The Vision and Strategy of our Technology
Each type of Vertical/Short Take-off and Landing (V/STOL) aircrafts has its own disk loading range and its associated hover lift efficiency, with the hover lift efficiency being inversely proportional to the disk loading, and with helicopters providing the highest hover lift efficiency, which ranges between 5-10 pounds per horsepower.
However, the helicopters’ relatively high hover lift efficiency comes on expense of its disk loading which is the lowest, and which ranges between 3-15 pounds per square foot. This necessitates the use of rotors having relatively big diameters, typically ranging between 24 – 79 feet in diameter, to propel helicopters.
And as these relatively big diameter helicopter rotors need to be positioned on top of the helicopters, so this limits the alternatives in which a helicopter powertrain maybe designed, resulting in a complex powertrain that is more susceptible to accidents due to component failure, limits the maximum speed at which a helicopter can fly, and makes helicopters noisy in operation.
The limited maximum speed at which a Helicopter can fly is due to the fact that a helicopter has rotating wings, with the helicopter’s spinning rotor blades producing lift and enabling the helicopter to fly, and these only produce an equal amount of lift in a still air hover. When there is any wind at all, or the helicopter moves forward, the advancing blade (the forward moving one) has more air blowing over it i.e. a higher airspeed than the retreating blade (the backward moving one), and therefore produces more lift.
To counteract this dissymmetry of lift, we allow the blades to flap up and down, and this flapping equalizes the lift across the rotor disc as the blades “flap to equality.” However, a side effect of this flapping is that when the cyclic is moved forward to increase speed, the rotor disc tilts forward initially, but then flaps back, and further forward cyclic movement is required in order to continue to accelerate. This phenomenon, known as “flap back,” occurs throughout the whole speed range of the helicopter. So, if we want to increase our speed, the cyclic has to be moved progressively further and further forward. There will come a point at which the cyclic is on its forward limit, and the helicopter cannot fly any more quickly, which limits the maximum speed at which a helicopter can fly.
An ideal V/STOL aircraft’s propeller would be a Compact Propeller providing relatively high hover lift efficiency, preferably more than 15 pounds per horsepower, and high disk loading, preferably more than 200 pounds per foot square, to enable reducing the diameter of the propeller’s rotor, which will provide more flexibility in the V/STOL aircraft design.
Based on our provisional calculations, our proposed technology will enable the production of lift-producing Compact Propellers providing a high hover lift efficiency of up to 20 pounds per horsepower, and high disk loading of up to 250 pounds per foot square, which will make this innovative propeller ideal for powering all future Helicopter-like VTOL aircrafts, and which will enable the production of quieter Helicopter-like VTOL aircrafts that are cheaper to produce and maintain, safer to operate, and that can fly at higher speeds and altitudes.