Optimize the Ju88 for speed

[wiking85]

Hmm - a Jumo 213A with turbocharger, and plenty of exhaust thrust, with GM-1 added for a good measure?? The writer of Wiki article smokes something bad
At any rate - tailoring a 420 mph bomber + Jumo 213 in 1935? Give it jet engines, I say

I was talking about the air frame, but using the numbers of its performance for a reference of the aerodynamics with high powered engines.

 

[Koopernic]

Thanks. I was thinking of making the wing slimmer, eliminating the flat sheet windows and nose in lieu of streamlined units, and making it as light as possible while increasing power. That would get you part way there, but then you'd need to make a slimmer overall fuselage.

We could work at it and maybe arrive at a solution ... maybe not. Doing it in wartime Germany should have been a top priority, but somehow it wasn't. The Do.335 didn't really fly until the end was a foregone conclusion. Germany never really HAD a stragetic bomber, and that was a big mistake.

If you are going to base your attack on quality instead of quantity, you'd better have the quality in-service when it is needed, and it wasn't. It as in work, and that's not the same thing. Also, it's tough to prevent the enemy from inventing the things you are working on all by himself, and there's no guarantee they won't invent something you haven't thought of.

The speeds of the various Ju 388 with various engine combinations are given in Black Cross Volume 2 Ju 288/388/488 and also Ju 388 by Vernalieken Handig. Basically the Ju 388J2 daylight zerstoerer with ventral gun pack and Jumo 222E/F was expected to reach 710kmh/441mph. With the single stage Jumo 222A2/B2 404mph, this engine had a full throttle altitude of 5000m, about 292 produced. The Jumo 222/A3 had a 6km full throttle height due to an improved supercharger and would have been faster. All variants had a power of 2500hp each.

The aircraft lost speed if radar was fitted or if the ventral bomb pack was installed it lost 15kmh or 10mph.

Ju 388 by Vernalieken Handig actually reproduces a letter between Adolf Hitler and Kurt Tank where Hitler asks tank for advice on whether the He 219 or the Ju 388 was better. Hitler is clearly seeking out a second opinion. Tanks reply was that neighter was suitable to deal with the Mosquito but that although the He 219 was faster he may as well go with the Ju 388 due to its versatility as neighter could deal with the Mosquito anyway. I presume this was after the Ta 154 was cancelled anyway.

I suspect the He 219 with Jumo 222E/F could deal with the Mosquito.

The 'thin wing' would tend to work if the power of the engines was enough to get close to 400mph in the first place.

The Germans did have their own home grown laminar flow technology, flown on the Me 309 in May 1942. Don't know how good it was but NACA laminar flow technology would have allowed a thick wing with a great deal of fuel capacity as well as low form drag, this then would have left more of the fuselage free for bombs. Of course the spar and the subdivided bomb bay would prevent this anyway unless other arrangements are made. A long flat ventral bomb pack seems to have been the solution and only cost 10mph.

Frankly the Do 217 impresses me more as a bomber: the Do 217M with only 1750hp DB603A had a speed of 347mph compared to the Ju 188A with 1750hpJumo 213A managing only 322mph. It had a decent bomb bay long enough to carry torpedos internally. It was considered underpowered but then the DB603 has such great scope for improvement. The Ju 88 series was probably only popular because such a large production system was already available and it could function well as a night fighter.

1941-1942 should have been a watershed year for the production of advanced types: the Me 210 should have replaced much of the the Me 110, Ju 88 and Ju 87 fleet. The Ju 288 should have begun replacing much of the Ju 88, He 111, Do 217
and the He 177 should have been debugged replacing many of the twin engine bombers as well as the Fw 200.

The He 177 should have been easiest save as the Heinkel firms owner, Earnest Heinkel had begged to develop a 4 separate engine version early enough but was at that time denied. Not much could be done about the DB606/610 engine problems or those of the Jumo 222. Both were essentially solved by 1944 but then it was too late.

