109's kill ratio (all variants from B to K)

[GScholz]

Originally posted by F4UDOA
Gsholz,

If you are insulted you should be.

Insults are uncalled for in a serious debate no matter what.

Originally posted by F4UDOA
1. I didn't say a P-51D will out accelerating or climb a 109K-4/G10. My point is that at a reasonable fighting weight the advantage of the 109 is reduced to being moot. When your inside of combat range low speed accleration/climb will not save you unless the differance is vast.  And that is without 150 octane fuel.

No, you said:

This is strictly thrust vrs drag. How much thrust is required to overcome X amount of drag. If the P-47C can accelerate as well as a P-38F then a Mustang can do at least as well as a 109. I can't do the math right now but I will shortly. BTW at sea level the Mustang is at least as fast with less HP required. The Mustang is designed for low cruise drag thats why it accelerates through those speeds ranges so well.

and ...

Most importantly. The K4 has the advantage of Nitrious and other fuel additives at altitude but you are excluding the use of 150Octane fuel in the Mustang which was common. With 150 octane fuel the P-51D was much faster than the K-4 and would climb as well even with heavier loads.

So you did say the P-51 could out accellerate the 109 and you did say the P-51 could climb as well as the 109 with heavier load, indicating it could out climb the 109 with equal load.

The 109 could out climb any allied fighter at high altitudes also at speed, as Franz Stigler commented:

The K-4, he said was very much like the G yet could leave all other fighters behind in climb. In control feel he said the K felt identical to the G. He described on many occasions where they would just bank away from the fighters and climb away from them.

Originally posted by F4UDOA
What I did and will repeat is that differance is not so large when the P-51 is fighting at it's design weight. If you read an actual document instead of the comic books will Colonel Klink on the cover you will find things like "Empty weight, Design weight and max loaded weight". That design weight is at about 9300LBS in the P-51 and you have an agile fighter.

You persist in being rude. Even with no fuel and no ammo the P-51D is still considerably heavier than a fully loaded 109, and the P-51 has less power. At a very light configuration I have no doubt the P-51 had a better instantaneous turn rate, however it lacked the power to match a 109 in sustained turn and at any case a 109 would just spiral climb above the P-51 in such a case.

Originally posted by F4UDOA
2. You or Isegrem have yet to produce one viable document on the K-4 or G10 showing performance. Specifically roll rate which you claim is good despite having shown to be poor in multiple AFDU test against various aircraft.

I have no documentation on the 109G10 or K4 except what HTC has posted (and I think their sources are good), and Isegrim's charts are disputed. That's why I said this remains unresolved.

Originally posted by F4UDOA
3. I am a F4U proponent. I would much rather post F4U data which I prefer to the pony as I prefer the 190 to the 109.

I know, but this is a debate on the 109 and P-51.

Originally posted by F4UDOA
4. If you can't read the column where it shows 80 GPH at 403MPH at 30,000FT you are either hard of sight or in denial. The column is difficult to read but not impossible.

Do you have that chart in higher resolution? I'd like to read the "fine print" as well.

Originally posted by F4UDOA
Challenge

Give me a senario at what altitude where a P-51D and 109K-4 Dogfight at any altitude how the 109 wins? The only possible altitude where the 109 could have an advantage is at sea level because the Pony could not dive away if it lost the advantage. And at sea level the P-51D can turn well inside the 109.

By 1944 it (the 109) was already obsolete due to an airframe that did not allow for major modifications. It had no range, load carrying capability and had very limited maneuverability at speed.

Basically any engagement between the 109G10 or K4 against a P-51D would in most cases end up with the P-51 being shot down or running. A 150 octane British Mustang with -7 Merlin would have a better chance against a 109G10. If the P-51 runs the 109 would in most cases let it go since the 109's job was to attack bombers or protect "formation destroyers". If the 109 did decide to run the Mustang down it could do so since the P-51 cannot run on full throttle for long due to fuel considerations and at low alt (after diving away) is not fast enough to run from a high 109. In any case, making the P-51's run from the bombers they were meant to protect would be a victory for the interceptor 109's, and would allow the 109's or other aircraft to attack the bombers undisturbed.

