# Four-engined Junkers 288? <delurk>!



## ktank (May 27, 2014)

Be gentle, it's my first time 

OK, there's a large, advanced twin engined medium bomber project, which includes provision for dive bombing. To power it a radical large new generation engine is needed, however said engine runs into serious development problems and can't take the project's increasing weight.

So far the history of the Junkers 288 and the Avro Manchester are parallel...

But with the Manchester Rolls Royce scrapped the troublesome Vulture engine, and Avro redesigned the Manchester to take four proven Merlins in an enlarged wing. This meant dive bombing was out but it was obvious it wasn't required. The result was the Lancaster, and the rest is history.

Was there any similar thought, given the Junkers 222 debacle, to re-design the Ju288 with four Jumo 211s, which I gather were in plentiful supply and well-proven?


----------



## davebender (May 27, 2014)

If Luftwaffe were interested in heavy bombers with four separate engines it would have happened long before Ju-288 came along. 

Heinkel proposed He-177B during 1938 powered by four Jumo 211 engines. Low priority research continued into 1944 resulting in He-274 and He-277 designs. However none of these four engine designs were seriously considered for mass production.


----------



## wiking85 (May 27, 2014)

You mean the Ju488?
Junkers Ju 488 Luft '46 Entry


----------



## Capt. Vick (May 27, 2014)

wiking85 said:


> You mean the Ju488?
> Junkers Ju 488 Luft '46 Entry



Weren't they building that in France when it was sabotaged or bombed?


----------



## wiking85 (May 27, 2014)

Capt. Vick said:


> Weren't they building that in France when it was sabotaged or bombed?


Yep, but it was also cancelled, so it died many deaths and ended up in French hands in the end.


----------



## GrauGeist (May 27, 2014)

Welcome to the forums!

With the death of General Wever in 1936, the four engine heavy bomber ideology in the Luftwaffe nearly died with him.

One of the only standard production heavy bombers that was produced, was the He177 (a result of Wever's Bomber A program)

But in answer to your question, yes, the Luftwaffe was looking at a Ju488, which was originally designed for 4 BMW801J radials, however 4 Jumo222 were to be the replacements. Only two were nearly completed, the other airframes never reached completion. After sabotage and allied bombings, the project was abandoned, none ever flew.

There were several types proposed and prototyped and several types were built and used in limited service, otherwise. Of course, dive-bombing with a four engined bomber is completely out of the question (that would be quite a ride!)

Do19 - three built, one used as a transport
Ju89 - two built, used as transports
Ju90 - 18 built, based on the Ju89, designed as a passenger liner but pressed into service as transports
Ju290 - 65 built, based on the Ju90, used as heavy transport and maritime patrol
Ju390 - 2 built, 6 engined version of the Ju290. Designed for extreme long range, they were never able to produce any quantity or put them into service.
Me264 - 3 built, two damaged by Allied bombing raids, one was used as a transport but eventually destroyed in a bombing raid as well.
Fw200 - 275 built, used as maritime patrol, bomber and transport.

These examples show that the Luftwaffe (and aircraft companies) never took the idea of a 4 engined bomber off the table, but the idea never went beyond limited runs for many reasons.


----------



## Koopernic (May 27, 2014)

That's exactly what Focke-Wulf proposed doing with the Fw 191 when they put forward the Fw 191*C* (the *C* variant replaced the twin engines with 4 separate engines). 

The Fw 191 was a competitor with the Ju 288 in the bomber B program.

This was a small aircraft, less than 2/3rds of the size and weight of a B-17G or Lancaster but assuming the 1420hp Jumo 211J with greater sea level power than either of the the allied bombers and a pair of such engines had indeed greater power than the Jumo 222 (2500hp). The Jumo 222 version was flown as a 2200hp variant at 388mph so its fair to say that at least this speed could be achieved with 2840hp available from a pair of Jumo 211J.

Moreover developing a 4 engined version would provide easy access to exchanging in more capable engines such as the BMW801D, BMW801TJ, Jumo 213A or E, DB603 or DB605AS. Such a high speed would have given the Luftwaffe a survivable bomber. One that wouldn't suffer high attrition or require gruesome sacrifices and attrition from its crews who had to operate without air superiority. The kind of speeds expected of Bomber B would have stretched even Mosquito night fighters to the limit and been a potent maritime strike aircraft able to outrun or match most allied naval fighters.

There are slight aerodynamic advantages to a two engined design over a 4 engined one however they are minimal, the primary advantage is the aeroelastic advantage of not having the outer engines cantilevered at the wing tips where they can cause flutter in a dive. From 1941/42 onwards the Stuvi 5B computing dive bombing sight was available as was the Lotfe 7C gyro stabilized tracking computing bomb sight and so steep dive bombing was no longer required.

These new *"Bomber B"* had large an well organized bomb bays. I doubt they would have much more range than the older twin engined bombers due to the fuel volume issue in such a small fuselage but they would carry much heavier loads to the limit of their range at high speed thus improving effective range and they could've presumably carry drop tanks such as the Do 217 could to push range beyond 2000 miles.

The problem was that once aircraft such as the Ju 288, He 177, Me 210 failed to meet their deadlines the production plants had to expand on existing types which meant that even when the aforementioned types were perfected it meant greatly disrupting the existing system.

The RLM/Luftwaffe and Industry did seem to learn and started to develop "Plan B" for risky parts of a design in parallel but it was too late.

History does record that Enest Heinkel begged to rapidly develop a 4 engined He 177 but was denied or at least not officially supported and did so privately and that Focke-Wulf proposed the Bomber B as the 4 engined Fw 191C, no doubt the Ju 288 could also have been offered as a 4 engined version just as easily as AVRO converted the Manchester into the Lancaster.

There were procurement issues in the German system; the Air Ministry (RLM) seemed to specifiy aircraft the Luftwaffe sometimes didn't need, want or expect. An elaborate system of liaison was developed but obviously too late.


----------



## Capt. Vick (May 28, 2014)

wiking85 said:


> Yep, but it was also cancelled, so it died many deaths and ended up in French hands in the end.



A buddy of mine sent me this link. It's about a book (in French) on the He 274 and Ju 488.

Heinkel He 274 et Junkers Ju 488 | Artipresse


----------



## m37b1 (May 28, 2014)

I've often wondered why the FW200 wasn't developed into a true heavy bomber. Given it's airliner roots, it may not have been ideal, but I would think that given appropriate priority/funding, it could have been: strengthened/armored/armed, given a decent bomb sight, increased HP to account for added weight . . . . Making it roughly equivalent to the allied 4-engine bombers.


----------



## wiking85 (May 28, 2014)

m37b1 said:


> I've often wondered why the FW200 wasn't developed into a true heavy bomber. Given it's airliner roots, it may not have been ideal, but I would think that given appropriate priority/funding, it could have been: strengthened/armored/armed, given a decent bomb sight, increased HP to account for added weight . . . . Making it roughly equivalent to the allied 4-engine bombers.



The He177 was in production and far too many resources were sunk into its development to give up on it. The FW200 was mostly being made via batch work, but always understood to be a placeholder; later the Ju290 showed up as a replacement, while the HE177 was always 'just about ready', so adapting an airframe like the FW200 with only one real purpose didn't make sense given the other stuff on the horizon.


----------



## Shortround6 (May 28, 2014)

Perhaps??

The problem comes in with _how much_ modification is needed or desired. Every increase in armor, armament, etc is an increase in weight. Every increase (or major step increase) in weight _may_ require stronger (read heavier) landing gear, stronger (read heavier) fuselage framing, stronger (read heavier) wing construction. The FW 200 had a few structural strength issues as it was. Had the Germans viewed it as a true operational type instead of a "filler" to be built in the fewest numbers while waiting for the _Vundar_ planes to show up perhaps more could have been done with it. 

As I said though, how far do you try and take it. The FW 200 started several thousand pounds lighter than early B-17s and the B-17s piled on so much weight that some of the later versions weighed _empty_ what the first dozen or so weighed weighed when at _normal_ take-off weight ( about 10,000lbs more). Later versions had some structural beefing up done. 

Germans also have and engine problem. Their 9 cylinder radials don't quite track the American R-1820 and R-1830 for power ( year by year in the early part of the war) and the liquid cooled engines weigh several hundred pounds more per engine installed. 

It starts to get real complicated rather quickly and it depends on how close you want to get to the allied bombers.

Better than Historic Fw 200 shouldn't be _that_ hard. Equivlent to a B-17 is very hard and equivalent to British Bombers using 1600hp Hercules engines isn't going to happen unless you can use four BMW 801s or weight until 1943/44 for the DB 603 engine.


----------



## m37b1 (May 28, 2014)

Shortround6 said:


> Perhaps??
> 
> The problem comes in with _how much_ modification is needed or desired. Every increase in armor, armament, etc is an increase in weight. Every increase (or major step increase) in weight _may_ require stronger (read heavier) landing gear, stronger (read heavier) fuselage framing, stronger (read heavier) wing construction. The FW 200 had a few structural strength issues as it was. Had the Germans viewed it as a true operational type instead of a "filler" to be built in the fewest numbers while waiting for the _Vundar_ planes to show up perhaps more could have been done with it.
> 
> ...




Agreed on all counts. 

Just wondering if had they taken that route, would they have had an effective strategic bomber? B-17 is a good example of steady improvement. Could the FW200 have benefitted from a similar program?


----------



## Shortround6 (May 28, 2014)

Depends.

It _could have benefited_, But the Germans have no turbos to boost power of the 1100-1200 take-off power engines at 18-15,000ft. The Germans dropped the ball on simple power turrets and went for remote controlled barbettes (ala B-29?).

FW 200 needs a modified fuselage to get the bomb bay _inside_ the fuselage and not scabbed onto the bottom creating extra drag and limiting bomb size/s and/or carrying the bulk of the bomb load externally. 
FW 200 needs a strengthened fuselage to stop breaking it's back on landing at times or having rear spar drop out of the airplane. 







FW 200 needs a revamped fuel system (this might not be that hard to do ?) 
FW 200 needs revamped defensive armament.
FW 200 needs better engines ?

Strengthened airframe cuts into payload at same gross weight. Raising gross weight cuts performance with same engines. New engines raises gross weight or cuts into payload and around and around and around. 

Something could have been done but trying to the FW 200 into a B-17 probably wasn't going to happen.

Reactions: Like Like:
1 | Like List reactions


----------



## tomo pauk (May 28, 2014)

Shortround6 said:


> Perhaps??
> 
> The problem comes in with _how much_ modification is needed or desired. Every increase in armor, armament, etc is an increase in weight. Every increase (or major step increase) in weight _may_ require stronger (read heavier) landing gear, stronger (read heavier) fuselage framing, stronger (read heavier) wing construction. The FW 200 had a few structural strength issues as it was. Had the Germans viewed it as a true operational type instead of a "filler" to be built in the fewest numbers while waiting for the _Vundar_ planes to show up perhaps more could have been done with it.
> 
> ...



The Germans did not have had the engine problem. The V-12s offer 1150-1200 PS for take off for take off as early as 1939, and up to 1420 PS in mid 1941. The extra weight of cooling system is in the ballpark with the extra weight of the turbo systems the German engines don't have. Something as good as Lancaster (and better than turboed B-17/24 under 20000 ft) was very much feasible in mid 1941, but Fw-200 will not fill those shoes - new design is needed? We can also note that German V-12s will get better fuel mileage than Allied V-12s.
German problem was how to produce as much engines they and their allies needed, and reverting the V-12s for 4-engined bomber production does not help with that.


----------



## wiking85 (May 28, 2014)

tomo pauk said:


> The Germans did not have had the engine problem. The V-12s offer 1150-1200 PS for take off for take off as early as 1939, and up to 1420 PS in mid 1941. The extra weight of cooling system is in the ballpark with the extra weight of the turbo systems the German engines don't have. Something as good as Lancaster (and better than turboed B-17/24 under 20000 ft) was very much feasible in mid 1941, but Fw-200 will not fill those shoes - new design is needed? We can also note that German V-12s will get better fuel mileage than Allied V-12s.
> German problem was how to produce as much engines they and their allies needed, and reverting the V-12s for 4-engined bomber production does not help with that.


Considering all of the DB606/10/13's made for the He177 and there are plenty of DB601/5/3's for a He177B. Or take the Ju290's BMW 801s for a version of the He177. Basically all that is needed is for the LW to give up on the coupled engine version of the HE177 by 1940-41 to get a 1942-43 He177B with four engines, either Jumo 211s, DB601/3/5, or even BMW 801. Hell, you can even use the BMW 323s used in the FW200 for the He177B if you're really that desperate for engines, but given the number of DB's furnished for the He177 that's the best option, unless you want to convert the capacity used for the DB's into Jumo capacity. Or even keep the Ostmark facility in Jumo's hands to make more Jumo 211s or 213s instead of turning it over to Daimler and getting Jumo sabotaging the transfer and of course the need to retool for Daimler engines, which wasn't very feasible it turned out.

Edit:
I though the 1420PS Jumos weren't around until 1943? I think 1941 only saw the 1350PS Jumo 211F enter production and service? The DB601E theoretically offered 1350PS in 1941, but was restricted due to design flaws. Same with the DB601N, which was supposed to offer 1420PS in 1940, but ended up at 1250PS at best with C3 fuel.


----------



## ktank (May 28, 2014)

No, the 488 was to use four Jumo 222s. And if the 222 had been suitable for service, the 288 would have gone into production with them... I'm staggered that at that late stage of the war the RLM was *still* getting aircraft developed based around an engine that had already proved to be a dud.


----------



## Shortround6 (May 28, 2014)

The Germans did have a bit of engine problem at the beginning of the war (1939-41?) in regards to the Condor as the two radial engines (BMW 132 and Bramo 323) are a bit below Allied standards. 
The BMW 132 never got above 960hp/PS take off (sources may not have converted) and managed that by using a supercharger gear that peaked at 1480ft (?). Version that offered 890hp at 11,500ft was restricted to 800hp at sea level. 
The Bramo 323 is a bit better as it was fitted (in some models) with a two speed supercharger which allowed (_without_ water injection, 1000hp at sea level for take-off and 940hp at at 13,200ft. By using water injection the R-2 model (shows up when in 1941?) and running at 2600rpm instead of 2500rpm and using 1.64 ata instead of 1.5 it gets 1200hp. It weighs 1320lbs (?) 
Climbing power is about 800hp or below for both engines. 

In comparison a Wright R-1820G200 with two speed supercharger was good for 1200hp for take-off and 1000hp climb (max continuous) to 4500ft and was good for 900hp climb (max continuous) at 14,000ft. Single speed engine with trubo was good for 1000hp max continuous to over 25,000ft. 

The Jumo 211s do offer 1100-1200hp in 1939 and a good part of 1940 and do get to 1300-1400hp by 1941 but then we are back to looking at climbing power (max continous) and for the 1200hp for take-off B,D, G and H models this was around 930hp at both sea level and 17,000ft. The Jumo 211F does offer 1340hp for take-off and and 1120hp max con in low gear at sea level and 1060hp at 17,000ft. 

The Merlin XX can provide 1240hp at 10,000ft and 1175hp at 17,000ft at it's 30 minute rating. The Hercules isn't quite as good up high with the more common war time models offering either 1315hp climb power at 2000ft or 1355hp at 4750ft in low gear or 1185hp at 12,750ft or 1240hp at 12,000ft. the 1590/1615hp for take-off helped the heavy planes though. The early 1375hp Hercules engines will of course have less climb power. 

The climb power is important to bombers as they can take quite a while to climb to operating altitude in loaded condition. He 111H-16 took 23.5 minutes to reach 19,685ft at max loaded weight.
One source gives a service ceiling of 19,000ft for the Fw 200.


----------



## Koopernic (May 28, 2014)

The Germans problem with power on the BMW 132 (PW Hornet Based) and Bramo 323 (Bristol Jupiter based) is almost insoluble due to the use of 87 octane on these engines but improved with fuel injection, metrication and presumably other features. (Note however the BMW 801 was all their own work).

BMW did try a system of switching the Bramo 323 over to C3 (96/130 octane fuel) during takeoff and then to B4 (87 octane) during cruise on the Ju 352, they also eventually did develop a two speed supercharger to get to 1200hp as well as MW50; at what date I don't know, I only used Wikipedia.

AFAIK the Jumo 211J was in service in 1942 and the Jumo 211F in 1941, both running on B4(87 octane) fuel on the Ju 88A4, the Ju 88A5 actually preceded the Ju 88A4 in production since the Jumo 211F/J was not yet available. Else we had Jumo 211B with 1200hp and a two speed supercharger.

The Germans, as to be expected, had a word for an aero engine optimized for sea level power: "bodenmotor" (opposite of hohenmotor ie high altitude motor). Quite a few bodenmotor were built for record breaking aircraft and certain transport and sea planes. It usually involved specific supercharger ratios, supercharger impellers, Water Injection of some kind to overboost but with maximum efficiency. Even diesels variants such as the Jumo 207 were so optimized. (hence we have the somewhat controversial Fw 190D9 with the "A-ladder als bodenmotor" roughly translated as "compressor A(1st gear) as sea level motor" which managed 640kmh/397 mph at sea level)

The Germans had a very ambitious high altitude development program, the one at BMW was called "Hubertus" program and the high altitude test chamber complete with wind tunnels and refrigeration systems was modified to develop jet engines and then latter taken as war booty to the USA after having tested the DeHaviland jet engines in Germany post war. The allies had nothing like them.

Typically these engines had full throttle heights of over 38500ft. Some used turbo chargers, others such as the DB628 was a DB605 based engine with two independent mechanical superchargers. Stage one was an annular unit (around the propeller gearbox hub) with variable pitch fan and the second stage the familiar transverse variable speed drive. It was probably to ambitious as they couldn't quite get them into production (apart from the BMW 801TJ).

The Ju 488 (basically a hybrid stretched Ju 288/388 with BMW 801TJ was expected to have a service ceiling of 50,000ft.

There were more advanced versions of the Jumo 211F and J these were the N and P but not pro-ceded with, presumably due to favoring Jumo 213.

I think that by 1940 the Germans should have been secure that 4 x Jumo 211 could have provided sufficient power to replace 2 x Jumo 222 (2500hp target power) irrespective of whether the 1200hp Jumo 211B was used or the more powerfull but heavier Jumo 211F or J. 
In fact it's bizzar that the RLM went so far as to fund 3 flying prototypes of Bomber-B (Ju 288, Fw 191, Do 317) but did not advance one of them as a 4 engined type as insurance against engine related issues.

