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Old 9th Mar 2015, 12:05
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hawk37
 
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Increased stall AOA with speed brakes extended

In the recent thread "How does altitude affect the aircraft performance", John Tullamarine posted the link below to a Boeing article on AOA. An excellent read, BTW, many thanks

http://http://www.boeing.com/commercial/aeromagazine/aero_12/attack_story.html#figure1

One of the figures, figure 2, shows that if speed brakes are extended, the stalling aoa is actually GREATER than that without speed brakes deployed, shown here

http://http://www.boeing.com/commercial/aeromagazine/aero_12/attack_fig2.html

The text says "Wing-mounted speed brakes or spoilers have the opposite effect. They reduce the lift at a given AOA; they also reduce the maximum lift achievable but, surprisingly, increase the AOA at which stall occurs."

Anyone able to provide an explanation of why a wing stalls at a higher angle of attach with speed brakes deployed?
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