Best Messerschmitt Bf109 subtype

[Soren]

Claidemore are you seriously trying to suggest that the Clmax of the 109's wing without slats was below the Spitfire's ?? This is as far out as your claim that the Clmax for the Spitfire's wing is 1.50!

Don't you understand that the Spitfire's wing Clmax was as low as proven because it was thin and used a rather low Clmax airfoil ??? (NACA 2200 series)The Bf-109's wing is thicker and uses a higher lift airfoil (NACA 2R1)!

Moving on..

The Emil the RAE tested was first of all not using proper fuel, so power wasn't high enough, and secondly the stalling figures are completely off so something wasn't done right, go read the 109E's POH and you'll see that right away.

Furthermore the V24, a 109F with a reduced wing span and wing area of 15.1m^2 because of removed wing tips achieved a Clmax of 1.48 (Freestream) in windtunnel tests, and this was WITHOUT slats and with a lower AR wing. So the Clmax WITHOUT slats for a full span wing was somewhere in the area of 1.55.

Here's the effect slats & flaps have on the Clmax of a std. 12% Clark Y airfoil (Note: The NACA 2R1 is a modified Clark Y airfoil with a higher Clmax and lower drag)



So are you still under the illusion that the slats only helped a few percent ?

As for landing speeds, here are the landing speeds for the Bf-109F-4 and K-4:

Bf-109F-4 V-lande: 135 km/h
Bf-109K-4 V-lande: 150 km/h

These are the official landing speeds, in TAS! Not IAS!

And the Clmax and Cd0 of the 109F gear and flaps up:


By Comparison the Ta-152H-1 has a landing speed of 155 km/h and the Fw-190 D-9 one of 167 km/h and the P-51D one of 170 km/h.

Do you need further proof ??

Oh and guess what the Bf-109 also has a much shorter take off roll than the Spitfire. Do you see the pattern emerging ??

[claidemore]

I am seriously suggesting that clMax in a power off glide (slats OUT)for a 109E is 1.4 and clMax for a Spitfire Mk 1 is 1.36. This is straight from the RAE test chart. I don't see how we can get a more accurate comparison than two tests done by the same organization at the same time. Other data may indicate different results, but for purposes of comparison, the RAE test is ideal.

As usual, those who find that those numbers do not support what they want to believe, will claim that the British didn't know what they were doing, so the test must be wrong or biased or something. Sometimes the grapes are sour.

I fail to see how the type of fuel can affect a 'power off' glide?

Actually the 109 wing resembles the NACA 2315 and 2310. The slats helped the 173 sq ft 109 wing, by a factor of about 12-13% as you alluded earlier, HOWEVER they only increase it's cl compared to the 242 sq ft Spit wing, by 3%. That is not hard to understand.

20 degree flap setting and 150 more horsepower, 500 lbs less weight, the 109 should have a shorter take off roll, particularly if the Spit does not have a constant speed prop. With constant speed prop the Spit roll off was only 150 yards (for the heavier Mk II!).

We still have trials done by Rechlin and RAE and AFDU that show the Spitfire outturning the 109. Can all those trials be wrong?

[kool kitty89]

Soren, something I noticed from the Drag Estimation chart, the automatic "slot" increases the CLmax by ~42.6% not 25%, so using that figure for the 109's ~48% span LE slats the CLmax should increase by ~20.4%.

And if you work backwards (using all figures according to claidmore's post) with 1.4 CLmax with slats adding 13%, w/out slats the wing's CL would be ~1.24 (which is worse than the standard Clark Y airfoil), which is decidedly low. And if we use other figures it's even lower.

Even if we assume the wing is a standard (less efficient) Clark Y airfoil from that chart with 48% span slats, the CLmax with slats should be in the area of 1.67. (using data from the Drag Estimation chart) possibly a little less since the inner wing may be past critical AoA. (not sure on that)

[claidemore]

The stalling speeds of the 109E are as stated 74 mph flaps and gear up, and 61 mph gear & flaps down, and this is from the Dash 1 (POH).

