Could you have designed a better Warbird?

davebender said:

I agree.

If Japan wants the Ki-61 program to be successful they must sink some serious money into facilities for manufacture of the DB601 engine and it's sub-components. ...

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There were several major problems for the Japanese in building an engine based on the DB 601.
Firstly, they had not previously used an aero-engine with roller bearings. The roller bearings came from DB's history of designing engines for motor racing and are better for going suddenly to full power from idle at a race start. However, late DB 605s went to shell bearings for ease of manufacture. The problem was that Japanese crankshaft pins could not survive the distortions caused by the roller bearings as they rotated. There is a photograph (Photo 38-3) of the wear in "The Romance of Engines" by Takashi Suzuki. He notes "On the otherhand, when observing the structure of the carburized area, the German Benz crankshaft has a neat Martensite structure (indicating satisfactory quenching). The Japanese engine crankshaft shows precipitation of troostite, which indicates inadequate quenching (Photo A38-2)."
Secondly, although the Japanese had obtained two licences to build the DB 601 (Army and Navy separately), Bosch had refused to supply tools to build the fuel injectors. Thus Japanese fuel systems were either frequently defective (from Kawasaki for the Army Ha 40) or hand built and rare (from Mitsubishi for the Navy).
Thirdly, as noted by Dave, the design of the DB 601Aa was copied rather than the redesigned DB 601E with repositioned plugs and changed valve timing to allow 2800 rpm.
Finally, what if the Japanese had copied a Mustang radiator for the Ki-61 (assuming skilled espionage)?

several major problems for the Japanese in building an engine based on the DB 601.

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I agree. So Japan must count the cost before choosing this option. Building a poor copy of the DB601 engine is simply a waste of money.

On the other hand....
The DB601 / DB605 was an excellent WWII era aircraft engine. If Japan spends the money to produce a reliable copy it could power more aircraft models then just the Ki-61.

Interesting thread. There's obviously some very knowledgable people here, well versed in aircraft specifications and performance. I doubt I could design a 'better' aircraft (in quotes because 'better' could be defined different ways). But I do like the canard style designs that appeared later on, like the Kyūshū J7W1 Shinden.

But I would challenge the idea that having a better performing aircraft was all that was important. Yes, aircraft design certainly was important. But personally, I think some of the biggest factors in any WWII aircraft design weren't about the performance of the aircraft alone, but the overall cost, component availability, build time, and the tactical philosophy behind the design. It wasn't always about having the best aircraft, but more that the aircraft was easily produced, reasonably protected the crew, and met a critical need. A great example being the Hawker Hurricane. In my opinion, many could easily design a better performing aircraft, but I doubt very few could have designed an aircraft that better met the needs of the RAF at that time.

The Japanese had some wonderful aircraft, that met their tactical philosphy. But their philosophy was inferior. They didn't protect their pilots well. They fought in a 'lone warrior' style reminiscent of samurai, instead of emphasizing team work. They used their most skilled pilots in action instead of pulling them back to use their expertise in training new pilots. The Americans did exact the opposite, and the difference showed.

Leif

davebender said:

I agree. So Japan must count the cost before choosing this option. Building a poor copy of the DB601 engine is simply a waste of money.

On the other hand....
The DB601 / DB605 was an excellent WWII era aircraft engine. If Japan spends the money to produce a reliable copy it could power more aircraft models then just the Ki-61.

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I hope that we are not hijacking this thread and turning it into a history of Axis failure to cooperate. Searching the internet seems to find many versions of "In March 1938, Kawasaki signed an agreement with Daimler-Benz of Germany for obtain manufacturing rights to the liquid-cooled inline engines then under development by the German firm. In April 1940, a Kawasaki engineering team visited Daimler-Benz in Stuttgart to obtain plans and samples of the DB 601A engine, then being used in the Me-109" which is taken from Kawasaki Ki 61 Tony. The question is why did they waste two years? I suspect that one problem would have been how the Japanese were going to pay the Germans. Japan had little foreign currency and neither had fully convertible currencies. Thus they probably had to negotiate a barter deal possibly involving soy beans from Manchuria. The other issue would have been futile negotiations over the fuel injection system and perhaps also the electrical equipment. All the prototypes of the Ki-60 were powered by imported DB-601 engines and those of the Navy's D4Y by imported DB-600 engines. The prototype of the Ki-61 in December 1941 may have been the first real use of a Japanese built engine. There would have been two consequences from the delay in producing the engines. Firstly, without engines there was little pressure to rush aircraft development. This did have some good consequences as three He-100s arrived in Japan and some ideas were incorporated in the Ki-61's structure. Secondly, without running Japanese built engines, it was impossible to find the problems such as those involving the crankshaft pin. Had a Ha-40 been available for a prototype in December 1939, it seems likely that testing would have led to a design with shell bearings for 1941 production which would have been much more reliable.

