Axis aircraft using DB 601: comparison

[alejandro_]

I have written an article on the Ki.61 hien and I decided to compare its performance with other axis aircraft that used DB 601 or derivatives. See graph below (Height in feet vs speed in mph):

- The engine in Macchi 202 gives a maximum power of 1160HP while the weight is 2930kg (250kg fuel)
- The Ha-40 in Ki.61 has a maximum output of 1100HP and the full weight is 3280kg (562kg of fuel~165 imp gallons of fuel)
- The Bf-109 weight is 2540kg and the power 1100HP (300kg of fuel).

The Macchi 202 has the highest speed but carries little fuel. Bf-109E-3 can vary by ~5% according to the test. For some reason French, Swiss and Soviet test give a similar top speed at altitude but lower speed at sea level. Note that Ki.61 is the heaviest, being the one carrying the largest amount of fuel.

I would appreciate if anyone can add any information, correction or opinion. The data I used come from:

http://www.ww2aircraft.net/forum/aviation/maximum-speed-reggiane-2005-a-3267.html
Kurfrst - Baubeschreibung fr das Flugzeugmuster Messerschmitt Me 109 mit DB 601.
http://www.ww2aircraft.net/forum/aircraft-requests/ki-61-tony-speed-altitude-diagram-27545.html

 

[davebender]

I've always liked the Ki-61 (V12 engine) and Ki-100 (radial engine). However there must be a reason the IJA produced twice as many Ki-43s. Was the Ki-61 / Ki-100 expensive to produce compared to the Ki-43?

 

[alejandro_]

I've always liked the Ki-61 (V12 engine) and Ki-100 (radial engine). However there must be a reason the IJA produced twice as many Ki-43s. Was the Ki-61 / Ki-100 expensive to produce compared to the Ki-43?

Ki-43 had a radial engine, more simple to maintain. I would not go as far as to say that it was easier to produce because it required more man hours than Ki-44/84. Maintenance crews and aircraft industry had more experience with radial engines, with more simple cooling systems. IMO the main reasons:

- Model was superseded by Ki-84 Frank.
- Engine production was troublesome, and a limiting factor. Ki-100 is born due to lack of engines for Ki-61-II cells.

 

[davebender]

The Ki-61 program began in 1938 when Japan signed license agreements with Germany. The Ki-84 program began during 1942.

These two programs are separated by four years. How can they be connected? If adequately resourced the Ki-61 and/or Ki-100 would have been in mass production before the Ki-84 program had started. Unless the Ki-61 and/or Ki-100 were simply too expensive for Japan to afford.

 

[alejandro_]

Sorry for late reply, I still get virus warning when trying to access.

These two programs are separated by four years. How can they be connected? If adequately resourced the Ki-61 and/or Ki-100 would have been in mass production before the Ki-84 program had started. Unless the Ki-61 and/or Ki-100 were simply too expensive for Japan to afford.

I did not say that Ki-61 and Ki-84 were connected. My impression is that Ki-61 production was much more complicated to produce and deploy than Ki-84. The IJAAF had to ask Kawasaki to improve the Hien to simplify the design and improve reliability.When manufacturing of Ki-84 began, another production line was installed soon after.

 

[davebender]

Are you sure?

It appears to me the Ki-61 and Ki-84 had similiar problems. Good airframes with poor quality engines. The engine technical problems were fixed eventually but Japan might have been further ahead perfecting DB601 engine production for the Ki-61 rather then starting over perfecting the Nakajima Homare radial engine for the Ki-84.

There was nothing inheritly wrong with the Ki-61 design. It was arguably superior to most Allied aircraft operating in the Pacific.

Nakajima Homare - Wikipedia, the free encyclopedia
1940. Nakajima Homare engine prototype first run.
1941. Homare engine certified for production.

However, the tight design of the engine made it difficult to maintain quality in manufacturing, and unreliability in the field was a significant problem; actual output of early models at altitude was in the range of 1300 hp (970 kW), far below the designed capability. Later models had improved performance, and it became one of the predominant powerplants of Japanese military aircraft in the latter part of the war

 

[krieghund]

For your Ki-61 article some interesting information is here;
http://www.ww2aircraft.net/forum/aviation/ki-61-he-100-related-26499.html

also another user of the DB601

He-100A-0 Series II 2444kg (3x MG17 410 liters fuel) 650 km/h @ 4950m

Special Ki-61 with evaporative cooling system 625 km/h

 

[davebender]

Mitsubishi Kaesei radial engine.
Mitsubishi J2M - Wikipedia, the free encyclopedia

The first few produced J2M2 were delivered to the development units in December 1942 but severe problems were encountered with the engines. Trials and improvements took almost a year and the first batch of the serial built J2M2 Model 11 was delivered to 381st Kokutai in December 1943. Parallel with the J2M2, production of the J2M3 Raiden Model 21 started. The first J2M3 appeared in October 1943 but deliveries to combat units started at the beginning of February 1944

WWII Japan cannot mass produce a high performance fighter aircraft without a reliable high performance engine. It appears to me that didn't happen until late 1943. Far too late to matter.

