{{Short description|Four cylinder piston aircraft engine}} {{Use dmy dates|date=March 2023}} {{Use American English|date=March 2023}} {{infobox aero engine | name= Rotax 912 | image=3Xtrim3X55TrainerC-IFUF46Rotax912Sinstallation.jpg | caption=Rotax 912ULS {{convert|100|hp|abbr=on}} installation in a [[3Xtrim 3X55 Trener]] | engine_type = [[Piston]] [[aircraft engine]] | national_origin = Austria |produced=1989–present |first_run=1984 | manufacturer = [[Rotax Aircraft Engines]] | major_applications = {{ubl|[[Light Sport Aircraft|Light sport aircraft]]|[[ultralight aviation|Ultralight aircraft]]}} |variants_with_their_own_articles= {{ubl|[[Rotax 914]]|[[Rotax 915 iS]]}} }} [[File:Rotax912SEngineInstallationMerlin.jpg|thumb|right|Rotax 912ULS {{convert|100|hp|abbr=on}} installation in a [[Blue Yonder Merlin EZ]]]] [[File:LezaLockwoodAirCamTwinRotax912SEngines.jpg|thumb|right|Pusher engine installation of two Rotax 912ULSs in a [[Lockwood Aircam]]]] [[File:Rotax912sDynAeroMcr01.jpg|thumb|right|Rotax 912ULS with [[tuned exhaust]] in a [[Dyn'Aéro MCR01]] with 3-blade hydraulic [[Constant speed propeller|CSU]] propeller]]
The '''Rotax 912''' is a [[flat-four engine|horizontally-opposed four-cylinder]], [[naturally-aspirated]], [[four-stroke engine|four-stroke]] [[aircraft engine]] with a [[Propeller speed reduction unit|reduction gearbox]]. It features [[Radiator (engine cooling)|liquid-cooled]] cylinder heads and [[air cooling|air-cooled]] cylinders. Originally equipped with [[carburetor]]s, later versions are [[fuel injected]]. Dominating the market for small aircraft and [[kitplane]]s, [[Rotax]] produced its 50,000th 912-series engine in 2014.<ref>{{cite web|title=Rotax Rolls Out 50,000 912-Series Engine|url=http://www.avweb.com/avwebflash/news/Rotax-Rolls-Out-50000-912-Series-Engine222133-1.html|access-date=7 June 2014|date=2014-06-06}}</ref> Originally available only for [[Light Sport Aircraft|light sport aircraft]], [[ultralight aviation|ultralight aircraft]], [[autogyro]]s and [[unmanned aerial vehicle|drones]], the 912-series engine was approved for [[type certificate|certified]] aircraft in 1995.<ref name="E00051EN">{{cite web|url = https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/e121f64f6e98b66b86258050006bb696/$FILE/E00051EN_Rev6.pdf|title = Type Certificate Data Sheet No. E00051EN |access-date = 16 August 2020|author = Federal Aviation Administration|author-link = Federal Aviation Administration|date = 11 October 2016|archive-url = https://web.archive.org/web/20161113024203/https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/e121f64f6e98b66b86258050006bb696/$FILE/E00051EN_Rev6.pdf|archive-date = 13 November 2016|url-status= live}}</ref>
==Design and development==
The Rotax 912 was first sold in 1989 in non-[[Type certificate|certificated]] form for use in [[Ultralight aviation|ultralights]] and [[motorglider]]s.<ref name=AOPA_2017>{{cite news |last=Busch |first=Mike |date=1 June 2017 |title=Opinion: Savvy Maintenance - Outside the Box: The Rotax 912 is Delightfully Different |url=https://www.aopa.org/news-and-media/all-news/2017/june/pilot/savvy-maintenance-rotax-912 |work=AOPA Pilot |publisher=[[Aircraft Owners and Pilots Association]] |access-date=10 April 2020 }}</ref> The original {{cvt|80|hp|order=flip}} 912 UL engine has a capacity of {{convert|1211|cc|cuin|abbr=on}} and a compression ratio of 9.1:1, and is designed to work with regular automotive gasoline, with up to 10% ethanol. The later certified {{cvt|100|hp|order=flip}} [[Rotax 912 ULS|912 ULS]] variant has a compression ratio of 11:1, and requires 91-octane ("premium") auto gas (100LL leaded [[avgas]] can be used, sparingly).<ref name="firewall_2013_07_19_kitplanes">Prizio, Dave: [https://www.kitplanes.com/firewall-forward-rotax-service-training/ "Firewall Forward: Rotax service Training,"] July 19, 2013, ''Kitplanes,'' retrieved July 5, 2023</ref>
The engine differs from previous generation aircraft engines (such as the [[Lycoming O-235]]) in that it has air-cooled cylinders with liquid-cooled heads<ref name="912OperatorsManual">{{cite web|url = http://www.flyrotax.com/portaldata/5/dokus/d06151.pdf|title = Operators Manual for Rotax engine type 912 series |access-date = 21 June 2015|author = Rotax|date = September 2012|author-link = Rotax }}</ref> and uses 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 (aircraft)|propeller]]. The gearbox has proven to be generally trouble-free.<ref name=AOPA_2017/> On the 912A, F and UL the standard reduction ratio is 2.27:1 with 2.43:1 optional. Lubrication is [[dry sump]], and fuel is supplied via dual [[Carburetor#Constant vacuum carburetors|CV carburetors]], or fully redundant electronic fuel injection in the 912iS.<ref>{{Cite web |date=January 1, 2023 |title=Operators Manual for Rotax Engine Type 912 Series Edition 4 Revision 1 |url=https://rotax.my.salesforce-sites.com/DocumentsSearch/sfc/servlet.shepherd/version/download/0685c00000IhJYnAAN |website=Rotax}}</ref>
