Best Messerschmitt Bf109 subtype

[Soren]

Guys the Germans used low octane synthetic fuel, the Allies used high octane natural fuel, and that is why the engine didn't perform well. It's the same with Fabers A-3 which got captured, the engine ran extremely poorly and the problem was only corrected well after all the tests by the RAE & AFDU.

[Kurfürst]

Originally Posted by claidemore

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.

... this chart illustrates calculated turn radiuses based on estimated Cl etc. values obtained with unreliable methods on a captured plane the French tested after it made an emergency landing...

It shows that and nothing more. And while the RAE paper you quote draws the - to me at least, reasonable, given the basic technical characteristics, ie. wingloading, power loading, drag etc. - conclusion that the Spitfire can, technically, turn better, it also mentions that 'in a surprisingly large number of cases', the 109E had no trouble turning with the Spitfire; this was entirely down to the Emils better control&stall characteristics is pitch and near the stall. Simply to put, less experienced pilots found it more difficult to push the Spitfire to the edge than the 109. The Spitfire was oversensitive in pitch (something that Rechlin, RAE, and NACA agrees on), it took very delicate movements on the coloum to ride the stall - which was very violent on the Spit - when at the same time the control harmony was poor, and the handling ailerons were like arm-wresting match.

Not much of a conclusion can be drawn based on these 109E vs Spit I results though, their design did not remain constant through the war. Basically the Spitfire gained more weight in both absolute and relative (%) terms than the 109 during its development life; also the 109 was gradually cleaned up aerodynamically, whereas the Spitfire only detoriated from the drag`s point of view after the Spitfire Mk I.

In brief, whatever the relative merits of the 109E and Spitfire I were in the turning department, with the later variants the balance is increasingly in favour of the lighter, cleaner 109 version.

My 2 fillérs, but I dont want to get any deeper than that, you guys are having the same conversation for the 100th time here...

[Soren]

you guys are having the same conversation for the 100th time here...

Exactly, and its getting real tiring..

As stated by German, British and modern pilots, the two a/c were very close in all aspects of flight, esp. turn performance, and it was a matter of pilot experience in the end.

We have Mark Hanna, Skip Holm, Dave Chairwood, Walter Wolfrum, Erwin Leykauf, Heinrich Beauvais etc etc and aerodynamics confirming this.

Both a/c were excellent fighters IMO.

[Kurfürst]

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)

A quickie.

The LW used two kinds of fuel. B-4, nominally 87 octane, and C-3, nominally 96 octane.

By Allied standards, C-3 was actually 130 grade fuel; in late 1942, its mixture was changed and it was an equivalent of 150 grade fuel. I am not sure about B-4.

Some reports though indicate that the fuel found in cases the downed fighters tanks was some kind of mixture of B-4 and C-3, something like 92 octane IIRC.

In any case, its worth to consider the fuel requirements from the technical sides; the main Allied inline engines, the Merlin and Allison, were relatively low displacements at 27 liters compared to the DB etc. engines. So the only way they could match the larger engine`s output was using highly manifold pressures, and/or higher RPMs. Higher manifold pressures absolutely required higher grade fuels to prevent knocking; also, to make best use of these fuels for power, comparatively low CRs were used; combined with the high supercharging needs required for high manifold pressure, this lead to high fuel consumption, and much more need for high octane fuels; the Germans, French (and thus Russians, who copied French inlines) with their high capacity engines simply didn`t require such fuels for high output.

[parsifal]

But soren, using incorrect fuel in an engine (whether it be synthetic, or natural) is an obvious and easily corrected problem. A simple engine timing test would reveal the problem. I dont know anything about these "RAE" tests, not even when they were carried out, but putting the wrong fuel into an engine can only be something you would do deliberately. To a trained mechanic, the engine knock is something detected immediately, and an ignition timing test would pinpoint the problem with complete accuracy. Even small differences in the type of fuel could be detected very easily.


It just seems very implausible that tests such as these "RAE" tests would be compromised by such a silly error. What is entirely plausible is that the wrong fuel is put into the tank initially ( and recorded, I guess), and then the problem being corrected, either by putting the correctly rated fuel in, and/or adjusting the ignition timing.

Kurfurst also mentioned that the 109 could use either 87 rated fuel, or 150 octane rating fuel, or some mixture in between. in each case, the engine would need to be re-tuned to take the new fuel.

[parsifal]

I found this posted in Wikidapedia.

