> Bleed holes, Captain Joe explains, “allow for pressure equalization between the space between the panes of the window and the cabin interior. Without these holes, the pressure difference between the cabin and the space between the panes would lead to stress on the window.”
And then to answer the follow-up, the double panes are not for safety in case one breaks. They’re for thermal insulation.
This doesn't refer to the double-paned outer window, the pressure window. It refers to the innermost protective pane, the "scratch pane" that keeps greasy fingers and portruding camera lenses from reaching the two "real" windows. It's the hole in the scratch pane people are asking about
doesnt mean the inside one isnt there to protect the outside one.
> doesnt mean the inside one isnt there to protect the outside one.
The inner pane is typically half the thickness of the outer pane.
So whilst you could argue it cold be seen as a failsafe, I would say its primary purpose remains "double glazing" insulation.
The OAT at 30–40,000ft is very low and there is a lot of combined window area. So the importance of insulation is not to be underestimated. In particular on newer aircraft where efficiency is the name of the game in their design.
The inner pane (isn't it plastic?) is far easier to replace when some annoying kid devices to scratch their tag into it with a nail file.
> The inner pane (isn't it plastic?) is far easier to replace
That's the scratch pane you are referring to.
Yes, it is made of cheap plastic and serves no structural or other purpose other than to protect the real stuff from annoying kids. ;)
Also if it wasn't insulated, the windows might also steam up? Or does the air conditioning make it dry enough that this wouldn't happen. Foggy windows could also affect the pilot's ability to see, I suppose the flight deck windows must also be insulated.
> Or does the air conditioning make it dry enough that this wouldn't happen. Foggy windows could also affect the pilot's ability to see, I suppose the flight deck windows must also be insulated.
Depends on the aircraft but a typical design would connect the space between the panels to an air supply or otherwise a self-contained desiccator system.
Flight deck windows are completely different, typically three layers, two full thickness and one half thickness. All fully heat/chemical strengthened with additional anti-fog, anti-ice and moisture absorption systems built-in. The fact that some of them are sliding (i.e. openable) adds to the design complexity.
> OAT
For the non-aviation folks, OAT means "Outside Air Temperature".
My time in the military has made me hate acronyms with a fury.
that's not what's being discussed. airplanes have a hull window and a passenger cabin window that are universally refered to as a single "double" window- at least amongst the general public.
The inner cabin window is absolutely there to protect the hull window.
Doesn't this just put the stress on the other pane of the window? I don't see how it helps.
EDIT: Oh. It helps because otherwise the bit between the panes would be at a different pressure to both the interior and exterior of the plane. It would work just as well if the bleed hole were on the outside, as long as both panes are equally strong.
This "article" is basically a transcript of a youtuber's explanation. At least they are quoted and not just copied.
I prefer reading articles over watching videos. Videos take forever to get to the point.
> Videos take forever to get to the point.
I feel the same with this article.
This is such a common annoyance on the modern internet. I've recently been playing Minecraft with my kids, with a few mods, and I've been irritated to discover that - unlike when I'd mess around with mods a decade ago - lots of the "documentation" for mods now exists only in video form.
Anyway, I built / slopped out this little wrapper for yt-dlp that I call tuber[1], and it has a feature for grabbing a video's subtitles and summarizing them with Claude, if you've got the CLI. I've found it really handy for those annoying cases where some video seems to promise info I want but I don't want to sit through ten minutes of bullshit.
you could also use openai whisper for transcription. takes longer but beats bad subtitles
yeah, but some people don't want to, or can't watch a video, and prefer reading.
I think their point is why not have an actual source?
The guy who made the video is (was?) a pilot, so I think he's as good a primary source as we would often deem acceptable for something like this.
[deleted]
Yeah, I'd rather read a 2 minute article than have someone stretch the explanation to 10 minutes for ad revenue or the algorithm or whatever the current YouTube enshitrification meta is.
