Patent ID: 7231997

Claim:
A lift platform comprising: a primary drive system, comprising: an engine; a transmission coupled to said engine; a first fixed-pitch propeller coupled to said transmission; a first over-running clutch interposed between said transmission and said first fixed-pitch propeller; a second fixed-pitch propeller coupled to said transmission; and a second over-running clutch interposed between said transmission and said second fixed-pitch propeller; and an auxiliary drive system, comprising: an air compressor coupled to said engine; an air storage tank coupled to said air compressor; a thrust recovery system coupled to said air storage tank, said thrust recovery system further comprising a first plurality of tip jets positioned at a first plurality of propeller tips corresponding to said first fixed-pitch propeller and a second plurality of tip jets positioned at a second plurality of propeller tips corresponding to said second fixed-pitch propeller; and at least one valve for controlling air flow from said air storage tank to said thrust recovery system.