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Turbomeca Arrius 2K1 Turboshaft

Turbomeca, a division of SNECMA, is the foremost producer of medium power turboshaft engines for civil and military helicopters throughout the world. Most european helicopters in operation today utilize a turbomeca engine. These engines are noteworthy for their clean designs, compact and lightweight construction, fantastic reliability, and rapid response. The most striking aspect of a typical turbomeca engine is the miniscule size for the amount of power the engine produces. This size to power ratio is what makes Turbomeca engines the leaders in their class, and highly sought after for use by helicopter designers of today.

The Turbomeca Arrius, which is the smallest unit in their expansive line of helicopter turboshafts, embodies the Turbomeca design philosophy to the fullest degree. In its 2K1 iteration, this tiny nugget of an engine, weighing a little over 250 lbs., can produce a takeoff rating of 670 horsepower, or 715 horsepower in the newly uprated version. One Engine Inoperative contingiency ratings allow the Arrius to put a shaft twisting 800 shaft horsepower for 2.5 minutes, in an emergency.

The design of the Arrius is noteworthy for its simplicity and functionality. Air is drawn in through a screened radial inlet between the front mounted gearbox and the compressor section of the engine. The inlet is known to have the lowest inlet (friction) losses on the market. Air is drawn up by a simple single stage centrifugal compressor with a high surge margin for rapid acceleration and high pressure ratio. Though pressure ratio is not published, it is probably in the neighborhood of 8-9:1; about peak for a modern swept vane centrifugal compressor, before major compressor efficiency losses begin to take place. The compressor feeds air to an annular reverse flow combustor designed for space efficiency as well as high efficiency of combustion. Power to drive the compressor and accessories is extracted from the combustion energy by a single crystal formed axial high pressure turbine. Power to drive the helicopter transmission is taken from a second axial free power turbine. The free power turbine is located at the very rear of the engine for easy access, and the exhaust gas is expanded through this turbine before it is directed through a standard axial flow exhaust diffuser. The power turbine drives a shaft forward coaxially through the center of the high pressure shaft to the combination accessory/output reduction gearbox. In an effort to save space, the Arrius utilizes a front mounted common gearbox case for both the output reduction geartrain and the accessory geartrain. Accessories are mounted to the front of the gearbox while the engine output is offset down and comes out at 6,000 rpm to drive a helicopter transmission. Engines such as the Lycoming LTS101 and Pratt & Whitney PW200 turboshaft use very similar layouts combining a very simplified turbomachine combined with a front mounted combined gearbox. In fact, the Pratt & Whitney PW200 is almost identical in layout and in specification to the Arrius.

The Turbomeca Arrius can be found in many light to medium sized helicopters, including the Eurocopter EC120 Colibri, which can often be seen flying over the city of New York giving tours.


Turbomeca Arrius 2K1 Turboshaft

  • Type: two spool, free shaft turboshaft
  • Inlet: Radial
  • Compressor: Single stage centrifugal
  • Burner: Annular, reverse flow
  • Turbine: two spool, single stage axial gas producer turbine, single stage axial free power turbine
  • Exhaust: Rear exit, axial flow jet-type diffuser outlet
  • Power Rating: 690 shaft horsepower at 6,000 rpm
  • Rated Torque Output: 600 lb/ft at 6,000 rpm
  • Weight: 251 lbs.
  • Power/weight: 2.76:1
  • Pressure Ratio: est. 9:1
  • Specific Fuel Consumption: est. .54 lb/shp/hr



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