30th
“In June 1982, Columbia Helicopters was hired by Sohio to participate in a test on Alaska’s North Slope. The purpose of this test was to evaluate the ability of a helicopter—the Boeing Vertol 107-II - to tow a fully-loaded hover barge over water, snow and ice.”
1. That helicopter is not in the process of crashing. 2. Hover barge!
From Mark.
From the Jan. 1918 Monthly Weather Review:
1. Introduction.—The development of the art of concealing large guns so that they can not be easily seen by hostile airmen or observers in kite balloons has brought into prominence the study of methods of locating powerful guns by means of observations of the time of arrival of the sound of their gunfire at one or more observing stations.