The Rotax 912 family brought modern automotive-derived engineering to light aviation: liquid-cooled heads for thermal management, integrated reduction gearbox, and dual ignition systems. The 912 S variant increased displacement from 1,211 cc to 1,352 cc with a larger bore, raising compression to 10.8:1 and pushing output to the 100 hp class that light sport aircraft demanded .
Rotax 912 S Design Features
The primary subject of this technical guide focuses on the Rotax 912 S engine, engineered specifically for 4-Cylinder, Horizontally Opposed, Liquid/ Air-Cooled Piston applications. Below is an essential digest of this powertrain configuration.
• 1,352 cc four-cylinder
• 100 hp class
• Liquid-cooled heads
• Automotive fuel capable
Rotax 912 S Technical Specifications
1,352 cc displacement; bore 84 mm, stroke 61 mm; compression ratio 10.8:1; reduction gear ratio 2.4286:1; liquid-cooled cylinder heads, ram-air cooled cylinders .
The 912 S uses carburetors on standard models (the 912 iS adds FADEC fuel injection). The integrated reduction gearbox with shock absorber and overload protection allows direct propeller mounting without a separate gearbox unit. The engine can operate on automotive gasoline or avgas, a significant cost advantage for private owners. Its liquid-cooled heads tolerate the higher compression ratio without detonation on pump fuel .
| Configuration | 4-cylinder, horizontally opposed |
|---|---|
| Bore | 84 mm (3.31 in) |
| Stroke | 61 mm (2.40 in) |
| Displacement | 1,352 cc (82.5 cu in) |
| Compression | 10.8:1 |
| Gear Ratio | 2.4286:1 |
| Cooling | Liquid heads, air cylinders |
| Fuel | Automotive gasoline or avgas |
Aircraft Using the Rotax 912 S
This engine model is deployed across various operational frameworks. Here is a breakdown of the typical machine or vehicle applications using this unit:
Light sport aircraft, ultralights, experimental aircraft (consult specific type certificates)
Pros & Advantages
Modern liquid-cooled head design; automotive fuel compatibility; integrated reduction gear; lightweight.
Cons & Disadvantages
Lower power than traditional aircraft engines; carbureted models require mixture management.
Frequently Asked Questions (FAQs)
Q1: What is the displacement of the Rotax 912 S?
A1: 1,352 cc (82.5 cu in) .
Q2: What is the compression ratio of the 912 S?
A2: 10.8:1, higher than the 9:1 of the 912 A/F series .
Q3: Can the Rotax 912 S run on automotive gasoline?
A3: Yes, it is designed to operate on automotive gasoline or avgas .
The standard 912 S uses carburetors; the 912 iS variant adds FADEC fuel injection .