Originally Posted by
Mach E Avelli
Negative torque protection is usually only provided if the pilot does not retard the power lever. If the power lever is retarded to flight idle, most props will go to a high drag state - not beta or reverse, but still enough to cause control problems at low speed.
I have no idea how the ATR powerplant handles this, but this is not true for the Allison 501 installation in the L382. Negative torque protection is a mechanical system which is active through the entire flight range of throttle position. You have to move the throttles over the gate into the Beta range before the linkage in the NTS system is cammed out. If you pull the throttles all the way back to flight idle, (like when you're a little high on descent and trying to make a crossing restriction ... or so I've heard
) you will definately get NTS-ing, and should in a prperly rigged powerplant. In fact this is one of the things which is checked on a functional check flight.
My understanding is that the Metro powerplants are the same way, that you'll get NTS-ing if you pull the throttles back to Flight Idle. I would take that as an indication that some (but not necessarily all ) Garrett installations are similar.