It turns out the solution they chose was the DB606 and latter DB610, the same paired engines that ruined the He 177. Ju 288 flown with DB606/610 didn't seem to have the same reliability issues as the He 177. I believe the Ju 288 with DB610 was in fact ordered into production for late 1943 early 44 but fell victim to the cancellation of essentially the entire German bomber program in the face of labor shortages, bombing, fuel shortages and the need for dispersal and hardened factories. The resources went to fighter production and the development of a new generation of jets and technologies. Manfred Griehl's book on the He 177 shows that the maritime He 177 units were able to get their He 177A5 reliable by early 1944 with 220 hours MTBO and a minor one at 110 hours.

The course of aviation history would have changed had Daimler-Benz not put these paired engines on the table.


----------



## Koopernic (May 29, 2014)

The Germans actual managed to get a fair amount of work done in France during the war. Focke-Wulf and Heinkel in particular and it was generally possible to subcontract work to a French firm and get it back on time easier than using say an Allie such as Rumania or Hungary.

The Ju 488 came in two versions, one was basically a stretched Ju 388 with a welded steel tube structure (made in France), while the other had a fully engineered fuselage (built around the Ju 288 and made in Germany). The Heinkel He 274 was a He 177 derivative using 4 x BMW801TJ high altitude turbocharged engines being built in France while the He 277 was a 4 engined version of the He 177 being finished in Vienna Austria using DB603 engines. The French aviation industry survived relatively intact in terms of its abilities.


----------



## ktank (Jun 3, 2014)

"We can also note that German V-12s will get better fuel mileage than Allied V-12s."

Any details on this? I would have thought the higher-octane fuel of the Allies on its own would have given the Allies lower specific fuel consumption.

Note that the DB605, in performance equivalent to a Merlin, was nearly the displacement of the Griffon.


----------



## Shortround6 (Jun 3, 2014)

ktank said:


> "We can also note that German V-12s will get better fuel mileage than Allied V-12s."
> 
> Any details on this? I would have thought the higher-octane fuel of the Allies on its own would have given the Allies lower specific fuel consumption.
> 
> Note that the DB605, in performance equivalent to a Merlin, was nearly the displacement of the Griffon.



Different engine designers emphasized different things in their designs and "fuel mileage" is a different attribute than "Performance" or hp per liter of displacement or hp per pound of engine weight. The Allies _might_ have used the higher octane fuel for lower specific fuel consumption but they didn't. Instead they used it for higher specific power output per unit of displacement. 
High cylinder compression ( a major element in low specific fuel consumption) is in direct opposition to high manifold pressure/boost ( a major element in high specific power output.)

The DB 605, while nearly the displacement of the Griffon was closer in weight to the Merlin and engine weight was much more important to the _airframe_ designer than displacement.


----------



## tomo pauk (Jun 3, 2014)

Part of the 'deal' for lower consumption was also the direct fuel injection, that took care that every cylinder gets exact amount of fuel, for a desired power setting. The engines with one big carburetor needed to run some of the cylinders a bit too rich, so no cylinder is run too lean. 
Here are two tables. One is for the Packard Merlin V-1650-1, a sibling with early Merlin 20 series. Another is for the DB-601E. 445 l/h is about 117.5 US gal/hr, 1350 PS is 1331 HP (consumption and take off power for the DB-601E). Against 133 US gal/hr for 1300 HP for the V-1650-1.
300 l/h is 79 US gal/hr, 1040 PS is 1026 HP (maximum continuous power for the 601E); against 93 US gal/hr for 1010 HP for the V-1650-1.


----------



## Shortround6 (Jun 3, 2014)

And into somewhat more normal cruise settings the DB 601E can give 840 PS (828hp at 5100 meters/16830ft) on 240 liters per hour (63 gallons) while the Merlin on 63 gallons per hour can give 758hp at 16,000ft. A 9.3% advantage for the DB 601E


----------



## Koopernic (Jun 3, 2014)

There was a great deal of smart technology in the DB601E/DB605 that to an extent the automotive world is still catching up on. DB605 even beats the Merlin on frontal area. However, the DB605 wasn't producing equal power outputs to the Merlin in service aircraft till about March 1944. It was then that the Water-Methanol versions started coming into service, the DB605AM. The German engine was 10%-20% behind the Merlin during the BoB which to an extent can be blamed on 100 octane fuel which allowed 12psi or 1310hp for the Merlin III and XII. The German DB601A1 engines could only provide 1100hp, there was a Db601Aa able to do 1170 but for one minute and usually only allowed on bombers for takeoff. The DB601Aa seems to have been an export version for the Swiss with a supercharger set for higher altitudes that was used as a stopgap while the DB601N was debugged and only equipped 25% of 109 and in general was no better than the DB601A1 apart from a slightly higher FTH. After the BoB after the DB's fell further and further behind. The gap closed for a very short time with Me 109F4 with the DB601E engine released to 1.42 ata and the Me 109G1 (and many argue that the Me 109F4 was better than the Spitfire V) but then the Spitifre IX was only 2 months away.

I believe the problem gets down to two things:
1 Spark plug quality. I suppose an aspect of spark plugs is their ability to cool themselves to avoid preignition, handle high temperatures and pressures without deteriorating or failing, to provide a high tension without breaking down to ensure reliable ignition in the prescience of fouling and water injection etc.
2 A Lubrication issue, one of the changes of DB601->DB605 was the replacement of the crankshaft roller bearings with more conventional journal bearings. The higher pressures in the lube system seem to have caused a 'frothing' at higher altitude that wasn't understood till much latter. I'm not sure about this as I am not using primary sources.
3 Fuel quality was an important issue but I think secondary to the above. There were strengthened pistons fitted prior to the release from 1.3 to 1.42 ata but they of themselves did not allow the release.

German pilots were at one point flying 1320hp Me 109G6's against 1700hp Spitfire IX, VIII with Merlin 66 and 70.

If the British had of been able to fit their Mk.V Spitfires with the two speed Merlin's that were assigned to try and make the inferior Hurricane compettive then the 109 would have been under the most dreadful pressure and the Fw 190 scourge blunted much earlier.

However fuel consumption at sustained high speed cruise and military power of the DB seems excellent.

Reactions: Like Like:
1 | Like List reactions


----------



## tomo pauk (Jun 4, 2014)

Koopernic said:


> ... However, the DB605 wasn't producing equal power outputs to the Merlin in service aircraft till about March 1944. It was then that the Water-Methanol versions started coming into service, the DB605AM.



The DB-605AM was been unable to solve the main shortcoming of the DB-605 line, namely the power above 7 km against turboed or two-stage engines fielded by W.Allies. That problem was addressed with the 605AS/ASM, but by then the air war in the ETO was decided.



> The German engine was 10%-20% behind the Merlin during the BoB which to an extent can be blamed on 100 octane fuel which allowed 12psi or 1310hp for the Merlin III and XII.



Blamed? 



> The German DB601A1 engines could only provide 1100hp, there was a Db601Aa able to do 1170 but for one minute and usually only allowed on bombers for takeoff. The DB601Aa seems to have been an export version for the Swiss with a supercharger set for higher altitudes that was used as a stopgap while the DB601N was debugged and only equipped 25% of 109 and in general was no better than the DB601A1 apart from a slightly higher FTH.



The DB-601Aa was the export version of the 601A ('a' is for 'ausland' - foreign country), the supercharger was of lower capacity - good for lower alt, a bit worse for high altitudes. The FTH was at 3700 m, power there was a bit bigger than for the 601A - 1100 PS vs. 1020 PS. The take off power (1 minute duration) was 1175 PS, vs. 1100. We are informed n this forum that many 601Aa engines wound up in Jabo versions of Bf-109 and 110, exactly because of that extra power under 4 km.
The DB-601A have had two different superchargers, to add to the 601Aa. Earlier version gave 1010-1020 PS at 4 km, later version was doing 1020 PS at 4.5 km. Take off power was equal.
I doubt that DB-601N equipped more than a token of Bf-109 produced.




> ...
> German pilots were at one point flying 1320hp Me 109G6's against 1700hp Spitfire IX, VIII with Merlin 66 and 70.



The Me-109G6 was also a much smaller A/C, with less guns ammo weight, and probably less radiators' bulk under wings - should even out a bit the speed comparison? The rate of climb was pretty much in Spitfire's favor, especially at high altitudes; ditto for high speed there.



> If the British had of been able to fit their Mk.V Spitfires with the two speed Merlin's that were assigned to try and make the inferior Hurricane compettive then the 109 would have been under the most dreadful pressure and the Fw 190 scourge blunted much earlier.



Maybe splitting some hairs - there were no problems to install 2-speed Merlin in Spitfire V (it was installed in a handful of Spit IIs, and Spit V received two-speed, two stage Merlins, and also 1-stage 2-speed Griffons), but huge demand for those, mostly for multi-engined bombers, but also for Hurricane, made that task pretty much impossible.


----------



## Koopernic (Jun 4, 2014)

tomo pauk said:


> The DB-605AM was been unable to solve the main shortcoming of the DB-605 line, namely the power above 7 km against turboed or two-stage engines fielded by W.Allies. That problem was addressed with the 605AS/ASM, but by then the air war in the ETO was decided.
> 
> Blamed?
> 
> ...



Thanks for the "a = ausland" info. The Aa seems a tweek rather than an improvement. Playing around with the supercharger settings and short term power periods (WEP, takeoff) ie 1 minute of slightly greater emergency power instead of 5 minutes.

I wouldn't over emphasize the altitude problem. There was no significant 'high altitude problem' for either the Me 109 or the Fw 190A since 95% of their missions were below 6500m which is at or slightly above the full throttle height at which there is typically a rapid decline in speed and climb rate. From late 1943 and certainly 1944 even the USAAF seldom operated above this altitude and you will note that the moderate flying MF (66 series) and 5 series Packard Merlins came to dominate in both the Spitfire and Mustang. The enlarged supercharger of the DB605AS and its subsequent variants (DB605DM,DC/DB) certainly increased the full throttle height. It could have been better but it was enough.

There was certainly a power problem for the Me 109 and that was closed of as I say around March 1944 when engines in the 1700 hp class came in service eventually reaching 2000hp. The two engines, as you know are the:
DB605AM which was essentially a refined DB605A with Water Methanol added, it required C3 fuel AFAIKT, at least initially.
DB605ASM which had an enlarged supercharger as well as the MW50. 
Both had the same power but the ASM at higher altitude.

What matters most is the power since the FTH of the DB605A and BMW801 is reasonable to begin with though the higher FTH is welcome and useful.

It's amazing that the Me 109 was able to function with this huge power gap, if the situation had of been reversed such that the Spitfire had 20% less power than the 109 I doubt the Spitfire would have done as well at all. This situation never arose. I think you'll find that the Spitfire IX and Me 109G6 have essentially the same weights.

There was a two stage DB605L, it worked rather well and there is a speed graph on the ww2 performance testing site but for an early version without the 4 blade prop it needed to cut into the thinner air.

There were nearly 1000 Me 109G with GM-1 nitrous oxide produced, they had fantastic performance when using mixture. The weight consumed by a few hundred pounds of turbo or intercooler can be used instead to carry the same weight in cryogenic nitrous and this was seen as the expedient solution but one needs the power rating to begin with.


----------



## tomo pauk (Jun 5, 2014)

Koopernic said:


> Thanks for the "a = ausland" info. The Aa seems a tweek rather than an improvement. Playing around with the supercharger settings and short term power periods (WEP, takeoff) ie 1 minute of slightly greater emergency power instead of 5 minutes.



I guess we might call the 601Aa a 'tweak'. The power of 1100 PS at 3.7 km was 5 minute rating, as it was 1020 at 4 or 4.5 km for the 601A.



> I wouldn't over emphasize the altitude problem. There was no significant 'high altitude problem' for either the Me 109 or the Fw 190A since 95% of their missions were below 6500m which is at or slightly above the full throttle height at which there is typically a rapid decline in speed and climb rate. From late 1943 and certainly 1944 even the USAAF seldom operated above this altitude and you will note that the moderate flying MF (66 series) and 5 series Packard Merlins came to dominate in both the Spitfire and Mustang.



I'm not sure that there were 5 series Packard Merlins in operative use - it was either V-1650-3 or V-1650-7 in use in P-51s. As you've noted - the problem was not around before mid/late 1943, but then it vehemently backfired in LW's face.



> The enlarged supercharger of the DB605AS and its subsequent variants (DB605DM,DC/DB) certainly increased the full throttle height. It could have been better but it was enough.



Indeed, the hi-alt performance was greatly improved with a big S/C, but it was too late to matter. 



> There was certainly a power problem for the Me 109 and that was closed of as I say around March 1944 when engines in the 1700 hp class came in service eventually reaching 2000hp. The two engines, as you know are the:
> DB605AM which was essentially a refined DB605A with Water Methanol added, it required C3 fuel AFAIKT, at least initially.
> DB605ASM which had an enlarged supercharger as well as the MW50.
> Both had the same power but the ASM at higher altitude.



It took the DB-605D sub-variant, when using both C3 and MW-50 to attain 2 ata, ie. 2000 PS for take off. And that means 1945. I will not enter the quagmire of debating how regularly the 605D was operating on 2 ata 



> What matters most is the power since the FTH of the DB605A and BMW801 is reasonable to begin with though the higher FTH is welcome and useful.



The rated altitude (or FTH) also matters, if the enemy is throwing in it's A/C on high altitude. We can compare eg. DB-605A and 605AS, and then compare those with what Allies were fielding from 1942/43 on.



> It's amazing that the Me 109 was able to function with this huge power gap, if the situation had of been reversed such that the Spitfire had 20% less power than the 109 I doubt the Spitfire would have done as well at all. This situation never arose. I think you'll find that the Spitfire IX and Me 109G6 have essentially the same weights.



It is not that amazing. The Bf-109 was considerably smaller A/C, and size matters. Once the Spitfire received two-stage engine, that, combined with generous wing area, contributed to the plane's competitivness at higher altitudes. 



> There was a two stage DB605L, it worked rather well and there is a speed graph on the ww2 performance testing site but for an early version without the 4 blade prop it needed to cut into the thinner air.



Indeed, the DB-605L shows the advantages of two-stage compressors - it was some 300 PS advantage over the DB-605D at 10 km.



> There were nearly 1000 Me 109G with GM-1 nitrous oxide produced, they had fantastic performance when using mixture. The weight consumed by a few hundred pounds of turbo or intercooler can be used instead to carry the same weight in cryogenic nitrous and this was seen as the expedient solution but one needs the power rating to begin with.



The GM-1 system was offering advantages, but also the disadvantages. Like need to carry it at suitable altitude, while not taking advantage of it, but lugging it until the altitude is reached. A part of the dead weight is still aboard, even after use. The DB-605L did not used intercooler (and no intercooler weighted hundred of pounds), but MW-50 instead.


----------



## Koopernic (Jun 5, 2014)

I don't believe there was ever a time when the Spitfire didn't have a 10% power advantage, I would say throughout preponderance of the war the Spitfire had generally a 20% power advantage over the Me 109.

Battle of Britain
Spitfire I Merlin III with 100 octane, power = 1030hp or 1310hp 9,000 ft (2,700 m) for 5 minutes using 12psi boost.
Spitfire II with Merlin XII power = 1150hp, this engine was able to use constant 12psi boost (1310hp+) and was free of the 5 minute restriction. Also used in BoB.

Me 109E3 with DB601A1 = 990ps, 1100 for 5 minutes. (note it's an A1 not just an A)
Me 109E4 with DB601Aa = 990ps, 1045 for 5 minutes, 1170ps for 1 minute. Doubtful if the 1 minute rating was of use.

Figures for the German engine are in metric horsepower so deduct 1.6%. In detail:

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.

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.

The DB 601N, 1.35 ata for five min and 1175 PS. Rated altitude being 4800m. (there was a second type of 601N, mounted in one in the 109F had better supercharger and IIRC 5200 m rated altitude) and 1260hp, which latter was also cleared for 1.42 ata along with the DB601E presumably giving Me 109F1/F2 the same performance as Me 109F4.


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 a question whether the new s/c was fitted to the Aa as well.) 


In regards to your statement that the Spitfires "generous wing area" being an advantage; it may have been a disadvantage if the tables had of been turned in power and their size extracts a toll in drag. The high coefficients of lift the Me 109's wing can generate at high angles of attack due to its slats come at the disadvantage of even higher drag which leads to loss of height, speed and energy but only when pulling high G, in level flight the small wing is advantageous. With adequate power that can be overcome. I won't claim that with such the 109 could turn inside a Spitfire, though it would help, but what it would do is help greatly turn rates, acceleration, climb, speed, altitude and the 'energy' of a fighter; its ability to position itself favorably.

It should be noted that the DB601 didn't need a high pressure supercharging so much since it's bolt-less head design offered much higher swept volume, greater valve area while the higher compression ratio improved efficiency and power. Really one needs to look at a power versus altitude chart with the DB601 over layed to the Merlin since the altitude curves are radically different. Really, we don't know much about use of GM-1 operationally.

I'm not pushing the 1.98ATA band wagon apart from saying it was certainly used in the closing months of the war in 1945. An Me with the DB605L was tested at 1.75ATA but would have been interesting at 1.98ATA given the higher altitude, if it were possible that is given the higher temperatures resulting from higher pressure ratios. The 1800/1850 hp the DB601DB/DC achieved eliminated the gap to the Merlin except in the event that 100/150 fuel was available to the Merlin.

But, getting back on topic, it seems to me that 4 conventional engines either DB605 or Jumo 211, fitted to the Ju 288 or Fw 191 would have produced a rather excellent fast bomber able to rapidly take advantage of advances in these fighter engines development. No one tried a medium weight bomber with 4 engines. The only loss would be steep diving bombing, not really needed post 1942 with computing bomb sights.


----------



## Shortround6 (Jun 5, 2014)

Seems to be turning into another Sptifire vs 109 thread. Or Merlin vs DB 60? thread. 

The Merlin XII was _not_ free of the 5 min. restriction. What it could do was climb (1 hour) at 2850rpm and 9lbs boost instead of the Merlin III's climb rating of 2600rpm and 6 1/4lbs. Max cruise went from 2600rpm/4 1/2lb to 2650/7lbs. 
Early testing and early service use used a 9lb boost limit at 3000rpm with 12lbs available, like the Merlin III, by operating the boost control cut-out. 