This is in very close agreement with the RAE tests of the 109E, which got a stall speed reading of 75 mph for flaps and gear up (ASI air speed indicated, which we usually refer to as IAS nowadays) on the regular airspeed indicator in the cockpit, and 61mph for flaps and gear down. Of course the real speed, (TAS) as measured by the 60 ft trailing static head, was 95.5 mph for flaps and gear up, with slats deployed.

That gives us a clmax of 1.4 but more importantly, it gives us an accurate stall speed, which is 11.5 mph higher then the stall speed of the Spitfire measured using the exact same method. And there lies the turn advantage for the Spitfire, the 109 stalls first, and the Spit is still turning.

The guys who flew these planes have been telling us this for nearly 70 years, but we're just too smart and arrogant to believe them.

[Soren]

The guys who flew these planes have been telling us this for nearly 70 years, but we're just too smart and arrogant to believe them.

I beg your pardon ?? Are you forgetting that just as many has said otherwise and most notably so the experts flying the a/c such a LW chief test pilot Heinrich Beauvais ??

I think it is arrogance to refuse to want to learn the truth and desperately cling to old claims & myths, refusing to use ones logic,

Claidemore,

You're Cl estimations are to put it simply very inaccurate, heck take a peak at the normal Clmax of a std. 12% Clark Y airfoil and then remember that the Bf-109's wing used an improved higher lift Clark Y airfoil designated NACA 2R1 which Clmax range is close to that of the 23000 series. And with a TR which ranged 14.2% at the roots to 11.35% at the tips, the 109's wing is alos thicker. By now use of pure logic will tell you that the Clmax can only then be significantly higher, esp. when adding the approx. increase in Cl offered by the slats, which is atleast in the 25% range in the covered areas.

As for the RAE tests, no they can't have been very accurate for the very reason that everyone, including the French, Finnish & Germans got completely different results from actual windtunnel tests which mind you are allot more accurate than those RAE field tests. Remember that in a windtunnel you are in complete control of the inviroment, while out in nature a large magnitude of things could effect the way the tests come out.

KK,

The Handley page auto slots represented on that chart are of a different design than the ones on the 109, as they drop down to increase camber. The fixed slot is of the same design as the 109's auto slats when they're fully deployed and this is therefore the one to be looking at. The increase is in this case from 1.29 to 1.77, a 37% increase in Clmax, but this is only in the covered area, so we can cut that down to 17% and then down to around 13% when we factor in that the 109's wing was thicker to begin with.

[claidemore]

Soren;
Rechlin test: Spitfire outturns 109 in every situation.
RAE tests, Spitfire has smaller turn radius, Spitfire stalls at a higher G load, Spitfire stalls at a lower air speed, measured TAS stall speeds of 95.5/109 and 84/Spit I.
AFDU tactical trials: Spitfire out turns 109, 190, and every thing else.

Would this be the source of the myth?

Logic somehow ignores all these tests and all the data contained in them, and assumes that the 109 wing which has "improved higher lift" has cl that is "significantly higher" and has an "approx. increase in Cl" with cl range " close to that of the 23000 series" and 2%? higher TR has somehow overcome a 30% deficiency in wing area, and a 21% deficiency in wingloading.
So we take some assumptions, a handful of generalizations, and use logic to come up with what?

The Hawker Typhoon had a nice thick wing,(NACA 23 series) and it didn't turn as well as the Spitfire either. Interesting that it has a similar trapezoidal profile to the 109 and 190 which caused it to get shot down by over-enthusiastic Mustang pilots. Could that trapezoidal shape be the source of its poor turn performance?

