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I have noticed a strange visual artifact over the wing of a Boeing yesterday. You can see two manifestations of the artifact in the pictures below.

  • The first shows it at the front edge of the wing. There were actually many of those, but I only managed to capture one. It looks very similar to a scratch in the window, but moving my head in front of the window didn't move the artifact. So it must have been in a distance somewhere above the wing.
  • The second pictures shows something similar which looked a bit like there was some kind of reflection on the wing, but the sun was on the other side of the plane, so I wasn't sure what caused it. An odd thing was that the stripe moved kind of in sync with the turbulences

Both of those things moved during the flight and were not always on the same position on the wing. Is it possible that those were caused by pressure/density differences of the air or is it just some reflection (or even something totally different)? first second

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    $\begingroup$ What's the little orange thing near the top-left of the 2nd picture? $\endgroup$
    – user2813274
    Commented Jul 1, 2015 at 3:40
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    $\begingroup$ @user2813274 - take a look at this question $\endgroup$
    – FreeMan
    Commented Jul 1, 2015 at 4:20
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    $\begingroup$ Take a look at this too (near the end at 2:30). Same phenomenon at a larger level. $\endgroup$
    – mins
    Commented Aug 16, 2015 at 0:00

2 Answers 2

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That is the visual effect produced by a shockwave.

The air above the wing is accelerated and will reach Mach 1 (the speed of sound) locally.

It is usually best visible when the sun is right behind you (from the viewers perspective, so on the 3 or 9 o'clock position from the aircraft) and high above the horizon.

Here is a video of shockwave on an A320 on youtube (thanks to @mins for finding it).

Thanks for sharing those really nice pictures! I have tried to make some in the past but I couldn't make out the shock effect from all the dirt on the window.

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    $\begingroup$ Wow, this is one of the most interesting answers (and questions) I have seen on this site. Thanks for sharing! And @Lukas_Skywalker, those are some really nice pics :) $\endgroup$
    – flyingfisch
    Commented Jun 30, 2015 at 21:12
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    $\begingroup$ Ah, interesting, thanks for your answer. On a side note, feel free to use those pictures elsewhere (all of you). $\endgroup$
    – Lukas_Skywalker
    Commented Jun 30, 2015 at 22:38
  • $\begingroup$ @DeltaLima does this happen often on an airplane and can it be heard at ground level $\endgroup$
    – Ethan
    Commented Aug 19, 2015 at 2:26
  • $\begingroup$ @Ethan whether it happens depends on the aircraft type, atmospheric conditions, cruise speed and weight of aircraft. But I have seen it often. I don't think you can heard it specifically at ground level. It is part of the total noise of the aircraft. The aircraft itself is travelling below the speed of sound so you don't get this characteristic sonic boom on the ground. $\endgroup$
    – DeltaLima ♦
    Commented Aug 19, 2015 at 7:50
  • $\begingroup$ @DeltaLima When you say "the air above the wing is accelerated and will reach Mach 1 locally", I presume you mean relative to the wing - can you clarify? $\endgroup$
    – Daniele Procida
    Commented Jun 4, 2016 at 18:10
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I saw this shockwave and the shockwave shadowgram a few days ago on a flight from JFK to SFO over a grey wing, and managed to film it with my iPhone. If I understand it correctly it is:

  1. the shadowgram of the shockwave on the surface of the wing (see how it moves around)
  2. later in the video you can see the shockwave itself as looking through the shockwave it distorts the front of the wing (the distortion moves as well, I think depending on where the iPhone focuses).
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    $\begingroup$ Welcome to aviation.SE! While that is a pretty sweet video, its not actually an answer to the question. Please either explain what the video is showing, or leave this answer as a comment on the original question. Note, once you have enough reputation you will be able to comment on any question. $\endgroup$
    – Rhino Driver
    Commented Aug 19, 2015 at 3:33
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    $\begingroup$ Ooops sorry just wanted to share that I was able to capture this weird phenomenon. If I understand it correctly it is 1) the shadow of the shockwave on the surface of the wing, and 2) later in the video you can see the shockwave itself as looking through the shockwave it distorts the front of the wing. Does that make sense? $\endgroup$
    – Huub
    Commented Aug 19, 2015 at 4:54
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    $\begingroup$ You should edit your answer to reflect this comment, and then you'd be well on your way to a good answer. $\endgroup$
    – Rhino Driver
    Commented Aug 19, 2015 at 5:06

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