Originally Posted by
A Squared
Well, I'm not sure what an "ex-albert driver" is, but if we assume that you at one time flew a c-130, we have to also assume that it was a while ago, because your systems knowledge is pretty lacking. Spouting the numerical specs for the prop is not the same as understanding how it works First the prop does not have "stop pins", I don't know where you got that but there's nothing in there that could be remotely described as a "pin". Regardless, the props go into reverse at high airspeeds on almost every flight. That's what you do on landing. It doesn't activate the NTS and it doesn't decouple the prop Besides, even if it *did* decouple, that doesn't prevent the prop from going into reverse. The safety coupling has nothing to do with prop function or control, All the safety coupling does is disconnect the reduction gearbox from the turbine, the prop is still out there in reverse. You may (or may not) recall that there is nothing to prevent you from moving the throttle into the beta range in flight. All you have to do is pick the throttle up over the flight idle gate and move it back into the ground range, and the prop will got to flat pitch, then reverse. It won't NTS because the NTS linkage is cammed out of engagement when you move the throttle into the ground range. Obviously that's a really bad thing to do in flight, so you don't do that. But, here's the thing; if you have a throttle cable break, the effect on the throttle coordinator out on the engine can be essentially the same, the throttle coordinator doesn't 'know" whether the cable broke or the throttle was moved into the ground range, all it knows is something just rotated it into the reverse range, and it does what it does in the reverse range ..whcih is this: it moves linkage to the valve housing whcih causes a prop pitch change into the reverse range and it cams the NTS linkage out of engagement. There you go: One single point of failure, and you have a prop reversing in flight. This isn't just speculation or theorizing this is the actual, real, cause of actual, real inflight prop reverse incidents. It seems odd that you claim to be a C-130 pilot and don't know about this. I thought that was one of those things that all Herc crews knew about. That's why you have a special Engine Shutdown Procedure which is different than a standard ESP when there's a known or suspected throttle or condition lever cable failure. You do remember that from your "albert" days, right? That a throttle cable failure had a special procedure? It's in all the Lockheed manuals, I don't know how you could have missed it. That's the reason, because it can cause the prop to reverse in flight.
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. In other words, it's not so much a negative
thrust system as a negative
torque system. When the prop blades go into beta range (i.e. negative pitch angle) the engine is still producing positive torque, but the prop is producing negative thrust. That will not trigger NTS. NTS is a fail safe in the event the prop goes into pitch lock and then the engine flames out (or the pilot is negligent and allows the RPM to droop). This condition can result in the prop system driving the engine, a potentially very dangerous situation. A small amount of negative torque is permitted to enable a windmill start, but a prop driving the engine can result in drag (negative thrust) well in excess of the equivalent of 6000 lbs negative thrust, much higher negative thrust than the prop can generate in beta range.
Hope this clarified.