Japanese 2-engined A/C becoming top crop?

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tomo pauk

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Apr 3, 2008
... mostly for the IJN, but the IJA can benefit, too.
Japanese manufactured a number of 2-engined designs, some better than the other. What they lacked - talking about series-produced A/C - were the really high performance heavy fighters, and actually fast bombers.
Any suggestions on what they should be doing differently, within the constrains of technology available for them in 1939-45?
 
Interesting topic tomo but looks too wide to comment.
If I may view the Pacific War from my own insight, I think that Japan should have expanded the production capabilities in Manchukuo first as it was the war of 'volume'.

Manchuria Aircraft Co., Ltd. in 1943
Manchuria_Aircraft_Co.jpg
 
Japanese Navy might've put to a good use the 2-engined fast bombers. Something size and shape of Ki-45 or Ki-46, but with an enclosed bomb bay, capable to carry at least one 500 kg bomb (800 kg is even more appealing, remove the bob bay doors need-be). Guns being reduced to bare minimum, talk rear-firing HMG, and forward-firing pair of cannons/HMGs?
Flying at 340-360 mph and with useful range/radius, these will be quite a task for the Allies to intercept. Appeal for the Japanese is that the small twins use the small, almost legacy engines, so they can be manufactured in good quantities.
 
Japanese twin-engined fighters like Ki-45 or J1N(Irving) were failure as a fighter but both happened to be good as an interceptor when B-29s appeared in the sky but this was all. On the other hand, Yokosuka P1Y was excellent as not only a bomber but a fighter unexpectedly. This plane would have had a good chance to be equipped with such HMGs as a fighter bomber. However, in view of general situation of saving resources at the time, such a twin-engined plane was luxurious and usage was limited. For a fighter, single-engined one like N1K2-J was enough in performances. According to a testimony, Ki-46 could have been a good interceptor or bomber too but Japan had to have enough production capabilities to do so.
 
Japan had a gun problem, or several.
They didn't have enough of them, many of the 1941-43 aircraft being under gunned.
They also were using up way too many resources building small numbers of not very good guns. This really shows up with the twin engine aircraft where the designers/planners seem to be throwing everything at the wall and not only seeing what stuck but what seemed to slide even less than quickly to the ground.

t_ho-203_37mm.gif@webp

This 37mm cannon was used on quite a number of Ki-45s and some of the later prototypes.
Think of it like the US 37mm smaller, weaker, slower cousin.
It was lighter than the US 37mm but after that in had no positive attributes.
At times the Japanese resorted to using a hand fed 37mm AT (or tank gun?) in the ventral tunnel of the Ki-45. Think of a 1/2 scale gun from the B-25 (to be fair it was earlier).
The Gun used in the Ki-46 was a different 37mm
dinahho204-jpg.jpg

There was also a collection of 30mm and 55mm guns at the end of the war to try to deal with the B-29s.
The Japanese Army had these 20mm guns at the start of the war.
m_Type_97_gun.jpg.072427f97425ce103aa4c89623e7ee89.jpg

Ho 3 was used in the Ki-45 in the ventral tunnel. It wasn't too bad except it fired about 2/3rds as fast as a Hispano. It was about as powerful as a Hispano per round. The Drum held 50 rounds and apparently the Ki-45 carried a spare drum.
The problem starts with the Ki-45 using just one of these guns and a pair of the small 12.7mm machine guns which is a small return for the 2 engines invested in the machine.
The Ki-96 showed up near the end of the 1943 and maybe more of what Tomo had in mind.
640px-Ki-96-2s.jpg

However the Japanese gave the prototypes one of the weak 37mms and two of the 20mm Ho 5 cannon which means the effective fire power wasn't much better than Ki-61s with 20mm cannon. The Japanese were depending on lucky hits from the 37mm gun way too much.
The Ki-45 carried an over 400 liter fuel tank between the pilot and the rear gunner/loader/radio operator. Yes you could move the fuel out into the wing and get rid of the tunnel gun to fit a bomb inside the aircraft.

I am not expecting four Hispano's but the Japanese weren't coming close to even two Hispano's for much of the war in their existing twins.
 
I am not expecting four Hispano's but the Japanese weren't coming close to even two Hispano's for much of the war in their existing twins.

