FW-190 - How Good Was It, Really?

[swampyankee]

Interesting. In contrast I have heard that the P-47 had a rather cramped cockpit. Any truth to this?

I don't know the answer to that question. A little googling found this article: P-47 THUNDERBOLT, which included an essay by a pilot who flew both P-47s and P-51s in combat (he preferred the former); he said "The Thunderbolt had a much larger, roomier cockpit. You were comfortable in the big Jug cockpit. In my Mustang, my shoulders almost scraped the sides on the right and left. I was cramped in with all my "gear." I could not move around like I could in the P-47. I found the ability to move a little bit very desirable, especially on seven and eight hour missions."

I know some people denigrate the importance of pilot comfort in a combat aircraft, but an uncomfortable pilot will tire more quickly and will be in poorer shape when it times to act.

 

[DarrenW]

...However, the Jabos were 1st to use over-boosting in service, 1st by use excess fuel injection as ant-detonant ('C3 einspritz'), and quickly after that the 'simple' overboosting....

From Focke-Wulf Fw 190 - Wikipedia:

Changes introduced in the Fw 190 A-8 also included the C3-injection Erhöhte Notleistung emergency boost system to the fighter variant of the Fw 190 A (a similar system with less power had been fitted to some earlier Jabo variants of the 190 A), raising power to 1,980 PS (1,953 hp, 1,456 kW) for a short time.


Fw 190 A-4/U8 — The A-4/U8 was the Jabo-Rei (Jagdbomber Reichweite, long-range fighter-bomber), adding twin standard Luftwaffe 300 L (80 US gal) drop tanks, one under each wing, on VTr-Ju 87 racks with duralumin fairings produced by Weserflug, and a centreline bomb rack. The outer wing-mounted 20 mm MG FF/M cannon and the cowling-mounted 7.92 mm (.312 in) MG 17 were removed to save weight. The A-4/U8 was the precursor of the Fw 190 G-1.

Fw 190 A-5/U8 — The A-5/U8 was another Jabo-Rei outfitted with SC-250 centreline-mounted bombs, under-wing 300-litre drop tanks and only two MG 151s; it later became the Fw 190 G-2.

I have a few questions. Was the C3 system added to all of the above mentioned variants at the factory, or was it a field modification performed on selected machines? Also, what exactly is 'simple' overboosting?

 

[pbehn]

Thanks for confirming this first hand drgondog, I had a feeling that what I heard about the P-47 cockpit was untrue.

I have read in various places that the Bf 109 was so cramped that it affected roll rate in some cases, note some graphs for roll rate state a force value. Big pilots simply couldnt exert enough sideways pressure to get the best from the plane, on the other extreme I have read jokes somewhere on this forum about P47 pilots taking evasive action by jumping around the cockpit, there was a lot of "banter" between P47 and Spitfire pilots when it arrived in UK.

 

[Greyman]

I have read in various places that the Bf 109 was so cramped that it affected roll rate in some cases, note some graphs for roll rate state a force value. Big pilots simply couldnt exert enough sideways pressure to get the best from the plane, on the other extreme I have read jokes somewhere on this forum about P47 pilots taking evasive action by jumping around the cockpit, there was a lot of "banter" between P47 and Spitfire pilots when it arrived in UK.

During their Emil testing the RAE noted that due to the cramped conditions, the pilot was only able to exert 40 pounds of sideways force, while in a Spitfire 60 pounds was possible,

 

[tomo pauk]

...
I have a few questions. Was the C3 system added to all of the above mentioned variants at the factory, or was it a field modification performed on selected machines? Also, what exactly is 'simple' overboosting?