> It should be noted that the DB601 didn't need a high pressure supercharging since it's bolt-less head design offered much higher swept volume, greater valve area while the higher compression ratio improved efficiency and power.



While this is true (mostly) it is also true that the DB601 _could not *use*_ high pressure supercharging with it's service fuel without wrecking the engine. 12lb boost being roughly 1.8 ata and 6lb boost being roughly 1.4 ata. High compression does improve efficiency but it actually limits peak power in a supercharged engine because a higher compression ratio limits the amount of boost that can be used with a given fuel. 
Let us assume for arguments sake, that the British had a choice when they got 100 octane fuel of either raising the compression ratio or raising the boost limit. They did raise the boost limit and at 12lbs (everything being equal, which it often is not) the engine is consuming about 29% more air than at 6lbs boost. tracks the power change fairly well. Perhaps they could have kept the 6lb boost and fitted high compression pistons to boost the compression to 8 or 8.2 like the DB 601N. The trouble with this is approach is that while it increases the fuel economy by about 10% it only increases the power by about 11% (for an 8:1 compression ratio) yet it increases the _peak_ pressure in the cylinder by around 35%. Granted using more boost will increase the peak pressure in the cylinder too, but obviously the high boost approach gives more power for the same fuel grade(Allison used a higher compression ratio than the Merlin and lagged a bit in power on a given fuel but since the Allison was about 5% bigger in displacement, that covered about 1/2 the power difference and a 5% difference in power doesn't amount to much in the real world unless you are using stop watches).

Reactions: Like Like:
1 | Like List reactions


----------



## tomo pauk (Jun 6, 2014)

Koopernic said:


> I don't believe there was ever a time when the Spitfire didn't have a 10% power advantage, I would say throughout preponderance of the war the Spitfire had generally a 20% power advantage over the Me 109.



Agreed with Shotround6 - Spit vs. 109 deserves a thread on it's own, if not the whole sub-forum 



> Battle of Britain
> Spitfire I Merlin III with 100 octane, power = 1030hp or 1310hp 9,000 ft (2,700 m) for 5 minutes using 12psi boost.
> Spitfire II with Merlin XII power = 1150hp, this engine was able to use constant 12psi boost (1310hp+) and was free of the 5 minute restriction. Also used in BoB.



Covered by SR6. I'll add that we also need to state the rated height (or FTH) of contemporary engines - and it was above 16000 ft where Merlin III was doing it's 1030 HP (30 minutes limit?). Merlin XII even managed a bit a higher FTH, the power was some 10% greater above 10000 ft than Merlin III. The DB-601 was with FTH at 4 or 4.5 km (~13120 or 14700 ft), depending whether a new or old supercharger was installed. 



> Me 109E3 with DB601A1 = 990ps, *1100 for 5 minutes. (note it's an A1 not just an A)*
> Me 109E4 with DB601Aa = 990ps, 1045 for 5 minutes, 1170ps for 1 minute. Doubtful if the 1 minute rating was of use.
> Figures for the German engine are in metric horsepower so deduct 1.6%. In detail:
> 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.
> 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.



Will you please be so kind to double-check the bolded part, or to give some source that can confirm that? The 1 minute rating was for take off, and as such is/was stated in contemporary documents.



> The DB 601N, 1.35 ata for five min and 1175 PS. Rated altitude being 4800m. (there was a second type of 601N, mounted in one in the 109F had better supercharger and IIRC 5200 m rated altitude) and 1260hp, which latter was also cleared for 1.42 ata along with the DB601E presumably giving Me 109F1/F2 the same performance as Me 109F4.



The DB-601N is one of most mysterious German engines. This excerpts from the manual for the Bf-109F1/F2 states that, by my currently best (  ) translation, that 'regular' _Steig- Kampfleistung_ was using 1.3 ata and 2400 rpm, and 1.42 and 2600 rpm was used for _Start- Notleistung_, that is limited to 3 minutes. Some engines were rated just for 1.25 ata for _Kampfleistung_, and 1.35 ata for _Startleistung_, and that means power down for 4.5% and 6% respectively. Hopefully someone with a better grasp of German language (and the awkward of the neo-gothic) will help us here 
The German documents do state that a new type of supercharger is in use in the engines for the Bf-109F - that change allowed for 1.42 ata at same 4800 m? The Bf-109F topped in high speed at 5200 m, ie. the engine is using max possible amount of ram air.
A change from 1.30 ata (=1175 PS) to 1.42 ata is indeed making some ~1250 PS (6%)? A further thing in the DB-601N (in Bf-109F only?) was the clearance for 2800 rpm, allowed above FTH. That gave another healthy boost of power above 5 km - speed increse of 10 to 15 km/h at FTH. 
(please open the pics separately; chart for the 601N kindly provided by krieghund; 'Ausgezogene' - full line; 'Gestrichelt' - dashed line)



















> 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 a question whether the new s/c was fitted to the Aa as well.)



The power chart for the DB-601Aa, again kindly provided by krieghund. My guess is that the new S/C was fitted to the 601Aa - it made more power at all altitudes than the 601A with old S/C.








> It should be noted that the DB601 didn't need a high pressure supercharging so much since it's bolt-less head design offered much higher swept volume, greater valve area while the higher compression ratio improved efficiency and power. Really one needs to look at a power versus altitude chart with the DB601 over layed to the Merlin since the altitude curves are radically different. Really, we don't know much about use of GM-1 operationally.



I'm not sure that bolt-less head design was to be credited for those benefits. Many countries were into big V-12s, much before DB-60? appeared. High compression ratio is a trade off.



> I'm not pushing the 1.98ATA band wagon apart from saying it was certainly used in the closing months of the war in 1945. An Me with the DB605L was tested at 1.75ATA but would have been interesting at 1.98ATA given the higher altitude, if it were possible that is given the higher temperatures resulting from higher pressure ratios. The 1800/1850 hp the DB601DB/DC achieved eliminated the gap to the Merlin except in the event that 100/150 fuel was available to the Merlin.



The DB-605L, in case it was to be running on ~2 ata, would do so at lower altitudes than it was the case for 1.75 ata. The DB-605DC was making 1.98 ata at 4.9 km, but 'only' 1.8 ata at 6 km (no ram).


----------



## wiking85 (Jun 7, 2014)

Koopernic said:


> But, getting back on topic, it seems to me that 4 conventional engines either DB605 or Jumo 211, fitted to the Ju 288 or Fw 191 would have produced a rather excellent fast bomber able to rapidly take advantage of advances in these fighter engines development. No one tried a medium weight bomber with 4 engines. The only loss would be steep diving bombing, not really needed post 1942 with computing bomb sights.


Why adapt those airframes when you could just do the four Jumo 211s or DB601/5s on a He177B? It would be ready by 1942 unlike either of the above. In fact the Bomber B adaptations would only be ready for flight testing in 1942 and wouldn't be production ready until late 1943 and operational until 1944. So that's a moot point. Much better just to go with the He177B with four DB601/5s or Jumos.

There was this later on though:
Focke-Wulf Fw 191 Luft '46 Prototypes Entry


> One final attempt was made to save the Fw 191 program, this time the Fw 191C was proposed as a four engined aircraft, using either the 1340 horsepower Jumo 211F, the 1300 horsepower DB 601E, the 1475 horsepower DB 605A or the 1475 horsepower DB 628 engines. Also, the cabin would be unpressurized and the guns manually operated; a rear step in the bottom of the deepened fuselage being provided for the gunner.


----------



## Koopernic (Jun 8, 2014)

Shortround6,

I agree fully with your well presented post. One needs to consider that Daimler Benz was probably driven by a few imperatives different to Rolls Royce. One was the severe limitation Germany had in producing 100 octane fuel in quantity and the other the need to keep fuel economy high for its main customers the Me 109G and Me 110G both of which had little hope of improvements in internal fuel volume. To me the 'large capacity' using a bolt-less head seems more appropriate.

What I find interesting is if we look at the situation at the close of 1944:

DB 605 DB/DC performance:
With C3 fuel 1800hp at sea level
With B4 +MW50 1850hp at sea level
Full throttle height is about 6000m.
With C3+MW50 power is 2000hp at sea level and full throttle height about 4900 meters.

The Merlin 66 with 110/150PN fuel at 25psig is producing
1860hp at sea level
2000hp at rated altitude.

I would regard 150PN fuel equal to the 96/130 C3 fuel +MW50 the DB605 used.

The Packard Merlin V-1650-9 with 150PN fuel plus ADI (water ethanol injection) could manage about 2200-2300hp but I would imagine the DB605 could manage this as well i given the fuel, there was supposedly a German 140PN fuel being developed and DB605 was benching 2.3 ata. (I have no proof only other posters claims) and of course there was a DB605L with two stage supercharger, for which only 1.75 ata rating data is usually provided, which no doubt could have generated the pressures required. The sloweness of getting two stage supechargers in service is probably explained by the Germans developing highly sophisticated types such as the DB605 based DB628 that proved to hard to put into production with the available airframes.

The point I wish to make is this. The DB605 engine and the Merlin ended up with the same power levels 1944/45, however for much of the war the DB was severely lagging the Merlin. Inferior Fuel explains some of this but it seems not all.

I do think the narrative in which the Spitfire is superior because it "out turns" the Me 109 would be different, even reversed, if these aircraft were equally matched in power.

Despite that, the evolution of the Jumo 211 shows a different possibility. This engine was closer to the configuration of the Merlin, Griffon, Allison in using a lower compression ratio and higher boost and perhaps beat even the Merlin 61 into service with an inter-cooler in 1942 when the Jumo 211J came into service on Ju 88A4.

It might even have made a better fighter engine in 1942 given the power of 1420hp on only B4 fuel (1500hp for the Jumo 211P on only B4 though it was not produced in numbers). It's curious to imagine this inter-cooled engine receiving two stage supercharger given the inter-cooler and two speed gearbox is already present and perhaps C3 fuel.

Something went wrong between 1942 to 1944 with German fighter engine performance particularly the DB, some item of technology was missing.

(Tomo, thanks for the data, one day I mean to overlay DB and RR power v altitude on dated charts. The bolt-less integral head design seems authentically DB technology, remeber Rolls Royce messed up the head design of the Merlin originally. I know that Hispano Suiza used a similar idea on the HS-12 series and this technology ended up in Soviet production in the form of the Mikulin engines but the HS-12 series was way down on DB601 performance, it was this rather than airframe issues that nobbled the Morane-Saulnier M.S.406 though the Dewoitine D.520 had hideous handling with a viscous completely unannounced stall)


----------



## Aozora (Jun 8, 2014)

Koopernic said:


> Shortround6,
> 
> I agree fully with your well presented post. One needs to consider that Daimler Benz was probably driven by a few imperatives different to Rolls Royce. One was the severe limitation Germany had in producing 100 octane fuel in quantity and the other the need to keep fuel economy high for its main customers the Me 109G and Me 110G both of which had little hope of improvements in internal fuel volume. To me the 'large capacity' using a bolt-less head seems more appropriate.
> 
> ...



While the Allies were using 100/150 grade fuel en masse from June 1944 the DB 605DC only ever used C3 + MW 50 on an experimental basis in one gruppe, II./JG 11, late 1944-early 1945, after which the use of 1.98 ata + MW 50 was banned until problems with the DC were solved (II./JG 11 was disbanded soon after testing stopped); there is no viable evidence that this combination was used operationally by 109G-10s or K-4s by wars end - best of intentions aside,and a single document stating that a small number western based Jagdgruppen were supposed to start using C3 + MW 50 1.98 ata from 27 March 1945 notwithstanding. AFAIK the BMW 801 engined Fw 190s had priority when it came to supply of C3 fuel.


----------



## Koopernic (Jun 8, 2014)

The DB605DB/DC was cleared for 1.8 atmosphere's boost using B4(87 octane) +MW50 and achieved 1850hp at sea level, about the same incidentally as the Merlin 66 using 150PN fuel at sea level whose 2000hp MF gear WEP rating was only at about 2000ft and somewhat less at sea level. That's quite an achievement of the DB considering the low grade of the fuel and no doubt of enormous value in terms of supply logistics.

All of the engines certainly operated securely at 1.75 ata and up to 1800hp.

1.98 ata was clearly worked at Daimler Benz, was tried at the Luftwaffe's Rechlin Center, was tried at a Gruppen level, withdrawn in some cases reset down to 1.9 ata and then rescheduled to Gruppen that had C3 issued. It's highly plausible, I would say likely, that the engine was suitable for use this way given there was still nearly two months of war left and that was the intention.

I was clearly a ignition/detonation issue as the use of retarded ignition on the 1.9 ata units shows. In other words the use of 104/150PN or some other better fuel would have allowed the DB605D"x" to produce the same power as the Merlin. Given the allied oil bombing campaign and the damage it caused to the synthetic fuel industry its unlikely such a fuel could be manufactured. There was a great deal of research in this area including production of triptane (lean PN rating 160) use of analine etc. The solution seems to have been the use of the Beru F280 E43 spark plug though there may have been an attempt to tweak C3 fuel formulation, the characteristics of this fuel being rather difficult to manage at this time.

But I digress, the point is the difference between the DB605 on 1.8 ata with B4+MW50 at 1850hp versus the Merlin at 2000hp on 150PN is only 7.5% and then only at the Merlins 2000ft MF gear peak.

This gap is minimal and the smallest the gap ever was since the BoB.


----------



## Shortround6 (Jun 8, 2014)

The Allison, Merlin, DB 601 and Jumo 211 all started out fairly close to each other in power, weight and physical size. 

The Hispano (and Russian M100 series) were roughly of a size (outside dimensions) but down on power even if a bit lighter. 

It is power to weight that was much more important to aircraft performance than displacement. The next thing is that once a company or country is tooled up and producing an engine at hundreds per month (or thousands) it is more than just a bit difficult to switch horses in midstream. Unless the engine is an unmitigated disaster, every attempt will be made to extend it's life with a series of modifications rather than start over and loose the tooling/production knowledge. 

Strangely enough the engines didn't finish that far apart in weight either. The Allison and Merlin both gained two stage superchargers that added several hundred pounds but then the DB 605 gained around 100 kg over the early 601s and the Jumo 211 porked up a bit even before trying for the 213 version. 
Different materials and manufacturing techniques allowed more power with the same or better engine life in many later models compared to the late 1930s versions of the engines. The trick is rarely making large power for a few minutes, it is making large power for extended periods of time and still having a serviceable engine. For instance the Allison went through 4 different crankshaft versions ( at least) with the first 3 being identical to the eye in dimensions and weight. They started with a "plain" version, went to a shot peened model that could handle about 28% higher stress loads and then went to a nitrited model that could handle 33% more stress than the shot peened crank (and 71% more than the plain crank). They finished with a new crank with 26-27lb more counterweights but using the same size bearings/journals that can be dropped into early crankcases. 
New casting techniques allowed for stronger engineblocks/crankcases that weighed just a bit less and had a lower scrap rate. 
The Merlin and German engines are not quite as well documented as the Allison in regards to these internal modifications that allow the engine to survive at the higher powers.


----------



## wuzak (Jun 8, 2014)

Koopernic said:


> I do think the narrative in which the Spitfire is superior because it "out turns" the Me 109 would be different, even reversed, if these aircraft were equally matched in power.



The Spitfire out turns the Bf 109 whether it has more power, equal power, or less power. It is a function of the bigger wing.

Increased power would improve the Bf 109's straightline speed, climb and acceleration. 

The small wing is part of the reason why the Bf 109 could be so fast on low power.




Koopernic said:


> The bolt-less integral head design seems authentically DB technology, remeber Rolls Royce messed up the head design of the Merlin originally. I know that Hispano Suiza used a similar idea on the HS-12 series and this technology ended up in Soviet production in the form of the Mikulin engines but the HS-12 series was way down on DB601 performance, it was this rather than airframe issues that nobbled the Morane-Saulnier M.S.406 though the Dewoitine D.520 had hideous handling with a viscous completely unannounced stall)



The "ramp head" design was based on that which was used in their latest car engine. It showed well in single cylinder testing, but that did not translate to the full V-12.


----------



## wuzak (Jun 8, 2014)

Koopernic said:


> The DB605DB/DC was cleared for 1.8 atmosphere's boost using B4(87 octane) +MW50 and achieved 1850hp at sea level, about the same incidentally as the Merlin 66 using 150PN fuel at sea level whose 2000hp MF gear WEP rating was only at about 2000ft and somewhat less at sea level. That's quite an achievement of the DB considering the low grade of the fuel and no doubt of enormous value in terms of supply logistics.



According to Lumsden, Merlin 66 with PN100/150:
2000hp, 3000rpm, +25psi @ 5,250ft
1860hp, 3000rpm, +25psi @ 11,000ft

Merlin 66 with PN100/130:
1750hp, 3000rpm, +18psi @ 5,250ft
1625hp, 3000rpm, +19psi @ 12,500ft


----------



## wiking85 (Jun 9, 2014)

Given the discussion on the efficacy of the DB601/5 vs. the Merlin, and seeing how the Merlin provided to be a successful bomber engine, how would the DB 600 series have done as a bomber engine for a four engine bomber?


----------



## Shortround6 (Jun 9, 2014)

It depends on which engine and when and what you want the bomber to do. 

Comparing a 20 series Merlin and a DB 605 _without_ big supercharger or power boosting systems the DB gives perhaps 10% better fuel economy, which for a plane with 2500-3000 US gallons of fuel means either longer range/a bit higher cruise speed/ or a 1500-1800lb greater bomb load. Pick *one.* Of course a Merlin 20 series is about 145lbs lighter per engine so the difference is more like 630-930lbs. 

The engines don't match power exactly but you can forget the over 1500hp power ratings of the later DB 605s for bomber use. Of course you can pretty much forget the over 18lb boost ratings for the 20 series too for 4 engine bomber use. 
4 engine bombers often took 20-30 minutes to take-off and climb to operating altitudes. the 30-60min rating is much more important than the 1-5minute _sprint_ rating. Take-off rating is important too and it should be a _normal_ take-off rating for most purposes, not WEP or water injection ratings except for special missions. Increasing the maintenance man hours per mission is not a goal when in the planning stages. Once squadrons are equipped and operational you sometimes have to do what you have to do but planning ahead of time to use WEP/water injection take-offs during most of WW II wasn't a good idea. ( they got better at it as the war went on and post war commercial planes used it).

