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Rotax Aircraft Engine

Rotax Aircraft Engines, Limitations

Rotax four stroke aircraft engines have proven themselves as reliable pieces of machinery. They can be bought as experimental (UL), sport (S) or certified (A and F) engine and there are four main models (fuel injected too: i models) to date. The original engine is the 80 hp 912, from which the 100 hp 912S was developed and Rotax also has a 115 hp turbocharged 914 engine. In 2015 BRP-Rotax announced the fuel injected 141 hp turbocharged 915iS.

Recognizing the different models is easy: the 912 has black cylinder covers, the 912S green/blue (blue for the French market), the 912iS is green but without the carburetors and the 914 has red covers and a turbo. The 915 is a turbocharged version of the 912iS with blue covers. These are the most obvious differences.

As all engines, even the Rotax has its limitations in power, RPM, fuel and other temperatures. Keep in mind that we present this info without any warranty. The manuals from Rotax remain authoritative at any time.

Rotax Operating Limits

All Rotax four strokes have more or less the same limitations in RPM, temperatures and fuel requirements. Below a quick reference guide. Again, refer to the official manuals for the finer details.

General Operating Limitations
Takeoff RPM (max 5 min) 5800
Max Continuous RPM 5500
Idle RPM 1400
912 UL/A/F power at 5800 59,6 kW / 81 hp
912 UL/A/F power at 5500 58 kW / 79 hp
912 ULS/ULSFR/S/iS power at 5800 73,5 kW / 100 hp
912 ULS/ULSFR/S/iS power at 5500 69 kW / 95 hp - 72 kW / 98 hp (iS)
914 UL/F power at 5800 84,5 kW / 115 hp
914 UL/F power at 5500 73,5 kW / 100 hp up to 15000 ft
915 iS power at 5800 104 kW / 141 hp
915 iS power at 5500 99 kW / 135 hp up to 15000 ft
Volume Oil Tank At max: 3,0 l - at min: 2,5 l
Oil pressure 7 bar max at cold engine start
Min Oil pressure 0,8 bar below 3500 RPM (1,5 bar older models)
Normal Oil pressure 2 - 5 bar above 3500 RPM (1,5 - 5 bar older models)
Max Oil Consumption 0,06 L per hour
Max Oil Temperature ULS/S 130 °C (ULS/ULSFR/S) 140 °C (UL/A/F)
Min Oil Temperature 50 °C
Normal Oil Temperature 90 - 110 °C
Max Cylinder Head Temperature 135 °C (ULS/ULSFR/S) (150 °C UL/A/F)
Ideal CHT 75 - 110 °C
Fuel pressure 0,15 - 0,4 bar
Hydraulic governor 600 W
Vacuum pump 300 W
Alternator 1200 W

Rotax Fuel requirements

The engine is built for lead free mogas, running it on AVGAS (100LL or 100) is possible but do take note of the limitations. Service Instructions SI-18-1997-R5 and SI-912-016-914-019 from Rotax explains it in more detail.

Fuel Requirements
912 UL / A / F 912 ULS / ULSFR / S
min. ROZ 90 min. ROZ 95
EN 228 Normal -------------
EN 228 Super EN 228 Super
EN 228 Super Plus EN 228 Super Plus

Make sure to always use clean and fresh fuel from a pump with a high daily volume.

Written by EAI.

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