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With the default X-Plane 11 737 I can use the the spoilers switch just at lower center of panel to control the speed at which the speed brakes deploy on touchdown. There are options 1, 2, 3 and Max. Max would be for shortest runways and/or higher touchdown speeds. Most times 2 is enough. The speed brakes can also be armed at the left of the center console with the mouse dragging on the speedbrake lever, to the armed position. Keys can also be assigned. The default keys already assigned are 1 and 2. 2 to increment up a notch and 1 to increment down. As for automatically deploy I only have experience with the 737 for this. Other default aircraft may have something similar.
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