There doesn't seem to a be any reason why the DB 600 series wouldn't have worked on a 4 engine bomber. Both engines had advantages and disadvantages and the differences changed (either increased or decreased) depending on exact model available and fuel available. 

The bomber has to match the engines to some extent, sticking two stage Merlins on the Short Sterling wasn't going to get you a high performance/high altitude bomber because of the fuselage (huge) and wing, for example.


----------



## wiking85 (Jun 9, 2014)

How about the DB605A of 1942 on the He177B? Despite being restricted in RPMs until 1943, it was about 200kg lighter as an engine than the DB603 the He177B was tested with in 1943.


----------



## Shortround6 (Jun 9, 2014)

What is the power of the two engines?

DB 605A had 1475PS for take-off and 1310PS for climb at sea level rising to just under 1400ps at just over 2000 meters and then falling to about 1250PS at 5700 meters. Max cruise is 1075 PS at 5500meters?

The DB 603 had 1750PS for take-off (at 1.4 ata, no special fuel, no MW 50) and 1580PS for climb at sea level (1.3 ata)with 1510PS at 5700 meters (?). Max cruise is 1400 PS at 5360-5400meters?

DB 603 has a max cruise higher than the "Höchtsleistung" rating of the DB 605A at about the same altitude. While the engine is lighter (and so is the cooling system and the propeller needed and the ....etc. etc) you are dealing with a 70-90,000lb bomber when fully loaded. Why the HE177B/HE277 gained 20,000lb loaded (and around 10,000lb empty) over the He 177 I don't know but using around 84% of the take-off power isn't going to give good results. 

You might be able to make a rather more reliable bomber than the He 177 but it is going to have a bit less performance in one or more areas due to the higher drag. Perhaps only 3-5% ???


----------



## wiking85 (Jun 9, 2014)

Shortround6 said:


> What is the power of the two engines?
> 
> DB 605A had 1475PS for take-off and 1310PS for climb at sea level rising to just under 1400ps at just over 2000 meters and then falling to about 1250PS at 5700 meters. Max cruise is 1075 PS at 5500meters?
> 
> ...



The 277 and 177B are different aircraft in that the 277 is wider with a bigger bomb bay and has more fuel capacity. The 177B will be about the same weight at the 177A, perhaps with some extra weight from the larger wings and extra nacelles, but less from smaller nacelles, lighter engines, and smaller props. So 2-3,000kg extra? IIRC about 3-4% extra drag. I get why the DB603 was used, but it was not available in numbers and was less reliable.


----------



## Koopernic (Jun 9, 2014)

ktank said:


> "We can also note that German V-12s will get better fuel mileage than Allied V-12s."
> 
> Any details on this? I would have thought the higher-octane fuel of the Allies on its own would have given the Allies lower specific fuel consumption.
> 
> Note that the DB605, in performance equivalent to a Merlin, was nearly the displacement of the Griffon.




However only thing that matters is the weight and frontal area and in terms of weight the DB605A, DB605D and DB605L (two stage) were exactly equal to the Merlin 66 with both equal to 745kg +/-1kg. The Daimler Benz engine in fact had lower frontal area. The Merlin (and Griffon) may, I suspect, even have had a requirement for larger radiators given the inter-coolers requirements. The DB60x series used the threaded cylinder sleeve as a kind of giant hollow nut which was screwed into the integral cylinder head block combo and secured to the crankcase by a large nut (technically a threaded ring). The Merlin (and Jumo and Allison) engines had 4 bolt holes surrounding each cylinder which was used to tighten on the block to the crankcase. The need for sufficient structural material and clearances around these holes and the more peaky stresses forced the Merlin to used smaller cylinders and conversely allowed larger ones on the DB. Perhaps DB then designed for lower pressures. There is more than one way to skin a cat as they say.

Likewise the Griffon (34L) is about the same weight as the DB603(44L). The RR engines relied on processing more air not through higher swept volumes but through supercharging and then inter-cooling to get rid of the heat that would cause preignition and thereby sacrificing some efficiency and power by low compression ratios, losses in supercharging compression, losses in the heat extracted in the inter-cooler which would have been partially compensated for by the lower frictional losses in the smaller engine.

Daimler Benz did start introducing inter-cooling on the larger DB603L and were expecting a spectacular 2800hp out of the DB603N.
A DB605 variant, the DB628 which had separate drives for the 1st stage variable pitch LP supercharger and 2nd stage HP supercharger (infinitely variable drive type) had inter-cooling AFAIKT from photos and a spectacular full throttle height of 38500ft.


----------



## wuzak (Jun 9, 2014)

What is the frontal area of a DB 605 compared to an Allison or Merlin? Or Griffon?

The Merlin (most of) has a higher frontal area than the Allison due largely to the updraught carburettor. The 130 series Merlins had a lower frontal area than other Merlins because it used a downdraught carby.

The Griffon was 37l (36.7l actually). The two stage Griffon was about the same weight as the single stage DB 603. But more powerful, and nowhere near as long.

Similarly the single stage DB 605 was about the same weight as the two stage Merlin.


----------



## Koopernic (Jun 9, 2014)

wiking85 said:


> How about the DB605A of 1942 on the He177B? Despite being restricted in RPMs until 1943, it was about 200kg lighter as an engine than the DB603 the He177B was tested with in 1943.
> 
> View attachment 264655








He 177A5 prototypes with 4 engines (BMW 801) were in fact flown in 1942. AFAIKT the only issues were that the 4 engines really required a larger tail area or contra rotation. Now the He 177A1 and 177A3 actually had 2 x DB606 and since these were paired engines it really means they had 4 x DB601E. Had the engines been mounted separately they could by 1942 have had a choice of 4 x DB605A, 4 x Jumo 211J, 4 x BMW 801 even 4 x DB603 all significantly more powerful than 4 x DB601E. Any drag increase is greatly over compensated for by the more powerful engines, any increase in fuel consumption is compensated for by the higher maximum takeoff weight enabled by the greater power. By late 43 or early 44 they can add in the Jumo 213A as an option or the enlarged supercharger variant the DB605AS or start using limited form of the MW50 boost systems for enhanced takeoff power eg 1.55 ata rating.

As it turns out the He 177A5 series was introduced in 1943 with a new, larger re-engineered wing. The first 200 or so still received only the 2 x DB606 (4 x DB601E) that had been used in the He 177A1 while the latter production batch received 2 x DB610 (4 x DB605A) the reason being the Luftwaffe didn't have the Stomach to introduce another new engine type too early. The next development was supposed to be the He 177A7 which had yet again an enlarged new wing with larger coupled engines again 2 x DB613 (4 x DB603 engines) however the new wing (3rd new wing) had been designed to handle either 2 large engines or 4 smaller separate engines in the manner of the Airbus A330/A340 and by this time the Luftwaffe was sick of the coupled engines. When configured with 4 separate engines a He 177A7 was known as a He 277B7.

You'll note the RLM (maybe not the Luftwaffe fault) persisted with the coupled engines to the point that it looks insane from our perspective, even re-engineering the wing totally several times, that effort could have been used to distribute the engines separately and introduce the 4 engined variant after the He 177A3 in 1943.

In regards to the Fw 191C (4 engined version) as far as I can tell Bomber B was supposed to enter production in late 1941 or early 1942 and if a backup plan in case of failure of the Jumo 222/DB604/BMW 802 to meet development schedule had of been in place production Bomber B could have been in production in 1942 using 4 separate engines. The difference is that the Bomber B was significantly smaller than Bomber A (He 177) and would have had speeds of around 380-440 mph. The internal bomb load of 4 tons (as opposed to 6-8 tons for He 177) however was still big, Bomber B was classified a heavy bomber. That is the kind of performance the Luftwaffe needed in the face of its numerical inferiority.

When He 177 started flying around the Atlantic and Mediterranean in 1943 with glide bombs (see Martin Bollingers book on the guided weapons) their great range and speed meant they often turned up the next day on missions thousands of miles away, becoming a threat over a large area. Had they been available in large numbers as reliable 4 engines aircraft they would have forced the allies to deploy more defensive resources while being very efficient from the Luftwaffe's point of view. The Bomber B also had this capability only they could have blunted the effectiveness of allied fighter superiority.

Note the suggestion of DB628 (a DB605 variant) use on the Fw 191C, this engine produced around 1100hp at 38500ft and this suggests penetration speeds of well over 400mph at well over 40000ft with service ceilings of 45000ft or more.

Junkers I think actually did rather well with the Jumo 222 since a new engine took at least 6 years to get into production, developing full power, reliable and in service. Doing it in 4 years was never going to work. Compare CW R-3350 (1937 first run) and Napier Sabre which started earlier.

By the end of the war the Jumo 222E/F with two stage supercharger on B4+MW50 was producing 2800hp and likewise the single stage Jumo 222A-3/B-3. The engine was scheduled for production but the bar had been raised yet again to 3000hp.

Reactions: Like Like:
1 | Like List reactions


----------



## tomo pauk (Jun 10, 2014)

Koopernic said:


> ...
> The Packard Merlin V-1650-9 with 150PN fuel plus ADI (water ethanol injection) could manage about 2200-2300hp but I would imagine the DB605 could manage this as well i given the fuel, there was supposedly a German 140PN fuel being developed and DB605 was benching 2.3 ata. (I have no proof only other posters claims) and of course there was a DB605L with two stage supercharger, for which only 1.75 ata rating data is usually provided, which no doubt could have generated the pressures required. The sloweness of getting two stage supechargers in service is probably explained by the Germans developing highly sophisticated types such as the DB605 based DB628 that proved to hard to put into production with the available airframes.



We might compare the number of designs under development in the Daimler-Benz, with number of designs in other companies. The plethora of the types simply deluted the scarce resources. It is interesting that Germans (at least DLV) were perfectly aware of advantages of two-stage supercharging even before the ww2 broke out, yet they did not have anything such to install in the airframes before 1945. Even the Soviets were test flying the 2-stage versions of the M-105 in early ww2.
The DB-628 was a 2-stage engine, we do not know for certain that it would've been such an issue to install it in the Fw-190, for example. 



> Despite that, the evolution of the Jumo 211 shows a different possibility. This engine was closer to the configuration of the Merlin, Griffon, Allison in using a lower compression ratio and higher boost and perhaps beat even the Merlin 61 into service with an inter-cooler in 1942 when the Jumo 211J came into service on Ju 88A4



The Jumo 211F J were indeed using the lower compression ration (6.5:1, a bit lower than V-1710), yet the allowed boost was still only 1.40 ata, even for the 5 minute take-off power setting. It cannot beat the Merlin 61 at any altitude, the power for the inter-cooled sub type (211J) was 1180 PS at 4800 m (1164 HP at 15750 ft), on 2400 rpm and 1.20 ata (30 min rating). Maybe as a result of the Jumo 211 being the 'bomber engine', the engine was never rated for 'Notleistung' (5 min rating, 2600 rpm and 1.40 ata). The power was comparable with Merlin 20 series, apart for the Merlin's advantage for being also rated for 5 min power (circa 1400 HP at 12000 ft); also 1100+ HP at 17000 ft for 'max climbing power' at moderate boost and RPM - +9lbs and 2850. 
No second stage equals low power at higher altitudes, irrespective to the country boundaries.



> It might even have made a better fighter engine in 1942 given the power of 1420hp on only B4 fuel (1500hp for the Jumo 211P on only B4 though it was not produced in numbers). It's curious to imagine this inter-cooled engine receiving two stage supercharger given the inter-cooler and two speed gearbox is already present and perhaps C3 fuel.



Against the DB-601E and 605A (even de-rated), the chances are slim. It 1st need to be tested and rated for 2600 rpm beyond tale-off regime. It (maybe?) need to be modified for the prop gun, so the Bf-109 can use it. It is a wider engine than DB-60?. With two stage S/C, now that would be an engine.



> Something went wrong between 1942 to 1944 with German fighter engine performance particularly the DB, some item of technology was missing.



Too many products went nowhere, while consuming resources and time. 



> (Tomo, thanks for the data, one day I mean to overlay DB and RR power v altitude on dated charts. The bolt-less integral head design seems authentically DB technology, remeber Rolls Royce messed up the head design of the Merlin originally. I know that Hispano Suiza used a similar idea on the HS-12 series and this technology ended up in Soviet production in the form of the Mikulin engines but the HS-12 series was way down on DB601 performance, it was this rather than airframe issues that nobbled the Morane-Saulnier M.S.406 though the Dewoitine D.520 had hideous handling with a viscous completely unannounced stall)



The Hispano 12 was too light, compared with DB or Jumo, with 2 valves per cylinder. So the allowable RPM and boost were low, and that means power is lacking. The Soviets bulked up the Klimov versions several times, so the M-105 turned 2600 rpm vs. 2400 of the French 12Y. That improved power at all altitudes. Soviets also installed 2-speed S/C drive, that gave 'altitude flexibility' to the power. Further weight increase allowed greater boost, 1st with VK-105PF, then with 105PF2 versions. The VK-106, 107 and 108 were to be further bulked up, with 4 valve head and up to 3200 rpm (!). The weight cost was to be above 200 kg against the M-105.

The Jumo 222, at least going by the article about it in the 'Flugmotoren und strahltriebwerke' was a huge resource hog, that was not helped with RLM upping the bar every now and then. It was also not helped by numerous relocations of test and perceived production facilities. Despite passing of bench tests, the flight tests were many times interrupted by malfunctions of numerous main components. Corrosion, vibrations, crankshaft troubles, S/C malfunctions - the 222 have had it all.


----------



## wuzak (Jun 10, 2014)

tomo pauk said:


> It is interesting that Germans (at least DLV) were perfectly aware of advantages of two-stage supercharging even before the ww2 broke out, yet they did not have anything such to install in the airframes before 1945.



Daimler-Benz built the Mercedes-Benz W154 in 1938. It had a 3l V-12 with twin Rootes type superchargers - these were two parallel, single stage superchargers. For 1939 the engine was redesigned as the M163 with twin stage supercharging.


----------



## Koopernic (Jun 10, 2014)

The idea that the Germans are dissipating their resources in a plethora of R+D programs while the allies are highly focused doesn't bear scrutiny.

Rolls Royce piston engines in development between 1940 to 1945
Rolls-Royce Merlin single stage, two stage and turbo
Rolls-Royce Griffon
Rolls-Royce Eagle (1944)
Rolls-Royce Exe
Rolls-Royce Peregrine
Rolls-Royce Crecy
Rolls-Royce Vulture
Rolls-Royce Pennine

Some of these engines are highly unconventional, bordering on crazy with sleeve valves or two stroke cycles requiring technology that didn't exist or seemingly provoked by competition from Napier. Only a few were cancelled, such as the Peregrine.

Less is known about Bristol R+D effort except that the Centaurus did not see service until after the war (unless one counts the oversize Wellington-the Warwick) and did nothing that the PW R-2800 or CW R-3350 could not do better and earlier. The British and US duplicated effort in many areas for reasons of national pride, post war strategy or to develop some unique aspect of technology.

Napier expended a great deal of effort on the Nomad turbocompund diesel that went nowhere.

This is the sample of the US effort.
Pratt Whitney X-1800
Pratt Whitney XH-3130
Wright R-2160 Tornado
Wright R-3350
Chrysler IV-2220
PW R-4360 (did not see combat service in WW2)
Turbo compound Allison V-1710
Lycoming XR-7755 edited in.

Only the R-3350 and R-4360 became a useful engine and then barely.

While fascinating engines they represented huge R+D programs that failed to produce useful engines in time while their economic viability was dubious as well.

As far as your notations on the inferiority of the Jumo 211F/J you overlooked that the engine was operating on 87 octane rather than 100 and latter 100/130. The 6psig the early 87 octane Merlin operated at is essentially 1.4 ata. To get to 12psig (about 1.8 ata) the Merlin needed 100 octane and to get above that level, the 15psig (2.1 ata), 18psig (2.3ata) it needed 102/130 or 102/150 and 25psig it needed 104/150

Most of the duplicated engines of the German programs are derivatives eg DB628 (DB605 based), DB627(DB603 based) and so not really duplications but programs adding sophisticated supercharging or turbo charging. The DB605 and hence DB628 was simply going to be too small, just like the Merlin was getting too small, by 1945 hence it would have made sense to focus on the larger 627 instead. 

The DB605D with enlarged supercharger first ran in 1942 so its surprising an enlarged supercharger took 2 years to enter service.

The 628 might have made sense on a 4 engined bomber if ready early enough but even if fitted to the Me 109 wouldn't the 109 require too many airframe modifications. These two stage supercharged engines had independent drives, variable pitch fans and variable speed drive on the second stage and were much more effective than more conventional two stage engines.

Abandoning most piston engine programs made sense after 1944. Only Jets now made sense, even for long range aircraft that were to target the US east coast, while the existing Jumo 213/DB603/BMW801 were more than capable of performing any remaining job; up to 2800hp, with minor modifications.

Jumo 222 didn't seem to have any problems other engines didn't have. It was pushed into production after only 4 years development when 6 were needed by all other WW2 engines. The RLM or Luftwaffe might have accepted the engine into service in derated form but apparently that wasn't an option due to airframe weight growth.


----------



## wiking85 (Jun 10, 2014)

The Jumo 222 started development in 1937 and wasn't ready until 1943 then only with unacceptable amounts of heat resistant metals Germany didn't have. That's 7 years of development to get to production ready status and it never entered production even after being declared 'ready'.


----------



## wuzak (Jun 10, 2014)

Koopernic said:


> The idea that the Germans are dissipating their resources in a plethora of R+D programs while the allies are highly focused doesn't bear scrutiny.
> 
> Rolls Royce piston engines in development between 1940 to 1945
> Rolls-Royce Merlin single stage, two stage and turbo no turbo as far as I am aware
> ...



Basically the main part of the war Rolls-Royce concentrated on the Merlin and Griffon, and moreso on the Merlin.




Koopernic said:


> Some of these engines are highly unconventional, bordering on crazy with sleeve valves or two stroke cycles requiring technology that didn't exist or seemingly provoked by competition from Napier. Only a few were cancelled, such as the Peregrine.



The Crecy was based on designs from Ricardo. It was unconventional, but it was a promising research project.

