Effects of Airframe Geometry on Downwash Problems of Tandem Ducted-Propeller VTOL Aircraft

摘要

A full scale half-model simulation of a dual tandem ducted propeller VTOL aircraft has been tested at heights of less than two duct diameters above sand and water terrain. Data on terrain transport, terrain caused aircraft damage, flow field measurements and ducted propeller performance were obtained. These tests were conducted at propeller disc loadings up to 60 pounds per square foot with various aircraft configurations and ducted propeller orientations. The dual tandem configuration was found to cause a significant increase in downwash problems compared to isolated propeller configurations previously tested. Reduced performance, severe engine and propeller damage and an oscillating aerodynamic interference were experienced. Several promising devices to alleviate downwash problems were evaluated. (Author)