hmmmm...
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What Is This On Every Window?

Mon Dec 17, 2007 1:32 am

I've heard this has something to do with pressure, but in what capacity, I don't know. It seems to me to be a solid plastic cylinder, without any hole in it.

An optimist robs himself of the joy of being pleasantly surprised
 
EMBQA
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RE: What Is This On Every Window?

Mon Dec 17, 2007 1:41 am

It's a vent hole to prevents moisture from forming.... period. It has nothing to do with presurization....but does use it to move the air

[Edited 2007-12-16 17:45:38]
"It's not the size of the dog in the fight, but the size of the fight in the dog"
 
hmmmm...
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RE: What Is This On Every Window?

Mon Dec 17, 2007 1:46 am

If the two panes of glass were sealed, how would moisture get in there? Why make a hole.
An optimist robs himself of the joy of being pleasantly surprised
 
EMBQA
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RE: What Is This On Every Window?

Mon Dec 17, 2007 1:52 am

They first are not glass...carbon poly. Second........ condinsation from the very cold outer pain... and the warm air from the cabin.
"It's not the size of the dog in the fight, but the size of the fight in the dog"
 
hmmmm...
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RE: What Is This On Every Window?

Mon Dec 17, 2007 2:44 am

The plastic cylinder is in between the two outer pressure panes, as you can see in the photo. It is not attached to the inner pane that is inside the cabin. Why would air get in between those two pressure panes?
An optimist robs himself of the joy of being pleasantly surprised
 
EMBQA
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RE: What Is This On Every Window?

Mon Dec 17, 2007 4:06 am

It's a small drill hole in the window panel to prevent moisture from forming between the window and the inner panel. That is all it does.....Moisture forms for the same reason the windows in your car fog up in the winter. The cold air on the outer window reacts to the warm cabin air. The hole allows air to flow between the two pains....... I can't make it any simpler. In your photograph there are actually 3 window panels. The inner panel.. which is non structural and is attached to the wall panel.... the mid pane which is also non-structural... and the actual window.

[Edited 2007-12-16 20:19:00]
"It's not the size of the dog in the fight, but the size of the fight in the dog"
 
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jetmech
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RE: What Is This On Every Window?

Mon Dec 17, 2007 4:22 am



Quoting Hmmmm... (Thread starter):

It may have something to do with the design of the windows. IIRC, there are two panes that are able to withstand the cabin pressure. The hole is drilled into the secondary pane to allow the pressurisation loads to be borne by the outer pane in normal operations. If this pane fails, the middle pane will take the pressurisation loads. There is also a third, inner pane called the scratch pane, which protects the two pressure panes from damage.

Regards, JetMech
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
EMBQA
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RE: What Is This On Every Window?

Mon Dec 17, 2007 4:25 am

Quoting JetMech (Reply 6):

Incorrect... go read your AMM Chapter 56-20, Part 1... D&O Section

[Edited 2007-12-16 20:32:45]
"It's not the size of the dog in the fight, but the size of the fight in the dog"
 
2H4
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RE: What Is This On Every Window?

Mon Dec 17, 2007 4:39 am

Intentionally Left Blank
 
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jetmech
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RE: What Is This On Every Window?

Mon Dec 17, 2007 5:17 am



Quoting EMBQA (Reply 7):

Yes, I have no doubt the hole does act to prevent fogging, but I am also of the opinion that it serves to place the pressurisation loads upon the outer, primary pane. The philosophy with fail-safe designs is to relieve the secondary, back-up feature from loading under during normal operations.

Regards, JetMech
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
WindowSeat
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RE: What Is This On Every Window?

Mon Dec 17, 2007 5:18 am



Quoting EMBQA (Reply 5):
I can't make it any simpler.



Quoting EMBQA (Reply 7):
go read your AMM Chapter 56-20, Part 1... D&O Section

What's with the attitude??

Btw, go read your 5th grade grammar. It's pane and not pain!
I'm all in favour of keeping dangerous weapons out of the hands of fools. Let's start with keyboards.
 
MD11Engineer
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RE: What Is This On Every Window?