Of possible interest, Science for the Airplane Passenger by Elizabeth Wood
I fly quite a lot and have never seen this? mostly norwegian, SAS easyjet and ryanair. Is it a US thing?
I'll definitely be on the lookout next time I fly though but yeah. Maybe its not every window?
I've always noticed and wondered, so I guess it's easy to overlook but it's there.
Then you overlooked it, every passenger jet of a certain size (say A320 and up) has them
Ryanair and sas definitely have them
The article claims it helps stop condensation, but I have several memories of little ice crystals and/or condensation that originate right at the little hole…
This is extremely obvious and it’s what you think it is.
Most people don’t think along this axis. It’s the same reason why if you asked somebody how a toilet works or the functionality of P-trap (both things a majority have interacted with/seen more frequently than a plane window), they’d probably give you a blank stare.
I guess it is to most people, but others have never given it an iota of thought and some are part of today's lucky 10,000! https://xkcd.com/1053/
Could have been answered with a single sentence instead of a trip down memory lane that nobody wants or needs.
How much easier would it be to design build & maintain aircraft if we did away with (passenger) windows?
Everything gets much easier without windows, but many people feel a sense of security with windows.
I also prefer a flight without get a feeling of a flying can.
It also helps passengers on long flights experience the passage of time as something other than number go up
Is that just a TV with a fancy bezel that plays a 24-hour video? $10K seems a lot to drop on something so mundane.
If this meant more space and bigger seats due to reduced costs of the plane, sign me up.
If history is any indication, it would only mean more passengers in the plane.
so if I block it with my finger from takeoff to cruise I can create a little explosion? Or is the issue the repeated cycles of pressure weakening the material over time?
You can't reach it with your finger, it's in the middle pane.
If you just want an answer to the question
> Bleed holes, Captain Joe explains, “allow for pressure equalization between the space between the panes of the window and the cabin interior. Without these holes, the pressure difference between the cabin and the space between the panes would lead to stress on the window.”
And then to answer the follow-up, the double panes are not for safety in case one breaks. They’re for thermal insulation.
This doesn't refer to the double-paned outer window, the pressure window. It refers to the innermost protective pane, the "scratch pane" that keeps greasy fingers and portruding camera lenses from reaching the two "real" windows. It's the hole in the scratch pane people are asking about
doesnt mean the inside one isnt there to protect the outside one.
> doesnt mean the inside one isnt there to protect the outside one.
The inner pane is typically half the thickness of the outer pane.
So whilst you could argue it cold be seen as a failsafe, I would say its primary purpose remains "double glazing" insulation.
The OAT at 30–40,000ft is very low and there is a lot of combined window area. So the importance of insulation is not to be underestimated. In particular on newer aircraft where efficiency is the name of the game in their design.
The inner pane (isn't it plastic?) is far easier to replace when some annoying kid devices to scratch their tag into it with a nail file.
> The inner pane (isn't it plastic?) is far easier to replace
That's the scratch pane you are referring to.
Yes, it is made of cheap plastic and serves no structural or other purpose other than to protect the real stuff from annoying kids. ;)
Also if it wasn't insulated, the windows might also steam up? Or does the air conditioning make it dry enough that this wouldn't happen. Foggy windows could also affect the pilot's ability to see, I suppose the flight deck windows must also be insulated.
> Or does the air conditioning make it dry enough that this wouldn't happen. Foggy windows could also affect the pilot's ability to see, I suppose the flight deck windows must also be insulated.
Depends on the aircraft but a typical design would connect the space between the panels to an air supply or otherwise a self-contained desiccator system.
Flight deck windows are completely different, typically three layers, two full thickness and one half thickness. All fully heat/chemical strengthened with additional anti-fog, anti-ice and moisture absorption systems built-in. The fact that some of them are sliding (i.e. openable) adds to the design complexity.
> OAT
For the non-aviation folks, OAT means "Outside Air Temperature".
