Ki-43 Hayabusa Performance

Ki-43-I:
Empty Weight: 1580kg
Loaded Weight: 2243kg
Wing Area: 22.0m2
Engine: Ha-25
Take off: 990hp / 970hp at 3400m
-
Max Speed: (Military Power)
414kph at Sea Level
495km/h at 4000m
-
Rate of Climb: (Military Power)
Time to 1000m: 1:11
Time to 2000m: 2:12
Time to 3000m: 3:10
Time to 4000m: 4:08
Time to 5000m: 5:13
Time to 6000m: 6:21
-
Turn Time: (Military Power, SL)
14 sec
-
Armament:
Ko: 2x 7.7mm Type 89 (500 rounds per gun)
Otsu: 1x 7.7mm Type 89 / 1x 12.7mm Type 1
Hei: 2x 12.7mm Type 1 (270 rounds per gun)

——————————————————

Ki-43-II Ko
Empty Weight: 1729kg
Loaded Weight: 2590kg
Wing Area: 21.4m2
Engine: Ha-115
Take off: 1120hp / 1020hp at 2800m / 980hp at 5600m
-
Max Speed: (Military Power)
445kph at Sea Level
515km/h at 6000m
508km/h at 8000m
-
Rate of Climb: (Military Power)
Time to 1000m: 1:13
Time to 2000m: 2:25
Time to 3000m: 3:30
Time to 4000m: 4:35
Time to 5000m: 5:49
Time to 6000m: 7:24
Time to 7000m: 9:12
Time to 8000m: 11:09
-
Turn Time: (Military Power, SL)
16 seconds
-
Armament:
2x 12.7mm Type 1 (270 rounds per gun)

———————————————-

Ki-43-II Kai
Empty Weight: ???
Loaded Weight: ???
Wing Area: 21.4m2
Engine: Ha-115
Take off: 1120hp / 1020hp at 2800m / 980hp at 5600m
-
Max Speed: (Military Power) [Estimated]
465km/h at Sea Level
535km/h at 6000m
-
Rate of Climb: (Military Power) [Estimated]
Time to 5000m: 5:29
-
Turn Time: (Military Power, SL)
16 seconds
-
Armament:
2x 12.7mm Type 1 (270 rounds per gun)

———————————————-

Ki-43-III Ko
Empty Weight: 2040kg
Loaded Weight: 2725kg
Wing Area: 21.4m2
Engine: Ha-115-II
Take off: 1190hp / 1230hp at 2800m / 950hp at 6800m
-
Max Speed: (WEP)
490km/h at Sea Level
555km/h at 6100m
-
Rate of Climb: (Military Power)
Time to 5000m: 5:19
Time to 8000m: 10:50
-
Turn Time: (Military Power, SL)
16 sec
-
Armament:
2x 12.7mm Type 1 (270 rounds per gun)

———————————————-

Ki-43-III Otsu
Empty Weight: ???
Loaded Weight: ???
Wing Area: 21.4m2
Engine: Ha-115-II
Take off: 1190hp / 1230hp at 2800m / 950hp at 6800m
-
Max Speed: (WEP)
???km/h at 6100m
-
Rate of Climb: (Military Power)
Time to 5000m: ???
Time to 8000m: ???
-
Turn Time:
???
-
Armament:
2x 20mm Ho-5 (150 rounds per gun)

Note: Ki-43-III Otsu underwent major modifications to fit the 20mm guns in place. This added more drag and weight. Overall its performance was worse than Ki-43-III Ko and the Japanese only built 2 prototypes and abandoned the project.

———————————————-

Ki-43-IV - Unofficial name, it was considered but it didn't go anywhere. It would have been a Ki-43, armed with 20mm Ho-5 cannons and powered by Ha-112 engine.


Effectiveness of the Type 1 12.7mm / 12.7mm Ho-103
12.7mm Ho-103 ammunition

Laurilix,
My question to you sir is, where did your figures for turn times come
from? Erik Pilawskii has published the turn times for the Ki.43-1b otsu
at 4,000 m. to be 14.0 seconds/360 degrees (observed). He published
the Ki.43-IIa ko as 14.5 seconds/360 degrees (observed) at the same
altitude.
I am also curious where any of you information for the Ki.43-IV came
from? Rene J. Francillon states in his book "Japanese Aircraft of the
Pacific War" the following: " The last variant designed by Nakajima was
the Ki-43-IIIa of which ten prototypes were built, starting in May 1944.
Similar in airframe and armament to the Ki-43-II Kai, it was powered by
a Nakajima Ha-115-II rated at 1,230 hp. at 2,800 m. (9185 ft.). Production
aircraft, designated Army Type I Fighter Model 3A, were built by
Tachikawa Hikoki KK., which company also built two prototypes of the
Ki-43-IIIb.
Sorry, no Ki.43-IV, not even in legends.

