A220 Speedbrake Behavior

[Minuteman]

I was on an A220 flight recently and wondered about how the aircraft decided to move the speedbrakes during descent.

At one point, level around 5000 feet, all four panels on the wing popped up a little to slow down briefly. Then about a minute later we started descending and only the middle two panels extended further for braking again while the other two remained down.

That’s a new behavior to me and I was wondering if you know how the A220 decides which spoiler panels should extend when the speedbrake handle is used. Why four one time and two the next time?

 

[Baronman]

With slats or flaps deployed, only the middle two spoiler panels deploy. But they can deflect to a greater degree than when slats and flaps are up but all four spoiler panels deploy.

So my guess is at least the slats were out when you saw the middle two up.