Jack vs. Tojo - Which was better? Why?

GregP said:

That's a problem with a LOT of WWII comparisons. The U.S.A. has a lot of data about their planes while some of the basic data about Axis aircraft are seemingly lifted from one website to the next, verbatim. And the lack of things like standard climb from SL to 10,000 and 20,000 feet or a standard metric number of meters makes comparisons difficult and/or almost impossible. If we DO get decent data in some area, then we seemingly fight over fuel quality, etc. I share your curiosity.

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Awhile back I did actually write up some basic graphs for aircraft which had manifold pressure settings in several formats.

While I don't have the ability to just crank out huge amounts of data alone to do anything useful: I would imagine the ability to create accurate charts in either metric/imperial format, determine power settings in all formats, and overlay everything onto a graph with marks for both, would be very useful.

Creating the charts is easy ... IF you have the data. To me, getting accurate data is the hard part.

It isn't to difficult to convert among manifold pressure units. The U.S.A. used inches of Mercury absolute pressure. The British used pounds per square inch gauge pressure. The Germans used technical atmospheres (ata). 1 ata = 28.958 in Hg. The Japanese and Russian used mm water gauge or mm Hg gauge.

I attached a spreadsheet below to convert among boost units. It is on the first tab, and is number 3).

Just enter your known boost unit in the orange border cell, and all the cells on the same row will convert to the boost unit shown in the title row.

It takes longer to write that than to actually look at it and understand it.

Cheers.

Zipper730 said:

determine power settings in all formats

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This gets a bit harder

Unless I miss-understand you.

HP....................MP/in.....................altitude
2000..................54....................0000
2000...............52.5....................2000ft
1800.................53.....................12,500ft
1650.................53.....................21,000ft

R-2800-8 at 2700rpm no RAM.
it is nice information to have when comparing planes but don't read too much into it as changes in the supercharger or gear ratios can throw the pressure to power settings way off.

S Shortround6

Just to be clear, I don't mean in every pressure format imaginable: I mean in the following

Absolute pressure, inches of mercury; Gauge pressure, PSI; ATA; the Japanese use gauge pressure in millimeters (air, mercury?); and I assume the Soviets used millimeters as well, but I'm not sure what they used.

Zipper730 said:

Absolute pressure, inches of mercury; Gauge pressure, PSI; ATA; the Japanese use gauge pressure in millimeters (air, mercury?); and I assume the Soviets used millimeters as well, but I'm not sure what they used.

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Greg covered it above:

GregP said:

The Japanese and Russian used mm water gauge or mm Hg gauge

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You KNOW it is gauge pressure when they talk about 0.00 psi of boost, because the normal air pressure is always present.

If it really IS a vacuum, the engine won't run!

GregP I looked up the J2M1's weight vs the Ki-44-IIB (Otsu). The J2M1 and the Ki-44-IIB have almost identical empty weights:
Ki-44-IIB (Source: Profile Aircraft: Nakajima Ki-44 Shoki ('Tojo') by John Brindley

• Maximum Loaded: 6,598 lbs
• Empty: 4,643 lbs
• Maximum speed: 376 MPH

J2M1 (Source: Mitsubishi J2M Raiden Jack by Robert Peczkowski)

• Maximum Loaded: Unavailable
• Empty: 4,830 lbs
• Maximum speed: 359 MPH

There is definitely an issue with a lack of standardization between different sources. There's no way the Ki-44-IIB should be faster than the J2M1, J2M2, and J2M3.

There's something else worth mentioning here: the J2M2 has larger fuel and water methanol tanks as well as a slightly different engine compared to the J2M3 Model 21 (according to Peczkowski). Which might explain the performance differences. However, the lack of wing tanks on the J2M2 as well as the lack of a oil cooler scoop makes me think it should have been faster than the J2M3 rather than slower.

The source I usually use for checking Japanese stuff is," General View of Japanese Military AIrcraft in the Pacific War," published in Tokyo (Edit: 1953). I own a (Edit: 1955) copy of the text in both Japanese and English. It says the empty weight of a Ki-44 (version unnamed) is 4,643 pounds. 6,107 gross. There is no overweight point published. It quotes the empty weight of the J2M3 at 5,675 pounds. 7,573 gross. 8,599 overweight.

TAIC Manual No. 2 versus the new source: Ki-44: 6,100 versus 6,107. About a wash. J2M3 Gross: 7,320 versus 7,320. Exactly the same. TAIC manual No. 2 doesn't HAVE an empty weight for the J2M3. I found a source that said 6,200 pounds but my primary source says 5,675 pounds, with the Raiden 33 being much heavier at 6,259. Methinks I used the empty weight of the Raiden 33 instead of the Radien 21. My fault. When you enter data into a few thousand lines manually, a few mistakes tend to creep in, and my posts have a way of zeroing in on these errors whether or not I'm looking for them.

