Kurfürst

Ok, so its a yellow spec sheet, got it. Well at least it confirms two things : a) the specs were understood for mean weight of 7106 kg (cc. Half ammo and fuel) and b) their overlay curve seem to confirm that they were a sort of mean avarage/crossing point between the prototype and BS310. My conclusion seems to be correct then - its extremely likely that the air intake efficiency is simply far too high in the current DCS model because its based on a small sample on non-serial production results in which weight corrections may have bern also ignored, and that in the end results an artificially increased full throttle height and abnormal performance achieve well above full throttle height realistically achievable with the Spitfire Mk IX LF in standardized condition.

What does it relate to then? Since when? Can you qoute where I said this? All I say is that they need to be taken into account when assessing the subject, not ignored at a whim. What do you suggest then - ignore the all the results of test that were all made on planes in serial production standard, and by some weird logic, rely only on two planes tested, which even the test themselves say are not representative of the serial production standard? I said in my first my first post that BS 310 sounds reasonable, since it agrees with a) the nominal British specs for the IX LF and b) it is actually falls between the highest figures achieved by the experimental machines and the results more typically achieved with serial production machines in the UK, in the USSR and in Australia. There are 7 flight tested machines there on the graphs. 5 of them are serial production machines, and 2 of them are prototypes with usually high full throttle heights. You seem to be on the opinion that out of the 7 tests, its best to "forget" the 5 serial production machines and try to match the speeds of those two weird prototypes. The British who tested them had a different view on this. The report on MA 648 says: External equipment of the above four aircraft was similar with the exception that MA.648 had the new pattern of air intake. It will seen that the above full throttle heights vary considerably. Differences in ram effect due to speed variations account to some extent for this; for instance if the speed of JL.165 were increased to that of MA.468 the full throttle height would be increased roughly 500 ft. The effect of difference in ram effect on the other aircraft would not exceed 150 feet. The mean full throttle heights for BS.310, JL.165 and BS.543 are 9,200 ft. in MS gear and 20,300 ft. in FS gear, but the engine of BS.543 has full throttle heights far above average. Even then, the full throttle heights of MA.648 with the injection pump are above average by 200 ft. in MS gear and 800 ft. in FS gear. The new type intake on MA.648 is expected to reduce the full throttle heights by a small amount, so these figures may be rather pessimistic. The improvement is attributed chiefly to the reduction in pressure losses occuring before the air enters the supercharger by the elimination of the choke and other obstructions of the normal carburettor. Owing to large variations in the performance of the four aircraft tested it is not possible to obtain an accurate value for the improvement in performance but the above quoted figures for increase in full throttle height give an average increase of about 3 mph. around the full throttle height. The only satisfactory way to obtain exact figures would be to repeat the tests with the normal carburettor substituted for the injection pump. When this was done on Spitfire VB W.3322 (Merln 46 S.U. Mark I injection pump), the increase in speed at full throttle was about 5 mph, and the improvement in full throttle height 1300 ft. The increase in full throttle height indicated by the present report therefore seems to be pessimistic. Is it another experimental plane that never saw service in this condition or a plane in serial production standard?

Well take a look at the graph on which I also added the full curves of JL 168, MA 310, JF 973 and the unknown serial no. IX LF measured by the NII VVS, they are all in close agreement. Its quite clear that all the serially produced Spitfires ever tested all reach their full throttle heights in the region between ca 19 000 - 20 000 feet. From your graph I can only see that your model simply ignores the results of serial production aircraft test results and reflects most closely the performance obtainable only with non-standard prototypes and experimental machines: BS 543 and MA 648. Again, and I must stress this, since there seem to be a bit issue of miscommunication or parallel talk - the issue is not the top speed (such as the the lower top speeds typically obtained with serial production Spits compared to the optimistic condition prototype machines - such is very much expected with mass produced machines). Of course always an easy solution to ignore the majority of real life test results and accept only those that fit in the model. If I take only the high values into account.... then the high values I get in my calculation will look normal. :music_whistling: The issue isthat the altitude those speeds are reached: both BS 543 and MA 648 achieved their top speeds way, way higher (21-22k feet) than all the other machines with the same engine tested. Its actually even explained in detail in both flight test reports (for example MA 648 had experimental air intake - why take this as basis..?). The British testers made it very clear that these altitude results are very high and unusual for the type, yet for some reason, the current DCS Spit model achieves even greater altitudes... the issue will be even greater with climb rate as a result. CONCLUSION: its extremely likely that the air intake efficiency is simply far too high in the current DCS model because its based on non-serial production results, that result a ca 2-3000 feet increase in the full throttle height realistically achievable by serial production machines.