Seems that the 87 octane rating given to German "standard fuels" was the same as the 100 octane rated fuels in allied circles.

The quote from wikidapedia should be taken with the usual caveats as to accuracy

During World War II, Germany received much of its oil from Romania. From 2.8 million barrels (450,000 m³) in 1938, Romania’s exports to Germany increased to 13 million barrels (2,100,000 m³) by 1941, a level that was essentially maintained through 1942 and 1943, before dropping by half, due to Allied bombing and mining of the Danube. Although these exports were almost half of Romania’s total production, they were considerably less than what the Germans expected. Even with the addition of the Romanian deliveries, overland oil imports after 1939 could not make up for the loss of overseas shipments. In order to become less dependent on outside sources, the Germans undertook a sizable expansion program of their own meager domestic oil pumping. After 1938, the Austrian oil fields were made available, and the expansion of Nazi crude oil output was chiefly concentrated there. Primarily as a result of this expansion, the Reich's domestic output of crude oil increased from approximately 3.8 million barrels (600,000 m³) in 1938 to almost 12 million barrels (1,900,000 m³) in 1944. Even this was not enough.

Instead, Germany had developed a synthetic fuel capacity that was intended to replace imported or captured oil. Fuels were generated from coal, using either the Bergius process or the Fischer-Tropsch process. Between 1938 and 1943, synthetic fuel output underwent a respectable growth from 10 million barrels (1,600,000 m³) to 36 million. The percentage of synthetic fuels compared with the yield from all sources grew from 22 percent to more than 50 percent by 1943. The total oil supplies available from all sources for the same period rose from 45 million barrels (7,200,000 m³) in 1938 to 71 million barrels (11,300,000 m³) in 1943.

By the early 1930s, automobile gasoline had an octane reading of 40 and aviation gasoline of 75-80. Aviation gasoline with such high octane numbers could only be refined through a process of distillation of high-grade petroleum. Germany’s domestic oil was not of this quality. Only the additive tetra-ethyl lead could raise the octane to a maximum of 87. The license for the production of this additive was acquired in 1935 from the American holder of the patents, but without high-grade Romanian oil even this additive was not very effective. 100 octane fuel, designated either 'C-2' (natural) or 'C-3' (synthethic) was introduced in late 1939 with the Daimler-Benz DB 601N engine, used in certain of the Luftwaffe`s Bf 109E and Bf 109F single-engined fighters, Bf 110C twin-engined fighters, and several bomber types. Some later combat types, most notably the BMW 801D-powered Fw 190A, F and G series, and later war Bf 109G and K models, used C-3 as well. The nominally 87 octane aviation fuel, designated 'B-4' was produced in parallel during the war.

In the US the oil was not "as good," and the oil industry had to invest heavily in various expensive boosting systems. This turned out to have benefits: the US industry started delivering fuels of increasing octane ratings by adding more of the boosting agents, and the infrastructure was in place for a post-war octane-agents additive industry. Good crude oil was no longer a factor during wartime, and by war's end, American aviation fuel was commonly 130 octane, and 150 octane was available in limited quantities for fighters from the summer of 1944. This high octane could easily be used in existing engines to deliver much more power by increasing the pressure delivered by the superchargers.

In late 1942, the Germans increased to octane rating of their high-grade 'C-3' aviation fuel to 150 octane. The relative volumes of production of the two grades B-4 and C-3 cannot be accurately given, but in the last war years perhaps two-thirds of the total was C-3. Every effort was being made toward the end of the war to increase isoparaffin production; more isoparaffin meant more C-3 available for fighter plane use.

A common misapprehension exists concerning wartime fuel octane numbers. There are two octane numbers for each fuel, one for lean mix and one for rich mix, rich being greater. The misunderstanding that German fuels had a lower octane number (and thus a poorer quality) arose because the Germans quoted the lean mix octane number for their fuels while the Allies quoted the rich mix number. Standard German high-grade 'C-3' aviation fuel used in the later part of the war had lean/rich octane numbers of 100/130. The Germans would list this as a 100 octane fuel while the Allies would list it as 130 octane.

After the war the US Navy sent a Technical Mission to Germany to interview German petrochemists and examine German fuel quality. Their report entitled “Technical Report 145-45 Manufacture of Aviation Gasoline in Germany” chemically analyzed the different fuels, and concluded that “Toward the end of the war the quality of fuel being used by the German fighter planes was quite similar to that being used by the Allies.”