One of the reasons for this thread is my opinion that Japanese twins were ... worse than what was possible back then. Even having 3 Ho-3s represents a far greater firepower than what was used, and was within the abilities of Japanese industry to make. Granted, IJN twins can use the lighter Type 99-2, or much lighter Type 99-1; four of the later will not bee too heavy.
Back to the IJA - modifying the Ho-3 for the belt feed, or even coming out with a big drum would've been IMO a much better use of time and resources than experimenting with 37-40mm cannons. Sped up the Ho-3, too.

The Ki-45 carried an over 400 liter fuel tank between the pilot and the rear gunner/loader/radio operator. Yes you could move the fuel out into the wing and get rid of the tunnel gun to fit a bomb inside the aircraft.

That was kinda my point - fast bombers might be a better asset than big fighters, for the same resources spent. Make them as bombers from day one, both for Navy needs as well as for the Army. It will be easy to install cameras and long-range radios on these, as well as some guns' firepower later.

The problem starts with the Ki-45 using just one of these guns and a pair of the small 12.7mm machine guns which is a small return for the 2 engines invested in the machine.
Bingo.

The Ki-96 showed up near the end of the 1943 and maybe more of what Tomo had in mind.

Size and shape fits, role not so much - needs to have a bomb bay :)
 
The 2 engine fighters could certainly have been improved.
But you are trying to have them take over for the 2 engine bombers which were somewhat of a sorry bunch.
Fix/replace the bombers and then fix the fighters.
Ki-48 Lily
640px-Ki-48_99siki-souhatu-keibaku.jpg

It was produced in numbers of over 1500 too many, perhaps none should have been built. (1997 total).
It went into production in the summer of 1940. The guns (3) had 3/4 the rate of fire of Vickers K gun and about 70% of the ammo capacity in the drum. And the British were trying frantically to fit twin guns in many aircraft. Germans were also adding 2-3 more guns in their bombers in the summer of 1940.
Japanese had no protection in the early versions (until the summer of 1942).
Typical bombload was six 50 kg bombs and used a 4 man crew. Had a wing around 1/3rd larger than the Ki-45 wing. Was developed after the Ki-45.

The Ki-21 Sally had some excuse, having first flown in Dec 1936 and entering squadron service in late 1938. But like many Japanese aircraft it got stuck in time. It took too long to get more guns and adding extra crew to man single 7.7mm MGs didn't really do much.
The Ki-21 IIb didn't show up until part way through 1942 and they built just under 700 out of the just over 2000 Ki-21 built, production stopped in 1944.
ki21-bismarck-sea.jpg

the single 12.7mm gun in the turret was traversed with a set of bicycle pedals and elevated by the gunners arms.
The Ki-49 was a bit of a mess from the start.
800px-ArtImage_Ki-49-I.jpg

From a computer game but shows the problem. 20mm gun in the dorsal position, powered by muscle. The gun was pictured above with a 15 round magazine, about 2 seconds of firing time. All other guns on the early versions were the 7.7 type 89 that was barely better than a Lewis gun. Trouble is the plane was entering service in 1941and used an eight man crew to deliver 1,000kg of bombs. There were some upgrades to the armament but too little, too late. They built just over 800 total.
The Japanese were building bombers that were 1-2 years behind the world standards.
Asking some modified fighters to stand in wasn't going to change the situation much.
Single 800kg bombs are good against large warships, not so good against most other Pacific targets.
The Japanese could have used bombers that could drop 1500-2000kg of 250-500kg bombs (or a crap load of 100-125kg bombs) to saturate air fields and ground positions.
 
Perhaps the KI-83 would fit the bill, Tomo?

It was fast and capable of high altitude performance along with a decent range.

It was heavily armed (two 20mm and two 30mm cannon).

And most important, it was reported to have exceptional maneuverability.
 
The 2 engine fighters could certainly have been improved.
But you are trying to have them take over for the 2 engine bombers which were somewhat of a sorry bunch.
Fix/replace the bombers and then fix the fighters.
Note that my emphasis is more on 'make the better bombers' rather than to 'fix the heavy fighters'. Don't make any bespoke 2-engined fighter for all I care.