For what is worth, IIRC the Soviet tested in real life one of the thousand IX LFs they received and found the turn radius to be 235 m (IIRC) and the turn time 18 seconds at 1000 meter altitude.

So, is the opinion that full throttle height in the model seems to be about 3000 feet too high reasonable?

I sure do not have intricate knowledge of it, though I think I get the basics of the process. However, I do not think that the "full throttle height in the model seems to be about 3000 feet too high, here is why" is such a complicated message either. I am not talking about absolute speeds (though that is indirectly effected), nor comparison charts, nor margins of error in the measurement - nor any assumptions on my alleged lack of background in doing engineering measurements for that matter... and yes, I am quite happy with my 109K since its no longer a 109G. :p Anyway, that's just my point and I have made it already.

I already said in first posts that the BS 310 tests should be what it looked like - after all the Brits accepted that as the "official" figures for this type. I am sure YoYo has that, but its his call.

All correct expect my opinion is actually based on, oh wait, times goes so fast, 16 years of "I think" - research & analysis - and I know the BS 543 and MA 648 tests details very well and would never use them as straight reference. And if I see data that matches them, "I think" I know where the problem might be. OK - then let me put my point plainly - the current DCS figures only fit the full throttle height characteristics two planes, a prototype, and an experimental setup. It does not fit in with any of the serial production planes FTH characteristics tested and I am pretty sure even back they could measure altitude with better than +/- 3000 feet accuracy. The fact that the DCS model closely matches these proto/experimental planes suggest they were used as a basis for performance model. And if this is true, it is simply a very much possible source of multiple small errors in the FM I wished to point out in detail and I leave it at that whether they are fixed, modified or left as is. If its not true, we are left that the DCS model does not fit results of serial production planes as of yet, for an unknown reason.

Yes - using the above example, imo realistically the curve should start to drop off after 8000 feet. MA 648's airspeed dropped of later because it experimented with a new type of carburetor that was better, but it wasn't used on serial planes so why is this the reference...? Or if used for example as a source to establish drag - why not correct/adjust aspects (FTH, air intake effiency) we know to be different from serial planes accordingly to fit known results of serial production standard? Speed effect may not be so great (say 10 mph on these selected altitude bands), but effect on climb is very significant.

I do not believe in this measurement error, its a rubber arguement anyway, fits all situations and sizes. And these measurement errors only show in the two references chosen - the prototype and the experimental plane...? Yes, thats the point (hsitoric charts also gave it as 20 000 Feet with 400 mph RAM). Normally measured range of FTH with serial production Spits cc 19.5-20k feet. Only prototype BS 543 and experimental MA 648 is higher, both stated in report, why (carburetor changes - not serialized apparently) The 23k feet is actually my (rough) reading from your first curve on DCS model Spit. Second shows it closer but bit above even BS 543. My question is why is DCS Mark IX full throttle height (and resulting performance) cc. 2500-3000 feet higher than a) measured in real life on all serial production IX LFs or VII/VIIILFs - expect the two proto/experimental planes oddly chosen as references b) theoriatically possible with cc 404 mph ram shown by your calculation c) theoriatically possible with 400 mph ram shown by WW2 RAF calculation for Merlin 66 If you say 3000 feet deviation in full throttle height is small difference - sure, please increase then the FTH of existing prop jobs by this amount. See what gives from that... ;) P.S. Yes weight does have very minimal at low/medium altitudes but its the high altitude (FTH and above) I am talking about where this effect is increasingly important. See graphically this chart for the 109 http://kurfurst.org/Performance_tests/109G_Leistungzusammenstellung/LZS109G_Blatt23_weight-effect_speed.jpg Since the DCS model increasingly diverges from the reference, I guess its worth checking wheater this is because DCS current pre-FM models 100% weight based on raw data for 95% weight.

