Vibration and icing investigation of CAA type V-109 very-high-frequency aircraft antenna

Vibration and icing determinations on a CAA type V-109 very-high-frequency aircraft antenna were conducted in the NACA Lewis icing research tunnel. The antenna is an omnidirectional-range unit that consists of two aluminum elements mounted in a streamline plastic head forming a V in plan view with an apex angle of 80°.

Vibration determinations during a nonicing experiment produced element-tip total amplitude of approximately 1/4 inch at a tunnel-air velocity of 300 miles per hour.

During the icing investigation, a total amplitude as great as 7 inches was observed at the antenna-element tips with tunnel-air velocities greater than 160 miles per hour and a tunnel-air temperature of 20° F. At the higher tunnel-air temperatures, which produced a heavier and more severe ice accretion, the damping effect of the ice reduced the element-tip amplitudes over the entire range of tunnel-air velocities to a maximum of 1/4 inch at a tunnel-air velocity of 300 miles per hour.