TRI DUC ENGLISH - The Invention of Variable-Pitch Propellers TRI DUC ENGLISH Reading Practice: The Invention of Variable-Pitch Propellers Until the late 1920s, airplane propellers were made of a single piece of wood attached at the center to the driveshaft of the engine. The tilt of the propeller, that is, how flatly it faced the wind, was fixed, which meant planes flew as if they had only one gear. If the plane had a fine propeller, it traveled the entire time as if in first gear, working well on takeoff and landing but working inefficiently during sustained flight. If the plane had a thick, coarse propeller, it traveled the entire time as if in high gear, working efficiently during sustained flight, but making takeoffs and landings dangerous and prolonged. This inflexibility meant that commercial uses of such aircraft were limited because the planes could not carry heavy loads either safely or efficiently. In 1922, Wallace Rupert Turnbull patented his latest invention, the Variable-Pitch propeller. His propeller in effect gave airplanes gears. The propeller's blades were separate from each other, attached at the driveshaft in the center, and could be moved independently or together to chop the air at different angles. The propellers could be tilted at takeoff and landing to act as if in first gear, chopping less air with each rotation, and could be tilted when cruising to act as if in high gear, chopping more air with each rotation. With this Variable-Pitch propeller, planes could now take off and land more safely and reliably, carry varying weights, and handle greater variations in wind speed and turbulence. Turnbull was born in New Brunswick in eastern Canada in 1876. He studied mechanical engineering at Cornell, then continued his post-graduate studies in Europe, and returned to work at the Edison labs in New Jersey. In 1902, just one year before the Wright brothers made their historic flight, Turnbull went back home, set up his own lab in a barn, and started running his own aviation experiments. To begin, Turnbull need...