330-PSA-58-63 (USN 711258):  First SX-51A Flight Photo.  This photograph shows the Lockheed-California Company’s XH-51A, rigid-rotor helicopter in flight, November 1, 1962.  It is one of two advanced concept helicopter research vehicles built under a joint U.S. Navy-Army contract, the XH-51A incorporates Lockheed’s breakthrough technology that uses the inherently stable effects of the rigid rotor to simplify control.  Designed for speeds in excess of 150 mph, the XH-51A features “hands-off” flying capability with no form of autopilot or artificial stabilization. The XH-51A is equipped with a retractable landing gear, eliminated the drag inherent in conventional landing gear.  The skids, shown in this photo, are free-falling and can operate without hydraulic power.  Another XH-51A innovation:  all-stainless steel rotor blades.  Stable and controllable with power on or off, the XH-51A design emphasizes safety, economy, and ease of handling.  Unique performance characteristics of the rigid-rotor helicopter afford potential application to a variety of military missions.  Lockheed’s flight prove-out program for its rigid-rotor helicopter concept began in 1959 with a developmental flying test bed machine that logged hundreds of successful flights Photograph released March 13, 1963.  (2015/10/13).
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