NRT744
Topic Author
Posts: 13
Joined: Tue Feb 01, 2005 10:15 pm

What's That Thingy Called Next To The Engine?

Wed Nov 19, 2008 5:59 am

It has been bothering me since I first noticed it on a 777.
There's a small slat or a flap on the leading edge of the wing next to the 767/777 engine pylon. I suspect that it's a small Kreger flap just like the ones on the 747, but I'm not sure.
I also noticed them on the 300/310s as well.
Because it's so small, it makes you think why it's even there. Does it make significant "lift" if it's there? or is it there for other purposes?
 
Gatorman96
Posts: 795
Joined: Wed Dec 07, 2005 2:22 am

RE: What's That Thingy Called Next To The Engine?

Wed Nov 19, 2008 6:03 am

Vortex generators....

http://en.wikipedia.org/wiki/Vortex_generator

They also occur on the wings, tails, and even inside engines a la 727

[Edited 2008-11-18 22:14:10]
Cha brro
 
pilotboi
Posts: 711
Joined: Thu Sep 06, 2007 8:16 am

RE: What's That Thingy Called Next To The Engine?

Wed Nov 19, 2008 6:08 am

Do you mean this?


View Large View Medium
Click here for bigger photo!

Photo © Alex G.-Denicourt - Contrails Aviation Photography

 
ACDC8
Posts: 7175
Joined: Thu Mar 10, 2005 6:56 pm

RE: What's That Thingy Called Next To The Engine?

Wed Nov 19, 2008 6:23 am

The little spot right over the pylon or between the pylon and fuselage?
A Grumpy German Is A Sauerkraut
 
OPNLguy
Posts: 11191
Joined: Tue Jun 15, 1999 11:29 am

RE: What's That Thingy Called Next To The Engine?

Wed Nov 19, 2008 6:30 am

This might be a better picture of them...


View Large View Medium
Click here for bigger photo!

Photo © Juan Carlos Guerra - APM



It does indeed look like a mini-Krueger flap, and since it's there, I think one can safely conclude that Boeing thought it necessary for aerodynamic reasons...
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
NRT744
Topic Author
Posts: 13
Joined: Tue Feb 01, 2005 10:15 pm

RE: What's That Thingy Called Next To The Engine?

Wed Nov 19, 2008 6:34 am

Not exactly. It's not on the engine, nor is it the vortex generator (which I know). It extends and retracts along the leading edge. If you look at the photo, you'll notice that there's a small piece of slat or flap next to the engine pylon and it's clearly different from the inner slat. I'm sorry, my question was not clear.

View Large View Medium
Click here for bigger photo!

Photo © Andrew Hunt - AirTeamImages

 
ACDC8
Posts: 7175
Joined: Thu Mar 10, 2005 6:56 pm

RE: What's That Thingy Called Next To The Engine?

Wed Nov 19, 2008 6:38 am

I've never noticed those before, but I would have to agree with OPNLguy, its most likely for aerodynamic purposes.

Would be interesting to learn more about them, such as do they have the same flap/slat settings as the rest of the leading edge or do they just have one setting?
A Grumpy German Is A Sauerkraut
 
NRT744
Topic Author
Posts: 13
Joined: Tue Feb 01, 2005 10:15 pm

RE: What's That Thingy Called Next To The Engine?

Wed Nov 19, 2008 6:48 am

Now that the question is clear, another question pops up. Why wouldn't they extend the inner slat? It would certainly save some weight and help maintenance. Do they have to add extra weight just for a small device as that??
 
ACDC8
Posts: 7175
Joined: Thu Mar 10, 2005 6:56 pm

RE: What's That Thingy Called Next To The Engine?

Wed Nov 19, 2008 6:52 am



Quoting NRT744 (Reply 7):
Why wouldn't they extend the inner slat?

Clearance over the engine cowling I would assume? If the inner slat was extended, it looks like it wouldn't be able to extend out as much due to the proximity of the cowling. Of course, this is just my assumption, I've never flown an aircraft with leading edge slats.
A Grumpy German Is A Sauerkraut
 
NRT744
Topic Author
Posts: 13
Joined: Tue Feb 01, 2005 10:15 pm

RE: What's That Thingy Called Next To The Engine?

Wed Nov 19, 2008 7:02 am

That would make sense only if the "thingy" was shorter than the inner slat. But it appears to me that that small piece extends closer towards the engine.
 
qf744fan
Posts: 36
Joined: Fri Jan 05, 2007 11:58 am

RE: What's That Thingy Called Next To The Engine?

Wed Nov 19, 2008 7:07 am

I guess this is related....
also on the T7, there's a little flap that lifts up on the top of the fuselage, to one side of the tail, during taxi.

It's always down again by the time the aircraft reaches the runway, so i've always imagined it's something to do with the APU. Can anyone be more specific?
 
johnclipper
Posts: 462
Joined: Thu Aug 25, 2005 5:44 am

RE: What's That Thingy Called Next To The Engine?

