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What Is This On Every Window?  
User currently offlineHmmmm... From Canada, joined May 1999, 2104 posts, RR: 5
Posted (6 years 7 months 1 week 3 days 3 hours ago) and read 11867 times:

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
27 replies: All unread, showing first 25:
 
User currently offlineEMBQA From United States of America, joined Oct 2003, 9364 posts, RR: 11
Reply 1, posted (6 years 7 months 1 week 3 days 3 hours ago) and read 11836 times:

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"
User currently offlineHmmmm... From Canada, joined May 1999, 2104 posts, RR: 5
Reply 2, posted (6 years 7 months 1 week 3 days 3 hours ago) and read 11800 times:

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
User currently offlineEMBQA From United States of America, joined Oct 2003, 9364 posts, RR: 11
Reply 3, posted (6 years 7 months 1 week 3 days 3 hours ago) and read 11770 times:

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"
User currently offlineHmmmm... From Canada, joined May 1999, 2104 posts, RR: 5
Reply 4, posted (6 years 7 months 1 week 3 days 2 hours ago) and read 11617 times:

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
User currently offlineEMBQA From United States of America, joined Oct 2003, 9364 posts, RR: 11
Reply 5, posted (6 years 7 months 1 week 3 days ago) and read 11403 times:

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"
User currently offlineJetMech From Australia, joined Mar 2006, 2684 posts, RR: 53
Reply 6, posted (6 years 7 months 1 week 3 days ago) and read 11308 times:



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.
User currently offlineEMBQA From United States of America, joined Oct 2003, 9364 posts, RR: 11
Reply 7, posted (6 years 7 months 1 week 3 days ago) and read 11289 times:

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"
User currently offline2H4 From United States of America, joined Oct 2004, 8955 posts, RR: 60
Reply 8, posted (6 years 7 months 1 week 3 days ago) and read 11221 times:
AIRLINERS.NET CREW
DATABASE EDITOR



Quoting Hmmmm... (Thread starter):
What Is This On Every Window?

http://www.airliners.net/discussions/tech_ops/read.main/170548

http://www.airliners.net/discussions/tech_ops/read.main/146605

2H4



Intentionally Left Blank
User currently offlineJetMech From Australia, joined Mar 2006, 2684 posts, RR: 53
Reply 9, posted (6 years 7 months 1 week 2 days 23 hours ago) and read 11087 times:



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.
User currently offlineWindowSeat From United States of America, joined Sep 2003, 1311 posts, RR: 57
Reply 10, posted (6 years 7 months 1 week 2 days 23 hours ago) and read 11082 times:



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.
User currently offlineMD11Engineer From Germany, joined Oct 2003, 13967 posts, RR: 63
Reply 11, posted (6 years 7 months 1 week 2 days 22 hours ago) and read 10915 times:



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


User currently offlineUSADreamliner From , joined Dec 1969, posts, RR:
Reply 12, posted (6 years 7 months 1 week 2 days 12 hours ago) and read 7248 times:



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?


User currently offlineNema From United Kingdom, joined Feb 2006, 710 posts, RR: 0
Reply 13, posted (6 years 7 months 1 week 2 days 9 hours ago) and read 5070 times:



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!



There isnt really a dark side to the moon, as a matter of fact its all dark!
User currently offlineJasp25 From United States of America, joined Aug 2007, 615 posts, RR: 2
Reply 14, posted (6 years 7 months 1 week 2 days 9 hours ago) and read 4869 times:



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!
User currently offlineScrubbsYWG From Canada, joined Mar 2007, 1495 posts, RR: 0
Reply 15, posted (6 years 7 months 1 week 2 days 9 hours ago) and read 4454 times:

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?


User currently offlineRheinbote From Germany, joined May 2006, 1968 posts, RR: 52
Reply 16, posted (6 years 7 months 1 week 2 days 9 hours ago) and read 4201 times:

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 


User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 17, posted (6 years 7 months 1 week 2 days 8 hours ago) and read 4056 times:



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.


User currently offlineVald From Ireland, joined Sep 2007, 138 posts, RR: 0
Reply 18, posted (6 years 7 months 1 week 2 days 8 hours ago) and read 4025 times:



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

Its polycarbonate


User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 19, posted (6 years 7 months 1 week 2 days 7 hours ago) and read 3649 times:



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.


User currently offlineDakota123 From United States of America, joined Aug 2006, 116 posts, RR: 0
Reply 20, posted (6 years 7 months 1 week 2 days 6 hours ago) and read 3614 times:



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 


User currently offlineSiren From United States of America, joined Aug 2006, 312 posts, RR: 12
Reply 21, posted (6 years 7 months 1 week 2 days 5 hours ago) and read 3581 times:



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...


User currently offlineHAWK21M From India, joined Jan 2001, 31667 posts, RR: 56
Reply 22, posted (6 years 7 months 1 week 1 day 21 hours ago) and read 3457 times:

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



Think of the brighter side!
User currently offlineEMBQA From United States of America, joined Oct 2003, 9364 posts, RR: 11
Reply 23, posted (6 years 7 months 1 week 7 hours ago) and read 3204 times:

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"
User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 24, posted (6 years 7 months 1 week 7 hours ago) and read 3188 times:



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.


25 EMBQA : 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 do
26 JetMech : 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 u
27 HAWK21M : As I said Earlier Both the Outside & Middle pane Carry the Pressurisation Loads.Eg B737. regds MEL
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