WEST PALM BEACH, Florida -- In a demonstration Thursday for the U.S. Army's top civilian official, a Sikorsky-Boeing team flew experimental helicopter prototypes that could one day become the service's next scout and assault rotorcraft under the Future Vertical Lift (FVL) program. The SB-1 Defiant helicopter prototype performed a series of aerial maneuvers to show off its unique X2 technology, which features a coaxial rotor blade system and a large propeller in the tail section of the aircraft designed to aid in forward thrust. This was the first flight demonstration of the Defiant for Army Secretary Ryan McCarthy. Sen. Tammy...