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IV_JG51_Razor
12-28-2003, 10:23 AM
Oleg, would it be possible to make the props actually stop after they have been featherd? As it is now, after shutting an engine down, and feathering the prop, it slows down to a stop, then begins accelerating BACKWARDS to the point where you can't tell the difference between a feathered prop, and one that is being turned by the engine. I have found that if you slow down sufficiently, the prop will actually stop, but that is down around landing speed.

Is this a possibility Oleg? Thanks for your time, and I wish you and your crew a happy New Year! http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif

IV_JG51_Razor
12-28-2003, 10:23 AM
Oleg, would it be possible to make the props actually stop after they have been featherd? As it is now, after shutting an engine down, and feathering the prop, it slows down to a stop, then begins accelerating BACKWARDS to the point where you can't tell the difference between a feathered prop, and one that is being turned by the engine. I have found that if you slow down sufficiently, the prop will actually stop, but that is down around landing speed.

Is this a possibility Oleg? Thanks for your time, and I wish you and your crew a happy New Year! http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif

p1ngu666
12-28-2003, 02:26 PM
i thought they did windmill ?
i pressume the blades goto least drag mode, which will probably make them turn a little

LEXX_Luthor
12-28-2003, 03:43 PM
Also shut off magnetos and the props stop spinning below about 180km/hr.

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IV_JG51_Razor
12-28-2003, 04:15 PM
A feathered prop does not windmill, and once the engine is shut down, the mags have no function. But you're right Lexx, they will stop turning below 180 or so. http://ubbxforums.ubi.com/infopop/emoticons/icon_frown.gif

Razor
IV/JG51 Intelligence Officer

"Good judgement comes from experience, and experience comes from poor judgement"

JG5_Scorpius
12-29-2003, 10:58 AM
Razor,

Do you center the slipball? If not, the prop will continue to rotate, same as in RL.

Regards,

Scorpius

p1ngu666
12-29-2003, 11:21 AM
i thought with the blade design they would always turn
i probably wrong tho :P

IV_JG51_Razor
12-29-2003, 11:39 AM
Scorpius, yeah, I get the plane trimmed up with the rudder, but in game, this makes no difference. The prop(s) continue to rotate, albeit backwards, untill the speed drops to around 180 or so. Then they will stop. As far as RL is concerned, I've never seen the props continue to rotate after they have been feathered, regardless of how the plane is trimmed. Even with a turbo prop engine, where there is no compression to overcome, a feathered prop will remain motionless in flight. I'm a pilot with a multi engine rating, and have some first hand experience with this situation.

It's not a real big deal within the context of this great sim, just one of those little things I'd like to see corrected. If, for no other reason than for others to be able to see that you have an engine shut down and feathered. As it is now, an attacking fighter has no way of knowing that his quarry is flying on only one engine.

Razor
IV/JG51 Intelligence Officer

"Good judgement comes from experience, and experience comes from poor judgement"

JG5_Scorpius
12-29-2003, 02:52 PM
Razor,

I work for an aircraft manufacturer and our experience is different. However, I did some testing in the sim (which I should have done in the first place) and I agree that the feathered prop behaviour is not realistic. Not only will the prop turn regardless of the slip angle, it also turns much too fast.

Regards, Scorpius

IV_JG51_Razor
12-29-2003, 04:13 PM
Now you've got me hooked Scorpius, tell me all! http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif Which plane are you referring to? How 'out of trim' do you need to be in order for the prop to continue rotating after it's feathered? Speed? I've never heard of this situation. I'm truely interested.

Razor
IV/JG51 Intelligence Officer

"Good judgement comes from experience, and experience comes from poor judgement"

BfHeFwMe
12-29-2003, 07:24 PM
No way could a piston engine ever be allowed to spin that fast reversed. You reverse the rotation and your bearings get no oil flow, your valves are now reverse ordered so you get even more compression. That engine is comming off the mount, and real quick.

WhtBoy
12-29-2003, 10:56 PM
Similar to an overspeed when the prop is not feathered before the oil pressure drops (in those a/c with oil pressure driven pitch), I'd bet that the crankshaft sieze would break the prop shaft or gearbox before the engine mounts failed.

