915 iS aircraft combustion engine

The Rotax 915 iS is a turbocharged four-cylinder, four-stroke aircraft piston engine from Rotax (BRP-Rotax), with electronic fuel injection and ignition, an intercooler, a propeller reduction gearbox and an electric starter. It is used as a combustion powerplant for light fixed-wing aircraft, and as a propulsion or range-extension engine in larger uncrewed aircraft and hybrid installations. The iSc version is certified to EASA CS-E and the iS version is ASTM compliant.

The main figures are a maximum power of 104 kW and a maximum continuous power of 99.0 kW at 5,500 rpm. Displacement is 1,352 cm3, with a bore of 84.0 mm and a stroke of 61.0 mm. The turbocharger and intercooler keep the power available at altitude, and the engine has a service ceiling of 7,010.4 m (23,000 ft). Time between overhaul is 1,200 hours, which feeds directly into the operating cost and maintenance planning of an aircraft fleet.

Mass is 82.2 kg for the engine with gearbox, turbocharger, intercooler and exhaust. Accessories are listed separately: the engine suspension frame at 2.0 kg, the external alternator at 3.0 kg, the air guide hood at 0.4 kg and the fuel pump assembly at 1.6 kg. An integrator must add these to the installed mass.

Engine management is by an electronic management system with redundant fuel injection and ignition, and an eco mode. The engine accepts leaded and unleaded gasoline, AVGAS 100LL and ethanol 10 fuel, with a minimum rating of MON 85, RON 95 or AKI 91, which gives flexibility in fuel supply for remote operations.

Cooling is combined: liquid-cooled cylinder heads and air-cooled cylinders, so the airframe needs a radiator and an air guide in addition to the engine. Lubrication is by a dry-sump forced system with a separate oil tank, and hydraulic valve tappets adjust the valve clearance automatically. The exhaust is stainless steel.

For installation, the propeller reduction gearbox has a ratio of 2.54 and includes an overload clutch. The electric starter is available in 12 V and 24 V versions, and the external alternator supports a 24 V supply delivering up to 800 W.