 

[Shortround6]

The Japanese tried to be just a little too tricky.

The versions of the Kasei engine used in the G4M didn't seem to give too much trouble.
The version/s used in the J2M used an extended shaft/gearbox? to allow for a more tapered/better streamlined cowl. It was the extended shaft and vibration problems that caused a lot of trouble.

A good 1500hp engine in 1942 was possible if they didn't try to get to tricky and that might have been good enough in 1942/43.

The Nakajima Ha-109 used in the Ki-44 at 1450hp seems to have been available in mid/late 1942 also.

A sort of big winged Ki-44 might have been producible in 1942/43 and while not the equal of the Ki-84 it should have been better than the Ki-43 which was kept in production until the wars end.

Using the Mitsubishi Kinsei sooner might have helped also. 1942 versions being good for 1300hp for take-off and 1100hp at 6,200meters. later developed into the powerplant for the Ki-100.

 

[davebender]

That's exactly what Japan needed.

The Kasei engine was probably Japan's best bet for getting such an engine into mass production by 1942. Perhaps the Homare engine would be the long term follow-on for the Kasei engine. Both are air cooled so there would be some sharing of technology.

Forget license production of the DB601. A great engine but Japan cannot afford the diversion of engineering resources.

 

[Shortround6]

That's exactly what Japan needed.

The Kasei engine was probably Japan's best bet for getting such an engine into mass production by 1942. Perhaps the Homare engine would be the long term follow-on for the Kasei engine. Both are air cooled so there would be some sharing of technology.

The Kasei engine was in mass production (of sorts) in 1942 seeing as how it was the Standard engine of the G4M bomber that helped sink the Repulse and Prince of Wales.
It was sort of a Japanese equivalent of the Wright R-2600 though. Rather large in diameter and hard to streamline on a small plane. Which is why the extension shaft and fan cooling on the early J2M. If they had been willing to settle for 10-15mph less to begin with they might have had a 350mph fighter in 1942 with more firepower than the Oscar.
Edit> 350mph at 5500-6500 meters beats 329mph at 4000meters, especially if the "new" plane can dive even close to allied planes.
The Homare engine was much smaller in diameter and offered better streamlining or power per unit of frontal area.
Going for what was technically attractive vs what was more easily obtainable. The Homare was actually a 35.8 liter engine if the publish bore and stroke are correct. even 1800hp from a 35.8 liter air cooled engine is pretty amazing, it is little wonder they had trouble with it. <edit

 

[davebender]

Maybe Japan licensed the wrong German technology.

During 1937 Dornier patented the extension shaft design which was eventually employed on the Do-335 fighter. Would a similiar prop extension shaft work on a Japanese fighter powered by the Kasei radial engine?

 

[Shortround6]

Maybe Japan licensed the wrong German technology.

During 1937 Dornier patented the extension shaft design which was eventually employed on the Do-335 fighter. Would a similiar prop extension shaft work on a Japanese fighter powered by the Kasei radial engine?

Probably not. It is one thing to design an extension shaft that uses an external support for the propeller, like the Dornier flying boats, the Do 335, the P-39/63 and airacuda and just using a longer than normal prop shaft supported by a beefed up bearing in either a normal nose/gear case or an extended one.

For a couple of American tries see:

Factsheets : Curtiss XP-42

Factsheets : Vultee P-66

adding a strong enough cowl/fuselage structure to support the propeller independent of the engine is going to add weight and access difficulties.

 

[davebender]

adding a strong enough cowl/fuselage structure to support the propeller independent of the engine is going to add weight and access difficulties.

Personally I wouldn't bother.

The IJA Ki-44 (Tojo) and IJN J2M (Raiden) will fly just fine without a nose extension. Max speed will suffer but the high power to weight ratio should provide good acceleration and climb plus superior payload. If flown with proper boom zoom tactics they should do well vs P-40s, F4Fs and bombers.

 

[alejandro_]

A sort of big winged Ki-44 might have been producible in 1942/43 and while not the equal of the Ki-84 it should have been better than the Ki-43 which was kept in production until the wars end.

I agree with this, but I wonder if Japan would have been able to manufacture the model in big quantities. Ki-44 production was rather small when compared to other types.

There was nothing inheritly wrong with the Ki-61 design. It was arguably superior to most Allied aircraft operating in the Pacific.

If you are referring to P-40 and P-39, Ki-61 could be superior in many parameters but I don't think it had a massive advantage. When Eric Brown tested a Hien, he stated that handling was similar to a Hurricane and performance typical of a European fighter of 1939. The issue is that the Hien started to be deployed in late 1942 early 1943.

For your Ki-61 article some interesting information is here;

Thanks!