Abstract: Cascades and associated blocker doors are provided in the lower section of a turbofan engine nacelle such that when the blocker doors are closed the bypass flow is diverted through the open cascades to produce vertical thrust. Vanes are provided in the cascades to assist in directing the diverted airflow in the downward direction. The upper section of the bypass duct is isolated from the lower cascade section by way of horizontal struts extending across the bypass duct. A pair of outer doors may be provided over the cascades such that, when opened, they act to provide side skirts to guide the downward flow of air.