The Hamilton Standard Hydromatic propeller introduced in the 1930s was a significant advance over the counterweight, controllable pitch propeller. Application of oil pressure to both sides of the actuating piston provided increased capacity and the capability of feathering or unfeathering by a single control knob. Reverse pitch permitted shortened landing roll.

With this advance, Hamilton Standard became the primary propeller manufacturer for the Allies during World War II. Virtually the entire front-line inventory, from multiengine bombers to fighter and transport aircraft, as well as a significant majority of RAF aircraft, employed Hydromatic propellers. Hamilton Standard and its three licensees--refrigerator manufacturers Frigidaire and Nash-Kelvinator, and office equipment maker Remington-Rand--produced 530,135 Hydromatic propeller assemblies during the war.