Rolls-Royce's first sleeve valve engines were modified Kestrels (modified by Ricardo). These were the RR/D (Diesel) and RR/P (petrol). The Exe was designed and built in the '30s, but never had any serious amount of resources directed to it. The Pennine was an enlarged version, started late in the war.

The Vulture was an X engine. Not exactly crazy, or unique.

The Eagle was, indeed, a response to Napier's Sabre. But it, too, was a late war design.





Koopernic said:


> Less is known about Bristol R+D effort except that the Centaurus did not see service until after the war (unless one counts the oversize Wellington-the Warwick) and did nothing that the PW R-2800 or CW R-3350 could not do better and earlier. The British and US duplicated effort in many areas for reasons of national pride, post war strategy or to develop some unique aspect of technology.



The reason why the Centaurus did not see service untillate in WW2 is that practically all the resources at the disposal of Bristol went to sorting and improving the Hercules.




Koopernic said:


> Napier expended a great deal of effort on the Nomad turbocompund diesel that went nowhere.



Most of that effort was post WW2.




Koopernic said:


> This is the sample of the US effort.
> Pratt Whitney X-1800
> Pratt Whitney XH-3130
> Wright R-2160 Tornado
> ...



These are projects from several different companies. And the US war economy was far more capable of supporting them than the German one was.




Koopernic said:


> Only the R-3350 and R-4360 became a useful engine and then barely.



You will get arguments on the usefulness of these engines. The R-3350 did make a significant contribution - in the B-29.




Koopernic said:


> As far as your notations on the inferiority of the Jumo 211F/J you overlooked that the engine was operating on 87 octane rather than 100 and latter 100/130. The 6psig the early 87 octane Merlin operated at is essentially 1.4 ata. To get to 12psig (about 1.8 ata) the Merlin needed 100 octane and to get above that level, the 15psig (2.1 ata), 18psig (2.3ata) it needed 102/130 or 102/150 and 25psig it needed 104/150



As I understand it, B4 was better than the pre-war British 87 octane, and more akin to the 100 ocatne being used at the start of the war.

Of course the option for the Merlin would have been, as the Germans did, to use ADI to compensate for lack of octane.




Koopernic said:


> Most of the duplicated engines of the German programs are derivatives eg DB628 (DB605 based), DB627(DB603 based) and so not really duplications but programs adding sophisticated supercharging or turbo charging. The DB605 and hence DB628 was simply going to be too small, just like the Merlin was getting too small, by 1945 hence it would have made sense to focus on the larger 627 instead.



Interesting that you say that most of German engine projects were derivatives of exiting engines, but then call out the variants on the Merlin (single stage, two speed and two stage). All of Allison's WW2 piston engine projects were based on the V-1710. Even the turbo-compound was additional components bolted up to the back of a standard 2 stage V-1710.

There were some German projects that went nowhere. The DB604, for example. An X-24, like the Vulture.
The DB609, a V-16. You could say this was based on the DB603 (it was, using the same bore and stroke dimensions) - but you could say the R-3350 was based on the R-2600 and the R-4360 was based on the R-2800.
BMW 802
BMW 803
Junkers 223 (IIRC a Diesel)

And a myriad of gas turbine projects.

As for being too small, the DB605 was of Griffon capacity, give or take a litre.



Koopernic said:


> The DB605D with enlarged supercharger first ran in 1942 so its surprising an enlarged supercharger took 2 years to enter service.



I guess it would be the same situation as for the Allies - production trumps development.




Koopernic said:


> The 628 might have made sense on a 4 engined bomber if ready early enough but even if fitted to the Me 109 wouldn't the 109 require too many airframe modifications. These two stage supercharged engines had independent drives, variable pitch fans and variable speed drive on the second stage and were much more effective than more conventional two stage engines.



The Bf 109 was too small. But it could have been used for a new development, or for a Fw 190 version.




Koopernic said:


> Abandoning most piston engine programs made sense after 1944. Only Jets now made sense, even for long range aircraft that were to target the US east coast, while the existing Jumo 213/DB603/BMW801 were more than capable of performing any remaining job; up to 2800hp, with minor modifications.



I think you will find that the modifications were anything but minor.




Koopernic said:


> Jumo 222 didn't seem to have any problems other engines didn't have. It was pushed into production after only 4 years development when 6 were needed by all other WW2 engines. The RLM or Luftwaffe might have accepted the engine into service in derated form but apparently that wasn't an option due to airframe weight growth.



I think that the DB 604 had, possibly, more potential. But it was cancelled after less work had been done it than the Jumo 222.

Reactions: Like Like:
1 | Like List reactions


----------



## Koopernic (Jun 10, 2014)

wiking85 said:


> The Jumo 222 started development in 1937 and wasn't ready until 1943 then only with unacceptable amounts of heat resistant metals Germany didn't have. That's 7 years of development to get to production ready status and it never entered production even after being declared 'ready'.



While the Jumo 222 development program started in 1937 the Wright R-3350 actually ran in 1937 and it still had problems in 1943 and then at only 2000/2200hp.

Jumo 222 did enter low rate production, approximately 289 were produced and Ju 288 did fly on it as did Fw 191. First run of the Jumo 222 was 1939. First run of the Sabre was 1938. First run of the R-3350 1937.

By demanding 2500hp on only 87 octane fuel rather than accepting 2000hp or even less, too much demand was placed on the engine too early. The engine was back on the production program in 1944.

The reason it didn't enter production was probably that its only customer was the Ju 288 and it wasn't powerful enough. Perhaps they might have tried it in de-rated form on the Do 217 or He 219 in 1942. If de-rated to 1900hp it still provides more power than a BMW801 or DB603 while having the same or better power to weight ratio.

One issue halting production was a lack of tin for the bearings.


----------



## Koopernic (Jun 10, 2014)

"As I understand it, B4 was better than the pre-war British 87 octane, and more akin to the 100 ocatne being used at the start of the war."

No, B4 was 87 octane as was British 87 octane. Both fuels, if tested, would slightly exceed their nominal 87 octane rating. RON is RON.
The reason is that the acceptance tests always added a safety margin.

There were slight differences in the test engine procedures. The Germans were more rigorous in their test by preheating the fuel to 150C rather than just using ambiant which leads to a slightly more conservative result however the Germans tested at 600RPM while the British at 800RPM which also leads to a more conservative result. In effect the tests are the same to within a point.

The result is that German B4 started out at 87 octane was often tested at 89 octane using the British methods but then RAF 87 octane was also slightly higher than the nominal 87 octane rating.

Most of the German engines projects were derivatives in that the basic DB605/603 were used as the basis 

Rolls-Royce Merlin XX Turbo-Supercharger Cutaway Drawing from Flightglobal 





List of aircraft engines of Germany during World War II - Wikipedia, the free encyclopedia


Daimler-Benz DB 600 12-cylinder inverted-V
Daimler-Benz DB 601 improved DB 600 with fuel injection
Daimler-Benz DB 602 16-cylinder diesel powered the two Hindenburg class airships
Daimler-Benz DB 603 enlarged DB601 for use in bombers and fighter-bombers, little fighter use
Daimler-Benz DB 604 prototype 24-cylinder (X-24) engine, cancelled in September 1942
Daimler-Benz DB 605 improved and slightly enlarged DB601 for use in fighters
Daimler-Benz DB 606 composed of twinned DB 601 engines, a coupled "power system", derided as a "welded-together engine" by Goering in August 1942
Daimler-Benz DB 607 a four-stroke diesel version of DB 603 engine.
Daimler-Benz DB 609 16-cylinder version of DB 603 engine. this was still not an entirely new development.
Daimler-Benz DB 610 composed of twinned DB 605 engines, a coupled "power system", to replace the DB 606
Daimler-Benz DB 612
Daimler-Benz DB 613 two coupled "power system" DB603 engines as with the 606 and 610, experimental only
Daimler-Benz DB 614 development of the DB 603G, 2000 hp. Abandoned June 1942
Daimler-Benz DB 615 consisted of two coupled DB 614 engines. 4000hp. Abandoned in June 1942.
Daimler-Benz DB 616 a development of the DB 605. Abandoned in June 1942.
Daimler-Benz DB 617 a development of the DB 603 for long-range flight.
Daimler-Benz DB 618 two coupled DB 617 engines.
Daimler-Benz DB 619
Daimler-Benz DB 620
Daimler-Benz DB 621 DB 605 with a two-stage supercharger. 1620 hp. Abandoned in September 1942
Daimler-Benz DB 622 DB 603 with a two-stage mechanical supercharger and a turbosupercharger. 1970 hp. Abandoned in January 1943
Daimler-Benz DB 623 DB 603G with twin turbo-superchargers. 2265 hp. Abandoned January 1943
Daimler-Benz DB 624 DB 603 with both a two-stage mechanical supercharger and a turbosupercharger. 1900 hp. Abandoned in April 1943
Daimler-Benz DB 625 DB 605D with turbo supercharger. 1755 hp. Abandoned
Daimler-Benz DB 626 DB 603G with twin turbosuperchargers and induction cooler. 2125 hp. Abandoned November 1942
Daimler-Benz DB 627 603 with a two-stage supercharger and after-cooler. Development abandoned in March 1944
Daimler-Benz DB 628 DB 605, fitted with a two-stage supercharger. Abandoned in March 1944
Daimler-Benz DB 629
 Daimler-Benz DB 630 36 cylinder Double W engine with a capacity of 89 litres and output in the 4,000 HP class (2,940 KW)
Daimler-Benz DB 631 DB 603G with a three-stage supercharger. 1900 hp. Abandoned
Daimler-Benz DB 632 DB 603N, with a drive for contra-rotating propellers two stage supercharger with intercooler, two mechanical speeds with infinetly variable drive.

The only engines which are truly new developments I have highlighted in blue text.

BMW 801 14-cylinder two-row radial, air-cooled — most-produced radial engine of the Third Reich
BMW 802 experimental, 18-cylinder two-row radial (same bore but longer stroke as 801) but abandoned.
BMW 803 experimental, 28-cylinder liquid-cooled four-row radial, originally Bramo/Siemens

For Junkers

Jumo 204 6-cylinder opposed liquid-cooled diesel;
Jumo 205 improved Jumo 204 of smaller size;
Jumo 207 improved 205 with a turbocharger;
Jumo 208 enlarged development of the 207;
 Jumo 210 inverted V-12;

Jumo 211 inverted V-12, mostly for bomber use, most produced German aviation engine of World War II;
Jumo 212 Two Jumo 211 "coupled" (geared together), same design as DB 610;
Jumo 213 improved Jumo 211, inverted V-12;
Jumo 222 experimental 24-cylinder supercharged liquid-cooled "star" (six banks of four cylinders) aircraft engine; nearly 300 examples built
Jumo 223 "box" engine made of four 207s;
Jumo 224 "box" engine made of four 20's.

The ones I have highlighted in blue are essentially prewar engines.

Most of the projects by Argus and Klockner go back pre war and were not perused through the war.


----------



## wuzak (Jun 11, 2014)

Koopernic said:


> Rolls-Royce Merlin XX Turbo-Supercharger Cutaway Drawing from Flightglobal
> View attachment 264736



Was there anything other than this drawing for Flight (ie not a RR drawing) to suggest that there was a turbo Merlin?


----------



## GregP (Jun 11, 2014)

I don't think anyone says the Allies didn't develop new prototypes ... rather they say the Germans developed many MORE prototypes with resources that were in shorter supply and were sorely needed on projects that could get into combat. 

The Allies DID develop prototypes, but also didn't pursue them to the point of neglecting the materiel needed to prosecute the war, and had more resources to spare since the prototypes usually consisted of very small teams that tried a few things and got back to work on the necessary engines.


----------



## Koopernic (Jun 11, 2014)

GregP said:


> I don't think anyone says the Allies didn't develop new prototypes ... rather they say the Germans developed many MORE prototypes with resources that were in shorter supply and were sorely needed on projects that could get into combat.
> 
> The Allies DID develop prototypes, but also didn't pursue them to the point of neglecting the materiel needed to prosecute the war, and had more resources to spare since the prototypes usually consisted of very small teams that tried a few things and got back to work on the necessary engines.



"rather they say the Germans developed many MORE prototypes with resources that were in shorter supply and were sorely needed on projects that could get into combat."

I just don't see that at all. The numbers to support that don't seem to be there.

They, the Germans, developed exactly what they had to and suspended anything that was diverting resources from the here and now after around 1941. They did that to a fault in fact, sacrificing long term developments quite frequently.

The prolific designations that are noted by Daimler Benz are almost all turbo/supercharger variations of the DB601/605/603 series or variations of such as pairing via a gearbox or simple modifications such as adding contra rotating gearbox. Few of these went past theoretical investigation. One can argue that the DB605 was hardly even a new engine: being essentially a bored out DB601 with heavier parts. A lots of these simply needed suffix designations rather than a type number.

The three engines that the Germans did build to the point of running and close to mass production were the DB604 (X24), BMW 802 (18 cylinder radial) and Jumo 222 (24 cyclinder star) of which the DB604 and BMW802 were abandoned, perhaps foolishly since they may have been less promising in frontal area and weight but more reliable.

The Jumo 213 was a logical progression Jumo 210->Jumo 211 ->Jumo 213 to meet greater needs.
You can see the same progression in the Rolls Royce Family eg Kestral, Merlin, Griffon, Perigin, R-type.

It would have been irresponsible to have neglected development of such engines.

The DB engines were a family based around an inverted V12 using the same technology, merely scaled. They weren't really developments of each other but hatched in parallel. The bigger engine, the DB603 is almost as old as the DB600 but they were less a progression than a planed family of engines.

The BMW 801 ->802 was a logical progression. The BMW803 was abandoned and received minimal resources. The DB603/5/1 series seems more coherent that the Rolls Royce program which used radically different configurations (X,V and H blocks) with different valves (sleeve, poppet and 2 stroke) wherease the German variations were often to do with supercharging, gearboxes to pair engines.

We do have some odd balls, the big 4000hp Argus AS413 H24 based on Jumo 213 pistons, 

And the two giant flying boat diesels
Kloeckner-Humboldt-Deutz:
DZ 710 16-cylinder horizontally opposed diesel
DZ 720 32-cylinder H-block version of the 710

There is nothing crazy about these programs. They were logical programs to provide power plants in the 1000, 2000 and 4000hp class. All were necessary.

The Reich, the German military needed 4000hp class engines and it needed high altitude engines.

They would be needed for the giant transports envisaged for global trade one way or another or the giant 500+mph piston fighters that were being conceived and might come in useful if there was an need to conduct an intercontinental bombing war between a successful third Reich and North America. Remember in 1939 the only country seriously developing such a weapon was the USA with its B-36 which was a fully funded program.

Had the Reich have won in Europe giant transports powered by low wear economical diesels might have been plying a global trade to Sth America, Asia, Africa and even a neutral America rather than R-4360 or R-3350.

It was obvious by 1943 that the turbojet was viable so these engines were abandoned. By flying efficiently in thin air where there is no parasitic drag even the thirsty turbojets of the day promised intercontinental range. 

The variations in allied engines are also significant: you can find single stage, two stage, 1,2 and 3 speed superchargers. the R2800 came with single stage and two stage superchargers, some with independent drive, some with inter-cooling. It came also with turbos. V-1710 with turbocharged, two stage, turbocompound.

Ditto with R-4360. That's just the ones that were built, not just projects that were theoretical investigations.


----------



## wuzak (Jun 11, 2014)

Koopernic said:


> They, the Germans, developed exactly what they had to and suspended anything that was diverting resources from the here and now after around 1941. They did that to a fault in fact, sacrificing long term developments quite frequently.



They kept working on the Jumo 222 which, basically, was a lost cause.

You are only talking about piston engines. There were also a myriad of gas turbine projects - turbojets and turboprops. Even 3 aviation steam turbine projects - two cancelled early in the war, another started late in the war for the Me 264.




Koopernic said:


> The prolific designations that are noted by Daimler Benz are almost all turbo/supercharger variations of the DB601/605/603 series or variations of such as pairing via a gearbox or simple modifications such as adding contra rotating gearbox. Few of these went past theoretical investigation. One can argue that the DB605 was hardly even a new engine: being essentially a bored out DB601 with heavier parts. A lots of these simply needed suffix designations rather than a type number.



This is quite true. Quite a few of them were built and tested, though.




Koopernic said:


> The three engines that the Germans did build to the point of running and close to mass production were the DB604 (X24), BMW 802 (18 cylinder radial) and Jumo 222 (24 cyclinder star) of which the DB604 and BMW802 were abandoned, perhaps foolishly since they may have been less promising in frontal area and weight but more reliable.



I didn't think the BMW 802 was anywhere near production. Nor was the DB 604, frankly.

The DB 604 would have been about the same in frontal area than the Jumo 222, if not lower.




Koopernic said:


> The Jumo 213 was a logical progression Jumo 210->Jumo 211 ->Jumo 213 to meet greater needs.
> You can see the same progression in the Rolls Royce Family eg Kestral, Merlin, Griffon, Perigin, R-type.
> 
> It would have been irresponsible to have neglected development of such engines.



Your history of the Rolls-Royce product is a bit out of kilter.

The Kestrel was developed into the Goshawk (steam cooled) and the Peregrine (basically an all new update of the Kestrel). 
The Kestrel was scaled to create the Buzzard. The Buzzard was developed into the racing R. Which was detuned to become the Griffon I, which did not enter production.

The Griffon that went into production was started later ~1938.

Note that the Buzzard, R, Griffon I and Goshawk were all developed and finished before the DB 600 had even ran.




Koopernic said:


> The DB engines were a family based around an inverted V12 using the same technology, merely scaled. They weren't really developments of each other but hatched in parallel. The bigger engine, the DB603 is almost as old as the DB600 but they were less a progression than a planed family of engines.



The DB 605 was not part of the original program. It was a later development of the DB 601. 




Koopernic said:


> The BMW 801 ->802 was a logical progression.



Yes. As was the R-2600 -> R-2800 and the R-2800 - R-4360.

Even the Centaurus was a logical follow on from the Hercules.




Koopernic said:


> The BMW803 was abandoned and received minimal resources.



I can't speak to that. I thought that the BMW 803 was started during the war, rather than before it.




Koopernic said:


> The DB603/5/1 series seems more coherent that the Rolls Royce program which used radically different configurations (X,V and H blocks) with different valves (sleeve, poppet and 2 stroke) wherease the German variations were often to do with supercharging, gearboxes to pair engines.



