A-320 speed brake versus engine anti ice
 

hi,
the fcom state on the SOP,Descent


SPEEDBRAKES........AS RQRD
In OPEN DES : Use speedbrakes to increase the rate of descent. The pilot may use up to half speedbrakes to maintain the required rate of descent, when engine anti-ice is used.

why is the reason of this statement,I mean, to use of half speedbrake when using engine anti ice?

thanks

....because when you have Eng Anti Ice ON the existing Idle Thrust is increased as the bleed air is taken off. More thrust = reduced descent rate on Open Descent, so use 1/2 speedbrake to counter effect of Eng AI being ON

Very general and simplistic, I'm sure more detailed answers to follow!