Quote from Mike Williams site:

The Tempest arose from Hawker’s desire to apply a new, thin wing to the Typhoon in order to enhance performance. The Tempest V combined the new semi-elliptical wing with the Typhoon airframe and Sabre II engine. The new wing was five inches thinner at the root with the maximum depth of the new section occurring farther back, at 37.5% of the chord, while the thickness/chord ratio was reduced, 14.5% at the root tapering to 10% at the tip.

Hmmm, those numbers are pretty close to the 109 numbers, how did the Tempest fair in a turn fight against a Spitfire? Not well. Mustang outturned it too, and it was just slightly better than the 109G2. Since I think the G2 used in those trials was not up to snuff, I'll allow that it might have matched or even outturned the Tempest slightly if it was in 100% condition. (i know that will come back to haunt me!)
In any case, we know that the Spitfire easily outturned the Tempest, and the Tempest turned about the same as a 109, so logic tells us?


As for my cl calculations, they are completely accurate.
Stall speed of 95mph TAS, weight of 5600 lbs, wing area of 173 sq ft and you get cl of 1.4020.

[Soren]

Claidemore,

We've already discussed why the tests with the Emil aren't worth anything many times before so I wont even go there.

As for the stalling speeds of the Bf-109E that I listed, these are TRUE airspeeds, NOT indicated stall speeds. The indicated stalling speed was 10 km/h lower in all cases.

As for the Clmax of the wing, it is 1.70 as established in multiple windtunnel tests clean with gear & flaps up. With no slats the Clmax would've been around 1.50+.

The Spitfire's wing's Clmax was 1.36.

And here the Clmax of the NACA 23000 series airfoil from 9 to 18% in thickness ratio. As you can see there's a limit to how thick the wing can be before Clmax start to drop instead of increasing:


The average Clmax for a airfoil from 15 to 09% is 1.58 to 1.59, much higher than normal, which can also been seen when compared to the Clmax ofthe std. Clark Y airfoil.

Btw, the Clark Y airfoil was used by all Yak, La & LaGG fighters, while the 109 featured a modified type with a higher Clmax and lower drag.

And as for the Typhoon, like I said it outturned the Tempest despite being heavier, having less wing area and having less power available, and this was thanks to its higher TR & AR wing.

PS: The Tempest also used a airfoil which was bad for turn performance but good for speed.

[kool kitty89]

He's saying that the combination of the higher lift airfoil, the higher TR, and LE slats, overcome the high wing loading.

The Typhoon should have had a fairly high CL, but it had high wing loading and no additional high lift devices.

The Tempest's wing should have had a much lower CL, due to being much thinner and using a low drag airfoil with the max thickness at 37.5% chord. (similar to the P-51's psudo-laminar-flow wing;low-lift and low drag= good speed but not for turn)


Technically the 109F and later models had a tapered wing with rounded tips, and thus would no longer be considered trapizoidal. And anyway there were other a/c with similar plan for that had decent maneuverability as well.

[Soren]

Very correct KK.

[claidemore]

RAE had people who devoted their entire lives to aircraft research, they had experienced test pilots, aeronautical engineers and designers, skilled technicians, research scientists, the best aviation people in Britain, with an enviable reputation. (they had Beatrice Shillling too!) They had access to some of the best equipment in the world, and cooperated extensively with American test facilities and personnel. Hitler wanted their research so much that he would not allow the Luftwaffe to bomb it, assuming that eventually he could capture it.

You seriously think we should completely dismiss their findings and results? All these highly qualified experts were wrong, and you are right?

Persoanlly, I think they knew a hell of a lot more about this stuff than your or I, and this chart illustrates it pretty well.

[Glider]

Originally Posted by Soren

The Emil the RAE tested was first of all not using proper fuel, so power wasn't high enough,

I admit I thought that I had heard all your arguments but this is a new one on me.
Can I ask what fuel was used in the test and what fuel should they have used plus how do you know?

I say this as the standard front line fuel in the RAF was 100 octane, which was higher than the normal fuel available to the Luftwaffe. So at worst it was likely that they gave it a higher than normal octane fuel, at best the correct level.

