[1] In the early 1930s, Frank W. Caldwell of Hamilton Standard led a team that developed a variable-pitch propeller, using hydraulic pressure and centrifugal force to change the angle of attack of the blades.In 1968, Hamilton began delivering automatic, electronic systems for control of cabin pressure in aircraft.General Motors' propeller business, which originated with its purchase of Aeroproducts in 1940, was acquired by Hamilton Standard in 1990.Sundstrand brought a long history and portfolio of aerospace products to the newly named company.Hamilton Sundstrand continues to provide aerospace components and systems to most of the world's aircraft manufacturers, including Boeing, Airbus, Bombardier, and Embraer.