Bf109 test data

[*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'.

[*Buzzsaw*]

Salute

And one more.

The following document is only really relevant to the 109E-1, although it does show the E-3 weights, which by the way indicate that game aircraft is underweight.

The primary use of it is that it shows production E-1 speeds at 1.15 ata boost, ie. continuous cruising speeds. Measurements could be taken at this boost level to determine if the aircraft meets these specifications.

[Kurfürst]

Originally Posted by *Buzzsaw*

The primary use of it is that it shows production E-1 speeds at 1.15 ata boost, ie. continuous cruising speeds.

I guess you misunderstood something.

Motorunterzetzung DB 601 A = 1:1.55
Reduction gear ratio DB 601 A = 1:1.55

1 ata = 1 kg / square centimeter. I am not going to convert this to PSI (0.454 kg = 1 lbs, 2.54 cm = 1 inch, have fun ) but keep in mind the British used relative boosts, ie. (+) 0 PSI = 1 ata, and + 6.25 PSI boost on the Merlin III is 1 ata plus whatever 6.25 PSI is in ata.

Bottomline, the Merlins always used much higher boost than DBs to compensate for smaller displacement. IIRC the 1.7 ata boost of the methanol boosted 605AM was something like +7 PSI..

[Robo.]

Originally Posted by *Buzzsaw*

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.

Yes I am familiar with that document but as usually, it does not specify the subversion of DB 601A (e.g. A-1 or Aa) and is rather generic (includes all A dn Bs, difference being the gear ratio). It actually mentions the details about the new supercharger, like 1mm Drahtstaerke) and different FTH at Hoehenlader as result. My understanding until now was that the new s/c column is for the A-1 and old s/c is for the Aa, hence the FTH difference. I see there is more to it so I am interested in details - how many engines have had the old s/c fitted and what was the technical difference and so on.

I simply don't know so I did not consider the various supercharger combinations at all in my original post.

It is obvious though that in case we have the Aa modelled, the FTH is wrong.

Originally Posted by *Buzzsaw*

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'.

1 ata = 1kg/cm^2 = 14.2 lbs/in^2 = 28.96 inHg

[Kurfürst]

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.

Probably that would be the best historical approach, though since there was a lot of E-7/N (in fact most the post-bob production which will make appearance in BoM) I would say that 601N would be a more practical choice.

Problem is, we are end of the development line, and 1c certainly not going to give us 3 seperate variants. The only diffo between the A and Aa is probably that the latter is maybe about 10-15 km/h faster down low.

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.

Depends. Engines have higher FTH in high speed flight. An Aa should get about 3700m in climb and 4800 m in full speed flight (the latter being a bit problematic with the current poor altitude model)

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.

Yes I do have these old/new 601A curves but I believe both are uploaded to aircraftperfomance.org recently.

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.

Yes more or less that's my understanding too. Of course the Aa has curves too, but these are Mercedes's own manual.

[Robo.]

Thank you very much for the info about the superchargers, superb!

Originally Posted by Kurfürst

Depends. Engines have higher FTH in high speed flight. An Aa should get about 3700m in climb and 4800 m in full speed flight (the latter being a bit problematic with the current poor altitude model)

I am aware of RAM effect, but the current FTH in the sim (for all Emils) is 4,5km in the climb. (I would need to re-check that in the current beta patch.)

[Kurfürst]

Originally Posted by Robo.

Thank you very much for the info about the superchargers, superb!

You are welcome.

I am aware of RAM effect, but the current FTH in the sim (for all Emils) is 4,5km in the climb. (I would need to re-check that in the current beta patch.)

Oh, something is fuzzy then... indeed it looks like the neue Lader, I wonder if someone has the most recent engine file data, I remember seeing them on the forum some time ago.

[*Buzzsaw*]

Salute

There is also this document, dated 24/7/1942 according to Mike Williams site where it is located.



It indicates a much more conservative speed than some of the previous documents.

I am also very interested in any German speakers interpretations of the following three documents, dated August of 1940, also found on the WWII Aircraft Performance site: