How The Spitfire Mk XIV Compared to the K4 and Other Questions

[fastmongrel]

There is another report I have seen that puts the 'rich mixture' even higher than 120% of 130PN.

If the German fuel was rated using the same methods as Allied fuel how does this rich mixture 120% compare.

Certainly seems like the German chemists never let the LW down even with poorer basic supplies and round the clock bombing.

 

[tomo pauk]

I have never seen any documentation to indicate that C3 was better than 97/130 and that comes from British technical intelligence on the fuel tanks in captured or downed German aircraft. Officially it seems to have remained 96/125. In fact it started of at only 93/115 I doubt you'll find any. Where did you hear that claim?

They were struggling to make enough B4 let alone better the allies 100/130 fuel.

1st part is true, second is not.

150PN fuel is actually 110PN/150PN against which the Germans had 97RON/130PN (test figures not official ones). The PN means performance number and is a percentage increase in power possible when running rich. So allied 100/130 gave a 30% boost when rich. Allied 100/130 was in fact 102/130. Hence 150PN could create 16% more power than 130PN. That would get the Me 109K4 to 2.15 ata and certainly above 2.0 ata.

Or DB gets really smart, lowers down the compression ratio of the DB 605, so it can do eye-watering 2.5 ata.

Both the Mk VIII/XIV and the Me 109 had about 95 gallons/400L in the main fuselage tanks. The Spitfire VII/VIII/XIV added about 25 gallons in the wing leading edges and the Me 109 about 21 gallons in a supplementary tail tank. Little difference.

The MK VIII/XIV have had the LE tanks as-is. Rear fuselage fuel tanks were an tried tested thing for the 2-stage Spitfires, lack of the need (=LW defeated, Allies are near Paris, availability of Mustang Thunderbolt for the RAF) and current doctrine means they were never used, like it was the case for the RAF's Merlin Mustangs.
Was the rear tank of the 109 self-sealing, was it ever used as a fuel tank at all?

If the Luftwaffe wanted to do something crazy and of marginal utility instead of adding a 170 gallon slipper tank they could add 200 imp gallons or 900L of fuel in the form of 3 x 66 gallon/300L drop tanks to the Me 109, this in fact was used on reconnaissance versions of the Me 109. They might try something like a small 'dachelbauch' (dachhound belly, the German equivalent of a conformal slipper tank) tank say 150L combined with the wing drop tanks. No problem, but the Luftwaffe felt no pressing need to do so or felt it was of dubious utility. Useful for long standing patrols over an area yet still in clean range of base.

For the bolded part - here you are wrong. LW was never able to achieve air superiority above UK, above war production centers of the USSR (once the frontline stabilized more or less), and above anything that was 200 miles away from it's fighter bases, even above Malta. The 109, short ranged fighter, was the crux of the matter.
Attaching 900 L of fuel in drop tanks on a fighter that has 400-500 liters of internal fuel does not make it a long range fighter (as in Japanese or US terms), since whatever the fuel is in the drop tanks will be 'dropped' once the enemy is around. The Spitfire VIII/XIV with ~850 L of internal fuel and ~400-800 L in a drop tank is a far better proposal, even though some 30-40 imp gals (~120-160 L, or one of two of rear tanks) should be consumed before entering the combat.
Not too big a slipper tank in a fighter might be a good proposal of you fighter has a considerable performance advantage, not so good idea if the enemy can put in the air a decent fighter of his own. Spitifre already have had 30 and 45 gal slipper tanks (not self sealing IIRC), unlike the 109, BTW.

There was never a chance of an intercooled DB605L since adding 200kg of intercooler and radiator didn't make a lot of sense as opposed to adding 200L of MW50 in the case of the size restricted Me 109. The Me 109 had already accepted an engine size change when it went from the Kestrel/Jumo 210 to the DB601 and then DB605. Fitting the Griffon sized Jumo 213 wasn't possible.

