3 ms·

And then to answer the follow-up, the double panes are not for safety in case one breaks. They’re for thermal insulation.

by stouset 10mo ago

butvacuum 10mo ago
doesnt mean the inside one isnt there to protect the outside one.
- traceroute66 10mo ago
  > 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.
  - iso1631 10mo ago
    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.
    - traceroute66 10mo ago
      > 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. ;)
  - HPsquared 10mo ago
    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.
    - traceroute66 10mo ago
      > 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.
  - Sohcahtoa82 10mo ago
    > OAT For the non-aviation folks, OAT means "Outside Air Temperature".
    - mierz00 10mo ago
      My time in the military has made me hate acronyms with a fury. https://acronyms-suck.com https://acronyms-suck.com
  - butvacuum 9mo ago
    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.
Arn_Thor 10mo ago
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

And then to answer the follow-up, the double panes are not for safety in case one breaks. They’re for thermal insulation.

by stouset 10mo ago

And then to answer the follow-up, the double panes are not for safety in case one breaks. They’re for thermal insulation.

butvacuum 10mo ago

doesnt mean the inside one isnt there to protect the outside one.

traceroute66 10mo ago
> 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.
- iso1631 10mo ago
  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.
  - traceroute66 10mo ago
    > 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. ;)
- HPsquared 10mo ago
  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.
  - traceroute66 10mo ago
    > 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.
- Sohcahtoa82 10mo ago
  > OAT For the non-aviation folks, OAT means "Outside Air Temperature".
  - mierz00 10mo ago
    My time in the military has made me hate acronyms with a fury. https://acronyms-suck.com https://acronyms-suck.com
- butvacuum 9mo ago
  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.

Arn_Thor 10mo ago

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