waketurbulence
Posts: 1264
Joined: Sun Apr 18, 2004 12:33 pm

Fan Blades In #2 Engine Of 3 Engine A/c?

Sun Aug 08, 2004 7:15 am

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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Klaus
Posts: 20665
Joined: Wed Jul 11, 2001 7:41 am

RE: Fan Blades In #2 Engine Of 3 Engine A/c?

Sun Aug 08, 2004 7:20 am

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
 
OPNLguy
Posts: 11191
Joined: Tue Jun 15, 1999 11:29 am

RE: Fan Blades In #2 Engine Of 3 Engine A/c?

Sun Aug 08, 2004 7:41 am

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...

ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
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Starlionblue
Posts: 17368
Joined: Fri Feb 27, 2004 9:54 pm

RE: Fan Blades In #2 Engine Of 3 Engine A/c?

Mon Aug 09, 2004 2:07 am

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." - John Ringo
 
LineMechQX
Posts: 76
Joined: Wed May 12, 2004 6:02 pm

RE: Fan Blades In #2 Engine Of 3 Engine A/c?

Mon Aug 09, 2004 3:59 pm

- 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.
 
TFJamie
Posts: 117
Joined: Thu Mar 04, 2004 6:16 pm

RE: Fan Blades In #2 Engine Of 3 Engine A/c?

Mon Aug 09, 2004 6:39 pm

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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