Hmmmm... From Canada, joined May 1999, 2089 posts, RR: 5 Posted (7 years 3 months 3 weeks 4 days 14 hours ago) and read 4895 times:
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.
Does anybody know what purpose it serves, or is it an artifact of the manufacturing process?
An optimist robs himself of the joy of being pleasantly surprised
Sammyk From United States of America, joined Oct 1999, 1686 posts, RR: 0 Reply 1, posted (7 years 3 months 3 weeks 4 days 14 hours ago) and read 4867 times:
I always thought it was a spacer but would love to know what it really is if not that.
N600RR From United States of America, joined Feb 2006, 171 posts, RR: 0 Reply 2, posted (7 years 3 months 3 weeks 4 days 14 hours ago) and read 4840 times:
I don't know for certain, but I always thought it had something to do with air pressure equalization between the layers of windows -- either to keep them from bowing, or to prevent them from fogging.
But more importantly, and it's hard to tell from this angle, it looks like a ramper left some safety or eye glasses on the wing...
"And the fluffy white lines that the airplane leaves behind are drifting right in front of the waning of the moon" -Cake
Tekelberry From United States of America, joined May 2003, 1459 posts, RR: 5 Reply 3, posted (7 years 3 months 3 weeks 4 days 13 hours ago) and read 4810 times:
Quoting N600RR (Reply 2): alert But more importantly, and it's hard to tell from this angle, it looks like a ramper left some safety or eye glasses on the wing... wink
Spacecadet From United States of America, joined Sep 2001, 3277 posts, RR: 14 Reply 4, posted (7 years 3 months 3 weeks 4 days 11 hours ago) and read 4695 times:
I'm pretty sure that's basically a hole in one layer of the window so that the air in between can move back and forth as it heats up and cools down. You gotta remember that these planes may be sitting in 100 degree weather on the tarmac, only to hit somewhere around -50 once they're at cruise altitude. You can even feel how cold the window gets on the inside layer.
I suppose I could be wrong about that thing, but that's what I always assumed it was. Without some way for that air to breathe, the inner window would crack. (The outer layer has to be tough enough to withstand pressurization, so I'm sure it's the inner layer that would break.)
I'm tired of being a wanna-be league bowler. I wanna be a league bowler!
QQflyboy From United States of America, joined Oct 2003, 2200 posts, RR: 14 Reply 5, posted (7 years 3 months 3 weeks 4 days 10 hours ago) and read 4658 times:
Those "eyeglasses" on the wing are where the overwing exit ropes are attatched. Most aircraft with overwing exit windows have ropes that extend from the overhead bin or window sil to act as a hand hold during an evacuation.
And I concur the hole(s) in the window is to allow for movement of air.
The views expressed are mine alone and do not necessarily reflect my employer’s views.
MX757 From United States of America, joined Aug 2005, 602 posts, RR: 12 Reply 6, posted (7 years 3 months 3 weeks 4 days 10 hours ago) and read 4620 times:
Quoting N600RR (Reply 2): I don't know for certain, but I always thought it had something to do with air pressure equalization between the layers of windows -- either to keep them from bowing, or to prevent them from fogging.
You are correct about pressure equalization, it's called a breather hole in the maintenance manual. It's located on the bottom of the middle window pane.
Fog and frosting are prevented by means of muti-pane construction with intervening cavities essentially isolated from cabin interior air conditions.
Quoting N600RR (Reply 2): But more importantly, and it's hard to tell from this angle, it looks like a ramper left some safety or eye glasses on the wing.
Was I the only to get your joke?
Funny by the way.
Thanks... I know its not material, but I was starting to wonder. (Think I'll stick with my day job for now.)
Quoting QQflyboy (Reply 5): Those "eyeglasses" on the wing are where the overwing exit ropes are attatched.
Even though my somewhat failed attempt at humor was lame, I appreciate the explanation. Since I am only a mere passenger when I fly, I actually thought it was something used for maintenance purposes.
"And the fluffy white lines that the airplane leaves behind are drifting right in front of the waning of the moon" -Cake
474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9 Reply 8, posted (7 years 3 months 3 weeks 3 days 22 hours ago) and read 4333 times:
Quoting MX757 (Reply 6): You are correct about pressure equalization, it's called a breather hole in the maintenance manual. It's located on the bottom of the middle window pane.
The standard window installation is made up of a rubber seal that holds two window panes made of clear stretched acrylic. The outer pane is 0.40" thick then there is a 0.25" air gap and an inner pane 0.25" thick. The small hole at the bottom on the inner pane equalizes the pressure between the inner and outer pane. Should the outer 0.40" thick outer pane fail the 0.25" inner pane can still hold maximum cabin pressure. The two panes and the rubber seal are held in place with small clips.
