JtD

We still don't know which units were switching to 1.98 ata, because all we have is a secondary source stating a plan, we have no primary source, no order and no confirmation. We also don't have a primary source clearing 1.98 ata for service use, outside of field testing, and no confirmation that it actually was used, outside of field testing. We have some indicative arguments but they lack in number and quality to make it conclusive evidence. In dubio pro reo, which at this point means every one can pretty much be entitled to have is own opinion. And just so you know, the manuals very strictly recommend to use C3 fuel with MW50, even at lower boost settings. Permitting use of B4 "in case of emergency". Obviously, losing the war kind of qualifies as a permanent case of emergency, but just because a 109 has a C3 triangle on the fuselage and/or C3 available at the base, it doesn't necessarily mean highest boost levels.

Secondary source again. :( A snippet of it. And I thought there was a well researched article based on 60 primary sources, most of them presented in the article, on the issue.

OK, and the source?

Maybe you know, I don't. Can you please point me to the source(s)?

Well, please provide the links to these argumentations. I for one have never seen pilot statements confirming the use of 1.98 ata or Gruppe logs that confirm the engine modifications. All I know are well documented plans, some technical feasibility studies and field studies with mixed outcomes, plus some poor quality (i.e. mostly secondary) sources indicating the outcome was positive because there were further plans. I've never seen any confirmation - but I've seen other 1945 plans about hundreds of submarines and thousands of aircraft to be produced. I don't care. I also don't care if it was Jimmy who stole Jonny's gummy bear. I've outgrown kindergarten for a long time. I care about facts. So - do you care to share facts or is this such a personal issue that only Mike, Neil, Milo and Friedrich may know?

Look Kurfürst, if you want to make a case for anything, try an approach like this. There's a list with more than 60 primary sources on the bottom which support the authors point of view - plans, technical feasibility, factory tests, field tests, service introduction, service use. All there, documented. Do the same. But please spare me and the world your tiresome kindergarten style forum debates, where you show no intention at all to actually share information. And while you seem to be desperately trying to prove your intellectual superiority with smart ass comments and cheap shots at absent people, you are in fact achieving the opposite. One liners followed by :megalol::doh::lol: are pathetic. You're destroying any reputation you might have built with your other contributions, be it your website or other, good quality forum posts.

Snippets from secondary sources are not "data", in particular when they boil down to "it seemed that they solved the problem because they had big plans with that thing". Even if we accept the secondary sources all they show is that by the end of March 1.98 ata weren't in use but there were plans to use it with several squadrons. Alongside with all the Ta 152's and the jets that never got into service. Anyway, feel free to make your own website with whatever content you think is worth publishing. There's nothing keeping you from it, just like Mike and Neil started from nothing, you'll just have to do it. And if your site ends up only half as good as theirs, lots of people will be happy having another excellent source on the web.

Kurfürst has some data on his page, maybe he's got more in other places / his library. http://kurfurst.org/Engine/DB60x/DB605_datasheets_ASM.html

I don't care about the extras, but would like to be given the chance to participate in the skype meetings.

The temperature of the supercharged air increased up to 5-6 km, depending on rpm, where the supercharger reached maximum rpm with the coupling fully filled with oil. Above that, air temperature dropped down again. As an example, the curve in the DB605A manual for 2600 rpm gives 70°C at sea level, 58°C at 2100m, rising to 98°C at about 5.5 km and down to 70°C at 11km, because outside air gets cooler and compression remains constant above full throttle altitude. As to why they handled the low altitude supercharging the way they did, I can also just guess. I suppose they wanted to have higher boost at lower rpm, too, for instance when taking off with manual 12o'clock pitch, where the engine would start with low rpm and only catch up during the take off run, not supposed to exceed the rpm limit until after gear up. The way it is, 2300rpm will already give you the ~1.42 at sea level, certainly good to have, might be what DB had their eyes on.

Simply put, it is the full throttle altitude of the first charger gear. As you say, below that altitude there is a constant volume of oil pumped into the supercharger coupling, which costs power, more in the denser air down low, just as if it was a fixed coupling as on any other aircraft engine at the time. It's wasted power to excessively compress and then throttle air (sea level) instead of compressing it to the required level, without any throttle (2.1 km). Also supercharged air temperature drops up to the 2.1 km mark (DB605A), resulting in more power there then at sea level.

When pressure between the two throttles drops below 1.30 ata. This depends on a few things, like engine rpm and speed, but taking the chart in post #16 as an example - Kampfleistung at 2600 rpm in level flight - it happens at 6100 m.

I was talking about high altitude, where the blower no longer is physically able to provide the boost. As a sidenote, the blower does not provide constant ata over altitude, as can for instance be seen in the chart Kurfürst provided in post #16. The 1.30 ata setting delivered up to about 1.8 ata, in which case the Reglerklappe cuts off anything above 1.30 ata. At sea level, 1.30 ata are still being exceeded even at the 2100 rpm setting and the Reglerklappe need to regulate.

