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View Full Version : Help with the Basics of Radiator and Prop Pitch Management Please...



xxcurarexx
01-09-2005, 03:07 PM
I'm starting to become competitive playing on-line...and it's great mixing it up with you guys. My gunnery's gotten pretty good and my maneuvering and tactics are coming along swimmingly, so I figure it's now time to fine tune my flying by introducing radiator and prop pitch management. Problem is - I know nothing about the effects of changing radiator or prop pitch settings. While I realize that different planes will react differently, what are the basic points for managing these two items, such as:

What are the advantages/disadvantages of having radiator closed/open?

How does changing prop pitch affect climbing ability or max speed?

and so on...

Thx in advance for any info you provide.

S! all.

xxcurarexx
01-09-2005, 03:07 PM
I'm starting to become competitive playing on-line...and it's great mixing it up with you guys. My gunnery's gotten pretty good and my maneuvering and tactics are coming along swimmingly, so I figure it's now time to fine tune my flying by introducing radiator and prop pitch management. Problem is - I know nothing about the effects of changing radiator or prop pitch settings. While I realize that different planes will react differently, what are the basic points for managing these two items, such as:

What are the advantages/disadvantages of having radiator closed/open?

How does changing prop pitch affect climbing ability or max speed?

and so on...

Thx in advance for any info you provide.

S! all.

Atomic_Marten
01-09-2005, 06:40 PM
Here you are. (http://www.airwarfare.com/guides.htm)

Furious-E
01-09-2005, 06:49 PM
The way I understand it is that the further you open your radiator, the more the engine stays cool, but also the more drag created, thus slowing down your plane.

Prop pitch is a measurement of how much air the prop is sucking through. 100% being full capacity, 0% being none. Obviously the more air your prop sucks through, the faster your plane will move and the better it will climb, but it also puts a heavier strain on your engine. The RPM meter is a great way to see what kind of prop pitch the engine can take; it differs from plane to plane, but with my P51D I usually set my prop pitch to equal an RPM of about 2700-2900, which is generally around 80% pitch or so.


But I'm also new to this game (and flight sims) so someone correct me if I'm wrong.

FatBoyHK
01-09-2005, 07:21 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Furious-E:
but with my P51D I usually set my prop pitch to equal an RPM of about 2700-2900, which is generally around 80% pitch or so. <HR></BLOCKQUOTE>

On US planes you don't set prop pitch, instead you set the RPM directly, and the prop pitch will be adjusted automatically to maintain the RPM.

on LW planes you play with prop pitch directly. RPM varies when your speed change, and you may fry your engine if you don't pay attention.

drose01
01-10-2005, 12:26 PM
The complex engine management link on the "Airwarfare" site that marten referenced is good, but still leaves me with a few questions.

I am understanding that prop pitch can be adjusted to avoid over-revving the engine and preventing engine damage. The comparison is made to a manual transmission automobile, where if you rev too fast, you should switch gears.

The question is, does adjusting prop pitch to get the plane into the optimum/safe RPM power band actually improve performance? Do you go faster at a pitch of, say, 80% if that maintains an RPM that is at the top end of the recommended? Or are you always faster at a pitch of 100%, just knowing that you may be frying your engine if you rev too high?

Also, I assume that lower prop pitches which lead to lower RPMs should should prevent engine overheating, right?

ZG77_Lignite
01-10-2005, 10:29 PM
The 'Airwarfare' site can be confusing, it leaves out some important aspects. Try these for more correct details: http://people.ee.ethz.ch/~chapman/il2guide/cemguide/proppitch.htm , http://www.avweb.com/news/columns/182082-1.html .

Regarding your questions, they depend completely on the aircraft you are flying (more specifically, the type of prop control system). The automobile analogy is really defiecient for most types of pitch control systems in the game.

For question #1 (optimum/safe RPM), this is automatically done on the most common system, the Constant Speed Prop (CSP). What you describe IS necessary for Bf-109 series in 'manual' mode (BoB era control, later aircraft retrofitted with an 'automatic' control system that adjusted prop pitch, well automatically). For CSP, maximum horsepower is achieved (and thus maximum 'thrust') at '100%', &lt;-- '100%' refers to an engine RPM setting for CSP's (as opposed to a direct blade angle control, such as in Bf109's in 'manual').

Question #2, Lower RPM's alwayse result in less overheating (as well as less horsepower output), it just depends upon which prop system your aircraft uses on how you (the pilot) achieve this. For example, Fixed Props (TB3, P.11c, etc) require a reduction manifold pressure (throttle), and possibly (probably) a reduction in speed to lower the engine RPM.

drose01
01-11-2005, 07:22 AM
Thanks for the links and reply, but I am still confused, especially when that first link told me that the "prop pitch heads up control does not actually indicate true prop pitch" or something like that.

I'm sorry but I also am left confused by your answer to my question #1, which can be boiled down to: does going over the redline in RPMs make you go faster or slower?

Johan217
01-11-2005, 08:05 AM
A related question:

In the early versions of the game, the radiator settings for the IL2 worked the other way around: i.e. the "open" setting meant in fact closed radiator. Is this still so in PF?

ZG77_Lignite
01-11-2005, 10:38 AM
Drose, my apologies, it is a confusing subject. It is really important to narrow down what aircraft (or more specifically which prop control system) you are using, there are 5 (arguably 7+, now) seperate systems, all of which operate differently. Depending upon the aircraft, the '100%' indication does not normally have anything to do with the actual blade angle on the prop, but refers instead to RPM (percent of available RPM)

But to try again to answer your question, in PF going over the rated ('redline' as you put it) RPM may (this is argued back and forth, it is not technically realistic) provide a small increase in power, but engine damage is also very likely to occur. Note this is not really possible on the most common system, the Constant Speed Prop.