When one considers the effort put into the He 219, Me 410, Ta 154, Do 335 these seems much effort for little result. Most of these aircraft only had a chance to be mature in late 1944 or early 1945 as engines improved.

 

[drgondog]

Two immediate 'fixes' - change the wing to lowest possible drag consistent with cruise performance and eliminate the dive bombing requirement as far as extra structural weight (add back to payload) - but the latter removes some inherent capability that made the Ju 88 so valuable and versatile.

The parasite drag due to the frontal area for the Ju 88 is not as significant with respect total drag as the overall parasite drag of the wing.

Move the Jumo 213 back in time.

Look to the Ju 188 and 288 for the available performance boosters that were acceptable to Junker engineers.

 

[tomo pauk]

...
Couldn't the existing wing configuration still have allowed for the ability to carry some larger bombs (even if not using the space as efficiently), or at least allow for that if it was planned for from the start? (that and adopting a bulged bomb bay for special heavy bomb runs like the Mossie did would make more sense than using external racks)

And embedded radiators might work, but also take up wing space and increase vulnerability. (the compact annular configuration limited vulnerable engine area considerably on top of being relatively efficient weight/bulk/drag wise) Granted, the lack of pressurized cooling systems on the early Jumo engines means larger radiators for similar cooling capacity. (optimized annular radiators on contemporary DB-601s should be less)

If we loose, say, 10 km/h due to installation of bomb tray, and another 10 km/h without going to wing radiators than we're getting away from a Ju 88 optimized for speed. The radiators don't have to be fully buried, they can be arranged in Mosquito-style in front of the spar. Even the fully buried radiators on the Pe-2 and predecessor of the Tu-2 don't look like to great a waste of internal space.

There's a reason most late-war adaptations of DB-603s and Jumo-213s used similar arrangements.

Every installation is a trade-off. The power egg installation allows for a fast engine installation removal. A more 'convoluted' radiator installation can buy some speed, at cost of weight and vulnerability.

 

[olbrat]

what if there was industrial espionage and germany obtained the plans for the merlin/peregrin/vulture series to develop? A lot of horsepower available.

 

[tomo pauk]

Peregrine don't bring anything for the Germans, power is too low. Vulture - the Jumo 222 was a similar engine, both were having issues of their own. Merlin without plenty of C3 fuel to burn does not bring much for the Germans either.
What could/should be copied is the RR 2-stage supercharger inter-cooler set-up - it was simple efficient, and a clone of it coupled with big displacement engines will yield plenty of power at altitudes.
Worth copying is also the radial compressor set-up for the jet engines, though the Germans have had something similar?

 

[dedalos]

Germany did not have High octane fuel,neither Special alloys. It would be always behind in engine power.They should sacrifice airframe size and weight
The Bf 110 should be replaced by single Seat Fw187 in the heavy fighter role
The Ju 88,He111 should be replaced by Me 410C as medium bomber and night fighter
The He 177 should be replaced by Do 217K with DB610s or ju288 with DB610 s in the role of heavy bomber
The smaller airfames mean less equipment,less bombs(not much), less range but provide much more speed(=life), less fuel consuption and require less raw Materials to build

 

[Shortround6]

Germans cannot use the boost the British did without different fuel AND lowering the compression ratio used and accepting worse fuel economy. Even then you have a power to weight problem. Why did the Griffon weigh as much as it did? To be strong enough to handle the power it was making. The Buzzard was the same bore stroke yet hundreds of pounds lighter.

 

[GregP]

Hi Kool Kitty,

I didn't want to design a new aircraft, I was making suggestions. Coming up with a real new design is enough work for an aeronautical engineer for 3 - 8 months or more ... all for no pay if it isn't going anywhere but to a fourm ... and I'd get second-guessed every third line as usual.

