Editing Turbofan (section)

===Thrust===
While a turbojet engine uses all of the engine's output to produce thrust in the form of a hot high-velocity exhaust gas jet, a turbofan's cool low-velocity bypass air yields between 30% and 70% of the total thrust produced by a turbofan system.<ref>{{cite book |url= http://www.faa.gov/library/manuals/aircraft/airplane_handbook/media/FAA-H-8083-3B.pdf |title= FAA-H-8083-3B Airplane Flying Handbook Handbook|publisher=Federal Aviation Administration |year= 2004 |url-status=dead|archive-url= https://web.archive.org/web/20120921094453/http://www.faa.gov/library/manuals/aircraft/airplane_handbook/media/FAA-H-8083-3B.pdf |archive-date=2012-09-21}}</ref>

The thrust ('''''F<sub>N</sub>''''') generated by a turbofan depends on the [[effective exhaust velocity]] of the total exhaust, as with any jet engine, but because two exhaust jets are present the thrust equation can be expanded as:<ref>{{Cite web|url=https://www.grc.nasa.gov/WWW/K-12/airplane/turbfan.html|title=Turbofan Thrust|website=Grc.nasa.gov|access-date=1 March 2022}}</ref>

<math display="block">F_N = \dot{m}_e v_{he} - \dot{m}_o v_o + BPR\, (\dot{m}_c) v_f</math>

where:
* {{math|{{var|{{overset|•|m}}}}{{sub|{{var|e}}}}}} = the mass rate of hot combustion exhaust flow from the core engine
* {{math|{{var|{{overset|•|m}}}}{{sub|{{var|o}}}}}} = the mass rate of total air flow entering the turbofan = {{math|{{var|{{overset|•|m}}}}{{sub|{{var|c}}}} + {{var|{{overset|•|m}}}}{{sub|{{var|f}}}}}}
* {{math|{{var|{{overset|•|m}}}}{{sub|{{var|c}}}}}} = the mass rate of intake air that flows to the core engine
* {{math|{{var|{{overset|•|m}}}}{{sub|{{var|f}}}}}} = the mass rate of intake air that bypasses the core engine
* {{math|{{var|v}}{{sub|{{var|f}}}}}} = the velocity of the air flow bypassed around the core engine
* {{math|{{var|v}}{{sub|{{var|he}}}}}} = the velocity of the hot exhaust gas from the core engine
* {{math|{{var|v}}{{sub|{{var|o}}}}}} = the velocity of the total air intake = the true airspeed of the aircraft
* {{mvar|BPR}} = bypass ratio