FW-190 - How Good Was It, Really?

[swampyankee]

Hi Tomo,



I... ended with fuels called 115 / 145, sometimes mistakenly called grade 150 fuel. Nobody makes 115 / 145 fuel anymore except by special order.

When one of the test engineers I worked with at Lycoming was involved in the flight tests of the ALF-502 engine on the ex-USN AJ-2, he told a story about the flight test manager with bottles of tetraethyl lead spiking barrels of 100/130. I never got to rode in the AJ-2. The plane never crashed, but after that last stint of flight testing it went to a museum. I was told that the flight test people at Lycoming felt the aircraft had very little life left in it, and was approaching a condition where it wasn't flight worthy without far too much expenditure.

 

[wuzak]

I see your statement that the myth of British fuels being significantly different from U.S. fuels is dead and buried. I have not read anything that supports that other than posts in here, and have first-hand testimony from several P-38 pilots that the early P-38s DID have fuel-related problems that were cured. They were told it was the gasoline after the cure was effected. It took some 8 - 10 months because nobody sent any British fuels back to the U.S.A. for analysis. When they did, the difference in aromatics became known and the carburetor jets were changed, eliminating that issue. After that, it wasn't an issue as long as the fuel to be used was specified.

P-40s didn't seem to have much of a problem on "British fuels".

 

[swampyankee]

P-40s didn't seem to have much of a problem on "British fuels".

I suspect that the turbocharger gave a higher pressure ratio, resulting in a higher cylinder inlet temperature than did the supercharger on the P-40. We could also have a thread about how the P-40 has been undeservedly maligned.

 

[Shortround6]

In WWII, aromatics were mostly Benzene and Benzene derivatives, used mainly to increase the Octane number. After an Octane rating of 100 (101 - 150), the term is "performance number." In WWII, we had gasoline with two ratings, the lean rating (cruise condition, leaned out), and the rich rating (full power, full rich). We started the war running 80 / 100 fuels (generally) and ended with fuels called 115 / 145, sometimes mistakenly called grade 150 fuel. Nobody makes 115 / 145 fuel anymore except by special order.

The US started the war using fuel with octane ratings from around 65 to 100, in 1939-40 there was no "rich rating".

Grades may have included 65, 73, 80, 87, 90/91 and 100. The lower grades were used in light aircraft and trainers.
see: http://rgl.faa.gov/Regulatory_and_G...86f3a8c564f1a8525670c00523a93/$FILE/E-216.pdf
For the inline 6 cylinder Ranger which was available to use 4 different grades of fuel. Each engine used a different compression ratio (but no supercharger).
Large commercial and military aircraft used 87 pretty much as a minimum although a few planes using P & W Wasp Juniors had a small tank of 87 octane and several larger tanks filled with 80 octane. The 87 octane was used for take-off and then the plane cruised on the cheaper 80 octane. This was one of them.

There may have been some very short lived grades of fuel between 91 and 100 at this time. 91/96 did show up as a standard later.
Post war things get real confusing as were four grades of Military fuel (80, 91/96, 100/130, 115/145) and five grades of commercial fuel (80/87, 91/98, 100/130, 108/134 and 115/145) in 1951. Please note there were a few differences between military fuel and commercial. Commercial fuel had slightly lower evaporation temperatures, more allowable gum residue and precipitate, but lower allowable lead content in the mid grades.
Please note that during WW II there sometimes more than one specification per year for a given grade of fuel. 100/130 went through 3 if not 4 specifications (maybe more) and that does NOT include either the pre war American 100 octane, the British pre war/early war 100 octane, or the 100/125PN fuel.
First 100/130 only allowed 3.0 CC of lead per US gallon, the 2nd allowed 4.0 CC of lead and the 3rd allowed 4.6 CC of lead. Please note that just because 4.6 CC could be used doesn't mean it was used in all batches.
Benzine was not well liked by early WW II despite being a "go to" additive in the 1920s and early 30s. It had a few problems for aircraft use if you weren't record breaking at sea level. One was that if froze at 42 degrees F. That is 42 degrees above zero, not below. Another was that it good for about 17,300btus per pound of heat value compared to the desired 18,700 Btus per gallon of av gas. While it's anti knock rating running richis very, very good it's anti-knock ability when running lean is not so great. Adding lead to Benzine does just about nothing.

C-3 was also found to 40% aromatics (!), which is about twice that of British fuels. US fuels were less than 5% aromatics, and British fuel gave early P-38s fits when they got to the UK because the engines were set up for U.S. fuels. I have little doubt that the BMW 801 in the test was not very comfortable on U.S. fuel.

Early British fuel was sometimes 40% aromatics. Early American fuel was under 2%, this was lifted to 5% for a short period to help increase production but little of this may have been actually made. The short lived 100/125 fuel was allowed to use 20% aromatics although not spelled out in specifications. The upper limit was more a by product of heat energy content specification.

Please see, "Development of Aviation Fuels" by S. D. Heron.

 

[DarrenW]

To answer your question, we used different additives to get high-performance number fuels and used less aromatics than did Europe. Neither is good or bad, just a fact. But the two different routes to higher Octanes burn differently when the mixture changes, and it isn't important which fuel you use as long as you know and jet for it.....