Mon Dec 17, 2007 6:57 am



Quoting EMBQA (Reply 5):
the mid pane which is also non-structural

Each of the main window panes can carry the whole cabin pressure if one fails.
And unless you assemble the window units (two panes in a molded rubber seal) in a special room with a 100% dry atmosphere, you'll always have moisture inbetween. The little hole will not disturb if the outer pane breaks, but allows enough air circulation (during pressurisation cycles) to remove moisture from between the panes.

Quoting JetMech (Reply 6):

It may have something to do with the design of the windows. IIRC, there are two panes that are able to withstand the cabin pressure. The hole is drilled into the secondary pane to allow the pressurisation loads to be borne by the outer pane in normal operations. If this pane fails, the middle pane will take the pressurisation loads. There is also a third, inner pane called the scratch pane, which protects the two pressure panes from damage.

Regards, JetMech

 thumbsup 

Jan
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USADreamliner
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RE: What Is This On Every Window?

Mon Dec 17, 2007 4:31 pm



Quoting Hmmmm... (Reply 4):
The plastic cylinder is in between the two outer pressure panes, as you can see in the photo. It is not attached to the inner pane that is inside the cabin. Why would air get in between those two pressure panes?



Quoting Hmmmm... (Reply 2):
If the two panes of glass were sealed, how would moisture get in there? Why make a hole.

AND Irtysh-Avia (Kazakhstan)">IT'S A MAGICAL CYLINDER TO KEEP THE PLANE FLYING, AND Irtysh-Avia (Kazakhstan)">IT'S MADE WITH FAIRY POWDER AND CHRISTMAS WISHES !!!! Happy NOW?
 
nema
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RE: What Is This On Every Window?

Mon Dec 17, 2007 7:03 pm



Quoting WindowSeat (Reply 10):
What's with the attitude??

Btw, go read your 5th grade grammar. It's pane and not pain!

LOL, somewhat hypocritical in an instant.


This thread should have been moved to Tech/Ops Forum!
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jasp25
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RE: What Is This On Every Window?

Mon Dec 17, 2007 7:14 pm



Quoting WindowSeat (Reply 10):
Btw, go read your 5th grade grammar. It's pane and not pain!

And it's condensation, not condinsation. *wink*
*peace*

-jasp
-peace and chicken grease!
 
scrubbsywg
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RE: What Is This On Every Window?

Mon Dec 17, 2007 7:45 pm

as has been mentioned, your eyes can kinda play a trick on you. what you are looking at is indeed a hole, not a cylinder.

Quoting EMBQA (Reply 3):
They first are not glass...carbon poly

what's carbon poly? I assume you mean polycarbonate. Are some airliner windows made of acrylic?
 
Rheinbote
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RE: What Is This On Every Window?

Mon Dec 17, 2007 8:02 pm

Its a resonator hole that helps to shape/attenuate cabin noise and it also keeps exterior noise from being transmitted from the outer panes into the cabin.











 liar  duck 
 
474218
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RE: What Is This On Every Window?

Mon Dec 17, 2007 8:15 pm



Quoting EMBQA (Reply 3):
They first are not glass...carbon poly.



Quoting ScrubbsYWG (Reply 15):
what's carbon poly? I assume you mean polycarbonate. Are some airliner windows made of acrylic?

Actually cabin windows are made from "Stretched Acrylic" conforming to MIL-P-8184.
 
vald
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RE: What Is This On Every Window?

Mon Dec 17, 2007 8:16 pm



Quoting EMBQA (Reply 3):
They first are not glass...carbon poly.

Its polycarbonate
 
474218
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RE: What Is This On Every Window?

Mon Dec 17, 2007 9:57 pm



Quoting Vald (Reply 18):
Its polycarbonate

No. Polycarbonate is what eye glasses are made from and is far to soft for aircraft windows.

Stretched Acrylic is Polymethacylate (PMMA) which is man made synthetic plastic.
 
dakota123
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RE: What Is This On Every Window?

Mon Dec 17, 2007 10:31 pm



Quoting Hmmmm... (Thread starter):
I've heard this has something to do with pressure, but in what capacity, I don't know. It seems to me to be a solid plastic cylinder, without any hole in it.