[Neil Stirling1]

Adam you got your P51B data from here

http://www.fourthfightergroup.com/eagles/spit14speedchart.jpg

Notice the full throttle height for speed is about 8400M, your diagram 8400M, you will notice from the original document that the engine used was the -7 Merlin, Military power is +15lbs (61"hg)

http://hometown.aol.co.uk/JStirlingBomber/Pilots+notes.jpg

Military power full throttle height with the -3 Merlin is about 9450M as you can see here.

http://hometown.aol.co.uk/JStirlingBomber/Mustang+4.jpg

Pilot notes Mustang III V.1650-3

http://hometown.aol.co.uk/JStirlingBomber/3+Merlin.jpg

Some Mustang III Climb and Level speed performance trial data for you. Mustang III F.X 953 Feb to May 44.

http://hometown.aol.co.uk/JStirlingBomber/3+climb.jpg

http://hometown.aol.co.uk/JStirlingBomber/3+speed.jpg


How about changing your climb chart, use a K4 with 1.8ATA Vrs a P51 using 67"hg.

Neil.

[GScholz]

While searching for the drag coefficient numbers and calculations for the 109 and P-51 I stumbled upon this interesting article (especially for you Nomak):


Why Col. "Kit" Carson was wrong.

[GScholz]

The drag coefficient is a number that aerodynamicists use to model all of the complex dependencies of drag on shape, inclination, and some flow conditions. This equation is simply a rearrangement of the drag equation where we solve for the drag coefficient in terms of the other variables. The drag coefficient Cd is equal to the drag D divided by the quantity: density r times half the velocity V squared times the reference area A.

Cd = D / (A * .5 * r * V^2)

This means that actual drag is:

D = Cd * (A * .5 * r * V^2)

Now, from this thread we know (undocumented though) that the P-51D had a Cd of 0.0176 while the 109K4 had a Cd of 0.0185 to 0.0190.

r and V are variables we can set to be identical for comparison purposes, however we still lack information on the reference area A.

Notice that the area (A) given in the drag equation is given as a reference area. The drag depends directly on the size of the body. Since we are dealing with aerodynamic forces, the dependence can be characterized by some area. But which area do we choose? If we think of drag as being caused by friction between the air and the body, a logical choice would be the total surface area of the body. If we think of drag as being a resistance to the flow, a more logical choice would be the frontal area of the body that is perpendicular to the flow direction. And finally, if we want to compare with the lift coefficient, we should use the same wing area used to derive the lift coefficient. Since the drag coefficient is usually determined experimentally by measuring drag and the area and then performing the division to produce the coefficient, we are free to use any area that can be easily measured. If we choose the wing area, rather than the cross-sectional area, the computed coefficient will have a different value. But the drag is the same, and the coefficients are related by the ratio of the areas. In practice, drag coefficients are reported based on a wide variety of object areas. In the report, the aerodynamicist must specify the area used; when using the data, the reader may have to convert the drag coefficient using the ratio of the areas.

Does someone know the reference area used for the Cd of the P-51D and 109K?

[GScholz]

From nasa.gov

The drag area f is the product of the zero-lift drag coefficient and the wing area. The resulting number is of interest because it represents, approximately, the area of a square flat plate, or disc, held normal to the direction of flight, which has the same drag in pounds as the aircraft at a given speed and altitude. (The relationship is exact for a flat-plate drag coefficient of 1.0. According to reference 72, the actual drag coefficient of such a plate is 1.171.) For example, the drag area of the P-51 fighter is 3.57 square feet as compared, with, 12.61 square feet for the much smaller Fokker E-III of World War I. The improvement in aerodynamic efficiency over the 25-year period separating the two aircraft is obvious. Comparisons of the drag area of aircraft of different periods designed for the same missions can thus provide some indication of comparative aerodynamic cleanness or streamlining. Furthermore, the maximum speed is approximately proportional to the cube root of the ratio of the power to the drag area (ref. 90). The larger this ratio, the higher the top speed.

Note: Also know as "flat-plate area".

Ok, so the P51 (unknown model) had a drag area of 3.57 ft^2 according to NASA, while every other source I can find on the net says 4.63 ft^2 for the P-51D. Which is right?

Now if Isegrim's data on the 109K4 having a flat plate area of 0.294 m2 which is 3.163 ft^2 it would seem that the K4 indeed produced less drag than the P-51 despite having a higher Cd because of the difference in size between the aircraft.

Now, if these numbers are correct the 109K4 would be faster, accelerate faster and cruise more economically (with the same engine) than the P-51. HTC seems to agree with this since the 109G10 in AH is both faster and accelerates faster than the P-51, however the Cd and drag area of the G10 is not known to me.

[GRUNHERZ]

From behind the dark bushes:

But doesnt the Mustangs radiator design offset some of that drag by providing thrust?

[dtango]

GScholz:

Reference area used typically is the wing area in drag calculations.  (This gets interesting when you have aircraft that don't have "traditional" shapes with regards to lift generation! It's an interesting topic especially from a modern aerodynamics perspective and there are some interesting debates on this topic regarding which area to actually use for the calculations which is beyond the scope of my personal study.)