My time in the military has made me hate acronyms with a fury.
https://acronyms-suck.com
that's not what's being discussed. airplanes have a hull window and a passenger cabin window that are universally refered to as a single "double" window- at least amongst the general public.
The inner cabin window is absolutely there to protect the hull window.
Doesn't this just put the stress on the other pane of the window? I don't see how it helps.
EDIT: Oh. It helps because otherwise the bit between the panes would be at a different pressure to both the interior and exterior of the plane. It would work just as well if the bleed hole were on the outside, as long as both panes are equally strong.
This "article" is basically a transcript of a youtuber's explanation. At least they are quoted and not just copied.
I prefer reading articles over watching videos. Videos take forever to get to the point.
> Videos take forever to get to the point.
I feel the same with this article.
This is such a common annoyance on the modern internet. I've recently been playing Minecraft with my kids, with a few mods, and I've been irritated to discover that - unlike when I'd mess around with mods a decade ago - lots of the "documentation" for mods now exists only in video form.
Anyway, I built / slopped out this little wrapper for yt-dlp that I call tuber[1], and it has a feature for grabbing a video's subtitles and summarizing them with Claude, if you've got the CLI. I've found it really handy for those annoying cases where some video seems to promise info I want but I don't want to sit through ten minutes of bullshit.
[1]: https://github.com/epiccoleman/tuber
you could also use openai whisper for transcription. takes longer but beats bad subtitles
yeah, but some people don't want to, or can't watch a video, and prefer reading.
I think their point is why not have an actual source?
The guy who made the video is (was?) a pilot, so I think he's as good a primary source as we would often deem acceptable for something like this.
Yeah, I'd rather read a 2 minute article than have someone stretch the explanation to 10 minutes for ad revenue or the algorithm or whatever the current YouTube enshitrification meta is.
Of possible interest, Science for the Airplane Passenger by Elizabeth Wood
https://archive.org/details/sciencefromyoura00wood
Related: Why there are holes in bicycle rims: https://youtu.be/yppBwvPciBo?t=8m7s
The article on the trio of de Havilland passenger jet crashes from 1950s (linked from the post) is very interesting -
https://www.faa.gov/lessons_learned/transport_airplane/accid...
I fly quite a lot and have never seen this? mostly norwegian, SAS easyjet and ryanair. Is it a US thing?
I'll definitely be on the lookout next time I fly though but yeah. Maybe its not every window?
I've always noticed and wondered, so I guess it's easy to overlook but it's there.
Then you overlooked it, every passenger jet of a certain size (say A320 and up) has them
Ryanair and sas definitely have them
The article claims it helps stop condensation, but I have several memories of little ice crystals and/or condensation that originate right at the little hole…
This is extremely obvious and it’s what you think it is.
Most people don’t think along this axis. It’s the same reason why if you asked somebody how a toilet works or the functionality of P-trap (both things a majority have interacted with/seen more frequently than a plane window), they’d probably give you a blank stare.
I guess it is to most people, but others have never given it an iota of thought and some are part of today's lucky 10,000! https://xkcd.com/1053/
Could have been answered with a single sentence instead of a trip down memory lane that nobody wants or needs.
How much easier would it be to design build & maintain aircraft if we did away with (passenger) windows?
Everything gets much easier without windows, but many people feel a sense of security with windows.
I also prefer a flight without get a feeling of a flying can.
It also helps passengers on long flights experience the passage of time as something other than number go up
another solution: https://www.theliquidview.com/
Is that just a TV with a fancy bezel that plays a 24-hour video? $10K seems a lot to drop on something so mundane.
If this meant more space and bigger seats due to reduced costs of the plane, sign me up.
If history is any indication, it would only mean more passengers in the plane.
so if I block it with my finger from takeoff to cruise I can create a little explosion? Or is the issue the repeated cycles of pressure weakening the material over time?
You can't reach it with your finger, it's in the middle pane.
not with that attitude