Originally Posted by
noneofyourbusiness
Sikorsky X2 - T800 engine, free power turbine
Sikorsky Raider - T700 engine, direct drive from engine to rotor
Sikorsky/Boeing Defiant - T55 engine, free power turbine
Sikorsky Raider X - new GE single spool engine, direct drive
Conclusion - Sikorsky Raider and Raider X will never fly fast, because they lose the slowed rotor technology with a single spool engine. X2 and SB-1 have free power turbines, so the drive to the rotor is decoupled from the engine central shaft.
Single spool engines refers to the gas producer section of the engine, and does not effect the power turbine section. Still a free turbine engine....
https://www.geaviation.com/sites/def...dual-spool.pdf