feathering a prop

[Golfer]

hitech, the props will only auto feather if the engine is dammaged.

Flyboy, Not true.  Try the P-38 as an example.  Shut off the engine manually and the props do go to full feather thanks to autofeather.  Like HTC said, if the props have feathering capability (not many do as most airplanes in this game are Piston singles.) they will automatically feather.  And they do.

These engines don't have feathering props, they just stop turning due to internal damage preventing the propeller from windmilling.

how did the dual pitch props (like Battle of Britain era Spitfires & Hurricanes) operate? It couldn't have been on oil pressure, could it?

I haven't seen any information on hurricanes and spitfires that they had anything other than constant speed propellers.  They have them in-game and I'm sure HTC did their homework.  They work on high pressure oil (same oil as in the engine) which is put under pressure by the governer and it pumps it into the engine based on mechanical flyweights...its not a terribly complex system actually.

If you know something I don't, post a link I'd like to learn more.

one more thing i found out, even after i turn the engine off, the RPM stay the same, even in very low speed, graphicly, you can see the prop turning slowly but the there is no movement in the RPM gauge, if i will take the plane to a even lower speed (below 40mph) the prop will stop turning and the rpm will show zero, meaning the prop is feathered i guess. after the prop stop turning no matter what speed ill go it wont move unlesss i turn on the engine.

Use your propeller controls the +/- keys on the NUMPAD or you can set them for whatever you'd like.  These come in handy to stretch glide range in a single if you run out of fuel or to extend the range as per the power settings in the E6B.

and lastly when the engine is off and the prop is still turning, when i start the engine it imidiatly goes to full power (or whatever power im on), but if the prop is feathered it will have to do the whole start up routine and it will take a few seconds.

This is absolutely correct and how it works in real life.  If the propeller is spinning and you cut your engine (hitting the E key) basically all you're doing is pulling what is referred to as the "Mixture" control and turning off the Magnetos.  This prevents fuel from getting to the engine.  With no fuel, there is nothing to go 'boom boom boom' in the engine.  With the propeller still turning, once you reintroduce the fuel/air mixture into the cylinders and turning on the magnetos, which give the spark plugs their spark (all done by pressing the E key) they will immediately begin firing.

If the engine has to come out of feather, there are a few ways to do this in a real airplane.  The use of an accumulator, which these airplanes don't have or you have to restart the engine.  This was common practice during my multiengine training, as just flipping the starter on a feathered prop (in flight) wouldn't provide enough oil pressure to get the propeller out of feather.  The standard thing to do was prime the engine while keeping the power just off idle.  Once it began firing again, you were in for a rather violent shaking because the prop was coming out of feather and with the engine not firing very fast that just caused a racket.  Eventually, there was enough oil pressure (after about 6-10 very long seconds) to cause the propeller to just 'windmill' and you let the engine gradually warm up at that very low setting before you powered it up.  This is so you don't crack cylinders with a fast heat/cool/reheat cycle.  With the real airplane, starting an engine with the prop feathered like that, took about 2 minutes for the whole cycle to be complete to the point you could power up again.  I'd say HTC is letting us off easy

[Flyboy]

thnks for the the info golfer.
that pretty much clear things up.

so are you saying the P51 and the spit cant feather their prop? (just 2 planes of my head)

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one more thing i found out, even after i turn the engine off, the RPM stay the same, even in very low speed, graphicly, you can see the prop turning slowly but the there is no movement in the RPM gauge, if i will take the plane to a even lower speed (below 40mph) the prop will stop turning and the rpm will show zero, meaning the prop is feathered i guess. after the prop stop turning no matter what speed ill go it wont move unlesss i turn on the engine.
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Use your propeller controls the +/- keys on the NUMPAD or you can set them for whatever you'd like. These come in handy to stretch glide range in a single if you run out of fuel or to extend the range as per the power settings in the E6B.

that is not my point, reread what i wrote.
i do not understand how the plane holds the RPM constant with the engine turned off?
and why when i go below certien speed the prop stop spinning and no matter what speed i will go it wont start spinning again, unless i start the engine again.

[jigsaw]

Originally posted by Golfer
I haven't seen any information on hurricanes and spitfires that they had anything other than constant speed propellers.

There's another prop system called Adjustable Speed which only has two settings, one for high , one for low. I've only seen it in books, never in an aircraft.

Golfer, did/are you taking classes at UVSC?

[Golfer]

that is not my point, reread what i wrote.
i do not understand how the plane holds the RPM constant with the engine turned off?
and why when i go below certien speed the prop stop spinning and no matter what speed i will go it wont start spinning again, unless i start the engine again

The reason the plane holds RPM (and its not constant, if you hold down the - key it will decrease) is because of the air blowing over the propeller causing it to windmill.  My standard practice when I either run out of fuel or am 'nursing' back to base due to a radiator hit is to hold best glide speed while basically holding down the - key on the NUMPAD to get the propeller to be pointing as much as possible into the wind causing the least amount of drag.  It will still windmill, but it won't cause as much drag.

