Aeronautics and astronautics – Miscellaneous
Patent
1997-08-27
1999-10-05
Barefoot, Galen L.
Aeronautics and astronautics
Miscellaneous
244 53B, 244 65, 415119, B64D 3302
Patent
active
059610670
ABSTRACT:
An apparatus and method for reducing noise within the fuselage of a propeller driven aircraft. In one embodiment the propeller blades are spaced apart and in front of an offset inlet. The inlet provides air to a gas turbine engine powering the propeller, and also to a scavenge duct. The propeller blades and inlet are spaced apart such that during cruise conditions for the aircraft, the trailing edge of the propeller blades are spaced apart from the inlet by more than one-fourth of the chord length of the propeller blades, and less than about the chord length of the propeller blades. This spacing reduces the aerodynamic interaction between the propeller blades and a bubble of partially stagnated air in front of the inlet. In another embodiment, the scavenge duct is constructed such that it flows an increased amount of air, thus allowing the inlet duct to flow an increased amount of air. In this second embodiment, the engine duct flows more than about 40% of the total amount of air entering the inlet duct, and less than about 60% of that total airflow. In this manner the size of the slightly stagnated bubble in front of the inlet duct is reduced.
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An Assessment of Propeller Aircraft Noise Reduction Technology, NASA Contractor Report 198237, F. Bruce Metzger, Aug. 1995.
Hall Edward J.
Meade Joseph P.
Allison Engine Company
Barefoot Galen L.
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