Rolls-Royce's war program consisted almost entirely of the Griffon and Merlin, with the Merlin taking up by far the greater amount of energy and resources.

The X engines - the Vulture was being developed at the same time as the DB 600. It was cancelled in 1941, after having developmen suspended during the BoB. The Exe was designed by Rowledge in the early to mid '30s. Only one was built, and development was stopped before the war. The Pennine, as I said before, was begun later in the war and was with the post war period in mind.

The H engine - there was but two. Only one was built. There was some though to making a H-Merlin, with 4 banks of Merlins. And the Eagle.

Sleeve valves - there was the Exe, Pennine, Eagle and Crecy. The Crecy was also two stroke. To repeat, the Exe was finished before the war, the Eagle and Pennine were late war and low priority and the Crecy was developed by only a handful of people, slowing its progress significantly.

You mention that the BMW 803 didn't take up many resources, but you don't concede the same for Rolls-Royce's projects.




Koopernic said:


> We do have some odd balls, the big 4000hp Argus AS413 H24 based on Jumo 213 pistons,



It was actually based on Jumo 213 blocks and cranks, etc. Quite logical really.




Koopernic said:


> And the two giant flying boat diesels
> Kloeckner-Humboldt-Deutz:
> DZ 710 16-cylinder horizontally opposed diesel
> DZ 720 32-cylinder H-block version of the 710



I don't know anything about these.




Koopernic said:


> There is nothing crazy about these programs. They were logical programs to provide power plants in the 1000, 2000 and 4000hp class. All were necessary.



There was nothing crazy about British and American programs in the main, either. There were the odd ones, like the Wright Tornado, but that isn't any worse than the BMW 803.




Koopernic said:


> 1000, 2000 and 4000hp class. All were necessary.
> 
> The Reich, the German military needed 4000hp class engines and it needed high altitude engines.



Did they really need a 4000hp engine?

There wasn't a 4000hp piston engine for the Allies, even post war. I suppose the R-4360 came closest.

The one that was under development, the R-7755, didn't proceed past prototypes.




Koopernic said:


> The variations in allied engines are also significant: you can find single stage, two stage, 1,2 and 3 speed superchargers. the R2800 came with single stage and two stage superchargers, some with independent drive, some with inter-cooling. It came also with turbos. V-1710 with turbocharged, two stage, turbocompound.
> 
> Ditto with R-4360. That's just the ones that were built, not just projects that were theoretical investigations.



The difference here is that the American engines for use with turbos were separate engines connected to the turbo usually by the airframe manufacturer. The change between a non turbo and turbo Allison was the gear ratio in the supercharger drive. All the turbo and intercooler parts were external to the engine. Daimler-Benz, at least, were integrating the turbos in the engine itself - not just the QEC, but the engine.


----------



## Gixxerman (Jun 11, 2014)

Koopernic said:


> while the existing Jumo 213/DB603/BMW801 were more than capable of performing any remaining job; up to 2800hp, with minor modifications



This puzzles me. Perhaps they did manage significantly over 2000hp on a test rig but as I understand it - and I'll be glad to be put right if I'm wrong - one of the LW's big problems is that they never did have engines available (in numbers) of a genuine 2000hp+ rating ( I don't mean ps or brief periods of MW or GM boost either).


----------



## Shortround6 (Jun 11, 2014)

How many projects a "country" can undertake depends on the number of design teams available and the size of those teams. Most, if not all, of the companies underestimated the problems of advancing along the development path. Development had been fairly easy from 1914 to the 1920s and with better fuel (1920s fuel was about 40-50PN) further increases didn't strain or outrun materials and engine design knowledge that much. But the further they went the harder increases got. Desires started to outrun capability of manufacturing and materials. 

Germany was in a bad position because they competing against 3 world powers. They were vastly outnumbered by the allied engineers and engineering staff. It is not enough to have good _idea_ men, you need large numbers of simple draftsmen and number crunchers to turn the "ideas" into reality. You also need foundry men and materials men and machine tool experts to turn the tens of thousands of drawings into actual hardware in large numbers. 

The allies also had better fuel which meant older, smaller engines could be kept in the front lines with less development work than new engines would require (Not that more than a few allied companies didn't try to develop technological _marvels_ that wound up going nowhere). Use the R-R development method, Flog it until it breaks-fix it-flog it again. This lessened the demand for new, larger engines. (the R-2800 was proposed as a 1650hp engine in 87 octane fuel). It meant that the Griffon could be delayed and the Vulture dropped with less loss. It meant that the Centaurus could also be put on the back burner. If the Hercules had topped out at 1300-1400hp with 87 octane fuel the Centaurus could have been pushed somewhat harder. 
However air-cooled engines almost always had a harder time with high boost than liquid cooled engines. For fuel development air-cooled engines were usually referred to as _severe duty_ engines and most liquid cooled engines were considered mild duty engines. 

As far as P W engine development pre and early war goes, P W was working on the R-1830, R-2180 and R-2800 pretty much on their own. The X-1800 and XH-3130 were military development contracts but were started by Mead after a visit to England where it might have been over influenced?. The story (welcome correction) is that Hobbs told the military that he doubted that P W could get any sleeve valve liquid cooled engine into service in time to do any good during the war ( This was in 1940 and who knew how long the war would take?) and asked to be let out of the contracts to work on the R-2800 and R-4360 which used R-2800 cylinders. 
This use of common cylinders or at least common sized cylinders was very common as it helped hold down development work. Using a constant sized cylinder eliminated some variables. 

BTW 



> It was obvious by 1943 that the turbojet was viable so these engines were abandoned. By flying efficiently in thin air where there is no parasitic drag even the thirsty turbojets of the day promised intercontinental range.



Is not even close to being right, unless you consider that taking until the early to mid 1950s was sufficient promise. Unless you think that all the work done on Turbo-compound engines, turbo props and even late conventional piston engines was wasted. The low efficiency early turbo jets had no hope of intercontinental range without aerial refueling. While the British did use Comets on long routes they used stages, London to Johannesburg took five/six stages.


----------



## tomo pauk (Jun 11, 2014)

Wuzak and SR6 covered most:



Koopernic said:


> ...
> As far as your notations on the inferiority of the Jumo 211F/J you overlooked that the engine was operating on 87 octane rather than 100 and latter 100/130. The 6psig the early 87 octane Merlin operated at is essentially 1.4 ata. To get to 12psig (about 1.8 ata) the Merlin needed 100 octane and to get above that level, the 15psig (2.1 ata), 18psig (2.3ata) it needed 102/130 or 102/150 and 25psig it needed 104/150



Whether the fuel is 87 oct, 100 oct, or 150 oct, the Jumo 211J will not go above 1300-1400 PS above 4 km. Not even on 2600 rpm. The better fuel improves power 'under' the rated altitude, not above it. For improving the power above rated altitude, one needs a better supercharger installed (as for Merlin III to 45, for example; or installing a two stage S/C on various engines; or several DB engines with improved S/C, even before the big S/C from the DB-603 was installed), or turning an even greater RPM (DB-601 can serve as an example here). 
The improvements for the Merlin power, with ever better fuel, were also noted at ever lower altitudes. 



> Most of the duplicated engines of the German programs are derivatives eg DB628 (DB605 based), DB627(DB603 based) and so not really duplications but programs adding sophisticated supercharging or turbo charging. The DB605 and hence DB628 was simply going to be too small, just like the Merlin was getting too small, by 1945 hence it would have made sense to focus on the larger 627 instead.



Who says that DB-628 is going to be to small? The DB-603 has issues as late as second half of 1943, we are to expect that a two stage variant of it will be devoid of those just because there is another stage installed? Merlin was good to propel fighters to 450 mph mark, and bombers to 420? mph, that is quite a feat for a 'too small' an engine.
Neither DB-628 nor 627 employed turbo chargers -the 624 did



> The DB605D with enlarged supercharger first ran in 1942 so its surprising an enlarged supercharger took 2 years to enter service.
> The 628 might have made sense on a 4 engined bomber if ready early enough but even if fitted to the Me 109 wouldn't the 109 require too many airframe modifications. These two stage supercharged engines had independent drives, variable pitch fans and variable speed drive on the second stage and were much more effective than more conventional two stage engines.



Where we can read the math that DB version of two stage supercharging used on 628 and 627 was much more effective than conventional two stage systems? That were at least three types in Allied inventory (in service use), so we don't know what one did you have in mind when making such a blanket statement.
I'm also at loss how of the sudden the Bf-109 is promoted from an un-suitable airframe for a 2-stage engine (DB-628 ), into a suitable one.



> Abandoning most piston engine programs made sense after 1944. Only Jets now made sense, even for long range aircraft that were to target the US east coast, * while the existing Jumo 213/DB603/BMW801 were more than capable of performing any remaining job; up to 2800hp, with minor modifications.*



Please, do try to post some sources when stating such stuff. 
BTW, the time to abandon many projects was once the BoB was not won by the LW.



> Jumo 222 didn't seem to have any problems other engines didn't have. It was pushed into production after only 4 years development when 6 were needed by all other WW2 engines. The RLM or Luftwaffe might have accepted the engine into service in derated form but apparently that wasn't an option due to airframe weight growth.



Jumo 222 have had a full list of issues, not just one or two.


----------



## Shortround6 (Jun 11, 2014)

I would note that the BMW 801 must have been a rather amazing engine if it could have gone to 2800hp


> with minor modifications


.

The R-2800 only required a completely new engine to make 2800hp, they saved the bore and stroke and, according to one story, the starter dog. New crankshaft, new connecting rods, new crankcase, new pistons, new wrist pins, new cylinder barrels, new cylinder heads and on and on and on. Just minor modifications right? Granted the older R-2800 gave them a good starting point ( one of the old engines hit 3500hp on a test stand for a moment or two) but service engines are a far cry from momentary test results or even racing engines. 

While some sources say the DB603N was: "Power (max): 2800 PS (2762 hp, 2059 kW) at 3000 rpm at sea level" it was a prototype engine and it is not stated if that was a goal or actually achieved in tests or achieved for a long enough period of time to be usable in a service engine or what it might have done to service life. The increase in RPM from 2750 to 3000rpm results in a 19% increase in stress on the reciprocating parts, on the crankshaft and crankcase. This is in addition to the increased loads due to higher pressures in the cylinder due to higher boost. 
Shorter engine life may be acceptable to the service user to get the desired performance ( and was accepted by the Russians on certain models engines) but tends to be ignored when comparing some German engines to allied engines. German engines may have suffered from material (alloy) shortages or even lubricating oil, I don't know. 

Trying to say which was _better_ gets difficult due to the fuel, material and perhaps oil questions. Different paths were chosen and once started on were very difficult to reverse ( and both sides built their share of clangers).


----------



## rinkol (Jun 11, 2014)

There were some earlier German projects with two stage superchargers. These included the Junkers L88a installed in the Ju 49 research aircraft, the Jumo 207B (mechanical + turbo stages) installed in the Ju 86P and R, and the DB 601D. The last was to be used in one version of the Hs 130, but seems to have been unsuccessful, though the nature of the problems remains a mystery. Many of the later German programs appear to have gone astray in that the extreme rated altitudes that were targeted could not be achieved in a timely way under the circumstances. This may have been motivated by expectation of operations by B-29s at altitudes approaching 10,000 m. If so this was a major success of allied disinformation as the failure of the German programs left them without a good answer to aircraft such as the P-51 and Mosquito during a critcal period of the war.

I understand that there were 2 distinct versions of the DB 605D. the first, developed in 1942 was a major redesign that was not proceeded with due to production issues. The second was an improved version of the DB 605AS with the enlarged supercharger. The last one may have been developed as an interim solution to the problem of delays affecting the DB 628 and other high altitude engines.


----------



## wuzak (Jun 11, 2014)

Shortround6 said:


> While some sources say the DB603N was: "Power (max): 2800 PS (2762 hp, 2059 kW) at 3000 rpm at sea level" it was a prototype engine and it is not stated if that was a goal or actually achieved in tests or achieved for a long enough period of time to be usable in a service engine or what it might have done to service life. The increase in RPM from 2750 to 3000rpm results in a 19% increase in stress on the reciprocating parts, on the crankshaft and crankcase. This is in addition to the increased loads due to higher pressures in the cylinder due to higher boost.
> Shorter engine life may be acceptable to the service user to get the desired performance ( and was accepted by the Russians on certain models engines) but tends to be ignored when comparing some German engines to allied engines. German engines may have suffered from material (alloy) shortages or even lubricating oil, I don't know.
> 
> Trying to say which was _better_ gets difficult due to the fuel, material and perhaps oil questions. Different paths were chosen and once started on were very difficult to reverse ( and both sides built their share of clangers).



The Merlin RM.17SM ran at 2620hp on the test bench, but was officially rated at 2200hp (MS) and 2100hp (FS). It didn't go into production.

Which shows the difference between test bench performance and rated performance.


----------



## Koopernic (Jun 11, 2014)

Just a note to cover some of the preceding responses to everybody.

In general I would argue that the Germans were as rational, if not more rational in 'culling' engine development programs that were too diverse and excessive from 1942 onwards, from that date onwards the cull was very thorough. However it should be noted that almost all development programs were suspended in 1940 during the Battle of France and again at the start of Operation Barbarossa to concentrate on near term weapons deployment by a Fuehrer Directive. Many of these programs did not restart or started again with difficulty and this was often very damaging. It was, overall, a rational directive as these is no point in having long term goals if French tanks are rolling into the Rhineland and but the impact was severe in some areas such as Radar.


Jumo 222 was cancelled from the production program in 1942 and with it the Ju 288 but a low priority development program continued to the point it was regarded as production ready in 1944. The arguments then centered around whether it was worth putting an engine in to production that was only 2800hp, probably 2500hp in service albeit on B4 fuel alone. Clearly the context of the war, the Normandy landings, the development of the Jet etc argued against this. 

Shortround6: there was not really a serious Luftwaffe "Amerika Bomber" as the Me 264 was really a reconnaissance platform and a long range currier that would have had no chance against US fighters such as the P-38. After the granting of lend lease, the USN's neutrality patrols escorting of British convoys it was obvious that war was coming and such an aircraft would probably be needed and so perhaps the development of engines in the 3000hp to 4000hp class continued before being allowed to wither. I'll let readers peruse the Luft46.com website though that site is by no means complete compared to the German Secret Projects series.

Proposals for Jet bombers able to reach the USA centered around cruising the aircraft at up to 50000ft where the air is so thin, perhaps 10%, that parasitic drag disappears and all that is left is induced drag, which is surprisingly small. Rather than high aspect ratio wings what was seen as the way forward was the large wing areas to get altitude and so flying wings or semi flying wings were favored. The nature of jet engines also allows near transonic cruising speeds which allows a reduced wing area due to the high lift at high speed. Use of laminar profiles was also required. The Luft46 aircraft that came out of this (really Luft47) were not really capable of the 8000-9000 mile range required to reach the eastern seaboard of the USA but 3500miles was considered easy to achieve and in one case (Ho XVIII) 5500 even 7500 with extra fuel seemed achievable. As the Luftwaffe had run a series of successful in flight refueling experiments between 1940 to 1943 (culminating in hookups between Ju 290 and Ju 352) these jet aircraft were to feature in flight refueling capability to be fit for purpose.

In reality the Germans were expecting about a 2500 mile range with full bomb load of a B-29 sized jet (Junker EF132).

The engines were to be based around the Jumo 004H, Jumo 012 and BMW 018.

These engines were simply scaled up Jumo 004 or BMW 003 with higher pressure ratios for greater efficiency, compressor blow of valves and a fabricated compressor casing rather than a casting. The Jumo 004H was a scaled down Jumo 012 rather than an improved Jumo 004 with the blow of valve feature. such engines had only slightly improved fuel consumption: perhaps an sfc of 1.1 See Anthony Kay.

The final German war piston engines were big engines and not really over stressed at the 2500hp level: the DB603 series are over 41L much larger than a Merlin or Griffon. Even with a two stage supercharger DB often didn't plan on using an inter-cooler. However after compression the air comes out at 200C and pulling of 75C-100C or so can help and when such a device is added that level of power becomes plausible and these devices were added to the DB603L and DB603N

In General the final engines that managed to get into service or were just short of doing so were:
*BMW801F at 2600hp*, this is an evolved form of the BMW801D2. The "F" didn't make it into service due to tooling issues but a hybrid form of the F and D2 known as the TS made it into service at 2200hp. One can argue over whether a certain boost level was released or not. The F had technologies such as vacuum cast heads, stronger pistons, stronger crankcase, new supercharger and gearing.

BMWTJ and TQ, turbo charged versions. These had very good altitude performance.

The Jumo 213A and 213E1 probably made it into service achieving 2100 to 2050 hp and quite possibly 2240hp, this level of power was certainly undertaking speed runs at the end of the war and may have been used in airfield protection squadrons for Me 262 given fuel delivery documents showing C3 deliveries. A variant capable of 3750 rpm and 2600-2800hp using 4 instead of 3 valves known as the 213J was expected to be capable of 2600hp in short order in service and I believe it was hoped it could reach 3200hp.

However before the 213J would have entered service there was two intermediate versions:
Jumo 213F which was a Jumo 213E without the inter-cooler: some delivered as Fw 190D13
Jumo 213EB, essentially an improved E1 (or F as inter-cooler) good for about 2400hp, larger valves, higher RPM. The Fw 190D13/R25 was expected to achieve 488mph on this engine. It was scheduled for late 1944 production but never made it.

The DB603 had many incarnations but roughly:
DB603EM could achieve 2250hp on C3 + MW50, this engine was cancelled on the grounds that it needed C3 fuel thus delaying the Ta 152C. It had a single stage supercharger
DB603LA could achieve 2250hp on B4 + MW50, this engine was delivered in the form of the Ta 152C and had a two stage supercharger, no inter-cooler.
DB603L, same as above only using an inter-cooler, good for 2400hp, used on Do 335 

The DB603N was expected to archive 2800hp on C3+MW50 was a variant with a two stage inter-cooled supercharger, it had the infinitely variable supercharger drive as well as two mechanical gear supercharger speeds that could easily be changed to different ratios as required.

