Rotax 912

The Rotax 912 is a naturally aspirated, air- and water-cooled, horizontally opposed four-cylinder, four-stroke, gear reduction-drive engine commonly used on certified aircraft, light sport aircraft, ultralight aircraft and unmanned aerial vehicles. Rotax produced its 50,000th 912-series engine in 2014.[1]

Rotax 912
Rotax 912ULS 100 hp (75 kW) installation in a 3Xtrim 3X55 Trener
Type Piston aircraft engine
National origin Austria
Manufacturer Rotax Aircraft Engines
First run 1984
Major applications Light sport aircraft
Ultralight aircraft
Produced 1989–present
Variants Rotax 914
Rotax 915 iS


The original 80 hp (60 kW) 912 UL engine has a capacity of 1,211 cc (73.9 cu in) and a compression ratio of 9.1:1. The later 912S / ULS is enlarged to 1,352 cubic centimetres (82.5 cu in) and has a compression ratio of 10.8:1, yielding 100 hp (75 kW). The 912 A and F are used in certified aircraft, such as the Diamond DA20, which is quite popular in Europe. The 100 hp (75 kW) versions are used in many light sport aircraft, such as the Zenith STOL CH 701 and the Tecnam P2002 Sierra. The 80 hp (60 kW) versions are sufficient to power the new generation of efficient motorgliders, such as the Pipistrel Sinus and the Urban Air Lambada. It is also fitted to some light twins, such as the Tecnam P2006T.

The engine differs from conventional aircraft engines (such as the Lycoming O-235) in that it has air-cooled cylinders with liquid-cooled heads[2] and uses a 2.43:1 gearbox (PSRU) to reduce the engine's relatively high 5,800 rpm shaft speed to a more conventional 2,400 rpm for the propeller. On the 912A, F and UL the standard reduction ratio is 2.27:1 with 2.43:1 optional. Lubrication is dry sump, and fuelling is via dual CV carburetors or fully redundant electronic fuel injection. The electronic fuel injected Rotax 912iS is a recent development.[2] A further derivative, the 135 hp (101 kW) Rotax 915 iS was announced in July 2015.[3]

Early 912 series engines have a shorter time between overhaul (TBO) than traditional engines, but are more fuel efficient than similarly sized engines, e.g., Continental O-200. Effective 14 December 2009, 912 engines have had their recommended Time Between Overhauls (TBO) raised from 1,200 hours to 1,500 hours, or 1,500 hours to 2,000 hours, depending on serial number.[4] In addition to the lower fuel consumption they are certified to run on automotive fuel (mogas), further reducing running costs, especially in areas where leaded AVGAS is not readily available.[2] The engines are popular in Europe and in United States Light Sport Category aircraft due to high power-to-weight ratio, low fuel costs and relatively quiet operation.

On 8 March 2012 the company displayed its 912 iS variant, a 100 hp (75 kW) version with fuel injection and an electronic engine management unit.[5] The version weighs 63 kg (139 lb), which is 6 kg (13 lb) more than the standard 912S. The non-certified 912 iS targets the Light Sport and Experimental market and 912 iSc will be certified. Production started in March 2012 and the engine has a 2000-hour recommended time-between-overhaul to start.[6]

On 1 April 2014 the company announced its new 912 iS Sport upgrade with greater power and torque and reduced fuel consumption.[7]


Unlike most other manufacturers of similar engines, Rotax provides extensive warnings in the owner's manual, about both the certified and non-certified versions of the engine design, warning pilots that the engine is not suitable for use in situations where a safe landing cannot be made, for use in rotorcraft, for night flying (unless equipped with redundant electrical power), or for aerobatics. It furthermore states that the company gives no assurances that the engine is suitable for use in any aircraft, that the "engine may seize or stall at any time. This could lead to a crash landing and possible severe injury or death" and that "non-compliance [with the warnings provided] can result in serious injuries or death!"[8]


