Unleashing the Power of the Rotax 912 ULS Engine

Written By Kevin Baker  |  Engine

rotax 912 uls

When it comes to light sport and ultralight aircraft, the Rotax 912 ULS engine stands out as a leader in its class. With its impressive power-to-weight ratio and high fuel efficiency, it’s no wonder this engine is a top choice among aviation enthusiasts worldwide.

The Powerhouse: Rotax 912 ULS Engine

The Rotax 912 ULS is a four-cylinder, four-stroke aircraft engine with a reduction gearbox. It features liquid-cooled cylinder heads and air-cooled cylinders. Initially equipped with carburetors, later versions of this engine are fuel-injected, offering more power while maintaining the same weight.

Performance and Specifications

The 912 ULS engine offers a performance of 73.5 kW at 5800 rpm, with an engine torque of 128 Nm at the same rpm. It weighs in at 56.6 kg, making it a lightweight powerhouse. The engine’s fuel efficiency and lighter weight compared to comparable older engines make it a preferred choice for many aircraft like Evektor Harmony or Ellipse Spirit.

Design and Development

The Rotax 912 ULS was first sold in 1989 for use in ultralights and motorgliders. It has a capacity of 1,211 cc and a compression ratio of 9.1:1. The engine’s design includes air-cooled cylinders with liquid-cooled heads and a 2.43:1 PSRU reduction gearbox to reduce the engine’s relatively high 5,800 rpm shaft speed to a more conventional 2,400 rpm for the propeller.

Frequently Asked Questions

What is the time between overhauls for the Rotax 912 ULS engine?

The Rotax 912 ULS engine offers a time between overhauls of 2,000 hours.

Can the Rotax 912 ULS engine run on automotive fuel?

Yes, the 912 ULS engine is certified to run on automotive fuel (mogas), further reducing running costs, especially in areas where leaded avgas is not readily available.

What is the power output of the Rotax 912 ULS engine?

The Rotax 912 ULS engine delivers a power output of 100 HP or 73.5 kW at 5800 rpm.


The Rotax 912 ULS engine is a testament to innovative design and engineering. Its superior performance, high fuel efficiency, and lightweight design make it a top choice for light sport and ultralight aircraft. Whether you’re a pilot or an aviation enthusiast, the Rotax 912 ULS engine offers a blend of power and efficiency that’s hard to beat.

About the Author

Kevin Baker loves everything about small planes, especially LSA. He's not just an enthusiast, he's also a flight teacher who loves sharing his passion for flying. Kevin uses his love and knowledge of planes to write articles, that make the thrilling world of flying exciting and accessible for everyone.