Newbie Question 4 - Can't feather prop!

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nworthin
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Newbie Question 4 - Can't feather prop!

Post by nworthin »

A really big deal is made during sales demos about how feathering the prop is as easy a flipping a switch.

But, it appears there are a least a few scenarios where you would not be able to feather the prop at all.

Page 7-33 of the AFM states that "Feathering is only possible at propeller speeds above 1300 RPM".

Are there situations where RPM would drop below this RPM making it impossible to obtain optimal single engine performance?

What about operations at very low airspeeds? Or, if the gear box turns into a mass of locked up metal? Are these realistic concerns?
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Re: Newbie Question 4 - Can't feather prop!

Post by Karl »

The prop works in much the same way as any other light twin so no more of a concern than on other GA twins.
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Boatguy
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Re: Newbie Question 4 - Can't feather prop!

Post by Boatguy »

If it's an engine failure, then I would think you'll shut it down and it will automatically feather when shut down.
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Re: Newbie Question 4 - Can't feather prop!

Post by photoSteveZ »

nworthin wrote: Thu Jul 07, 2022 3:02 am A really big deal is made during sales demos about how feathering the prop is as easy a flipping a switch.

But, it appears there are a least a few scenarios where you would not be able to feather the prop at all.

Page 7-33 of the AFM states that "Feathering is only possible at propeller speeds above 1300 RPM".

Are there situations where RPM would drop below this RPM making it impossible to obtain optimal single engine performance?

What about operations at very low airspeeds? Or, if the gear box turns into a mass of locked up metal? Are these realistic concerns?
I’ve had the props feather at engine shutdown on the ramp a couple of times. Once was at Leadville, where the ECUs prevented the engines from idling below 13% at the 10,000’ field elevation; the other time was in front of my hangar when I failed to ensure that both of the power levers were pulled back to the idle stops. In the latter case the engine was at only low single-digit power load, but the rpm was high enough to prevent the latches from engaging. I can’t imagine that any in-flight situation short of a complete engine seizure would give you a low enough prop rpm to engage the latches that prevent the springs from feathering the blades when you turn off the engine master.

By the way, if you let the accumulator pressure bleed off it takes three people, one to a blade, to unfeather the prop blades against those springs.
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Re: Newbie Question 4 - Can't feather prop!

Post by juanla@aol.com »

Please get with a qualified MEI and get some time flying single engine. You need to study and understand VMC and don't believe everything that the POH said. There are some many variables and factors to restart those engines and different techniques. Memorize all V speeds and settings.
Juan Asturias MEI, CFII, ATP
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Re: Newbie Question 4 - Can't feather prop!

Post by nworthin »

Boatguy wrote: Fri Jul 08, 2022 3:56 pm If it's an engine failure, then I would think you'll shut it down and it will automatically feather when shut down.
This is the standard case and I'm comfortable this will work properly. The edge case is probably only where the gear box "instantaneously" froze causing the hub to completely stop spinning. Very unlikely (I hope!).
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Re: Newbie Question 4 - Can't feather prop!

Post by nworthin »

Karl wrote: Fri Jul 08, 2022 5:19 am The prop works in much the same way as any other light twin so no more of a concern than on other GA twins.
Ok, but the rest of the power train is very different. Only a few piston twins are geared. None are compression engined except Diamond. I'm not aware of any that are full FADEC.

When I got my multi ticket years ago, after what I learned during that process, I said I would never, ever, fly an "antique" piston twin. For many years, I happily flew and fly single engine pistons, SE turboprops and twin jets.

The premise of the Diamond Jet-A twin line is they "retain the benefits of a twin and eliminate the risks". If they are only "just as good" as other twins, I would reconsider my purchase decision.
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Re: Newbie Question 4 - Can't feather prop!

Post by Karl »

nworthin wrote: Sat Jul 09, 2022 7:49 pm
Boatguy wrote: Fri Jul 08, 2022 3:56 pm If it's an engine failure, then I would think you'll shut it down and it will automatically feather when shut down.
This is the standard case and I'm comfortable this will work properly. The edge case is probably only where the gear box "instantaneously" froze causing the hub to completely stop spinning. Very unlikely (I hope!).
In that event, there is little need to feather it anyway.
We feather a prop to stop it from rotating in the airflow and creating drag.
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Re: Newbie Question 4 - Can't feather prop!

Post by ememic99 »

Karl wrote: Mon Jul 11, 2022 5:13 am
nworthin wrote: Sat Jul 09, 2022 7:49 pm
Boatguy wrote: Fri Jul 08, 2022 3:56 pm If it's an engine failure, then I would think you'll shut it down and it will automatically feather when shut down.
This is the standard case and I'm comfortable this will work properly. The edge case is probably only where the gear box "instantaneously" froze causing the hub to completely stop spinning. Very unlikely (I hope!).
In that event, there is little need to feather it anyway.
We feather a prop to stop it from rotating in the airflow and creating drag.
Non-feathered blades create more drag even when prop is not rotating.
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Karl
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Re: Newbie Question 4 - Can't feather prop!

Post by Karl »

ememic99 wrote: Mon Jul 11, 2022 5:19 am
Karl wrote: Mon Jul 11, 2022 5:13 am
nworthin wrote: Sat Jul 09, 2022 7:49 pm
This is the standard case and I'm comfortable this will work properly. The edge case is probably only where the gear box "instantaneously" froze causing the hub to completely stop spinning. Very unlikely (I hope!).
In that event, there is little need to feather it anyway.
We feather a prop to stop it from rotating in the airflow and creating drag.
Non-feathered blades create more drag even when prop is not rotating.
Of course, it creates some drag. But if it was a significant amount we would have feathering props on single-engined planes.
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