The O.S. FS-120 Surpass SP (often abbreviated as FS-120 SP) is a highly sought-after, vintage nitro-powered model airplane engine famous for featuring a functional, belt-driven Roots-style supercharger. It was developed by O.S. Engines to deliver immense power (around 2.5 BHP at 10,000 RPM) while turning large, high-pitch competition props.
Configuration: 4-stroke glow engine with an integral Roots-type mechanical supercharger mounted to the crankcase.
Power Output: Rated at roughly 2.5 BHP @ 10,000 RPM.
Propeller Range: Designed specifically to turn aggressive, high-load competition propellers (such as 14×14 or 16×6).
Fuel Requirements: Requires methanol-based fuel with a minimum of 18% lubricant (usually a castor oil/synthetic blend) to handle the extreme operating conditions.
Sound: The supercharger creates a distinct, loud induction noise.
This engine has been out of production for decades and is largely considered a collector’s piece today.
