ATR fcom gives best glide speed for obtruction, both engine out as Vmhb0. So this should be the Vx. this is best L/D spd
As Vy is generally more than Vx, Vy will be greater. i guess we'll have to check climb rates at diff speed from fcom.
Another interesting formula is
roc(ft/min) = Pavailable - Preqd/ 33000
hope it helps