I can make some informed suggestions, but the real-life design would be a job nobody is getting paid for. Today, if I had a Ju 88, I'd restore it stock due to historical significance. Back then, coming up with a new plane would have been a national necessity had I been a Germany aircraft designer.

 

[Koopernic]

The new location of spar attachment points would not interfere with crew placement, since those points would still be at Fuselage Rib 9 and 12. The spar attachment points are numbered 11 here:

View attachment 287693

With high wing location, the unrestricted bomb bay would be spanning between ribs 9 and 15.

snip

Burdening the aircraft with additions, like Bola weapon station, external payload with racks, ever bigger wing and sometimes fuselage certainly cuts the performance; not just speed but also range/radius. Hence my proposal to keep the wing at 50 sq m, internal bomb bay etc. Such a clean and not too big an aircraft would be a better performer than historical Ju-88.
When it's about the engines, the BMW 801 would make a lot sense here, at least for a part of Ju-88 production.

Good work, with the wing now mounted higher, the undercarriage a little longer and heavier but we can now efficiently carry bombs internally. With a higher penetration speed fewer Ju 88 are intercepted and even if intercepted are exposed for shorter periods to hostile fire. Fuel capacity is down but partially compensated by the greater practical speed. There are two broad remedies move more fuel to the wing stations or make drop tanks a standard feature.

 

[Milosh]

Germany did not have High octane fuel,.....

I understood C3 had a PN of at least 140. That is wrong?

 

[Shortround6]

It depends on when. Apparently C3 changed as the war went on. While it reached a PN of 140 in 1943 (maybe earlier?) in earlier years it was rated somewhat lower. Some sources claim two different performance levels and others claim more than 2 levels. One paper showing analysis of fuel in captured/crashed aircraft has a wide variety of numbers. By date of test the trend is definitely upward.

I may going way out on a limb but since the Germans did not have a performance specification (at least not one listed in common references) but rather a specification (at least in common references) that listed allowable mixtures of groups of compounds the actual performance of the fuel may have varied from batch to batch. While C3 could contain not more than 45% aromatics there are over a dozen different aromatics (a couple rather useless for liquid fuel) all with different PN numbers or affecting the PN differently. Since the Germans tended not to push boost limits too much it may not have made a lot of practical difference ( and as the P-38 fuel argument shows, even fuel with a specified PN number limit can vary in other characteristics.)

 

[kool kitty89]

Frankly the Do 217 impresses me more as a bomber: the Do 217M with only 1750hp DB603A had a speed of 347mph compared to the Ju 188A with 1750hpJumo 213A managing only 322mph. It had a decent bomb bay long enough to carry torpedos internally. It was considered underpowered but then the DB603 has such great scope for improvement. The Ju 88 series was probably only popular because such a large production system was already available and it could function well as a night fighter.

The 217 does seem a better overall aircraft than the attempted Ju-88 successors. The Ju-88 itself had the advantage of being somewhat smaller and more adaptable to non-bombing roles.

Had the successors to the Ju-88 been more of a further streamlined replacement ... closer to say the Me-410 but more bomber-optimized and no intent for its use as a day fighter, than it might have been more interesting. (as it was, modification of the basic Ju-88 design seems more worthwhile than the existing Ju-88 successors)

The He 177 should have been easiest save as the Heinkel firms owner, Earnest Heinkel had begged to develop a 4 separate engine version early enough but was at that time denied. Not much could be done about the DB606/610 engine problems or those of the Jumo 222. Both were essentially solved by 1944 but then it was too late.

Yes 4-engine and drop the dive bombing requirement. Being more conservative in engine target would be smarter though. Something able to make do with 4 Jumo-211 or 601/605 engines but able to accept the heavier more powerful 801, 603, and 213 would have been ideal in terms of practical utility and growth potential.

When one considers the effort put into the He 219, Me 410, Ta 154, Do 335 these seems much effort for little result. Most of these aircraft only had a chance to be mature in late 1944 or early 1945 as engines improved.

