Bf109 test data

[*Buzzsaw*]

Originally Posted by klem

OK, thanks. I'll keep the V15a, Swiss and Handbook curves only and plot the CoD 109E-3 against them.

Then you are ignoring the other relevant material in favour only of what Kurfurst is advocating. Who has a point of view. Which may or may not be accurate...

That is not to say that I don't think the 109E-3/E-4 as currently constituted are too slow in CoD, (although proportionately MUCH better modelled than the Spitfire and Hurricane), they are likely too slow, however...

One, you should be aware the designation 'V15', indicates a pre-production, test aircraft, which may or may not include the standard loadout or equipment of the production version, this is not an E-3 or E4 or even an E-1, and this cannot be considered a test of a standard factory variant, it was done in 1938, before the E-3 was in production and before the tests done of the standard variants.

For example, a later 1939 test of an actual German production 109E3 to determine the loss of speed as a result of the fitting of wing guns shows a top speed at sea level of 467 km/hr, less than shown with the V15 variant. The E-3 test was done at 1.3 ata, not full 1.4 boost, so the speed would be higher at a higher boost, with the additional 100 PS that would give, but it is hard not to accept the document is more relevant than the V15 document. Tests of the existing game 109E3 should see a speed of 467 km/hr at 1.3 ata, something which I believe it fails to achieve.



Two, in reference to another example, the Swiss tests, indications are the DB601Aa engine was an export only variant. And many facts bear this out. For example, none of the aircraft captured during the BoB had the Aa version of the DB-601 engine.

And the German manual for the DB601A or B, which includes many of the charts seen on the WWII site and Kurfurst's site, and which is dated on issuance October of 1940, with extensions, has no reference to the DB601Aa. It can be downloaded here:

http://www.scribd.com/doc/32387854/Handbuch-DB-601-A-B

The DB601A/B engine was listed at 1100 PS at sea level, but that actually wasn't it's highest output point, that was at approximately 1.7 thousand meters, when it outputted approx. 1170 PS.

A translated captured German document which agrees with the suggestion no DB601Aa were used in the Luftwaffe aircraft is a bulletin the Germans themselves issued in November of 1940 allowing engine rpm to be increased over a certain altitude, and the only engines mentioned were the DB-601A or B and N.



In any case, dismissing the results of the British and French tests as irrelevant is not necessarily the correct choice as there is very detailed information provided there which can shed light on the 109E's performance. And for example, the British Rolls Royce tests tend to agree with the test of the E-3 I have shown above.

Messers Rolls Royce did their speed and climb tests of a captured 109E-3 at 1.23 ata, the 30 minute limit boost level, and achieved a speed of 285 mph/456 km/hr at sea level at that boost. Obviously top speed at 1.3 and 1.4 ata would be higher, but you can see a linkage with the German E-3 test at sea level.



So as I posted before, careful consideration of ALL the facts is important when coming to a conclusion re. performance.

[csThor]

Buzzsaw - You're mixing something here. The export thingy was the Bf 109 E-3a (in which the a denotes the export use). The Romanians received the same type as did the Japanese (the latter for tests). I have the full Bf 109 E manual compendium from Luftfahrtarchiv Hafner (reproduced originals) and the DB 601Aa is listed as engine type.

BTW you accuse Kurfürst of " a viewpoint". If I were you I'd be very quiet since you obviously represent the other side of that particular medal.

[Robo.]

Originally Posted by csThor

Buzzsaw - You're mixing something here. The export thingy was the Bf 109 E-3a (in which the a denotes the export use). The Romanians received the same type as did the Japanese (the latter for tests). I have the full Bf 109 E manual compendium from Luftfahrtarchiv Hafner (reproduced originals) and the DB 601Aa is listed as engine type.

BTW you accuse Kurfürst of " a viewpoint". If I were you I'd be very quiet since you obviously represent the other side of that particular medal.

The 'a' is not necessarily for export, there seems to be lots of confusion regarding that.

Buzzsaw is certainly making a good point. The FTH of all 109s in game is 4500m, suggesting that DB 601A-1 version is modelled.

467 kph at S/L at 1.3 ata seem very reasonable (water cooler 3/4 closed). The test were not recalculated for engine's guaranteed power yet.

