Official Fulqrum Publishing forum

Page 5 of 9

« First

Last »

Show 100 post(s) from this thread on one page

Official Fulqrum Publishing forum (http://forum.fulqrumpublishing.com/index.php)

- IL-2 Sturmovik: Cliffs of Dover (http://forum.fulqrumpublishing.com/forumdisplay.php?f=189)

- - Bf109 test data (http://forum.fulqrumpublishing.com/showthread.php?t=34816)

41Sqn_Banks

10-10-2012 06:51 PM

Quote:

Originally Posted by *Buzzsaw* (Post 468241)

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.

10-10-2012 07:37 PM

Quote:

Originally Posted by Kurfürst (Post 467953)

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.

Quote:

Originally Posted by Kurfürst (Post 467953)

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*

10-10-2012 08:09 PM

Salute

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

http://www.wwiiaircraftperformance.o...zeug-daten.jpg

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:

http://www.wwiiaircraftperformance.o...endezeiten.jpg

http://www.wwiiaircraftperformance.o...rvenradien.jpg

http://www.wwiiaircraftperformance.o...rvenzeiten.jpg

*Buzzsaw*

10-10-2012 08:23 PM

Quote:

Originally Posted by Robo. (Post 468269)

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.

http://www.wwiiaircraftperformance.o...manual-p21.jpg

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*

10-10-2012 08:36 PM

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.

http://www.wwiiaircraftperformance.o...datenblatt.jpg

Robo.

10-10-2012 08:38 PM

Quote:

Originally Posted by *Buzzsaw* (Post 468289)

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.

Quote:

Originally Posted by *Buzzsaw* (Post 468289)

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

10-10-2012 08:51 PM

Quote:

Originally Posted by *Buzzsaw* (Post 468295)

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 :D ) 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..

Kurfürst

10-10-2012 08:59 PM

1 Attachment(s)

Quote:

Originally Posted by Robo. (Post 468269)

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.

Quote:

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)

Quote:

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

Quote:

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

Robo.

10-10-2012 09:03 PM

Quote:

Originally Posted by Kurfürst (Post 468304)

I guess you misunderstood something.

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

I believe he refers to the second (bottom) part of that document titled Reichweiten where we see the speeds at 1,15 ata Dauerleistung at 1, 3, 5 and 6km altitude (only 0,92 ata achievable at 6km) so I guess he was right in his assumption.

*Buzzsaw*

10-10-2012 09:08 PM

Quote:

Originally Posted by Kurfürst (Post 468304)

I guess you misunderstood something.

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

Salute

You are suggesting this is a test of a different reduction gear?

Because in fact the speeds shown are achieved at a boost of 1.15 ata.

All times are GMT. The time now is 04:11 PM.

Page 5 of 9

« First

Last »

Show 100 post(s) from this thread on one page