The engine is available in the following versions:

912 A#
Certified to JAR 22, 80 hp (60 kW)
912 F#
Certified to FAR 33, 80 hp (60 kW)
912 iS
Uncertified, 100 hp (75 kW) with direct fuel injection and an electronic engine management unit[6]
912 iSc
Certified, 100 hp (75 kW) with direct fuel injection and an electronic engine management unit[6]
912 iS Sport
Uncertified, aluminum airbox, longer intake runners and eco-mode when operated below 97% power setting.[9][10]
912 S#
Certified to FAR 33, 100 hp (75 kW)
912 UL#
Uncertified, 80 hp (60 kW)
912 ULS#
Uncertified, 100 hp (75 kW)
912 ULSFR#
Uncertified French Authority specification. 100 hp (75 kW)

The # in the designation stands for:

  1. Shaft with flange for fixed pitch propeller, P.C.D. 100 mm
  2. Shaft with flange for fixed pitch propeller, P.C.D. 75 mm, P.C.D. 80 mm and P.C.D. 4 inches
  3. Shaft with flange for constant speed propeller P.C.D. 75 mm, P.C.D. 80 mm, P.C.D. 4 inches and drive for hydraulic governor for constant speed propeller
  4. Shaft with flange for fixed speed propeller P.C.D. 75 mm, P.C.D. 80 mm, P.C.D. 4 inches also can be fitted with an adaptor, drive and governor for a constant speed propeller.


Specifications (Rotax 912 UL/A/F)

General characteristics

  • Type: four-cylinder, four-stroke liquid / air-cooled engine with opposed cylinders, dry sump forced lubrication with separate oil tank, automatic adjustment by hydraulic valve tappet, dual CD carburetors, mechanical diaphragm pump, electronic dual ignition, electric starter, integrated reduction gear 1 : 2.273 or 1 : 2.43
  • Bore: 79.5 mm (3.13 in)
  • Stroke: 61 mm (2.40 in)
  • Displacement: 1,211.2 cm3 (73.91 in3)
  • Length: 561 mm (22.1 in)
  • Width: 576 mm (22.7 in)
  • Dry weight: 60 kg (132.3 lb) with electric starter, carburetors, fuel pump, air filters and oil system


  • Valvetrain: OHV, hydraulic lifters, pushrods, rocker arms
  • Fuel type: Unleaded: 87 octane AKI (Canada/USA) / 90 octane RON (European) or higher. Leaded fuel and AVGAS 100 LL can be used but are not recommended.
  • Oil system: Dry sump with trochoid pump, camshaft driven
  • Cooling system: Liquid-cooled cylinder heads, air-cooled cylinders


See also

Comparable engines

Related lists


  1. "Rotax Rolls Out 50,000 912-Series Engine". 2014-06-06. Retrieved 7 June 2014.
  2. Rotax (September 2012). "Operators Manual for Rotax engine type 912 series" (PDF). Retrieved 21 June 2015.
  4. Rotax (December 2009). "Extension of Time Between Overhauls (TBO) for Rotax Engine Type 912 and 914 (Series)" (PDF). Retrieved 2010-02-11.
  5. "Rotax Introduces 921iS". Sport Aviation: 14. May 2012.
  6. Bertorelli, Paul (8 March 2012). "BRP/Rotax Rolls Out New Engine". AVweb. Retrieved 14 March 2012.
  7. "Rotax lowers fuel burn, boosts performance with 912 iS Sport". April 2014. Retrieved 22 July 2015.
  8. BRP-Rotax (1 September 2012). "Operators Manual Rotax Type 912 Series" (PDF). Archived from the original (PDF) on 30 June 2014. Retrieved 5 August 2014.
  9. Sport Aviation: 14. May 2014. Missing or empty |title= (help)
  10. "Rotax 912 iS: Better than predicted". 27 June 2013. Retrieved 10 August 2016.
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