Fw-190 Prototype engine changes

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Excellent graphs, delcyros. I also found the very same when plotted the results on graphs.

May I ask what program you were using? It looks excellent for these purposes! 8)

PS: Also see in attachment Rechlin's Spitfire IX w. Merlin 61 measurements. Apparently, the variation in level speed was similiar as in the case of the Bf 109G.
 

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I use curve finder for basic input and drawings, SPSS 15.0 for computation of the mean curve and Coral Draw for all text put into the graphics.
Differences between flight tests are quite common.
Here are the Spitfire V model flight tests published on Mike Williams site compilded to a single graph (no tropical Spit V). All speeds are corrected forposition error and compressibility. The boost rating is +9 lbs.
I added the few Bf-109 F4 datas from german, soviet and british sources.
I also added the Bf-109G0 speed trials with Db-601E. It´s a tad bit heavier than a -109F4 (pressurized cockpit, more armour) but otherwise aerodynamically comparable. The mean curves for the Bf-109F4 are faster at all altitudes compared to average Merlin 45 driven Spitfire V. The difference get´s even mre pronounced when applying full 1.42 ata celarence to the 109 (about feb. 1942) as opposed to +16 lbs boost clearence for the Spitfire V.


As a note to methodology:
The top speed does appear as a satter of points clustered around a specific range of speeds and altitudes. The mean curve is the mathematical expression of an weighted average, adjusted for inertia factors of datapoints beeing away from it.
The more flight tests we have, the more reliable is the mean curve. It may not be representative for the models best individual performance but it does match up well with performances of an average aircraft.
Personally, I don´t like to exclude very poor or good performing planes unless there is a very good explenation for them. The explenation has to be within certain limits, f.e. I don´t think that an engine, delivering less power / full pressure height than the specifications do call for does qualify here. It is reflective for a band of differences in production quality, too.
 

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I am coming around to the conclusion that DB switched to DB605 engine production too soon. Prior to June 1943 the DB601 engine produced approximately similiar HP. And it was a bit lighter. Why not stick with the Me-109F-4/Z until the summer of 1943?
 
I don´t know why exactly. Messerschmidt proposed significant performance increases with the Db-605 and appearently relied on 1.42 ata clearence to justify the switch to the Db-605 (one of the Bf-109G1 speed projections hit 700 Km/h on 1.42ata).
The Bf-109F4 was competetive through 1943/44 as well. It appears that in Norway and Russia as well as in Italy, Bf-109F4 were kept flying right to the end of ww2 in some cases. With GM-1 injection, the -109F certainly was a match for a Spitfire HF IX or P-47, respectively. Unfortunately, MW-50 injection was never tried in combination with an Db-601E.
Staying with the Db-601E should have been the option until the Jumo-213/Db-603 driven Fw-190 reaches frontline units.
 
The weigth difference between the DB 601E and 605A was marginal - less than 20 kg actually. The 605A could still produce about the same output at low levels at 1,3ata as the 601E at 1,42ata, but the output of the 605A at altitude was slightly better.

Similiarly, the weight difference between the 109F-4 and G-2 in practice was also very small. On paper, the F-4 weighted 2890 kg, the G-2 3037 kg, but but all likelyness the F-4 weights do not include the armored windscreen (8,5 kg which was added externally, and caused extra drag, on the G it was internal), and the weight of the 33 kg of dural aluminium armor behind the fuel tank on the G, which was also retrofitted to the 109Fs. Similiarly, late F-4s used the larger G oil cooler.

So I would say the rest of the weight difference, apprx. 100 kg was made up by the structural strenghtenings of the 109G wing, which the 109F would need anyway, plus the prerarations for extra stores for gondolas and other, the new propeller.

Add to that the usual variation between planes, and I would say the early 109G, even if not a step forwards in terms of performance, was no worser performer either, with some useful features (more versatile, stronger structure, GM-1 ready). And, as soon as the engine's full ratings would be cleared, it would be a better overall performer.

IMHO the real pity is that the new model did not get all the aerodynamic improvements originally meant for it (wheel well covers), and that the engine was de-rated for about a year. Should these be available, we would be talking about a ~700 km/h fighter, in 1942... lots of wasted potential, in other words.
 
Hi Kurfürst,

I am not convinced that the difference between Db-601E and Db-605A is that significant. It´s to some extant true that the FTH for the -605A is higher and it´s output is greater, too. But certainly not to a comparable degree against the -601E´s output at 1.42ata.
The 601E´s power at Sea level and 1.42 ata was 1420 hp, the -605A delivered only 1310hp at 1.3 ata, slightly more than the -601E´s power at 1.30ata, too.

Running a dsicriminance analyis for my dataset of Bf-109G1/2 speed trials aviable, I have come across with some interesting problems, which require an interpretation.
Statistically spoken, the scatter for the Db-605A at Kampf- und Steigleistung does not show a uniform cluster but two rather solated ones.
If I draw two lines around their points respective inertia´s, I get two very neat graphs which agree quite well with the -109F4 datapoints (blue) at 1.30 ata and 1.42 ata, respectively.
Hennig should be able to verify whether or not the lines doe coincide with power related speed calculations on base of the ata-ratings. I know IT DOES cntradict with the information given in few primary sources (ERLA-tests) but I believe there might be a critical explenation for this, more to this later. I would rather like to hear Yours and Hennigs comments first.
 

