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Aviation glossary

Open rotor

Also: propfan, unducted fan, open fan, UDF

Engines

Turbine engine whose large blades spin in the open air without a casing, achieving a very high bypass ratio and lower fuel burn than a turbofan.

What it is

An open rotor blends features of the turbofan and the turboprop: a gas turbine core drives one or two rows of large, strongly curved blades that are not enclosed by a nacelle. Without a casing the diameter can be much larger and the effective bypass ratio very high, cutting fuel burn at cruise speeds close to those of today's jets.

The idea was flight-tested in the 1980s with demonstrators such as General Electric's GE36, which flew on an MD-80, but it did not reach production because of noise, the difficulty of integrating it with the airframe and the fall in oil prices.

It is back today through CFM International's RISE programme, which is studying an open fan with a single row of rotating blades followed by a row of stationary vanes, aiming for fuel consumption more than 20 per cent lower than current engines.

On Vuelopedia

McDonnell Douglas MD-80 CFM International

Related terms

TurbofanJet engine in which a large front fan drives air around the core, producing most of the thrust with greater efficiency and less noise. TurbopropGas turbine engine that drives a propeller through a reduction gearbox, with the propeller rather than the exhaust producing almost all the thrust. PropellerSet of blades with an aerofoil section that, as it rotates, accelerates a large mass of air rearwards to produce thrust for piston and turboprop aircraft. Bypass ratioRatio between the mass of air that flows around a turbofan's core through the outer duct and the mass that passes through the core to be burnt. Specific fuel consumptionAmount of fuel an engine burns for each unit of thrust or power it produces over a given time; the standard measure of engine efficiency.
Whole glossary

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This page was last updated on October 9, 2026

APA

Vuelopedia. (2026, October 9). Open rotor. Retrieved October 16, 2026, from https://vuelopedia.org/en/glossary/open-rotor

MLA

“Open rotor.” Vuelopedia, Fundación Poderia, 9 Oct. 2026, vuelopedia.org/en/glossary/open-rotor. Accessed 16 Oct. 2026.

Chicago

Vuelopedia. “Open rotor.” Fundación Poderia. Last modified October 9, 2026. https://vuelopedia.org/en/glossary/open-rotor.

Harvard

Vuelopedia (2026) Open rotor. Available at: https://vuelopedia.org/en/glossary/open-rotor (Accessed: 16 October 2026).

BibTeX

@misc{vuelopedia_en_glossary_open_rotor,
  author       = {{Vuelopedia}},
  title        = {{Open rotor}},
  publisher    = {Fundación Poderia},
  year         = {2026},
  date         = {2026-10-09},
  url          = {https://vuelopedia.org/en/glossary/open-rotor},
  howpublished = {\url{https://vuelopedia.org/en/glossary/open-rotor}},
  urldate      = {2026-10-16},
  note         = {Accessed 2026-10-16}
}

Wikipedia

{{cite web |url=https://vuelopedia.org/en/glossary/open-rotor |title=Open rotor |website=Vuelopedia |publisher=Fundación Poderia |date=2026-10-09 |access-date=2026-10-16 |language=en}}

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