WI: alternative IJA fighters

[tomo pauk]

Unlike the IJN, the IJA was fond to readily adopt new fighters almost on yearly basis after ~1940. For good reasons - the Ki 43 was not well armed, nor fast (level flight nor in dive), nor it was known to be tough; Ki-44 have had high wing loading and still was not stellar with firepower; Ki-61 was plagued by engine problems, ditto for Ki 84. Ki-45 was too many cylinders for too slow speed and, initially, weak armament; other 2-engined types were too late.

So - how would've the IJA fighters developed with less issues? The engine types are the ones historically made in Japan, though you can alter the production of engines (in a timely manner, of course) in order to have enough of desired types made for the newly-fanged fighter force. Starting date is, say, 15th November of 1940 - the Ki 43 is in pipeline for production, and you can have some feedback from Germans. Note that Japanese economy can't support the gazzilion of engines & whole aircraft someone might intend to whip up here, so plan accordingly.

 

[cherry blossom]

The first Ki-46 III was delivered in December 1942 with the Ha-112 II (Kinsei 60 series) engine. Thus it is possible that the first Ki-100 could also have been delivered in December 1942. The requirements are that the IJA learns about the cowling arrangement of the Fw 190 earlier and that production of the Ha-112 II builds up quicker, which requires that the fuel injection system is mass produced earlier.

Now we start to cheat on your requirements. The raider Komet arrived in Japan in about November 1940 German auxiliary cruiser Komet - Wikipedia but obviously left Germany earlier on the 3rd July 1940. There were no prototypes of the Fw 190 available to be sent in July 1940 but the V5 had flown with the BMW 801. Full details of the installation with drawings and photographs could have been placed on Komet together with details of how to build the fuel injection system (the details that Bosch had refused to supply as part of the DB 601 licences). The deal is no aircraft data and Komet gets no fuel. Germany would perhaps have been willing to send sensitive data on a warship that it would not have allowed to travel through the USSR by train.

If the IJA tests the Ki-61 and the Ki-100 (which will have a different name) in 1942, they will chose the Ki-100 and it will be their main fighter by late 1943. This won't change too much but will make life difficult for the P-40 equipped units of the USAAF.

 

[Shortround6]

Put a normal size wing on the Ki-44 and perhaps extend the fuselage a bit. Might be 10-15mph slower than the real Ki-44 but could be built/changed at the same time scale as the Ki-43.
Put the 12.7mm Mg in each wing and the 7.7mm guns in the cowl to start, change to 12.7mm guns as supply allows. By 1943 end production of the Ki-43 and build as many big wing Ki 44s as you can. Fit the 20mm Ho-5 when it becomes available. Perhaps fit ejector exhausts?

 

[Hardrada55]

Nakajima should have mounted the Nakajima "NLF" inverted V-12 engine being developed from 1938-39 in the 1942 Ki-43-II Oscar fighter. Nakajima NLF(B9) LiV-12 950@2700rpm@t/o to 1780m; 940hp@2700rpm@3650m 1938-40 140x150 27.7L 1689.7ci; 6.5/1 1027x737x? 495kg; 1938-39

 

[DarrenW]

To me it seems that engines where the Achilles heel of Japanese fighter design. Only Mitsubishi was capable of producing a quality aero-engine but output power always seemed subpar when compared to allied designs of the same period.

As with the DB 601A, did the Japanese ever consider a licensed built BMW 801 engine? I also wonder if they just purchased German and Italian manufactured DB 601As from the start there may have been less maintenance issues in the field. Did the axis powers have the industrial might to provide this for Japan in the early war years?

 

[tomo pauk]

Put a normal size wing on the Ki-44 and perhaps extend the fuselage a bit. Might be 10-15mph slower than the real Ki-44 but could be built/changed at the same time scale as the Ki-43.
Put the 12.7mm Mg in each wing and the 7.7mm guns in the cowl to start, change to 12.7mm guns as supply allows. By 1943 end production of the Ki-43 and build as many big wing Ki 44s as you can. Fit the 20mm Ho-5 when it becomes available. Perhaps fit ejector exhausts?