The 912's lubrication system differs from most dry-sump designs in that oil is forced into the storage tank by [[crankcase]] pressure rather than by a separate scavenge pump. This requires a novel preflight inspection procedure: before checking the oil level with the [[dipstick]], the engine is "burped" by removing the oil filler cap and turning the propeller until a gurgling sound is heard, which indicates that all oil has been forced into the tank and the oil level can now be checked accurately.<ref name=AOPA_2017/>
A relatively unique feature is the inclusion of an overload clutch fitted as standard in all certified engines, and most non-certified models. In the event of a [[Propeller strike|prop strike]], the clutch disengages the prop from the drivetrain to avoid engine damage, and in many cases an expensive overhaul can be avoided. The gearbox is removed and inspected, and if the crankshaft is not out of round, the engine can be reassembled and placed back into service.<ref name=":0">{{Cite web |date=July 1, 2021 |title=Maintenance Manual Line for Engine Type 912 Series Edition 4 Revision 1 |url=https://rotax.my.salesforce-sites.com/DocumentsSearch/sfc/servlet.shepherd/version/download/0685c00000BM5VqAAL?asPdf=false |website=Rotax}}</ref> A torsional shock absorber consisting of 2 [[Dog clutch|dog gears]] serves to smooth the power pulses and reduce gearbox wear during startup and shutdown.<ref name="912OperatorsManual" />
The 912 is more fuel efficient and lighter than comparable older engines, ''e.g.'', [[Continental O-200]], but originally had a shorter [[time between overhaul]] (TBO). On introduction, the TBO was only 600 hours, which was double that of previous Rotax engines but far short of existing engines of comparable size and power. The short TBO and lack of certification for use in factory-built [[type certificate]]d aircraft initially restricted its worldwide market potential. However, the engine received US [[Federal Aviation Administration]] (FAA) certification in 1995, and by 1999, the TBO had increased to 1,200 hours;<ref name="AOPA_2017" /> on 14 December 2009, the TBO was raised from 1,200 hours to 1,500 hours, or 1,500 hours to 2,000 hours, depending on serial number.<ref name="SB-912-057 R1">{{cite web|url = http://legacy.rotax-owner.com/si_tb_info/serviceb/sb-912-057.pdf|title = Extension of Time Between Overhauls (TBO) for Rotax Engine Type 912 and 914 (Series) |access-date = 2010-02-11|last = Rotax|author-link = Rotax|date=December 2009}}</ref> In addition to the lower fuel consumption, the 912 is certified to run on automotive fuel (mogas), further reducing running costs, especially in areas where [[Tetraethyllead|leaded]] [[avgas]] is not readily available.<ref name="912OperatorsManual" /> The 912 may be operated using leaded fuel, however this will require more frequent maintenance when used more than 30% of the time. This is due to the accumulation of lead sludge in the oil tank, on spark plugs, and in older gearboxes which do not have an updated design that slings buildup away from the gears.<ref name=":0" />
A [[turbocharger|turbocharged]] variant rated at {{cvt|115|hp|kW|order=flip}}, the [[Rotax 914]], was introduced in 1996. In 1999, the 912S / ULS were introduced;<ref name=AOPA_2017/> enlarged to {{convert|1352|cc|cuin}} with a compression ratio of 10.8:1, yielding {{cvt|100|hp|order=flip}}. The 912S is certified, as are the A and F, which are used in the [[Diamond DA20]], which is quite popular in Europe. The 912's popularity was greatly enhanced by the introduction of the [[light-sport aircraft]] category in Europe and the United States, which resulted in the introduction of many factory-built aircraft designed to fully exploit the engine's small size and light weight.<ref name=AOPA_2017/> The {{cvt|100|hp|order=flip}} versions are used in many light sport aircraft, such as the [[Zenith STOL CH 701]] and the [[Tecnam P2002 Sierra]]. The {{cvt|80|hp|order=flip}} versions are sufficient to power the new generation of efficient motorgliders, such as the [[Pipistrel Sinus]] and the [[Urban Air#Lambada|Urban Air Lambada]]. It is also fitted to some light twins, such as the [[Tecnam P2006T]].
