Audible dot com is the leading provider of downloadable digital audio books and spoken word entertainment. Audible has over one hundred thousand titles to choose from to be downloaded to your iPod or MP three player. Go to audible podcast dot com slash brain stuff to get a free audio book download of your choice when you sign up today. Welcome to brain Stuff from how stuff works dot com where smart Happens. Hi Am Marshall Brain with today's question,
how do they start jet engines? On airplanes? A jet engine has two sets of veins that are connected together by a shaft. The hot gases produced by the burning fuel drive one set of veins in exactly the same way that the wind turns a windmill. These veins are at the back of the engine and the hot exhaust
casts are blowing against them to spin them. Those veins then connect to a shell aft which goes towards the front of the engine to spin the turbans compressor veins, so when the exhaust veins are spinning, the compressor veins are also spinning and compressing the air that comes into the engine. The starting process normally uses an electric motor to spin that main turbine shaft. The motor has bolted to the outside of the engine, and it uses gears
and another shaft to connect to that main shaft. The electric motor spins the main shaft until there's enough air blowing through the compressor and the combustion chamber to light the engine. Fuel starts flowing in an igniter similar to a spark plug ignites the fuel. Then fuel flow is increased to spin the engine up to its normal operating speed. If you've ever been at an airport and watched a big engine start up on a jet, you know that
the blades start rotating slowly. You can see them spinning at the front of the engine. The electric star motor does that. Then you can hear a pop and see smoke come out the back of the engine as the fuel first starts to ignite. Then the engine spins up and starts producing thrust. On smaller turbine engines, especially home built models, another way to start the engine is to simply blow air through the air intake with a hair
dryer or a leaf blower. This technique has the same effect of getting air moving through the combustion chamber, but it doesn't require the complexity or weight of an attached starter motor. Besides the starter shaft, most big jet engines include another output shaft for driving things like electrical generators, air conditioning compressors, and so on needed to operate the plane and keep it comfortable. This shaft can connect to the main turbine shaft at the same point the starter does,
or somewhere else on the shaft. Do you have any ideas or suggestions for this podcast? If so, please send me an email at podcast at how stuff works dot com. For more on this and thousands of other topics, go to how stuff works dot com and be sure to check out the brain stuff blog on the how stuff works dot com home page. Streaming TV shows and movies directly to your home is a breeze with Netflix. As a Netflix member, you can instantly watch TV and movies
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