Hmm - the Ha-41/109 powered Ki 60/61 airframe?
Indeed, the Ki 43 needs to be phased off as soon as possible.

To me it seems that engines where the Achilles heel of Japanese fighter design. Only Mitsubishi was capable of producing a quality aero-engine but output power always seemed subpar when compared to allied designs of the same period.

As with the DB 601A, did the Japanese ever consider a licensed built BMW 801 engine? I also wonder if they just purchased German and Italian manufactured DB 601As from the start there may have been less maintenance issues in the field. Did the axis powers have the industrial might to provide this for Japan in the early war years?

The Ha-41/109 series provided about the same power as BMW 801C (87 oct fuel, 'low speed' S/C) or the de-rated BMW 801D (100 oct fuel, 'hi speed' SC, higher compression), with smaller weight and size, and with far better reliability. Without 100+ oct fuel, BMW 801 probably does not have the appeal for the Japanese.

At any rate, I'd veto the Kawasaki attempt to licence manufacture the DB 601 - they were already making Nakajima radials under licence, have them make Ha-41/109 series of engines instead of DB 601/Ha-40. My idea for fighters will probably be:
- 'medium size' for mid-1942 on - dimensions of Fw 190, with alternative engines (Kinsei, Ha-41/109)
- 'bigger size' for late 1943 on - size of P-51 or F8F, again with alternative engines (start with Kasei, switch to Homare and then to Ha-42)

 

[DarrenW]

The Ha-41/109 series provided about the same power as BMW 801C (87 oct fuel, 'low speed' S/C) or the de-rated BMW 801D (100 oct fuel, 'hi speed' SC, higher compression), with smaller weight and size, and with far better reliability. Without 100+ oct fuel, BMW 801 probably does not have the appeal for the Japanese.

But even without C3 fuel wasn't there more potential horsepower with the BMW 801 when one considers water injection? And I was unaware that the BMW is considered to have been less reliable than the Nakajima engine but I'm still learning. Can you possibly elaborate on this?

 

[tomo pauk]

But even without C3 fuel wasn't there more potential horsepower with the BMW 801 when one considers water injection? And I was unaware that the BMW is considered to have been less reliable than the Nakajima engine but I'm still learning. Can you possibly elaborate on this?

On 87 oct fuel, the BMW 801 was making 1560-1600 PS, vs. Ha 109 making 1440-1520 on 91 oct - not much of advantage for an 1/3rd heavier engine? Germans were experimenting with BMW 801 using C3 + water injection, that was never implemented in service. The 'simple' overboosting being much more elegant solution, and WI not giving too much of extra HP? I am not aware of Ha 109 being used with water injection, though, ditto for BMW 801 being run on 87 oct + WI.

Before the Homare, Japanese radials were working well, the only problematic type I know were the sub-variants of the Kasei that featured extended prop shaft & case. In Allied hands, even the Homare was working well, so it's problems were probably due to the late-war Japanese fuel being close to 87 than 91-92 oct, production & raw materials issues, questionable maintenance in the field etc?
On the other hand, problems with BMW 801 in the 1st 12-15 months of service use were such that it was a threat not just that the whole BMW 801 program was to be cancelled, but also the Fw 190. Problems are taked about at Calum's video.

 

[Gen. MacArthur]

You also have to look at how the Japanese designed their planes in the late 30's. They wanted highly maneuverable planes. This caused the planes to be extremely lightweight. So, when the heavily armed American planes learned to bounce the Japanese planes, the A6m, Ki-43 and Ki-44 had to adapt to high altitude fighting, vs. low and slow turn fighting. They were not designed for high altitude.

 

[DarrenW]

I am not aware of Ha 109 being used with water injection, though, ditto for BMW 801 being run on 87 oct + WI.

