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XyZspineZyX
07-25-2003, 07:27 PM
I'm afraid to ask as there has been tons of discussion on this, but alot of the articles I've read don't summarize it well with regard to FB and some even seem to contradict themselves.

These are the variables I see with regard to prop pitch. If possible, please correct me if I have one under the wrong category.

Blade PARALLEL to air flow
Fine setting
FB setting 100% (key 0?)
cruise setting
least resistance to air
gives faster top speed in dive and straight and level


Blade PERPENDICULAR to air flow
Coarse setting
FB setting 0% (key 1?)
Takeoff, climg, acceleration, most combat
most resistance to air, cuts througth air
gives slower top speed
Can overrev engine in dive at 100% throttle


Are these right?

XyZspineZyX
07-25-2003, 07:27 PM
I'm afraid to ask as there has been tons of discussion on this, but alot of the articles I've read don't summarize it well with regard to FB and some even seem to contradict themselves.

These are the variables I see with regard to prop pitch. If possible, please correct me if I have one under the wrong category.

Blade PARALLEL to air flow
Fine setting
FB setting 100% (key 0?)
cruise setting
least resistance to air
gives faster top speed in dive and straight and level


Blade PERPENDICULAR to air flow
Coarse setting
FB setting 0% (key 1?)
Takeoff, climg, acceleration, most combat
most resistance to air, cuts througth air
gives slower top speed
Can overrev engine in dive at 100% throttle


Are these right?

XyZspineZyX
07-25-2003, 07:29 PM
Back to front in FB - Coarse is Fine and Vice-Versa.

JG5_UnKle

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XyZspineZyX
07-25-2003, 07:46 PM
In my experiance in FB 100 pp is like first gear in a car
just keep that in mind for the German ac

This concept doesnot seem to hold water with the Russian or American or Brittish AC altho I think that certain of these ac fly better @ 90 or 85 pp in FB



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XyZspineZyX
07-25-2003, 07:46 PM
I'm in no way an expert, and have somewhat limited experience with IL2/FB compared to most here, so take my answers with a grain of salt.

- Blade PARALLEL to air flow
- Fine setting
- FB setting 100% (key 0?)
- cruise setting
- least resistance to air
- gives faster top speed in dive and straight and
- level

As far as I know, lower (ie: coarser) prop-pitch settings make for lower fuel consumption and are therefore more appropriate for cruising. The fine setting (100% until the patch) gives you lower prop-pitch (ie: prop bites less air) but higher RPMs. Finer settings seem to give good results in the Bf109 (might apply to other German planes as well)for climbing and speed in general. Just watch out because it's easy to overrev and blow the engine that way. Before diving, reduce pitch or turn auto pitch back on.

- Blade PERPENDICULAR to air flow
- Coarse setting
- FB setting 0% (key 1?)
- Takeoff, climg, acceleration, most combat
- most resistance to air, cuts througth air
- gives slower top speed
- Can overrev engine in dive at 100% throttle

Like I said, use this to conserve fuel on the way to your target. Coarser settings mean the prop bites more air, but give you lower engine RPM. I think you'd be hard pressed to overrev the engine in the coarse settings because, like I said, these are the settings that give the smallest engine RPMs.

Hope I helped /i/smilies/16x16_smiley-very-happy.gif

XyZspineZyX
07-25-2003, 07:54 PM
tmdgm1

What you think should be correct. The problem is FB has it backwards, and I don't see it changing in the patch either. At least in the beta 08 it didn't.

Da Buzz
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XyZspineZyX
07-25-2003, 08:04 PM
Ok, I think I'm still confused. Which part is backwards in FB? Just change the word coarse to fine and keep everything else? Is what I wrote correct in a real plane?

XyZspineZyX
07-25-2003, 08:07 PM
Yes. 100% would be like 1st gear in a car. If you like to look at it that way.

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XyZspineZyX
07-25-2003, 08:28 PM
If 100% is like first gear in a car, that must be Coarse setting with blade PERPENDICULAR to air flow, right? So FB should be like this.


