NTS vs Autofeather

ASpilot2be

ASpilot2be

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What exactly is the advantage of either one? Is either one more advantageous? The NTS seems like quite an elaborate system.
 
In the C441 that I flew the NTS system would not completely feather the prop. It would take it to about 80% of the way to completely feathered which got rid of most of the drag.

On the 350 I fly know we have auto feather which completely feathers the prop. It does it quicker than you or I could on our best day. I will take the autofeather over the NTS system because it is one less thing that I have to worry about when the crap hits the fan.



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An autofeather system is exactly what it sounds like, it automatically feathers the prop when engine torque output drops below a certain level with the power levels advanced to near full power (example numbers: <400 ftlbs torque with power levers >90% forward). It is used on free turbines because once the prop is feathered, the starter can still motor the engine in order to air-start it if you discover why it shut down and remedy the problem. This is because the prop is not physically attached to the engine and therefore will not slow the engine's acceleration during start up.

A Negative Torque Sensing System (NTS) is exactly what it sounds like. Positive torque = engine driving the prop (normal), Negative torque = engine output so low that the relative wind's windmilling force turns the prop faster than the engine does (power idle, high speed descent or when you lose an engine). The NTS system senses torque and when it sense a negative torque condition (engine failure), it will move the prop TOWARD a feather (more course blade angle = slower prop RPM = less windmilling force from the wind = less negative torque). As a person said above, the NTS system does NOT FULLY Feather the prop. It will slow the prop down to about "Light Off" RPM (example: around 5-10% RPM) because that little residual windmilling motion allows for the MINIMUM drag on that side while still allowing the pilot to perform an air-start.

To air-start a free turbine, you simple...do the same thing as on the ground. In a direct drive turboprop, the prop is spun as the engine accelerates. If the prop is fully feathered, it will be near impossible for the engine to accelerate properly. On the Fairchild Metroliner (SA227) with Garret TPE331 direct drive engines, the engine start button's function changes in the air. A squat switch changes the start button from activating the starter (ground) to running the unfeather pump (air) thus removing the starter from even trying to crank over the engine in the air.
 
That makes a lot of sense. Thank you!

Starting the CASA with the TPE331-10R-511C in the air the air start switch activates the unfeather pump.
 
NTS is more complex and less effective. That's the short version. The long version is it has to be because they put the engine in facing the correct direction, unlike Brand P.
 
Boris Badenov said:
NTS is more complex and less effective. That's the short version. The long version is it has to be because they put the engine in facing the correct direction, unlike Brand P.
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It certainly is complex. Trying to figure this engine out is making my head hurt.
 
Oddly enough though, I enjoyed learning about the Garret more than the Prats because it was more complex and intricate. I do admit though, I had the most difficulty learning the prop control system and the NTS system mainly because of how different it was (and how sorta un-intuitive it seemed as well). Beta Mode vs Normal Mode, the hydraulic reset piston, and the NTS lockout valve... man, what an.... interesting design lol. What helped me out a lot was sneaking a peak at the maintenance dept's training manual (along with talking to the actual mechanic). The diagrams were more detailed as well as the descriptions. If you have one available to you, I highly suggest it, if you are so inclined.
 
Yeah maintenance manuals are great. I don't know why they omit all that detail out of the pilot manuals. It would really help the learning process.
 
Fly Boy Knight said:
Oddly enough though, I enjoyed learning about the Garret more than the Prats because it was more complex and intricate. I do admit though, I had the most difficulty learning the prop control system and the NTS system mainly because of how different it was (and how sorta un-intuitive it seemed as well). Beta Mode vs Normal Mode, the hydraulic reset piston, and the NTS lockout valve... man, what an.... interesting design lol. What helped me out a lot was sneaking a peak at the maintenance dept's training manual (along with talking to the actual mechanic). The diagrams were more detailed as well as the descriptions. If you have one available to you, I highly suggest it, if you are so inclined.
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The Garretts are certainly elaborate engines. I am enjoying learning about them. Luckily a mechanic its teaching our aircraft systems class. Very cool stuff. I am finally getting the hang of prop governor mode versus beta mode.
Cessnaflyer said:
Yeah maintenance manuals are great. I don't know why they omit all that detail out of the pilot manuals. It would really help the learning process.
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I haven't seen the maintenance manuals, but a mechanic its teaching the class which helps.
 
You don't get maintenance manuals because 99% of that stuff is useless knowledge. It works or it doesn't. It feathers or it doesn't. Why is irrelevant. If I have no control over it or it doesn't help me operate the system or try to get it working properly if it isn't, then I don't need to know about it.
 
Rocketman99 said:
You don't get maintenance manuals because 99% of that stuff is useless knowledge. It works or it doesn't. It feathers or it doesn't. Why is irrelevant. If I have no control over it or it doesn't help me operate the system or try to get it working properly if it isn't, then I don't need to know about it.
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Very true! The company wants us to know a bit more about the systems because of where we operate. If they have to fly a mechanic out to the middle of nowhere, it is nice to give the mechanics as much info as we can to avoid multiple trips to get parts.
 
Rocketman99 said:
You don't get maintenance manuals because 99% of that stuff is useless knowledge. It works or it doesn't. It feathers or it doesn't. Why is irrelevant. If I have no control over it or it doesn't help me operate the system or try to get it working properly if it isn't, then I don't need to know about it.
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Not to be mean, but that is the dumbest thing I have heard. You should be very familiar with how your craft operates. You never know when you need the correlative ability to diagnose problems which could only be known when you dive into the manuals and learn more about the systems and how they operate together. Why stop at the bare minimum.
 
Cessnaflyer said:
Not to be mean, but that is the dumbest thing I have heard. You should be very familiar with how your craft operates. You never know when you need the correlative ability to diagnose problems which could only be known when you dive into the manuals and learn more about the systems and how they operate together. Why stop at the bare minimum.
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I agree. But I am having a hard time going really in depth at the beginning. It is overwhelming, so I wish to learn more overtime.
 
It is great knowing both the operation and the maintenance side of things. Of course, keeps me employed and the pilots from having to be too smart... ;)
 
Cessnaflyer said:
Not to be mean, but that is the dumbest thing I have heard. You should be very familiar with how your craft operates. You never know when you need the correlative ability to diagnose problems which could only be known when you dive into the manuals and learn more about the systems and how they operate together. Why stop at the bare minimum.
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Disagree from a 121 perspective. Knowing how your craft operates does not correlate to knowing minutae about systems you have no input or control over. Not to mention, diagnosing problems outside what is in the abnromal or emergency section of the aircraft manual is a surefire way to find yourself called onto the carpet explaining yourself to the chief pilot. Nice to know sometimes for curiosity's sake, yes; relevant to operations, nope. The company didn't hire you to diagnose and fix planes, that's the maintenance department. They don't pay you for it either.

In other types of operations, I can see your perspective. Some of the extra knowledge might be helpful in the cases where you dont have well defined and spelled out procedures when something goes wrong.
 
Yeah I guess I am used to the 91 aspect of it and being possibly stuck somewhere with no help. I guess I will learn 121 here in a few days.
 
Cessnaflyer said:
Yeah maintenance manuals are great. I don't know why they omit all that detail out of the pilot manuals. It would really help the learning process.
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Pilots + non-essential minutia = Earsplitting arguments in ground school and company orals where the check pilot decides to show you how smart he is and how dumb you are.
 
I think if learning the Garrett first, it will be easier. I learned the PT-6 first, making the Garrett hard as I keep trying to compare everything to the PT-6 when you should look at it from a fresh perspective.
 
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