STOL noise sources and fan noise treatment

STOL noise goals, noise sources, and their affects on engine and propulsion systems design are considered. It is shown that major noise sources constitute the blown-flap system with its turbofan engine and the augmentor wing propulsion system. Most of the problem areas associated with STOL propulsion systems are defined and the development of a multistage fan engine with proper rotor-stator spacings and low noise core exhaust jet is illustrated. A variable-area acoustic inlet provides near sonic flow conditions during takeoff and landing.