1943: the best Japanese fighter

[tomo pauk]

Both DB 601A and 601N were pushed to 2800 rpm, one on B4, other on C3. The rpm should have no relation to the higher oct fuel.

Can you point me to the relevant ATAIU document?

 

[Hiromachi]

Sorry, not ATAIU but TAIC Summary. And no, no idea which one it is. I only got fragments of it. Here is fragment of the page :

 

[tomo pauk]

Thanks.
The fuel injection is indeed different, though I don't really think it will affect the altitude power, what should be the job of supercharger and appropriate gearing.

 

[FLYBOYJ]

I heard about some of these issues shown in this article. Just throwing in an interesting perspective.

Japan's Fatally Flawed Air Forces in World War II | History Net: Where History Comes Alive – World US History Online | From the World's Largest History Magazine Publisher

 

[Hiromachi]

Whatever the reason is there was a difference to Ki-61 advantage.

I heard about some of these issues shown in this article. Just throwing in an interesting perspective.

Japan's Fatally Flawed Air Forces in World War II | History Net: Where History Comes Alive – World US History Online | From the World's Largest History Magazine Publisher

Logistics, designing and producing an aircraft is only a small part of big game. Someone has to fly it, someone has to maintain it, someone has to rearm and refuel it, some people have to produce spare parts for it and others have to ferry them.

 

[tomo pauk]

Indeed it was. It was probably a good thing for the Allies that DB 605A was not licensed in Japan, as well as a too late outfitting the Ki 61 airdrame with a radial more powerful than the V-12.

 

[tomo pauk]

The war time report on the Japanese 20 mm cannon, a development of the Oerlikon FFL. A bit on the FFL can be read here.

 

[Hiromachi]

Type 99-2 was pretty decent weapon, once the ballistics improved it could finally become a main weapon.
But then Japanese Army came with Ho-5 which was possibly best ww2 mass produced cannon.

 

[tomo pauk]

The Type 99-2 was with good ballistics from the start, since it was using the 'intermediate powerful' cartridge, leagacy of the FFL. Unlike the 'low power' Type 99-1, that shared low power cartridge with FFF, along with Ikaria MG FF.

But then Japanese Army came with Ho-5 which was possibly best ww2 mass produced cannon.

A fine cannon indeed. The contenders for the title might be the B-20, MG 151/20, plus the ones that can't fire synchronised, Hispano V and Type 99-5. Allied report on the Ho-5, that does not fit in this time line:

 

[Hiromachi]

The Type 99-2 was with good ballistics from the start, since it was using the 'intermediate powerful' cartridge, leagacy of the FFL. Unlike the 'low power' Type 99-1, that shared low power cartridge with FFF, along with Ikaria MG FF.

Umm, yeah, thats what I intended to mean. Once Type 99 was adjusted for longer cartridges the ballistics improved. I guess its getting late here and I loose my sense ...

A fine cannon indeed. The contenders for the title might be the B-20, MG 151/20, plus the ones that can't fire synchronised, Hispano V and Type 99-5. Allied report on the Ho-5, that does not fit in this time line:

B-20 was a fine gun on its own but it used same, limited ammunition as ShVAK. Great parameters but limited effectiveness against objects. Though one must admit that if Soviets had terrible quality of manufactured weapons, the lagged behind with some designs, their air weapons were often superb.

MG 151/20 had on the other hand a very mediocre ballistics but the ammunition, in particular Mine-shell gave a great results.

Hispano ... after reading so many reports of P-38s, Spitfires, Beaufighters ... those Hispanos were neither great guns nor they were reliable. A combat without jammed guns was in 1942-1943 a miracle. Dont know how far it went with Hispano V but with US AN/M3 issues continued.

Type 99-5 never became a mass produced weapon, it was still at prototype stage by the end of the war. And it really should have been scrapped in favor of a new design.


I actually have an Aberdeen Proving Ground comparative trials of Ho-5 and AN/M3 and ammunition for them. Will later on look what can I write from it, to give some abstract.

 

[tomo pauk]

The US saga of their production Hispanos was a sad one, the British production were good and got better. The Hispano V fired faster than the Mk II, while being lighter and shorter. Ballistics was great, even with the Mk V with a bit lower MV.
Muzzle velocity of both Ho-5, MG 151/20 and B-20 (and ShVAK) was in the ballpark, from ~730 (Soviet) to 800 m/s (MG 151/20 firing M-geschoss), so the ballistics were just fine.
The B-20 was a featherweight, more than 10 kg lighter than the not heavy Ho-5. ShVAK and MG 151/20 were a somewhat heavier than the Ho-5, but were earlier available.
The main shortcoming of the Ho-5 was that it fired the ligthest shell - 79g, per T. WIlliams. Hispano fired almost twice the weight (130 g), the IJN 20 mm cannons were at 128 g.

Installation of 4 Hispanos in the wing was lacking in heating capacity, that was the main problem with the 'C' armament, along with loss of performance.

