Acoustic Results Obtained with an Upper-Surface-Blowing Lift-Augmentation System

The noise caused by the interaction of the exhaust jet and the wing was measured under static conditions for several versions of a small-scale STOL engine-over-the-wing configuration. Three basic nozzles were tested: a circular nozzle with deflector, a 5:1 slot nozzle with and without deflector, and a 10:1 slot nozzle. The wing included a flap lift-augmentation system with flap deflection angles of 20° for a takeoff condition and 60° for an approach condition. Far-field noise data are presented for nominal jet pressure ratios of 1.25 to 1.7 for the flyover mode. The data are discussed in terms of SPLs and normalized sound pressure spectra: comparisons with nozzle-only data are also made. The model OASPL near 90°—measured from an engine inlet—follow a 6th–7th power relationship with jet velocity compared to an 8th–9th power law for the jet alone. Only minor acoustic differences were obtained between the two flap deflection positions. The most significant noise reduction was achieved with the 10:1 slot nozzle. Implications of extending the small-scale model acoustic data to a full-scale aircraft are discussed and indicate a sizable noise attenuation may be achieved owing to wing shielding.