Editing Propeller (section)

{{Short description|Device that transmits rotational power into air movement thrust on a fluid}}
{{About||aircraft propellers|Propeller (aeronautics)||Propeller (disambiguation)}}
[[File:Ship-propeller 2000.jpg|thumb|upright=1.35|A 'right-handed' propeller on a merchant vessel, which turns the ship forward. The man's hand rests on the trailing edge.]]
[[File:Pratt & Whitney Canada PW100 Dash 8 OE-LGD 01.JPG|thumb|upright=1.35|Propeller of [[Pratt & Whitney Canada PW100]] [[turboprop]] mounted on [[Bombardier Q400]]]]

A ''' propeller''' (often called a '''screw''' if on a [[ship]] or an '''airscrew''' if on an [[aircraft]]) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear [[thrust]] upon a working fluid such as water or air.<ref>{{Cite web|url= https://www.britannica.com/technology/propeller|title=Propeller |website=Encyclopedia Britannica |access-date=2019-12-04}}</ref>  Propellers are used to pump fluid through a pipe or duct, or to create thrust to propel a [[boat]] through water or an [[aircraft]] through air.  The blades are shaped so that their [[rotational]] motion through the fluid causes a pressure difference between the two surfaces of the blade by [[Bernoulli's principle]] which exerts force on the fluid.<ref>{{Cite web|url=  https://www.grc.nasa.gov/WWW/K-12/airplane/propeller.htm | publisher = NASA | title = Propeller Propulsion|date= May 5, 2015}}</ref> Most marine propellers are '''screw propellers''' with helical blades rotating on a [[propeller shaft (ship)|propeller shaft]] with an approximately horizontal axis.{{Efn | On many boats, the prop shaft is not horizontal but dips towards the stern. Although this is often forced upon the designer by hull shape, it gives a small benefit by helping to counter any [[squat effect]].}}