Basically the problem is that the reference data is an early prototype, with a mix of a late experimental type, that, as mentioned in the report and testified by later testing results, produced abnormally high full throttle heights than the actual serial production machines. Its very visible even on YoYo's graphs as well. The DCS pre-model produces even higher ones. This abnormal increase in FTH will gradually boost the performance and operational altitude range to surreal levels, but it also has some effect on low/medium altitudes. The Mk IX LF was low-medium altitude aircraft with an engine that had a relatively low rated altitude - 16 000 feet. For DCS, for some odd reason the BS 543 IX LF prototype was chosen as reference, but following its trial the RAF re-did the trial with another aircraft, BS 310, and again for some reason, choose the data, or at least very similar data to BS 310 as the reference performance in its official datasheets. The RAF itself acknowledged this. I am not criticize how it fits to that reference data, I am criticizing that the reference data itself does not fit very well in the majority of the data. Namely, the FTH is too high, all the normal production planes were in the order of 19 500 feet, not 23 000 or more... It can be seen that the DCS model increasingly diverges from even that flawed BS 543 data as altitude increases... which I believe is partly because the reference data was flawed to start with (engine was abnormal when measured in 1943), and party because the weight corrections are more than likely not have been taken into account... which will yield very small effects in low or moderate altitudes, but will be increasingly noticable with altitude (=flight attitude) increase. Its not a single issue, I believe its a cumulative issue. I fully believe that YoYo's calculating methods and modelling is probably sound (which is why it is not very difficult to find possible bugs - it works and reacts like real life!), but IMO with the choice of reference data and the particular pitfalls in that data made several small margins of error that add up in the end.

"Taktik ohne Technik ist hilflos – Technik ohne Taktik ist sinnlos." I agree. Now I suggest that we quickly get back to 'DCS Spifire Mk IX preformance' before the schoolmaster arrives. ;)

Strike out "early" from the sentence and you have it right.

Both BS 543 and MA 648 were experimental setups, never serialized. That's a fact. And its not a particular surprise that their results are similar, since both plane had setup/modification of carburrator that gave them much higher full throttle heights than normal planes as you have probably realized yourself. That is the problem if they are reference values, these factors had to be taken into account. For example MA 648's report specifically states: "These results compare favorably with those of other Spitfire LF Mk. IX aircraft, which fact is attributed cheifly to the higher full throttle height obtained with the S.U. pump." So MA 648 had a new SU carburrator, it gave the plane higher FTH than normal planes, which gave it of course better altitude performance. But this will get even more funny when you realize that BS 543, the prototype IX LF with the normal Bendix carburetor (but set to too high engine mixture) had even higher full throttle height (cc. 22k ft) than the experimental MA 648 (21k ft by ca. 1000 feet)...! In fact the BS 543 report clearly points the reasons for that out: "The powers of the RM-9SM and the Merlin 66 engines in F.S. gear should be identical, since the high speed supercharger gear ratio is the same. It will be seen that on the climb, the performance and boost pressures were similar, within the limits of experimental error, but in level flight above the full throttle height the Merlin 66 engine was developing about 1 lb/sq.inch higher boost pressure than the 9 SM engine, with a consequent higher full throttle height and improved performance. This discrepancy must be due to variations in the manufacture of the engines and possibly of the air intakes, but it should be borne in mind that any small differences in performance of a high compression ratio supercharger or of the intake will be more noticeable at high speeds because of the increase in the dynamic head." These results obtained by BS 543 were by 2500 ft higher ft than any of the serial production M66 aircraft tested, which all but these two gave FTHs of about 19 500 feet - which btw matches RR's own engine curves and full throttle heights given for 400 mph rammed conditions (20k ft). And evidently the current DCS model has even even higher FTH than the better-then-even-experimental-carburattor-plane, by another 1000 feet. In fact 3500 feet higher full throttle height than what is normal, explainable and consistent with real life tests... So in the end we can conclude that the evidence points to that current DCS "Experimental Spitfire" model overstates greatly the FTH and thus high altitude performance, even though the real aircraft's peculiarity was that it was produced with an an engine optimized for low altitude performance and had a relatively low full throttle height and reduced supercharger gear ratios (5.79 to 1 & 7.06 to 1). This is not "nitpicking on 1-2%" (although I do mention that if we have 1-2% lower specs for one plane, 1-2% higher specs for another, it adds up and gets significant). Due to the various errors in measurement, but also ignoring the peculiarities of the tested planes, each adding to a systematic error margin of higher FTHs than should be stack up and in the end result, in the DCS model s a full kilometer different (better) full throttle height than it realistically should be and corresponding effects on altitude performance. This is not 1-2% error, its 18% in FTH... but hey, no biggie, right? So lets just have a K-4 with a 9000 meter full throttle height (18% error) instead of 7500m in the specs, OK? Nobody fights there, as in not that that altitude regime would be the place where the P-47 or later VEAO XIV would enjoy better altitude performance. ;) I mean, yeah, it would effect top speed a bit too, as in increase it to about 740 km/h at this new, somewhat flawed FTH that's only 18% greater than it should be. :) Of course if all the data is derived only from select prototypes and experimental planes that had better full throttle heights than the normal planes (and understandably such "representative" trials are attractive for Spitfire fans ;) ) and all the serial production results are ignored and not crossed check, such flaws are bound to happen. See the modified chart I attached which includes serial production Mk IX LF aircraft for comparison with DCS model and "reference" figures for the prototype and experimental machines... its very easily seen that both the serial production BS 310 and JL 165 (despite difference in speeds, which is probably down to drag difference betwen individual planes, but lets ignore that as normal serial production variation) both resulted in practically the same full throttle heights slightly under 20 000 feet. P.S. For some reason the Brits had the annoying habit of correcting level speed tests to 95% take off weight - this woudl, very rougly correspond to half fuel / ammo load on the Spitfire. For example BS 543s trials notes: All results given in this report have been corrected to standard atmospheric conditions by the methods of report No. A.& A.A.E.E./Res/170 (which incorporates A.& A.E.E. Memorandum dated 27.8.42). The level and speed results have been corrected to 95% of the take-off weights by the method of the same report." In practice this means very little in speed in low altitudes, but with altitude it gets significant because a lighter plane needs less angle of attack to maintain altitude, thus has less drag and is faster. Bottom line - if British trials are used, the level speed results, particularly the high altitude results cannot be used directly for 100% take off weight model, but need to be adjusted accordingly. I believe this might also attribute to the abnormal high altitude results in the current "Experimental Spitfire" model. ;) But I could be wrong, but then please explain how an engine (Merlin 66) with 16 000 feet static FTH (4876 m) gets a rammed FTH of 23 000 + feet (7000+ meter). And why go all the fuss with high altitude engines at all when a low altitude engine can do both! :)

