Are those props or rotors? The Vought/Hiller/Ryan XC-142A VTOL 'tilt-wing' test vehicle NASA 522 / 62-5924 which used to be on display outside at the US Air Force Museum at Wright-Patterson AFB, photo taken 6th February 1987.
Dedicated to the memory of 340Sqn Cpt Anastasios Balatsoukas, lost his life in the cockpit of this aircraft, due to a mid air collision with F-16D 604 in 26/08/2010.
May God rest Tasos' soul in peace...