Model Test Results of the Split-Fan Cross-Ducted Propulsion System Concept for Medium Speed V/STOL Aircraft

Propulsion systems for Navy V/STOL aircraft have unique design requirements from which has emerged a diversity of proposed configurations. During recent years the Lockheed-California Company has been involved in design studies of a split-fan, cross-ducted propulsion system concept that meets the V/STOL requirements with conventional turbofan engine configurations. This concept utilizes fixed engines/nacelles with thrust vectoring for lift, and transfer of engine fan air between variable area nacelle nozzles for aircraft control and trim. A simple, lightweight cross-duct coupling between engines also provides engine-out roll trim, and is adaptable to either a twin or four engine configuration.

A joint Lockheed/Navy experimental test program was conducted, utilizing a 0.25 scale propulsion internal flow model, to establish the flow transfer performance and the capability to generate nozzle forces for aircraft thrust, lift, and control. A description of the model, test set-up, and preliminary performance results that demonstrate concept feasibility are presented herein.