Aircraft with transonic rotor
A rotorcraft aircraft design incorporates double swept forward and aft rotor blades configured to provide efficient hover and efficient cruise at Mach number of 0.65-0.7 without varying a diameter of the rotor. The aircraft design combines the benefits of helicopters and fixed-wing aircraft, enabling vertical takeoff and landing (VTOL) capabilities while also achieving improved forward flight speed and reduced noise emissions.
1 . A method for operating a tilt rotor aircraft having first proprotor has a blade with an inboard portion and a swept outboard portion, in which:
the swept portion occupies at least 50% of a length of the blade; and
a leading edge of the blade is swept both forward and aft;
the blade is constructed of a medium-modulus carbon fiber whereby a distribution of fiber orientations changes from 0 degree fibers at a blade root and 45 degree fibers at an outboard station of the blade;
and operating the aircraft with a tip speed of the rotor between Mach 0.8-0.9 via a drive system with variable RPM coupled to the first proprotor.
2 . The method of claim 1 , wherein the aft swept portion is at least 30% of the length of the blade, and has an aft sweep of at least 30 degrees.
3 . The method of claim 2 , wherein the inboard portion has a thickness-to-chord ratio of less than 16%.
4 . The method of claim 1 , further comprising providing, by the first proprotor, at least 80% of a lift required for hover.
5 . The method of claim 1 , further comprising providing, by the first proprotor, at least 95% of a lift required for hover.
6 . The method of claim 1 , where each of the first proprotor is sized relative to a maximum rated capacity of the aircraft to have a disc loading of up to 40 psf.
7 . The method of claim 1 , where each of the first proprotor is sized relative to a maximum rated capacity of the aircraft to have a disc loading of 40-100 psf.
8 . The method of claim 1 , wherein each of the first and second proprotors is a hingeless rotor.
9 . The method of claim 1 , wherein the blade has a linear taper of 50% to 58% from 10% to 94% span.
10 . The method of claim 1 , wherein a chord of the blade further reduced by 49% to 55% from 94% span to a tip.
11 . The method of claim 1 , wherein an airfoil thickness ratio of the blade is reduced from 15%-chord at a root to 13%-chord at 60% span and 10%-chord at a tip.
12 . The method of claim 1 , wherein the blade has a total twist of −32 degrees from root to tip.
13 . The method of claim 1 , further comprising rotating, by a drive system, each of the first and second proprotors at a rotation speed (RPM) in forward flight less than 70% of a maximum RPM in hover flight.