Propeller (aeronautics)

**History and Evolution of Propellers:**
– Chinese children played with bamboo flying toys around 400 BC.
– Leonardo da Vinci designed an aerial screw in the early 1480s.
– Mikhail Lomonosov developed a coaxial model in 1754.
– Alphonse Pénaud created coaxial rotor model helicopter toys in 1870.
– The Wright brothers pioneered the twisted airfoil shape of aircraft propellers.

**Theory, Design, and Efficiency:**
– A Cessna 172 has a propeller efficiency of about 73.5% at cruise.
– Propeller efficiency is influenced by the angle of attack.
– Mahogany was the preferred wood for propellers through World War I.
– Propeller research for NACA was directed by William F. Durand from 1916.
– The original propeller blades by the Wright Brothers had an efficiency of about 82%.

**Materials and Construction Techniques:**
– Propellers can be made from wood, metal, or composite materials.
– Alberto Santos Dumont designed propellers with steel shafts and aluminum blades.
– Wartime shortages led to the use of walnut, oak, cherry, and ash for propeller construction.
– The Wright Brothers used mahogany for their propellers through World War I.

**Innovations and Advancements in Propeller Technology:**
– Sir George Cayley developed feather-powered models.
– William Bland showcased Atmotic Airship designs in 1851.
– Hiram Maxim built a craft powered by two 360hp steam engines.
– The Wright Brothers realized the similarity between a propeller and a wing.
– Pénaud’s toy inspired the Wright brothers to pursue flight.

**Advanced Propeller Mechanisms and Techniques:**
– Variable pitch propellers maintain optimal angle of attack.
– Feathering systems increase gliding distance and reduce drag.
– Reverse pitch allows for deceleration after landing.
– Counter-rotating propellers balance torque effects.
– Contra-rotating propellers increase efficiency without increasing diameter.