Bf109 test data

[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.

[*Buzzsaw*]

Originally Posted by Kurfürst

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.

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


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

The problem was there were no 109E1's or 109E-3's in production or service at the time V15 was constructed. V15 was clearly a prototype.

According to Uwe Feist in "The Fighting Me 109", published London: Arms and Armour Press, 1993, there were two prototypes built to test the 109 with the DB601: V14, which had two MG's in the nose, and two F/F 20mm in the wings and which was equipped with a DB-601Ao engine, and V15, which had only had the two nose MG's, (no weapons mounted in the wings at all) and which it appears, was equipped with the DB-601Aa engine.

According to Wiki, V14 was determined to be the more successful of the two prototypes, and there was an initial pre-production order of 20, designated E-0. Later, early production 109E's were sent to Spain to be tested with the Condor Legion. Production later commenced with the E-1 variant, with two MG's in the wings.

This information clearly points out the difference between V15 and the later production aircraft. This aircraft did not have the drag or weight of a pair of MG F/F's and their ammunition to contend with. And who knows what else was not present?

The question is, where is the test of V14?

[KG26_Alpha]

Originally Posted by *Buzzsaw*

The problem was there were no 109E1's or 109E-3's in production or service at the time V15 was constructed. V15 was clearly a prototype.

According to Uwe Feist in "The Fighting Me 109", published London: Arms and Armour Press, 1993, there were two prototypes built to test the 109 with the DB601: V14, which had two MG's in the nose, and two F/F 20mm in the wings and which was equipped with a DB-601Ao engine, and V15, which had only had the two nose MG's, (no weapons mounted in the wings at all) and which it appears, was equipped with the DB-601Aa engine.

According to Wiki, V14 was determined to be the more successful of the two prototypes, and there was an initial pre-production order of 20, designated E-0. Later, early production 109E's were sent to Spain to be tested with the Condor Legion. Production later commenced with the E-1 variant, with two MG's in the wings.

This information clearly points out the difference between V15 and the later production aircraft. This aircraft did not have the drag or weight of a pair of MG F/F's and their ammunition to contend with. And who knows what else was not present?

The question is, where is the test of V14?

I would take Luftwaffe data only as confirmed data, Wiki or old books are not always to be regarded as reliable to be honest.


"It clearly points out"................nothing




.

[Kurfürst]

Originally Posted by *Buzzsaw*

The problem was there were no 109E1's or 109E-3's in production or service at the time V15 was constructed. V15 was clearly a prototype.

Yes.

Originally Posted by *Buzzsaw*

According to Uwe Feist in "The Fighting Me 109", published London: Arms and Armour Press, 1993, there were two prototypes built to test the 109 with the DB601: V14, which had two MG's in the nose, and two F/F 20mm in the wings and which was equipped with a DB-601Ao engine, and V15, which had only had the two nose MG's, (no weapons mounted in the wings at all) and which it appears, was equipped with the DB-601Aa engine.

We are not discussing V14 (WNr 1029, first flew April 1937) V15 (WNr. 1773, first flew december 1937) but V15a (WNr. 1774). V15a had four MG 17s, as the report notes:

"An Bf 109 V 15 a, der Mustermachine für die E-1-Serie, wurden die Geschwindigkeitsleistungen erflogen. ... 2 Flügel- und 2 Hauben-MG eingebaut."

This information clearly points out the difference between V15 and the later production aircraft. This aircraft did not have the drag or weight of a pair of MG F/F's and their ammunition to contend with. And who knows what else was not present?

Again we are talking about V15a, not V15.

The question is, where is the test of V14?

Good question.

[*Buzzsaw*]

Originally Posted by 41Sqn_Banks

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.

Yes, but.... according to the RAF documents, except for takeoff, 3000 RPM and +12 boost should only be used over rated altitude, below rated altitude, 2850 rpm was recommended. However, this did not stop pilots from using 3000 rpm and +12 boost down lower.

The fact is, pilots will do things which are not necessarily in the manual, just because they are pilots.

[41Sqn_Banks]

Originally Posted by *Buzzsaw*

Yes, but.... according to the RAF documents, except for takeoff, 3000 RPM and +12 boost should only be used over rated altitude, below rated altitude, 2850 rpm was recommended. However, this did not stop pilots from using 3000 rpm and +12 boost down lower.