EMBQA From United States of America, joined Oct 2003, 9292 posts, RR: 12 Reply 9, posted (7 years 3 months 3 weeks 3 days 21 hours ago) and read 4270 times:
It's a small hole to prevent moisture from building up between the inner and outer structural window.
"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, 2089 posts, RR: 5 Reply 10, posted (7 years 3 months 3 weeks 3 days 16 hours ago) and read 4152 times:
Thanks for the answers guys!
BTW, I had to look really hard to find a window shot that had a window in the shot! I much prefer to see the shot framed by the window. Gives a much nicer impression, like you are in the plane with the photographer.
An optimist robs himself of the joy of being pleasantly surprised
Mir From United States of America, joined Jan 2004, 19813 posts, RR: 56 Reply 11, posted (7 years 3 months 3 weeks 3 days 14 hours ago) and read 4096 times:
Quoting N600RR (Reply 2): But more importantly, and it's hard to tell from this angle, it looks like a ramper left some safety or eye glasses on the wing...
Quoting QQflyboy (Reply 5): Those "eyeglasses" on the wing are where the overwing exit ropes are attatched. Most aircraft with overwing exit windows have ropes that extend from the overhead bin or window sil to act as a hand hold during an evacuation.
I heard that it was the hoist point for the wing. Maybe it's both.
-Mir
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Bri2k1 From United States of America, joined Dec 2004, 988 posts, RR: 4 Reply 12, posted (7 years 3 months 3 weeks 3 days 13 hours ago) and read 4087 times:
Quoting EMBQA (Reply 9): It's a small hole to prevent moisture from building up between the inner and outer structural window.
I don't want to sound like I'm disagreeing with you, but I don't know how a small hole would help. I would think that more moisture would be present on the inside of the cabin than outside during most of the useful life of an airliner, so with the hole there, it would be more likely for it to transit the space between the panes. If the opposite were true, and moisture was more likely to sporadically leak from the outside to the inside, why would it vacate the inter-pane space via the hole? There's almost always going to be higher pressure on the inside than the outside of the airliner.
I personally think the first scenario I described above is most common, since I often see ice crystals forming radially out from the hole in between the two panes. It seems likely that these are formed when warm moisture from the cabin seeps into the space between the panes via the hole and is frozen due to the cold temperature of the outer pane. Am I close?
FLY2HMO From , joined Dec 1969, posts, RR: Reply 13, posted (7 years 3 months 3 weeks 2 days 1 hour ago) and read 3865 times:
Quoting EMBQA (Reply 9): It's a small hole to prevent moisture from building up between the inner and outer structural window
Quoting MX757 (Reply 6): Fog and frosting are prevented by means of muti-pane construction with intervening cavities essentially isolated from cabin interior air conditions.
Uhmm yeah right.....
I took this picture while flying one of AM's newest 73Ws. It also has happened to me in WN's 73Ws.
A319XFW From , joined Dec 1969, posts, RR: Reply 14, posted (7 years 3 months 3 weeks 1 day 23 hours ago) and read 3840 times:
Quoting 474218 (Reply 8): The standard window installation is made up of a rubber seal that holds two window panes made of clear stretched acrylic. The outer pane is 0.40" thick then there is a 0.25" air gap and an inner pane 0.25" thick. The small hole at the bottom on the inner pane equalizes the pressure between the inner and outer pane. Should the outer 0.40" thick outer pane fail the 0.25" inner pane can still hold maximum cabin pressure. The two panes and the rubber seal are held in place with small clips.
I concur with this - that's what I remember from my Aircraft Familiarization course a few years ago
Nonfirm From United States of America, joined Sep 2005, 434 posts, RR: 0 Reply 17, posted (7 years 3 months 3 weeks 1 day 10 hours ago) and read 3694 times:
The window need to be installed with the part number up on the outer pane and the weep hole down on the middle pane if the windows show sings of fogging there is a possible leak and the seal should inspected or replaced.The middle window pane gives the structural fail safe it can hold 1.5 times the normal pressure load.The middle pane is similar in shape to the outer pane but it does not have beveled edges.This is from the ng mm.The inner pane is non structural.
A319XFW From , joined Dec 1969, posts, RR: Reply 19, posted (7 years 3 months 3 weeks 1 day 2 hours ago) and read 3606 times:
Quoting Jush (Reply 18): I don't want to be nitpicking... but well the heck I will.
Easyjet does have the A319 and no A320 whatsoever.
It still is a part of the A319 as well.
Not wanting to nitpick either...
It is also part of the A318 wing, too
That's because the A318, A319 and A320 wings are identical.
