Sikorsky XR-4
Sikorsky R-4 Hoverfly was the first series produced US helicopter. It was result of contract with US Army and XR-4...
X-4
Ruhrstahl X-4
Ruhrstahl X-4, also known as "Kramer X-4" or "Ruhrstahl-Kramer RK 344" — the rocket of a class air-air, designed during...
