This report contains the results of a field teat program to measure the movement and strengths of wing trailing vortices of the Douglas DC-6 jet transport aircraft during takeoff and landing approach. The effect of the ground plane and ambient winds on the movement and strength decay was investigated. The results are compared with a modified potential flow theory.nThe position of the trailing vortices near the ground is extremely sensitive to low level ambient winds and vertical gradients of the wind. The measured positions of the trailing vortices indicate probable correlation with the potential flow theory with noted exceptions to the assumptions used. Measured vortex velocity decay rates are comparable to a modified theoretical free vortex viscous decay. Distinct vortex velocity fields were observed near the ground, using a smoke generator technique, for periods up to 65 seconds after aircraft passage. No differences in the trailing vortex system of two rolled-up vortices were observed for both the takeoff and landing configurations of the DC-6 aircraft.
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