Oh, I thought the maximum power rating for the HA 109 was achieved with water injection. My mistake. And because this is a 'what if' type thread I mentioned using MW50 as a way to possibly improve the output power of the BMW 801 without 100 octane fuel. Didn't the BMW 801D using C3 fuel experience a 300 hp increase with the addition of water injection?

On the other hand, problems with BMW 801 in the 1st 12-15 months of service use were such that it was a threat not just that the whole BMW 801 program was to be cancelled, but also the Fw 190. Problems are taked about at Calum's video.

I'll have to view Calum's video one evening when I have more time to fully digest the information.....Thanks for the link!

 

[tomo pauk]

Oh, I thought the maximum power rating for the HA 109 was achieved with water injection. My mistake. And because this is a 'what if' type thread I mentioned using MW50 as a way to possibly improve the output power of the BMW 801 without 100 octane fuel. Didn't the BMW 801D using C3 fuel experience a 300 hp increase with the addition of water injection?
...

The increase of HP via C3 fuel was gradual, there was barely increase of power when the de-rated 801D was compared with 801C. The fully-rated 801D initially was not that much more powerful than the 801C that run on 87 oct fuel, perhapss extra 130 HP in 1st gear. The actual increase of power, either via C3 injection (that doubled as MW 50) or via 'simple' overboost, was perhaps up to 200-300 HP by late 1943, depending on altitude and S/C gear. The later power increase was possible due to the C3 fuel being perahps as 'good' as the Allied 100/130 grade.
The B4 + MW50 stands out as interesting choice for BMW 801 engine, however I don't think the Germans went with that beyond test bench. Not even the results with C3 + MW 50 were stellar ones, barlely reaching 1.5 ata of boost down low - perhaps 200 HP extra vs. 'normal' max boost of 1.42 ata?

This article notes several problems experienced during MW 50 tests on BMW 801D, that were not cured during the short tests. Among them corrosion was noted. Speed increase was 16 km/h at SL.

 

[fastmongrel]

I don't know enough about Japanese Army fighters to make a definite comment but I have always liked the Ki-100. If this aircraft had been built from the start with a radial rather than slapped together in a crisis it might have been the best Japanese fighter of all.

Certainly the initial batch of high back aircraft were a handsome beast.

 

[DarrenW]

The increase of HP via C3 fuel was gradual, there was barely increase of power when the de-rated 801D was compared with 801C. The fully-rated 801D initially was not that much more powerful than the 801C that run on 87 oct fuel, perhapss extra 130 HP in 1st gear. The actual increase of power, either via C3 injection (that doubled as MW 50) or via 'simple' overboost, was perhaps up to 200-300 HP by late 1943, depending on altitude and S/C gear. The later power increase was possible due to the C3 fuel being perahps as 'good' as the Allied 100/130 grade.
The B4 + MW50 stands out as interesting choice for BMW 801 engine, however I don't think the Germans went with that beyond test bench. Not even the results with C3 + MW 50 were stellar ones, barlely reaching 1.5 ata of boost down low - perhaps 200 HP extra vs. 'normal' max boost of 1.42 ata?

This article notes several problems experienced during MW 50 tests on BMW 801D, that were not cured during the short tests. Among them corrosion was noted. Speed increase was 16 km/h at SL.

Excellent information Tomo, thanks for explaining things so concisely like that. So basically what you're saying here is that the BMW 801 was under-powered without C3 fuels so it wouldn't have been a good choice over the HA 109 at any stage in the war. I'm definitely learning a lot here.

Thankfully for the US it had the R-2800, which from the very beginning of the war provided 2,000 hp. I understand that they were comparatively large engines and thus were mated to the three biggest and heaviest single-engine fighters of the war but the available horsepower more than made up for this, especially when ADI and 150 octane fuel came into being.

