Aerodynamic instability of non-lifting bodies towed beneath an aircraft

A theoretical and experimental (wind tunnel) investigation was made of the stability of a heavy body towed on a light cable beneath an aircraft. The theory showed the possible existence of a band of speeds within which the body is dynamically unstable, (swinging sideways). The experiments confirmed this prediction, and showed good agreement with the calculated values of the two critical speeds wh.ich bound the unstable region. The calculated and measured periods of oscillation also were in good agreement.