Convair Model 21

The Convair Model 21 was a design proposal from Convair for a carrier-based anti-submarine aircraft for the United States Navy. It was drawn up for the VSX competition (Heavier-than-air, Anti-submarine, Experimental), which was opened in 1967 to find a replacement for the ageing twin piston-engined Grumman S-2 Tracker. Convair competed against Grumman's G-304, Lockheed's CL-806 and CL-995, McDonnell Douglas's Model 201 and an entry from North American Rockwell. Lockheed's design won and became the S-3 Viking, so the Model 21 never went beyond the concept stage. Convair did build wind tunnel models, a complete aircraft mockup, a forward fuselage mockup for the crew compartments, a part fuselage mockup for avionics and systems, and a weapons bay mockup with an engine in place to prove the loading and unloading of the torpedo bay. The German article says the layout was very close to the S-3 as built, differing mainly in outward-curved cockpit windows and slightly higher tailplanes. Convair also planned a transport version with a rear loading ramp and an airborne early warning version to rival the E-2 Hawkeye, with a rotating radar above the fuselage and twin fins on the tailplane ends instead of a central fin.