-WhtBoy.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by BfHeFwMe:
No way could a piston engine ever be allowed to spin that fast reversed. You reverse the rotation and your bearings get no oil flow, your valves are now reverse ordered so you get even more compression. That engine is comming off the mount, and real quick.<HR></BLOCKQUOTE>

JG5_Scorpius
12-30-2003, 11:06 AM
Razor,

I'm referring to the F27, which is a turboprop aircraft but with single shaft engines. In other words a wind milling prop drives everything, the complete engine and the accesory gearbox with pumps, generator, compressor and roots blower. The minimum torque to rotate that powerplant is probably less than what you need for a large piston engine, but I don't think it will be that much. On the F27 we see up to 30 rpm with less than a full ball of center at about 180 knots.
To convince Oleg that the change you requested should be made, it would be helpful if someone with flight test experience on multi engine aircraft equipped with large piston engines could provide some input.

Regards, Scorpius

IV_JG51_Razor
12-30-2003, 01:31 PM
Very interesting Scorpius. Thanks for the reply. I've never heard of that before. Tell me, if the plane is trimmed up properly, will the prop then stop rotating? If so, will it again begin to turn if the pilot gets it out of trim?

As for Oleg, I'm quite sure he is aware of how the props are supposed to stop turning after being feathered, and doesn't need a flight test engineer to explain it to him http://ubbxforums.ubi.com/infopop/emoticons/icon_wink.gif It's just some kind of glitch in the programming that does this. Have you ever noticed, online, another human's plane sitting on the ramp for a while (after the engine has been shut down) and the prop slowly windmills? I'll bet the two are connected somehow.

Razor
IV/JG51 Intelligence Officer

"Good judgement comes from experience, and experience comes from poor judgement"

IV_JG51_Razor
12-30-2003, 01:36 PM
Something else I've been wondering about, but never had the ambition to actually test, is if the windmilling prop in the game causes any additional drag as it would in RL. In other words, after feathering the prop, is there less drag than if you didn't feather it (even though the game shows it turning)?

With more multi engine planes coming into the game, this might be a very important question to have answered. I suppose I ought to get off my butt and go find out http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif I'll let you know what I see.

Regards,

Razor
IV/JG51 Intelligence Officer

"Good judgement comes from experience, and experience comes from poor judgement"

BfHeFwMe
12-30-2003, 03:22 PM
Absolutly, all depends on the prop size, angle, and turn rate though. A T-56 engine, one I'm most familiar with, unfeathered with a flat angle would give as much drag as an entire wing on a C-130. So it was a huge deal to get it feathered, will make the difference between clearing a mountain or making it back to land.

We had manual electric fine tune control over prop angle, the co-pilot would bump the feather motor slowly to stop all rotation, normally an engine shutdown by pulling the emergency handle would end up with slight rotation, that had to be stopped manually.

DaBallz
12-30-2003, 06:35 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by JG5_Scorpius:
Razor,

I'm referring to the F27, which is a turboprop aircraft but with single shaft engines. In other words a wind milling prop drives everything, the complete engine and the accesory gearbox with pumps, generator, compressor and roots blower. The minimum torque to rotate that powerplant is probably less than what you need for a large piston engine, but I don't think it will be that much. On the F27 we see up to 30 rpm with less than a full ball of center at about 180 knots.
To convince Oleg that the change you requested should be made, it would be helpful if someone with flight test experience on multi engine aircraft equipped with large piston engines could provide some input.

Regards, Scorpius<HR></BLOCKQUOTE>


Turbo prop engines have prop brakes to prevent
windmilling after shut down or on the ground.

If a prop fails to feather you hoped for a
shaft or gearbox failure. A siesure was better
than windmilling. Boeing data on windmilling
props said (for a Stratocruiser) around
1,000hp parasitic drag for a windmill.
that's more than twice the drag than any other
condition than a "run away".

Run away's were the worst case. An over speeding engine could, and did, tear off the wing. Run away's often did not feather because
the same mechanism that goverened the prop
also feathered it. http://ubbxforums.ubi.com/infopop/emoticons/icon_frown.gif

Also a failed prop speed governer could run
the prop speed so high as to cause wing failure
from the vibration.

