In 1937, Hungarian engineer Gyorgy Jendrassik (1898- 1954) designed and constructed a small turboprop engine. A year later he completed the larger "CS-1" engine, intending to use it on a military bomber, the RMI-1. Unfortunately, the CS-1 ran into combustion problems, keeping it from reaching its projected 1,000 horse-power. The RMI-1's designers were unable to implement an alternative engine before the RMI was annihilated in an air raid by the United States.
In spite of its turbulent birth the turboprop engine enjoyed subsequent success. It is primarily distinguished by its namesake, the turbine-driven propeller at the front. Whereas turbojet and turbofan engines generate thrust only at their rears, the thrust of the turboprop engine is generated mostly by the propeller.
The turboprop engine produces motion like any gas turbine engine. Air enters the engine and is compressed by a spinning, blade-covered cone called an axial compressor. The axial compressor pulls the air into a progressively smaller tube until it reaches a combustion area, where fuel injectors combine fuel and high-pressure air to create a powerful explosion that pushes exhaust out of the engine. As the exhaust leaves, it spins a turbine that rapidly rotates a drive shaft. The rotating drive shaft is then used to spin a gearbox, which in turn powers the plane's propeller.
Turboprop engines are most efficient at speeds below 500 miles (800 km) per hour and so are usually used in smaller, slower-moving aircraft that land and take off frequently. In order to increase efficiency at higher speeds, many modern turboprop engines now use smaller and more numerous blades.