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 (1.65 ata vs. 1.42 ata). Please note that BMW 801D was outfitted serialy with direct fuel injection, each cylinder have had it's plumbing and injector. C3 was German name for their 100 oct fuel (it got better than 100 oct during the course of war). Benefit is that it was easier to engineer and install the extra plumbing for that, than to go with water-alcohol injection system. A new boost gauge was also fitted. Shortcoming was that total fuel consumption went sky high, not a good thing when one has fuel shortages. At 1st the system was cleared to use just with supercharger in 1st gear, in 1944 it was allowed also for 2nd gear.
BMW also tried to use MW 50 to increase the boost of their 801s, however the power gain was judged as too small, with reliability problems emerging during the tests, like burned pistons.
'Simple' overboosting took advantage of anti-knock properties of the C3 fuel, just like the RR did it with Merlins 4-5 years earlier. No new parts are needed, apart from boost gauge. The 120-130 PN C3 fuel of 1943 allowed pilots to open up the throttle under the rated altitudes, so boost went up, and power with it. Limit was 1.58 ata in 1st S/C gear, 1.65 ata in 2nd S/C gear. Shortcoming was increased head temperature, so pilots needed to be wary.
1.65 ata = +8.75 psi = 47.7 in Hg
1.42 ata = +5.5 psi = 41 in Hg

 

[DarrenW]

Intersesting stuff. So after the higher octane C3 became available to use with the BMW 801D was the C3 - 'Zusatzeinspritzung' system largely abandoned or was it still in use?

 

[tomo pauk]

Intersesting stuff. So after the higher octane C3 became available to use with the BMW 801D was the C3 - 'Zusatzeinspritzung' system largely abandoned or was it still in use?

My understanding is that, once the 'simple' overboosting was tested and found workable, the installation of the 'C3 - Zusatzeinspritzung' was no longer being installed on production A/C. Talk late 1943/early 1944.
BTW - looks like that 'C3 - Zusatzeinspritzung' was used in service predominantly on fighter-bomber variants.

 

[DarrenW]

I know some people denigrate the importance of pilot comfort in a combat aircraft, but an uncomfortable pilot will tire more quickly and will be in poorer shape when it times to act.

Very true. And this becomes especially relevant after flying several hours seated in one position before even arriving over the target area....

 

[DarrenW]

My understanding is that, once the 'simple' overboosting was tested and found workable, the installation of the 'C3 - Zusatzeinspritzung' was no longer being installed on production A/C. Talk late 1943/early 1944.
BTW - looks like that 'C3 - Zusatzeinspritzung' was used in service predominantly on fighter-bomber variants.

Great. So what you are telling me is that these earlier built BMW 801D engines were engineered from the start to benefit from the higher octane fuels, but because they were either unavailable or in short supply other methods were used to increase the power of these motors. True?

 

[tomo pauk]

The BMW 801D engines were from onset using the C3 fuel. Things were not that clear cut, though, both with engine and fuel. Early BMW 801Ds were unreliable, and during the 1st 7 months or so they were operated with restrictions with regard to the boost and rpm. After modifications were introduced* in late 1942, the engine was finally fully rated (max rpm 2700 max boost 1.42 ata). By that time, the C3 fuel have had it's rich rating around 120 grade (or 120 performance number). During 1943, the C3 fuel got increasingly better, eg. this test mentions it as with rich rating of 140 grade (140 PN), and surely the people at BMW were eager to puch their engine to the reliable limit.
The wartime reports on German fuel development in English language can be accessed at the Fischer-Tropsch archive.
Please note that increase in boost was very modest for such high PN fuel, probably due to the high compression ratio, while the supercharger and associated plumbing needed redesign & improvement. The redesign granted an extra ~0.2 ata of boost under 6 km, or another 200 PS. Again - cue what RR (= Hooker) did with Merlin's 1-stage supercharger & plumbing, but 4 years earlier.
I've tossed in some info about the BMW 801 engines here, FWIW.

* from here: "Chrome-plated valves, Bosch spark plugs, fixed spark plug sockets preferably latest rolled version, nitrated blades in supercharger, strengthened starter shafts. Subject to a reexamination of the empirical data the following procedure is agreed upon."

