Complex sentence: As with the Heinkel He 277 competitor for the "Amerika Bomber" contract, no prototype of the Ta 400 was ever built, it never progressed beyond a wind tunnel model, and performance, range and dimensions are based solely on the designers' estimates.
Split into simpler sentences: As with the Heinkel He 277 competitor for the "Amerika Bomber" contract, no prototype of the Ta 400 was ever built. It never progressed beyond a wind tunnel model, and performance, range and dimensions here are based solely on the designers' estimates.