Quoting Bri2k1 (Reply 12): don't want to sound like I'm disagreeing with you, but I don't know how a small hole would help.
I just got back after my weekend and dug into the manuals. I looked at a few different aircraft on our server and and found the following information...Taken from the D&O section.
CRJ 700/900:
AMM Part 1, 56-20-00- Page 1
The inner pane is an acrylic plate that molds to the same contour as the fuselage. It has a hole drilled in the bottom half to allow warm air from the passenger compartment to heat the outer pain and prevent condensation
SF340:
AMM Part 1, 56-20-00-Page 1, B-2
The inner pain is made of acrylic and has a small hole in the bottom to allow air flow and prevent moisture build up.
[Edited 2006-02-28 22:38:43]
"It's not the size of the dog in the fight, but the size of the fight in the dog"
Bobster2 From , joined Dec 1969, posts, RR: Reply 21, posted (7 years 3 months 3 weeks 20 hours ago) and read 3531 times:
Here's an idea. Put a little piece of paper up againt the hole and see if the cabin air pressure holds it in place. If the paper falls down, then there is not a significant air flow through the hole, and that would disprove the claim that warm air is flowing out the hole.
I personally think the hole is there to put the full cabin pressure on the outer window pane, which is clearly the primary pane since it is thicker than the inner pane. As others have pointed out, the hole provides pressure equalization, not heat conduction.
2enginesonly From Netherlands, joined Jun 2005, 91 posts, RR: 0 Reply 22, posted (7 years 3 months 3 weeks 19 hours ago) and read 3516 times:
Quoting Bobster2 (Reply 21): Here's an idea. Put a little piece of paper up againt the hole and see if the cabin air pressure holds it in place. If the paper falls down, then there is not a significant air flow through the hole, and that would disprove the claim that warm air is flowing out the hole.
Bobster,
I can tell you right away that the paper will fall off.
When an aircraft climbs, the cabinpressure will get lower than the pressure at groundlevel ( but still higher than outside )....with the piece of paper in place on the hole, the pressure between the 2 panes should remain the same as the groundlevel and will therefore blow the piece of paper away.
The only reason for that hole is to prevent moisure being trapped between the 2 panes.....that's the reason the hole is at the bottom of the pane.
It doesn't mean that condensation won't happen ( humid air in cabin + cold windowpane = condensation on window ) but after the flight it will disappear.
I hope my explanation is satisfactory.
And all this because of a tiny hole in a window
Nonfirm From United States of America, joined Sep 2005, 434 posts, RR: 0 Reply 23, posted (7 years 3 months 3 weeks 19 hours ago) and read 3515 times:
Quoting Bobster2 (Reply 21): I personally think the hole is there to put the full cabin pressure on the outer window pane, which is clearly the primary pane since it is thicker than the inner pane. As others have pointed out, the hole provides pressure equalization, not heat conduction.
From both the 737/MD-80 manual both windows are capable of carrying the full load of pressurization the hole is to help vent moisture so the windows panes do not fog up.
Bri2k1 From United States of America, joined Dec 2004, 988 posts, RR: 4 Reply 24, posted (7 years 3 months 3 weeks 19 hours ago) and read 3509 times:
I believe it now. Who am I to disagree with an AMM excerpt? And, its true they rarely fog up to the point that it impairs visbility. Sometimes the inner pane will fog up if you breathe on it, but the outer one usually stays fog-free.
At least we're concerned about a hole in the plane! It's not like another rant about thrust reversers...
Position and hold
25 Hmmmm...: Thanks for posting that photo. Nothing like that on A.net. But just to clarify, I a not talking about the bullet-shaped hole apparent in your photo. I
26 Bri2k1: I don't think that's a hole. That's frozen moisture on the inner surface of the outer pane, which presumably entered the inner-pane gap via the hole
27 David L: Agreed. The small cylindrical shape is the hole. That moisture pattern has formed directly opposite the hole on the next pane outboard. Where are tho
28 HAWK21M: If you see a stain around that hole.Replace the seal between the Outer & Inner Panes. regds MEL
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From Canada, joined May 1999, 2089 posts, 
From United States of America, joined Oct 1999, 1686 posts, 
But more importantly, and it's hard to tell from this angle, it looks like a ramper left some safety or eye glasses on the wing... 
material, but I was starting to wonder. (Think I'll stick with my day job for now.)
Since I am only a mere passenger 
when I fly, I actually thought it was something used for maintenance purposes.
From Hong Kong, joined Feb 2004, 15904 posts, 
From Germany, joined Apr 2005, 1636 posts, 
From Netherlands, joined Jun 2005, 91 posts, 
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