Can the STOL modifications made to an airplane's wings, vortex generators, etc, be made to a helicopter's rotor blades, and if not why?
While in the military someone explained a helicopter's rotors are basically like wings, ie same aerodynamic principles. If possible, integrating STOL modifications would increase the efficiency of the blade.
- John RLv 75 years agoFavorite Answer
There would be no point in this, and they would actually detract from performance.
STOL modifications do not increase total lift, they simply allow the wing to generate lift at a lower speed, often by allowing it to operate at higher angles of attack without stalling.
But there is no such thing as a free lunch in aerodynamics - while a higher AOA allow you to create the needed lift at a lower speed, a higher AOA also means greater induced drag, wasting the power you would use to climb.
- lowlevelLv 75 years ago
No, you can't. Rotor blades are made with symmetrical airfoils to prevent the center of pressure from moving with changes in angle of attack. Since helicopters can already hover... and since a certain blade RPM is required to maintain rigidity of the rotor... ...and since a lower blade RPM would mean a lower airspeed for retreating blade stall... there is no advantage of making a rotor 'STOL'.
Some of the rotors for the human powered helicopters have STOL characteristics like very high camber... but these are very lightly loaded (so VGs wouldn't be of any use) and are quite impractical for any meaningful directional flight.
- flyingtiggerukLv 75 years ago
a helicopter can VTOL so STOL modifications are a moot point.
Improvements to helicopter rotors have included paddle tips or swept tips, the blades themselves are probably too narrow for modifications like vg's to have any meaningful effect.
People have investigated blowing from helicopter blade leading edges as a means of improving performance, eg link.