The Bell X-22A was a U.S. Navy-sponsored VTOL research aircraft with four tilting ducted propellers arranged in tandem pairs. The ducts rotated from vertical lift to forward flight, while variable-stability instrumentation let researchers study hover, transition and control of future V/STOL transports. Two aircraft were built, and the surviving research lineage remained useful long after the first prototype was lost.
Future launches and major activity directly linked to this vehicle family.