Why all this complexity to produce a new version of an engine, the turboprop, whose primary advantage was simplicity? The main problem with conventional jet engines is that the combustion takes place in an open chamber, which is considerably less efficient than the closed chamber of a piston engine, where it has constant volume (or close to it). The Otto cycle or Diesel cycle used in piston engines has a much lower specific fuel consumption than the Brayton cycle of a traditional gas turbine engines at low speed. Lutz's design was intended to power very long-range bombers and patrol aircraft, where fuel economy was more important than simplicity and performance.