[41Sqn_Banks]

Originally Posted by *Buzzsaw*

The E-3 test was done at 1.3 ata, not full 1.4 boost, so the speed would be higher at a higher boost, with the additional 100 PS that would give, ...

Obviously top speed at 1.3 and 1.4 ata would be higher, ...

According to the DB601A manual 1.4 boost was for take-off only ("am Boden bei Abflug"). The highest boost mentioned for flying at ground level ("in Bodennähe") is 1.3 boost.



There is nothing preventing the pilot from using this boost during combat at ground level. However there is no evidence at all that this boost was authorized or even used against regulations (e.g. pilot anecdote) for any other condition than take-off. Of course power and speed can be higher if the engine is mistreated, but this incorrect handling should not be considered during performance dicussions and should actually be penalized by the game.

[klem]

OK Guys, thanks.

We don't seem to have a problem with the historical performance curves, only the particular engine in use.

My memory, as ever, being a little unreliable I had forgtten a book I have tucked away called Bf109 by William Green. I found it last night and he talks about the V series including V15 which had the DB601A engine and in the same sentence says "this was the engine variant used by virtually all Me109s for the first 18 months of the war." But I guess that will only fan the flames.

None of which solves the argument unless someone has production/installation figures for the A and Aa which might lead us to a decision. Even that would no doubt be contentious as I imagine there could be a case for both engines.

SO, I am going to separate the issues. I'll test at 1.3ata AND 1.35ata with 2400rpm and 1/4 radiator and put back ALL of the curves I had in the beginning. This will:
1. Tell us what CoD 109E-3 is doing (my main aim)
2. Let everyone else return separately to the bun-fight over what we should be getting.
3. Raise the question "what do 1CMG think they are giving us".

And 3. is the real point for those that disagree. That's where the A and Aa camps should be directing their energies.

[Kurfürst]

From TOCH. Very interesting posts there btw, I won't post all, but you can follow the link.

http://forum.12oclockhigh.net/showth...6932#post26932

Originally Posted by olefebvre

I never said the Aa was exactly the same as the A-1.

The export customers indeed get the Aa engine but the Russians got a/c with A-1 engines. The Aa documents leaves no doubt it was designed for export since there are absolutly no references to RLM standards within those documents (fuel, oil, doc ref, etc...).

The Aa was based on the A-0 just like the A-1, and used the old kind of supercharger as used on the A-0 but souped up for low alt business. It seems the increased take off rating was of interest for the Luftwaffe afterall since about 25-33% of the produced A/B series engines were of the Aa/Ba kind. Which means that the luft used them as well along with the A-1. Both subtypes being produced over the same period of time.

While there is absolutly no Aa document that i could find with a RLM reference, but i believe it was used most probably on the E-4/B and E-7 variants for which the increased output at take off was most needed.

So far every engine recovered on E-4/B or E-7 crash site seems to have been of the Aa type.

Cheers,
Olivier

[klem]

OK, my bad. I forgot I had abook called Bf109 by William Green. In it he covers he entire development of the 109 and of V15 he says it was fitted wwith the DB601A and goes on to say that "this was the engine that powered virtually every Bf109 for the first eighteen months of the war". Yes, I know that's contentious.

More memory problems, I forgot the 1C Manual for CoD which gives us the following max figures:

Take-off
Initial climb at 250 km/h.
Raise gear.
Raise landing flaps and adjust trim accordingly.
Max 2,468 rpm / 1.45 ATA

Climb
Max continuous 2,368 rpm / 1.35 ATA.
Oil temperature: 30 to 75 C, up to 95 in short bursts.
Water temperature: 80 C, up to 105 in short bursts.

Cruise
Max 2,326 rpm / 1.20 ATA.

The DB601A max figures for these are 1.4, 1.3 and 1.15 so it seems 1C have given us the DB601Aa (whether everyone likes it or not).

However 1C also give us 460kph at SL and 560kph at 5,000m.

Looking at the available figures again.....

V15 with the DB601A gave 485kph at SL on 1.31ata corrected to 498 for guaranteed engine performance and 561/4900m on 1.33ata corrected to 572/4800m. But did this represent a standard military loaded aircraft in 1938? It compares very favourable with J-347s DB601Aa 'true' performance a full 20 months later. Is this likely?

Me109E-3 J-347 ("The Swiss Tests") with DB601Aa gave 464kph at SL and 565kph at 5000m.

