Abstract: A thrust reverser including a bypass duct and a plurality of light weight, circumferentially displaced blocker doors each movable between a normal position and a thrust reversal position. The blocker doors include pits on the inner portion which faces the bypass duct during normal operation of the engine. Provision is made for automatically covering the pits during normal operation to provide smooth, non-turbulent flow of air through the bypass duct. In one embodiment of this invention a pit cover is pivotally mounted on the blocker door and is biased to engage the edge of a ramp fairing when the blocker door is in the position it occupies during normal operation of the engine. During thrust reversal, the pit cover moves outwardly along with the blocker door and away from the ramp fairing so as not to impede in any way flow of thrust reversal air through an opening in the outer wall.

Abstract: A thrust reverser including a bypass duct and a plurality of light weight, circumferentially displaced blocker doors each movable between a normal position and a thrust reversal portion. The blocker doors include pits on the inner portion which faces the bypass duct during normal operation of the engine. Provision is made for automatically covering the pits during normal operation to provide smooth, non-turbulent flow of air through the bypass duct. In one embodiment of this invention a pit cover is pivotally mounted on the blocker door and is biased to engage the edge of a ramp fairing when the blocker door is in the position it occupies during normal operation of the engine. During thrust reversal, the pit cover moves outwardly along with the blocker door and away from the ramp fairing so as not to impede in any way flow of thrust reversal air through an opening in the outer wall.

Abstract: A method and apparatus for suppressing internally generated gas turbine engine low frequency noise is disclosed. The apparatus is comprised of means for structuring the cross-sectional area of the gas flow path into one or more open elements of a predetermined size. The method involves a way of determining the size of each of the elements and the total number of elements.

Abstract: A turbomachinery stage comprising two axially spaced blade rows, one of which is rotatable, wherein the blades of the upstream row are contoured to present a leaned wake to the downstream row. In the preferred embodiment, the blades of the upstream row extend radially from a central hub and, at a radius above the hub, are physically curved circumferentially from a radial line through the hub. The physical lean locally complements the inherent aerodynamic lean at each radius such that the integrated acoustic power of the stage is essentially at a minimum, thus maximizing the acoustic attenuation. Preferably, the constraint is imposed that the blade physical curvature is essentially smooth, continuous and without an inflection point.