The following images were published in Anything A Horse Can Do: The Story of the Helicopter by Col. H. F. Gregory, Reynal & Hitchcock, N.Y., 1944. Col. Gregory was an instructor and Army test pilot in gyrocopters and early helicopters during the late 1930s and WWII. Early German and American rotorcraft may be a topic of a new article soon. Look here for more rotorcraft history. A Kellett YG-1 gyroplane in formation with a Seversky P-35. Both the YG-1 and Pitcairn's YG-2 were direct-control autogyros purchased and evaluated by the U. S. Army. Experience with these rotorcraft lead to the development of American helicopters for military use. Germany's Focke-Wulf 61 was one of the first successful helicopters. It used two rotors which rotated in opposite directions to offset rotor torque. For more information, try German Helicopters 1928-1945 by Heinz J. Nowarra, Schiffer Military History, 1990. In 1940, the Platt-LePage Aircraft Co. won an Army contract for a helicopter. Drawing on German experience, the XR-1 used twin rotors powered by a Pratt & Whitney R-985 engine of 450 h.p. Flight testing began in May of 1941. A number of changes were made before significant flights were regularly performed. With a modified nose section, the XR-1A made its first flights in late 1943. One other airframe was produced for testing of improvements of the controls but did not fly. The XR-1 is in storage at the NASM, while the XR-1A was sold to Frank Piasecki and accidentally scrapped. [Thanks to Jay Hendrickson for this correction and additional information.] Igor Sikorsky's VS-300 (right front) demonstrated that a single rotor helicopter with a small anti-torque rotor on the tail was practical, and the Army ordered a version called the XR-4 (rear left). The XR-4 first flew on 14 January, 1942 and went on to pass Army test to demonstrate the craft's controllability. Here, it has landed on a 20' x 20' platform. Service test models were known as YR-4s and the final production version was the R-4B, one of which is a part of the CAF's Ghost Squadron.