Redesignation of three YHC-1A prototypes in Oct 1962 to YHC-46C, then later CH-46C. The Army transferred 58-5514 to NASA in 1962, who reserialled it NASA533 in ~1964, assigned it to the Wallops Island Flight Center, wfu ~1975, fate unknown. The Army assigned 58-5515 to the US Army Aviation Test Activity (USAATA), Edwards AFB in 1960, and loaned it to NASA who assigned it to their Dryden Flight Research Center at Edwards AFB, CA ~1962. It served as a tow aircraft for the PARASEV airfoil. It was returned to Vertol ~1964 and bailed to M.I.T. for R&D purposes. It is unclear whether it retained it US Army serial or wore the civil registration, N55927. Vertol delivered 58-5516 to the Army sometime in 1960. Its history is unknown. It was registered N5588K at some point. Along with its sister, 58-5515, it was sold to MC Allister Engineering Enterprises, Kent, WA, and they are both stored in a hangar at SEA-TAC airport, circa 1984. Current status unknown.