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  • Design/structural question

    can someone explain to me what these things are and why some planes have several of them on each wing?


  • #2
    It's a fairing of the flap mechanism. Not a structural item.
    Since each wing typically has two flaps segments, and each segment requires at least two points of attachment with the required mechanisms, hence the several fairings per wing.

    --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
    --- Defend what you say with arguments, not by imposing your credentials ---

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    • #3
      as i was posting my question, i had a premonition you would be the first to answer!

      thanks.

      my comment is that they appear to put an awful lot of drag on the wings. then again, what do i know about aerodynamics?

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      • #4
        Originally posted by TeeVee View Post
        ................my comment is that they appear to put an awful lot of drag on the wings. then again, what do i know about aerodynamics?
        Research is ongoing to use "wing warping" on aircraft to decrease drag and weight (and cost).
        Here is one example:

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        • #5
          Originally posted by TeeVee View Post
          as i was posting my question, i had a premonition you would be the first to answer!

          thanks.

          my comment is that they appear to put an awful lot of drag on the wings. then again, what do i know about aerodynamics?
          They do put drag, of course, but not as much as the exposed flap mechanisms would.

          The airplane is a bag of compromises. For example, if there were no flaps, they'd be a lot more streamlined, not to mention way lighter. The flaps, its mechanisms, power sources, power lines (mostly hydro pipes), controls and sensors weight a real good bunch. Without the flaps (and slats), the airplanes would be able to either: take more fuel and take the same payload farther, take more payload and take it the same distance for the same fuel, or take the same payload and take it the same distance for less quite less fuel.

          But, what runways would be needed to let airplanes take-off and land at speeds 50% faster than current ones? The answer is runways more than twice as long. And not only that: What tires would bear rolling at 250 MPH? And what brakes would be needed to absorb the energy of a landing, not to mention an aborted take-off at V1?

          So you need flaps, that are very expensive in its design, manufacturing, assembly, maintenance, operation (more fuel, less payload), and that take controls, sensors, mechanisms.... and fairings.

          --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
          --- Defend what you say with arguments, not by imposing your credentials ---

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          • #6
            well it would appear to be possible to bury the stuff in the win and relocate at least a portion of the fuel stored in the wings elsewhere. but i have no idea how much room is actually in the wing and how big these devices are. obviously big enough to need these huge devices.

            i know that zero flap is a selling point for some biz jets. maybe it's time for the commercials to do the same?

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            • #7
              No flaps on bigger a/c mean longer runways plus increased approach speeds and more speed needed for lift off. Not the things you want....
              “The only time you have too much fuel is when you’re on fire.”

              Erwin

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              • #8
                Originally posted by TeeVee View Post
                well it would appear to be possible to bury the stuff in the win and relocate at least a portion of the fuel stored in the wings elsewhere. but i have no idea how much room is actually in the wing and how big these devices are. obviously big enough to need these huge devices.
                While size and room is an issue, location is more of an issue.

                Look at this photo:



                That looks to me like a 747-400 landing. Look at those triple-slotted fowler flaps. Figure out where the flaps end when they are retracted (cue: look at the trailing edge of the flapless zones), and realize how far they extend (and I think they are less than fully extended in this photo). Try to imagine to hold that much flap and that far with a mechanism that was fully contained inside the wing. And then realize that all that "empty" room ahead of the flaps is actually occupied by the flaps themselves when they are retracted.

                Doable? Sure. Didn't Boeing think of that? You bet they did. If they decided for the external mechanism faired with those canoes, I'm sure it's because the drawbacks of that solution were not as many or as big as those of the internal solution. Probably the internal solution was so complex / heavy / expensive / maintenance-intensive etc. that its combined cost made the added fuel consumption due to the drag of fairings a moot point (relatively).

                i know that zero flap is a selling point for some biz jets. maybe it's time for the commercials to do the same?
                What???? That's new for me. Care to explain or give an example of a bizjet without flaps?

                --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                --- Defend what you say with arguments, not by imposing your credentials ---

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                • #9
                  Bombardier Global 6000...zero-flap takeoff capability.

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                  • #10
                    Originally posted by TeeVee View Post
                    Bombardier Global 6000...zero-flap takeoff capability.
                    Discover the new class of business jet. The Global 6500 delivers heightened comfort and total performance that is quintessentially Global.