So, by the "general View" source, a well-respected one to be sure, the J2M3 is actually 22% heavier empty, 24% heavier at gross, and 41% heavier when the J2M3 is at overweight status. While not inconsequential, it might or might not account for performance differences.

The source I used for my post above was, as quoted, TAIC Manual No. 2. I attached it below so you all can see the text for yourself. For Axis aircraft, as well as British, there are some missing data. I went through my own sources to fill in some of the missing data for myself, so I have a document where the main fighter aircraft can be easily compared. The comparisons are only as good as the data and, for SOME Japanese aircraft, the source contradict each other. Which source is correct? Especially since they seem to copy one another, down to using the exact same data, with the same data both present and missing.

So, thanks for pointing out the error in the empty weight of the J2M3 in my document, which has now been corrected. Glad somebody is reading the numbers!

Whatever numbers you post, I can find SOME source that quotes different data. I suppose we all have to decide what we believe. Myself, I think that the comparisons we can draw from the TAIC Manual No, 2 are generally about the same as what we could draw from the "General View" source I use as my backstop. That is, MOST of what we can deduce about one aircraft, compared with what we can deduce about another aircraft, generally agree.

If one source claims one fighter climbs at 4,100 fpm and the other aircraft climbs at 3,100 fpm, then both sources will usually show the better-climbing aircraft having a climb rate about 1/3 greater, regardless of the exact numbers.

Cheers.

Clayton Magnet said:

The J2M was a formidable fighter, assuming it was running to spec. And as per this article ( which was posted years prior) was superior to a F6F-5

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The author did a notable job dissecting the attributes of both aircraft and I commend him for his scientific approach. But unfortunately he got the F6F-5s service ceiling completely wrong which would skew the results accordingly. On the other hand, he was unusually accurate with the aircraft's other performance statistics which was refreshing to say the least.

Be that as it may, his findings seem to be in line with most aviation historians so there's really nothing new to be found here. The J2M3 was notable for its extraordinary climb rate and with a comparitively low wing loading it could normally out-climb and out-mauever most allied aircraft it encountered at both low and medium speeds.

He did admit that the Hellcat could mostly out-run and out-dive the Raiden, and at high speeds it also held a slight edge in maneuverability.

I would take it one step farther and give an edge in maneuverability at all speeds to the Hellcat, seeing how many Japanese pilots felt that the J2M wasn't a good match for the American fighter in a classic dogfight scenario.

So the "superiority" of the Raiden depended largly on opportunity, along with using its strengths to gain an advantage in combat. But this was also true for the Hellcat and every other fighter used during the war. A proper running J2M3 was hard to find, but if encountered could assuredly give a better account of itself than the obsolete A6Ms and KI-43s still in service by 1945.

Admiral Beez said:

Is the IJN the only carrier force to specify a frontline fighter incapable of flying from its carriers? Why not make the Jack carrier capable or divert its resources to a carrier fighter? Since when is it the navy's job to intercept B-29s? That nation was messed up.

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My take on this was that it allowed for an increased performance envelope to be achieved. During WWII carrier fighters tended to be at a slight disadvantage when compared to their land-based rivals due to the constraints of improved low speed handling, airframe strengthening, folding wings, tail/catapult hooks, cockpit visibility, ect. Being land-based from the very start the J2M wasn't affected by any of these parameters so its performance was enhanced as a result.

DarrenW said:

My take on this was that it allowed for an increased performance envelope to be achieved. During WWII carrier fighters tended to be at a slight disadvantage when compared to their land-based rivals

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Japan's A6M carrier fighters were a match for every land-based fighter they met until much later in the war, besting Hawks, Buffaloes, Fokkers, Warhawks, Hurricanes and Spitfires. The A6M was mainly disadvantaged against land-based fighters through obsolescence, as land-based Lightnings and Thuds entered IPTO service.

DarrenW said:

Being land-based from the very start the J2M wasn't affected by any of these parameters so its performance was enhanced as a result.

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Good point, but the IJN's carrier fleet could have sure used something with the J2M or Kawanishi N1K's performance during the later fleet engagements. Presuming of course that pilot training/ability kept up with the competition - otherwise it's all Turkey Shoots no matter that aircraft the IJN fields.

Admiral Beez said:

Japan's A6M carrier fighters were a match for every land-based fighter they met until much later in the war,

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The Zero was an anomaly for sure but it must be said that it's ascendancy probably had as much to do with tactics employed as it did with any intrinsic qualities of the type. Many land-based fighters of the same era statistically outperformed it to varying degrees, the P-40 and Spitfire being faster, better armed, and both could take far more punishment. Even the oft-maligned P-39 enjoyed a margin of superiority in certain areas. When the allies learned not to fall into the trap of being forced into a slow maneuvering dogfight the Zero began to display some serious flaws.