Wed Nov 19, 2008 7:14 am

That's the APU intake door...
"Flown every aircraft since the Wright Flyer" (guys, if you take this literally, then you need to get a life...)
 
NRT744
Topic Author
Posts: 13
Joined: Tue Feb 01, 2005 10:15 pm

RE: What's That Thingy Called Next To The Engine?

Wed Nov 19, 2008 7:17 am

That would be the APU air intake. It would close when the pilot turns the thing off. Obviously, they won't need it by the time it reaches the runway.
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: What's That Thingy Called Next To The Engine?

Wed Nov 19, 2008 7:28 am



Quoting NRT744 (Thread starter):
Because it's so small, it makes you think why it's even there. Does it make significant "lift" if it's there? or is it there for other purposes?

It's sealing the gap between the flap and the pylon. Without it, you'd have a vortex trailing off the outboard end of the flap and shooting along the edge of the pylon. I don't know any specifics, but that can't be good for drag or airflow in that area. The pylon/wing interface is a very touchy area for aerodynamics and even relatively small changes (e.g. the "blisters" on the A340) can make a big difference.

Tom.
 
NRT744
Topic Author
Posts: 13
Joined: Tue Feb 01, 2005 10:15 pm

RE: What's That Thingy Called Next To The Engine?

Wed Nov 19, 2008 7:43 am



Quoting Tdscanuck (Reply 13):
Without it, you'd have a vortex trailing off the outboard end of the flap and shooting along the edge of the pylon.

Since you mentioned it, I can imagine that it would. Wouldn't the extension of the inner slat solve the problem (and save weight)?
 
ACDC8
Posts: 7175
Joined: Thu Mar 10, 2005 6:56 pm

RE: What's That Thingy Called Next To The Engine?

Wed Nov 19, 2008 7:53 am



Quoting NRT744 (Reply 14):
Wouldn't the extension of the inner slat solve the problem (and save weight)?

Looking at the picture in reply 4, if you would just extend the inner slat, it doesn't look like it would cover enough to reduce the extra vortex/drag as per reply 13. Again, just a guess, but at least I'm trying ....  Wink
A Grumpy German Is A Sauerkraut
 
NRT744
Topic Author
Posts: 13
Joined: Tue Feb 01, 2005 10:15 pm

RE: What's That Thingy Called Next To The Engine?

Wed Nov 19, 2008 7:58 am



Quoting ACDC8 (Reply 15):
Again, just a guess, but at least I'm trying ....  

I appreciate it! That's what makes this post exciting!
 
474218
Posts: 4510
Joined: Mon Oct 10, 2005 12:27 pm

RE: What's That Thingy Called Next To The Engine?

Wed Nov 19, 2008 3:36 pm

Its a "Kruger Flap" that seals off the area between the outboard end of the slat and the pylon.

Extending the slat to provide the same sealing would have required tapering the contour of the slat making manufacture and sealing of the leading edge, with the slat retracted, more difficult.
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: What's That Thingy Called Next To The Engine?

Thu Nov 20, 2008 1:11 am



Quoting NRT744 (Reply 14):
Quoting Tdscanuck (Reply 13):
Without it, you'd have a vortex trailing off the outboard end of the flap and shooting along the edge of the pylon.

Since you mentioned it, I can imagine that it would. Wouldn't the extension of the inner slat solve the problem (and save weight)?

It should solve the problem, and would save weight. However...

Quoting 474218 (Reply 17):
Extending the slat to provide the same sealing would have required tapering the contour of the slat making manufacture and sealing of the leading edge, with the slat retracted, more difficult.

This is definitely true. There's also the fact that, if you get really nice and close to the cowl (which you want to do for maximum effectiveness) you may need to have a clearance panel for the thrust reverser to translate without messing up your leading edge. On the 737NG this is a little spring-loaded flap, but I'm not sure what the 777 does.

I have to assume that somebody did the trade study and figured out that a nice 2D slat with a small Krueger flap was a cheaper (i.e. simpler overall) solution than a fancy contoured slat with some extra moving bits on one corner.

Tom.
 
NRT744
Topic Author
Posts: 13
Joined: Tue Feb 01, 2005 10:15 pm

RE: What's That Thingy Called Next To The Engine?

Thu Nov 20, 2008 9:57 am

I think that solves my problem. Thank you, everyone.
 
Mender
Posts: 247
Joined: Wed Feb 04, 2004 9:36 am

RE: What's That Thingy Called Next To The Engine?

Thu Nov 20, 2008 2:25 pm

I'm not that familiar with the 777 but usually if the slat went all the way to the pylon the translating sleeve of the thrust reverser would hit the slat when the t/rev is deployed. On some aircraft part of this Kruger flap is spring loaded so it will retract when the sleeve is deployed.

I must admit from the picture there look to be enough clearance for the trans sleeve to deploy.

Additionally because the slat doesn't drive out at 90 degrees to the pylon the end of the slat would get closer to the pylon the more it extends. Using a Kruger flap allows the designers to seal this area better throughout the full range of movement of the slats.

Who is online

Users browsing this forum: dennys and 18 guests