Johannes, I believe it has been determined that the Il-2 now operates as other aircraft; closed=closed/armoured, open=airflow, but I'm not sure it has been proven definitevly. I think Oleg stated this, it was simplified due to the considerable confusion on the subject.

drose01
01-11-2005, 12:05 PM
Thanks for the reply, I understand you now.

The aircraft that I have been flying mostly is the P51, where the redline is about 2500 RPM. With throttle 100% and prop pitch 100%, at level flight RPMs usually get to 3000 RPM or higher, and the sound becomes noticeably higher pitched. I usually decrease prop pitch to keep RPMs at 2500 or so, but wonder if, in a real jam where I need as much speed/power as possible, I should leave the pitch at or near 100%.

I also fly the Spitfire, and although the same questions apply, I am not sure where the RPM "redline" is.

I do also fly Me109s, FW190s, La's and Yaks,...and P47's of course...

Is it really true that these planes are not comparable for the purposes of learning how to optimize prop pitch?

Johan217
01-11-2005, 12:37 PM
Great info http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

ZG77_Lignite
01-11-2005, 07:59 PM
That tells us (me) what we need to know. The P-51 uses a Constant Speed Prop. It automatically adjusts itself (its propeller blade angle) to maintain a given RPM (it was the most common WWII 'system', just as it is the most common 'high performance' system of today).

So, in a P-51, you (the pilot) Can Not directly influence Propeller Pitch (the blue text on the screen is a mis-leading generic term, they had to use Something). What you Are directly influencing, is the RPM of the engine; again, the prop will adjust itself automatically to maintain your RPM settings (for any given speed), to its best ability (its best ability in FB/PF is notably better than real-life(tm), but thats a whole different story).

So, for the P-51, you achieve the most horsepower (maximum 'thrust', for a given manifold pressure) at '100%', which happens to be about 3000RPM or so. If you are only flying at 2500RPM, you are flying at a decreased power setting (not best speed), though you are saving engine (overheat).

P-51 power settings go something like this:

Climb/Combat: 3000RPM/67Hg MAP (manifold pressure)
Fast Cruise/Normal Climb: 2500RPM/47Hg MAP
Economy Cruise: 2300RPM/41Hg MAP.

It just so happens the Spitfire uses the same engine, and has the same RPM settings (the Brits don't use Hg, or inches of Mercury to define MAP, but you can guess close enough for a corresponding MAP setting, or see below for Spit MkIX).


Regarding the differences in aircraft, they are extreme, and noticeable.

Try a Me109, set it to 'manual mode' (check control assignments for keystroke) and you'll note the difference immediately (possibly when your engine blows).

Try a P.11c (Polish) for a Fixed Prop, your engine RPM will vary depending upon your airspeed (climb/dive) because the Fixed Prop is locked at a given angle and is only most effecient for One speed (normally a nice fast cruise speed).

Try a FW190 in the default 'automatic' mode, you can't adjust the prop pitch or the Engine RPM, at least not seperate from the manifold pressure (MAP), because it automatically sets an RPM/MAP/Fuel Mixture for any given throttle setting (and is a CSP on top of that, so it is constantly adjusting prop pitch for your given speed, watch the 'prop pitch clock' in the lower center/right to see how blade angle adjusts to speed changes). The late model Spitfires (MkIX) has a linked throttle (MAP) and RPM lever, and operates similar to the FW190 (different from P-51).

Whew, hope that helps. Maybe somebody else will explain how to control the Me109 in 'manual' (it operates somewhat similar to FW190 in 'automatic'), it actually is a bit like a manual transmission in a car (but I still think its not good to think of it that way).

WTE_Galway
01-11-2005, 11:58 PM
with regard to the Radiator side of things:


- the more open the radiator cowl the better the cooling
- on SOME planes, the more open the radiator cowl the worse your top speed
- on SOME planes, the more open the radiator the worse the low speed handling (lagg is good example of this)
- "auto" simply means higher the throttle the more the cowl is shut off (it is NOT temperature controlled)
- on SOME planes an "open" cowl makes you more vulnerable to oil cooler and engine damage from flak or enemy fire

WTE_Galway
01-12-2005, 12:05 AM
oh yes .. the 109

apart from important exceptional circumstances like takeoff and steep dives .. the throttle is "set and forget" basically choose your throttle setting (I use 85% cruise 105% combat)and leave it alone.

Now just use pitch to keep revs at around 1800 to 2000 in cruise and at optimal power just under redline (depends on the model of 109) in combat

Generally manual pitch on a 109 is too much hastle to bother with .. however early emils of the BoB period were all manual so if y are flying a BoB scneario manual pitchj is historically correct.

Daiichidoku
01-12-2005, 01:54 AM
Great info, all

WTE Galway, I didnt know about the "auto" rad setting, I always assumed it was temp controls, like a thermostat, thanks for the tip

Curious, though....is it perhaps like the Meredith Effect, because I notice that often when I close the rad, IAS drops a few kph, but when I open it up fully, IAS actually increases...wouldav thought the drag from an open rad would slow the plane..unless, as I said, it has to do with the Meredith Effect, and I am getting extra thrust from a hot engine