This is only a false interpretation propagated by Crumpp. The 2,850 rpm/3,000 rpm restriction is the 30 minute climb rating (+6.25 boost). In normal conditions this is restricted to 2,600 rpm, in combat/emergency condition however 2,850 rpm is permitted below FTH and 3,000 rpm above FTH.

Just think about it: It is not possible to achieve +12 boost above FTH, why put a restrict on a boost for an altitude where this boost is not possible?

But enough of Spitfire talk, this topic is about Bf 109.

[Robo.]

Just reading and summarising the information in this thread, ideally there would be both engines modelled:

DB 601Aa for E-3/B, E-4/B (and E-7 eventually)
DB 601A-1 for most of the other Emil variants, especially without bomb racks installed (E-1s, E-3s and E-4s in the sim)

It is known that due to overhauls and re-builds, there were all combinations possible and I am not taking the superchargers in account.

Only cca 3 out of 10 DB 601s made were Aa.

DB 601Aa = full throttle height of 4000m, rated at 1,35 ata (1,45 max)
DB 601A-1 = full throttle height of 4500m, rated at 1,3 ata (1,40 max)

Looking at the above, the only DB601 modelled in the sim has got the rated power of Aa and fth of A-1.

Originally Posted by Kurfürst

I. 1. The DB 601A-1 with the old type supercharger, 1.30 ata for five min and 990 PS, and 1.40 ata for 1 min and 1100 PS. Rated altitude being 4000m.

2. The DB 601A-1 with the new type supercharger, 1.30 ata for five min and 990 PS, and 1.40 ata for 1 min and 1100 PS. Rated altitude being 4500m.

Any documents at the different FTH of the two above supercharger types? Different supercharger (improved or new design) usually shifts the power curve of an engine, e.g. gaining in low level performance for the cost of lower fth. Alter und Neuer Lader do reflect this change in the Baubeschreibung page posted by Buszsaw.

Originally Posted by Kurfürst

3. The DB 601Aa with the old type supercharger, 1.35 ata for five min and 1045 PS, and 1.45 ata for 1 min and 1175 PS. Rated altitude being 3700m (altitude output was otherwise very much like the DB 601A-1 / old s/c, though it is an open question wheter the new s/c was fitted to the Aa as well. So far no evidence to that though.)
This is the type we have in the sim.

We do have these rated power but we also have the FTH of 4,5 km. See above. It is my understanding that the neuer und alter Lader reflects the A-1 or Aa subtype in the relevant documents because these were only referred to only generally as DB 601A without specifying the subvariant. Aa was indeed intended for export, but ended up being used by the Luftwaffe in considerable quantities (cca 25%) and on pretty much random basis.

[*Buzzsaw*]

Originally Posted by Robo.

Just reading and summarising the information in this thread, ideally there would be both engines modelled:

DB 601Aa for E-3/B, E-4/B (and E-7 eventually)
DB 601A-1 for most of the other Emil variants, especially without bomb racks installed (E-1s, E-3s and E-4s in the sim)

It is known that due to overhauls and re-builds, there were all combinations possible and I am not taking the superchargers in account.

Only cca 3 out of 10 DB 601s made were Aa.

DB 601Aa = full throttle height of 4000m, rated at 1,35 ata (1,45 max)
DB 601A-1 = full throttle height of 4500m, rated at 1,3 ata (1,40 max)

Looking at the above, the only DB601 modelled in the sim has got the rated power of Aa and fth of A-1.



Any documents at the different FTH of the two above supercharger types? Different supercharger (improved or new design) usually shifts the power curve of an engine, e.g. gaining in low level performance for the cost of lower fth. Alter und Neuer Lader do reflect this change in the Baubeschreibung page posted by Buszsaw.



We do have these rated power but we also have the FTH of 4,5 km. See above. It is my understanding that the neuer und alter Lader reflects the A-1 or Aa subtype in the relevant documents because these were only referred to only generally as DB 601A without specifying the subvariant. Aa was indeed intended for export, but ended up being used by the Luftwaffe in considerable quantities (cca 25%) and on pretty much random basis.

The below document, dated October 1940 by the WWII Aircraft Performance site is from the manual I have already posted,

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

...and indicates the DB601A and B had both variants of superchargers installed, both the 'Neuer' and 'Alter' lader, but the limit for both was 1.40 for takeoff and 1.30 for 5 minutes.



By the way, can anyone shed any light on the methodology to convert the German method of measuring boost, ie. 'ATA' to 'Ft/pounds', or 'Inches of Mercury'.