MILLER helicopter (J. Miller, 62 Abbott Rd., Putney, London, SW)

   This device, built in 1909, consisted of twin screws of spiral design spinning in opposite directions on a vertical shaft, driven by a 50hp motor. A narrow vertical surface extended for the full height outside of the rotating screws to provide directional control.

   Data
   Two coaxial rotor screws 10ft diameter
   Area 909 sq ft
   Weight 1,1901b