There was every chance of the intercooled 605L, as it was chance for the non-intercooled DB 603L to became the intercooled 603LA, along with a whole host of engines that received intercoolers during their development. Your figure of 200 kg for the intercooler is way above board, eg. the cooling system (engine cooling + intercooling) for the P-51D weighted 663 lbs (~300 kg), the intercooler using maybe 1/3rd of that weight. The figure of 100 kg looks more realistic for a water-to-air intercooler, with further weight saving if the intercooler's radiator is located perhaps under the engine, in a bigger fairing so the oil cooler can share it too. Opting for an air-to-air intercooler further can cut the weight. Another option is the heat exchanger, that would require a bit bigger main cooling system.
Agreed that Jumo 213 or something similar would not fit on the small 109, the 209-II (or whatever was the name) received bigger wings, among other, so it can receive a bigger engine.

Since the DB605 consumed a little less fuel than the Griffon and since the Giffon had to operate on rich mixture (about 20% greater consumption) instead of using MW50 as a charge cooler there was likely no difference in range even if the Me 109 was forced to use MW50 as an Anti Detonant. The range corsing posted suggested the range of 460 miles was at a 226 mph cruise for at least part of the mission which is impractical for even escort combat duty in Europe.

This is what the Spitfire XXI was supposed to give, (not just) range-wise: link. Seafire 47 also carried rear tanks.

Plain drop tanks were the solution.
Many Me 109 developments, such as the in wing canon armament I suspect, were delayed due to the severe production stresses experienced by the Reich at the close of the war. The use of 4 canon seems to have been limited to the Griffon variants, maybe 700 produced during the war?

Plain drop tanks were partial solution. Greater internal fuel, as CoG-neutral as possible, was the real solution, from Zero and Ki 61 to P-47N and Hornet.
Spitfire V already have had 4 cannons as an option, not a very good one because of performance penalty and not enough of gun heating capacity. Later both engine power and heating capacity were much improved, but threat from German bombers decreased the need for such heavy armament for the Spitfire, though it was re-introduced in 1945 with the modified wing.
Small thin wing of the Bf 109 meant a redesign was needed in order to fit the MK 151 or 108, but it was possible.

 

[tomo pauk]

...Intercooling may have been heavier than simple ADI, but it never ran out. The performance afforded by intercooling was accessible at all times during a flight.

Use of intercooling instead of ADI in the LW would also mean that MW 50 does not need to be poduced shipped, meaning less of a logistical burden. Intercooling + ADI + hi-oct fuel + low compression ratio will offer the greatest power in an easily feasible way (talk Jumo 213E, Merlin V-1650-9, later R-2800), of course if the engine is strong enough to withstand that power.

The DB 605 was, in terms of capacity, the same size as the Griffon.

The 605 was a good deal lighter, that is both a good and bad thing.

The 170 galllon slipper tank was a ferry tank. Not for combat. The 90 gallon drop tank was fo combat, and the ADFU determined that a XIV was superior in all respects to a Bf 109G with the tank in place.

The doctrine was determining whether the 170 gal was ferry-only, not a technical issue?

I believe that the Mk 108 was a poor air to air weapon. While the round was heavier, it's muzzle velocity was only ~60% of the Hispano's. The Mk 103 was the great 30mm hope of the Luftwaffe, but it wasn't really sorted before the end of the war.

The MK 108 was probably a fine anti-bomber weapon, not so good vs. an aware and maneuverable target?
The MK 103 was a powerful weapon, but it's design meant it won't fit on the Bf 109 ( a redesigned MK 103M would fit, but it wasn't available until to late). The Ta-152 was able to carry it as a prop gun, since it added some 77 cm between the engine and cockpit.

 

[GregP]

That page 13 line is not a rich performance number.

It is the amount of T.E.L. per US gallon compared with US fuel. It means the German test fuel had slightly more T.E.L than US fuel did. The exact amount of T.E.L. is not the rich mixture performance number.

 

[Milosh]

If it is not the rich mixture PN then why does is say 3C Rich Mixture Rating?

 

[GregP]

Look at the units, Milosh. It says "3C ccs. T.E.L. / US Glns. in S2"

That means the German fuel had 16% and 20% more Tetraethyl Lead (T.E.L.) per US Gallon than US Fuel does when running rich. T. E. L. is not a performance number, it is an additive.

So we now know that the Germans had a bit more trouble than we did with lead-fouling in spark plugs if the pilots didn't pay attention to leaning. So ... they wouldn't want to spend 25 minutes taxying about before taking off and needed to lean more often when climbing and richen a bit more when descending.