Clearly other German developments could have been incorporated. I am not sure when the DB 601E influenced the development of Japanese engines. As a DB 605 was delivered to Japan, it should have influenced the Ha-140 at least. The Ki-61's radiator design could have been improved if Günther Bock's lecture boundary layer | transition point | drag coefficient | 1942 | 0665 | Flight Archive had been passed to Kawasaki. Perhaps, it was necessary to combine the oil and coolant radiators to actually generate useful thrust?

I think this is the crux of the problem.

Prior to the start of WWII in Europe Japan could import production tooling and technical experts from Germany. That must happen before September 1939 if Japan is to have a reliable copy of the DB601 engine. Otherwise Japan should forget the entire project.

Does some one want to tell us WHEN the DB601 was demonstrated to be a RELIABLE mass production engine?
As a known quantity rather than predictions or promises.
How many months do the Japanese have to make up their minds and considering their options ( how many PROVEN liquid cooled V-12s were there in the world in 1938/39?) I think it was more a case of take what they could get and hope it worked out.
Considering the trouble with early Merlins, Vultures, Peregrines, Griffions, Bristol sleeve valve engines, the Napair Sabre, it took a lot of faith in many cases to sign onto a new engine. Sometimes it worked and sometimes it didn't.
If the Japanese could see into the future well enough to predict that they couldn't build the DB 601 then they should be able to see that they couldn't win the war either.

I made some changes in Me 155E:


And I made a fighter-bomber/recce/night fighter a/c for the Axis:

It's powered by 2 DB603's, radiator air intake is like in Mosquito (in the wing):

Armament is 6xMG 151/20s

and 4 SC500 bombs.

Canopy is based on He 219:

Tail section and aerodynamical concept comes from Ki-83:




Regards

In every case of airframe design, the proposals that ended up as production fighters served a purpose aligned to the national 'mission' and belief systems regarding tactics and applications of airpower.

Had the design criteria for Germany been for an air superiority fighter capable of escort to say 400 mile radius in 1935, the Me 109 would not have been the choice, nor would such capability of performance and range been considered practical with a single engine fighter with the aerodynamics and engines of the day. The Fw 189 may have had a different historical perspective

Had the Japanese doctrine been built around strategic bombing in daylight at high altitude, the design of the Zero would have been compromised to achieve high altitude performance with an engine not yet on their drawing boards... or relegated entirely to the naval version to support air superiority and escort at medium altitudes for both land based and carrier based aircraft.

Was the Mustang a lucky accident, a combination of the excellent aerodynamics of both airframe and wing, along with a predisposition for placing ALL of its fuel in the wings? But even if it had been originally designed with the Merlin instead of Allison, would the USAAF been overwhelmed with its capability given the belief by Arnold, Eaker, Spaatz, etc that the B-17 and B-24 did not need long range escort?

The DB601-605 and the Merlin were the only two in-line designs available in 1938-1943 with both the foundation and growth potential to surround with a high performance, light weight, airframe for a single engine fighter... capable of 0-35K high performance.

The wonderful radials required turbo-supercharging and the fuel and materials to match the above two in-lines above 20K - at a consequential penalty in drag and weight - to mate the engine and supercharger to the airframe, until the very late dash numbers of the R-2800 and BMW801s became available.

So every discussion regarding 'improvement' usually focus on some engine swap for an existing airframe. The discussions I have seen that venture to airframe mods with same basic engine packages (like a 'twin' Me 109) usually ignore the delicate trade offs between additional airframe weights and increased drag to a potential performance gain without specifying why the modification is made?

If you re-arrange a wing to take more fuel, you basically redesign a wing from scratch, increase the structural weight to accomodate the fuel cells, decrease performance for same power.

