On Saturday, January 6, 2018 at 1:38:02 AM UTC-7, Andy Blackburn wrote:
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Second, deploying spoilers increases drag so the descent angle needs to increase to keep from bleeding off airspeed. The net effect between loss of lift and increase in drag depends a bit on the glider and the airspeed and g-load, but suffice to say that airspeed and AOA will have additional influences inflicted on them. Not a problem if you fly the airplane properly, but a bunch of rates and angles are going to change when you tug on the spoiler of flap handle.
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Andy Blackburn
9B

This, I believe is the key that people are not considering. The physics of it is such that when the air brakes/spoilers are deployed, they disrupt not only the lift, but increase the drag. As such, if you kept the aircraft in the same attitude, you would increase the AOA and are more likely to stall.

However, if you maintain your airspeed, to do this and deploy the spoilers, you would need to change the attitude of the aircraft into a more nose-down position. This would decrease the AOA, thus compensating for the decreased lift and increased drag, and the net effect would be no significant change to the stall speed, whether you are turning or flying level wings. The AOA remains the same, and IAS and stall speed also remain the same.