cgates66
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Boeing 757-200 Cruise Flap Settings

Fri Aug 05, 2011 7:02 pm

Long time lurker, new poster. I travel frequently and on two recent flights aboard a 757-200 I noticed that during cruise, the inboard flaps remained partially extended - perhaps 3 - 4 inches - for the entire duration of the flight. It occurred to me that this was unusual and I asked my carrier about it; they took my question seriously and said that it was normal for certain flight conditions. I've attached a photo.

Any 757 drivers out there who can elaborate on this? I was very surprised by this, as the wing when fully cleaned up should be optimized for cruise configuration. After landing, the flaps were fully retracted.



[Edited 2011-08-05 12:11:01]

[Edited 2011-08-05 12:11:26]
 
CplKlinger
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RE: Boeing 757-200 Cruise Flap Settings

Fri Aug 05, 2011 7:17 pm

I think that this really isn't that the flaps are not retracted, rather that they aren't fitting as snugly as you think they should. At cruise speeds, flaps are set at 0, and the extension speeds for even the first setting are pretty low (less than 240 knts). The wing is clean, just not the mental pciture you probably had.
 
cgates66
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RE: Boeing 757-200 Cruise Flap Settings

Fri Aug 05, 2011 7:41 pm

That makes sense - although odd that they were completely snug on landing - oh you know what...I wonder if that's just wing flex...that WOULD make sense. Thanks for the time.
 
474218
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RE: Boeing 757-200 Cruise Flap Settings

Fri Aug 05, 2011 8:33 pm

Seems to be normal:


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vikkyvik
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RE: Boeing 757-200 Cruise Flap Settings

Fri Aug 05, 2011 8:36 pm

Quoting cgates66 (Thread starter):

Are you talking about the gap visible there? It looks more like a horizontal gap than a vertical one. Either way, looks normal to me, just based on what I remember seeing out the window (haven't flown on a 757 in quite awhile!).

Also, the inboard section visible may not be a flap, but rather a high-speed aileron. Not sure if that's the case on 757s or not. May just be the flap directly behind the engine, and therefore only being single-slotted.
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XFSUgimpLB41X
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RE: Boeing 757-200 Cruise Flap Settings

Fri Aug 05, 2011 8:48 pm

It's just a gap.

There are no high speed ailerons on the 757.
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dlednicer
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RE: Boeing 757-200 Cruise Flap Settings

Fri Aug 05, 2011 9:27 pm

Several years ago, on a NW 757-300 flight to Hawaii, I noticed that the inboard spoiler I could see out my window was up a little bit while we were in cruise. This struck me as odd, so I wrote a message to this effect on the back of my business card and asked a flight attendant to take the note to the cockpit (my card identifies me as an aero engineer). The pilot came back and took a look. He confirmed that I was right and after looking out the other side, noted that they were deployed equally on both sides. He went back to the cockpit for a while. When he came back, he told me that he thought it was part of the Mach trim system, but he had never seen this before.
 
XFSUgimpLB41X
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RE: Boeing 757-200 Cruise Flap Settings

Fri Aug 05, 2011 10:22 pm

I too noticed that about the spoiler years ago... It's just what it does.  
Chicks dig winglets.
 
474218
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RE: Boeing 757-200 Cruise Flap Settings

Fri Aug 05, 2011 11:42 pm

Quoting XFSUgimpLB41X (Reply 7):
I too noticed that about the spoiler years ago... It's just what it does.

Spoiler float. Very common and not just on the 757.
 
AA737-823
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RE: Boeing 757-200 Cruise Flap Settings

Fri Aug 12, 2011 1:13 pm

Most of these things (aside from spoiler float) are rigging issues. They're considered 'in tolerance,' and once an airframe settles, you're shooting yourself in the foot to try to tweak it out.
Also, each airframe is different- one 737-800 might not fly just like the next 737-800- and so flaps and things can be rigged to correct for a heavy wing, a roll tendency.... all sorts of things.

The gap visible in the original post photo is nowhere near four inches, I can tell you that much. I spend WAY too much time working on the wings to let that go- it's much closer to one inch, slightly below, in fact.
If the gap were four inches, you'd start to see some more odd behaviors, as the flight deck would be having a hard time keeping 'er level!

This gap is typically present after landing as well, wing flex or not. Maybe it was just positioned differently, but it typically doesn't completely disappear.
 
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HAWK21M
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RE: Boeing 757-200 Cruise Flap Settings

Fri Aug 12, 2011 7:37 pm

Quoting XFSUgimpLB41X (Reply 7):

I too noticed that about the spoiler years ago... It's just what it does.

As long as its not contributing to a Trim requirement......Whos complaining.
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