[parsifal]

This was a quote relating to the Emil, concerning manouverability

We in J52 were very inexperienced, in just two months, our strength fell from thirty-six pilots to four. We really wasted our fighters. We didn't have enough to begin with, and we used them in the wrong way, for direct close escort. We were tied to the bombers, flying slowly - sometimes with flaps down - over England. We couldn't use our altitude advantage nor our superiority in a dive. Of course, the Spitfire had a marvelous rate of turn, and when we were tied to the bombers and had to dogfight them, that turn was very important".
Gunther Ball of 8/JG52

It was also thought that unbeknown to the pilots the British Air Ministry instructed that Hurricanes and Spitfires use 100% high octane fuel instead of the 87% octane that both the RAF and the Luftwaffe were using at the outbreak of the war. Richard Hough and Denis Richard's mention in their book that in September 1939 the U.S Congress invoked the Neutrality Act that prohibited the use of 100% octane fuel, but after some anxious moments, the British Government and the Roosevelt Administration had reached a compromise where the supply of this fuel could be used on a 'dollar on the barrel-head' basis [1].

This is an Link to an article I found by John Dell on this very issue. Dell argues that it is actually unclear as to which aircraft was the more manouverable, but in the end, in his opinion, ther was a slight advantage to the Spitfire. Dell attributes these advantages to the small cockpit size, and heavier controls for the 109 at high speed, coupled with an apparently peculiar and less efficient stick design. He seems to think that these peripheral handicaps added up to the german pilots having a lesser physical ability to match the spit in a high g turn.

Anyway, have a look an see what you think

The Supermarine Spifire in combat - an essay.

[kool kitty89]

Kfurst should have more info on the fuel. nd iirc the normal liste "octane" number for the LW fuel didn't always corespond to to the same number as in standard fuel. (particularly the blended fuel iirc)



Claidmore, the turn testing is interesting, but where are the Cl figures you were talkin about. (which operating condition should have litte effect on, as testing would be done in a power off glide)

[Glider]

Originally Posted by kool kitty89

Kfurst should have more info on the fuel. nd iirc the normal liste "octane" number for the LW fuel didn't always corespond to to the same number as in standard fuel. (particularly the blended fuel iirc)

I await it with interest. Its a major claim and its one that I have never heard before. I have read the reports as I am sure you have and can find no mention of fuel issues impacting the performance of the 109.

[parsifal]

A very quick comment about different fuels (I have to go to a lunch). Higher octane rating fuels essentially have a slower burn rate than the lower rated fuels. This is achieved by putting burn inhibitors into the fuel. Typically lead (although banned in many countries now). The longer fuel burn time means that the fuel air mixture is burning down a greater portion of the cylinder, whilst on the power stroke. A much greater proportion of the fuel can be burnt in this way, and a sustained power stroke is more efficient than if the fuel "explodes", rather than "burns".

However, if you put higher octane fuel into an engine tuned for a lower rating fuel, you will downgrade the power output of that engine markedly. This is because the fuel air mixture will continue its burn cycle into the exhaust stroke.

Every old car engine I have ever worked on can be retuned to accommodate 100 octane fuel. This was certainly also true for the Hurricane and Spit 9note i have never worked on any aero engines). They ran on both types of fuel. Dont know about the DB 601. One of you more technically minded guys will have to answer that. But one would assume that it could be re-tuned.

Even if it was not re-tuned, the guys undertaking the tests would immediately have known that. The engine would simply not run correctly if it was fuelled up incorrectly. Running an engine in that state would be very obvious due to all the backfiring and noise that would be going on. moreover, it would be quite unsafe to fly. To even a first year engine mechanic, it would have been obvious what the problem was, and since the RAF was still using the lower rated fuel at the same time as the 100 octane fuel, the solution easily at hand.

So Sorens claim about using the wrong fuel is possible, in a theoretical sense, but the practicalities make it a highly unlikley scenario