Helicopter Downwash Applied to Fog Clearing: A Status Summary

Abstract : The report summarizes the results of a literature search and a survey of helicopter pilots concerning the use of helicopter-induced downwash to effect temporary clearings in fog. While the technique has been unsuccessfully applied in a variety of situations, the available information indicates that the criteria for determining the probability of successful application of this method are yet to be completely established. In general larger helicopters, such as the CH-54, can be successfully used for clearing fogs of 500-600 foot depth; however, smaller helicopters, such as the UN-1, do not work well for fogs of depths over 100-300 feet.