I appreciate the further explanation. So when you use the term "jet" I suppose you are talking about the jets of a carburetor or fuel injection system?

 

[Milosh]

Please note that the report Tomo linked to is dated 1940-1943. A PN increase over 125 after 1943 would not be in this report.

 

[GregP]

Hi DarrenW,

Yes, carb jets.

Rest, I didn't cover all the German, Japanese, Russian, British, and U.S. fuels. I was trying to say that I have first-hand statements about the issue with early P-38s that point squarely at fuel issues. I suspect, as mentioned, that the fact that the P-38 was both supercharged and turbocharged has something to do with it since the mixture was much hotter as-delivered to the cylinders than anything in a non-turbocharged P-40 ever was. An extra boost stage does that.

The Allison letters of the day indicate fuel issues, as does Allison company correspondence and former Allison employees in possession of a friend who builds Allisons. To me, the issue is mixed in with the intake manifold mixture issue that was solved about the same time as the fuel issue, and the final solution could easily have been the result of both changes.

For those who don't know, the original Allison intake manifolds served 3 cylinders (4 of them mated to two ram's horn distribution castings), was very smooth and the mixture came into the manifold in the middle. The resultant mixture bounced off the smooth interior and made the outer two cylinders rich and the inner one lean from an initial homogeneous mixture. The solution was to install a turbulator inside the manifold to make the mixture swirl inside the manifold, evening out the flow. The combination of the turbulator and the jets made a huge difference in the way fuel was burned.

I wasn't there in WWII, but I can see how it works on an Allison today on a regular basis, including on P-38s running engines we built. Coupled with first-hand accounts, it seems to me there WAS an issue with British fuels. Nothing whatsoever wrong with the WWII British fuel ... it just wasn't exactly the same as U.S. fuel of the day. Once known, the jets were easily worked out.

I have no problem if people refuse to believe it. If you worked on and with Allisons, you'd probably know if you had the old correspondence and tried the old manifolds. Otherwise, we read what people who weren't there, never flew planes, and never worked on Allison engines wrote after the war was over. They may be good researchers who write books, but they weren't there just as I wasn't.

 

[DarrenW]

Yes, carb jets.

I have little doubt that the BMW 801 in the test was not very comfortable on U.S. fuel.

So from what you are telling me, the octane rating is just one of several specifications to consider when deciding what fuels to use, in this case with a WWII radial engine. Wouldn't the persons performing the test normally know if the fuels they were using were 'compatible' with the engine in question? And would adjustments be made to the carb at that point? Excuse me for not being very educated on the subject, I'm most likely asking questions that others in this discussion already are well aware of....

 

[Shortround6]

The fuel issue is very complicated. There are literally hundreds of different compounds that can be found in gasoline, at least in trace amounts. Some have more impact than others.
The source of fuel varies considerably, that is to say the crude oil from one field can vary considerably from one oil to another oil field and to a lesser extent from oil wells within a large field. Some oil comes out of the ground with 30-40% aromatics and some comes out with almost none. Some other basic elements can also show the same sort of variation.

Until the late 20s most aviation fuel varied from around 38-40 octane to around 70 octane however until the invention/development of the octane scale there was no way to measure the differences. They were known to exist but there was no way to measure or judge a particular fuel sample. Once you had the octane scale you could measure up to 100 octane but after that things got tricky, all you could say was that fuel XX acted like 100% Iso-octane plus X amount of lead if it went over 100 octane. S. D. Heron (author of the book mentioned above) helped develop/invent the performance number scale (among other things) which not only goes above 100 octane but is much more liner that than the octane scale. The octane scale is actually somewhat curved. the difference between 70 and 80 octane is actually a lot less than the difference (about 21%) between 80 octane and 90 octane (about 26.3% improvement) and another 10 points (90 to 100) is actually a 35.7% improvement.

The book mentioned is not a history of all aviation fuels but more a history of the allies effort and the conflicting needs between increased production and the availability of certain compounds or refining techniques. Some compounds showed great advantages as additives but either cost too much in the way of raw materials or cost tens of thousand of tons of high grade steel for the refining plant needed to make them.
There was also less than the desired communication between engine makers and the fuel producers although this got better over time. Compound this with the Governments wanting large numbers of the most advanced engines and large amounts of the highest grade fuels and things sometimes got pulled one way or an other.

I would guess that all the major countries had bright and skilled chemists/chemical engineers but not all countries had access to the same quality crude oil or additive industries and not all countries had access to even the needed refining plant improvements.
Even the US could not use some of the better compounds for aircraft fuel, like Toluene which was wanted for high explosives production. However some of the Xylenes were used for aviation fuel and they were a by product of Toluene. Or the large scale production of Triptane would have consumed almost the entire US production of chlorine.

 

[Ivan1GFP]

Life gets a little more complicated still. I don't think I have seen this mentioned yet:
If you have ever looked at the markings on the gas pump, you will see something like (R+M) / 2
What this means is that the octane marked at the pump is an average of the Research Octane and Motor Octane.
(This has been a while....)
Research Octane is a chemical analysis of the gasoline.
Motor Octane is how the fuel behaves in a very specific test engine.
The problem though is that not every country uses the same form of test engine and the resulting numbers may be different.