 

[Hiromachi]

The US saga of their production Hispanos was a sad one, the British production were good and got better. The Hispano V fired faster than the Mk II, while being lighter and shorter. Ballistics was great, even with the Mk V with a bit lower MV.
Muzzle velocity of both Ho-5, MG 151/20 and B-20 (and ShVAK) was in the ballpark, from ~730 (Soviet) to 800 m/s (MG 151/20 firing M-geschoss), so the ballistics were just fine.
The B-20 was a featherweight, more than 10 kg lighter than the not heavy Ho-5. ShVAK and MG 151/20 were a somewhat heavier than the Ho-5, but were earlier available.
The main shortcoming of the Ho-5 was that it fired the ligthest shell - 79g, per T. WIlliams. Hispano fired almost twice the weight (130 g), the IJN 20 mm cannons were at 128 g.

It was 85 g for Type 2 HE shell, same was for Type 4 HEI shell and finally the Type 100 AP-T round had a weight of 113 g.
Minengeschosspatrone was something like 95 g, thus not much heavier in this case from Japanese rounds. Panzergranatpatrone 151 had a weight of 117 g according to wiki.


Regarding Aberdeen Proving Ground trials, Ho-5 presented ROF between 800 to 900 RPM depending on the conditions. Muzzle velocity of the complete rounds was 2287-2329 f/s (~700 m/s) with the AP round, and 2421-2515 f/s (~750 m/s) for HE round, during the time-of-flight test.
To bring some summary :

- Japanese Ho-5 APT round was superior to US AP round in penetration, in fact Japanese was the only round in tests to be able to penetrate armored plate 1.25" thick

- Japanese HE round was inferior to US HEI round in penetrating armored plates however its explosive power was greater and the average size of holes created in plates was larger than for US HEI. However it seems that high effect on Japanese HE rounds had corrosion.

- Japanese fuzes failed multiple times but even though majority was considered to work satisfactory, it was unknown exactly why they performed in such a "peculiar" manner. Notes say that factory powder loads failed to generate enough energy to activate them, though it was mentioned that it could be due to long time of the powder spending in casings, inappropriate preserving both by Japanese and later on by Americans and finally by shipping to US in bad conditions, you know how humid is air over seas.
It is known that the degradation of quality of Ho-5 guns effected in reduced powder loads to compensate for shorter life of firing mechanism.

- Ho-5 almost never failed in firing even at extremely high and low angles and during high G-loads, only case when the gun/ammo failed was when ammunition was deformed or when angles exceeded depression of -70 deg.

The effects of that are written as Ballistic limits (F/S) and for AP rounds that would look for example like this :
Plate Ballistic Limits (F/S)
Thickness Type AP 20 mm, M95 Japanese APT, 20 mm
0.5" Homogeneous 1332 1010
1.0" Homogeneous 2864 2395

0.75" Face-Hardened 1819 1830
1.25" Face-Hardened * 2756
*Partial penetration obtained at the highest velocities fired.


For the US it is said that they used standard M95 20 mm AP and T23 20 mm HEI.

 

[tomo pauk]

Thanks for the excerpts.

It was 85 g for Type 2 HE shell, same was for Type 4 HEI shell and finally the Type 100 AP-T round had a weight of 113 g.
Minengeschosspatrone was something like 95 g, thus not much heavier in this case from Japanese rounds. Panzergranatpatrone 151 had a weight of 117 g according to wiki.

The M-geschoss was with much more HE content, and even on just 92 g it was a powerful round. The H-geschoss principle was copied from French and British post war. There was also 115 g HE for the MG 151/20. There are very good articles about ww2 weaponry in this forum, 'Wepon system tech' subforum.
IMO the Soviets didn't judge their 20mm shell (95 g) as powerful enough vs. German bombers, going with the 37 mm cannon vigorously already in 1942 (and 45 mm soon after), while trying to employ 23 mm in air-to-air combat, coming out finally with the 'mid power' 23 mm cartridge in 1945 and 'mid power' 37 mm cartridge in late 1940s.

It is known that the degradation of quality of Ho-5 guns effected in reduced powder loads to compensate for shorter life of firing mechanism.

Looks like the Ho-5 was designed from the get go around the not so powerful cartridge. The correction to the T. Williams book 'Rapid fire' has this by Ted Bradstreet, take it for what is worth:

PAGE 174:
The 20x94 ammunition in the Ho-5 was not downrated in performance: it was designed for 750 m/s from the start.

From here.

 

[Hiromachi]

Thanks for the excerpts.
The M-geschoss was with much more HE content, and even on just 92 g it was a powerful round. The H-geschoss principle was copied from French and British post war. There was also 115 g HE for the MG 151/20. There are very good articles about ww2 weaponry in this forum, 'Wepon system tech' subforum.
IMO the Soviets didn't judge their 20mm shell (95 g) as powerful enough vs. German bombers, going with the 37 mm cannon vigorously already in 1942 (and 45 mm soon after), while trying to employ 23 mm in air-to-air combat, coming out finally with the 'mid power' 23 mm cartridge in 1945 and 'mid power' 37 mm cartridge in late 1940s.

