Study of Unconventional Propulsion System Concepts for use in a Long Range Transport - Exhibit A, Part II, Task I Final

摘要

An investigation of unconventional propulsion system concepts for the next generation of subsonic (0.9 Mn) long-range transport aircraft indicates that a noise level of FAR Part 36 minus 20 ePNdB can be achieved by either a fixed geometry, high bypass ratio turbo fan with a geared two-stage fan and advanced acoustic treatment;or a moderate bypass ratio turbofan with a variable pitch two-stage fan, variable primary and duct nozzles and ad¬vanced acoustic treatment. The geared fan system meets the noise goal with minimum ec¬onomic penalty. Comparison of the noise footprint areas at take-off and landing in com¬bination with the economic penalties required to achieve lower noise levels at specific noise measuring stations, indicate that both footprint area reduction and current certification pro¬cedures should be used to ascertain the point of diminishing returns in establishing future noise goals.