If you add fuel to the fuselage you frequently must change the dimensions (and weight) and re-arrange relationships between epennage and wing to account for stability issues.

If you dramatically increase horsepower, re: existing structure - particularly the rudder size and aft fuselage carry through structure needs to be beefed up - or manuever limits imposed (a la Mustang P-51B/D)

Everytime you add metal to the solution, you increase drag. Everytime you add fuel you lose certain intrinsic manuever performance. One of the great airframes (the Mustang) did Not improve handling qualities as it morphed - until it was basically re-designed from the ground up to lengthen the tail to aero center of lift, shift fuel tank capacitites, and lighten the airframe back to nearly the P-51A weights.

Shortround6 said:

Does some one want to tell us WHEN the DB601 was demonstrated to be a RELIABLE mass production engine?
As a known quantity rather than predictions or promises.
How many months do the Japanese have to make up their minds and considering their options ( how many PROVEN liquid cooled V-12s were there in the world in 1938/39?) I think it was more a case of take what they could get and hope it worked out.
Considering the trouble with early Merlins, Vultures, Peregrines, Griffions, Bristol sleeve valve engines, the Napair Sabre, it took a lot of faith in many cases to sign onto a new engine. Sometimes it worked and sometimes it didn't.
If the Japanese could see into the future well enough to predict that they couldn't build the DB 601 then they should be able to see that they couldn't win the war either.

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Good question!! According to Wikipedia, the DB 601 was first run in 1935, 150 were ordered in February 1937 and production began in November 1937. The source given was in Russian, so that trail went cold for me. Two Bf 109s powered by DB 600s had taken part in an international meeting at Zurich in July 1937 but the Bf 109D in production in 1938 were still powered by Jumo 210s (AFAIK as sources differ). Thus even the DB 600 may not have been available in quantity in 1938 although there seem to have been enough DB 601s to power a range of prototypes (Bf 109s, Bf 110s, Bf-162s and He 111Gs with the last in airline service). However, according to "Aeronautical research in Germany: from Lilienthal until today", Volume 147, Ernst-Heinrich Hirschel, Horst Prem Gero Madelung (Springer, 2004, ISBN 354040645X) page 212, the DB 601 Re III was supplied to both Messerschmidt and Heinkel in Spring 1938 and gave 1660 hp. Thus, although production of the DB 601 was not exactly racing when Kawasaki signed the initial agreement, it may have been clear that the basic design could survive for 5 minutes under higher load and at faster rpm. It is also quite clear that by early 1939, reliable engines were being mass produced for the Bf 109E. Thus there was at least one wasted year.

Shortround6 said:

....
If the Japanese could see into the future well enough to predict that they couldn't build the DB 601 then they should be able to see that they couldn't win the war either.

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They should have been able to see that it would be much easier with blueprints and tools for the Bosch components (i.e. the fuel injection and electrical systems).

WHEN the DB601 was demonstrated to be a RELIABLE mass production engine?

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During August 1938 DB601 production at Genshagen reached 200 engines per month. So I think the Japanese knew what they were getting when they signed the license agreement.

P-51 got accolades for it's merits, with only shortcoming being it was initially powered with engine ill suited for higher altitudes. Let's say that during the talk between Brits and NAA someone proposes installation of Merlin XX 'stead of V-1710 (so P-40 remains Allison-only plane), and the deal is on.
So the RAF tests the Mustang prototype during winter 1940/41, and the brass is stunned that new fighter is considerably faster then beloved Spitfire, even faster than the brand new Mk.V. And that is with pretty low boost settings (10% less power than Mk.V), 20% greater weight and provision for huge fuel load.
As they boosted engine like the one in Hurricane II, another 20 mph were achieved, and climb rate also went up. Sure enough, RAF orders 500 Mustangs, with increased boost, of course. Those started to arrive in late 1941, to be used in mid 1942. Reign of Fw-190s and Bf-109Gs is stopped cold before it started.

But, everybody is not excited that RAF uses 420 mph plane, not even on allied side...

