Sikorsky S-67 Blackhawk
 The Sikorsky S-67 Blackhawk was a private-venture prototype attack helicopter built in 1970 with Sikorsky Aircraft R&D funds. A tandem two-seat aircraft designed around the dynamic drive and rotor systems of the Sikorsky S-61 it was designed to serve as an attack helicopter or to transport up to 8 troops into combat.