Trisha Shetty (Editor)

Rotax 447

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The Rotax 447 is a 41.6 hp (31 kW), inline 2-cylinder, two-stroke aircraft engine, built by BRP-Rotax GmbH & Co. KG of Austria for use in ultralight aircraft.


Design and development

The Rotax 447 is a development of the Rotax 377, increasing the power output from 26 kW (35 hp) to 29.5 kW (40 hp) by increasing the cylinder bore from 62 mm to 67.5 mm and the maximum rpm from 6500 to 6800. The modern 447 has a single breakerless, magneto capacitor-discharge ignition (CDI) system. Early (ca. 1988) models use a breaker point ignition system.

The Rotax 447 features piston-ported, air-cooled cylinder heads and cylinders, utilizing either a fan or free air for cooling. Lubrication is by use of pre-mixed fuel and oil. The engine can be equipped with either one or two piston-type float carburetors. The dual-carburetor version uses Bing model 84 carburetors. The single-carburetor version uses a Bing model 54 carburetor. An optional High Altitude Compensation kit is available. It is typically installed with an induction-pulse-driven diaphragm fuel pump to provide fuel pressure.

The engine's propeller drive is via a Rotax type B gearbox. The standard engine includes a muffler exhaust system with an extra after-muffler as optional. The standard starter is a recoil start type, with an electric starter optional. An integral alternating current generator producing 170 watts at 12 volts with external rectifier-regulator is optional. The engine includes an intake air filter and can be fitted with an intake silencer system.

The manufacturer acknowledges the design limitations of this engine, warning pilots:

"This engine, by its design, is subject to sudden stoppage. Engine stoppage can result in crash landings, forced landings or no power landings. Such crash landings can lead to serious bodily injury or death...This is not a certificated aircraft engine. It has not received any safety or durability testing, and conforms to no aircraft standards. It is for use in experimental, uncertificated aircraft and vehicles only in which an engine failure will not compromise safety. User assumes all risk of use, and acknowledges by his use that he knows this engine is subject to sudden stoppage...Never fly the aircraft equipped with this engine at locations, airspeeds, altitudes, or other circumstances from which a successful no-power landing cannot be made, after sudden engine stoppage. Aircraft equipped with this engine must only fly in DAYLIGHT VFR conditions."


447 UL-1V
basic engine equipped with a single carburettor, 39.6 hp (30 kW) at 6800 rpm
447 UL-2V
basic engine equipped with two carburettors, 41.6 hp (31 kW) at 6800 rpm

Specifications (447)


General characteristics

  • Type: two-stroke air-cooled aeroengine
  • Bore: 67.5 mm (2.66 in)
  • Stroke: 61 mm (2.4 in)
  • Displacement: 426.5 cc (26.64 cu in)
  • Dry weight: 26.8 kg (59 lb) (dry, no exhaust system)
  • Components

  • Valvetrain: piston ports
  • Fuel system: pneumatic pump pressurized
  • Fuel type: regular autofuel
  • Oil system: premixed in the fuel at 50:1 or oil injection
  • Cooling system: fan or free air
  • Reduction gear: Rotax 'B' gearbox: 2.00, 2.24, 2.58 ratios
  • Performance

  • Power output: 30 kW (40 hp) at 6800 rpm
  • Compression ratio: 9.6 (theoretical) 6.3 (effective)
  • Fuel consumption: 11 litres/hr (3 US gph)
  • Power-to-weight ratio: 1.12 kW/kg (0.68 hp/lb)
  • References

    Rotax 447 Wikipedia

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