Ideal Luftwaffe starting 1/1/1936

[tomo pauk]

Some additional data about German engines.
The DB-601C and D were two-stage developments of the DB-601 line. Dimensions were much like the DB-601E. Dry weight was 685 kg (25 kg more than 601E). Max RPM was 2700, the compression ratio was 7.2:1 - both values as the 601E. Take off power was 1300 PS. The rated altitude was at 8000 m, the 'Steig und Kampfleistung' there was 1120 PS ( ie. 1105 HP at 26250 ft, 1105 HP; vs. 4900m and 1200 PS for the 601E). Unfortunately, I don't have values for Notleistung of the 601C/D. I also don't know whether the inter-cooler was used. Fuel was 87 oct - very much likely that no inter-cooler was used?
My understanding is that the only important difference between C and D was the prop reduction gear ratio, being 0.49 and 0.53 respective.
The data is from my newly-acquired 'Flugmotoren und Strahltriebwerke' book If they only dealt more with the ww2 piston engines...

The same book claims that all improvements of the DB-601 series were incorporated in the development of the DB-603.

 

[wiking85]

Any info on the Jumo 222?

Also to your point about the 601 improvements 'being incorporated into the development of the 603', that only indicates that those improvements were added to the process, not that they were integral to making the 603 reliable and functional. I haven't denied that the 601 improvements were included in the development process, but rather that the 601 innovations added nothing that uninterrupted 603 development from 1936 couldn't have added on its own and perhaps even better without having to try and add in smaller engine developments to a larger engine.

 

[tomo pauk]

Re. 603: I have no problems admitting that more resources, earlier on, would've make the engine a more useful asset. What I do not agree is that DB would've had the DB-603A running on 2700 rpm and 1.40 ata already in 1941.

Re 222: yes, the 5 page chapter is in the book. I didn't have much time to consume it, and there is only 10 days since my eye laser surgery was done - small print in the whole book, along with even smaller quoted text and picture captions, is quite tiring at this time. At any rate, the new issue of the book that covers only Junkers engines is deadlined for June/July, so that is my next buy. Hopefully, my picture about the Jumo 222 will be complete then
From the table: Jumo 222 A/B weighted, dry, 1084 kg. Power for take off was 2000 PS at 1.42 ata, Steig und Kampfleistung was 1980 (!!) PS at 6400 m; all at 2900 RPM. The 222 E/F have had increased bore/volume, two-stage (and two-speed?) supercharger and intercooler, T.O. rating was 2500 PS at 3000 RPM and 1.5 ata, S. K.leistung was 1750 PS at 2900 RPM and 9400 m. Weight 1370 kg dry. With MW-50, TO power was 2900 PS.
The 222 C/D received increase in stroke/volume, single-stage two-speed s.charger, 1180 kg dry. TO power 3000 PS, rated height was 5300 m, the power at that altitude is not stated.

 

[wiking85]

Thanks! I'm curious about whether there is any reference about the reasons it never became ready, i.e. technical vs. bureaucratic problems

 

[rinkol]

I recall someone posting information on a DB patent application for a two stage supercharger arrangement on another forum. Basically, the idea was to have single stage superchargers mounted on each side of the engine (rather than on one side as for the common DB 601/603/605 variants) with one supercharger feeding the other. This seems like a reasonable arrangement and would seem like a logical choice for the DB 601C/D, but I don't have any definite information as to the actual configuration. In any case, it seems unlikely that there would be an intercooler as this would likely result in a larger weight difference with the DB 601E. It would be interesting to find out what the problems were with this line of development. This was apparently a serious development as the design of the Hs 130A was based on this engine and its non-availability adversely affected the viability of that aircraft.

