The Consolidated YP-28 was to have been a version of the Consolidated
Y1P-25 with a Pratt & Whitney R-1340-19 air-cooled radial engine in
place of the Curtiss Conqueror liquid-cooled inline engine. It was
never built.
Sources:
The American Fighter, Enzo Angellucci and Peter Bowers, Orion Books, 1987.