Four-engined Junkers 288? <delurk>!

[rinkol]

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]

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]

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]

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]

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 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]

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.

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]

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]

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]

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]

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]

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

 

[Shortround6]

"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.

 

[Koopernic]

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]

Double post

 

[Koopernic]

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]

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.
snip
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.

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]

...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]

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]

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?

 

[Koopernic]

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.