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The 601E put out 1350 PS at SL/1,42, the 605A 1310 PS at SL/1,30 ata. See attached graph for the power curves. Net weight is given in a British paper as 1640 vs 1680 lbs.



I am not sure if I get it correctly, but I guess the two groups of scatter probably relate to differences in test and tested aircraft conditions - whether the aircraft had semi-retractable or fixed tailwheel, and the position of the radiator during the level speed tests, or wheter we speak of a G-1 through G-4 or G-5/G-6. I can only confirm that all Bf 109G-1 through G-4 tests refer to 1,30ata rating (Finnish trials, all German tests, Soviet trials). I have not yet seen a single 1,42ata test for the G-1/2/3/4 models, save for the British trials in the desert on Black Six, but that aircraft may have had some issues as to its condition.
 

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the -605A delivered only 1310hp at 1.3 ata, slightly more than the -601E´s power at 1.30ata, too.
Click to expand...
How can this be? The DB605 had greater displacement and an improved camshaft for higher RPMs. The engine should be significantly more powerful.
 
Kurfürst, are You sure that the VVS trial was with 1.30ata? A soviet book rates the G2´s engine power at 1475 hp/SL, which would imply 1.42 ata rating for the 666 Km/h figure attained by the test.
Ununderstandably, the altitude rating is given with 1250 hp, altough no specific altitude is mentioned there. I don´t know of any dynamometer tests were done with the engine.

Thanks for the powercurves, btw! I haven´t seen a complete one for the Db-605A.

The speed datapoints are exclusively G1/G2 in clean fighter configuration. Statistically spoken, I get a one sigma probability (66.7%, IIRC) that the datapoints reflect two interrelated "sets" of datas rather than one clustered. It might well be related to the limited sample size or any of the factors mentioned by You but I would keep this in mind if further documentation produces datapoints, which fall in one of the two clusters rather than in between.
 

Pretty sure. The "TsaGI book" that floats around on the net indeed lists 1475 hp for some reason, but I have the original soviet paper from 1943 and 1944, and it gives in the tables 1310/SL and 1300/5,8km, for both G-2s and the G-4.

Also if you plot the Soviet climb results with the gunpodless G-2 against other curves known 100% for 1,3ata (Erla, Rechlin Kennblatt, Finn trials), the curves are almost perfect match. Checking climb curves is a good way because its very sensitive to power changes.

Thanks for the powercurves, btw!
Click to expand...

Your welcome!
 

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Hi Delcyros,

>The speed datapoints are exclusively G1/G2 in clean fighter configuration.

Would it be possible to provide a full list of the datapoint sources?

The reason I ask is that for a comparison, they would have to be normalized, which is only possible if we know the configuration of the aircraft in some detail.

For example, the Finnish G-2 data was not normalized for standard atmospheric conditions, and the engine of the test aircraft was running slightly too slowly due to an inaccurate tachometer.

Kurfürst has an interesting comparison on his website showing the influence of various configuration items, so it might be possible to get normalized and thus comparable data points even where the configuration of the test aircraft differed.

Regards,

Henning (HoHun)
 
Are these charts any good:
 

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Kurfürst said:
Pretty sure. The "TsaGI book" that floats around on the net indeed lists 1475 hp for some reason, but I have the original soviet paper from 1943 and 1944, and it gives in the tables 1310/SL and 1300/5,8km, for both G-2s and the G-4.
Click to expand...

When was the G-2 cleared for 1.42 ata? I have a pilot handbook giving 1.42 ata for Notleistung (5.7 km alt.) and it is dated June '42.
 
June 1942 Handbook? I don't think I have seen that yet, could you spare a copy?

As for 1.42ata, I believe it was cleared at least twice, once in November 1942, then probably recalled at around March 1943, and then in end of September 1943 again.

DB issued a directive for clearance in June 1943, but I believe that was not an official clearance from the RLM, but the testing was undergoing at the same time with new oil dearator, and they were waiting for the testing results, which were appearantly positive towards the end of September 1943.

See also: Kurfurst - Your resource on Messerschmitt Bf 109 performance
 
Here you go. Check page 14.

Also, check out this website, that's where I got it from. They have lots of stuff there, unfortunately the site's a bit awkward to navigate.
Luftwaffe Cockpits

The Bedienvorschrift specifically states that it is overridden by the later L.Dv.T 2109 G-2/Fl, so there that's where they could've limited the cleared boost.
 

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Basically yes, it is possible. I did these data compilations quickly basing on Mike Williams and Kurfürst´s sites. It will take some hours to tabulate the datas with additional source informations. Whish I had more hours to spend...



It´s not necessarely comparable in the soviet tests. They noted that the G2 cannot run at top speed for more than 1 to two minutes before the oil begins to boil. This cannot be representative for 30 minutes climb- and combat power. It could be argued that take off power was not applied in these tests for climbing trials due to the cooling limitations, which are more exagerated in climb than level speed conditions.
 
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