Sponsor Message:
Civil Aviation Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
How Do Jet Engines Start Up?  
User currently offlineSJCguy From United States of America, joined Apr 2001, 579 posts, RR: 1
Posted (12 years 7 months 6 days 5 hours ago) and read 32441 times:

While pushing out aircraft and watching them, I see that the captain "spins" the engine, then after it gets going fast enough, it ignites and makes a loud pop, then starts full on. How does this ignition of the engine work? Does the captain ignite the engine or does he turn it on and it ignites itself? What is the line of events going on in the engine as it starts?

SJCguy  Smile

6 replies: All unread, jump to last
 
User currently offlineKFRG From , joined Dec 1969, posts, RR:
Reply 1, posted (12 years 7 months 6 days 5 hours ago) and read 32410 times:

I believe the APU supplies power to the engines to startup. Well, a jet engine is ignited through the ignition of jet fuel. The engines stabilizes at approximately 20-25% N1 (I think that's right)

-Tom


User currently offlineRamper@IAH From United States of America, joined Dec 2001, 240 posts, RR: 1
Reply 2, posted (12 years 7 months 6 days 4 hours ago) and read 32380 times:

It all depends on the engine. Some engines are more automated than others. Here is a typical start sequence for a "classic" jet engine: 1) a start valve is opened to provide bleed air (from an APU, ground power source, or another engine that is running) to an air turbine starter. The air turbine starter is connected to the compressor spool, which turns and compresses the air. The speed of this spool is known as N1. When the N1 reaches a certain speed, ignitors are turned on (usually automatically) and fuel is introduced by the pilot (sometimes automatically). Combustion takes place shortly after this sequence. After combustion, the engine becomes "self sustaining," meaning that the power turbine section can turn the compressor section without the air turbine starter. The engine start sequence is complete when the engine indications are stabilized and the generators are brought on-line. In aircraft such as the ERJ-145, the entire start sequence is automated - it only requires you to turn the start knob...thats it!

User currently offlineJsuen From United States of America, joined Aug 2001, 211 posts, RR: 0
Reply 3, posted (12 years 7 months 6 days 4 hours ago) and read 32359 times:

Actually, the compressor spool speed is known as N2. Also, to expand, the ignitors are similar to the spark plugs in your car.

User currently offlineJsf119 From United States of America, joined Jul 2001, 196 posts, RR: 0
Reply 4, posted (12 years 7 months 6 days 3 hours ago) and read 32337 times:

the compressor is also know as N1 too. N1 refers to the fan and the low pressure compressor which is attached to the low pressure turbine by a shaft. N2 refers to the high pressure turbine and high pressure compressor

User currently offlineYeeha From Australia, joined Apr 2001, 70 posts, RR: 0
Reply 5, posted (12 years 7 months 6 days 2 hours ago) and read 32311 times:

try this site...http://www.howstuffworks.com/turbine.htm

User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 6, posted (12 years 7 months 5 days 20 hours ago) and read 32266 times:

N1, N2, Ng - different names, same thing. It's the gas generator RPM.

Large turbines almost exclusively use an air starter, as described. Smaller turbines can use electrical starters. Sometimes, this is achieved by running the generator 'in reverse'. A less common method are hydraulic starters, where a hydraulically driven engine does the initial cranking. Again, often this is a hydraulic pump going 'in reverse'.

On military engines which have to be startable without depending on external air sources etc, you might see cartridge starters or iso-propyl-nitrate starters, where the combustion gases from IPN in a chamber or a cartridge are sent through a turbine to crank the engine.

Cheers,
Fred



I thought I was doing good trying to avoid those airport hotels... and look at me now.
Top Of Page
Forum Index

This topic is archived and can not be replied to any more.

Printer friendly format

Similar topics:More similar topics...
How Do You Start Up An Airline? posted Thu Jul 20 2006 07:32:44 by TopJet001
How Do By-pass Jet Engines Reverse Thrust Work? posted Thu Jan 3 2002 03:25:29 by RC Pilot
How Do They Fill Up Widebodies On Domestic Routes? posted Tue Aug 1 2006 04:57:12 by BizJet
How Do Engines Get To The Assembly Line? posted Mon Apr 24 2006 18:07:32 by BHXDTW
How Do Airlines Come Up With Flight Numbers? posted Wed Sep 21 2005 17:17:36 by RicardoFG
Wheelchair Bound? How Do They Get Up AirStairs? posted Thu Dec 9 2004 06:24:56 by Flybyguy
How Do They Divide The Gates Of New Terminal Up? posted Mon Nov 8 2004 17:09:12 by 7E72004
Start-Up Airlines: How Is It Done? posted Mon Apr 12 2004 17:48:27 by Aguilo
How Do You Lock Up An Aircraft? posted Thu Jan 15 2004 23:48:21 by BA1978
Why Do Older RB 211 Start Up So Loud posted Sun Aug 10 2003 03:16:23 by 747400sp
How Do Airlines Come Up With Flight Numbers? posted Wed Sep 21 2005 17:17:36 by RicardoFG