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From time to time I like to watch a planespotting video and I must say that one tiny detail bothers me a slight bit.

Look at this Boeing plane:

enter image description here

And at this Airbus:

enter image description here

In particular, examine the section directly above the windows, in the middle. Why is it so smooth with most Boeing planes, and why does it have this crease in many Airbus planes (including the A380, but I think excluding the A350)?

It reminds me of playing with 3D modelling software long ago. I found it difficult to get these curves perfectly smooth - but surely Airbus designers have more skill than I do! So what is the real reason?

Credit: I have taken these images from a YouTube video.

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It is not about Boeing versus Airbus, but rather about old versus new.

Your representative image for Airbus is an A320, whose technological competitor by Boeing is the 777. Juxtaposing the two, we find that the feature in question is present on both aircraft:

A320 versus 777 Image Sources: Boeing 777 versus Airbus A320

Likewise, the technological competitor of the 787 is the A350 (and maybe the A220) - all three of which have a smooth nose section.

Airbus A350, Boeing 787 and Airbus A220 Image Sources: Airbus A350, Boeing 787 and Airbus A220

Camille Goudeseune's answer explains correctly the reason for this feature on older aircraft.

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The pinched-nose airplane has its (flat) frontmost windshield panels almost touching and raked back, which forces the vertical crease. The corresponding panels on the other airplane are farther apart, nearly coplanar, and may be curved as well, so the space between them can have a larger radius of curvature.

The reasons behind those design choices quickly get complicated. But for a start, flat windows are cheaper to design and build and have less optical distortion. G3 curvature will be pretty far down on the list, compared to cars and kitchen appliances.

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    $\begingroup$ Excellent reference to G curvature $\endgroup$
    – Fattie
    Commented Mar 19 at 14:19
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I think you're comparing a 787 in to top to an A319 in the bottom.

The 787 is unusually smooth in that area. It is a composite airframe, which allows some additional freedom to use curvature. You might want to compare to a broader selection of aircraft.

I am not positive, but I think they may have used curved glass on the 787 -- but only a simple curve (one direction). However, the A319 you show clearly uses flat glass.

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  • $\begingroup$ "It is a composite airframe, which allows some additional freedom to use curvature" -- This is true, but there are plenty of aircraft constructed with traditional materials that do have a smooth nose section. See: C919 and A220 $\endgroup$
    – Aditya Sharma
    Commented Mar 19 at 7:39
  • $\begingroup$ IMO it's not clear that composites are "easier to curve". Completely free-form 3D surfaces are really really hard (in terms of everything from design to simulation to indeed manufacture). I'm not sure it's particularly harder, the literal manufacturing, with traditional materials V. composites. I dunno. $\endgroup$
    – Fattie
    Commented Mar 19 at 14:21
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    $\begingroup$ Sheet metal can be easily bent in simple curves without stretching or shrinking the metal. In order to make compound curves, you must deform the metal. This isn't a huge obstacle on an industrial scale where you can make appropriate tooling. So for these aircraft it probably isn't very important. For homebuilt experimental aircraft, forming metal to compound curves by hand for one-off parts is very difficult. It is much easier to carve a mold and lay up composites over that mold. $\endgroup$
    – Rob McDonald
    Commented Mar 19 at 15:17
  • $\begingroup$ @RobMcDonald more precisely, forming aircraft-suitable metals to compound curves by hand is difficult. Doing it in copper, brass or certain types of steel is actually fairly straightforward, but those would be to weak and/or heavy for a plane. $\endgroup$
    – leftaroundabout
    Commented Mar 21 at 16:44
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Building upon this question and the relevant answers, it might have been not only a technical reason (aerodynamics or bird strike resistance) but also a simpler aesthetic/corporate reason in order to help distinguish an Airbus back in the '70s when Airbus was born and started to compete against Boeing, McDonnell Douglas and Lockheed.

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  • $\begingroup$ Huh! Could well be. $\endgroup$
    – Fattie
    Commented Mar 19 at 14:22

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