English: A Sikorsky YR-4B (c/n 29, USAAF s/n 43-28229) at the NACA Langley Memorial Aeronautical Laboratory at Hampton, Virginia (USA). This aircraft was initially ordered in 1943 by the USAAF, and still carries the original serial number. It had been transferred to the U.S. Navy and officially received the designation HNS-1 (BuNo 39034). It was test flown at Langley in March 1945. Jack Reeder, the NACA's first helicopter pilot, is at the controls. This "Hoverfly" was also used for pilot training in rotary winged flight.