Perhaps that's why the Fw 190 had a single-lever throttle ... automatic mixture to help with decreasing spark plug fouling. I you experience a LOT of lead-fouling issues, you might come up with a more automated solution for same, too.

A PN rating does not have units including ccs. of T. E. L. per gallon. It is a unitless number that means you can multiply the Octane rating by the PN to get the new rating since Octane numbers stop at 100.

One thing is for sure. We were very near the limits of fuel intended for engines that operate for long periods of time. There are fuels for engines that run for a few minutes or a few seconds, but aircraft needed to run reliably for hours. A Top Fuel dragster engine runs at high power for about 4 seconds at most these days. If they still needed to runs 5 - 6 seconds, then we would be back to 8,500 HP. That only reason we make 10,000 HP in a Top Fuel car is that the engine only needs to run about 4 seconds above idle.

The engines in Monster Trucks need to run several minutes and are mostly no more than 1,500 - 1,800 HP since they need to survive awhile and not die from just running.

The piston fighters needed to be able to carry enough oil and fuel to run for 8 - 10 hours and then get more of both fuel and oil and do the same for another mission out to 250 - 450 hours. That limited the fuel and HP to the levels we saw in WWII with the technology at the time. Today we could make the same size engies and get maybe twice the power, maybe not ... and they'd last even longer. But the Merlin, Allisons, DB's and BMW's weren't bad at all, and still aren't. They run great even today. I have only heard a Jumo 211 run twice in the former Doug Champlin Fw 190D-9. That was back in the 1980's. It sounded good, but they only had the idle circuit working. It could not be run at higher than idle power due to some missing parts, so it likley won't ever be flown as the guys who could solve the dilemma of the missing parts are getting very old and will likely pass away before anyone in power thinks to contact them and have them come solve the problem.

Probably Joe Yancey, Mike Nixon, Pete Law, Dave Cornell, and a few other guys like them could get it running, and probably a few older gentlemen from Germany and eastern Europe, too. Aside from these guys who KNOW the engines (and a few others aside from the above names), there are no or FEW new up and coming people around who understand these old engines well enough to even make them run.

I know one thing, Joe Yancey's method of doing basic cam timing and ignition timing is MUCH easier than trying to follow the Allison instructions. He does the same thing, but his explanation is in modern English and can be understood much better than the official writeup. I think it was written to confuse the Germans who read it, and you have to have all the books to get all the information. It was broken up into about seven volumes on purpose. If any 2 - 4 of them fell into enemy hands, they would not be able to keep captured engines running for long.

 

[BiffF15]

Greg,
Is the Champlin Fw-190D-9 the same A/C that is at The Flying Heritage Museum (Fw-190D-13)?
Cheers,
Biff

 

[GregP]

Yes, I thought they had it lised as a D-9 at some time in the past ... but could be wrong. Memory might not be quite what it used to be and I was just reading about the D-9. It is, in fact, a D-13. When Doug sold it, it was discovered that the wings for that aircraft and the one in the National Air and Space Museum had been swapped at some point in the restorations ... and they swapped them back. Now it is in Seattle. All I can say is Mr. Allen has a very nice facility and collection.

Doug used to start up one or two of his rare birds occasionally, usually at a private art show or the like and both times I heard it start and idle were at art shows there in the evening. In fact, that's where I bought my prints signed by Erich Hartmann and Saburo Sakai ... at an evening Champlin Museum art show. They also had a VERY rare P-40. It had only about 40 flight hours on it when it was flown to storage, and so was very original and pristine. Not sure where it went when Doug closed up shop. He was an interesting guy, but wasn't flying them and had a LOT of money tied up in them.

The Focke Wulf was a bit temperamental and would start about every other time, so I was lucky to hear it twice. Some people went to 3 - 4 shows and it never started while they were there. I only got to go to the shows because I had a friend who had a plane displayed there, a MiG-15 bis. He got tickets and was going to be out of town, so he gave them to me. Turned out pretty well as I got to see some rare things at each show that usually weren't on display, and met some of the big-name aviation artists ... and got a couple of prints. Still have them.