Yes, at high altitude on manual, on the bottom line you'll be able to reduce resistance in the manifold a little bit and it will have a small, positive impact on endurance / range. I doubt it will even be a two digit percentage. Under the same conditions you'll get more performance by increasing rpm along with boost and for that can leave everything on automatic.

The Reglerklappe is not the problem, it is fully open at high altitude without any overrides. But if you reduce boost to below 1.30 ata (DB605A), the Leistungsklappe is not fully open and will not be adjusted. If you set the engine to 1.15 ata, it will reduce boost from 1.30 to 1.15 or ~proportionally at higher altitude.

At settings below Kampfleistung you could disable automatic prop pitch, and maintain rpm while increasing boost by moving the power lever forward. This is just like any other aircraft. However, many other aircraft had the throttle gradually open up fully at high altitude, so there'd be the optimum full throttle altitude also at lower boost settings. The DB did not, so at high altitude, at low power settings, disabling automatic pitch could give you higher boost at the same rpm. On the other hand, if you needed more power at high altitude, you could leave automatic pitch and increase rpm along with boost for an overall much bigger effect - on the bottom line, manual pitch would only allow you to fly maximum boost at reduced rpm.

Yo-Yo, I think it is pretty clear what happens for Notleistung und Kampfleistung (Regelklappe regulating to 1.42 ata or 1.30 ata (DB605A), Leistungsklappe fully open). I'm still not sure what happens at lower power settings, it still seems to me that the dual throttle will not maintain constant boost over altitude (Regelklappe fully open for the most part, leaving through whatever the supercharger can deliver (at cruise settings less than 1.30 ata at most altitudes for the DB605A), Leistungsklappe at constant opening). Boost at cruise settings not being constant over altitude is new to me, and doesn't really agree with the popular engine charts. These might of course be simplified, but still it seems odd. I'd appreciate if you could share your findings, understanding and conclusions on the subject, if you can spare the time.

Which Fw 190D, Spitfire, P-47 and P-51 subtype? Can I assume whichever variant I consider best?

YoYo, do you have the DB 605 Einbaumappe available from Luftfahrtarchiv Hafner? It contains a few charts that may be helpful - for instance a chart with several boost over altitude curves for various rpm. It states the figure I quoted above. Edit: There's also useful info regarding the relation between throttle opening and power control lever position in the DB 605 Anleitung fuer Kontrolle, page 168, available there. It can for instance be seen there, that the throttle can be considered fully open with Kampfleistung already. Activating Notleistung will only increase rpm and setting for the boost control. If you need help translating, please let me know.

What I don't understand about the whole thing, sorry YoYo for hijacking a bit here, is that the pressure between the two throttles was for the most part controlled by a single aneroid, the only exception being the manual input for the Notleistung override. Now both the documentation and my technical understanding say that this system limited the boost to a single fixed value (of 1.3 ata), provided the supercharger managed this. Now this works OK for as long as the pilot chose combat power, but at lower power settings with lower rpm the supercharger only manages to deliver 1.3 ata at low altitudes, for instance at 2300 rpm only up to ~1300m. If the automatic regulation now always limits to 1.3 ata, this means the first throttle is fully open and the second throttle is closed a little, which it is since it is controlled directly by the pilot. But this would only results in the 1.15 ata going with the 2300 rpm at altitudes below 1300m, and will be slightly less, and varying, at altitudes above 1300m. However, the engine chart gives a full throttle altitude of 5500m for 2300 rpm and 1.15 ata, which is exactly what the supercharger can manage - at the exit of the supercharger according to DB documentation, not behind two throttles. Which in turn means that both throttles need to be fully open, at least not restricting anything, in order to deliver the full full throttle altitude. But then I also don't see anything to automatically adjust the pilot linkage, which leaves me in a bit of a dilemma since they way I understand the system - automatic only regulation on the first throttle for 1.3 ata and manual only regulation on the second throttle doesn't result in a constant 1.15 ata up to 5500m, as indicated by the DB documentation. For the record - a throttle does reduce pressure. It always does, there's no "sufficiently large" or something. So that's not the explanation. One question I could not answer myself - where does the boost gauge in the cockpit get the boost information from? Would it be possible DB fed the supercharger pressure instead of the pressure directly before the cylinders to the pilot?

While I can confirm that the throttle workings in the DB are somewhat odd in that the pilot controlled throttle does not fully open above full throttle altitude, I found no pilot instructions that there was something to do about this as routine. The basic handling was to go by rpm, not boost, with no rpm increase noted above full throttle altitude, even on a couple of Betriebsdatentafeln that have an optional, separate column for high altitude. The column was left blank. I looked into this just recently.

vodoradiator = water cooler.

Good to see this up and running, hope you can sort out the little problems in no time. Guess it's good you finally have this off your to do list.

Certainly - the more options, the better.

The 16 squadrons mentioned are listed in reference 41 of the article and contain only 2 Spitfire IX squadrons. 4 Tempest, 4 Mustang, 3 Spitfire XIV, 2 Mosquito XIX and 1 Mosquito XIII making up the rest. http://www.wwiiaircraftperformance.org/150grade/backfire-2.jpg