Why is there a HOLE in AIRPLANE windows?

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After take-off and during climb, the outside air pressure is in a constant fall, whilst the air pressure within the cabin is in a constant rise created by the aircraft's bleed and air conditioning system, otherwise you would have trouble breathing during the flight. Due to the big difference between the ambient pressure in the cabin and the low pressure outside, there´s is a lot of physical stress on the cabin hull and especially on the windows.

Now if we take a closer look at the cabin windows you´ll see they are made up out of three separate window panes. One outer and middle pane which share the same window frame and one inner pane.

Now if you look at your windows installed in your home you´ll see they are also made up out of at least two panes of glass, with a transparent gas in between them, acting as a temperature barrier which stops condensation on the inner side of the window.

Same in the airplane but without the special gas in between. Because the air pressure difference and temperature variations are far much higher then in your home, engineers had to come up with and idea to prevent the windows from fogging and freezing up. So they´ve decided to leave an air gap in between the two panes. But air has the physical effect of expanding and shrinking either due to air pressure or temperature changes, which could damage the windows.

See the rest of the video for more information!

[InsaneMetalSoldier]

Your damn videos are awesome, friendly to understand as always. I'm gonna request again a video about Pilot Controlled Runway lights! :) Thank you for your videos!

[AceOfHearts]

Thanks for the cool video. Just a small inaccuracy I spotted... cabin pressure is not rising at all. It is also decreasing. But outside pressure is dropping faster... both pressures drops as we climb. Cabin pressure ceases to drop at maximum cabin alitude then stays constant. No point does cabin pressure rise.

[claudiograf]

Great video series! Just a quick correction about the pressures - the cabin pressure does fall too in climb at a reduced rate of the outside pressure. The typical cabin pressure altitude at cruise is between 6000 and 7000 feet for modern airliners (approx. 830 to 800 hPa). The inner window is not affected by the outside pressure and the tiny hole as you correctly stated is there to allow for air to flow out during the climb and in during the descent to equalise the pressure of the air trapped between the outer and inner windows with the cabin. Btw I'm an atmospheric scientist, not a pilot ;)

[LinescrewCanada]

I just assumed the little hole was placed there so people could do videos about it on Youtube.

[commanderbluy]

I actually learnt about my home windows in this video. Mine are single glass pane. It explains why I get condensation on cold mornings! Thank you Joe!

[Weltbevoelkerung]

Well, the inner pressure is not rising, it's just falling slower than the outside pressure. So the differential pressure rises with the altitude.

[ifly]

Why r they bugs in between the outer window and the inner window?

[tobin]

Your demeanor, delivery, and thoroughness is awesome. I am always so happy when I see you have a new video. Thanks.

[bigbignig-abandoned]

2:22 :Ohhh. :) Last time when I was on an airplane, I was like "Why are these windows made out of plastic??" xD

[XN_pro]

My question: Could a passanger break the window and what would happen if its broken?

[neilburns]

So, a typical window in an airliner is triple-glazed.

The wee hole at the bottom of the window is generally to help with the air pressure inside the aircraft cabin (this where all the passengers sit).

[JonathanLarson-CoolJon]

Wouldn't the inner pane also serve as a thermal barrier between passengers and the middle/outer panes? Since there's no insulating gas between the outer and middle panes, the middle pane would get very cold at cruising altitude. Not only would it be very cold to the touch, but it would also frost-over due to all of the moisture in the cabin air. The cabin air between the middle and inner pane plus the insulating properties of the plastic inner pane protect the passenger from the cold outer panes and also reduce the amount of heat that's lost from the cabin air due to convection.

[CountryAndClassics]

I never noticed this before & did not know about this. Many thanks once again.

[khoshrozalamchowdhury]

Please make a video on how to become a pilot which includes pilot training, joining an airlines and how to do all of the above mentioned things. And also how your career started including your pilot school and airline joining. Cheers..

[gooner]

I knew I'm an aviation nerd so it's one of those facts that I have stored in my head in case someone needs to know.
Great work Captain

[catbalooboy]

I was on a 27 year old Boeing 767 last week and I saw ice forming in between the middle and outer glass. it was like an ice cube. mentioned it to the flight attendant who said it was normal. I have some photos if anyone wants.

[Chikyel]

You're the best in the youtube scenery regarding A320. Really, not ironically.
Thanks for your videos, here's an airsimmer (P3Dv4 + Aerosoft 320 + FSLabs 320 ), I always I learn something.

[BartVideoBlog]

Hi Joe. There is a small error in this video.

After take off the cabin pressure is not rising, but also decreasing. But is it is decreasing much slower than the outside pressure. Why not stabilise the cabin pressure to the same as the ground level? In that case on causing altitude the hull has more differential pressure to deal with. So the hull shook be stronger, which makes the aircraft heavier more costly and it burns more fuel. So the air cabine pressure is also lowered when ascending. making the differential persure a bit lower. This way the weight of the hull can be made thinner, the plain lighter and more economically. 

I am so enjoying your channel :-) It's so much fun learning about aviation in every video. Can you make video about the process of starting the engines. What happens in the engines. Are they started electrical like in a car? Are the started with compressed air? What preparations are needed before start? 

Safe flights and hop to meet you in real live!

[haveyoueverwondered]

Absolutely love this channel Joe! Thanks for sharing your world with us! How did you become a pilot... did you always want to be one throughout school?

[crazygirl_irl]

Hi Captain Joe, I found your channel accidentally(recommended for you) and got addicted by them and I love the simple way of explaining the aviation related topics ;). Can you make a video of how to decode METAR, NOTAM and TAF? :)
Looking forward for next videos,
Echo Delta Yankee Tango Alpha (Edyta)