Tommo, the Luftwaffe or RLM did not plan for a high altitude war developing so early. In a way the Development of the Merlin was 'lucky' in that the only way forward was a two stage inter-cooled engine and such an engine had been developed for the Wellington high altitude bomber. This is the origin of the Merlin 61 for the Spitfire IX, the supercharger/inter-cooler being used useful for power with its good altitude performance being a welcome side effect.

Junkers EF132 about the size of a B-29 range of 2500 miles with full bomb load. With a soviet style stepped cockpit and a pair of engines instead of sixtuplet this became the Tu 16 Badger. Little known Fact: Tu 4 (B-29 copy), Tu 16, Tu 95 Bear all use B-29 diameter fuselage.









Below 120 ton Focke-Wulf Project 195 with 8 x Jumo 222, 




Dornier Do 214 with 8 x 4000hp engines: The Dornier Do 214 would have had 192 pistons to service and clearly diesels with their lessor number of larger cylinders make more sense. This was a civilian aircraft project and is shown in its militarized form.




Blohm Voss BV P.207.02 Heavy fighter with 4000hp Argus AS413 engine H24 configuration based on Jumo 213 pistons. This aircraft is painted as toss bombing probably using the TSA2D computing sight using a pair of BT1000 or BT1400 bombs. These 1000kg/1400kg bombs penetrated the water tunneled much as a torpedo, and were to detonate using a proximity detector reacting of the ships metal. Clearly they would have destroyed an aircraft carrier or battleship. This is an indication of the kind of power that might have been needed had the jet not developed. I think by 1946/47 an XP-72 superbolt would have been considered smallish.


----------



## wuzak (Jun 11, 2014)

I don't believe a Jumo 213J would turn at 3750rpm....for long.

Also, the DB 603 was 44.5l - 21% larger than the Griffon, the single stage version weight roughly the same as the two stage Griffon, which had more power. It had a bigger bore (160mm vs 152.4mm) and longer stroke (180mm vs 167.6mm) than the Griffon, and a longer crankshaft. The long bore and crankshaft contribute to stress issues, while the larger bore and longer stroke have an effect on combustion.

The Me 264 was absolutely designed as a bomber. Reconnaissance was a secondary role.

The Ju 288 switched to DB 610s and was still planned to be put into production late in the war. It was cancelled, I guess, in favour of making more defensive fighters.


----------



## Shortround6 (Jun 11, 2014)

Koopernic said:


> Shortround6: there was not really a serious Luftwaffe "Amerika Bomber" as the Me 264 was really a reconnaissance platform and a long range currier that would have had no chance against US fighters such as the P-38. After the granting of lend lease, the USN's neutrality patrols escorting of British convoys it was obvious that war was coming and such an aircraft would probably be needed and so perhaps the development of engines in the 3000hp to 4000hp class continued before being allowed to wither. I'll let readers peruse the Luft46.com website though that site is by no means complete compared to the German Secret Projects series.
> 
> Proposals for Jet bombers able to reach the USA centered around cruising the aircraft at up to 50000ft where the air is so thin, perhaps 10%, that parasitic drag disappears and all that is left is induced drag, which is surprisingly small. Rather than high aspect ratio wings what was seen as the way forward was the large wing areas to get altitude and so flying wings or semi flying wings were favored. The nature of jet engines also allows near transonic cruising speeds which allows a reduced wing area due to the high lift at high speed. Use of laminar profiles was also required. The Luft46 aircraft that came out of this (really Luft47) were not really capable of the 8000-9000 mile range required to reach the eastern seaboard of the USA but 3500miles was considered easy to achieve and in one case (Ho XVIII) 5500 even 7500 with extra fuel seemed achievable. As the Luftwaffe had run a series of successful in flight refueling experiments between 1940 to 1943 (culminating in hookups between Ju 290 and Ju 352) these jet aircraft were to feature in flight refueling capability to be fit for purpose.
> 
> ...



The Germans could propose or specify whatever they wanted. For a reality check try looking at the Boeing B-47 Stratojet bomber. Wingspan 116 feet 0 inches, length 106 feet 10 inches, wing area 1428 square feet, Weights: 78,102 pounds empty, 122,650 pounds combat, 184,908 pounds gross and in overload in excess of 200,000lbs. Combat radius 1965 miles with 10,00 pounds of bombs. 4444 miles ferry range. Six General Electric J47-GE-23 turbojets, 5970 lb.s.t. each. Service ceiling 33,900 feet, combat ceiling 40,800 feet. 

Granted it used a smaller wing and was a lot heavier when loaded but take-off was Takeoff ground run 9100 feet, 7200 feet with JATO and this was in the summer of 1952. The J-47 engines had a pressure ratio of either 5:1 to 5.5:1 depending on model and used a 12 stage compressor. Quite a number of late 40s and early 50s jets could not quite make 50,000ft, some of them by close to 10,000ft. 

Or find some other jet bombers that were actually built and flown in the late 40s or very early 50s, or failing that try a jet airliner or two. The jets offered a _promise_ but that promise turned out to be a long time coming even with the cold war and Korea. Piston engines provided the power for commercial intercontinental transport instead of jets until the mid or late 50s, first Boeing 707 went into _service_ Oct 1958, despite high fuel costs (often using 108/135 or 115/145 fuel) the use of water injection for take-offs and maintenance problems. 



> The final German war piston engines were big engines and not really over stressed at the 2500hp level: the DB603 series are over 41L much larger than a Merlin or Griffon. Even with a two stage supercharger DB often didn't plan on using an inter-cooler. However after compression the air comes out at 200C and pulling of 75C-100C or so can help and when such a device is added that level of power becomes plausible and these devices were added to the DB603L and DB603N



A DB 603 turning 3000rpm has a piston speed of 3545fpm. A Jumo 213 turning 3250rpm has a piston speed of 3520. Nobody else used piston speeds within 10% of those numbers during the war. 



> In General the final engines that managed to get into service or were just short of doing so were:
> *BMW801F at 2600hp*, this is an evolved form of the BMW801D2. The "F" didn't make it into service due to tooling issues but a hybrid form of the F and D2 known as the TS made it into service at 2200hp. One can argue over whether a certain boost level was released or not. The F had technologies such as vacuum cast heads, stronger pistons, stronger crankcase, new supercharger and gearing.



"vacuum cast heads, stronger pistons, stronger crankcase, new supercharger" are minor modifications?


----------



## Koopernic (Jun 12, 2014)

wuzak said:


> I don't believe a Jumo 213J would turn at 3750rpm....for long.
> 
> Also, the DB 603 was 44.5l - 21% larger than the Griffon, the single stage version weight roughly the same as the two stage Griffon, which had more power. It had a bigger bore (160mm vs 152.4mm) and longer stroke (180mm vs 167.6mm) than the Griffon, and a longer crankshaft. The long bore and crankshaft contribute to stress issues, while the larger bore and longer stroke have an effect on combustion.
> 
> ...



I have read Frank Vann's biography of Willy Messerschmitt and I have read Manfred Griehl's "Luftwaffe over Amerika" which contains extensive minutes of meeting on the Me 264 between Milch, the RLM, Luftwaffe and Messerschmitt.

Messerschmitt privately promoted the aircraft as a maritime reconnaissance aircraft and long range currier to the far east perhaps picking critical raw materials, it was to be fast enough to generally avoid naval fighters and was to be armed only with a pair of waist guns. He eventually received limited RLM support but it was so limited he had to transfer much of the work to Dornier as he lacked the hanger space.

There was a plan to develop this aircraft eg by up scaling to 6 engines to be able to achieve the 9000+ miles needed to fly a return mission to the Easter Seaboard of the USA. This version was known as the Me 264/6m (for 6 motors) latter as the Me 364. The 6 engine version was latter found to not add much performance though it did increase armament.

Developing an aircraft powered by 4 x 1200hp engines with a range of 9000 miles was a difficult task, if not impossible. High MTOW and wing loadings and the need for an impossible to provide 10000ft concrete runway were one, the B-36 could do the job in 1/4 of that. RATO was considered but since almost an entire Battalion of Soldiers had been killed in an Me 322 RATO failure the idea was not liked. Messerschmitt claims to have eventually gotten the range using the 1800-2000hp class engines in theory but we are still considering an aircraft flying at very slow economy cruising speeds, literally dawdling along and lightly armed. The Luftwaffe remained cynical. There were many variations an improvements considered including some hybrid versions using swept wings, jets and DB603 piston engines, remote controlled armament but they are not really the same aircraft and essentially only design studies. In conjunction with in flight refueling they would probably have been viable but I hardly think that it would work to project unescorted bombers that distance in to a technically advanced target such as the USA which had radar and turbocharged aircraft. The attrition would have been horrendous. The reconnaissance / Currier role was enough and on its own would have been very valuable. Strategically it would have caused a lot of US air defense expenditure for the cost of a few nuisance raids. Psychologically leaflet dropping raid would have forced the expenditure without triggering calls for revenge.

Getting a DB603 produce 2800hp wasn't going to be too big a problem. The DB605 at 1.3ata grew from 1320hp on 87 octane to nearly 2000hp on C3+MW50 at 1.98ata; approx a 50% increase using only a single stage non intercooled engine. The DB603 at 1.3 ata managed 1750hp but by applying the same treatment and adding a two stage supercharger and an inter-cooler it would seem highly plausible that a 50% increase could be realised. DB605LA were seeing service at 2250hp at the end of the war and I've seen charts with 2400.

I also don't see too much of a concern with the 3750rpm speed of the Jumo 213J. It's no more absurd than 28psig boost on a Merlin (3 atmospheres, more pressure in a Merlin than a first generation turbojet) A lot of research went into improving engines and understanding the issues. Metallurgists developed new defect free materials, tribologists new lubricants that continued to operate at high speeds, pressures and and temperatures. I've seen a text book on piston development on google books preview and it shows photographs of DB604 pistons and its obvious a great deal of science and instrumentation went into it.

The pistons were not round, but oval to avoid scrapping, machined to micron accuracy. Having decided on 3750 rpm was the way forward for their next production variant the Junkers engineers set about doing it step by step. The specific output can only be increased with greater RPM, greater boost. All stress the engine.


----------



## Koopernic (Jun 12, 2014)

Shortround6, I always find your posts highly informed and therefore enjoyable to read.

"vacuum cast heads, stronger pistons, stronger crankcase, new supercharger" are minor modifications?
The BMW801E/F seemed an all new engine which is probably why it never entered service though certain parts of it did, such as stronger pistons. It was probably an all new engine like the 2800hp PW R-2800.

To be fair the Germans weren't the only aerospace engineers to over promise performance. Also the B-47 had two significant design limitations arising from its rushed design: it's wing loading was way to high, hence it had a somewhat unsatisfactory low service ceiling and its wings were way to thin thereby restricting fuel load, creating aeroelastic issues and possibly landing speed issues. These were all fixed in the B-52. The British V bombers were in many ways better aircraft but then they also were a great many years latter into service.

I'm not sure I get your performance specs for the B-47. As far as I understand it:
Service Ceiling = altitude at which rate of climb is less than 100ft/minute
Opperational or Combat Ceiling = altitude at which rate of climb is less than 500ft/minute.
So our combat ceiling should be less than service ceiling?

I agree that piston speed, not RPM is the key metric, didn't want to waste electrons on that. Obviously an engine needs to be pushed at some parameter. The centrifugal stresses go up with the square of engine RPM so a 20% increase in RPM implies a 44% increase in stress (not including pressure from the power stroke). That wouldn't seem to be too much to handle. We can make the components stronger or we can use better metallurgy, the latter being clearly preferable. There are lubrication issues I can't even begin to imagine.


----------



## wuzak (Jun 12, 2014)

The Me 264 wasn't designed around 1200hp engines. It was designed around DB 603s of 1750hp, but got stuck with Jumo 211s because that's all there were. Later it got some BMW 801s, but these weren't strong enough either.


----------



## wiking85 (Jun 15, 2014)

Koopernic said:


> In general I would argue that the Germans were as rational, if not more rational in 'culling' engine development programs that were too diverse and excessive from 1942 onwards, from that date onwards the cull was very thorough. However it should be noted that almost all development programs were suspended in 1940 during the Battle of France and again at the start of Operation Barbarossa to concentrate on near term weapons deployment by a Fuehrer Directive. Many of these programs did not restart or started again with difficulty and this was often very damaging. It was, overall, a rational directive as these is no point in having long term goals if French tanks are rolling into the Rhineland and but the impact was severe in some areas such as Radar.



You sure about that? The R&D situation exploded from 1942 on in terms of design proliferation. Even with engines; there was some culling, like the BMW 802 and 803, Jumo 223, but there were plenty of other projects added, especially in terms of jet engines, the Jumo 224 (just a bigger displacement 223) DB V16 project, plus lots of sub-projects within successful piston engine projects. For instance why develop turbo-superchargers when you don't have the raw materials to make them? They persisted even as the jet engine projects were moving on to other materials.


----------



## Gixxerman (Jun 15, 2014)

Koopernic said:


> With a soviet style stepped cockpit and a pair of engines instead of sixtuplet this became the Tu 16 Badger.



I'm sorry but I have a real problem with this sort of comment.

The Tu 16 didn't fly until mid 1952, almost a full 7yrs after the war ended, the wing of the Junkers EF132 looks nothing like it and the fuselage bears only a superficial similarity (and I'm willing to bet that internally they are nothing like similar either).
Yes I accept that (as in the USA, UK France) German knowledge informed the coming new aircraft but mere design proposals did not just 'become' aircraft x, y or z.
Those ideas were massively developed nothing close to the specs of the original (often unbuilt or untested) ideas, regardless of how advanced the idea was in 1945.
There were many years of additional new design, construction advances new material developments required, not forgetting the matter of the huge leap in engine performance required to power them (in the case of the Tu 16 it required 2 x 21,000lb thrust engines verses the best WW2 German jet prototype engine in WW2 of, what, just shy of 3,000lbs?). Between 3 - 10yrs often.
I am aware that the Jumo 022 was eventually developed into the monster turboprop Russia used (just as the BMW jet was the basis of the very successful French Atar jet family but they took many years of further development work to get to that stage.
It's like when people talk about how the US space program was 'just' what the German rocket program.
Which disregards the years of work (way beyond what was done in Germany to 1945) it took to get into orbit and all the rest.

Sorry, maybe it's just me but I think that sort of comment vastly underplays the huge amount of work that went on by engineers pilots long after 1945.


----------



## GrauGeist (Jun 15, 2014)

If anything, the EF132 looks closer to a B-52 than a Tu-16


----------



## Shortround6 (Jun 15, 2014)

"Sorry, maybe it's just me but I think that sort of comment vastly underplays the huge amount of work that went on by engineers pilots long after 1945.

I am just shocked that you could say such a thing. I repeat, simply shocked as everyone "knows" the Germans were just 12-24 months away from mass producing aircraft, engines, missiles, guns, tanks, submarines, field kitchens and porta-pottys it would take 7-12 years for the Americans, British, French and Russian to build (with the help of hundreds of German engineers?????) in 1945. 

If you squint kinda hard and smoosh the cockpit into a British style the Vickers Valiant doesn't look that different either.






Since wind tunnels don't lie ( aside from minor variations) a lot of people were going to come to similar conclusions given similar requirements and hardware status. 

EF 132 was designed around a proposed (or work in progress) engine rather than one that was actually flying. While it had some advanced features and specifications it might have taken a number of years to turn them into reliable hardware. Some of the numbers don't line up real well either. The Jumo 012 engine was proposed at 5500-6130lb thrust (and it may have given it under test, who knows) but it weighed 4000-4400lbs depending on source so six of them weigh 24,000-26,400lbs in plane that was supposed to weigh 69,000lbs empty. 

A-S Sapphire (Wright J-65), R-R Avon (early) and GE J-47 all went around 2500-2750lbs depending on model and gave around 5000-7500lbs thrust depending on model and dry or water injection. A R-R Nene could give around 5000lbs thrust for around 16-1700lbs weight and the Tay ( P&W J-48 ) could give over 6000lb dry for about 2000lbs weight. 

The Axial compressor was the way to go but took years and years to get there. 

It also took years for _anybody's_ jet engines to get to be reliable enough for long range bombers. Think about it. Assuming 3 times the life of a German WW II service jet engine (10 hours?) and a 10 hour mission ( 400mph cruise and 2000 mile radius) you would have to change _ALL_ the engines (4-8 ) every 3 flights assuming that NONE crapped out on any particular flight. Granted by Korea things were going much better but the allied engines weren't all that good in 1944-45-46 either. 

As a benchmark the early P&W J-57s that powered the early B-52s gave about 10,000lbs thrust, weighed about 4200lbs and had a pressure ratio of about 12.5 to 1 and a fuel consumption of 0.80lb./lb.t./hr. 
_AND_ were not what was really wanted or required for the mission.

Reactions: Like Like:
1 | Like List reactions


----------



## Koopernic (Jun 15, 2014)

wuzak said:


> The Me 264 wasn't designed around 1200hp engines. It was designed around DB 603s of 1750hp, but got stuck with Jumo 211s because that's all there were. Later it got some BMW 801s, but these weren't strong enough either.



Unbelievably I had the Creek/Forsyth book "Me 264 Amerika Bomber" still in its Amazon wrapping.

Below is the estimated data; you'll note the Engine was to be the 2100hp DB603H operating on C3 fuel. The DB603A that was available from 1943 was good for only 1750hp and couldn't have gotten the Me 264 off the ground for an "Amerika Mission" which required 50 tons takeoff weight and a 2050m runway or alternatively 1320m with RATO. The B-36 was underway first incidentally with RLM interest (call for preliminary tenders in 1939) with interest from Hitler and the High Command only coming in late 1940 as the US/German relations deteriorated. Prior to that the purpose of the project was currier (to asia) and maritime reconnaissance while the new mission envisioned missions to the US. However the Me 264 was still seen as a Currier/maritime recon platform as well.

However if one removed 10 tons of bombs of the Me 264 and operated with only 4 tons (8800lbs) and also removed 10 tons of fuel one ends up with an aircraft with a range of about 1500 miles and a take of weight of 30 instead of 50 tons that should have a good TO field length of about 1100m with the weaker 1750hp engines. The 1730hp BMW801 engines may have have been available with a short time takeoff rating using MW50 or C3 injection in late 43 on the Ju 188 to give somewhere around 1900 to 2000hp. I would expect only 1 minute takeoff rating but the higher drag and inferior fuel consumption of that engine still made it inadequate for the "Amerika" mission. Nevertheless both Junkers and Daimler Benz were pushing 2200hp engines out the factory doors in late 44 or early 45. My opinion they needed 2600-2800hp to operate without RATO in the kind of runway that they could build, operate and defend without it getting bombed, that kind of power was available on the Jumo 222 and advanced derivatives of the Jumo 213; the Jumo 213S, EB, J or DB603L or N. Indeed the Jumo 222 was seen as a possible option.