 

[spicmart]

With the general consensus being that the late-war Focke Wulfs were among the best machines for fighter-versus-fighter combat, I wonder how could an Fw 190D-9, which had its best performance at low-to-medium altitude, combat a La-7, a dedicated low-alt fighter.. maybe even more so than the Dora. It was almost as fast (maybe even faster at sea level?) and had good armament.
But the most striking difference lies in the weights of the two. While having similar dimensions.take-off weight is 3240 kg for La-7 and 4270 kg for D-9, IIRC.
That is a bit more than a ton! So wing loading favors the La-7 as well as power loading: the M-82 gave 1850 PS, the Jumo 213A gave 1750 PS to 2240 PS depending on equipment, setting and fuel. You do the math.
So what tactics the Germans must apply in a dogfight in order to have a chance to prevail?

 

[pbehn]

With the general consensus being that the late-war Focke Wulfs were among the best machines for fighter-versus-fighter combat, I wonder how could an Fw 190D-9, which had its best performance at low-to-medium altitude, combat a La-7, a dedicated low-alt fighter.. maybe even more so than the Dora. It was almost as fast (maybe even faster at sea level?) and had good armament.
But the most striking difference lies in the weights of the two. While having similar dimensions.take-off weight is 3240 kg for La-7 and 4270 kg for D-9, IIRC.
That is a bit more than a ton! So wing loading favors the La-7 as well as power loading: the M-82 gave 1850 PS, the Jumo 213A gave 1750 PS to 2240 PS depending on equipment, setting and fuel. You do the math.
So what tactics the Germans must apply in a dogfight in order to have a chance to prevail?

If there is that consensus I don't share it. All machines increase in performance and the FW 190 did. However the early versions had no match on the allied side, the later versions were circa 2000PS at maximum but the allies had several fighters designed for or developed to that output by 1944/45. Weight was never as important an issue as power, the Spitfire pretty much doubled in weight through the war and no one complained about its weight they were happy with the extra power. It was only in the last days of piston engined planes that weight reduction was addressed as a way to get the last extra drops of performance. The P51H, Bearcat and Fury/Sea fury were all lightened versions of their previous marques (or supposed to be)

 

[DarrenW]

During 1943, the C3 fuel got increasingly better, eg. this test mentions it as with rich rating of 140 grade (140 PN)....

Thank you for providing the links, they were very informative as was your reply. I will need to go through them again in more detail to understand them completely of course.

So in comparison to the C3 fuels of 1943, what octane ratings were the allies using for their aero engines during this same period?

 

[tomo pauk]

With the general consensus being that the late-war Focke Wulfs were among the best machines for fighter-versus-fighter combat, I wonder how could an Fw 190D-9, which had its best performance at low-to-medium altitude, combat a La-7, a dedicated low-alt fighter.. maybe even more so than the Dora. It was almost as fast (maybe even faster at sea level?) and had good armament.
But the most striking difference lies in the weights of the two. While having similar dimensions.take-off weight is 3240 kg for La-7 and 4270 kg for D-9, IIRC.
That is a bit more than a ton! So wing loading favors the La-7 as well as power loading: the M-82 gave 1850 PS, the Jumo 213A gave 1750 PS to 2240 PS depending on equipment, setting and fuel. You do the math.
So what tactics the Germans must apply in a dogfight in order to have a chance to prevail?

The La-7 was also very good at medium altitudes, 650-680 km/h at ~6 km. Power at that altitude was ~1450 CV, vs. Jumo 213A with ~1600 CV, both values are with ram effect, ie. for A/C flying at max speed. IMO - the LW pilot will be well advised to keep it's speed up and don't allow to be drawn into lower altitudes and into the turning flight. Granted, if the MW 50 is installed, the Fw 190D-9 should have had upper hand in all altitudes in speed and climb.
Perhaps the closest Soviet aircraft vs. the D-9 is the Yak-9U with VK 107A engine (if we discard the unrelaibility of the engine from the equation).

 

[tomo pauk]

Thank you for providing the links, they were very informative as was your reply. I will need to go through them again in more detail to understand them completely of course.

