From: bretcahill@aol.com   
      
   > > Put the fuselage inside of 2 counter rotating fans and the core engines in   
   tandem inside of the fuselage, geared together in case one engine fails like   
   the Osprey.  The engine room would split the cabin area in two displacing a   
   few dozen seats so the    
   wide body version would have a for cabin and an aft cabin, bathrooms and crews   
   etc.   
   >    
   > So a helicopter then.   
      
   Fixed wings don't provide the lift for a helicopter in any stage of flight.   
      
   Like the Osprey the fixed wings provide lift in horizontal flight, but   
   obviously not in VTOL mode.   
      
   Unlike the Osprey the fans/props do not change orientation relative to the   
   fuselage after takeoff.  Instead the entire fuselage rotates to the horizontal   
   for horizontal flight.   
      
   The passengers and pilot are tits up on take off and landing.   
      
   Another advantage:   
      
   The wings are not designed around the inelegant discontinuity of the engine   
   weight.   
      
    > These don't have the greatest safety record in   
   > general.   
      
   > > 4.  Increased Safety.  If a fan blade snaps off it can't impale any   
   passengers or critical structures.   
   >    
   > Shedding a fan blade leads to rapid destruction of turbines caused by   
   > loss of balance anyway.   
      
   Much much less of an issue with larger ductless fans.   
      
   1.  Imbalance forces increase with the square of rpm times dia.  A 3X larger   
   dia. fan has one third the imbalance for the same tip speed and same mass   
   loss. (1/3)^2 X 3 = 1/3.   
      
   2.  The tip speed will be less.  The whole point of high by pass is high mass   
   flow rate but at lower speed for higher propulsion efficiency at take off.    
   Take off is where they are wasting all the fuel.   
      
   3.  3X more blades can be packed on a larger annular fan.  If one comes off it   
   creates 1/3rd the imbalance as a similar fan with 1/3rd the number of blades.   
      
   4.  Without ducting, no impacts on other blades.  the lost blade easily clears   
   the swept wing which isn't going as fast forward as the blade is traveling   
   away from the plane.   
      
   https://www.youtube.com/watch?v=o2JKBabvx44&t=2s      
      
   § 33.94. Based on a margin of safety (MS) analysis, the most critical   
   compressor, turbine or fan blade at its maximum permissible rotating speed   
   must be contained by the casings while the engine should operate continuously   
   for at least 15 s.    
      
   https://www.sciencedirect.com/science/article/pii/S100093611200009X   
      
      
   Bret Cahill   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)