I calculate that a 40% reduction in wing loading frpm the reduced weight would lead to a 23% reduction in takeoff speed. I calculate that the 15% reduction in power in the context of a 40% reduction in weight leads to about an overall 25% increase in acceleration which combined with a 23% reduction in takeoff speed means the takeoff run should be under 1100m. Thus the Me 264 would be useful without long runways at reduced load without RATO while the better engines matured. And of course they had developed in flight refueling. The politics, finding basic resources such as detail draftsmen, hanger space etc stalled the program.






The aerodynamics seem to have been verified quite well in the underpowered Me 264V1 with Jumo 211 testbed/prototype. The operational version was to have remote controlled guns:


----------



## Koopernic (Jun 17, 2014)

Double post


----------



## Koopernic (Jun 17, 2014)

Shortround:
That’s a nice picture of a Valiant.

These are the statistics for the Me 262, I will compare them to Junkers EF 132 and Me B-47E to show how plausible EF 132 was.

*Me 262*
Empty Weight
Maximum Takoff Weight 7130kg/15720lb
Weight of Jumo 004B-4 Engines 745kg/1650lbs
Thrust of Engines 900kg/1980lbs x 2 = 1800kg/3960lbs
Thrust to Weight Ratio of Engines 900/745 = 1.185
Power to Weight Ratio of Me 262 at MTOW 1800kg/7130kg = 0.2525
SFC of engines 1.4

*Junkers EF132*
_The data I have used is from Anthony Kay’s “German Jet Engines and Gas Turbines 1932-1945”. As he was the preliminary designer of the RR (then Bristol) Olympus I rather trust him. He gives a Static Thrust of 2780kP and a weight of approx. 2000kg which reduces to 2200kP at 900kmh. Note design of the Jumo 012 was complete and mock-ups had been built while most components had already been fabricated in preparation for assembly of a prototype. The Soviets took over the factory and had Junkers engineers complete the engine. It benched successfully,*only one year after the war, in June 1946* although one variant blew up on the test rig a few months earlier. The development of this engine was not proceeded with as the British Labour Government of Clement Atlie handed the complete technology of the Rolls-Royce Nene turbojet inclusive of alloys and production methods to the Soviets leading to the MiG 15 being developed around this engine. Since there had been a program to develop the Jumo 012 into a Jumo 022 turbo prop the design team was re-tasked which lead to the 13800shp NK12 used in the Bear which had the same configuration: single spool axial with blow of valves._

*Junkers EF132*
Empty Weight 31300kg/69000lbs
Maximum Takoff Weight 65000kg/143300lbs (approx as early B-29 and 66% that of a B-47)
Weight of Jumo 012 Engines 2000kg/4400lbs (from Kay)
Thrust of Engines 2450kg/5400lbs to 2780kg/6130lbs (later figures from Kay)
Thrust to Weight Ratio of Engines 2780/2000 = 1.39
SFC of engines 1.2
Power to Weight Ratio of EF 132 at MTOW 15000/65000 *0.2262*
Or 16680/65000 *0.2561* using the Kay figures.
Wing Loading EF132 at MTOW 65000kg/161m2 =403kg/m2

The B-47E has a much higher wing loading of 753kg/m2 compared to EF-132 but a slightly inferior TW ratio of between *0.22* down to *0.19*. Its J-47 engines have an sfc of 1.04 as opposed to 1.2, but this is only 18% better and the Jumo 012.

The EF 132 has the same thrust to weight ratio as both the Me 262 and the B-47E which shows the proposed weights are sensible.

Compared to the B47E, the EF132 has a larger wing in absolute terms but also a lower weight to B-47 and thus a much lower wing loading than the B-47. That larger wing probably costs it some speed as compared to the B-47's ie 607mph versus 578mph. The lower wing loading would mean it has a much better take-off field length which would be non negotiable for the Luftwaffe.

The Junkers EF-132 has only 50% of the range (2100 miles instead of 4200 miles) and 50% bomb load of the B-47E at that range but it has 66% the MTOW of the B-47E while being 90% of the empty equipped weight. So it has paid a more than proportionate price in range, reduced bomb load and primarily by reduced fuel load to compensate for its heavier engines but it is still respectable. 

The weights and mass fractions of structural, fuel and engine weight make perfect sense when compared to the Me 262 and B-47 despite the inferiority of the more primitive Jumo 012 in T/W ratio. The inferior SFC of the German turbojet is not very significant as it is small.

The EF 132 was completed under soviet control but never flown, though there are photographs of it.

This is the EF140 completed under soviet control in 1947 with Soviet Nenes.




This is the Ju 287v1 test bed in flight using a He 177 fuselage. Handling was good with only a little proverse yaw.




This is the Ju 287A1 with a cluster of BMW 003 instead of nenes. It is based upon the Ju 288 fuselage, this is the Ju 288 abandoned in 1942 due to engine power at 2000hp being inadequet.




The gun system, which was developed from the Ju 288 used servo control to position the gun. Aiming was by a remote periscope with upper and lower outlets rather than just a sight. This kept the gunners face clear, allowed him to view through bullet proof glass which had better night vision. Unlike the GE system used in the B-29 the position of the guns was fed back to the sight to avoid misalignment from fuselage distortion as occurred in the B-29.


----------



## Koopernic (Jun 17, 2014)

Gixxerman said:


> I'm sorry but I have a real problem with this sort of comment.
> 
> The Tu 16 didn't fly until mid 1952, almost a full 7yrs after the war ended, the wing of the Junkers EF132 looks nothing like it and the fuselage bears only a superficial similarity (and I'm willing to bet that internally they are nothing like similar either).
> Yes I accept that (as in the USA, UK France) German knowledge informed the coming new aircraft but mere design proposals did not just 'become' aircraft x, y or z.
> ...



German aerodynamicists seem to have completed all the research, accumulated all the data they needed to build large scale swept wing aircraft.

I do not see years of work ie 5-10. I see 1 maybe 2 years. Remember these people were able to get a He 162 in the air in 60 days from initial design. There was a great deal of experience around. The Jumo 012 benched in June 1946 under soviet control.

For instance they knew of the effect of wing sweep and extensively tested such in rather large supersonic tunnels (facilities the allies just didn’t have) and also high speed subsonic tunnels. The level of technology and understanding was truly impressive and detailed with plenty of useful data and tables having been accumulated. The only thing holding them back was the development of more powerful engines than the 900kg Jumo 004 it being much easier to develop airframes than engines.

One problem, really the only problem, is that wing sweep and the interaction with the fuselage produces ‘span wise flow’ along the wing. The extended distance the outward flowing air experiences leads to a premature flow separation at higher angles of attack and the resultant tip stall and a spin.

To overcome this the following were developed:
1 Leading edge Slats (known to all at this time but not in connection with span wise flow)
2 Compound Sweep, the so called crescent wing seen on the Handley Page Victor where the sweep is reduced at the tip thereby disrupting the flow. To be used on the “Ar 234 crescent wing” being readied at the end of the war.
3 Leading Edge Flaps
4 and Krueger Flaps
In general leading edge flaps do not improve the coefficient of lift of typical WW2 wing profiles very much; however they have a very significant improvement on thin wings.
5 Forward Sweep as test bed flown on the Heinkel He 177 based Junkers Ju 287, forward sweep of course causes ‘inward span wise flow’ and eliminates the flow problem at the tips.
6 Aerodynamic Twist where instead of twisting the wing tips up to avoid premature tips stall the outer wings are given a more forgiving profile. (twist tends to induce shockwaves)
They were also aware of ‘area ruling’ which also effected span wise flow as well as shock drag.
7 They had used wing fences and seem to have integrated them on some designs, fences were tested on a Bf 109B however I have only seen them integrated in the form of fins or booms for tailless designs.

The structural and aeroelastic advances were there as well:

The forward swept Ju 287 also introduced the idea of unbroken upper and lower wing skins to create a very stiff wing and by suspending the engines of the wing and the idea of positioning the engines such that the frequency of the pendulum effect damps out the aeroeleastic flutter used latter on Boeing designs with rearward sweep and subsequently most airliners.

The Arado 234 introduced a new construction method whereby the rivets were attached to points of equal curvature rather than at points of equal chord. This produced a super flush and precise wing surface. Such precision is needed to avoid uneven shock wave formation on left and right wing.

The Ju 288 wings, for instance, were to be pressed out, with 4 powerful pressed and forged wings spars to speed production and achieve precision. The construction techniques were indeed quite advanced.
What they don’t seem to have been aware of was
1 The dog tooth leading edge
2 They favored tailless designs, deltas, or high “T” tails to avoid shock impingement in supersonic (not transonic) aircraft rather than the British developed all flying tail. Ironically most German fighter designs used all trimming tail planes rather than trim tabs on the elevator.

One of the more irritating problems of transonic aircraft, in particular swept ones is high speed snaking. Even here the Germans had tested a solution in 1943 on a Herschel Hs 132 in which a rate gyro was elect hydraulically attached to the rudder of an aircraft to damp or kick back against uncommanded yaw (snaking). (Reference Aeronautical Research in Germany from Lilienthal to today by Hischel, Prem and Madelung.)

The problems the victorious allies had seems to relate to the difficulty in absorbing that 10 years of research and more importantly familiarity the Germans had accumulated. The failure of the DeHaviland DH.108 and the loss of its test pilot, Geodfrey DeHaviland shows a case in point; the Vampire nose was left too blunt and the shock stall caused pilot coupled oscillations an over stressed the aircraft, no planed German supersonic vehicle or missile, there were several, was unaware of that.

The result is they often reinvented the wheel.

The Tu 16 Badger had a walk through fuselage the EF132 didn't but the configuration was the same. The Soviets were very vigorous in exploiting their German engineers and scientists, often going to the extreme of giving them Russian names so as to allow them to taunt the Americans and British for their scientists without fear of reprisal or keeping them in a segregated design buero and then reassigning it to another if the design was promising.


----------



## Juha (Jun 17, 2014)

Koopernic said:


> ...The Tu 16 Badger had a walk through fuselage the EF132 didn't but the configuration was the same. The Soviets were very vigorous in exploiting their German engineers and scientists, often going to the extreme of giving them Russian names so as to allow them to taunt the Americans and British for their scientists without fear of reprisal or keeping them in a segregated design buero and then reassigning it to another if the design was promising.



Some examples of the pseudonames and who were the Germans who participated the Tu-16 design team?

We know that the ex-Junkers team under Dr. B. Baade produced OKB-1 150 jet bomber proto, what are their other achievements in SU?

Juha


----------



## GrauGeist (Jun 17, 2014)

> I do not see years of work ie 5-10. I see 1 maybe 2 years. Remember these people were able to get a He 162 in the air in 60 days from initial design. There was a great deal of experience around.


But the He162 was plagued with problems, one of which, was because it was being rushed through production by forced labor. It was also suffering from the lamination problems that created difficulties for the Ta154 and other projects. These are conditions that could have been corrected *if* they had spent more time evaluating the airframe before production. 

This would hold true to all other projects that were being rushed along in the hopes that one or more would somehow turn the tide of war.


----------



## Shortround6 (Jun 17, 2014)

The pace of Allied progress after the war changed dramatically back and forth several times making comparisons to war time progress difficult. Late 1945 and 46 saw many programs cut/slowed down and then speeded back up again. The coming of the cold war and especially the first Russian A-bomb test ( Aug 1949) put a lot of programs on the fast track even if not quite the pace of 1943/44. 

It takes a number of years for a _lot_ of principles/theory's to make it from paper to _functioning_ hardware. The Meredith effect was read in a paper presented at a conference in 1935. Other people may have proposed the basic idea or written it down but Meredith wrote it up and presented it with mathematical formulas. It still took around 5-6 years to see it's most famous incarnation and people still argue over how effective it really was. 

You can't hide physical phenomenon forever and often several people working independently arrive at the same solution in the same time period. 

" In the United States, NACA engineer Robert Jones had discovered the concept of swept-back wings in January 1945, conducted wind tunnel tests in March, and published his results in May. But it took confirmation from the Germans before anyone went ahead with the idea." Now this may be a bit biased and perhaps Jones knew of German pre-war work or had seen photos of German aircraft with Swept wings in Dec 1944/Jan 45. 

In any case North American had decided to scrap the straight wing version of the F-86 (design started in 1944) in the summer of 1945 with the knowledge gained from captured German data and the swept wing (early version) was designed and approved by the USAAF by Nov 1 1945 (strangely enough _AFTER_ wind tunnel tests confirmed both high speed drag reduction and effectiveness of slats in low speed handling, Guess NA didn't know they didn't have access to a working wind tunnel).

Feb 28th, 1946 sees full sized mock up of F-86 inspected and approved and first flight took place in Nov 1947.

Up in Seattle "The first XB-47 (46-065) rolled out of the factory at Seattle on September 12, 1947" Seems like it took the guys at Boeing _years_ to absorb all that knowledge. 


The Germans did do a great deal of research and were ahead of the allies in many areas ( the allies were also ahead of the Germans in a lot of areas) but it often took years to turn a paper sketch into _service_ hardware, as in it take 1 1/2 to 2 years to go from Prototype to combat use. He 162 going from "design" to complete prototype in only 60 days is a bit misleading also. How much of the design was cribbed from other He projects or wind tunnel experiments?

Reactions: Like Like:
1 | Like List reactions


----------



## Koopernic (Jun 18, 2014)

Robert T Jones was actually ahead of that; actually started his work in 1943 by dropping instrumented supersonic delta winged darts from aircraft, he did a report in 1945 on a arrow head (literally a 1 inch diamond) that was published at the NACA that was dated 1946 or 47, you can still find it on the Cranfield mirror though the US industry, such as Boeings Geroge Schairer were aware of the report before then.

What is missing is the practical stuff such as methods to make delta wings work in landing IE slats, leading edge flaps, double delta's. Really, they already had a swept wing aircraft in flight: the Ju 287.

The problem with wooden components on German aircraft such as the Ta 154, He 162 was that the plywood was normally laminated by heat curing a special glue te-go or tego film at the which required special heated roller presses. Both the presses and the glue was damaged by bombing leading to use of inferior lamination glues that actually could corrode the wood, adequate for furniture maybe. There were generally problems with joinery adhesive quality as well. Building wooden aircraft was generally a waste of time though it would've matured.

I still say that German aerodynamic knowledge was complete enough by then to design an aircraft and get it right straight away, there are drawings with markups by Professor Messerschmitt himself in which he has rejected preliminary designs sent to him for review because they didn't conform to the area rule. The damper was jet engines which weren't powerful enough to exploit the advances. The book "Secret Messerschmitt Projects" reproduces some of these, it is a hideous translation but if you already have some aerodynamic knowledge.

Below is the Messerschmitt P.1011 test bed which had variable sweep wings (ground settable only) whose configuration was developed into the X5. This aircraft was not selected for production, The Focke-Wulf 183 was, as a more advanced model the ME P.1112 was expected to be developed to production using P.1011 wings.

Incidentally, having learned from the Me 210 disaster Messerschmitt had learned fast tracking and risk management. The test bed could check various sweep angles while they prepared both 12% and 20% slats in case 12% wasn't enough. It was though hydraulics might be needed so the aircraft was prepared so that these could be fitted.


----------



## Shortround6 (Jun 18, 2014)

> I still say that German aerodynamic knowledge was complete enough by then to design an aircraft and get it right straight away, there are drawings with markups by Professor Messerschmitt himself in which he has rejected preliminary designs sent to him for review because they didn't conform to the area rule.



Well, they missed on the He 162. Downward angled wing tips were to compensate for ???

and which is it "get it right straight away" or "while they prepared both 12% and 20% slats in case 12% wasn't enough. It was though hydraulics might be needed so the aircraft was prepared so that these could be fitted." 

Right straight away _if_ you use belt, suspenders and double sided tape all at the same time? 

Lockheed didn't do too bad with the P-80 by designing and building the XP-80 in 143 days ( it weighed over twice as much empty as the He 162 and might be considered a more complicated aircraft), It still took over a year from first flight to get 4-6 "trial" examples to Europe after it's first flight (and a slight enlargement of the aircraft) A number of German scientists, engine and airframe designers/engineers came to the US right after the war and some came later (one wound up head of the GE Jet engine division) and it still took until the early 50s to get axial compressor engines to "beat" centrifugal compressors. Of course the target was shifting a bit. A 1950-52 Axial compressor engine with high pressure ratio couldn't slide by with 25-50 hours of engine life like it could in 1945-46, not when the centrifugal and simple axial engines were achieving engine lives of hundreds of hours if not starting to exceed 1000 hours.

Lots of countries had bright engineers/scientists who had a lot of good ideas or new (and sometimes overlapping) theories. The inability of a particular country to bring these ideas to service use in short periods of time reflects much more on the state of the manufacturing art in a country than in the quality of those engineers/scientists. I am using "state of the manufacturing art" a bit loosely so as to cover material shortages, bomb damage/disruption, lack of low level engineers/draftsmen and a host of other things that can keep an idea/theory from going into production no matter how good or advanced the basic idea is/was. As an example the Russian probably used as many turbo-charged experimental aircraft or engines as the rest of the world put together (US excepted) but never succeeded in actually mass producing a turbo charged aircraft or engine (numbers in hundreds and not dozens) due to manufacturing problems. We *know* the idea works and the idea dates back to WW I but making turbo-chargers that would actually stand up to service use in the 1930s and 40s wasn't all that easy. Even the US just pulled it out at almost the last minute for a mass produced item. 

It is the post war history of many of these weapons systems/engines/airframes that, while not developed with the urgency of war time, were developed _without_ significant material shortages, bomb damage/disruption, large labor shortages and other problems and often with German designers/technicians/scientists giving advice/guidance that makes be doubt the ability of the Germans to actually turn most of those drawings into working hardware in 1-2 years. Just to be clear I would doubt the ability of ANY nation to turn the sketches/drawings/prototypes into serviceable weapons in 1-2 years.


----------

