Sikorsky and Boeing Unveil New Helicopter that Could Replace US Army Black Hawk The coaxial helicopter is based on the companies’ Defiant prototype. Lockheed Martin’s Sikorsky and Boeing have unveiled a new compound coaxial helicopter that they hope will one day replace the U.S. Army’s venerable Black Hawk helicopter. The companies billed their Defiant-X as the “fastest, most maneuverable and most survivable assault helicopter in history.” The design is based on the SB>1 tech demonstrator aircraft jointly built by the two companies in recent years. “We've made some enhancements to design to help reduce thermal signature and improve aerodynamic handling,” Heather McBryan, Boeing’s sales and marketing director for Future Vertical Lift, said in a call with reporters on Friday ahead of Monday’s announcement.