prop feathering

braidkid

New Member
During engine failure (single engine airplane), when is it appropriate to feather the prop to low RPM? I know that feathering the prop to low RPM reduces drag and increases gliding distance but I've also read that leaving the prop in high RPM acts like a brake increasing the drag and slows the airplane down.
 

mikek123

Well-Known Member
Well in most single-engine planes the prop won't actually feather, but just go to low RPM. In feather the prop would be aligned with the relative wind and stop turning which won't be the case in a single. I would bring the prop back to low RPM after the restart attempt. If it doesn't restart then I would bring the lever back to reduce drag.
 

CaliforniaSurfer

Well-Known Member
Yeah, I'm not sure of any single engine airplanes that have feathering props. That's not to say that there couldn't be, but usually it is a twin thing to reduce drag on the dead engine side.

Surf
 

mikek123

Well-Known Member
I think the only single-engine aircraft that would have a prop that could feather would be a turboprop.
 

braidkid

New Member
Ok, maybe I'm mistaken....I thought a variable pitch propeller on a complex single engine aircraft
was capable of being "feathered". I guess I have my lingo screwed up.
Anyway, during an engine failure my question is when would you want to set the prop pitch to low RPM and
when would you want to leave it at high RPM?
 

mikek123

Well-Known Member
[ QUOTE ]
Anyway, during an engine failure my question is when would you want to set the prop pitch to low RPM and
when would you want to leave it at high RPM?

[/ QUOTE ]

If you are close to a good landing spot and can definately make it then don't worry about the prop lever, but if you are on the edge of gliding distance to a good field or airport it might help to bring the prop back (assuming you could move the oil to the hub of the prop). So you might want to bring it back almost immediately if you can barely make a field.
 

JJOB757

New Member
Is drag so much a question in a single engine failure. Best glide will bring both parasite and induced drag to a minimum , yet this is purely based on an airspeed and not a configuration. Vmc in a multi engine is purely a directional control issue. Does the configuration in a single matter as long as we are maintaining L/D max airspeed????
 

braidkid

New Member
good question...i wonder which would be more beneficial..
1) establishing best glide with high RPM?
2) establishing best glide with low RPM?
 

ananoman

New Member
Configuration is very important when obtaining best glide in a single engine airplane. If you look in the POH for the aircraft there will usually be a chart for glide distance/altitude in the performance section. It will list the configuration used to obtain the performance listed in the chart. In the Piper Arrow it list the following conditions: Gear Up, Flaps Up, 79 KIAS, Power off, 2750 lbs (Max Weight), No Wind, Prop Full Decrease.

Gear and Flaps are obvious sources of drag and both will reduce glide distance. The prop is another large source of drag. Since most singles cannot be feathered it is best to reduce rpm as much as possible to reduce drag. Weight will not affect total glide distance, but at less than max weight best glide speed will be lower than the 79 KIAS listed in the chart. Use the VSI to find the exact number. Wind will also change best glide speed. If you are going into the wind a faster speed will give the most distance over the ground.

The prop governors of many singles work the opposite of a multi-engine airplane. In most multi's oil pushes the prop to low pitch, high rpm. If oil pressure is lost the prop will feather. In a single the oil pushes the prop to high pitch, low rpm. If oil pressure is lost the prop will go to low pitch, high rpm. So if you loose oil pressure from an oil leak, etc. You will not be able to reduce the prop rpm. If the engine just quits and is windmilling it will develop sufficient oil pressure to reduce prop rpm.
 
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