On 8 March 2012, the company announced the 912 iS variant, a {{cvt|100|hp|kW|order=flip}} version with [[fuel injection]] and [[FADEC]],<ref>{{cite journal|journal=Sport Aviation|title=Rotax Introduces 921iS|page=14|date=May 2012}}</ref> with ECUs supplied by [[Rockwell Collins]].<ref>{{cite web |last=Croft |first=John |date=2012-04-02 |title=Rotax, Rockwell Collins bring clout to small engines with 912iS |url=https://www.flightglobal.com/civil-uavs/rotax-rockwell-collins-bring-clout-to-small-engines-with-912is/104748.article |access-date=2025-07-03 |website=Flight Global }}</ref> The version weighs {{convert|63|kg|lb|0|abbr=on}}, which is {{convert|6|kg|lb|0|abbr=on}} more than the standard 912S. The non-certified 912 iS targets the light sport and homebuilt aircraft market and 912 iSc will be [[Type certificate|certified]]. Production started in March 2012, and the engine has a 2000-hour recommended time-between-overhaul.<ref name="Bertorelli08Mar12">{{cite news|url = http://www.avweb.com/avwebflash/news/BRP_Rotax_NewEngine_912iS_206291-1.html|title = BRP/Rotax Rolls Out New Engine |access-date = 14 March 2012|last = Bertorelli|first = Paul|date = 8 March 2012| work = AVweb}}</ref>
On 1 April 2014, the company announced its new 912 iS Sport upgrade with greater power, torque, and reduced fuel consumption.<ref>{{cite web|url=http://www.aopa.org/News-and-Video/All-News/2014/April/01/Rotax-upgrade.aspx|title=Rotax lowers fuel burn, boosts performance with 912 iS Sport|work=aopa.org|access-date=22 July 2015|date=April 2014}}</ref> A derivative, the {{cvt|140|hp|kW|-1|order=flip}} [[Rotax 915 iS]], was announced in July 2015,<ref>{{Cite web |date=July 21, 2015 |title=ROTAX 915 IS: BRP UNVEILS A NEW TURBOCHARGED ROTAX AIRCRAFT ENGINE |url=https://ir.brp.com/news-releases/news-release-details/rotax-915-brp-unveils-new-turbocharged-rotax-aircraft-engine |website=BRP}}</ref> and a further upgrade, the {{cvt|160|hp|kW|-1|order=flip}} [[Rotax 916 iS]] was announced in March 2023.<ref>{{Cite web |title=916iS Launch |url=https://www.flyrotax.com/n/916is-launch |access-date=2025-07-03 |website=Rotax Aircraft Engines |language=en}}</ref>
===Rotax's warnings to flyers=== Rotax publishes extensive warnings in the owner's manual about both the certified and non-certified versions of the engine design. Pilots are cautioned that the 912 engine is not suitable for: *use in situations where a safe landing cannot be made *use in [[rotorcraft]] *night flying (unless equipped with redundant electrical power), or *[[aerobatic]]s.
