reynolds number is notable only at β£ ΟΎ 50 Π . Variation of the sideslip angle between 0 and 10 Π appears to have no discernible ef fects on the amplitude of lateral oscillation for the test model with wing and LEX .