Now...I'd like to know what airplane you're in while in-game that you can get it to stop spinning.  I've tried to do that (that is an ideal condition and standard practice in a real airplane if at a safe altitude to pull the airplane's nose up to stop the spinning prop so it is creating the least possible drag) and have been unsuccessful.  By my count you have to be going <50 kts and that isn't a good idea if trying to get any sort of range out of your glide.

[Golfer]

Originally posted by jigsaw
There's another prop system called Adjustable Speed which only has two settings, one for high , one for low. I've only seen it in books, never in an aircraft.

Golfer, did/are you taking classes at UVSC?

There are also Ground adjustable and adjustable pitch.  Ground adjustable are big in the ultralight world and adjustable pitch aren't really used because constant speed propellers are just that much more simple to use.

Also, I'm in my last 1-2 semesters at UVSC, they've had their growing pains but its getting sorted out.  Should graduate end of summer 2005, at the very end of my 4th year out of high school...something not many folks do nowadays.

[jigsaw]

Originally posted by Golfer

My standard practice when I either run out of fuel or am 'nursing' back to base due to a radiator hit is to hold best glide speed while basically holding down the - key on the NUMPAD to get the propeller to be pointing as much as possible into the wind causing the least amount of drag. It will still windmill, but it won't cause as much drag.

Little trick I learned while working on my cpl; Doing power off 180s if you were a bit hot or high, go full prop early for the added drag.

Should graduate end of summer 2005, at the very end of my 4th year out of high school...something not many folks do nowadays.

Thought so. One of the course numbers you posted in another thread looked familiar. Grats on 2005. I'll be finishing the AS this semester and matriculating into the BS this fall with two upper classes already finished. Going just out of HS is the best way to do it. I had to wait until I was officially an old fart to get back into it.

[flakbait]

The ability to feather a prop entirely depends on the prop type.

Most models of Hamilton-Standard props used on WW2 aircraft can't feather at all. Some makes, like the model used on the B-29 and other late-war transports, dump oil overboard (an "open" system) to feather it. Fighters never got this unit because of the sheer size of it, and they really didn't need it. The F4U, P-51B/D, P-47, P-61 and many others used this type of prop.

Curtiss Electric props could be feathered depending on the model. The P-38 used a featherable CE prop because of the single-engine operation requirement. Most P-40s, Allison-powered P-51s, and some P-47s also used the CE. The difference between a non-featherable and a prop that could be feathered was in the planetary reduction gearing. The P-40 used a prop that could go from 24.5º to 54.5º; a fairly narrow range. The P-38 used a different model, allowing 22.7º on the high end to 57.7º on the low end with feather being 87.5º.

Aeroproducts props also can't feather due to the design. Each prop blade has a piston in the prop butt that fixed the amount of travel and acted as a blade stop. Deak has told me about operators of two F8F Bearcats down Arizona ways that have a constant problem in which the prop loses oil and slams down against the full low pitch stop. It has something to do with bad O-rings. The P-39, P-51K, and a few others used this with some success.

As for prop control, that was done by a lever in the cockpit. For Aeroproducts or Ham-Stans moving the lever changed the governor setting and the prop would change pitch, allowing the engine to speed up or slow down. The AH system of using the +- keys serves the same function. A Curtiss prop could be actuated in two ways. You could either manually increase or decrease the pitch with a switch and the governor would hold it there, or you could set it directly so it acted like a fixed-pitch model.

Jigsaw got the early Hurri and Zitfire prop stuff dead on. Early on they had a prop that either ran too slow, or too fast. At the Low setting the pitch was far too high for the engine to get much use out of it, and the High setting was so shallow the engine would nearly over-speed while taking tiny bites of air. It was a real mess that was fixed in mid '41 if my memory is correct.

Flyboy, neither the Spit nor the P-51 could feather it even if they wanted to. Neither one had a prop model that would allow the pilot to throw it in full feather. You could crank the pitch way up (lowering RPM) to reduce drag, but you couldn't feather it. As for why RPM holds, that's simple; if you leave the prop lever alone and kill the engine, you aren't shutting off the governor. It continues to work, holding the RPM roughly where you left it. If you slow the aircraft down, you'll see the RPM drop off because there isn't enough air flowing over the prop to spin the prop, and thus the engine, at the speed you set. Killing the engine simply stops the "bang" part, the generator is still turning, the governor still works, and the oil pump is still moving because the engine is not stopped. Remember, the engine and the accessory case (generators, pumps, governor, etc...) are all linked. To stop all those from working, you have to stop the engine... and hence the prop.




