The NASA Quiet Engine Programme.

Discussion of the experimental Quiet Engine developed under the NASA program to reduce jet aircraft noise levels. The current status of the program is given as follows: Aerodynamic evaluation of the three fans is complete and their acoustic evaluation is partially complete. Tests of fan casing boundary-layer section and of serrated leading edges on the half-scale B fan are complete and are underway on the half-scale C fan. Tests of the first engine with the A fan began in August 1971.