Ki-48 Lily
It was produced in numbers of over 1500 too many, perhaps none should have been built. (1997 total).
It went into production in the summer of 1940. The guns (3) had 3/4 the rate of fire of Vickers K gun and about 70% of the ammo capacity in the drum. And the British were trying frantically to fit twin guns in many aircraft. Germans were also adding 2-3 more guns in their bombers in the summer of 1940.
Japanese had no protection in the early versions (until the summer of 1942).
Typical bombload was six 50 kg bombs and used a 4 man crew. Had a wing around 1/3rd larger than the Ki-45 wing. Was developed after the Ki-45.

Good - have Kawasaki make a small bomber instead of both Ki-45 and Ki-48.

Single 800kg bombs are good against large warships, not so good against most other Pacific targets.
The Japanese could have used bombers that could drop 1500-2000kg of 250-500kg bombs (or a crap load of 100-125kg bombs) to saturate air fields and ground positions.

See, there is a lot to improve upon :)
Two 1500 HP engines and better should really be lugging the, at least 2000 kg bomb load around.

Asking some modified fighters to stand in wasn't going to change the situation much.

Yes, modifying the Zeros or Oscars into bombers is a worse thing than making good bombers from the get go.

Perhaps the KI-83 would fit the bill, Tomo?
It was fast and capable of high altitude performance along with a decent range.
It was heavily armed (two 20mm and two 30mm cannon).
And most important, it was reported to have exceptional maneuverability.

Excellent aircraft, indeed 'top crop'.
Several 'strikes' against it, though - it was 1st flown in 1945, and was powered by engines that were not in mass production. Japanese need something for 1942-43 to induce the probems to the 'West' (even 1944 is too late). Sorta Japanese Mosquito, obviously with radials instead of the V12s
 
Japanese need something for 1942-43 to induce the probems to the 'West' (even 1944 is too late). Sorta Japanese Mosquito, obviously with radials instead of the V12s
The problem for the Japanese is that they are 1-2 years late in engine development. Most of their 2 speed engines (or higher horsepower ones) show up in 1942.
The Ki-21II shows up early, Dec 1940 with it's 1500hp T-O engine.
The Ki-48 doesn't get the good version of the engine until April 1942. How long before it is the dominate version?
The Ki-45 doesn't get the good version of the engine until early 1942. How long before it is the dominate version?
The Ki-49 doesn't get the good version of the engine until Sept 1942. How long before it is the dominate version?
The G4M1 used two engines before they got to the G4M2. The 2nd engine in the G4M1 didn't show up until they were taking losses around Port Moresby. This engine, while rated at the same take-off power (1530hp) as the first offered 1280hp at 6000 meters instead of 1340hp at 4,000 meters.

You don't get the 1500hp small engines in 1942. You get the big 1500hp engines in 1942 and small 1100-1150hp engines that can make power in the high teens.
The Ki-46 was using and rated for 1080hp for take-off and 1055hp at 2800 meters until the end of 1942/beginning of 1943 when the 1500hp Ha 112-II stared showing up. And they kept the older engine in production into 1944, so 1943 saw both.
Note that my emphasis is more on 'make the better bombers' rather than to 'fix the heavy fighters'. Don't make any bespoke 2-engined fighter for all I care.
The Ki-45 was actually rather useful in 1942, more as an attack plane or strafer rather than for air to air combat. But the Japanese didn't have much in the way of converted bombers for strafing.
Good - have Kawasaki make a small bomber instead of both Ki-45 and Ki-48.
We are back to the engine situation (and the guns).
For some reason the Ki-45 could fly about 1000 miles clean (1400 miles with drop tanks) with a 2 man crew and the Ki-48 needed 4 men to fly 1200-1300miles.
Pilot, Bomb aimer/gunner, radio operator/dorsal gunner, navigator/ventral gunner?
See, there is a lot to improve upon :)
Two 1500 HP engines and better should really be lugging the, at least 2000 kg bomb load around.
For some reason the Japanese got stuck on the 1000kg bomb load (or close to it) and just tried to increase the range and speed and/or throw a few more 7.7mm mgs out the side windows.
The Ki-67 was pretty zippy but the requirements issued in Feb 1941 called for standard bomb load of 500kg with a max of eight 100kg bombs, three 250kg or one 500kg. Normal crew of six to eight and max crew of nine-ten. Guns were to be three 7.7s and one 12.7mm dorsal and one 12.7mm in the tail. Prototype flew Dec 27th 1942 and 3rd prototype flew March of 1943, went into combat in Oct 1944. That could have been speeded up some.
Yes, modifying the Zeros or Oscars into bombers is a worse thing than making good bombers from the get go.
Sorry, I meant using the Ki-45 as a bomber or any competitor (ki-46).

