An air-based thrust recovery system for use in a powered lift platform
utilizing fixed-pitch propellers is provided. The system utilizes an air
compressor coupled to the drive motor of the platform and an on-board,
high pressure tank for air storage. The fixed-pitch propellers are
coupled to the primary drive system with over-running clutches, thus
allowing the thrust recovery system to rotate the propellers faster than
if driven solely by the primary drive system. Preferably the propellers
are surrounded by air ducts. The thrust recovery system uses
individually, or in combination, cold air jets mounted at the tips of the
propellers, a circulation control system which blows out the leading or
trailing edge of the propellers, and one or more perforated tubing
segments surrounding at least a portion of the platform's air ducts.