 

[tomo pauk]

Seems that Jumo 222 have had it's fair share of developmental problems, by the book 'Flugmotoren und Strahltriebwerke'.
It took from March 1940 until October of 1941 for the Jumo 222 (a pair of them) to actually power an aircraft on their own - the Ju-288V-5. That is despite passing the 100 hour test in April of 1941. The main problems were corrosion, vibrations and damaged bearings.
The RLM wanted more from the Ju-288 now (crew to 4 members, increased payload), and the engine of 2000 HP was not enough. The book states that the engines' prototypes installed in Ju-288 prototypes were also incapable to develop full power of 2000 PS either, while experiencing issues. So, despite some engines that were capable to do do the 100 hr test twice, RLM was of the opinion that Jumo 222 cannot develop 2000 PS. Hence they cancelled the Jumo 222 program on 24th Dec 1941. The Ostmark factory will be equipped for production of the DB-603; previously it was expected that factory will produce 1000 of Jumo 222 monthly.
The book then names several issues that were plaguing the design even after cancellation, namely the master and connecting rod assemblies, the bearings (change of materials was attempted), damaged pistons, rough running (the attempted cure was the change in firing order), coolant turned into steam damaging the cylinder heads. We're at Spring of 1942 already, and the 'improved' prototypes of the engine experience the issues. How distant is the really workable and reliable engine?
Despite all of those issues and the cancelled contract, the Jumo attempted at increase of swept volume to 49.85 L by increasing the bore from 135mm to 140mm, in order to achieve the take off power of 2500 PS. The book mentions the take off power, acommplished on the test bench on 26th May 1942, of 3000 PS. In the same time, the Ju-288V 9 took off with Jumo 222A/B that were providing 2500 PS for take off (??). That engines were from 'baureihe 3', ie. 'production series 3'.
After the DB-606 and 610 developed issues on their own, Jumo received a contract, on 5th August 1942, for the series production to be undertaken in Prague. The 1st engines from there are expected from October of 1944. However, due to the ongoing work on Jumo 211 versions and the Jumo 213, there is no enough workshop space and test stands to iron out the bugs of the 222 and prepare the design for mass production. (Hence my '??' above: whatever A/C was taking off on the 222 on assumed full power, it was more of a calculated risk, rather than a product of confidence in the engine?)
At the start of December 1942, the 1st 100 hr test was passed by 'baureihe 3' Jumo 222A/B with 2500 PS for take off, clearing that engine for mass production. But, because of the realities of war, the Bomber B, J-288 and Jumo 222 were cancelled in summer of 1943. The other Jumo engine got priority, namely the Jumo 213, since it was an important part of the fighter program. After heavy bombing of Dessau in April 1944, the design team of the 222 was moved in Oberursel.

The book further mentions the development of ever more powerful variants, but that comes into 'too little, too late' category even more than the early 222A/B.

 

[wiking85]

Thanks for typing that up. It undermines Budrass's contention that the 222 was killed by administrative order, rather than technical issues. Hope you're feeling better after your surgery.

 

[tomo pauk]

Thanks, everything is okay
It is pretty clear that Jumo 222 have had issues with about any important part. Maybe, with more support from RLM, and satisfaction with, say, 1800 PS for the start, the engine would be in use from some time in 1942. But the same (ie. development with more support) would be true for DB-603 or BMW-801, so the 222 has no advantage? And it would be heavier and more expensive than those two.

 

[wiking85]

Thanks, everything is okay
It is pretty clear that Jumo 222 have had issues with about any important part. Maybe, with more support from RLM, and satisfaction with, say, 1800 PS for the start, the engine would be in use from some time in 1942. But the same (ie. development with more support) would be true for DB-603 or BMW-801, so the 222 has no advantage? And it would be heavier and more expensive than those two.

Yeah, it seems that the 2000hp engine was a bridge too far technically for the era. Instead it would make more sense to go for the 603, 801, and later when it becomes possible the 213 (with four valves per cylinder, rather than the historical 3).
BTW glad to hear you're feeling better.

 

[tomo pauk]

There was also possibility of the Jumo 211 with 4 valves per cyl.
Further, the RLM was of the opinion that BMW should concentrate on radials, and the merger with Bramo sealed the 'deal'. Interestingly enough, BMW was designing two V-12s in mid 1930s, the bigger, BMW 117 of 36 L, was capable for 905 PS on 2320 rpm, dry weight 525 kg. The 'F. und S.' book gives as much as 1100 PS at 2580 rpm for take off power, but it is unclear to me whether it was just a test stand value, or something really achieved during flights - the 117 was never more than an experimental engine, and all work on it was cancelled in 1937. The book claim that mentioned 905 PS was max continuous power at SL. For quite a light engine, the 1100 PS value does not sound reliable.
Same fate fell on the BMW 116, engine of 20.76 L and 470 kg. Power values were 750 PS on 3000 RPM for take off, and 620 PS at 2700 rpm for max continuous at SL. That one was cleared for mass production, but concentration on radial engines meant cancellation.

