Originally Posted by VNAVSPD
... From what I remember about the commander, you had to lift two detent latches to bring the power levers back past the FLT IDLE STOP. And (may have this wrong) but this is when beta mode takes over?? (ie Power levers control pitch, and overspeed/underspeed govenor controls RPM through fuel metering)
I think one advantage of beta mode on a free turbine engine is that on a throttle slam, beta starts the blades moving toward high (coarse) pitch right away; rather than pouring in fuel, driving the prop overspeed, and then having the prop governor catch up to bring prop speed back down. In normal flight, Beta acts as a variable low-pitch stop in case of a governor failure.