What about the Fw-187 and Ar-240? Earlier designs than most of those, and generally better than the Me-210/410 given the engine power available to it. The handling issues may not have been solved for the existing development period, but supporting the Me-210 over the 240 prevented that sort of development.

Either way, as a heavy fighter, the Fw-187 was a much more shurefire winner without the performance and complexity issues plaguing the 240 or 210. (but not a replacement for the Ju-88)

Good work, with the wing now mounted higher, the undercarriage a little longer and heavier but we can now efficiently carry bombs internally. With a higher penetration speed fewer Ju 88 are intercepted and even if intercepted are exposed for shorter periods to hostile fire. Fuel capacity is down but partially compensated by the greater practical speed. There are two broad remedies move more fuel to the wing stations or make drop tanks a standard feature.

That also fits in with the Ju-88 being a better, faster replacement to the Do-17 ... high wing configuration employed there too, and also the intention of having a lighter defensive armament than the Do-17 (or none). No need for the bulged rear canopy or space for added gunners/observers.

If we loose, say, 10 km/h due to installation of bomb tray, and another 10 km/h without going to wing radiators than we're getting away from a Ju 88 optimized for speed. The radiators don't have to be fully buried, they can be arranged in Mosquito-style in front of the spar. Even the fully buried radiators on the Pe-2 and predecessor of the Tu-2 don't look like to great a waste of internal space.

Yes, a Whirlwind or mosquito-like configuration might have been worthwhile there too, though using wing root extensions like the Mossie did might have been difficult combined with the high wing placement. (either way, the DB-601 should have favored smaller radators than the contemporary early Jumo 211)

 

[kool kitty89]

Not sure if this is more relevant here or in the recent Fast Bombers Again thread, but the Do 215 hasn't been addressed in either of those discussions.

Internal bombload was more limited than the Ju 88, but did the high wing configuration allow for larger bombs to be carried or any more efficient use of space at all?

Did the Do 215 benefit from less aggressive RLM requirements for added capabilities than the Ju 88? (it seems to have performed better in spite of being based on an older design and having a larger wing area; the lower weight seems to be the main advantage)

 

[mhuxt]

I have some C3 analysis stuff, can't get it to upload - board times out.

I dunno, past three months I've had trouble getting the page to load, on both home and work computers.

 

[tomo pauk]

Mark - maybe you would upload it to mediafire or the like?

Re. Do-215: max bomb caliber for the Do 17/215 was 2 x SD-250 for internal carriage (one behind another). Max weight seem to be 8 x SC-100 bombs, though there are some sources that list max bomb weight of 1000 kg.
The greatest speed figure for the Do-215 (with DB-601A) I was able to find is 465 km/h at 4800 m.

edit: seems it was 4 x 250 kg in 'main' versions of the Do-17 (the He-111 carried 8 x 250 kg internally, for example):

 

[kool kitty89]

Mark - maybe you would upload it to mediafire or the like?

Re. Do-215: max bomb caliber for the Do 17/215 was 2 x SD-250 for internal carriage (one behind another). Max weight seem to be 8 x SC-100 bombs, though there are some sources that list max bomb weight of 1000 kg.
The greatest speed figure for the Do-215 (with DB-601A) I was able to find is 465 km/h at 4800 m.

edit: seems it was 4 x 250 kg in 'main' versions of the Do-17 (the He-111 carried 8 x 250 kg internally, for example):

Wikipedia cites Dornier Do 215 - Wikipedia, the free encyclopedia for 506 km/h at 4,500 m. But that could be at a lighter weight. So it might have been slower than the Ju-88A1 depending on the configuration.

Being able to carry 4x SC-250 would have some advantages over 14x SC-100. (without resorting to external racks)

 

[mhuxt]

Another try.

 

[mhuxt]

View attachment BIOS-119.pdf

Sorry no appendix 2, think I have the info, but in German.

 

[Shortround6]

Thank you.