Bf109 test data

[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.

[Kurfürst]

Originally Posted by 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.

V15 or V15a? In any case, the V15a tests note a "DB 601A", but they give the rating as 1,35ata (which is the Aa rating). Power ratings also match that of the Aa.

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.

These figures appear to come directly from the Bf 109E operating manual and were clearly for 601Aa. See: http://109lair.hobbyvista.com/techre...als/bf109e.pdf

Originally Posted by klem

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?

The answer to both questions is that V15a fully confirmed to serial production aircraft, as the test report clearly notes.

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

Also note the results achieved in the Swiss tests fully agree with the results achieved with V15a FS/H0henlader supercharger gear testing results. This cannot be a coincidence IMHO.

Like I said, if the two aircraft two speeds is virtually identical at altitude with the same rating, it means that power and drag is virtually the same too.

Drag doesn't change with altitdue, so any meaningful drag or aiframe conditions between E-1 V15a and the Swiss E-3 J-347 can be ruled out.

Propellers are the same.

The only thing that can be different between the two is POWER. V15a has obviously a lot more power at low levels. Now this might raise the question wheter V15a has some kind of ultra-brutal low altitude engine with much more power than the serial production aircraft, but this can be ruled out too, since [b]V 15a's engine was bench tested/b], and it has exactly the amount of power at low levels as a DB 601Aa should have.

So the J-347 has LESS horsepower at low levels.

And it matches V15a's high-gear / Hohenlander / FS gear speed curves almost perfectly.

I mean, HELLOOOOOO? It runs in high supercharger gear only.. That's perfectly suitable if one want to compare the factory VDM props performance under identical conditions to two other type of props (which is what the Swiss were doing).

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.

In other words: under similar testing conditions, boosts and correcting (ie. not fully corrected), both the pre production WNr. 1791 and 1792 fully support the WNr. 1774 (V15a) figures.

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.

The December 1939 manual gives 1.3ata max ratings, so it's clearly for the 601A-1 version (early Lader).

Comparison the Manual's climb rates and speeds (at unknown rating) show practically identical match as the RAE trials which OTOH are known to have been performed at 1.23 ata 30-min rating, so in all likelyhood the manual also shows 30-min rating.

462 kph at the 30-min rating at SL is fairly believable for the 109E / 601A1.

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

Note the French aircraft is again a practically exact match with the V15a figures at low levels (as measured at 1.31ata, the French one was running at 1.3ata).

The French aircraft was not developing full boost over altitude for unknown reason (French oils used in tests are suspect) but only about ca. 1.2 ata. In other words, they achieved about 550 kph with 1.2ata.

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

US tests did not measure the captured '109E' speed anywhere near ground level..

Lowest measured value was 336 mph at 12k feet (541 kph at 3657 m) using the low altitude supercharger. In comparison V15a achieved 532 kph at (uncorrected) 1.33ata, and 545 kph at (corrected) 1.35ata.

As a matter of fact at known measurement altitudes the US trial matches even exceeds the V15a data..

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.

I Agree.

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

It was introduced early and in large 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.

As demonstrated above, this opinion is decidedly incorrect.

The V15a results match other results exactly, IF THE SAME CONDITIONS AND CORRECTIONS ARE APPLIED. Problem is, most of the other tests being waved about are either uncorrected, simplistic or are for different conditions (different engine, different boost).

Also the V15a's loadout is as detailed if not more so than any other 109E tests (definietely more so than the completely unknown conditions of the Swiss test, for example).

One can't compare apples and oranges.

Unfortunatley the only set of DB601Aa figures seems to be the Swiss tests.

This is incorrect because both V15a trials and the Baubeschreibung Leistungsblatter also detail DB 601Aa performance.

The most likely reason 1c decided to model the DB 601Aa variant is that this is what was best documented (both in manuals and for performance tests).



Well the question is basically this:

Should we correct FM to match the airplane modelled, or match the airplane to the FM modelled?

Should we compare our exiting FM's accuracy with tests using different and lower powered variants of engines we have modelled or not?

Should we use official / guaranteed performance specs for all aircraft (which is the V15a figures) or just pick the worst ones for each plane we can find from the bottom of the tolerance limits?

Should we model aircraft after essentially undocumented speed curves, in which the actual flight conditions are completely unknown or based on tests which are well documented and all airframe conditions, engine outputs are documented, known and also - can be replicated in the sim?

Should we apply the above decision to all aircraft, or just apply it to some aircraft, as it fits our taste?


BTW ain't the Spitfire's FM based on the Spitfire prototype? No problem with this one, eh?

[41Sqn_Banks]

Originally Posted by Kurfürst

BTW ain't the Spitfire's FM based on the Spitfire prototype? No problem with this one, eh?

Nope. The speed charts posted by BlackSix are based on the performance test of N3171 (http://www.spitfireperformance.com/n3171.html). Interesting notes on engine power of this aircraft:

The results show that the maximum level speed is reached with the airscrew controlling at 2800 engine r.p.m. On increasing the r.p.m. to 3000 the speed was reduced, on the average by 4 m.p.h.

For the particular engine fitted there is a reduction of 17 b.h.p. at constant boost (+6¼ lb) when the r.p.m. are increased from 2800 to 3000. The loss of speed is therefore probably due to the loss of power accompanied by a slight decrease in airscrew efficiency. The matter is being further investigated by Messrs.Rolls-Royce and Messrs.Rotols. It will be noted that reducing the R.P.M. from 3000 to 2800 lowers the full throttle height by 2000 feet.

4.3 Engine Power. The engine installed in the aeroplane develops slightly less power under test bed conditions than that in K.9793, the aeroplane fitted with the 2-pitch airscrew. This could have the effect of reducing the top level speed by about 2 m.p.h.

...


2. There is a drop of 13 m.p.h in maximum level speed compared with the 2-pitch airscrew aeroplane but of this, 8 m.p.h. can be attributed to sources other than the airscrew.

3. Below full throttle height an increase in speed of about 4 m.p.h. can be attained by controlling the engine R.P.M. at 2800 instead of 3000.

[Kurfürst]

Well the figures people have been asking for the Spitfire, 285-290 mph or so at SL, are strikingly similar to those achieved with the Spitfire prototype. Which if I got the spiriti of the thread right, means that our Spitfire should realistically do about 250-260 mph tops. It's a PROTOTYPE and all that you know...

I am also asking that because N3171 trials did not measure speed near SL (or under 8000 feet) at all.

So on what are complaints about the lack of SL speed of the Spitfire as based again? A trial that did not even measure SL speeds or that infamous crayon curve?

I am very cynical here of course, but in that context, it's a somewhat difficult to understand the extremely demanding attitude displayed by some for the 109E performance on the other hand.

I mean if a crayon drawing will do for the +12 Spitfire surely four seperate timed runs on a record course with calibrated and recorded instruments, a bench tested engine, with the results being corrected for Normaltag and the nominal engine output and guaranteed by manufacturer will do for a 109, would it not.