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Inboard aileron of a jetliner

The picture I took here is left wing of a jetliner and it shows how the flap works during take off and landing.

In that video is the inboard aileron, and it shows that the inboard aileron is not firmly controlled. It is like it is swinging up and down.

My question is, why does it look like it swings? Is it intended to be so? If yes, why?

Jamiec
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AirCraft Lover
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1 Answers1

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The flaperon points downwards to function as a flap, and moves up/down to induce rolling moments, which may be necessary to keep the wings horizontal when for instance wind gusts or turbulence are attempting to roll the plane.

So what you see is the roll control to maintain level flight, the outboard ailerons move together with the corresponding flaperons at lower airspeeds, which can be seen in the video as well.

Koyovis
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  • First, is its official name flaperon? I searched over the net before I posted this, I got [here] (https://history.nasa.gov/SP-367/chapt2.htm) that its name is inboard aileron. Sorry if I was wrong. – AirCraft Lover Mar 16 '22 at 21:10
  • If we see in 0:54, it began to "swings", just one or two second after it left the ground. Is rolling performed so immediately after it left the ground? – AirCraft Lover Mar 16 '22 at 21:13
  • Maybe it is good to see 0:54 just a second after it left the ground it is already "swings", and 4:14, less than a second before it touch the ground it is still "swings". – AirCraft Lover Mar 16 '22 at 21:22
  • @AirCraftLover A flaperon is an aileron whose "neutral" position is lowered below the normal chord line for low speed flight to provide double duty for roll control and additional lift, so it's accurate to call it a flaperon. They are also called drooping ailerons. But as far as I know, Boeing just calls them inboard ailerons whether they droop with the flaps or not, although in that case flaperon is a more accurate term. – John K Mar 16 '22 at 22:46
  • The movement of the ailerons in landing is to create rolling moments, which compensate for what the side wind gusts are trying to do: roll the aeroplane. The rapid movements are to keep the wings level. All movement is the result of forces (moments when talking about rotations), the ailerons provide rapidly changing opposing moments for whatever the wind is trying to do. – Koyovis Mar 17 '22 at 00:32
  • @JohnK, thank you for your explanation. But there is one question from your explanation: It is used for low speed* flight to provide double duty for roll control and additional lift* control. I bold the low speed as I read here there is mentioned that flaperon is used for high speed control, opposite to your explanation. – AirCraft Lover Mar 17 '22 at 02:48
  • @Koyovis, thank you for your supplement comment. I now understand it that it is intended to be so, it is in control. – AirCraft Lover Mar 17 '22 at 02:51
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    @AirCraftLover They are used for high speed roll control when fully up but moving differentially. Low speed control when drooped and moving differentially. They are used as ailerons in all flight regimes, whereas the outboard ailerons may be idled at high speeds. It's just that when flaps come out, they still work as ailerons, but also droop with the flaps. – John K Mar 17 '22 at 04:23
  • @JohnK, many thanks. Now I understand. – AirCraft Lover Mar 17 '22 at 11:38