So in comparison to the C3 fuels of 1943, what octane ratings were the allies using for their aero engines during this same period?

Western Allied fuel was with 130 performance number (for rich rating; 100 oct for lean rating), thus named 100/130. Allies strarted using 150 PN fuel by spring of 1944 in Europe.
The figures for Soviet fuel are not easy to come by, they were usualy stating just '94.5 oct' or '95 oct' during the war.

 

[DarrenW]

My knowledge of WWII aviation fuels could use a little tweaking, but thankfully you helped fill in a few blanks for me.

 

[GregP]

I was not able to locate anything saying C3 was 140 PN fuel except a comment that 140 grade fuel was used for the test quoted above (Thanks for the link, Tomo!) because it corresponds to German fuel grades. The only tests I have seen rate six different batches of C-3 (Green) fuel as anywhere from 118.5 to 125 PN when rich. Five of the six rich ratings were 124 - 125 PN.

The tests found C-3 to be 95-97 Octane lean and 124-125 PN when rich. That is decidedly not 140 PN, but one would use 140 rather than 100 since 125 is higher-rated than 100.

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.

 

[tomo pauk]

A quick peek on a doc (here) states that 3-C* Rich mixture rating % of 130 grade for C3 ('green') fuel ranged from 110 to >125. I don't know the exact minutiae of what the '3-C Rich mixture rating % of 130 grade fuel' means, my understanding is that C3 fuel was as hi-oct as the WAllied hi-oct fuel of any given day of ww2. 125% of 130 = 162.

BTW:

... and British fuel gave early P-38s fits when they got to the UK because the engines were set up for U.S. fuels.

That myth is dead & burried

*has nothing to do with German C3 nomenclature

 

[DarrenW]

C-3 was also found to 40% aromatics (!), which is about twice that of British fuels. US fuels were less than 5% aromatics

I hope I'm not getting too 'scientific' by asking this, but how exactly do aromatics affect the quality or usefulness of aviation fuel?

 

[GregP]

Hi Tomo,

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.

To be sure, the P-38 had other issues, each of which were also solved except for the low critical Mach number. Part of the cure may well have been the turbulators installed in the Allison intake manifolds as well as new jets, but the combination DID fix the issue when the aircraft were used in the ETO or MED. PTO operations used U.S. fuel, so they never had the issue, and were also mostly conducted AFTER the original issue was found and solved. When I was at an Allison shop, we used ONLY the intakes with the turbulators for aircraft engines. When I was there, we didn't make any new tractor or boat engines, so I can't say for sure about them, but many tractor guys in Europe run fuel injection anyway, so the intake wouldn't matter since it is eliminated in an injected or boosted-injected setup.

I have no real dog in the hunt since the pilots I know who fly warbirds can't get either U.S. or British WWII fuels anyway, and they have to fly on the best they can get today. But the first-hand testimony indicates the situation could have been a real one. It WOULD be nice to know for sure, but I have no definitive source.



Hi DarrenW,

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.

If you cut down the aromatics, the base Octane number dropps unless compensated for by adding other additives, such as tetraethyl lead (hence the obsolete term "ethyl" for high-octane gasoline for cars). European fuels generally had more aromatics than U.S. fuels due to the sources of their oil. If the U.S.A. had sourced the base oil from the same places as, say, Germany, our fuels would have had higher aromatics, too. Of course, the refineries can ADD Benzene and derivatives to make any desired mixture. Current U.S. 100 / 130 fuel is 5.0% aromatics, as is 100LL. WWII U.S. 100 / 130 avgas had 3.0 ml/gal tertaethyl lead, and 115 / 145 had 4.6 ml/gal. The gallons are, of course, U.S. gallons.

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. Bottom line: if the performance number drops, you get detonation at a lower temperature. When that temperature drops down to within the range of what is seen in the cylinders, you get destructive detonation, and pilots HATE it when they go down and get captured due to easily-preventable failures.