The 1st one's are at UK.
People at Supermarine will not allow that easy their bird is out-flown by an imported one, so they decide to take a look at the features of Mustang. After a while, the engineers agree to design a new wing, with enough space for fuel tanks, inward retracting U/C and a pair of cannons. The resulting Spit Mk.VIII really doubles the combat range vs. Mk.V, and it's performance is almost same as of Mustang.
In order to go one better than the American, they start to test the new two-stage supercharged Merlin with the new airframe. The plane clocks 440 mph, combat ready. Called Mk.IX, it's produced along the Mk.VIII.

Sidney Camm looks carefully onto Mustang too. The thing is better performer then his Typhoon. So he too takes a second look at Tiffie, whose prototype is only as fast as Mustang, despite 50% more power. He is angry at himself for going with tick wings for the plane, while beard radiator doesn't look that clean either, so it's back to the drawing board.
Finally, the new Typhoon prototype is flown in late 1941. It has thinner wings now (but of greater area, so the fuel and ammo are not reduced), and, leading-edge radiators for the powerful Sabre. When Sabre performs as advertised, new Typhoon outperforms the American. When thrown in combat in late 1942, the only thing that can kill Tiffie pilot is his own plane...

Some folks back in the USA are not happy either. At Curtiss, for example. Their P-40 is looked as a better Hurricane, not as the competitor in class of Spitfire, 109, or the new plane from NAA. And now, in 1941, that new plane steals their orders. So they set to improve the -40.
Since the Packard Merlin was no available, ditto R-2800, they opted for next one that was - their own R-2600. Armament was 4 HMGs in wings, and dorsal fin was added for increased stability. The resulting plane 1st flies on Dec 6th, 1941. The usage of 'bomber engine' hampers performance above 15K. RAF acquires the plane, using is as a bomber. OTOH, Russians equip their fighter squadrons with it. Australians too.
Curtiss now pushes for true 2-speed supercharged R-2600, so, in late 1942, things improve. With 390 mph at 15K, disadvantage vs. competition is thin, as noted during the Battle of Kursk.

tomo pauk said:

Curtiss now pushes for true 2-speed supercharged R-2600, so, in late 1942, things improve. With 390 mph at 15K, disadvantage vs. competition is thin, as noted during the Battle of Kursk.

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2 speed or two stage?

those A-20 and B-25 engines were 2 speed.

low gear peaked at around 4500ft and high gear at around 12,000ft.

Indeed, I was thinking about 2-stage

Now, let the man with too much spare time continues

Though not very keen on the new fighter from NAA (since they have two world beaters in the pipeline - P-38 P-47), USAAC did not pass on the opportunity to test the Mustang in fall 1941. While new fighter was slightly slower then P-47 P-38 prototypes (while outclassing the similar-sized P-39 -40), it's rate of climb was better than of those two.
The best thing for the new fighter was the affordability - almost 2 per each P-38 could be bought, and 3 for each 2 of P-47s. So, after much discussion, USAAC orders Mustang (called now P-51), but it will wait 'till production ramps up. The 1st US squadrons go to combat in early 1943 in MTO, and in summer '43 in ETO. With drop tanks.

Not so fast, say people at Allison, when their product gets expelled from Curtiss. They set to the task of developing a two-speed supercharger set for the V-1710. Engine develops 1400 HP, and it's useful at high altitudes. Taking advantage the Packard Merlins are still in short supply (plus RR gets royalities for each produced), they manage to have it installed in P-51. The new version, P-51B, is in usage from summer 1943.

Can you put together a similar what-if chain of events for the P-38?
British order initial batch with Merlins as you suggest for P-51.

Go for it!

(I'll bite... or not)

Don't think Brits were eager to buy half of fighters with money they had. Plus, having Merlins in quantity in 1941 was not as easy as in, say, 1943 or 44.

gjs238 said:

Can you put together a similar what-if chain of events for the P-38?
British order initial batch with Merlins as you suggest for P-51.

Go for it!

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For what ever perceived faults the Allison had it got better fuel economy than the Merlin.
Plus the two stage supercharged Merlin 61 ( or V-1650-3) doesn't show up until mid 1942 and then only handfuls. In fact the 10th two stage V-1650-3 doesn't leave the factory until May of 1943.
There were three different paper studies of Merlin engined P-38s. In no case was it estimated that the Merlin Version would have a significant performance difference than the turbo Allison. And in some cases whatever speed or climb benefit there was was balanced by an 8-30% loss of range depending on which Merlin was being compared to which Allison.