Four-engined Junkers 288? <delurk>!

[ktank]

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]

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]

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

 

[Capt. Vick]

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

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

 

[wiking85]

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]

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]

That's exactly what Focke-Wulf proposed doing with the Fw 191 when they put forward the Fw 191C (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]

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]

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]

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]

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]

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.

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]

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.

 

[tomo pauk]

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.

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]

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]

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]

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]

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]

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]

"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.