My wife and I are living in Germany . However my parents are not here with me . They are in my home country <| sep |> The scaled down electric motors we ' ve been using n power tools and other cordless devices don ' t count ? <| sep |> She scowls . As if . <| sep |> I ' ll take the wailmer add me ! <| sep |> I had to do some googling before I could agree with you , as typically I have found that multiblade helicopters have higher RRPM values 407 vs 206 L , Bell 206 vs EC 20 , etc , so I was surprised to read that the RRPM of the UH 60 was lower , but it makes sense considering the larger diameter of the ' Hawk blades vs the Huey . Interestingly , the chord of the blades look to be about the same , unless the M ' s have a longer chord since they apparently lift about 500 lbs more than the previous L ' s ? UH 60 Main Rotor Diameter 53 ' 8 UH 60 M Main Rotor Blade Chord 20 . 87 or larger ? widechord blades on the ML UH 60 Main Rotor Tip Speed at 258 RPM 725 fps 494 mph UH 1 D Main Rotor Diameter 48 ' UH 1 D Main Rotor Blade Chord 21 1 hhuey UH 1 D Main Rotor Tip Speed at 324 RPM 814 fps 555 mph 310631 , rxryAgAAQBAJlpgPA 244 otspG 5 jkwkXkdquh 1 d % 20 main % 20 rotor % 20 tip % 20 speed % 20 fpspgPA 244 # vonepagequh 1 d % 20 main % 20 rotor % 20 tip % 20 speed % 20 fpsffalse Speed of Sound at Sea Level ISA is 761 mph and decreases with altitude . planes . comjetmach 1 . htm