1949 Seibel S-4 helicopter.
Fullsize image: https://s3-us-west-1.amazonaws.com/h...r_fullsize.jpg
Previously:
Hughes XV-9 research helicopter - photo
Mil V-12 transport helicopter - photo
Vertol VZ-2 V/STOL research aircraft - photo
Platt-LePage XR-1A helicopter - photo and video
Flying jeep Curtiss-Wright VTOL quadrotor helicopter - photo
Bell HSL-1 helicopter - photo
Hughes HX-17 heavy-lift helicopter - photos
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