Hmmmm... From Canada, joined May 1999, 2088 posts, RR: 5 Posted (5 years 5 months 1 week 1 day 5 hours ago) and read 11037 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
EMBQA From United States of America, joined Oct 2003, 9286 posts, RR: 13 Reply 1, posted (5 years 5 months 1 week 1 day 4 hours ago) and read 11006 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"
EMBQA From United States of America, joined Oct 2003, 9286 posts, RR: 13 Reply 3, posted (5 years 5 months 1 week 1 day 4 hours ago) and read 10940 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"
Hmmmm... From Canada, joined May 1999, 2088 posts, RR: 5 Reply 4, posted (5 years 5 months 1 week 1 day 3 hours ago) and read 10787 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
EMBQA From United States of America, joined Oct 2003, 9286 posts, RR: 13 Reply 5, posted (5 years 5 months 1 week 1 day 2 hours ago) and read 10573 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"
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.
EMBQA From United States of America, joined Oct 2003, 9286 posts, RR: 13 Reply 7, posted (5 years 5 months 1 week 1 day 2 hours ago) and read 10459 times:
2H4 From United States of America, joined Oct 2004, 8950 posts, RR: 62 Reply 8, posted (5 years 5 months 1 week 1 day 2 hours ago) and read 10391 times:
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.
WindowSeat From United States of America, joined Sep 2003, 1307 posts, RR: 59 Reply 10, posted (5 years 5 months 1 week 1 day 1 hour ago) and read 10252 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.
MD11Engineer From Germany, joined Oct 2003, 13336 posts, RR: 64 Reply 11, posted (5 years 5 months 1 week 23 hours ago) and read 10085 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.
USADreamliner From , joined Dec 1969, posts, RR: Reply 12, posted (5 years 5 months 1 week 14 hours ago) and read 6418 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?
Rheinbote From Germany, joined exactly 7 years ago today! , 1956 posts, RR: 52 Reply 16, posted (5 years 5 months 1 week 10 hours ago) and read 3371 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.
Dakota123 From United States of America, joined Aug 2006, 104 posts, RR: 0 Reply 20, posted (5 years 5 months 1 week 8 hours ago) and read 2784 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.
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?
HAWK21M From India, joined Jan 2001, 31201 posts, RR: 58 Reply 22, posted (5 years 5 months 6 days 22 hours ago) and read 2627 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.
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 From United States of America, joined Oct 2005, 6340 posts, RR: 10 Reply 24, posted (5 years 5 months 5 days 8 hours ago) and read 2358 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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