A NASA sponsored program to develop noise-reduction modifications for the JT3D and JT8D engines was initiated in August 1972. New higher flow single-stage fans are attractive and result in higher bypass ratios with improved thrust and fuel consumption and reduced jet velocities. Fly-over noise reductions as great as 20 EPNdB are shown for the modified engines with nacelle treatment. Engine certification can be completed and production hardware for fleet retrofit or new airplanes can be provided by late 1975.