                    "The leading edge slats and trailing edge fowler flaps on the wing aloow Bombardier Global aircraft to take-off and land at lower speeds than other jets"
                    [for example the Concord]

                    "Take-off distance: 6472ft (Sea level, standard pressure and temperature, MTOW)"
                    [I bet that this figure is with take-off flaps well above zero, and it's likely similar to a 737]

                    And...



                    ... Canoes!!! (sorry, I mean flaps mechanism fairings)

                    Capabilty? Maybe.

                    --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                    --- Defend what you say with arguments, not by imposing your credentials ---

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                    • #11
                      check out page 2

                      Global_6000_Backgrounder.pdf

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                      • #12
                        Okay, again: Capability? Yes.

                        However, the flaps are there together with the fairings.

                        If it had no flaps (and no fairings), it would actually have a better no-flaps take-off performance (being able to replace the weight of the flaps its system with more fuel or more payload, or take the same payload farther on less fuel).
                        Now, it would spoil its ability to take-off from shorter runways in conditions more favorable than "Toluca ISA+25".

                        By the way, Toluca airport is 8500ft high and has a 13800ft-long runway (that's more than double what it requires at sea level ISA+0, presumably with flaps) . The reason for no-flaps is not the take-off run itself (the lack of flaps clearly worsens this performance) but for the climb in the event of an engine failure at take-off (past V1). While the flaps reduce the stall speed and hence the take-off and landing speeds and the required runway length, they also add drag so they worsen the climb gradient after the take-off.

                        Side-note 1: Zero flaps doesn't mean zero slats. I bet my sandwich that that take-off "high and hot with zero flaps" is not with zero slats.
                        Side-note 2: There are several airliners that also have the capability to take-off with zero flaps (but with slats) in some high-n-hot conditions. The MD-80 comes to mind. So in this regard, the Global 6000 didn't invent anything new really.
                        Side-note 3: I'd argue that the selling point is not the "zero-flaps" itself, but the good high-n-hot performance which, mind you, is more the result of the engines being flat-rated* than the other things mentioned.

                        * Engines that combine air with fuel (gasoline, diesel, turboprop, jets) tend to loose power as you climb, because the air is less dense and hence less mass of air flows through the engine, less mass of air requires less fuel to keep the right mixture, and less fuel means less energy. So, for example, say that at sea level an engine can deliver 100% of its potential power but at 5000ft only 80% (invented figures). If you limit the engine to deliver only 80% of its potential power (and call that your new 100%), then the engine will be able too keep that new 100% (in fact, 80% of its potential) up to 5000ft, where it will be really maxed-out. That's flat-rating: Put engines that are more powerful than needed (at sea level ISA+0), limit the thrust to what's needed, and you have an engine that will be able to deliver that max allowed power (flat-rated power) as it climbs to some extent.

                        --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                        --- Defend what you say with arguments, not by imposing your credentials ---

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                        • #13
                          ^Flap track fairings or flap guides are necessary for all the reasons pointed out thus far. The only major commercial aircraft I can think of that have had built-in flap guides is the Fokker 70/100, the 737 Classic (the inboard flaps only-they do not have the canoes seen on the outboard flaps; rather they use the supprt of the built-in flap guide you see that juts out from the wing) and the 747SP, which had a very different trailing edge flap system from the other '47 counterparts.

                          As far as no-flap takeoffs go, the F-70 and F-100 are both capable of doing that (experienced a no-flaps takeoff myself in an AA F-100 in '99), as is the Airbus 300-600, where the inboard ailerons droop down for takeoff should the pilot choose to do so, in certain conditions.

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                          • #14
                            Any drag in the Bernoulli effect? Does life come at the expense of drag? I know this drag thing is getting more and more important as fuel gets more and more expensive, but the cost of fuel probably is cheaper than a total redesign of the plane. By tweaking, they have high confidence the next design will fly. Or so it seems to me, a non-engineer.

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                            • #15
                              Originally posted by EconomyClass View Post
                              Any drag in the Bernoulli effect?
                              No.
                              Does life come at the expense of drag?
                              Both life and lift do.

                              --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                              --- Defend what you say with arguments, not by imposing your credentials ---

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