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freakyre33
03-13-2008, 02:52 PM
Ok I've been using planes with auto-pitch I believe, but i feel I understand what prop pitch is and how it works now. Please correct me if im wrong. Prop pitch is the "angle of attach" of the prop blades, E.g if im flying level and the pitch is at 100% then the prop is at its steepest "angle of attack" lowering the percentage makes the blade dig through the air at a more shallow rate, intern increases the speed because the rpms aren't being slowed by the immense amount of air the prop is trying to propell. so in case, if i my plane is at 100% prop pitch on the horizontal and i turn near the vertical, rpms will drop because of gravity, but if I lower the percentange of the prop pitch or "angle of attack" i will build rpms because the blade is not working as hard against gravity to climb. or is it vise versa?

freakyre33
03-13-2008, 02:52 PM
Ok I've been using planes with auto-pitch I believe, but i feel I understand what prop pitch is and how it works now. Please correct me if im wrong. Prop pitch is the "angle of attach" of the prop blades, E.g if im flying level and the pitch is at 100% then the prop is at its steepest "angle of attack" lowering the percentage makes the blade dig through the air at a more shallow rate, intern increases the speed because the rpms aren't being slowed by the immense amount of air the prop is trying to propell. so in case, if i my plane is at 100% prop pitch on the horizontal and i turn near the vertical, rpms will drop because of gravity, but if I lower the percentange of the prop pitch or "angle of attack" i will build rpms because the blade is not working as hard against gravity to climb. or is it vise versa?

Zeus-cat
03-13-2008, 04:06 PM
100% prop pitch makes the blades cut the air at the shallowest angle. The pilot would see the entire flat side of the blade if he was looking out of the cockpit. If the prop were feathered (minimum prop pitch) he would see only the knife blade edge of the prop.

At 100% the engine can spin the prop the easiest. The lower the prop pitch the harder the engine would need to work to maintain the same RPM. However, the engine can rotate the prop at a lower RPM and still get the same thrust as at 100% pitch and full power.

Sergio_101
03-13-2008, 04:18 PM
At full fine, or ground idle pitch the blades are nearly paralell to the plane of rotation.

At full coarse they are a bit past 45 deg of plane of rotation.

Fine pitch is roughly comparable to low gear in a car.

Full coarse pitch is roughly comparable to over drive.

In the extreme there is feather pitch, where the blades are perpinduclar to the plane of rotation, purpose to reduce the drag of a failed engine.

And Reverse pitch, to slow or back up an aircraft.

Most modern props, and most used in WWII run automaticly
at a given RPM but with the pilots having limited control.
To govern the RPM the prop control will change pitch at a given RPM and prop setting.

In most applications if a given RPM is selected and you feed the engine more throttle the
RPM will not change, the prop will go more coarse
to keep the RPM at the desired setting.

Hope this helps.

Sergio

qlc1
03-13-2008, 04:46 PM
what prop pitch and what thottle settings do i use and when do i use them?
in an sbd for eg.
a bit of help with the mixture and super chargers woud be nice too.

freakyre33
03-13-2008, 05:32 PM
im not sure what you would use on the sbd, i've came to the conclusion ill use prob pitch more for efficiency then anything, I can run my p-40 at 95 % throttle and get get a good power with the prop at 80 to 85% im not sure what that db would use

ffb
03-13-2008, 06:31 PM
I havemy prop pitch on a slider.....and in any a/c when I'm cruising along I lower the pitch to 70-80%....it saves fuel
not forgetting to put it back to 100% before landing and when combat is joined...
and on a steep dive it is better to be at less than 100% pitch too

buzzsaw1939
03-13-2008, 08:33 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Zeus-cat:
100% prop pitch makes the blades cut the air at the shallowest angle. The pilot would see the entire flat side of the blade if he was looking out of the cockpit. If the prop were feathered (minimum prop pitch) he would see only the knife blade edge of the prop.