Blade PARALLEL to air flow
Fine setting
FB setting 0%
cruise setting
least resistance to air
gives faster top speed in dive and straight and level


Blade PERPENDICULAR to air flow
Coarse setting
FB setting 100%
Takeoff, climg, acceleration, most combat
most resistance to air, cuts througth air
gives slower top speed
Can overrev engine in dive at 100% throttle


Bascially just changed the % setting. So for Takeoff, climb, accleration, I want 100% prop pitch in FB? I've seen so many posts say 0% is first gear. In fact, the below quote from the article is from Tailspins site

. At 100% the blades bite or grabs the air the least. The angle of incidence is displayed on the right hand side of your screen notated as 100%, 95%, 90% on down to 0% at 5% increments. 100% is the easiest for the engine to turn and grabs the least air. As you change from 100% to 95% the blades bite more air and takes more horsepower to turn the prop. Prop pitch set at 95% and 2,800 rpm's is going to move the aircraft faster through the air than 100% and the same 2,800 rpm's.



Tailspins implies 100% is fine pitch PARALLEL to air flow, least bite of air, and more for cruise.

XyZspineZyX
07-25-2003, 08:32 PM
What Tailspin is saying is correct. What you have is wrong.

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XyZspineZyX
07-25-2003, 08:36 PM
The same principal applies to a boat/ship as well...

If you take a prop/screw off and put it flat on the ground so the blades themselves are parallel to the ground you'll see the blades are fixed at a certain angle. The flatter or more parallel the blades are to the ground, the lower(in FB higher) the pitch setting is RELATIVE TO THE GROUND. The more upright or perpendicular the blades are to the ground the higher (in FB lower) the pitch setting, RELATIVE TO THE GROUND.

In FB, 100% would mean the prop blades are FLAT, or parallel to the ground, and 0% would mean they are standing straight up.

100% in FB would mean the blades would "catch" less air and therefore spin faster at a given power setting. Meaning, better low end torque, but lower top speed.

The reverse of this would mean (in FB terms), the lower the pitch setting, the more air the blades will "catch", the less low end torque, but higher top speed, given enough power can be applied.

I think thats it, anyone find fault with this please let me know! /i/smilies/16x16_smiley-wink.gif

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XyZspineZyX
07-25-2003, 08:41 PM
Yes for take off 100 is ok but just as in a car your only in 1st gear/corse PP for a mater of seconds then you shift too 95pp 90pp 85pp my wheels lift from earth @85pp

then I level out & maintain 85pp untill im @ or near 400kmh maybe 450kmh then I change too 80/75pp I start my climb @ 15 degree's angle or so....

If I start too lose to much speed Ill level out down shift & rebuild my speed to around 500kmh this time & continue climbing

Your above post looks true


Good Luck

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XyZspineZyX
07-25-2003, 08:47 PM
Murdoc.,

You'll see a change in the Dora after the patch. It seems the manual prop pitch is more of a fine tuning tool now. You can fly 0% to 100% on level flight without hurting the engine. The 109's still work the same, and you have to keep your eye on the rpm. I'm not sure if this will change in the final version.

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XyZspineZyX
07-25-2003, 08:54 PM
Hmmm I wonder if thats good or bad, since I use the 5%incriments for the most part my wheel on my ch stick is way too sensitive for fine tuning PP /i/smilies/16x16_smiley-sad.gif

I might have to call ch & figure a way to make this wheel lots less sensitive Ive tryed many settings in the control manager & nothing seems to adjust the pp smoothley its imposible to fine tune with it !!!



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XyZspineZyX
07-25-2003, 08:56 PM
This actually works for you. It's not as sensitive now, so 5% jumps are fine.

Da Buzz
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XyZspineZyX
07-25-2003, 09:10 PM
Still confused. If 100%, coarse, perpendicular to air flow, catches least air, why would that be good for taking off? I would've thought for takeoff/climb accleration, you would want to catch the most air, hence push more air so use 0% setting, fine, parralel to air, catches most air.