The book mentions several times that direct injection amounted for savings in fuel consumption by 10-15%, depending on engines. Due to more even fuel distribution - no too lean and too rich running cylinders?

Few posts were for a long range maritime patrol aircraft. The main victory would be to put those on Kriegsmarine command? More produced Do-26s? The Fw-200 with diesels? A dedicated LR MP aircraft? Time to consider in-flight refueling?

 

[wiking85]

On naval recon the Do26 seems like the only viable option; its ready to go, so no need to reengineer the Fw200, which would take too much time, while in flight refueling requires way too much experimenting and training to pull off by 1940. At that point is just better to go with a seaplane that rendezvous with a seaplane tender in the Atlantic. All they need is to get the Hohentwiel system in service, which was technically possible from 1938 on, they just needed the concept to develop it.

 

[tomo pauk]

A sea plane tender in the Atlantic depends too much on whether the RN will discover it or not? How about a supply submarine to top-off the fuel and oil tanks?

 

[Shortround6]

Same fate fell on the BMW 116, engine of 20.76 L and 470 kg. Power values were 750 PS on 3000 RPM for take off, and 620 PS at 2700 rpm for max continuous at SL. That one was cleared for mass production, but concentration on radial engines meant cancellation.

It also wasn't going to do much of anything the Jumo 210 wasn't going to do. 19.7 liters and 442kg?

The book mentions several times that direct injection amounted for savings in fuel consumption by 10-15%, depending on engines. Due to more even fuel distribution - no too lean and too rich running cylinders?

Could very well be, I believe British evaluations credited it with about that amount of fuel savings.

Few posts were for a long range maritime patrol aircraft. The main victory would be to put those on Kriegsmarine command? More produced Do-26s? The Fw-200 with diesels? A dedicated LR MP aircraft? Time to consider in-flight refueling?

KISS (Keep It Simple Stup*d) FW 200 properly redesigned for the role rather than 'quicky/cheap' conversion. Beef up structure a bit and if needed plumb under wing bomb racks for drop tanks. In-flight refueling won't by much except to top off tanks at start of mission while still in friendly airspace. Germans have enough problems with engines without trying to come up with a "new" diesel for limited application.

 

[wiking85]

A sea plane tender in the Atlantic depends too much on whether the RN will discover it or not? How about a supply submarine to top-off the fuel and oil tanks?

IIRC supply ships for German surface warships did have a reasonable success rate staying out of the RN's net, while the 'Milchkuh' Uboats did not have that success. IIRC it was the US entry into the war that really shut down Atlantic supply operations for the KM.
https://en.wikipedia.org/wiki/German_tanker_Altmark
https://en.wikipedia.org/wiki/German_Type_XIV_submarine

 

[Shortround6]

Landing seaplanes in the Atlantic is waaaaay too risky. Flying boats usually tried to land/take off in sheltered coastal waters. You need Maritime recon every day, every week, every month, weather permitting. weather permits flying over the ocean a lot more than it permits landing in ocean.Just google "atlantic convoy pictures"

 

[tomo pauk]

It also wasn't going to do much of anything the Jumo 210 wasn't going to do. 19.7 liters and 442kg?

Yep, no much point in muddling with the 116. The BMW 117 was to offer a better base for an really useful engine, had Germans/RLM decided to go for that one.

KISS (Keep It Simple Stup*d) FW 200 properly redesigned for the role rather than 'quicky/cheap' conversion. Beef up structure a bit and if needed plumb under wing bomb racks for drop tanks. In-flight refueling won't by much except to top off tanks at start of mission while still in friendly airspace. Germans have enough problems with engines without trying to come up with a "new" diesel for limited application.