It will run circles around anything anyway. So IMO it would kinda add some spice to the current mixture.

Extremely poor choice IMO since subsequent reports (see report BS 310 w. M70) and the BS 543 curves make it clear that the engine of the prototpye BS 543 was operating on too rich mixture, therefore it had an abnormally high full throttle height and improved low/medium performance at low medium altitude. Very higher altitude performance suffered somewhat. BS 543 also had an experimental propeller that was never serialized and achieved performance far in excess of ALL other Spitfire IXs/VIIIs tested. Take a look of climb curves of BS 543 at higher altitude, there is a break in the climb curve - apparently the mixture that was getting too rich there. MA 648 is an even poorer choice since its representative only of an experimental plane with a type of injection carburetor that never saw service in the end (all Merlin 66s were produced with the Bendix Stromberg injection carburator, not the SU type carb), hence the much higher altitude performance than normal. That plane never existed in service. IMHO BS 310 results should be best choice as reference, since this one was a control flight for the odd results with BS 543s and the results obtained (404 mph - still pretty much on the high side considering no other serial production Mark IX with the Merlin ever seem to have been capable of reaching or exceeding 400 mph) were, in the end, accepted as the official reference specifications for the Merlin 66 Spitfire IX by the British Air Ministry. Also of interest is the results obtained with serial production Merlin aircraft in reality - 397 mph, 389 mph (IX LF JL 165), 385 mph (Soviet Mk IX LF), 394 mph (RAAF Mk VIII LF JF 934 - extended w. tips though) Of course there is nothing wrong with using BS 543 and MA 648 as reference if you do not name Spitfire Mk IX. Name it a "an experimental Spitfire with an experimental propeller and and experimental carburetor with too rich mixture that gives you abnormally high powers at low and medium altitudes". ;)

Solty, you are correct, but its a bit about different standards, "apples and oranges". Power depends on the reference altitude - the Germans and Russians usually gave engine power at SL, but it actually peaked a bit higher than that because of the power curve of the engine increasing a bit after SL... for example the nominally 1475 PS DB605A peaked out at 1550 PS. The Western Allies usually gave it at the peak altitude (and sometimes gave an "international" rating that was lower, too which must have been derived from some cruise rating..?). So it just really boils down to different customs (and metric units, too, see metric horsepower vs mechanical horsepower) In any way, I think YoYo meant to point out that "its a feature, not a bug". ;)

:music_whistling: :thumbup: Yeah, uhm, good idea CHDT, I agree we need to have modelled the G-6 and A-8 for, uhm, balance, NO, historical, yes HISTORICAL reasons, as it is also not fair to Allied fliers us only have to choose from the K-4/D-9 and thus be FORCED upon to use overwhelming power. Addition of other models of 109/190s should be thus absolute modelling priority of course, and also, it should be FREE, since I for example MISTAKENLY wanted to buy a historically correct G-6 originally, and look what happened. A K-4. I was deceived, you see...! I need to be compensated with a.... uhm... free G-6? Oh come on, the TF 51D is free, too. We need to balance it with a free Luftwaffe plane. :music_whistling:

