Author Topic: Feathering the prop (Read 1628 times)

dtango · « **on:** July 05, 2001, 04:18:00 PM »

I've been performing some engine off glide tests to determine drag on AH aircraft. I've noticed that after I shut the engine off my prop continues to spin which adds thrust and throws off my glide tests.

I notice that I can reduce the RPM with engine off and that appears to help but the prop never completely feathers. The RPM indicator still shows the shaft spinning. It actually even increases as I glide at higher speeds.

Is there a way to totally feather the prop in normal flight without having someone to shoot out your engine or running out of gas?

[ 07-05-2001: Message edited by: dtango ]

Seeker · « **Reply #1 on:** July 05, 2001, 04:58:00 PM »

When you say RPM, you do mean RPM don't you, and not manifold pressure?

I'm no expert, but it goes like this:

The throttle controls how much air the engine can draw (manifold pressure); and this governs motor power output.

The Keypad +/- keys control prop pitch, and therefore shaft RPM, and this governs how engine power is applied.

I don't recall ever reducing RPM (prop pitch) enough to bring the prop to a standstill even when gliding engine off (when it stops on a dead motor, it's because the motor has siezed), but I do agree with your observations that it can make a considerable difference to the glide slope.

dtango · « **Reply #2 on:** July 05, 2001, 05:13:00 PM »

Yes I do mean controlling the prop pitch to reduce RPM and not manifold pressure. Didn't know if there was some way to feather the prop totally so I could remove that from the equation. Otherwise I'm not sure how to account for the amount of thrust that the spinning prop is still producing.

Staga · « **Reply #3 on:** July 05, 2001, 05:29:00 PM »

I guess only twin-engine fighters and bombers usually got system which allowed prop feathering ?

Edit: P-47 with Curtiss Electric prop could feather it and even brake with reversed thrust in landing and in divebombing in test flights.

[ 07-05-2001: Message edited by: Staga ]

ispar · « **Reply #4 on:** July 05, 2001, 05:34:00 PM »

Staga is correct. Virtually all single engine fighters do not have a control for feathering a prop. The reasoning behind it is that if the engine dies, you are going to want to leave the plane as soon as possible, rather than try to glide for any distance. Ditchings were generally performed only when the fighter near a friendly base or too low for the pilot to bail out.

Thrawn · « **Reply #5 on:** July 05, 2001, 05:43:00 PM »

Quote

Originally posted by dtango:
I've noticed that after I shut the engine off my prop continues to spin which adds thrust and throws off my glide tests.

I notice that I can reduce the RPM with engine off and that appears to help but the prop never completely feathers. The RPM indicator still shows the shaft spinning. It actually even increases as I glide at higher speeds.
[ 07-05-2001: Message edited by: dtango ]

The prop isn't producing thrust if the engine is off. It's producing a whole bunch of drag. The air hitting the prop is turning it, like a windmill. Hence it turns faster as you glide faster.

[ 07-05-2001: Message edited by: Thrawn ]

Staga · « **Reply #6 on:** July 05, 2001, 05:47:00 PM »

btw here's a pic for this topic:

This plane is using reversed thrust in landing in airshow (220kb).

SFRT - Frenchy · « **Reply #7 on:** July 05, 2001, 06:02:00 PM »

Even a constant speed prop will stop when the engine quit. Shut off your engine, if u keep your gliding fast enought, the prop will still be wind milling. If you can slow down the plane enought, the prop will stop.

In constant speed prop, pulling the lever all the way will definatly help gliding but will not always stop the prop rotation.

Duckwing6 · « **Reply #8 on:** July 06, 2001, 01:51:00 AM »

Kewl Pic Staga ... but that's a Turbo Prop Cresco...

I know hardly any piston single that havs a full feather prop...

Pepe · « **Reply #9 on:** July 06, 2001, 05:45:00 AM »

Staga, as far as I can see on the background of the pic, I think they are using our Mindanao terrain, aren't they?

Cheers,

Pepe

Jigster · « **Reply #10 on:** July 06, 2001, 11:03:00 AM »

Call me crazy, but I'd just use the wheel brakes and skip the whole process of trying-to-flare-with-zero-visability-near-a-crowd-thanks-to-a-reversable-prop-and-oil-injector and all that.

AKDejaVu · « **Reply #11 on:** July 06, 2001, 11:06:00 AM »

blank screan for general news.. just inducing a redraw.

Pay no attention.

LePaul · « **Reply #12 on:** July 06, 2001, 11:28:00 AM »

My question is this, since I fly Lancs and B-17s a lot....when the engines fail/die, do the props automatically feather?

Westy MOL · « **Reply #13 on:** July 06, 2001, 12:06:00 PM »

lol Staga. I though that was a screen shot from "IL2" of an aircraft firing it's nose guns

Westy

Tilt · « **Reply #14 on:** July 06, 2001, 02:33:00 PM »

Quote

Originally posted by dtango:
I've noticed that after I shut the engine off my prop continues to spin which adds thrust and throws off my glide tests.

[ 07-05-2001: Message edited by: dtango ]

My props stop when I switch the engine off.

Tilt