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I got this device detail of a wing. Those parts are:

  1. 1: wingtip fence, one of the wingtip device beside winglet.
  2. 2 & 3: aileron.
  3. 4: flap track.
  4. 5 & 6: slat.
  5. 7 & 8: flap.
  6. 9 & 10: spoilers.

2 & 3, 5 & 6, 7 & 8, 9 & 10, are part of controls.

In controlling an airplane (if it really has that pairing devices), if we have to use them one after another, which one is said main (primary) and which is secondary?

  • $\begingroup$ This question would benefit from improved grammar. Do you mean to ask what are the primary control surfaces and which are secondary. $\endgroup$ Commented Dec 23, 2018 at 4:55
  • $\begingroup$ Yes my fried. Sometimes I confused to chose the right word. Thank you have informed me that. $\endgroup$ Commented Dec 23, 2018 at 5:07

2 Answers 2


Generally speaking, if a wingtip fence or a winglet is there, it's fixed and can't be moved, so there is no question of it being used before or after the others, although since it's always there I supposed you could say it's used before any of the others. I say generally because I seem to recall hearing recently of an aircraft that has a movable winglet in some manner, but that may just be my imagination.

Insofar as labeling is concerned, control surfaces that are split—an inboard and an outboard section—are usually called just that, as in the inboard ailerons and the outboard ailerons.

Different makes of aircraft may have different orders of usage in some manner, but since your image pretty much matches that of a Boeing 747-100/200 (except they have no wingtip fence or winglet), let's use them for explanation.

The inboard ailerons, are always in use. The outboard ailerons come into use when the aircraft is in slow flight (relatively speaking), in other words, when slats/flaps are deployed. It's automatic, the pilots don't have to select using the outboard ailerons specifically.

The flap tracks (what you see on the image are the "canoes" covering the actual flaps tracks) move when the flaps are deployed. The flaps will usually operate fine even if a canoe leaves the airplane in flight (happened to me once), and as I remember you're allowed to defer replacing at least one of them, but with a performance penalty.

The movement of the slats is connected to the deployment of the flaps. Any flap selection results in the inboard slats being extended. On the 747, the inboard slats extend when the flap selection handle is moved to flaps 1°. When flaps 2° is selected, the outboard slats extend.

The flaps are deployed as called for by the pilots moving the flap handle to select whatever degree of flaps they want. On the 747 there are detents at flaps up, 1°, 2°, 5°, 10°, 20°, 25°, and 30°.

The spoilers/speed brakes (whatever you want to call them—the argument still rages—are deployed by the pilots using a handle, pulling it aft deploys them, and the inboard spoilers always deploy. Whether the outboard spoilers deploy depends on aircraft speed as determined by the flap setting: no flap deployment, no outboard spoiler deployment.

  • $\begingroup$ Thank you sir for the nice explanation. $\endgroup$ Commented Dec 23, 2018 at 6:09

The primary flight controls on a conventional fixed-wing aircraft are the ailerons, elevator and rudder.

Since your question is restricted to the wing, only the ailerons are commonly placed on it. However, on modern aircraft, some of the other surfaces are wired to move together with the ailerons. For example, the spoilers or flaps, which are then called spoilerons or flaperons.

The elevator and rudder can be combined into a single set of surfaces in a V-tail, but this solution is not widespread due to its higher mechanical complexity and weight.

The rest of the surfaces on your image are either the winglets, high-lift devices or spoilers. The flaps and slats are generally deployed at the same time, except in edge cases: the first detent on the flap controls might deploy only the flaps, then the second one would activate the slats as well. This depends on the specific aircraft in question.

Furthermore, on an airliner wing like the one pictured, there would be a bias toward deflecting only the inboard surfaces when flying at high airspeeds, to account for the high dynamic pressure in those conditions.

  • $\begingroup$ Actually I want to ask completely control device in the wing and the empennage, but I worry one or more will say my question is to broad. But if you want to explain them too, I will very welcome. $\endgroup$ Commented Dec 23, 2018 at 5:25
  • $\begingroup$ How about the device with more than one in a wing? Say like the slat there are 3. From the color, seems that green is one (number 5) and the yellow is seen as one device (number 6). Are they utilized at the same time? Or more specific, like aileron, which is used turn the airplane beside rudder. But aileron them self there are two: number 2 and number 3: Are they used at the same time? Or just one after another? Say like aileron number 2 then number 3? $\endgroup$ Commented Dec 23, 2018 at 5:29
  • $\begingroup$ I refined the answer a bit, dunno if its clearer now. $\endgroup$ Commented Dec 23, 2018 at 6:01
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    $\begingroup$ FWIW on 747-100/200 aircraft the first detent on the flap controls extends the inboard slats but not the flaps. $\endgroup$
    – Terry
    Commented Dec 23, 2018 at 6:03
  • $\begingroup$ @AirCraftLover While the rudder can be used to turn the aircraft, that would result in uncoordinated flight. The primarily purpose of the rudder is to counteract the adverse yaw caused by using the ailerons. $\endgroup$
    – Terry
    Commented Dec 23, 2018 at 6:12

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