XyZspineZyX
07-25-2003, 09:15 PM
In FB: 100% is full FINE pitch ie. tiny slices taken out of the air. Use in takeoff or climb. NOT in dive or you will over-rev your engine.

As you go down in percentage you are COARSENING the pitch. Coarsening to the pitch to varying degrees along with throttle adjustments can yield different results: max cruise speed, max fuel economy cruise, and very coarse with chopped throttle for steep dives so as not to let your engine run away.

XyZspineZyX
07-25-2003, 09:25 PM
tmdgm1

You can't take off in your car in 5th gear can you? You need to build up some speed before you can start grabbing more air with the prop.

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XyZspineZyX
07-25-2003, 09:34 PM
tmdgm1,

When you write perpendicular to air flow do you mean relative to the prop blades' vector or the planes'?



100 percent for prop pitch in IL2 means either 100 percent rpm setting or 100 percent prop angle depending upon which plane is being flown.

The 109s with manual prop are direct prop angle readings, meaning that 0 percent corresponds with coarse pitch and 100 percent is fine pitch. Coarse pitch relative to the planes' vector is approaching parallel. Fine pitch relative to the planes' vector is approaching perpendicular.
0 percent or Coarse pitch relative to the prop vector is perpendicular or at a high angle of attack. Fine pitch relative to the prop vector is 100 percent or parallel; low angle of attack.

On planes with constant speed props such as most Allied planes the percentage shows an RPM settting. 0 percent is a low RPM settting and 100 percent is a high RPM setting, the prop angle is automatically adjusted from coarse to fine depending upon the conditions present required to achieve the desired RPM.

On planes with rpm (prop) adjustment levers that are linked to the throttle such as the automatic constant speed props in the later 109s the game no longer shows a prop percentage even though throttle changes will also change RPM settings.

Prop angle and prop drag or bite is relative to the planes velocity, therefore any thoughts of how much air the prop will catch depends also on the planes velocity as much as does the relative prop angle.




JG14_Josf

XyZspineZyX
07-25-2003, 09:46 PM
JG14_Josf

I have a bad habit of thinking everybody is thinking of a 109 when they ask about prop pitch settings. Some of them are talking about constant speed prop planes, and it just screws everything up in trying to explain it to them.

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XyZspineZyX
07-25-2003, 09:50 PM
I think I got it. Had to understand the theory of the air flow. The overrevving in dives under full fine pitch 100% is due to the faster speed and air flow pushing the fine prop pitch faster, higher RPMs, because the fine prop pitch has more surface area exposed to the oncoming air? Is that right?

Thanks for all the help.

XyZspineZyX
07-25-2003, 09:53 PM
The work of a prop is less in a dive, because it doesn't have to pull the full weight of the plane. Just like a car going downhill../i/smilies/16x16_smiley-wink.gif

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XyZspineZyX
07-25-2003, 10:58 PM
See if I've got this correct. If you're on a bike, you start off with the chain on the biggest sprocket on the back. If you're shooting down a hill with the wind behind you it feels more comfortable with the chain on the smallest sprocket. Imagine how you legs would be going round if you had stayed in the first gear. They would be over-revving and you would be overheating. For the first 'easiest' gear, think 100% prop pitch, and for the stiffest downhill gear, think 50-60%. Keep the rate of pedalling fairly constant, as in revs, and you'll rarely need to use the draggy radiator. Roughly right?

Is a different approach needed for Russian aircraft, or do they have different rev criteria?

XyZspineZyX
07-25-2003, 11:16 PM
Hey Buzz, you said that after the patch, the Dora's manual prop pitch will be "more of a fine tuning tool . . . You can fly 0% to 100% on level flight without hurting the engine."

I noticed that in the Beta v.8. But is that the way it will be released? I thought it was a bug.

I fly manual pitch all the time. With the v.8 Dora, I had a terrible time accellerating to catch a flight of IL2s. I was so bummed, I removed the v. 8 patch right then and there. /i/smilies/16x16_smiley-sad.gif

If it's the same with the patch, I'm afraid the Dora will be eviscerated.

S!

