Feathering Props???

[Fozzer]

During a high altitude cruise.
I have an idea that if engine has that has stopped firing because of fuel starvage, or ignition failure, a windmilling propeller on a piston Twin/Multi caused by air passing through the blades, creates more drag than an engine which has been purposely seized/brought to a stand still (by starving it of oil, etc).

A single engine failure on a Twin during take off leaves very little time (none) to gain control* before aiming for the ground...Brown flight suit time... ...!


Paul... 8-)

* the magic, instant prop feather button... ...?

[Hagar]

That's all very well Paul but I'm still trying to figure out how you would go about deliberately seizing up a failed engine.

I tried feathering a prop on the FS9 Baron. Voila!

[Brett_Henderson]

Does the .air file model feathering ?  As in, can you see a yaw difference between feathered and not, engine off ?

(gonna go try it myself    :)     )

[DaveSims]

I believe on the default FS9 baron, the props always look feathered when shut down.

[Brett_Henderson]

I mean, aerodynamic modeling. Felt yaw, reduced airspeed.

[Fozzer]

The trouble with a failed engine is that the oil pump supply to the nose of the CS propeller also looses pressure, so unless the design automatically puts the prop into the feathered position, the propeller will remain at the angle is was in when the engine stopped...and may introduce excessive drag ...!

I suppose it all depends upon how sophisticated the design of your particular CS prop is on your aircraft.. ...!

Paul....Crawling inside the wing to saw through the oil pipe feeding my failed engine... :-?....LOL...!

P'S. I notice my trusty Spell Checker keeps changing my propellor into a propeller... ...!

[Hagar]

The trouble with a failed engine is that the oil pump supply to the nose of the CS propeller also loses pressure, so unless the design automatically puts the prop into the feathered position, the propeller will remain at the angle is was in when the engine stopped...and may introduce excessive drag ...!

I suppose it all depends upon how sophisticated the design of your particular CS prop is on your aircraft.. ...!

Paul....Crawling inside the wing to saw through the oil pipe feeding my failed engine... :-?....LOL...!

At one time I used to overhaul the unfeathering accumulators used on the majority of GA aircraft with CS props.http://www.americanpropeller.com/MTSPECS.htm

An unfeathering accumulator directly connected to the propeller governor is available otionally for Feathering Propellers. This feature enables unfeathering the propeller without a running engine. An unfeathering accumulator with compatible governors can also be installed in aerobatic airplanes, in order to prevent a RPM drop during special aerobatic maneuvers. This unfeathering accumulator maintains the oil supply of the propeller for 5-10 sec., when the governor becomes short of oil supplied by the engine.

P'S. I notice my trusty Spell Checker keeps changing my propellor into a propeller... ...!

There's a good reason for that. Propeller is the correct spelling.

PS. http://www.mccauley.textron.com/prop/prop-tech/pg04feather.html

[Fozzer]

Many thanks for the link, Doug...>>>>

http://www.americanpropeller.com/MTSPECS.htm

Seriously interesting reading on various CS/VP propellor....... propeller types... ...!

(Saved in my Engineering Folder)..!

Paul...Motorcycling at a Constant Speed?.... ....NAH!.... ...!

[Brett_Henderson]

OK.. for the record, it's modeled quite realistically (to a guy with less than a dozen R/L multi-engine hours..  lol )

Level cruise 25/25 and leaned is about 180kias.

I used the auto-pilot for consistency. After pulling the mixture on the non-critical (right) engine (and going to full power on the good engine), the airspeed falls off as expected... the auto-pilot starts compensating for the yaw/pitch and if you do not pull the dead engine prop to full coarse... it just keeps getting worse. I let the airspeed get down to 105 and the bank to almost 10* ..  Once you pull the prop full coarse; everything improves and stabilizes. The bank minimizes and airspeed settles to about 125knots.

I never did use key-strokes to feather completely, so the prop was still wind-milling.

I think the real-world solution is to hold 5-7* of bank and just enough rudder to keep the ball about 1/2-ball off center. I'm sure it's more stable that way, because the auto-pilot uses only bank to hold a heading. In the Seneca I've flown, there's a spring linkage (like that between the nose-wheel and rudder) between the ailerons and rudder, so you have to kinda fight it a little. That makes for a VERY tired foot by the time you're STANDING on the rudder to land in a cross-wind..

[Hagar]

[quote]OK.. for the record, it's modeled quite realistically (to a guy with less than a dozen R/L multi-engine hours..

[beaky]

OK.. for the record, it's modeled quite realistically (to a guy with less than a dozen R/L multi-engine hours..  lol )

Level cruise 25/25 and leaned is about 180kias.

I used the auto-pilot for consistency. After pulling the mixture on the non-critical (right) engine (and going to full power on the good engine), the airspeed falls off as expected... the auto-pilot starts compensating for the yaw/pitch and if you do not pull the dead engine prop to full coarse... it just keeps getting worse. I let the airspeed get down to 105 and the bank to almost 10* ..  Once you pull the prop full coarse; everything improves and stabilizes. The bank minimizes and airspeed settles to about 125knots.


I never did use key-strokes to feather completely, so the prop was still wind-milling.

Thanks for confirming that Brett. I wonder how many people have actually thought of trying it.

Done it a few times, with various models... my payware DC-3 has working autofeather buttons, and behaves about as you'd expect with one engine secured... although the dead prop  takes some time to stop turning altogether. Not all models out there have the ability to go all the way into feather, though.

BTW, this reminds me: when I took that B-17 ride, I noticed  during the takeoff roll that the copilot had his hand on the glareshield right next to the autofeather buttons until after rotation (about when we cleared the fence), at which time he took over the quadrant while the pilot steered with both hands. I guess in a brute like that, if there's any hope of a go-around with a sick engine, that prop must be feathered immediately.

[Jon H]

Perpendicular: At 90o to...

[C]

The trouble with a failed engine is that the oil pump supply to the nose of the CS propeller also looses pressure, so unless the design automatically puts the prop into the feathered position, the propeller will remain at the angle is was in when the engine stopped...and may introduce excessive drag ...!

In which case you hope that the prop is designed to coarsen under oil pressure and feather using spring pressure - hence it will always failed to the (almost perpendicular) feathered position, which still encourages a small rotation of the prop (if the engine is not seized) which comes in useful of you were wanting to start the thing again.