If you had an uncontrollable run away you prayed
for the prop to tear off the engine.

Few WWII Era props could pitch into reverse.
I for one have never heard of a prop windmilling
backwards!

On the other hand a damaged, lets say twisted prop
may force the engine to mill over backwards till it seizes.

By the way BfHeFwMe, I have 4 years of crew chief C-130 time.
Moving the condition lever to feather would stop the engine cold.
A "t" handle shut down had the same effect but
was more abrupt.

I was on a flight from Hawaii to Guam on WC-130E 61-2360
when the flight crew caged #2 for a nacelle overheat, it wound down to a stop very quickly.
Neither the Co or FE had to tweek anything. We spent a week on Wake Island awaiting parts. I had a blast!

You are correct about failure to feather a prop on a T-56A7 or T-56A-15. In ground idle position the drag would likely force a landing NOW!

But as I remember the Hamilton Standard props fitted failed feathered in flight if not damaged by gunfire or accident.
also if the prop was fixed in a power setting the gear box will disconnect (there is a small "fuse" shaft that will shear if over torqued). As I remember that was called a "decoupling".

Da

[This message was edited by DaBallz on Tue December 30 2003 at 05:46 PM.]

IV_JG51_Razor
12-30-2003, 06:46 PM
"Turbo prop engines have prop brakes to prevent
windmilling after shut down or on the ground."

That's not exactly true for most turbo props. It's becoming more common amongst the passenger carrying aircraft, however, most other corprate planes don't have that feature. It's certainly not characteristic of the turbine engine itself, just an expensive add-on applied by the airframe manufacturer.

The DC-7, with the R-3350's and Power Recovery Turbines had reversing props I believe.

Razor
IV/JG51 Intelligence Officer

"Good judgement comes from experience, and experience comes from poor judgement"

DaBallz
12-30-2003, 06:56 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by IV_JG51_Razor:
"Turbo prop engines have prop brakes to prevent
windmilling after shut down or on the ground."

That's not exactly true for most turbo props. It's becoming more common amongst the passenger carrying aircraft, however, most other corprate planes don't have that feature. It's certainly not characteristic of the turbine engine itself, just an expensive add-on applied by the airframe manufacturer.

The DC-7, with the R-3350's and Power Recovery Turbines had reversing props I believe.

Razor
IV/JG51 Intelligence Officer

"Good judgement comes from experience, and experience comes from poor judgement"<HR></BLOCKQUOTE>

The prop brake is part of the prop, not the engine. On some engines it may be in the gearbox.

Some flying boats such as the Martin Mars had reversable props, but it was a rare feature during WWII.

The DC7 was available with reversing props as was the DC6 but no DC7 flew during WWII and the R-3350TCW engines were a post war development.
I am not aware of any combat aircraft that had reversing props during WWII but I have a feeling I will be proven wrong!

My experiance with Turbo Props is limited to the C-130 Allison T-56's and Tech School on the North American Rockwell OV-10A Bronco powered by Garrett-AiResearch T76s.

Both had prop brakes.

Da

IV_JG51_Razor
12-31-2003, 12:12 AM
Oh, I realized it wasn't a WWII plane, it's just the only one I could think of with piston engines that had reverse.

I didn't realize the Bronco had a prop brake either. The CDF (California Dept of Forestry) operates them, and I've never seen them use a brake to stop them. That would be really handy when you've got to get out quick for a head call! http://ubbxforums.ubi.com/infopop/emoticons/icon_wink.gif

Well, all this has been an intersting education. Thanks Da and Scorpius. http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif I just hope Oleg sees this thread and does something about the prop feathering feature in FB http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif That would be really nice to see.

Razor
IV/JG51 Intelligence Officer

"Good judgement comes from experience, and experience comes from poor judgement"

DaBallz
12-31-2003, 04:20 AM
"I didn't realize the Bronco had a prop brake either. The CDF (California Dept of Forestry) operates them, and I've never seen them use a brake to stop them."

You do not use prop brakes! The action of a prop brake
can not be seen on a T-56 either. But go over to
a C-130, grab a blade and try to turn a prop.
It takes some real effort. You really got to lean on it.