It also comes from the different approach, Japanese tried the German method and for instance there was a special round for Type 99 cannon having about 11 grams of PETN. General consensus was that pure explosive power was not sufficient and thus a lot of emphasis was put on incendiary rounds. Almost every Japanese round not only has explosive material but also contains few grams of incendiary. And it was considered that incendiary is by far more effective. In some way it is substantiated by the US post war research.
Quoting "Exploding fuel tanks (...)" by R. L. Dunn, page 140 :

Americans studied the vulnerability of their aircraft. In a USAAF study conducted late in the Pacific War it was reported that fire was involved in 59 % of the aircraft lost. Smoke was observed in an additional 13 %. In a US Navy study of 501 single engine aircraft damaged in air to air combat from September 1944 to August 1945 the most common form of damage was to the aircraft structure (215) but nearly 90 % of the aircraft suffering such damage returned to base. In contrast of 57 aircraft suffering damage to oil or fuel systems only 18 % survived. Strikes in the cockpit hitting the pilot or controls resulted in only about 25 % of the aircraft surviving. This was the second most common form of damage. Damage to the engine or hydraulic system resulted in losses about 60 % of the time but was less common. A variety of other forms of damage caused relatively few losses.
Data from the American studies suggest that, despite self-sealing fuel tanks and pilot armor, fuel tanks and the pilot remained the most vulnerable areas on American aircraft. The American studies also ten to confirm the Japanese report that American fuel tanks were vulnerable to Japanese incendiary fire. (...)
In the US Navy study about 38 % pf all aircraft receiving damage were lost. About 30 % of the aircraft damaged received damage to the most vulnerable areas and accounted for 63 % of the losses. In contrast only 19% of the single engine Japanese aircraft damaged in 1941 Hawaii operation were lost. At least some of the Japanese aircraft returning to their carriers in a damaged condition had received hits in the fuel tank or cockpit area. During the Midway operation Japanese aircraft also survived similar damage. Losses among aircraft of the Japanese navy's 25th Air Flotilla from April to November 1942 amounted to 30% of all aircraft damaged, less than the loss ratio of aircraft in the US Navy study covering late 1944 and 1945. About twice as many Japanese aircraft were damaged in air combat compared to anti-aircraft fore (US Navy study was limited to damage in air-to-air combat). This data suggests American aircraft may have been about as vulnerable to Japanese aircraft fire at the end of the war as Japanese aircraft had been to Allied fire at the beginning of the war. This in turn suggests that the lethality of aircraft armament and ammunition eventually kept pace with and outstripped aircraft defenses.

Soviets actually were experimenting with 23 mm guns much earlier, in fact LaGG 3 prototype (I-301) was armed with 23 mm gun. Also, they were first to arm aircraft with 20 mm guns (on I-16 aircraft).
In regard to their round, it wasn't exactly the round itself which had very good ballistics with 800 m/s muzzle velocity but their ammunition ... The first pre war rounds, still being in use for the large part of the war had only 3.7 gram of Tetryl (OF round) or
0.85 g of Tetryl and 3.9 grams of incendiary composition (OFZ round). But main soviet 20 mm round during ww2 was OZ. It contained a considerably greater quantity of high explosive filler. Three different filler versions may be encountered: The earliest filler type consisted of 3.4gm incendiary composition ZZh-49 or DU-5 that was topped with 2.8gm GTT high explosive. In 1942 GTT was replaced by A-IX-2 explosive, aprox. 2.64 grams.
The final version was a projectile loaded with 5.6 grams of A-IX-2.

Looks like the Ho-5 was designed from the get go around the not so powerful cartridge. The correction to the T. Williams book 'Rapid fire' has this by Ted Bradstreet, take it for what is worth:

PAGE 174:
The 20x94 ammunition in the Ho-5 was not downrated in performance: it was designed for 750 m/s from the start.

From here.

The case was filled with 21.4 grams of short cord. That's the only thing I know from Japanese sources, so I'd like to see further references to the words of Ted.

 

[tomo pauk]

It was mentioned here that Ki-61s were armed with either 2 HMGs or heavier. However - they were initially armed with 2 LMGs and 4 HMGs.
This article might be worth reading: link.

 

[Vincenzo]

It was mentioned here that Ki-61s were armed with either 4 HMGs or heavier. However - they were initially armed with 2 LMGs and 4 HMGs.
This article might be worth reading: link.

actually 2 7,7 and 2 12,7

 

[Hiromachi]

That is correct, first variant that arrived on front-lines was armed with two 12.7 mm Ho-103 machine cannons and two 7.7 Type 89 machine guns - Ki-61-I Ko
It was soon followed by model Otsu with four HMGs and than by Hei with two cannons.

And of course I know the article, but its related to Ki-43-I.

 

[tomo pauk]

actually 2 7,7 and 2 12,7

Whoops, indeed, I'll edit the post.