Its not the most powerful 109. That would be the fully rated 2000 PS model. As of now, we only have the 1850 PS model ;) On the other hand you have the best P-51D that is possible, too, a late production block from March 1945, albeit like the 109K, not running on the highest historical USAAF boost rating allowed - but it has gyro sights, fixed dive charatartistics (earlier ones would have a tendency to porpoise in dive, you do not have to struggle with that), metal control surfaces, rear warning radar etc... In April 1944 there were no P-51Ds, just B/C variants without bubble canopy and often with just four machine guns. The D did not come until June-July, neither were any but testing examples running on 72" until then... Specifically speaking - the variant we have in DCS did not come until about April.... 1945. On the other hand the P-51D we have is modelled after the most optimistic performance numbers there is for 67" Hg boost performance, with SL top speed of 375 mph. In fact most trials showed about 10 mph slower realistically achievable top speeds, some as low as 359 at these ratings, and this 375 mph is quite close what was realistically achievable on the highest boost allowed. In fact, you already have a very late production, fully upgraded 51D model from the wars end, modelled after very generous reference base specifications. Those who want to "re-enact" the one sided affairs and their guaranteed outcome that were the 1944/45 air combats should start servers that make sure that P-51s at least outnumber Luftwaffe planes 10:1 on that server and should start in the air above the airfield they are trying to take off..... and then wait patiently for the LW to be seen (also historical :p ).

I believe it was internal parts differents mainly, afaik 50% of the components were redesigned. IIRC for example the manifold pressure regulator was from the 603, and the lubrication system was also redesigned, this also changing the external dimensions of the engine (hence why you see those tiny chin bulges on 605D powered G10/K4). Pistons I believe were also different. In contrast of the 605A, the D traces back its development to a long line of DB 605D variants that were parallel development / complete re-design to the 1941 605A from 1942 onwards. Supercharger gear ratio might have been very slightly different, I do not know (I am not sure if even there are documents showing) , but the power output curves available show they were very similar even at high altitudes, which is probably due to tiny differences in CR and piston design, boost, rather than supercharger speed ratio. Re stop gap, the first AS engines in late 1943 were basically the DB 605A block fitted with the more powerful supercharger of the DB 603A. Then in the spring of 1944 the 605A block was combined with MW boost and designated as ASM. I believe the later variants you refer to, ASB/ASC appearing in late 1944 were basically a hybrid of once again re-used DB 605A blocks and 605D components, a bastard/hybrid solution much like the G-10. And, from October 1944 you can see the 605D powered G-10/K-4 dominate the production lines, even G-14s are largely discontiued.