 

[Milosh]

It says "3C ccs. T.E.L. / US Glns. in S2"

It says: 3.25 ccs TEL / US gln in S2 = 116% of 130

In other words, in a US gallon of the C3 fuel analyzed was found 3.25ccs of TEL.

That amount of TEL (3.25ccs) in the US gallon gave a PN of 116% of 130, or if it was 4.00ccs of TEL, then = 120% of 130.

116/100 x 130 = 138
120/100 x 130 = 156

 

[GregP]

The Tetraethyl lead quantity doesn't equate to performance number ...

 

[mhuxt]

Milosh, the Germans tested captured fuels against their own C3 and B4, across the whole range of rich/lean mixtures - see the attachment on my post above for how the octane numbers compared according to the Germans' own research.

 

[GregP]

Hi mhuxt,

I've been looking through this thread and don't see your post above. What post # is it? I'm just curious since I haveseen reports on German fuels many years past, but can't seem to find the same ones today. Now when I find a good report, I save it ... back then, it didn't seem worth the disc space since discs were expensive. Comparatively speaking they're dirt cheap these days.

My first external hard drive was 20k bytes! And it wasn't cheap. Today I can get a 1 TB HD for less money ...

 

[BiffF15]

Greg,
I remember hearing about the wing swap! Cool they got that figured out. What keeps the motor from running above idle now, missing parts with the single lever engine control?
I have a few pieces of Art from the museum as well, picked them up at the Pheonix Air Races and brought them back in the Eagle.
Cheers,
Biff

 

[mhuxt]

Hi Greg, it's post #41, the one you bacon'd me for (thanks). The graphs show that by the Germans' own calculations it would not have been possible for C3 to have had 116% of the performance number of 100/130 at rich mixture.

 

[GregP]

Gotcha' and thanks. I downloaded that one at that time and I thought maybe I had another one on the line. More data is better, kind of like a few other things you could name.

Sometime in the past I found a report where they had tested six samples of captured German fuels and listed the test performance/Octane numbers. The samples varied from 1942 through early 1945 and were usually from 5 to 50 US gallons each. I'm still trying to re-find it. As I recall, it was 3 samples of B4 and 3 samples of C3. One C3 sample was a few points higher than the other two.

Alas, can't seem to find it again, but am still looking as I get time.

The reports I have now indicate C3 was 93 - 96 lean and about 110 rich, and had 4.26 to 4.6 cc of lead per gallon, with 37.4 to 38.6 % aromatics. It was 83 Octane base plus the additives to bring it up to the 93-96/110 rating.

The B4 was 71.5 to 74 Octane base and 4.5 to 4.75 cc of lead per gallon to bring it up to 89 - 91 lean, with no rich number.

I cannot recall the date of these samples and didn't record it at the time. Could have been early. To me, the difference between the 93 - 96 and the 110 isn't quite enough between lean and rich as our gasolines typically had a spread of about 30 points, but the German and American and British fuels were different and maybe that WAS the number. Just because we do it one way doesn't mean the Germans did it the same way. They used different bases, more lead, and MUCH more aromatics. Perhaps that affects the lean-rich spread, I make no claim either way there.

Lean and rich don't really describe it well. The US lean number is quite similar to the current US automotive (R + M)/2 method and the US rich is the rating for a supercharged, higher-compression, supercharged test engine. I'm not sure if the Germans used both a higher compression engine and a supercharged one to get their ratings. AT that time, things weren't all standard, and they still aren't, but we can at least understand and compare modern rating systems.

 

[Vincenzo]

from 42 to early 45 we have 3 different C3 in use, the C3 evolved a 42 sample would be different from a 44 sample and with different octane number

 

[GregP]

Hi Vincenzo. I have read that, but have not seen samples that verify it. I would not be surprised to see them. The airplanes themsleves changed specification every year or less throughout the war, so there is no reason to susect that the fuel wouldn't change occasionally, too. I DO question calling it the same name, but there was a war on and perhaps convenience rulled the day. If they made changes to a Bf 109G, they usually gave it a different dash number. Hence the Bf 109 G-2 through G-14 or whatever. Everyone, or pretty much everyone, in here knows that.