As was explained to me (and Shortround6 already touched upon here), Petroleum from different sources has different chemical properties such as Sulfur content (a contaminant), and of course a different combination of hydrocarbons which makes them best suited for different purposes. Some kinds might be most useful in making gasoline while others might be more useful for lubricating or fuel / heating oils or other petro chemicals.
I worked for one of the major oil companies supporting their commodities trading and monitoring volatility (of the market kind) and there were a lot of lunch discussions about why we were buying and trading different crudes to support the needs of the refineries and also why often what was pumped out of the ground in one place was shipped to a remote refinery instead of the local one. Often there was a new commodity we had interest in and then folks would need to figure out what it was closest to for analysis of market volatility.

Methane, Ethane, Propane, Butane, Pentane, Hexane, Heptane, Octane, Nonane, Decane....

- Ivan.

 

[taly01]

The 'C3 - Zusatzeinspritzung' system used the (excess) fuel as anti-detonant fluid. It was a factory modification, the excess fuel was sprayed in the eye of supercharger to cool the compressed air so increased boost might be used under the rated altitude

Many books say mid series FW190A-4/5 etc had MW50 water injection, this appears to be a misunderstanding by non-technical authors?

Another amusing error I find is that the 801TS motor is said to be turbo-supercharged! Assuming the author thought T=turbo S=supercharger

Slightly more reliable books have said that MW50 problems were solved and it was available on the 801TS/TH in the Fw190A-9/F-9, they quote a decent 2300HP for it.

 

[tomo pauk]

Many books say mid series FW190A-4/5 etc had MW50 water injection, this appears to be a misunderstanding by non-technical authors?
Another amusing error I find is that the 801TS motor is said to be turbo-supercharged! Assuming the author thought T=turbo S=supercharger
Slightly more reliable books have said that MW50 problems were solved and it was available on the 801TS/TH in the Fw190A-9/F-9, they quote a decent 2300HP for it.

The amount of mistakes that got repeated in English-language publications on German ww2 hardware is pretty big. People often either downplay the capability of German gear, or over-blow it. It would've been very good if someone actually posted exerpts from manuals, test reports and factory docs to prove their statement.

 

[DarrenW]

From Focke-Wulf Fw 190 operational history - Wikipedia:

On the whole, Allied pilots who flew the FW-190 found it pleasant to fly, very responsive, and, while the cockpit was small compared to most Allied fighters, it was well laid out. Most pilots found the FW-190's Kommandogerät system (which automatically controlled the RPM, fuel mixture, ignition timing, supercharger switchover, and boost pressure) to be more of a hindrance than a help.....

I also have read that American pilots said this same system made it extremely hard to fly formation as the pilot had less fine power plant control to 'tune" their aircraft to one another. Did these criticisms stem more from a lack of experience with the Kommandogerät system, or did these feelings exist within the German Luftwaffe as well?

 

[Shortround6]

Some american aircraft had a similar (but perhaps not quite as inclusive ) system later in the war. Perhaps a few british ones did near the end of the war?

I would be leary of the control of the ignition system also. Perhaps the 801 did use an adjustment of the ignition timing, I don't know. Many other engines did not. Or used one setting for starting and then a fixed setting for actually running once started, in which case there was no advantage one way or the other in an "automatic" control.

 

[GregP]

Good post above Shortround. Gasoline IS complex and changing a few minor things can have major consequences. It's a wonder we can drive / fly around with so few issues.

 

[Ivan1GFP]

The amount of mistakes that got repeated in English-language publications on German ww2 hardware is pretty big. People often either downplay the capability of German gear, or over-blow it. It would've been very good if someone actually posted exerpts from manuals, test reports and factory docs to prove their statement.

Hello Tomo Pauk,

If you think information on German aircraft is often incorrect, it gets MUCH worse with Japanese aircraft.

Regarding formation flying, I believe FW 190 had a RPM control that could be finely adjusted for formation flying.

- Ivan.

 

[tomo pauk]

...
If you think information on German aircraft is often incorrect, it gets MUCH worse with Japanese aircraft.
...

Care to make a topic about the coverage of Japanese A/C in Western publications?

 

[Ivan1GFP]

Not really.
I am more interested in finding more information rather than commiserating about the lack of it.

 

[tomo pauk]

Not really.
I am more interested in finding more information rather than commiserating about the lack of it.

Roger that.

 

[alejandro_]

One good feature about the Fw 190 was the engine installation. Kurt Tank managed to integrate a big, powerful radial engine into a small airframe. Soviet engineers who examined a Fw 190 in 1943 found the oil tank/ring configuration very interesting. The power egg configuration was also very handy.

Perhaps someone that has examined other radial fighters can add more. What about Fw 190 evaluation in the UK/US? I think sometimes the fact that it was a top fighter with a radial engine is overblown a bit, as there were models in this era (P-47). I am also thinking about the Il-16, which was a huge surprise during the Spanish Civil War.