O.S. Engine OSMG1975 91HZ F3C Competition Engine  [OSMG1975]

Designed for Contest Flight: O.S. Engine 91HZ

The O.S. Engine 91HZ is a competition-oriented helicopter motor refined from the 91SZ-H, created to meet the careful demands of F3C flying. It focuses on heat control and repeatable tuning to help pilots perform complex manoeuvres reliably.

Compact Head and Effective Cooling

The engine uses a narrow heat sink head to fit within common shroud designs while still providing effective heat dispersion. Dual sinks on the head and crankcase combine to stabilise operating temperatures during extended or intensive flights.

Reliable Carb Design and In-Flight Control

With the 61B carburetor fitted, the 91HZ emphasises tuning stability. The insulating ring helps shield the carb from crankcase heat and multiple O-ring seals reduce air leakage. The in-flight needle valve arm permits on-the-fly mixture trimming for fine control.

For pilots who need dependable thermal performance and straightforward in-flight adjustment, the 91HZ provides a compact, tunable package suitable for high level contest flying.