 

[tomo pauk]

Thankfully for the US it had the R-2800, which from the very beginning of the war provided 2,000 hp. I understand that they were comparatively large engines and thus were mated to the three biggest and heaviest single-engine fighters of the war but the available horsepower more than made up for this, especially when ADI and 150 octane fuel came into being.

The R-2800 in ww2 fighters was also outfitted with either 2-stage S/C or it have had turbo as add-on, either solution provided significant HP surplus over the BMW 801 already above 12000-15000 ft.

 

[tomo pauk]

Engine production listing at Kawasaki is attached. They were doing a good job of producing the Sakae engine family (Ha-25, Ha-115), so let's keep them doing just that, but in greater volume, so Nakajima can concentrate on bigger engines. Thus Ha-40 (licence-built DB 601A) is not proceeded with (ditto with Ha-140), the Ki-60 (V12 powered) morphs into a radial-powered fighter.

 

[DarrenW]

The R-2800 in ww2 fighters was also outfitted with either 2-stage S/C or it have had turbo as add-on, either solution provided significant HP surplus over the BMW 801 already above 12000-15000 ft.

Nice way to sum up the overall superiority of the R-2800 set-up.

Now back to the original intent of this thread, which was finding better solutions concerning IJA fighter aircraft...sorry for taking it off course like that.

 

[tomo pauk]

Now back to the original intent of this thread, which was finding better solutions concerning IJA fighter aircraft...
...

Related slightly to the post #15 here - no 2-engined day fighters. That basically means no Ki-45 - in fighter aircraft category, Kawasaki puts all the efforts on 1-engined fighter powered by radial engine. This also means Mitsubishi is not pressured to improve & produce Zuisei engines
(historically, 1st delivery of series-produced Ki-45 actually pre-dates the 1st delivery of series-produced Ki-61 by some 8 months)

 

[tomo pauk]

'Option B' - fighter with a big engine ASAP.
That will mean, at least in 1940-42, that Kasei is in the nose (Army designation was Ha-32). In 1941, Kasei was good for 1340 CV at 4600m (ballpark with BMW 801C). A bit wider than BMW 801 (52.7 in vs. 50.8), but 400-500 lbs lighter and more reliable. Engine of such power can enable for good payload (guns + ammo + fuel) and protection to be carried in the same time. Even a cannon on each wings' side* will not put much of a dent to the performance, on a fighter basically size of F8F (or, similar to the J2M but without the extension shaft on the engine and with a bit bigger wing).
The Kasei in 1943 was good for 1550 CV at 5600 m (~100 CV better than BMW 801D), and later even better altitude performance was extracted, while water-alcohol injection was added to improve boost and thus power at take off, low and medium altitudes. I'd stay away from the versions with extension shaft, for reasons of reliability, 'producibility' and weight (200-300 lbs difference).

*granted, the Army cannons were not stellar examples until the Ho-5 emerged

 

[Admiral Beez]

Unlike the IJN, the IJA was fond to readily adopt new fighters almost on yearly basis after ~1940. For good reasons - the Ki 43 was not well armed, nor fast (level flight nor in dive), nor it was known to be tough; Ki-44 have had high wing loading and still was not stellar with firepower; Ki-61 was plagued by engine problems, ditto for Ki 84. Ki-45 was too many cylinders for too slow speed and, initially, weak armament; other 2-engined types were too late.

So - how would've the IJA fighters developed with less issues? The engine types are the ones historically made in Japan, though you can alter the production of engines (in a timely manner, of course) in order to have enough of desired types made for the newly-fanged fighter force. Starting date is, say, 15th November of 1940 - the Ki 43 is in pipeline for production, and you can have some feedback from Germans. Note that Japanese economy can't support the gazzilion of engines & whole aircraft someone might intend to whip up here, so plan accordingly.

I want the IJAF fighter to be a variant of the IJN's fighter. So, politically these two must be forced to work together.

 

[michaelmaltby]

"... these two must be forced to work together."
haha