CD0 and total parasite drag comparisons - yes that was Isegrim's point he made and I corroborated it clarifying that what the data tells us is that the P-51 had a cleaner design vs. the K-4 but has a higher parasite drag because of the greater "wetted" surface area presented by P-51.

Flat plate conversion is based on the following equation:
FPA = CD0 * Ref Area

The NASA 3.57 sq ft vs. my 4.10 or the 4.63 you've seen is probably a difference in the ref area.  I'm guessing the 3.57 is based on some of the current thought in the aerodynamics field regarding which reference area to use - e.g. they may have substracted fuselage portion of the wing area etc.

So yes at equivalent airspeeds the K-4 has a lower parasite drag vs. the P-51D.

What does this mean?  At equal thrusts the plane with lower parasite drag would have a faster max level speed.

However a lower parasite drag doesn't neccesarily mean that a plane will out accelerate another, nor does it mean that a plane would cruise more economically.  

Aircraft acceleration is not linear and varies over a piston a/c's velocity envelope by the difference of power available - power required (total D * V).  

Regarding most economical cruise as being defined as maximum range or the best ratio of fuel burn to distance, for a piston a/c this occurs at the best L/D ratio for the aircraft or at the point of lowest total drag where induced drag and parasite drag are equal.


Grunherz:

Yes, the radiator design resulting in the Meredith Effect or ramjet thrust via the exhaust stacks for the P-51D does contribute but it's already shows up via the flight test data for the Mustang's top level speed.  Here's an interesting article on it all:
Meredith Effect on the P-51

Tango, XO
412th FS Braunco Mustangs

[Widewing]

Originally posted by GScholz

Does someone know the reference area used for the Cd of the P-51D and 109K?

In America's Hundred Thousand, Dean states that the flat plate of the P-51D is 4.10 square feet.

However, we can't rule out mitigating factors, such as the P-51's Merideth Effect radiator design and the clever use of boundary layer splitter to minimize drag associated with the radiator inlet.

These are some of the reasons that the P-51D, with considerably greater flat plate area than the Spitfire Mk.IX, was 30 mph faster on the same horsepower. The same can be said for the Bf 109G-2, which had, IIRC about 1,475 hp, but was about 35 mph slower than the P-51D. Both the late-war Spitfires and 109s needed far greater power than the P-51 to match or slightly exceed its level speed.

Years ago I read an article that discussed the Bf 109's drag issues. It did not employ the Merideth Effect radiator ducting, did not use boundary layer splitters and had all manner of protruding humps, bumps and scoops that contributed to a very high level of parasitic drag. I don't have a copy of the article, but is was based upon an engineering analysis performed at Langley Field in late 1945, including some wind tunnel runs. It was a Brit magazine, although I can't recall which one.

My regards,

Widewing

[F4UDOA]

Gsholz,

Since when does out accerate or out climb equal at least as well or as well?? If you don't want me to be derogatory then don't misquote me.

Also you should read Dtango quote very clearly.

What does this mean? At equal thrusts the plane with lower parasite drag would have a faster max level speed.

Widewing beat me to it but even the 109K-4 at sea level had 2,000HP and the P-51D had 1750HP and they both had the same top speed. So which aircraft had the higher drag?

Also your comment about the P-51D not being able to disengage at fullpower because it would run out of fuel is rediculous. Just think about that.

Do you even know what the fuel consumption of the 109K4 is? I do I have a entire document on it. The 109 had limited amounts of C-3(Nitrous) and MW-50. It would run out of those additives long before the Mustang would run out of fuel or overheat.

By the way by senario I meant offensive manuevers. My airplane will beat yours up does not count.

Also your sustained turn theory doesn't work if the other 109 has a higher stall speed than the P-51D. If the 109 is pulling max G then he is deccelerating. If the P-51D is not pulling max G the he can still accelerate and fly on the edge indefinetely without loosing E while turning inside the 109.

In other words if the P-51D has a 3G stall of 160MPH and the 109 has a 3G stall 170 MPH then the Mustang can fly 165MPH all day and turn inside the 109 while not burning E and the 109 will eventually loose speed and not be able to pull enough G to keep out of gun range.  This problem only gets worse when the 51 drops combat flaps.

[GScholz]

Ok Dtango you seem to be knowledgeable about such things (I'm learning as I go along ). Tell me which plane do you think would accelerate faster. The 7400 lbs, 2000hp, 3.163 ft^2 FPA Messerschmitt Bf109K4 or the 9000 lbs (light Pony), 1940hp (Merlin -7 on 150 octane),  4.61 ft^2 FPA North American Mustang IV (British P-51D)?





VS





WHO WILL WIN?