XyZspineZyX
07-25-2003, 11:38 PM
Pushing the prop can be done at any normal prop angle setting, this is called windmilling and is dependent upon the relative velocity of the prop, the plane and the atmosphere.

Windmilling occurs when the prop has a negative angle of attack relative to the atmosphere. The actual blade angle alone set by the pilot or governor, be it full coarse or full fine or any setting in between, has no bearing on weather the blade is creating thrust or nuetral or being driven by windmilling, what matters is the relative velocity of the atmosphere.

What happens when the plane if flying backwards?

Prop pitch is significant only relative to airflow.

A prop is a wing. Changing the prop pitch is like moving the elevator on a plane to increase or decrease the wings angle of attack relative to the atmosphere. Windmilling is analogous to flying upside down. The lift is on the other side of the wing.

When a twin engine plane has one engine not running,the pilot is advised to feather that engine (place the prop blades parralel to the planes vector) otherwise the relative angle of attack of the atmosphere to the prop blades will drive the blades, the blades will windmill, and this causes drag. One wing having an engine producing thrust and one wing with no thrust is bad enough, but when one wing has thrust and the other has a dragging windmill istead of an engine producing thrust then the plane may be unflyable with a tremendous yaw as the driving engine tries to fly around the windmilling engine. Feathering the prop reduces drag to a minimum on the engine that has failed.

Windmilling occurs when there is no more thrust, when the prop is not feathered, and the relative air vector actually drives the prop by creating lift on the opposite side of the prop blades.

This can occur even when the engine is running at full speed, even when the blades are at full coarse, or full fine, as long as the relative air velocity is greater such as a high speed power dive. In such a situation the prop acts like a dive brake, no longer does it produce thrust, instead the relative air velocity is driving the blades and this work produces drag.

The only way a prop can neither produce lift nor drag is when the prop is perfectly parallel to the air flow such as a feathered prop (which may not actually be without some minor pressure differential)

I am thinking out loud and understand that the physics involved is very complicated, however the subject of prop pitch use in IL2 need not be so difficult to understand. What is important is to identify first what type of prop pitch is used for the plane being flown. Then it is important to understand how any adjustments can maximize performance.
In the case of most planes presently in IL2/FB the prop adjustment is set at 100 and forgotten.

Oher planes that have manual prop control can be controled with an analog device; another throttle or dial.
These manual prop planes can then be adjusted on the fly with the throttle kept at 95 percent (no overheating). Soon the pilot will see clearly how more pitch percentage allows the engine to rev higher and lower pitch percentage slows the engine down. After awhile of flying around with prop pitch being adjusted constantly the pilot will note how low percentage prop adjustment is used when the plane is flying fast and high percentage prop adjustment is used when the plane is flying slow. When flying slow (hard climbs and turns) the enine tends to slow way down prompting the pilot to increase prop percentage. When the plane is flying fast (dives and prolonged level cruise) the pilot is prompted to reduce prop percentage to keep the engine from over reving.

If this method is done to fly the plane using an analog prop control it will soon become clear the effects of prop pitch on performance. The Auto prop planes do the work automatically, again they allow maximum performance when set to 100 percent.





JG14_Josf

XyZspineZyX
07-26-2003, 01:48 PM
ok, one more dumb question. When do you ever use prop pitch between 0% and say 50%? It seems like everyone says go down to 50% or 60% when in a dive or cruise. And 0% would be close to feathering so I know when you feather a prop. But when would you operate between the 0% and 50% range? I would think if it's like a car, once you got over say 250 mph, wouldn't you want to go as low as you can so the prop can catch more air in the coarse position?

XyZspineZyX
07-26-2003, 02:43 PM
Dunno if it was mentioned but in russian airplanes it's all about the RPM.
The best RPM for speed.
The best RPM for economical
etc

Pitch and throttle are two ways to affect the RPM.

- The more pitch (less procentage) the less RPM
...and...
- The more throttle the more RPM

So using these two (pitch/throttle) together u set the planes RPM for the desired speed and fuel consumtion.