Prop brakes apply on shut down to prevent flight line wind milling. They also prevent windmilling of a feathered prop. They do little or nothing in the action of stopping an engine that has been shut down normally.

A T-56 with bad a prop brake can easily be turned by hand, and required an engine change.

Da

IV_JG51_Razor
12-31-2003, 09:50 AM
AH SOOOO. Now I'm beginning to understand. I thought you were talking about something that actually had some kind of brake disk and calipers!! LOL Well, I've seen the pilot of that CDF Bronco get out after shut down and spin the props backwards for a minute or two, and they seem to spin fairly easily. I asked him why he was doing that, and he said it was to prevent coaking on such n such bearing. The pilot of our Cessna Conquest has to do the same thing, and since they both have Garrets in them, it made sense to me. However, the props are certainly easy to turn. One thing that I've noticed though, is that both the Conquest and the Bronco look like they have gone to completely flat pitch on shutdown. I'm wondering if that is to prevent flight line windmilling? Those Garrets really are easy to spin. After all, they are about the size of the APU of a C-130!! http://ubbxforums.ubi.com/infopop/emoticons/icon_biggrin.gif

Razor
IV/JG51 Intelligence Officer

"Good judgement comes from experience, and experience comes from poor judgement"

cafflier
12-31-2003, 02:14 PM
I have flown the EMB 120 Brasilia turbo prop for a living. When you feather the prop it stops. We don't have prop brakes because, when we park it we feather the props and they stop quite quickly. They will windmill while sitting on the ground if the wind is strong enough. When you lose an engine on a multi engine airplane the correct thing to do is bank about 5 degrees into the live engine and slip about half a ball's width. This provides minimum drag. The airplane will not be co-ordinated and may have airflow across the prop blades to move them slowly, as someone mentioned regarding the F27.
I got my Multi Comm and MEI in a C55 Baron. The props stopped when you feathered them and they stayed stopped. Infact, I seem to remember that you had a recommended minimum unfeather airspeed since you had to have a certain amount of airflow to overcome engine compression. There was also, I think, a maximum unfeather speed so you didn't over speed the engine.
I also fly a C-46 for the CAF in California. It is powered by the R2800. When you feather that, it stays stopped also. The prop is forced into the feathered position by an electrical feather pump. Pressing the feather button runs the pump and as long as the oil pressure remains below a certain value, a solenoid holds the button down and the pump continues to run. Once the prop is fully feathered, oil pressure exceeds that value and a pressure switch opens de-energising the feather button solenoid, releasing the button and switching off the pump. Prop is feathered and engine compression stops the engine. If the oil pressure switch is inop, the pump continues to work, opens a shuttle valve and unfeathers the prop. The prop will sit out there all day going in and out of feather until you crash, which you will. We think that's how our B26 Marauder was lost.
By the our Convair Vc131 has the same system as well as Auto feather and reverse.

IV_JG51_Razor
12-31-2003, 02:33 PM
This is all great poop! Cafflier, didn't the B-26 have Curtis electric props?? I thought their pitch was controlled by an electric motor, unlike the Ham-Standards that use engine oil pressure.

BTW, I've seen your 'China Doll' around So Cal, and she's a real beauty!! My company used to have one that we used to ferry helicopter parts around with, but it got too expensive to maintain. It has Ham-Standard props also, which I believe was a mod. I believe **** Foy has her now, or she's up in Jack Erickson's Tillamook Museum, not sure.

Razor
IV/JG51 Intelligence Officer

"Good judgement comes from experience, and experience comes from poor judgement"

cafflier
12-31-2003, 03:53 PM
Early ones had the Curtiss Electric props, but later ones, like ours, had the Ham Standard.

DaBallz
12-31-2003, 04:24 PM
The APU/GTC in a C-130E developed around 1,000hp
so was far more powerful than an Garret powering an OV-10A.

The props could be easily turned by hand on an OV-10.
The prop brakes only offered a little resistance.

On a C-130 turning over a T-56 by the prop blades required a good amount of effort, but I could do it and "X" or "T" the props without a fight.
But I could not "spin" a prop with good brakes.

Da