I have a new VTOL aircraft concept that offers vertical takeoff with a similar rotor disc loading to helicopters but a high speed cruise to about 400 MPH, if enough power is installed to reach that speed. Please see Welcome to Tiltplane.com | New VTOL Concept.
In the hover mode the speed of the rotors relative to the air will be a lot higher than the takeoff speed of most fixed-wing aircraft, so the area of the rotor blades can easily be a lot less than the area of the wings and control surfaces of fixed-wing airplanes, which means, in turn, that the cruise efficiency should be very good. In one design I was looking at I was getting an L/D ratio of 19:1 at about 200 MPH. The L/D ratio for helicopters is much lower, ranging from 7:1 to 9:1 and high top speeds are very difficult to achieve.
There are a couple of important issues about the tiltplane approach:
(1) The axis of the craft tilts from vertical when the craft is hovering to horizontal when the craft is flying. If it carries people, they would probably be carried in a compartment which somehow remains upright - which will require significant structure to implement.
(2) The craft has two powered, counter-rotating rotors turning about the axis of the craft with one rotor located at about 1/4 of the length of the fuselage from the nose and the other at about 3/4s of the length of the fuselage from the nose. It is mechanically awkward that two powered rotors are needed and that they are separated by so large a distance.
But there should be many unmanned applications for tiltplanes where (1) and (2) above are not significant obstacles and where the high cruise efficiency and high top speed are very valuable.
Questions or comments?