1 00:00:00,160 --> 00:00:03,440 Speaker 1: Audible dot com is the leading provider of downloadable digital 2 00:00:03,480 --> 00:00:07,160 Speaker 1: audio books and spoken word entertainment. Audible has over one 3 00:00:07,200 --> 00:00:10,080 Speaker 1: hundred thousand titles to choose from to be downloaded to 4 00:00:10,119 --> 00:00:13,640 Speaker 1: your iPod or MP three player. Go to audible podcast 5 00:00:13,760 --> 00:00:16,120 Speaker 1: dot com slash brain stuff to get a free audio 6 00:00:16,160 --> 00:00:18,560 Speaker 1: book download of your choice when you sign up today. 7 00:00:19,480 --> 00:00:22,520 Speaker 1: Welcome to brain Stuff from how stuff works dot com 8 00:00:22,520 --> 00:00:33,200 Speaker 1: where smart Happens. Hi Am Marshall Brain with today's question, 9 00:00:33,440 --> 00:00:37,040 Speaker 1: how do they start jet engines? On airplanes? A jet 10 00:00:37,040 --> 00:00:40,920 Speaker 1: engine has two sets of veins that are connected together 11 00:00:41,040 --> 00:00:44,800 Speaker 1: by a shaft. The hot gases produced by the burning 12 00:00:44,880 --> 00:00:48,680 Speaker 1: fuel drive one set of veins in exactly the same 13 00:00:48,760 --> 00:00:52,279 Speaker 1: way that the wind turns a windmill. These veins are 14 00:00:52,320 --> 00:00:54,640 Speaker 1: at the back of the engine and the hot exhaust 15 00:00:54,680 --> 00:00:58,760 Speaker 1: casts are blowing against them to spin them. Those veins 16 00:00:58,800 --> 00:01:01,800 Speaker 1: then connect to a shell aft which goes towards the 17 00:01:01,800 --> 00:01:05,680 Speaker 1: front of the engine to spin the turbans compressor veins, 18 00:01:05,720 --> 00:01:09,960 Speaker 1: so when the exhaust veins are spinning, the compressor veins 19 00:01:10,000 --> 00:01:13,440 Speaker 1: are also spinning and compressing the air that comes into 20 00:01:13,480 --> 00:01:17,760 Speaker 1: the engine. The starting process normally uses an electric motor 21 00:01:18,080 --> 00:01:22,160 Speaker 1: to spin that main turbine shaft. The motor has bolted 22 00:01:22,160 --> 00:01:25,319 Speaker 1: to the outside of the engine, and it uses gears 23 00:01:25,360 --> 00:01:28,640 Speaker 1: and another shaft to connect to that main shaft. The 24 00:01:28,680 --> 00:01:32,720 Speaker 1: electric motor spins the main shaft until there's enough air 25 00:01:32,880 --> 00:01:36,679 Speaker 1: blowing through the compressor and the combustion chamber to light 26 00:01:36,720 --> 00:01:40,560 Speaker 1: the engine. Fuel starts flowing in an igniter similar to 27 00:01:40,600 --> 00:01:44,240 Speaker 1: a spark plug ignites the fuel. Then fuel flow is 28 00:01:44,280 --> 00:01:47,720 Speaker 1: increased to spin the engine up to its normal operating speed. 29 00:01:48,120 --> 00:01:50,440 Speaker 1: If you've ever been at an airport and watched a 30 00:01:50,600 --> 00:01:53,680 Speaker 1: big engine start up on a jet, you know that 31 00:01:53,720 --> 00:01:57,640 Speaker 1: the blades start rotating slowly. You can see them spinning 32 00:01:57,640 --> 00:02:00,559 Speaker 1: at the front of the engine. The electric star motor 33 00:02:00,640 --> 00:02:04,000 Speaker 1: does that. Then you can hear a pop and see 34 00:02:04,040 --> 00:02:06,240 Speaker 1: smoke come out the back of the engine as the 35 00:02:06,280 --> 00:02:09,840 Speaker 1: fuel first starts to ignite. Then the engine spins up 36 00:02:09,840 --> 00:02:14,600 Speaker 1: and starts producing thrust. On smaller turbine engines, especially home 37 00:02:14,680 --> 00:02:17,799 Speaker 1: built models, another way to start the engine is to 38 00:02:17,960 --> 00:02:21,600 Speaker 1: simply blow air through the air intake with a hair 39 00:02:21,720 --> 00:02:25,480 Speaker 1: dryer or a leaf blower. This technique has the same 40 00:02:25,520 --> 00:02:29,120 Speaker 1: effect of getting air moving through the combustion chamber, but 41 00:02:29,200 --> 00:02:32,480 Speaker 1: it doesn't require the complexity or weight of an attached 42 00:02:32,480 --> 00:02:37,600 Speaker 1: starter motor. Besides the starter shaft, most big jet engines 43 00:02:37,680 --> 00:02:42,840 Speaker 1: include another output shaft for driving things like electrical generators, 44 00:02:43,080 --> 00:02:46,440 Speaker 1: air conditioning compressors, and so on needed to operate the 45 00:02:46,480 --> 00:02:49,880 Speaker 1: plane and keep it comfortable. This shaft can connect to 46 00:02:49,919 --> 00:02:53,480 Speaker 1: the main turbine shaft at the same point the starter does, 47 00:02:53,760 --> 00:02:57,360 Speaker 1: or somewhere else on the shaft. Do you have any 48 00:02:57,400 --> 00:03:01,080 Speaker 1: ideas or suggestions for this podcast? If so, please send 49 00:03:01,080 --> 00:03:04,360 Speaker 1: me an email at podcast at how stuff works dot com. 50 00:03:04,480 --> 00:03:06,800 Speaker 1: For more on this and thousands of other topics, go 51 00:03:06,880 --> 00:03:09,639 Speaker 1: to how stuff works dot com and be sure to 52 00:03:09,720 --> 00:03:12,000 Speaker 1: check out the brain stuff blog on the how stuff 53 00:03:12,000 --> 00:03:18,440 Speaker 1: works dot com home page. Streaming TV shows and movies 54 00:03:18,480 --> 00:03:21,160 Speaker 1: directly to your home is a breeze with Netflix. As 55 00:03:21,160 --> 00:03:23,840 Speaker 1: a Netflix member, you can instantly watch TV and movies 56 00:03:23,880 --> 00:03:27,200 Speaker 1: on your PC, mac, mobile device, or television. Get a 57 00:03:27,200 --> 00:03:30,360 Speaker 1: free thirty day trial membership. Go to Netflix dot com 58 00:03:30,400 --> 00:03:31,960 Speaker 1: slash stuff and sign up today.