Sikorsky’s X2 advancing blade helicopter has sustained a cruise at 181 kts, and has done so at very low vibration levels, the show stopper for Sikorsky’s XH-59A ABC helo in the 1970s, are a good sign.
This is about 40 kts faster than most conventional helicopters, and faster than almost any other helicopter out there.
They hope to make it to 250 kts, and they have yet to install the center hub fairing, which should further reduce drag, and the transmission is really not optimized for the mission, which implies that with some minor changes, performance could be improved:
The prototype is designed with no clutch between the main rotors and propulsor, which requires the pilot to increase forward speed through the variable pitch control on the six-bladed rear propeller. Once in the 180kt realm, the X2’s computer will automatically slow the main rotors and increase collective pitch to prevent tip speeds from entering high-drag transonic region, with Bredenbeck correspondingly increasing propulsor pitch to increase the X2’s speed as the propulsor also slows.
One of the things that blows my mind here is this vehicle has tested so well, so far, without any wind tunnel testing:
Weiner credits configuration maturity to Sikorsky’s advanced analytical tools given that the company did not perform windtunnel tests of the design before flight-testing. He says windtunnel tests would likely precede the design for a production model, the first of which could be a systems development and demonstration vehicle for the US Army’s potential competition to replace the Bell OH-58D Kiowa Warrior later this decade.