Originally Posted by
KenV
A quick note about NTS. I'm not a C-130 driver, but was a P-3 driver which shares a lot of the propulsion systems with the C-130. NTS will NOT be engaged due to the props going into reverse whether in flight or on the ground. NTS is designed to decouple the prop from the engine when the prop drives the engine.
No, NTS does not de-couple the prop from the engine. You are confusing the Safety Coupling with the NTS system. The safety coupling will de-couple the prop from the engine at a negative torque of 6000 inch-lb. The NTS system, senses negative torque being applied to the reduction gearbox, and through a mechanical linkage commands an increase in prop pitch to relive the negative torque. NTS is sort of "autofeather lite" it doesn't actually feather the prop fully, but it drives the pitch toward feather, whcih in a loss of engine power results in a lot less drag, and a lot less negative torque, than if the prop pitch had just gone to the low pitch stop ... whcih is what it would otherwise do in a loss of engine power. The NTS system activates at approximately 1200 inch-lb of negative torque. NTS is not a "failsafe", in fact, it is not uncommon to activate NTS on a descent if the throttles are brought all the way back to the flight idle gate. You'll see the torque-meters fluctuating as the prop pitch is cycled by the NTS.
Anyway, all this is beside the point. It is pretty clear from the AIB report that this was not a case of in-flight prop reversal as we earlier speculated. It was simply a mishandling of an engine failure.