At 100% the engine can spin the prop the easiest. The lower the prop pitch the harder the engine would need to work to maintain the same RPM. However, the engine can rotate the prop at a lower RPM and still get the same thrust as at 100% pitch and full power. </div></BLOCKQUOTE>

Best discription I've seen in here so far! http://forums.ubi.com/images/smilies/25.gif

M_Gunz
03-13-2008, 08:55 PM
Actual prop pitch is NOT blade AOA.
Blade AOA depends on prop pitch, prop rpms and forward speed.
More rpms increase AOA at the same forward speed and blade angle -- path of blade flattens.
More speed decreases AOA at the same rpms and blade angle -- path of blade coarsens.
What besides 109 allows you to set blade angle?

Prop pitch that is really desired rpm is a different thing. With constant speed units:
More % flattens the AOA at the same forward speed while less % coarsens AOA at same forward speed.

EDIT: BTW if you haven't got enough power to be driving the plane at the speed you are going
then 100% CSP will only slow you down. Yes, even at 110% power you can go fast enough in a
power dive to outstrip the power of these planes so reduce your desired rpms (CSP prop pitch)
as you pass your level top speed. By 800kph you should already have been lowering rpms.

ffb
03-14-2008, 04:02 AM
I just flew as tail-end in a flight of three A-20's, and during a long flight over the ocean I was down to 40%power and 40% pitch just trying to keep in formation with them....just slightly adjusting my elevator trim....

I never have a problem with AI running off ahead anymore since I had prop pitch on a slider

ShaK.
03-14-2008, 08:05 AM
I know MOST of the above are "in RL" is correct.

Now with that said. I have tested prop pitch in the F4u-d and C. I would set up with unlimited 100% fuel. fly at 1000 meters alt for 5 min. to get perfectly trimmed out. (That more than enough time to do this)

Flying at 100% PP and 95% throttle w/open rad. perfectly trimmed.

Drop PP to 95% throttle remaing the same. The plane should slowly gain speed.?,? IT DOES NOT!!! It slows down!!! The plane looses speed. This should not occur until your engines HP is overwhelmed. I have tested this OVER AND OVER again with the F4u's with the same results. Maybe it acutaly works on other planes in IL2.

M_Gunz
03-14-2008, 05:32 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ShaK.:
I know MOST of the above are "in RL" is correct.

Now with that said. I have tested prop pitch in the F4u-d and C. I would set up with unlimited 100% fuel. fly at 1000 meters alt for 5 min. to get perfectly trimmed out. (That more than enough time to do this)

Flying at 100% PP and 95% throttle w/open rad. perfectly trimmed.

Drop PP to 95% throttle remaing the same. The plane should slowly gain speed.?,? IT DOES NOT!!! It slows down!!! The plane looses speed. This should not occur until your engines HP is overwhelmed. I have tested this OVER AND OVER again with the F4u's with the same results. Maybe it acutaly works on other planes in IL2. </div></BLOCKQUOTE>

Why do you feel that 95% power in F4U should have to be matched by 95% rpm and whatever speed
you were at? The two numbers of throttle and rpm are not tied in some special direct way.
Your speed and alt also affect results.
You may have to run at 90% or less throttle to choke down to where you need to reduce rpms
when level. But just where is a matter of how much excess power you are producing and that
gets complex beyond just "try it and see".

P-51D at 90% power can definitely go faster at less than 100% rpm at least at 2km alt!
My way to know is watch the VSI, alt gain or loss is about immediate with thrust change.

qlc1
03-14-2008, 05:46 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ShaK.:
I know MOST of the above are "in RL" is correct.

Now with that said. I have tested prop pitch in the F4u-d and C. I would set up with unlimited 100% fuel. fly at 1000 meters alt for 5 min. to get perfectly trimmed out. (That more than enough time to do this)

Flying at 100% PP and 95% throttle w/open rad. perfectly trimmed.

Drop PP to 95% throttle remaing the same. The plane should slowly gain speed.?,? IT DOES NOT!!! It slows down!!! The plane looses speed. This should not occur until your engines HP is overwhelmed. I have tested this OVER AND OVER again with the F4u's with the same results. Maybe it acutaly works on other planes in IL2. </div></BLOCKQUOTE>
i have noticed this too.with all planes.what ever i do to the engine,whether it be prop pitch or fuel mixture,or super chargers, results in loss of speed.and in an sbd,i aint trading speed for anything.i do notice however,any prop pich adjustments made do make flying a hell of a lot easier.ie holding an attitude.

