advanced single-stage, high-temperature turbine. The primary burner and the duct burner utilize low-emission, highefficiency combustor concepts. The nozzle is a two-stream, concentric, annular (coannular) design with variable throat areas in both streams and an ejector/reverser exhaust system. The independent temperature and velocity control for both primary and bypass streams provides an inherent reduction in jet noise during takeoff. This noise reduction characteristic is based on an inverse velocity profile, where the bypass stream jet velocity is 50-70% higher than the primary stream velocity. Results from a P&WA model nozzle test program6 sponsored by NASA indicate that noise levels measured for coannular nozzles with this inverted velocity profile are approximately 8 EPNdB (effective perceived noise level in decibels) lower than a single-stream nozzle operating at the same airflow and thrust levels. These results are based on both static tests and wind-tunnel tests simulating takeoff flight conditions. Based on these model tests, the coannular noise benefit represents a breakthrough in jet noise control. Further evaluation (a largescale demonstration of this noise benefit) is in the planning stage. Critical Operating Conditions