Originally Posted by
Sunfish
is there a ' negative torque switch' like there was in Electra ham standard props?
Good explanation from Ramrod for the PT6A autofeather system.
The PT6A is a free-turbine engine, the compressor turbine and compressor are on a different shaft than the power turbine. The latter driving the reduction gearbox and the the propeller. These two shafts are not connected.
On the other hand, Negative Torque Sensing or NTS system is installed on a single [spline] shaft like the TPE331 engine. Where all engine components (compressor, power turbinne, gearbox & propeller, accessories, etc.) are geared to that one shaft.