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Flakbait [Delta6]

[Flyboy]

If you slow the aircraft down, you'll see the RPM drop off because there isn't enough air flowing over the prop to spin the prop, and thus the engine, at the speed you set. Killing the engine simply stops the "bang" part, the generator is still turning, the governor still works, and the oil pump is still moving because the engine is not stopped. Remember, the engine and the accessory case (generators, pumps, governor, etc...) are all linked. To stop all those from working, you have to stop the engine... and hence the prop.

flakbait, that is exactly what i thought. plane slow down= RPM drops.

but as i stated above most planes (i checked the spitfire 9, 190d9, Ki84, P40b, P40e, P51d and the p38)

WILL hold maximum RPM at speeds below 100mph, at around 5o-40mph the RPM will suddenly drop all the way too zero and the prop will "lock" and wont spin no matter what speed i go unless i press E again.

the exeptions are:
P38: it feathers his props after the engine is turned off

P51d: maximum RPM will drop as speed slows down (as it should) but it still gets the unexplained "prop lock"

Ki84: it will hold maximum RPM all the way till 50-40mph, but then the RPM needle will go up for like half a second and then start a drop towards zero and the prop lock.

btw P40s in AH do not feather the props

[hitech]

Flakbait: That oil pressure problem where prop goes full low pitch also happens to standard hartzels when doing acro and you loose oil pressure do to zero G. Like in a hammer head. Engine all of a sunden revs up.

This has to do with the cristen inverted oil system valve sorta stuck in limbo at 0 G.


2 ways around the problem. Some people put a nitrogen pressure system with an extra oil reserver to maintain pressure when 0 G.

Or an areobatic prop it dosn't push back with a spring but wrather counter weights move it to max pitch and oil pressure moves it to flat pitch. Then when oil pressure is lossed it goes max pitch, engine loads down instead of over speeding.


HiTech

[flakbait]

I never said a P-40 could feather the prop, I simply used the example of a P-40 to show the differences in CE props made. Some could feather, some couldn't; it entirely depended on the model. The rest (Ham-Stan, Aero) couldn't because of the physical design limits.

AH does not correctly model windmilling, I can tell you that now. A Beech Bonanza has to be flown with the prop pitch set full high (very low RPM) at nearly a stall (62 knots) before the prop stops. You can then fly it up to around 95 knots before it'll start windmilling again. AH doesn't model this accurately at all because you can't get the prop to windmill once you've stopped it. It's not that HT isn't aware of this (a simple power-off prop test would confirm it, though the speeds would only be valid for an RV-8) it's that stopping and starting a prop with the engine off isn't really necessary when you're talking aerial combat. Modeling the amount of prop drag per degree of pitch is more important.

HT, yeah I know a little about the more modern prop types using springs or weights instead of oil. Though the old ones still hold my fancy. I'd love to have all three modeled accurately... ahhh, wishful thinking!


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Flakbait [Delta6]

[Flyboy]

is it possible to feather the prop while the engine is still running? (somehow disconnecting the transition from the engine, like a clutch in a car?)

[jigsaw]

Originally posted by Flyboy
is it possible to feather the prop while the engine is still running? (somehow disconnecting the transition from the engine, like a clutch in a car?)

You can feather with the engine running, but It's very bad for the engine.  You can't completely disconnect it.

Generally as long as the engine is still producing power and not in danger of seizing, you want to keep it running.
If it's in danger of seizing, you shut it down and feather. Sometimes with the possibility of restarting it before you land.

On the twins I've flown you had to feather before the RPM fell below a certain number. Otherwise you'd be stuck with a windmilling prop.

Here's a linked pic of the governor system.

[Golfer]

That's an awfully complex photo.  Here is my CS propeller diagram that I keep in my Commercial and Multiengine instruction binders.

[Bodhi]

Originally posted by jigsaw
You can feather with the engine running, but It's very bad for the engine.  

Thats an incorrect statement.  

On an equipped A/C, you better damn well ensure your prop feathers every time you start the SOB up, if you read your checklist, it especially mentions to ensure proper engagement of the feathering system so that if in flight you do have an engine failure, you know damn well it will work.

So, if your checklist is telling you, as well as common sense is telling you to do it, tell me how it is hurting the engine.

If your retort is that "You can not run it indefinitely in feather" then do not bother, as that is not true either.  I can give numerous examples of aircraft that will run indefinitely on feather so long as you are not trying to achieve maximum RPM, which is common sense.

Plain and simple, the prop can be feathered and is done frequently with the engine running without causing damage...

[Golfer]

I figured we were fairly universal about piston engines and their propellers.

Though, intrigued...I'd like to hear a piston airplane that uses such a procedure as starting the engine in feather.

 Forgot to mention that I could name more than a few turboprops that start in feather, but thats a whole different ball of wax in a different can of worms.  We're talking about piston engines and again, I'd like to hear of one because that's new to me.