All this and more ... next on TOWNTALK with Dtango!

[GScholz]

Originally posted by Widewing
In America's Hundred Thousand, Dean states that the flat plate of the P-51D is 4.10 square feet.

However, we can't rule out mitigating factors, such as the P-51's Merideth Effect radiator design and the clever use of boundary layer splitter to minimize drag associated with the radiator inlet.

I wonder if the Meredith effect is included in the Cd/FPA calculations or not? The boundary layer splitters must surely be included since they are a normal part of the parasitic drag.

Originally posted by Widewing
These are some of the reasons that the P-51D, with considerably greater flat plate area than the Spitfire Mk.IX, was 30 mph faster on the same horsepower. The same can be said for the Bf 109G-2, which had, IIRC about 1,475 hp, but was about 35 mph slower than the P-51D. Both the late-war Spitfires and 109s needed far greater power than the P-51 to match or slightly exceed its level speed.

Years ago I read an article that discussed the Bf 109's drag issues. It did not employ the Merideth Effect radiator ducting, did not use boundary layer splitters and had all manner of protruding humps, bumps and scoops that contributed to a very high level of parasitic drag. I don't have a copy of the article, but is was based upon an engineering analysis performed at Langley Field in late 1945, including some wind tunnel runs. It was a Brit magazine, although I can't recall which one.

This is certainly true. However the 109K4, and to some extent the 109G10 as well, were considerably cleaned up aerodynamically compared to earlier 109G's, especially the 109G6. The 109K4 reintroduced the retractable tail wheel and had among other features completely covered wheel wells (like the P-51). The 109 was also a much smaller aircraft, even smaller than the Spitfire.

EDIT:

In this cutaway drawing you can clearly see how much more aerodynamic the 109K4 was, especially around the cockpit area.

[GODO]

Originally posted by F4UDOA
109K-4 at sea level had 2,000HP and the P-51D had 1750HP and they both had the same top speed. So which aircraft had the higher drag?

You should take also in consideration the propellor design, not only the "raw" HPs.

[mold]

Originally posted by Widewing
In America's Hundred Thousand, Dean states that the flat plate of the P-51D is 4.10 square feet.

However, we can't rule out mitigating factors, such as the P-51's Merideth Effect radiator design and the clever use of boundary layer splitter to minimize drag associated with the radiator inlet.

Yes I believe we can, because these things should already be accounted for in the flat plate area.  For our purposes, total drag is ultimately the only thing that matters--not Cd and not flat plate area, except when we can use such things to calculate total drag.  FPA is just a ref number, and Cd is calculated from that.  No extra information here, really.

[dtango]

Hehe Gscholz, the answer regarding acceleration is I don't know !  Seriously though, I don't have enough data to make an accurate assessment.

2ndly you can compare acceleration either as average acceleration or instantaneous acceleration and have different answers.

With the data we have posted in this thread I can make this assessment assuming the data is valid regarding best instantaneous acceleration:

K-4 7400 lbs best climb 4823 fpm
P-51B 9600 lbs with 150 octane 67" Hg best climb 4380 fpm (posted by Neil)

K-4 max sea level speed 377 mph
P-51B 150 octane 67" Hg max sea level speed 379 mph (posted by Neil)

The K-4 probably has the better instantaneous acceleration given the plane configs.  I think this is pretty clear.  The K-4 probably has a better average acceleration vs. the Mustang at 150 octane until toward the upper regions of the speed envelope.  This is reading the tea leaves and I can't say with accuracy this is the case.  Keep in mind that as already been batted around here regarding weights.  As the P-51 burns fuel it would start making up the difference between the K-4's acceleration edge.  How much this would be and if this would ever equalize or "cross-over" I don't know.

BTW - I misquoted myself LOL regarding the figure I used for the P-51's FPA figure. I had calculated and posted 4.10 sq ft but in quoting myself in my last post I mis-typed it as 4.61 sq ft which I have now corrected.

The CD0 .0176,  FPA 4.10 sq ft figure most likely is not factoring in ramjet thrust for the P-51.  NACA wind tunnel tests resulted in CD0 for the P-51 at .0173.  The ramjet impact would show up in an actual flight test not while the plane sat statically.

Tango, XO
412th FS Braunco Mustangs

[mold]

Originally posted by dtango
The CD0 .0176,  FPA 4.10 sq ft figure most likely is not factoring in ramjet thrust for the P-51.  NACA wind tunnel tests resulted in CD0 for the P-51 at .0173.  The ramjet impact would show up in an actual flight test not while the plane sat statically.

Oh, I see...perhaps I was mistaken earlier.    By "ramjet", are you referring to the fact that the engine isn't on in a wind-tunnel test?