We really need to figure out what the Japanese were thinking with those large crews, small bomb loads and poor gun armament.
 
The problem for the Japanese is that they are 1-2 years late in engine development. Most of their 2 speed engines (or higher horsepower ones) show up in 1942.
The Ki-21II shows up early, Dec 1940 with it's 1500hp T-O engine.
The Ki-48 doesn't get the good version of the engine until April 1942. How long before it is the dominate version?
The Ki-45 doesn't get the good version of the engine until early 1942. How long before it is the dominate version?
The Ki-49 doesn't get the good version of the engine until Sept 1942. How long before it is the dominate version?
The G4M1 used two engines before they got to the G4M2. The 2nd engine in the G4M1 didn't show up until they were taking losses around Port Moresby. This engine, while rated at the same take-off power (1530hp) as the first offered 1280hp at 6000 meters instead of 1340hp at 4,000 meters.
Problems lay there, but also elsewhere.
Like - don't make the G4M with a fuselage and wing for a transport aircraft - make the slender fuselage, and small wing (ie. 600 sq ft, not 840 sq ft). Basically, the P1Y-lookalike, but in 1939. Less weight, lower drag, better speed and mileage.
Similar with Ki-49 and -21: bombers are bombers, not something that can became a transport aircraft in a pinch.

You don't get the 1500hp small engines in 1942. You get the big 1500hp engines in 1942 and small 1100-1150hp engines that can make power in the high teens.
The Ki-46 was using and rated for 1080hp for take-off and 1055hp at 2800 meters until the end of 1942/beginning of 1943 when the 1500hp Ha 112-II stared showing up. And they kept the older engine in production into 1944, so 1943 saw both.

I get the big 1500 HP engines in 1941 (Kasei), and medium-sized 1500 HP engines in 1942 (Ha-109).
For the bombers size of Ki 45 or Ki 46, Sakae can be a start in 1941, unless we want them to start with Kinsei or Ha 41. By 1942, the 2-speed versions of these engines can take torch.

The Ki-45 was actually rather useful in 1942, more as an attack plane or strafer rather than for air to air combat. But the Japanese didn't have much in the way of converted bombers for strafing.

The small bombers still can be outfitted with gun noses. But I'd use the small fighters for strafing, Ki 44 is especially appealing for that.

We are back to the engine situation (and the guns).
For some reason the Ki-45 could fly about 1000 miles clean (1400 miles with drop tanks) with a 2 man crew and the Ki-48 needed 4 men to fly 1200-1300miles.
Pilot, Bomb aimer/gunner, radio operator/dorsal gunner, navigator/ventral gunner?

I've said several times that Ki-48 needs to go :)

Sorry, I meant using the Ki-45 as a bomber or any competitor (ki-46).
Roger that.
Ki-45 and -46 need to be designed as a bomber 1st.

We really need to figure out what the Japanese were thinking with those large crews, small bomb loads and poor gun armament.

We got a lot of work to do :)
 
The thing with fighters and bombers is that often they were not designed to pull the same G loading.

Some tales about maneuverable bombers were when they were carrying no bombs and with less than full fuel tanks. Being able to do a loop with lightly loaded bomber does not mean you can do several loops in row or even do one at close to gross weight.
Bombers were used as night fighters because they didn't expect the night bombers to maneuver that hard (British fooled them, but even then they weren't doing over 3 Gs ?)
A twin engine fighter can have a heavier structure weight than a bomber (twin engine dive bombers may be in anther class) and that structure weight has to come out of the bomb load or fuel load or??????
Bigger engines made things a bit easier.
they also made getting off the ground a bit easier for the bombers ;)
 
A twin engine fighter can have a heavier structure weight than a bomber (twin engine dive bombers may be in anther class) and that structure weight has to come out of the bomb load or fuel load or??????
A twin engine fighter must have the heavier structure than a 2-engined bomber :) Meaning that a bomber has the advantage here, that can be transfered into the greater payload.

Bigger engines made things a bit easier.
they also made getting off the ground a bit easier for the bombers ;)

Japanese have had engines with very good power-to-weight ratio, so this helps, too. They also were not shy in implementing Fowler flaps on their combat aircraft, interestingly enough Kawasaki was least into this.
 

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