In 1945, preliminary design began on Allison's first turboprop engines. One was the T40 (Allison Model 500), which consisted of two T38 power sections driving co-axial contrarotating propellers ...

The C-130 Hercules military transport plane may not be a sleek jet fighter, but it has been an important tool for the U.S. military for decades.

The C-130 Hercules still uses propeller engines because they suit the plane's usual tasks, which are short-haul, low-speed, and low-altitude journeys.