From Window Anomaly (by Hmmmm... Feb 25 2006 in Tech Ops)

Quoting Hmmmm... (Thread starter):
Every airliner window has a piece, usually cylindrical in shape, about the diameter of a piece of lead in a pencil, at the bottom of the window. You can see it here in this photo. It is always on the inside between the two layers of window.

What I want to know is... why do you keep posing this question?
 duck 
 
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Siren
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RE: What Is This On Every Window?

Mon Dec 17, 2007 11:40 pm



Quoting USADreamliner (Reply 12):
AND Irtysh-Avia (Kazakhstan)">IT'S MADE WITH FAIRY POWDER AND CHRISTMAS WISHES !!!! Happy NOW?

Sir Richard Fairey's cremated remains? Cooool. I didn't think there was that much of him left to go around...
 
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HAWK21M
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RE: What Is This On Every Window?

Tue Dec 18, 2007 7:55 am

The Hole at the Bottom of the middle pane helps Vent the Space between the Outer & middle pane.If there is a stain visible on the Inner surface of the outer pane opposite the Vent hole,its a sign of the Window seal leaking between the Outer & Middle pane.

The Inner pane is not build to take the Pressurisation loads & is mounted on the Sidewall panel.

regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
EMBQA
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RE: What Is This On Every Window?

Wed Dec 19, 2007 9:36 pm

Quoting WindowSeat (Reply 10):

What's with the attitude??

What is with the attitude... look at and read the two links listed above... most noted the second one. Look at who the thread starter is. Now look at who this tread start is. Do you actually think the answer has changed..?

Quoting JetMech (Reply 9):
but I am also of the opinion that it serves to place the pressurisation loads upon the outer, primary pane.

The mid-pane ( the one with the whole in it) is non load supporting. I can take one of those panes and snap it in two with my hands.....and often do when scraping them.

[Edited 2007-12-19 13:43:51]
"It's not the size of the dog in the fight, but the size of the fight in the dog"
 
474218
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RE: What Is This On Every Window?

Wed Dec 19, 2007 10:02 pm



Quoting EMBQA (Reply 23):
The mid-pane ( the one with the whole in it) is non load supporting. I can take one of those panes and snap it in two with my hands.....and often do when scraping them.

There are three separate pieces of plastic: the outer pane is approximately 0.40" thick, the middle pane (with the hole) is approximately 0.25" thick, either of these two panes can contain full cabin pressure. The inner pane (called the scratch pane) is approximately 0.10" thick and carries no pressure as it is actually part of the window reveal.
 
EMBQA
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RE: What Is This On Every Window?

Wed Dec 19, 2007 10:08 pm

Quoting 474218 (Reply 24):

I have never worked with a mid pane that thick......all have been much smaller....but then again, the aircraft were only rated to 30-35K. I HIGHLY doubt those I've seen would support a pressurization load.

[Edited 2007-12-19 14:09:44]
"It's not the size of the dog in the fight, but the size of the fight in the dog"
 
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jetmech
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RE: What Is This On Every Window?

Wed Dec 19, 2007 10:55 pm



Quoting EMBQA (Reply 25):
I HIGHLY doubt those I've seen would support a pressurization load.

Understood EMBQA. My responses in this thread were related to the window designs of the 747 and 767, which I have fitted many times. I was actually under the impression that the mid pane of the 747 was a thick as the outer pane, but it appears that this is not the case as other posters have pointed out.

Nonetheless, I am still of the opinion that the mid pane can carry the full pressurisation loads, and that one of the functions of the hole (besides fog reduction) is as I have written in earlier responses. I would presume that the outer pane is rated to a much higher number of pressurisation cycles than the mid pane.

Regards, JetMech
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
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HAWK21M
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RE: What Is This On Every Window?

Sun Dec 30, 2007 9:25 pm



Quoting EMBQA (Reply 23):
The mid-pane ( the one with the whole in it) is non load supporting.



Quoting JetMech (Reply 26):
Nonetheless, I am still of the opinion that the mid pane can carry the full pressurisation loads,

As I said Earlier Both the Outside & Middle pane Carry the Pressurisation Loads.Eg B737.

regds
MEL
I may not win often, but I damn well never lose!!! ;)

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