"It seems that every spec I read indicates that main rotors nearly all operate in the 400 to 450 RPM"
They differ quite a bit, actually. The local Guard base operates Chinooks, which I can hear coming well before seeing them. I can follow the blades going roundy-round, because they're relatively slow, being a large disk. The R22 disk turns at 530 RPM (104%), which gives 672 FPS tip-speed, or about 398 knots. That's right in line with ramen's comment "blade tips hover at 675 to 725 feet per second." and 2 Beers "the tip speed is usually somewhere around 400-430KTS".
What I don't understand is how some ships can have such high max airspeeds without getting RBS. Are their rotors turning so fast that the tips are barely subsonic, or what?
rf