The J2M was designed as an interceptor and as such speed and climb rate were paramount. Making it carrier-based would most likely be detrimental in this regard so Mitsubishi chose otherwise. After the initial development of the J2M was complete the firm began once again to dedicate it's resources on the development of the A7M Reppu, which had been delayed by work on the J2M. It was expected to be a shipboard fighter and the true successor of the A6M series. When one examines Japan's carrier situation after the brutal campaigns in the Marianas and Philippine Islands, as well as the allied strategic bombing of the homeland occurring simultaneously it's apparent at least to me that they probably made the right choice by developing the Raiden first.

DarrenW said:

The J2M was designed as an interceptor and as such speed and climb rate were paramount. Making it carrier-based would most likely be detrimental in this regard so Mitsubishi chose otherwise.

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Reminds me of the brief for the carrier-based F8F, where climb rate and speed were also paramount. Mind you, Mitsubishi did not have a 2,250 hp P&W R-2800 Double Wasp to call on.

Admiral Beez said:

Japan's A6M carrier fighters were a match for every land-based fighter they met until much later in the war, besting Hawks, Buffaloes, Fokkers, Warhawks, Hurricanes and Spitfires. The A6M was mainly disadvantaged against land-based fighters through obsolescence, as land-based Lightnings and Thuds entered IPTO service.

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I suggest you explore some of the units that were operating within the 5th AF mid/ late 1942. They were holding their own with their P-39s and P-40s, (especially the P-40) of course the game completely changed when they transitioned to the P-38 (late 1942).

Admiral Beez said:

Reminds me of the brief for the carrier-based F8F, where climb rate and speed were also paramount. Mind you, Mitsubishi did not have a 2,250 hp P&W R-2800 Double Wasp to call on.

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Yes, Mitsubishi could have pursued a shipboard version of the J2M but apparently decided to play it safe. One must remember that Japan didn't have a great amount of resources or time to develop replacement fighter designs, as from Pearl Harbor on they realized they had their backs against the wall.

DarrenW said:

After the initial development of the J2M was complete the firm began once again to dedicate it's resources on the development of the A7M Reppu, which had been delayed by work on the J2M

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Thankfully they did so.
Had carriers like the Shinano, with a complement of A7M, B7A and C6N actually put to sea when originally envisioned, it would have been a serious headache for the allies

Admiral Beez said:

Reminds me of the brief for the carrier-based F8F, where climb rate and speed were also paramount. Mind you, Mitsubishi did not have a 2,250 hp P&W R-2800 Double Wasp to call on.

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And that is a major difference.

A lot depends on who is responsible for what.
What was the Imperial Japanese Navy responsible for?
If it was responsible for naval bases in areas that the Army was not responsible for then having a fast climbing interceptor to defend the bases might have been very important.
The British in 1938-40 was thinking about a different airplane for base defense than for carrier use, so the Japanese were not alone in this thinking.

In the US the areas of responsibility were a bit different. The Army had a greater share of the responsibility of naval base defense.
Navy planes were not going to sit on airbases while they were being attacked but it was the armies job to supply the needed interceptors or at least the bulk of them. .
In the Pacific things got a little mixed up and the Marines did supply land based squadrons but that was after Pearl Harbor.

If the Navy was responsible for air defense of some of the Island bases with no Army air units within support range the answers become different.

The thought process for the Raiden started in 1938 with the written specification showing up in Sept 1939. Work on the A6M slowed down work so the first prototype didn't fly until March of 1942 but the initial specification (request) called for a speed of 600kph at 6,000 meters, a climb of 5 1/2 minutes to 6,000 meters, a landing speed of 130 kph and a take-off run of 300 meters in zero wind. Some of these are in conflict with each other, especially in 1939-41 with existing or promised engines.

A carrier fighters needs a bigger wing for lower landing speed and shorter take-off run. A bigger wing means lower top speed and less climb.
The J2M1 prototypes used 1430hp engines for take-off. They were over 1000lbs heavier than an early A6M.

Something (or several somethings) had to go.

Early prototype with small sloped windscreen and the the long extension shaft for the prop.
Trying to land this thing on a carrier would have been suicidal. But a larger wing, short nosed, tall windscreen fighter wasn't going to come close to the desired speed.

DarrenW said:

Yes, Mitsubishi could have pursued a shipboard version of the J2M but apparently decided to play it safe. One must remember that Japan didn't have a great amount of resources or time to develop replacement fighter designs, as from Pearl Harbor on they realized they had their backs against the wall.