ShaK.
03-14-2008, 06:59 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:

Why do you feel that 95% power in F4U should have to be matched by 95% rpm and whatever speed
you were at? The two numbers of throttle and rpm are not tied in some special direct way.
Your speed and alt also affect results.
You may have to run at 90% or less throttle to choke down to where you need to reduce rpms
when level. But just where is a matter of how much excess power you are producing and that
gets complex beyond just "try it and see".

P-51D at 90% power can definitely go faster at less than 100% rpm at least at 2km alt!
My way to know is watch the VSI, alt gain or loss is about immediate with thrust change. </div></BLOCKQUOTE>

I think you mis-understood what I posted or you meant to quote someone else. If you did not understand, I was trying to say that in IL2, flying a F4u, you can be flying level with 100% prop, and (insert variable here)% throttle, if you drop your prop pitch, The plane's SPEED will slow down. But I'll admit, My testing was done at low Alt (around 1000m) Maybe due to the thickness of the air at low alt, the plane would slow down. Maybe high atl (4000+m) the plane would have the power to turn the prop and it would actualy speed up?&gt;?&gt;?
I think I will have to re-test.

M_Gunz
03-14-2008, 07:30 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ShaK.:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:

Why do you feel that 95% power in F4U should have to be matched by 95% rpm and whatever speed
you were at? The two numbers of throttle and rpm are not tied in some special direct way.
Your speed and alt also affect results.
You may have to run at 90% or less throttle to choke down to where you need to reduce rpms
when level. But just where is a matter of how much excess power you are producing and that
gets complex beyond just "try it and see".

P-51D at 90% power can definitely go faster at less than 100% rpm at least at 2km alt!
My way to know is watch the VSI, alt gain or loss is about immediate with thrust change. </div></BLOCKQUOTE>

I think you mis-understood what I posted or you meant to quote someone else. If you did not understand, I was trying to say that in IL2, flying a F4u, you can be flying level with 100% prop, and (insert variable here)% throttle, if you drop your prop pitch, The plane's SPEED will slow down. But I'll admit, My testing was done at low Alt (around 1000m) Maybe due to the thickness of the air at low alt, the plane would slow down. Maybe high atl (4000+m) the plane would have the power to turn the prop and it would actualy speed up?&gt;?&gt;?
I think I will have to re-test. </div></BLOCKQUOTE>

Oh! Well I can say that when I am on landing approach I use low throttle and 100% pitch just
to control my speed, just to slow down. On approach I have power at 30%, rpms at full which
means to go-around I don't have to get my revs up, just power.

I think you see things as they are and only need to do more testing. You are holding level I
assume and yeah 1000m is a good alt to check. I just wondered why 95% power in over-powered
plane would not be enough (you've explained I think the 95% is just an example?) and from
practice I know there are power settings that will give a higher top speed at less rpms, 90%
power in P-51D at 2km alt for example.

Have you noticed cutting rpms to tone down gyro-nose wandering when aiming? I think I have
at 70% rpm in P-51 but I can't swear to it.

I've gone up to 100-100 speed in P-47's and cut power to 70% to see the how fast I would slow
down at different pitches and with 70% power the 100% pitch slowed me down quicker than 70%
pitch. I first did that when FB came out and we were all checking the new CEM features. I
also did some things that pilot friends tell me would destroy real prop gearing and engine!
Dive down at over 800 kph and to slow for fast landing, 100% pitch and power to idle (boom!)
then scrub speed and land in seconds -- when you're chased online it's not good to take a
long time on approach, LOL!

qlc1
03-15-2008, 02:28 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by qlc1:
[i have noticed this too.with all planes.what ever i do to the engine,whether it be prop pitch or fuel mixture,or super chargers, results in loss of speed.and in an sbd,i aint trading speed for anything.i do notice however,any prop pich adjustments made do make flying a hell of a lot easier.ie holding an attitude. </div></BLOCKQUOTE>
i stand corected.
i cant beleave im saying this but..les speed in an sbd is good against your average piolet.
the slower i go the les they hit me..combine that with low......