Heavy Lift Heritage
The 50s and early 60s saw Igor and his cohorts doing quite a bit of shopping in their existing parts bins to create new aircraft. The evolution of Sikorsky heavy lift rotors from the S-56 (CH-37) to the S-64F (CH-54B) and beyond is a great example.
The entire S-56 dynamic system, including the 72’ diameter main rotor system, was transplanted into the S-60.
The S-56 main rotor was then used in the S-64E (CH-54A), with the exception that an additional blade was grafted onto the hub for a total of 6. The vertical and horizontal hinges, spindles, sleeves, horns, and other miscellaneous hardware was retained, as well as the unique K-bar for the pushrod. Of course the swashplates were new to accommodate another blade..
The S-64F (CH-54B) retained the 72’ rotor diameter, but used a 6 arm S-65 (H-53) non fold style rotorhead. The blade is indeed related to the S-65 blade, but is nicknamed “high twist” because it was aerodynamically optimized for hover compared to the standard S-65 blade.
All of the previous blades had aluminum spars. Going forward, the titanium spar Improved Rotor Blade (IRB) originally intended for the CH-53D (at a 72’ diameter) was actually first applied to the 79’ diameter CH-53E, again with another arm added to an all new , bigger diameter rotorhead, for a total of 7 blades. And of course the CH-53K is all new, but it retains the 79’ rotor diameter…. so in a way, it can be said to be a descendant of the S-56!