Feathering Question...

dans2992

dans2992

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Dans2992
OK, so after getting my ME Commercial a year ago, I suppose I should know this, but I don't, so here goes:

Suppose that you have a piston twin (for example, a Seneca II) in cruise. Leaving all else the same, someone puts one of the prop controls back into full feather.

Does the engine:

1. Continue to run, just beating the flat blade against the air and generating no thrust?

or...

2. Meet so much resistance that it (and the prop) eventually stops.

and, does the answer change if the engine were at idle power when put back into feather...?

Most simulated engine outs are with the fuel cutoff...

Obviously, there is a feather check done prior to takeoff, however the prop is very quickly brought out of feather, not left there (as I imagine it's bad for the engine).
 
It won't make it to feather if you don't reduce the power.
 
It feathers, but as it's doing so, it really tears the hell out of the engine -- see the discussions on why you reduce throttle before reducing RPM when making any large power change. That's why you always pull the throttle back first before feathering, and why you make darn sure you identify before you feather (lest you destroy the only remaining good engine).
 
Oil pressure in a feathering prop pushes the blades to fine pitch. Remove the pressure completely while it's turning and it feathers.
 
dans2992 said:
OK, so after getting my ME Commercial a year ago, I suppose I should know this, but I don't, so here goes:

Suppose that you have a piston twin (for example, a Seneca II) in cruise. Leaving all else the same, someone puts one of the prop controls back into full feather.

Does the engine:

1. Continue to run, just beating the flat blade against the air and generating no thrust?

That is NOT full feather.. That is flat pitch...

or...

2. Meet so much resistance that it (and the prop) eventually stops.

and, does the answer change if the engine were at idle power when put back into feather...?

Most simulated engine outs are with the fuel cutoff...

Obviously, there is a feather check done prior to takeoff, however the prop is very quickly brought out of feather, not left there (as I imagine it's bad for the engine).
Click to expand...

Also keep in mind.. IIRC a Seneca II does not go into FULL feather.. Just course pitch......
 
I'm not planning to do this obviously, but if it were done, the engine would keep running, but under considerable stress then..?

This is purely hypothetical, but I'm questioning my knowledge of systems because this seems like a simple question with no straightforward answer.
 
dans2992 said:
I'm not planning to do this obviously, but if it were done, the engine would keep running, but under considerable stress then..?

This is purely hypothetical, but I'm questioning my knowledge of systems because this seems like a simple question with no straightforward answer.
Click to expand...

If the motor is still running and making oil pressure and it goes into course pitch, then yes, it will be is stress..

Kinda like putting your car in 5th gear while going 10 miles an hour.....
 
I've started a Barron on the ground with a feathered prop and it was a nonevent. Not the same thing but still.
 
N801BH said:
Also keep in mind.. IIRC a Seneca II does not go into FULL feather.. Just course pitch......
Click to expand...


83480f938cfb4922657eef1c09baa87a.jpg


Looks pretty flat to me...?
 
bnt83 said:
I've started a Barron on the ground with a feathered prop and it was a nonevent. Not the same thing but still.
Click to expand...


Was the prop lever forward when you started it? If so, it would promptly unfeather once oil pressure came up wouldn't it?
 
dans2992 said:
Was the prop lever forward when you started it? If so, it would promptly unfeather once oil pressure came up wouldn't it?
Click to expand...

Yes and yes. Took maybe 3 seconds

It blew the prop accumulator line while I was running it and that's how it ended up shutdown just found it feathered after shutdown
 
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bnt83 said:
I've started a Barron on the ground with a feathered prop and it was a nonevent. Not the same thing but still.
Click to expand...

Yep, but the blades were coming out of feather as the engine was starting and oil pressure became available.
 
Henning said:
Yep, but the blades were coming out of feather as the engine was starting and oil pressure became available.
Click to expand...

You are implying that it cranked and cranked before firing. It didn't.

In addition to that there was at least two quarts of oil on the ground from said blown line. The accumulator was depleated.
 
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Ron Levy said:
It feathers, but as it's doing so, it really tears the hell out of the engine -- see the discussions on why you reduce throttle before reducing RPM when making any large power change. That's why you always pull the throttle back first before feathering, and why you make darn sure you identify before you feather (lest you destroy the only remaining good engine).
Click to expand...

I would think it would ping but trash it seems a bit of a stretch since power decreases as RPM does.
 
bnt83 said:
I would think it would ping but trash it seems a bit of a stretch since power decreases as RPM does.
Click to expand...
The pressure rise will happen faster than the power reduction if the throttle is up in normal cruise or higher, and it will wreck the engine.
 
bnt83 said:
You are implying that it cranked and cranked before firing. It didn't.

In addition to that there was at least two quarts of oil on the ground from said blown line. The accumulator was depleated.
Click to expand...

No, it can fire right away, at low speed the resistance is not great, and the blades are already coming in before it makes it up to idle. As soon at it starts turning, it's filling the hub with pressure, and it doesn't take much volume of oil at all.
 
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