Sikorsky And Boeing Unveil The Defiant X That Will Compete For The Future Long-Range Assault Aircraft Sikorsky And Boeing Unveil The Defiant X That Will Compete For The Future Long-Range Assault Aircraft Sikorsky and Boeing released details of the DEFIANT X helicopter designed for the U.S. Army. With its rigid coaxial rotor system and pusher propeller, DEFIANT X will provide the U.S. Army with increased speed, maneuverability and survivability. (Image courtesy Sikorsky and Boeing) The advanced compound helicopter has been developed on the experience of the SB>1 Defiant and will face Bell’s proposal based on the V-280 Valor.