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Fan Blades In #2 Engine Of 3 Engine A/c?  
User currently offlineWakeTurbulence From United States of America, joined Apr 2004, 1288 posts, RR: 18
Posted (8 years 9 months 2 weeks 2 days 13 hours ago) and read 2427 times:

Can someone explain how the number 2 engine works on a 3 engine aircraft. I've looked at multiple pics of 727's, DC-10's, L1011's and MD-11's. You can see fan blades for the wing engines and I was just wondering how air is compressed for the #2 engine. Also why is the design so different from the L-1011 and 727, both have exhaust near where I would think the APU would be, versus the DC-10 and MD-11 that has exhaust right out of the back of the engine? I searched for a while and couldn't find a post in tech ops to educate myself. Thanks in advance.
-Matt


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5 replies: All unread, jump to last
 
User currently offlineKlaus From Germany, joined Jul 2001, 20845 posts, RR: 55
Reply 1, posted (8 years 9 months 2 weeks 2 days 13 hours ago) and read 2391 times:

The three engines are identical... #2 just has an elongated (and on some models curved) inlet.

More discussion in this thread: Airliners.net Tech Ops: L-1011 Tail Engine Question

User currently offlineOPNLguy From , joined Dec 1969, posts, RR:
Reply 2, posted (8 years 9 months 2 weeks 2 days 12 hours ago) and read 2369 times:

For the 727, see http://home.swipnet.se/~w-65189/transport_aircraft/b727/boeing_727_series.htm

The illustration is a little deceiving to the eyes initially, as it appears that there's an engine installed at the front of the #2 (center) inlet, but closer look shows that it's just the #1 engine...



User currently offlineStarlionblue From Hong Kong, joined Feb 2004, 15868 posts, RR: 66
Reply 3, posted (8 years 9 months 2 weeks 1 day 18 hours ago) and read 2228 times:

Exactly. the engine is always at the ass end of the S-duct (or straight duct for the DC-10/MD-11).

This is for several reasons:
- For the 727 and L-1011, thrust is closer to the centreline means less annoying torque on the airframe means more efficiency.
- The exhaust so hot it would melt the rest of the duct if the engine weren't at the end.
- Ease of maintenance. Any DC-10/MD-11 mech will tech you that engine is waaaaay up there.


There is plenty of space for the APU in front of the engine for the L-1011. The 727 APU (for those ships that have one) is in one of the main gear wells.




"There are no stupid questions, but there are a lot of inquisitive idiots." - from Citadel by John Ringo
User currently offlineLineMechQX From United States of America, joined May 2004, 77 posts, RR: 0
Reply 4, posted (8 years 9 months 2 weeks 1 day 4 hours ago) and read 2133 times:

- The exhaust so hot it would melt the rest of the duct if the engine weren't at the end.
I think we can rule this one out. If we can make combustion chambers and first stage turbines that don't "melt" then I would think this wouldn't be a huge issue. Take a look at a dash-8 exhaust sometime.

User currently offlineTFJamie From Iceland, joined Mar 2004, 120 posts, RR: 0
Reply 5, posted (8 years 9 months 2 weeks 1 day 1 hour ago) and read 2121 times:

But of course it is better to have the duct made from cheaper, lighter materials that melt easily than some of the heavy duty materials that are used in the combustion chambers.

If the thrust went this long way I could imagine that would be a waste of fuel and energy too...

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