I remember seeing one of those technology documentories where they had a concept helo (around the same time as sikorsky's ABC & the Grumman? X29a) that was a 'X' wing, rigid blade helo that at a certain point the blades slowed & locked into position allowing the forward speed to increase beyond normal RBS speeds.
don't think it ever flew, but it did make it to the drawing boards.
but then - so did 'the homer'