[Glider]

Originally Posted by Kurfürst

... this chart illustrates calculated turn radiuses based on estimated Cl etc. values obtained with unreliable methods on a captured plane the French tested after it made an emergency landing...

It shows that and nothing more. And while the RAE paper you quote draws the - to me at least, reasonable, given the basic technical characteristics, ie. wingloading, power loading, drag etc. - conclusion that the Spitfire can, technically, turn better, it also mentions that 'in a surprisingly large number of cases', the 109E had no trouble turning with the Spitfire; this was entirely down to the Emils better control&stall characteristics is pitch and near the stall. Simply to put, less experienced pilots found it more difficult to push the Spitfire to the edge than the 109. The Spitfire was oversensitive in pitch (something that Rechlin, RAE, and NACA agrees on), it took very delicate movements on the coloum to ride the stall - which was very violent on the Spit - when at the same time the control harmony was poor, and the handling ailerons were like arm-wresting match.

Not much of a conclusion can be drawn based on these 109E vs Spit I results though, their design did not remain constant through the war. Basically the Spitfire gained more weight in both absolute and relative (%) terms than the 109 during its development life; also the 109 was gradually cleaned up aerodynamically, whereas the Spitfire only detoriated from the drag`s point of view after the Spitfire Mk I.

In brief, whatever the relative merits of the 109E and Spitfire I were in the turning department, with the later variants the balance is increasingly in favour of the lighter, cleaner 109 version.

My 2 fillérs, but I dont want to get any deeper than that, you guys are having the same conversation for the 100th time here...

Section 5.4 of the paper summerises the 109's Good and Bad points

Good
a) High top speed and excellent climb
b) Good control at low speeds
c) Gentle Stall even under G
d) Engine doesn't cut out under negative G

Bad
a) Controls, Particularly the ailerons, far to heavy at high speeds
b) Owing to the high wing loading, the aeroplane stalls readily under G and has a poor turning circle
c) Aileron snatching occurs as the slots open
d) Quick manoeuvers are difficult, at high speed because of (a) above, at low speed because of (b) and (c) above.
e) Absence of the rudder trimmer, curtailing the ability to bank to the left at high speed.
f) Cockpit to cramped for comfort in combat.

Re the ability of the 109 to turn with the Spit it strikes me as being the age old point that an experienced pilot will get that bit more out of an aircraft than a 'normal' pilot. If the Spit went to the edge it would turn better, if it didn't and the 109 went to the edge then the 109 could hang on.
If both pilots were the of similar skill then the Spit would have the edge in the turn.

What I suggest and am sure that Kurfurst would agree with, is to encourage everyone to read the entire report and draw your own conclusions.

For those who don't know the link its as follows: -
http://www.ww2aircraft.net/forum/fli...eads-8132.html (Bf-109 Performance Threads)

[kool kitty89]

The 109F and later models cured or improved most of those faults.

[Glider]

Of course the 109 improved as did the Spitfire, but that wasn't the point.

The point was that emphasising small parts of what is a very detailed paper can be very misleading. That applies to any paper of any topic.

All I am trying to do is to print out all the summary (time permitting) which covers both the positive and negative sides of the report and encourage anyone interested to read the entire thing and draw their own conclusions. Nothing more and nothing less.

[kool kitty89]

Yes, but the Spitfire had fewer faults to cure and did so more slowly. (this is with changes in engines/weapons aside).

The Major problem with the Spit's airframe was with aileron control at high speeds, then wing tip warping causing control reversal. Other than that there weren't many things they corrected. Low drag radiator was added, that's about it. The aerodynamics stayed about the same. (sometimes got worse for certain applications or to trade off one performance category for another: ie CW spitfires, or long range versions) Also the Spit had a considerable weight increase throughout development while the 109 generally did not. (sometimes getting lighter)

And the 109 consistently got cleaner.

[Soren]

Also noteworthy ofcourse is the change in slats design from the Emil series to the F series and beyond. The Emil's slats were very unreliable, jamming all the time or deploying incorrectly according to each other, causing premature stalls in turns and vicious spins.

[kool kitty89]

And there was the jolt from the rapid deployment of the Emil's slats while the later design introduced in the 109F line opened smoothly, same as the Me 262's.

[Soren]

Yes.

[pbfoot]

i believe the slats issue is a maintainence problem , it has nothing to do with the slats themselves its the maintainers

[Soren]

Wrong, design flaw, way to sensitive to dirt and very unreliable in action under G's. This problem was first fixed with the F series.