A propeller 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. 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. Most marine propellers are screw propellers with helical blades rotating on a propeller shaft with an approximately horizontal axis.
A 'right-handed' propeller on a merchant vessel, which rotates clockwise to propel the ship forward
Propeller of Pratt & Whitney Canada PW100 turboprop mounted on Bombardier Q400
Archimedes' screw
Smith's original 1836 patent for a screw propeller of two full turns. He would later revise the patent, reducing the length to one turn.
An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or the dynamic lift of an airfoil, or, in a few cases, direct downward thrust from its engines. Common examples of aircraft include airplanes, helicopters, airships, gliders, paramotors, and hot air balloons.
The Cessna 172 Skyhawk is the most produced aircraft in history.
Hot air balloons
Airship USS Akron over Manhattan in the 1930s
An Airbus A380, the world's largest passenger airliner