The handling shouldn't be all that different since the plane still has the same or very similar wing size and planform, control surfaces and similar center of gravity, which largely define how the aircraft should be handling. There have been some improvements to improve stability, both on the ground and in the air but they would not change the overall picture - for example the K-4s long tailwheel and shallower ground attitude make it easier to control on the ground. The K airframe wasn't just to standardize the G airframe, it was to improve upon it, both in aerodyanmics and with small, but very numerous minor modifications. Many of these were soley practical (like re-arranging the radio instruments), but in the end it meant that different jigs and parts were needed, and re-tooling to producing K airframes would have meant production time losses. So in the end only the Messerschmitt plant in and around Regensburg assembled them en mass (Erla produced but a few dozen at best near the war's end). The other main difference was the engine. The K series prototypes in 1943 still had the same DB 605A engine, but serial production variants had the 605D series, which can be itself be consider a semi-new engine but at the very least, a major re-desgign. It had 1+2 subversions, the very early 605DM at 1.75ata and 1800 PS, and the major production variant 605DB/DC, which was the same engine with different settings. The DB variant was set to lower boost and power (1.8ata, 1850 PS), but could rely on either lower or higher octane fuel (B-4 or C-3), while the DC setup had greater output (1.98ata, 2000 PS output), but when set up as such, it could only run on 150 grade C-3 synthetic fuel. Since the DB/DC introduction coincided with some QC problems at the DB factory (faulty engine assembly and mis-sized engine parts), the LW initially put on hold the latter DC version until March 1945 (which roughly coincides with the introduction date of our P-51D-30 block in DCS ;) ) and until further proof testing, mostly the lower boosted DB version was used on the frontlines. It wasn't a high octane fuel availability concern, since C-3 was the majority (of what little remained, by late 1944) of German synthetic fuel production, but running the DB config on C-3 brought absolutely no power gains. Now, despite the serious differences in design the engines performance (power output) is in fact very similar to the 605AS (ASM, ASB, ASC) series engines that were fitted to the 1944/45 109G series (no coincidence, since these engines were an early stop-gap solution until the K/605D combo arrives, using some parts from them), so in the end the performance characteristics are broadly similar, except that the K's speed characteristics are better because of the less drag. So you had on one hand a desirable new engine and it was felt that standardization of spare parts is necessary, but the problem that many factories cannot re-tool to producing K series airframe without major production loss. Hence the birth of the G-10, which came out and built in parallel to the K, albeit in different factories, and was, basically, a K's internal components (such as engine and its new 2000 Watt transformator type) inside a G series airframe. Weight in similar configuration was in fact not not very different, the K-4 always had the heavier MK 108, the G-series only in the /U4 subtypes, so the basic G series was somewhat lighter but for example the similarly (MK 108) armed G-10/U4 and the K-4 was only some insignificant 19 kg apart (3343 kg vs 3362 kg) and had the same engine. In fact climb graphs for the G-10/U4 show it had practically the same performance as the K-4, albeit it was a bit slower. There was of course, the G-14 itself, which had the old DB 605A engine, albeit with MW boost designated as /AM and a helluva lot more power, which was less perfect aerodynamically. The main thing about is however that while the G-6/AS, G-14/AS variants, the G-10 and the K-4 had high altitude engines and high altitude optimized broad propellers, the basic G-14 had an engine and propeller optimized for low- and medium altitudes. Up to about 4-5000 meter, where most dogfights in DCS or other online sims would happen, it had equal or more power and a propeller that could convert more of that power to thrust at these lower altitudes than the high altitude specialized birds, and was lighter. Hence despite being the oldest of them all, it actually had the best low/medium altitude dogfight and climb performance of all of these.

Works out 296 kg for the main fuel tank (0,74 kg / lit), 85,1 kg for the rear tank if fuelled with 115 liters of fuel. 85 liters MW in the rear tank should be about 76 kg, if I calculated with a density of 0,896 kg / liter, which seems reasonable since it was a 50/50 mix of water and methanol. Methanol is lighter (0,792 kg/lit) than water, which is 1 kg/liter in SI at +4 Celsius IIRC. Possibly. 4 bars seem to be a bit much anyway - I mean car tires are pressurized to just about 2-2,5 bars and rock solid when they are pumped and strong enough to hold a two ton vehicle. Should not the MW pressure gauge show how much is that pressure actually, iirc something like 1,8...? P.S.: One of the thing that always amazed me when people talk about how "strong" engines must be if they can withhold such "extreme" manifold pressure like 2 ata at over. In reality it is not that much pressure, even car tires can hold it easily... its the insane power and torque of the engine running at such boost pressures that is hard to contain by the bearings and connecting rods...

I believe it was for CoG reasons, really there is not much else I can think of why placing a heavier equivalent weight liquid in the same place on an airplane. In practice it probably wasn't followed so strictly, there is a Brit intel report in my site noting they found 100 liters MW in the tank. There were tolerenace on CoG for a reason: human nature. :D 85 liters / 180 lit/h works out to me as 28.3 mins, but its again a bit reserve since the easy-to-remember instruction was to "use for ten mintues at a time, twice at max" and you better have reserve to account for sloppy loading for example, since when MW runs out knocking and detonation could occur with B-4 (less so with C-3) and this could damage the engine. I suppose like fuel tanks, you could probably not use the last liters either.

Though the EZ 42 was fitted to the Me 262, IMHO considering the ballistics of the MK 108 it would make as much sense as fitting a sniper scope to a a sawed-off barrel shotgun. :lol:

The manual is wrong, on many accounts, sadly. It seems to be based on varied sources, including Wikipedia... the only 109 that had a 250 liter tank was the 109B, subsequent models progressively enlarged the tank. The K-4 had a 400 liter main tank, a 115 liter aux. dual-purpose tank (fuel or MW, in latter case, only 85 liter is filled to maintain CoG) mounted in the rear of the fuselage and a 300 liter droptank. Since both of these latter two extra tanks feed into (top) the main tank, you only need one 400 liter gauge (and never have to worry about switching between fuel tanks).