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I noticed this particular portion of the flaps moving differently from rest of the wings. In the attached picture, the middle flap is raised. Is this considered normal?

The landing and takeoff in this flight was normal, but the flaps moving like this made me a little (lot) uncomfortable! I've added a video, as well.

weird flaps

Video on Youtube

Prashant Sinha
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  • Related – Pondlife Mar 24 '17 at 12:49
  • How can this be a duplicate? The other question is answered by explaining why there is a gap in the flaps, and how (and why) this inner "high-speed aileron" (flaperon) is used at high speed when the regular outer aileron is locked. It doesn't at all answer what happens at low speed. – mins Mar 24 '17 at 17:45

1 Answers1

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I believe the engine is mounted in front of that part.

This means that if the part moved along with the rest of the spoiler the jetblast would be deflected down which will create an upward force on the wing. You don't want that while you have full spoiler deployment.

Putting a gap in the spoiler will reduce stress on the full spoiler from the jet blast. This leads to less expensive maintenance as the stresses are reduced mostly to a single panel and its attachment points.

As @Ron points out the flap geometry is such that you can't have the full flaps adjacent to each other without them jamming up when they deflect. Putting an extra panel between them lets it move on top of the other 2 flaps when necessary.

Community
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ratchet freak
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  • It's a Boeing 787-8, if that helps? I found this picture of the plane and it looks like you're right about engine being mounted in front of the part there: https://i.ytimg.com/vi/a2GlO16qiIA/maxresdefault.jpg – Prashant Sinha Mar 24 '17 at 11:19
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    The engine isn't there, but look at the wing geometry. That panel can't lower because it would jam the flaps on either side. So they made it a spoiler – Ron Beyer Mar 24 '17 at 11:23
  • As noted by @Pondlife, that's not a flap but an aileron, that's why it's not moving like the flaps. See http://aviation.stackexchange.com/a/8905/1031 for more details. – Albireo Mar 24 '17 at 14:11
  • @Albireo It is a flaperon. Labeling it as merely an aileron is incorrect, as is labeling it "not a flap". – J W Mar 24 '17 at 14:30
  • All the comments saying it can't lower didn't bother to watch the video attached to the question - which shows the part lower - even below the other parts at some points. The statement that it will jam is shown clearly to be inaccurate. – Greg Taylor May 06 '17 at 10:39
  • It's not so much about jamming as hinging. Since the geometry of the wing has a curve at that point the flap hinges cant extend all the way to the midpoint, you therefor need a small panel in between to break the curve. It would appear that they did not however add both spoiler and flap in the short section though, so when spoiler is deployed the flap flips to the UP position. Not sure why this made you uncomfortable though. – Trevor_G Sep 15 '17 at 16:55