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Spoiler/Aileron synchronization

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  • Spoiler/Aileron synchronization

    I had a quick question about how pilots determine whether or not to use spoiler synchronization with the ailerons for crosswind landings. I'm guessing this depends on a number of factors such as wind speed/direction, aircraft type, runway length etc.? And do some heavies like the 340 normally land without the need for spoiler synchronization? Of all the times I've experienced crosswind landings with a decent wind speed and wind angle, only the ailerons have been used, the spoilers were not used at all in conjunction with the ailerons. And last question, does the pilot determine (or set) how many of the spoilers will rise (and to which angle) along with the aileron or do the plane's computers determine that? For example, on the 737's sometimes the first outboard spoiler rises, sometimes the first three rise, but to varying angles. On the 320 series, I've seen all outboard spoilers rise along with the aileron and all at the same angle.

  • #2
    Mostly use of roll control spoilers is automatic. After a certain amount a control wheel deflection or roll command the downward wing spoiler panels (those used for roll control) will rise to increase roll rate.

    Generally in a crosswind landing aileron deflection is not that great until runway alignment in the flare. In a sufficient crosswind spoiler rise may occur as the wings are kept level after yawing to align with the runway.

    You can als get spoiler rise during a crosswind takeoff, as can be seen in this shot:
    [photoid=338944]

    Cheers.

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    • #3
      Re:

      Ahh, I see. So does the onboard computer determine how many of the outboard spoilers rise depending on the degree of control column/sidestick input? Or is that more of a mechanical thing?

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      • #4
        It's certainly mechanical on the Boeings I've operated.

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        • #5
          Re:

          Cool. Thanks for the input AJ!

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          • #6
            Mechanical linkage on the Dash. Control cables run from the captain's yoke to spoiler clutches that input the commands to the roll control spoiler actuators. The clutches are there in case a jam occurs. The clutch will disengage allowing the ailerons to continue working until you pull the roll disconnect handle.
            Bite me Airways.....

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            • #7
              Re:

              ^^Interesting info, so basically, the clutches are kind of a built-in redundancy feature right?

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              • #8
                Yep. We can also dump the hydraulic pressure to the spoilers if one gets stuck open.
                Bite me Airways.....

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