AN INVESTIGATION OF VTOL OPERATIONAL PROBLEMS DUE TO DOWNWASH EFFECTS

Operational problems of propeller type VTOL aircraft caused by downwash effects have been investigated utilizing a 3500 horsepower engine and a 15 foot diameter propeller mounted on a 20 ton crane. Propeller disc loadings up to 60 pounds per square foot were tested over several types of terrain and for various propeller heights and orientations above the terrain. An evaluation of the effects of downwash on pilot vision, ground personnel environment, equipment and aircraft damage and on aircraft concealment are presented.