Check the pdf-file on your second FB-disc for best RPM for each plane.

For instance if the best RPM for a Yak for speed is 2800 u might have to adjust throttle and pitch to get 2800 RPM.

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XyZspineZyX
07-26-2003, 04:07 PM
Questions are not dumb.


Auto prop or constant speed prop planes where prop percentage is actually an engine rpm setting will not likely use 0 to 50 percent prop settings because those settings result in low engine rpms. It is possible that the game models fuel economy at low engine rpms and that is one possible use for low prop settings for constant speed prop planes. Another possible use of low prop settings for constant speed props is to force an overshoot. Selecting a low rpm setting would help decelerate the plane.

Some planes have direct prop pitch control like the early 109s (this is reported to be changed in the patch to an automatic prop governor) and this manual prop pitch control allows the pilot to move prop angle from full coarse or 0 percent to full fine or 100 percent at any time without having to adjust any other control or without having pilot input being governed by any other mechanism.

The situation with the early 109s with their manual prop control is not the same as the other planes with respect to the prop percentage readout in the game.

The early 109s, if flown level at 95 percent throttle with the radiator doors closed will continue to accelerated until reaching it's top speed in level flight. If the pilot selects a 100 percent or full fine prop setting in level flight at 95 percent throttle, radiator doors closed, flaps up, wheels up, the plane will accelerate until reaching it's top speed in level flight however at this prop setting the plane will soon be going fast enough to allow the engine to over rev. If the pilot allows this condition to continue the engine will be damaged due to excessive engine speed. In order to keep the engine from going too fast, to keep the engine rpm at the desired safe level of 2500rpm, the pilot can keep the prop angle at 100 percent and close the throttle or he can keep the throttle open and move the prop angle to a higher angle of attack such as 50 percent prop pitch. In either case the engine will slow down. If the pilot closes the throttle, the plane will no longer accelerate, if the pilot moves the prop blade angle to a higher angle of attack (lower percentage) the plane will continue to accelerate.
If the plane continues to accelerate the engine will continue to rev higher and higher until the engine exceeds the safe limits of engine speed 3000rpm. The pilot can then close the throttle or dial in more prop angle, again closing the throttle slows the plane down and moving the prop angle to a higher angle of attack (lower percentage) will keep the plane accelerating, both closing the throttle and increasing the prop angle slows the engine down to 2500rpm. The 109E-4 in IL2 will accelerate in level flight at 95 percent throttle with the radiator doors closed, flaps up, and gear up with 0 percent prop pitch until the engine over revs past 2500rpm, and at this point the pilot only has the choice of closing the throttle to slow the engine down since the prop is set to 0 percent or full coarse already. No longer can the pilot slow the engine down with more prop pitch (lower percentage) because at 0 percent prop pitch in the 109E-4B the limits has been reached, the maximum coarse setting is not enought to keep the engine in the safe operating range or rpm in level flight.

So here is a situation where 0 percent prop pitch is used in IL2. Flying the manual prop controled planes fast require very low percentage prop pitch settings. If the pilot in a 109E-4B keeps his speed at or above the top level speed he will always have his prop pitch set at 0 and he will have to keep his engine from over reving by closing the throttle.

If the 109 pilot, trying to keep his speed at or above level top speed, is forced into a situation where the airspeed falls below this top level speed then the engine speed will also fall below the desired rpm. When the pilot, in a manual controled prop plane like the 109E-4B is in a situation where his plane is slowing down, where his plane is set at 0 percent prop pitch and the throttle is set at 95 percent, the engine will slow down as the plane slows down. When the engine slows down to less than 2100rpm the engine will be turning too slow. At 2100rpm the pilot must do something to increase engine speed, he can stop turning or dive and the plane will again accelerate or he can open the throttle to 110 percent. Openning the throttle is a temporary fix since althought the engine will speed up it will also overheat. The pilot can also change the prop angle of attack by going from 0 percent to a higher percentage setting (finer pitch). As the plane and engine decelerates in a climb or turn the pilot can adjust the prop and therefore increase the engine rpm.