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IJN is to blame, IMO, that they specified the J2M in the 1st place; 'J' standing for land-based fighter in the IJN nomenclature. Should've requested another ship-borne fighter instead, and have the land-based version of the A6M outfitted with a more powerful engine for that task. Yes, range/radius will go down, but not as much as it was short on the J2M.

tomo pauk said:

IJN is to blame, IMO, that they specified the J2M in the 1st place; 'J' standing for land-based fighter in the IJN nomenclature. Should've requested another ship-borne fighter instead, and have the land-based version of the A6M outfitted with a more powerful engine for that task. Yes, range/radius will go down, but not as much as it was short on the J2M.

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Well, if you are satisfied with a 350-360mph aircraft in 1942/43 you might have gotten it (barely). If you are trying for the 370mph airplane the things are harder.

Or will the A6M with the 1942 Kinsei engine be fast enough? Or do you have to wait for 1943?

Just opened my new book on Japanese aero engines and it is missing 4 pages right at the end of the Mitsubishi chapter on the pacific war period (all the Mitsubishi engines we are interested in) all but one of the data tables for the Mitsubishi engines.

The Japanese were short on power and tried to substitute aerodynamic tricks

Some planes could get away with it, some gave more troubles with poor vision or cooling or whatever.

Shortround6 said:

And that is a major difference.

A lot depends on who is responsible for what.
What was the Imperial Japanese Navy responsible for?
If it was responsible for naval bases in areas that the Army was not responsible for then having a fast climbing interceptor to defend the bases might have been very important.
The British in 1938-40 was thinking about a different airplane for base defense than for carrier use, so the Japanese were not alone in this thinking.

In the US the areas of responsibility were a bit different. The Army had a greater share of the responsibility of naval base defense.
Navy planes were not going to sit on airbases while they were being attacked but it was the armies job to supply the needed interceptors or at least the bulk of them. .
In the Pacific things got a little mixed up and the Marines did supply land based squadrons but that was after Pearl Harbor.

If the Navy was responsible for air defense of some of the Island bases with no Army air units within support range the answers become different.

The thought process for the Raiden started in 1938 with the written specification showing up in Sept 1939. Work on the A6M slowed down work so the first prototype didn't fly until March of 1942 but the initial specification (request) called for a speed of 600kph at 6,000 meters, a climb of 5 1/2 minutes to 6,000 meters, a landing speed of 130 kph and a take-off run of 300 meters in zero wind. Some of these are in conflict with each other, especially in 1939-41 with existing or promised engines.

A carrier fighters needs a bigger wing for lower landing speed and shorter take-off run. A bigger wing means lower top speed and less climb.
The J2M1 prototypes used 1430hp engines for take-off. They were over 1000lbs heavier than an early A6M.

Something (or several somethings) had to go.
View attachment 690706
Early prototype with small sloped windscreen and the the long extension shaft for the prop.
Trying to land this thing on a carrier would have been suicidal. But a larger wing, short nosed, tall windscreen fighter wasn't going to come close to the desired speed.

Click to expand...

A major strategic failing of the IJN was its insistence that all its aircraft have supremely long range. Zeroes (or really any of their carrier aircraft) often doubled as scout aircraft (despite having horrible radios, which limited their effectiveness). This also gave the IJN the advantage of being able to conduct attacks beyond the strike radius of enemy carriers.

The blunder here was that the IJN brass didn't want any of their early-to-mid war frontline aircraft to have even the lowest grade of self-sealing fuel tank, despite objections from designers. The B6N series, for example, could do 2,400 miles as a scout or 1,400 with a full bomb load. It's borderline insane that their most shot-up bombers lacked self-sealing fuel tanks.

As such, the Imperial high command didn't assign much value to carrier-based interceptors with short ranges as they couldn't pull double duty as scouts. This overemphasis on offense and strike power would cost them at Midway, although it also aided the IJN's tactical victories throughout '42 and part of '43.

A Raiden-like interceptor at Midway would have been exceptionally effective at intercepting dive bombers. Except for one thing: its laminar wing would have made for longer take-offs and landings. Which means a Raiden may only have been able to operate from the largest of carriers, if at all. The Raiden's stall speed, with flaps, was something like 92 MPH. A Zero, in comparison, was something like 65 MPH (according to TAIC).
AFAIK, the only "laminar" airfoil to see carrier service during WW2 was on the Japanese C6N Saiun/Myrt. So there may have been some issue adapting low-flow wings to carrier craft.

Getting back to the Tojo-Jack comparison, the Tojo's stall speed (with its non-laminar wing) was around 93 MPH, according to Martin Ferkl. However, other sources list it as being around 85 MPH. I think both could be correct and the higher limit is flaps up. Overall, the Tojo's size and lower landing speed would have made it a better fit for carrier operations.