E-1 1791 and E-3 1792 both with DB601A gave 475-476 at SL on 1.3ata (max 5 mins) and "These speeds are on normal temperature and right boost pressure regulator setting, nevertheless, not on guarantee achievement of the engine". This begs the question on two separate aircraft "why not?" and leaves the door open to speculation that the guaranteed engine figures were not being achieved. Although without corrections the SL figures aren't that far below V15 (uncorrected for guaranteed performance and therefore in the same circumstances as 1791/1792) and which used fractionally higher boost.

The Bf109E-? curves for 16th December 1939 give 462 at SL and 562 at 4500m, presumably at the max 5 min contiuous rating... but for the 601A or 601Aa?? I am assuming the 601A because of the date and the fact that it is from the handbook.

Bf109E-3 French tests (DB601A) gives us about 475-480kph at SL and 550kph at 5000m.

Bf109E-3 US tests (engine unknown) give us 467kph at SL and 543klph at 5000m.

I realise I am going around the same circles as several other people and I am forced to the conclusion that 1C MG are modelling the Bf109E-3 on the DB601Aa and the Swiss Tests. The boost figures 1C give us are for the DB601Aa which the Swiss a/c had and the speed chart 1C give us for CoD closely resembles the Swiss results.

Whether they should be doing that is open to question. I have no idea when the DB601Aa was introduced and in what numbers.

I'm also inclined to disregard the V15 figures because everything else is against them including their date, the fact that it was a dev a/c (although at pre-production status) and full details of the aircraft loadout. Unfortunatley the only set of DB601Aa figures seems to be the Swiss tests.

Anyway, I'll do the 1.3ata and 1.35 ata tests and show them with the various data above. It will at least tell us if 1C are achieving what they say in their manual and I'll leave to to you guys to fight over which variant(s) should be in the game.

[camber]

Hi Klem, as you have seen there is no getting around the bunfight of choosing which tests to regard! I agree that as we have the DB601Aa in CloD, we may as well use the Swiss tests, which are pretty consistent with the rest of the flight test data anyway. I expect that Kurfust might present his opinion that the SL performance in this test is low because the supercharger was locked into high altitude gear. Myself I believe this is unlikely, and there is no documentation supporting such usage (just the possibility it could occur).

Originally Posted by 41Sqn_Banks

There is nothig preventing the pilot from using this boost during combat at ground level. However there is no evidence at all that this boost was authorized or even used against regulations (e.g. pilot anecdote) for any other condition than take-off. Of course power and speed can be higher if the engine is mistreated, but this incorrect handling should not be considered during performance dicussions and should actually be penalized by the game.

This is quite interesting...from Steinhilper, we know that 109 pilots tried revving their DB601 over limits to gain extra boost around FTH, which was only approved subsequently. If the 1.4 or 1.45ata clockwork boost worked at any altitude, surely it would have been used. It is intriguing that no anecdotes or reports exist!

camber

[Robo.]

Originally Posted by camber

I agree that as we have the DB601Aa in CloD

I would say that what we have in ClOD is a mix of A-1 and Aa qualities, e.g. fth od this 601 is 4,5 km, yet the mfp at SL is 1.45 ata (with Erhoehte Notleistung).

The weird and unlimited 'afterburner' usage is also pretty much fictional and so is the drop of ata unless you drop the pitch under 2200 U/min.

I have seen the actual FM files somewher on this forum and iirc it said A-1 so I assume that is what 1c tried to model.

[Kwiatek]

My test showed that E-3/E-4 in CLoD reached at sea level:

- 1.35 Ata 2400 RPMs - 450 kph
- 1.45 Ata 2400 RPMs - 460 kph ( 1 minutes emergency boost)


If i put my money on 109 E speeds i think most reliable data for serial planes would be:

109 E with Db601 E

- at sea level, 1/4 radiator open, 1.3 Ata 2400 RPMs - 467- 475 kph ( depend of version and windscreen type - standart E-4 new windsreen was more draggy so it should cost a few kphs)

109 E with Db601 Aa

- at sea level , 1/4 radiator open, 1.35 Ata 2400 RPMs - 475-485 kph.

Emergency power 1.4-1.45 Ata should add some few kph at sea level - i think someone could calculate it but it wont be probably higher then another 10-20 kph.