==Variants== The engine is available in the following versions; coloured cylinder head caps are used to easily identify the different horsepower ranges:{{cn|date=March 2023}}
;912 A# :Certified to [[Joint Aviation Requirements|JAR 22]], {{cvt|80|hp|order=flip}}, with dual carburetors and electronic ignition. Black cylinder head caps ;912 F# :Certified to [[Federal Aviation Regulations|FAR 33]], {{cvt|80|hp|order=flip}}, with dual carburetors and electronic ignition. Black cylinder head caps ;912 iS :Uncertified, {{cvt|100|hp|order=flip}} with direct fuel injection and an electronic engine management unit.<ref name="Bertorelli08Mar12" /> Green cylinder head caps ;912 iSc :Certified, {{cvt|100|hp|order=flip}} with direct fuel injection and an electronic engine management unit<ref name="Bertorelli08Mar12" /> ;912 iS Sport :Uncertified, aluminum airbox, longer intake runners and eco-mode when operated below 97% power setting.<ref>{{cite journal|journal=Sport Aviation|date=May 2014|page=14}}</ref><ref>{{cite web|url=http://generalaviationnews.com/2013/06/27/rotax-912-is-better-than-predicted/|title=Rotax 912 iS: Better than predicted|date=27 June 2013|work=generalaviationnews.com|access-date=10 August 2016}}</ref> Green cylinder head caps ;912 iSC Sport Green cylinder head caps ;912 S# :Certified to [[Federal Aviation Regulations|FAR 33]], {{cvt|100|hp|order=flip}} with larger bore than 912A/F/UL, with dual carburetors and electronic ignition. Green cylinder head caps ;912 UL# :Uncertified, {{cvt|80|hp|order=flip}}, similar to the 912A/F. Black cylinder head caps ;912 ULS# :Uncertified, {{cvt|100|hp|order=flip}}, similar to the 912S. Green cylinder head caps ;912 ULSFR# :Uncertified French Authority specification. {{cvt|100|hp|order=flip}}
The # in the designation stands for: # Shaft with flange for fixed pitch propeller, P.C.D. 100 mm # Shaft with flange for fixed pitch propeller, P.C.D. 75 mm, P.C.D. 80 mm and P.C.D. 4 inches # 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 # Shaft with flange for fixed pitch 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)== {{pistonspecs| <!-- If you do not understand how to use this template, please ask at [[Wikipedia talk:WikiProject Aircraft]] --> <!-- Please include units where appropriate (main comes first, alt in parentheses). If data are missing, leave the parameter blank (do not delete it). For additional lines, end your alt units with )</li> and start a new, fully formatted line with <li> --> |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 cm<sup>3</sup> (73.91 in<sup>3</sup>) |length=561 mm (22.1 in) |diameter= |width=576 mm (22.7 in) |height= |weight=60 kg (132.3 lb) with electric starter, carburetors, fuel pump, air filters and oil system |valvetrain=OHV, hydraulic lifters, pushrods, rocker arms |supercharger= |turbocharger= |fuelsystem= |fueltype=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. |oilsystem=Dry sump with [[trochoid pump]], camshaft driven |coolingsystem=Liquid-cooled cylinder heads, air-cooled cylinders |power={{convert|59.6|kW|abbr=on}} at 5,800 rpm Power density: 48.71 kW/L |compression=9:1 |fuelcon=15.0 [[litre|liters]]/[[hour|h]] at 5,000 rpm (75% power) |specfuelcon=285 [[gram|g]]/([[kilowatt|kW]]·[[hour|h]]) at 5,500 rpm (maximum continuous power) Specific power: 0.98 kW/kg }}
==See also== {{aircontent <!-- other related articles that have not already linked: --> |see also=
<!-- designs which were developed into or from this aircraft: --> |related=
<!-- aircraft that are of similar role, era, and capability as this design: --> |similar aircraft=
<!-- relevant lists that this aircraft appears in: --> |lists= *[[List of aircraft engines]] <!-- For aircraft engine articles. Engines that are of similar to this design: --> |similar engines= *[[Arrow 1000]] *[[D-Motor LF26]] *[[Hirth 3701]] *[[Hirth F-30]] *[[HKS 700E]] *[[Jabiru 2200]] *[[KFM 112M]] *[[Pegasus PAL 95]] *[[Revmaster R-2300]] *[[Sauer S 2200 UL]] *[[Sauer S 2100 ULT]] *[[Sauer S 2400 UL]] *[[ULPower UL260i]] * <!-- See [[WP:Air/PC]] for more explanation of these fields. --> }}
==References== {{Reflist}}
==External links== {{Commons category}} *[https://www.flyrotax.com/p/products/engines The aircraft engines section of the official Rotax company website] *[https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/16EFDC3281BA32408625805E0059BE06?OpenDocument&Highlight=e00051en FAA Type Certificate Data Sheet E00051EN] *[http://www.rotaxservice.com/documents/912info.pdf 912 UL 80 hp Engine Datasheet] *[http://www.rotaxservice.com/documents/912Sinfo.pdf 912 ULS 100 hp Engine Datasheet] *[http://www.rotaxservice.com/documents/914info.pdf 914 UL 115 hp Turbocharged Engine Datasheet] *[http://motive.aero Motive.Aero Rotax Distributor]
{{Rotax aeroengines}}
[[Category:Boxer engines]] [[Category:Rotax engines]] [[Category:1980s aircraft piston engines]]