I really would like to see some tests of the various B and C fuels that show the differences, but have not been very successful at finding the data. Batch to batch numbers are not even the same. A fuel that has a lean rating of 87 octane might have the same formulation in 3 different successive batches and have real test numbers of 85, 87, and 88. Production was close, but not an exact science. The measurement might or might not have been exactly reproducible, I can't say because I haven't seen several tests of the same batch of fuel with different result sets.

That should come as no surprise to anyone since the airplanes themselves weren't exactly the same either. One Bf 109 F-3 might have a sea level top speed of 350 mph and the next one off the line might be 345 mph. All I'm saying is there is a normal expected variance in aircraft, and variances between batch-to-batch fuels was there, too. Collectively it wasn't great, but there WERE variances and the variances could result in both slightly higher and slightly lower ratings.

Even if the German fuels were to have lesser performance numbers than Allied fuels it wouldn't matter if they had "work arounds". In engines, that usually means more displacement for the same power. The Bf 109 always was a good climber, being a small plane with a big engine. Whether or not they ever operationally used 1.98 ata or whatever manifold pressure matters less than the actual airframe performance. If it could climb at 4,600 feet per minute, then the pilots knew they had a good climber on their hands regardless of manifold pressure or fuel type used.

It all boiled down to actual flying characteristics, not a competition to deliver the "best" fuel. It was much more important to deliver fuel than to deliver C3 fuel. If the Allies had run short of 115/145 fuel, I'm sure they could have figured out how to run the late model planes on 100/103 fuel had it been necessary to do so.

Likewise, the Germans ran short of fuel near the end of the war. I'm sure the German pilots would have relished getting some B4 fuel as opposed to no fuel. Had they done so, then at least they could have flown their planes.

 

[Milosh]

http://fischer-tropsch.org/Tom Reels/Linked/A5464/A5464-0560-0635 Item 5.pdf

Long report on German avgas Greg.

Wasn't hard to find using the link Vincenzo provided.

 

[GregP]

Thanks Milosh.

That's the report I came across many years ago and didn't save. As I remembered, the rich rating went from lower to higher. Looks like 110 to 125 - 130. That's not an equivalent to 115/145, but isn't bad at all. It is a virtual equvalent to 100/130.

Appreciae it. In times recently past I had the time but not the link. Almost no time these days.

Still, I've seen pics of a Bf 109K-4 with a B4 sign over the fuel tank. That tells me there were at least some late-war Bf 109K's flitting about on bomber fuel equivalent to early war fuel. It probably means a C3 fuel shortage rather than a desire to run B4. You could set the DB 605 to run B4 or C4, but it required a mechanical change and could not run either at will without having the change done first. In other words, it was configured to run either B4 or C3, but not either one at will.

I am given to understand the changeover wasn't difficult, but required a mechanic, the parts, and maybe two hours of work. That from an old Luftwaffe pilot who spoke at the museum some years back. Note he was a pilot, not a mechanic, so I don't know if it is accurate, but it is the only first-hand report I have ever heard. I'll take it on faith until we hear otherwise from a wartime DB 605 mecahnic.

Hey Biff,

As I recall, they have the idle circuit on the Jumo 213 engine, but the main jets, or equivalent for the fuel injection system, are simply missing. Could be the primary injectors.

So they can prime it and start it, but have no real way to accelerate it past idle speed. I'm sure a master mechanic could adapt an American or British carburetor or fuel injection system of some vintage to make it run ... but it would not be 100% completely authentic ... hence the reluctance. The adapter would no doubt require some minor modification, and should they ever find the genuine parts, then the modification would have to be undone.

With today's 3D printing, I'd think it wouldn't be all that tough to fabricate a 3D model and print a modified manifold for use with an adapted mixture device, and they could save the original for use when and if they ever find the real parts. That option wasn't really available 25 - 35 years ago, and it offers us a chance to see a real Jumo 213 run and fly should Paul Allen ever be so inclined. To date I don't think he is, but maybe ...

 

[Milosh]

Most K-4s used B4 fuel.

Once did a count of 109s and 190s for Jan '45. Can't remember the number but the numbers were basically the same. The BMW801 required C3 fuel.