Agreed that, if one wants a battle-worthy Fw-200, a proper modification would be necessary. Not sure whether the new diesels are needed - the Jumo 205 was offering 880 PS for take off in 1940 on 595 kg, the Bramo 323 offered 1000 PS (1100 with C3 fuel) on 550 kg. The 207A was offering the same 880 PS, but were heavier, at 805 kg (weight with turbo?). The 207B (for Ju-86) was at 1000 PS, the up-rated 207C 1100 (for Bv-222) PS for TO.
The radial will offer somewhat lighter weight, but the fuel consumption was 1/3rd greater. Diesels will not be for a limited application, all transports and plenty of training airplanes can use those.

 

[wiking85]

Agreed that, if one wants a battle-worthy Fw-200, a proper modification would be necessary. Not sure whether the new diesels are needed - the Jumo 205 was offering 880 PS for take off in 1940 on 595 kg, the Bramo 323 offered 1000 PS (1100 with C3 fuel) on 550 kg. The 207A was offering the same 880 PS, but were heavier, at 805 kg (weight with turbo?). The 207B (for Ju-86) was at 1000 PS, the up-rated 207C 1100 (for Bv-222) PS for TO.
The radial will offer somewhat lighter weight, but the fuel consumption was 1/3rd greater. Diesels will not be for a limited application, all transports and plenty of training airplanes can use those.

Frankly the bombing role is overrated anyway; the utility is far more with convoy spotting for Uboats.
As to the Bramo vs Jumo, the former required the more expensive and more scarce Avgas, while the Jumo could use the cheaper and more plentiful diesel fuel with better fuel consumption rates. For long range recon then the diesel is a must. IIRC the Jumo 205 was only using 6 cylinders too.
I'm surprised more German aircraft didn't use diesels given their secondary role (such as the Ju52 transports).

 

[Shortround6]

The Diesels are limited application, they only make sense if the flight is long enough that the combined weight of the engines and fuel are less for diesel than for the gasoline engine. Short range flights with diesel engines simply means less payload. The Jumo diesels did alright with long steady speed flights but had problems with rapid or frequent throttle changes (which rather rules them out for trainers). Lufthansa tried them as did the Luftwaffe and the while a 1940/41 diesel may have been better, the mid/late 30s diesels required too much maintenance. The Ju 207 weighed at least as much as a Jumo 211 and at times was offering around 20% less power.

 

[Shortround6]

Frankly the bombing role is overrated anyway; the utility is far more with convoy spotting for Uboats.
As to the Bramo vs Jumo, the former required the more expensive and more scarce Avgas, while the Jumo could use the cheaper and more plentiful diesel fuel with better fuel consumption rates. For long range recon then the diesel is a must. IIRC the Jumo 205 was only using 6 cylinders too.
I'm surprised more German aircraft didn't use diesels given their secondary role (such as the Ju52 transports).

See above and please look at the Jumo diesels again, only 6 cylinders but 12 pistons and two crankshafts. See: http://www.enginehistory.org/Diesels/CH4.pdf

These are not cheap or easy to produce engines.

 

[tomo pauk]

Indeed, the LR MPA must be used to find out convoys and dispatch the acquired data to the subs. The Jumo diesels (204, 205, 207, 208 ) did indeed use only 6 cylinders, but also 12 pistons - each cylinder was shared by two opposing pistons.
The Jumo 208 was being developed from 1939, it featured different cylinder dimensions (bore increased from 105 to 130 mm), hence the volume was increased from 16.6L to 25.5 L. I don't know the weight. Power was 1500 PS for take off, 1100 PS was Steig Kampfleistung at 10000 m through use of turbocharger. Engine remained in prototype stage.
From 1940, another diesel was tested, the Jumo 223. A 24 cylinder engine - with 48 pistons!? Due to small cylinders (80mm bore, stroke 2 x 120 mm), the permissible RPM skyrocketed at 4400 rpm, the power was at 2500 PS for take off. The engine weight went also considerably up, at 1400 kg (with turbo?). Remained at prototype stage. Cylinder layout was similar to the Napier Deltic, but with 4 cylinder blocks, rather than 3. A 'diamond' layout, we might say.