How do turboprop engines work?

Dive inside the propulsion system that gets low-speed aircraft off the ground.

Anormal jet engine (often called a turbojet) uses fan blades in order to compress air pulled in at the front, and then adds fuel and ignites it. Some of the exhaust energy is used to keep the compressor fan turning, but most of it is expelled at the rear to produce thrust.

A turboprop engine turns this on its head; almost all of the energy is harnessed to turn the propeller shaft at the front, and only about ten per cent of the thrust comes from the exhaust gas. The propellers are much larger than the diameter of the jet engine, so most of the air they push flows past, rather than through it.

This is more efficient at lower speeds, because the engine only adds fuel to the small proportion of the airflow that generates thrust.

Turboprops are slower than jet engines but cheaper to run. They are mostly used in short-hop commuter planes. A helicopter engine is also a kind of turboprop (called a turboshaft) where the rotor blades are driven through a more complicated transmission system.

 

Click on the image for a closer look

Discover more amazing features in the latest issue of How It Works. It’s available from all good retailers, or you can order it online from the ImagineShop. If you have a tablet or smartphone, you can also download the digital version onto your iOS or Android device. To make sure you never miss an issue of How It Works, make sure you subscribe today!

You may also like:

How do ejector seats work? (Video)

Can EM pulses knock planes out of the sky?

Why do our ears ‘pop’ on planes?