I don't have an aerospace degree, but I will nonetheless comment on a few of your comments: Engine cooling: diesel engines need substantially less cooling than

I don't have an aerospace degree, but I will nonetheless comment on a few of your comments: Engine cooling: diesel engines need substantially less cooling than petrol engines, hp-for-hp. Gearbox certification: you are generalizing from one example. Every turboprop has a gearbox. Most helicopters have a "complex" gearbox, coupling two (and sometimes three) engines. Long propeller shaft: Not really a hard problem. Helicopter tail shafts seem more difficult. Pusher efficiency: The propeller efficiency will be a bit lower for the reasons you mention, however the overall aerodynamic efficiency is likely to be higher. There are plenty of citations for this. Pusher noise: Again, you are generalizing from one example (Avanti, in which the source of the noise is largely the turbine exhaust interacting with the propeller blades). Forward visibility: I suspect they intend to use a camera. Other solutions are possible also. WW2 fighters had no forward visibility on landing. Landing gear and door, tail strikes: yes, probably "prototype" stage engineering Coffin corner: The potential problems are a consequence of specific airplane design. They are easy to avoid, though admittedly by sacrificing a smidgin of performance. High altitude flight: I can't see that thing getting to 65,000 feet with that propeller and those wings... the number was taken from the patent, it seems, and may not have real world significance with the current design. Overall, I think it is great to see a bit of innovation and experimentation happening in aviation again.