OS 91 HZ Helicopter Engine

When it comes to designing engines expressly for the F3C competition, the OS pedigree goes back a long way. That experience and the never ending quest to produce the best engines in the world, has culminated in the new Max 91HZ Ring.

With improved hovering stability as well as greater power at high speed, the new Max 91HZ meets and exceeds the extreme demands of today's complex F3C competition manouevres.

The new design piston and crankshaft brings reduced vibration to provide improved and more stable torque over the entire RPM range.

The rectangular, heat-sink head is designed to be completely enclosed inside the helicopter fan shroud for better cooling in a fully enclosed body. The black 'alumite' finish with O.S. and 91HZ logos imparts a distinctive image for this latest engine in the OS competition helicopter lineup.

An integral back plate heatsink improves crankcase cooling as a result of that extra power. This, and a thermo insulator installed on the carburettor mounting spigot, helps shut out engine heat to the carburettor, which in turn ensures a stable fuel/air mixture.

A needle control lever with O.S. Engines logo is supplied with the engine as standard since it is widely used in the F3C competition when in flight adjustment is required

Specification

Displacement: 0.91 cu in (15 cc)
Bore: 1.091 in (27.7 mm)
Stroke: 0.976 in (24.8 mm)
Output: 3.4 ps @ 15,000 rpm
Practical rpm range: 2,000–16,000
Weight w/o muffler: 22.39 oz (635 g)

Includes: OS #8 glow plug