What I have just described in answer to the question "When do you ever use prop pitch between 0% and say 50%" is only for manual pitch prop planes and if the pilot trying to understand the question were to go for a test flight with the 109E-4B, and if the pilot were to fly around with 95 percent throttle with the radiator doors shut and if the pilot has an analog prop pitch control, then the pilot could see for himself the relationship between engine speed, airspeed, and prop angle. If the pilot maintains the optimum engine rpm at 2500rpm he will find that the faster the plane goes the lower the prop setting will be needed to maintain the desired rpm, and the slower the plane goes the higher the prop setting will be needed to keep the desired rpm.


Why?

When the plane is sitting stationary on the runway the pilot can test his engine by reving it up with the brakes on. The airspeed indicator reads zero. If the pilot does not pay attention to the prop blade angle he may not be able to rev the engine to a desired rpm, let's say he wants to rev to 2300 rpm to test first one magneto and then the other magneto. (this works in IL2 with the 109E-4B) With both magnetos selected the engine should rev to 2300 rpm and the engine rpm should drop when the pilot switches from both magnetos to one magneto and then rev back up when the pilot selects both magnetos again, and then drop when the pilot selects only the remaining magneto. The pilot then knows that each magneto is working but when both magnetos are working together the engine runs fastest.
So back to the pilot that does not have the proper prop pitch setting needed to test his magnetos. Let's say the prop was set at 0 percent (full coarse). The pilot selects both magnetos, applies the brakes, opens the throttle and finds that the engine only goes to 1900 rpms and no more.
The prop blade angle is at the maximum coarse setting and therefore at the highest angle of attack possible since the plane is not moving. The engine does not have enough power to turn the blades at that severe angle of attack.
The pilot trying to check his magnetos will have a mechanic outside waving his arms. There is a knock on the canopy. A sign is waved. "Check your prop setting"
The pilot then realizes that in order to do his magneto test the prop blade angle must be set to a finer pitch and allow the engine to turn faster.
When sitting on the ground on a calm day the prop blade angle of attack will be the greatest possible and therefore the highest load on the engine, because the plane is not moving there is zero velocity relative to the atmosphere. Once the plane starts moving the prop blade angle of attack decreases because the relative velocity of the atmosphere increases. Even if the pilot maintains the same prop angle setting the angle of attack decreases as the plane accelerates. As the angle of attack decreases so does the load on the engine, because it is easier to turn a prop blade that is at a lower angle of attack relative to the atmosphere.


There are no stupid quiestions. If I continue to answer this type of question, to the best of my ability, then I may learn both; how better to communicate and how this stuff works, or I could just remain relatively ignorant.

Ignorance is bliss http://ubbxforums.ubi.com/infopop/emoticons/icon_smile.gif

Ahhhhhhhhh

I think I'll take a nap.





JG14_Josf

XyZspineZyX
07-26-2003, 04:09 PM
Good post Josf!



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XyZspineZyX
07-26-2003, 04:35 PM
tmdgm1 wrote:
- ok, one more dumb question. When do you ever use
- prop pitch between 0% and say 50%?


In a dive the lowest pp I use is 45 in 109's & 55/50 in the Dora

with the throttle cut back to 50% or less sometimes 5%

I dont like to travle over 800kmh makes for a hard time shooting & scoring a hit

Again the easiest way to consider the pitch is like a cars gears if your KMH is high like 700 800kmh you would use a smaller pp # say 45/50/55 when @ 500kmh 60/65/70 300kmh and less 80/85/90 depending on what your doing

Now I told you all my secrets /i/smilies/16x16_smiley-happy.gif

Show me the Money !!!



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I am the Alpha and the Omega
the Begining and the End.</div> <center>

<center><FONT COLOR="white">ӚFJ M œ R D ˜ ӡ[/i]</FONT>

XyZspineZyX
07-26-2003, 05:43 PM
JV44Rall

I really don't know if it's a bug on the Dora. It does seem to work in a weird way. I prefer the way manual pitch works on the 109's.

Da Buzz
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F4..The Best BF109

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