PS: I believe you are fairly close on the turn time of the Ki.43-III.

Well firstly the air density is different at 4000m compared to 0-1000m. The higher you go, the less air and the worse the turn rate.

Also there's no way that Ki-43-II with smaller wing Area and more weight would have such a small difference in turn Rate compared to Ki-43-I
500kg difference nvm the smaller wing area. The turns rates are calculated by me.

Ki-43-IIIa were mass produced
Ki-43-IIIb, 2 prototypes of these
Ki-43-IV was planned. It was to be made with wood as well as metal due to material shortage and was to have the 1500hp Ha-112 engine

The reason i want to mention Ki-43-IV is because lot of confusion was made over the past in source translation. There are sources that say Ki-43-IIIb used Ha-112 1500hp engine which is false. It used same engine as the Ko.

Laurelix said:

Well firstly the air density is different at 4000m compared to 0-1000m. The higher you go, the less air and the worse the turn rate.

Not necessarily so. The less air pressure allows greater aircraft speed. In some aircraft the
turn time actually increases from 1,000 m. vs. 4,000 m simply because the A/C is able to
travel at greater velocities in a wider circle.

Also there's no way that Ki-43-II with smaller wing Area and more weight would have such a small difference in turn Rate compared to Ki-43-I

As I stated above, it is the increase in speed that allows this to happen.

500kg difference nvm the smaller wing area. The turns rates are calculated by me.

You should recalculate.

Ki-43-IIIa were mass produced

What is your definition of mass produced?

Ki-43-IIIb, 10 prototypes of these

Both William Green and Rene J. Francillon agree that there were two prototypes...???

Ki-43-IV was planned. It was to be made with wood as well as metal due to material shortage and was to have the 1500hp Ha-112 engine

What are your sources for this information?

The reason i want to mention Ki-43-IV is because lot of confusion was made over the past in source translation. There are sources that say Ki-43-IIIb used Ha-112 1500hp engine which is false. It used same engine as the Ko.

Click to expand...

I don't know of any confusion.? The Ki-43-IIIb two prototypes were powered by the
Mitsubishi Ha-112 with a constant-speed three-blade metal propeller produced the
following: 1,300 hp./T.O., 1,200 hp./3,000 m., 1,100 hp./6,200 m.

CORSNING said:

I don't know of any confusion.? The Ki-43-IIIb two prototypes were powered by the
Mitsubishi Ha-112 with a constant-speed three-blade metal propeller produced the
following: 1,300 hp./T.O., 1,200 hp./3,000 m., 1,100 hp./6,200 m.

Click to expand...

Look...
Ki-43-I - 950hp engine
Ko / Otsu / Hei = armament difference and modifications

Ki-43-II - as soon as engine changed to Ha-115 it became Hayabusa 2.

Ki-43-III - again engine was changed to Ha-115-II and it became Hayahusa 3.
Both the Ko and Otsu had same engine

Ki-43-III Otsu having Ha-112 is incorrect. Francillion has many innacuracies and that's one of them. If it had Ha-112... the Japanese would of called it the Ki-43-IV

Yes only 2 prototypes built.

You yourself said Ki-43-III has about correct turn time at 16 seconds. Ki-43-II is like 150kg lighter and same wings. Their engine power isn't much different. So 15-16 sec on Ki-43-II is correct.

Ki-43-I is 500kg lighter and has bigger wings. When you compare the power to Weight and wing Loading and stall speed compared to A6M2, the conclusion is the Ki-43-I should turn better than A6M2 by quiet a bit and the A6M2 should be outturning Ki-43-II. So the Conclusion = 12 sec sustained turn time for Ki-43-I

When I look at Francillon and see the top speed stated for N1K2-J, my eyes bleed.
Francillon also states the Ki-43-II achieved its top speed at 4000m, when both TAIC and Japanese tests agree it was at 6000m.

Re-Calculated the turn rates based on the fact Ki-43-I manual states 11 second turn time.

If the 11 seconds turn time came from the Ki.43-I manual I would
be very interested to see a copy of that page.

According to Erik Pilawskii the Ki.27b had a turn rate at 4,000 m.
of 13.0 seconds, the Ki.43-1b 14.0 seconds and the Ki.43-IIa 14.5 seconds
(observed).

For what it is worth, Wikipedia, William Green and Gordon Swansborough
also agree that the Ki.43-IIIb were equipped with the Ha 112-I.
Francillon is only human. He may make some mistakes from time to time.

CORSNING said:

If the 11 seconds turn time came from the Ki.43-I manual I would
be very interested to see a copy of that page.

According to Erik Pilawskii the Ki.27b had a turn rate at 4,000 m.
of 13.0 seconds, the Ki.43-1b 14.0 seconds and the Ki.43-IIa 14.5 seconds
(observed).

For what it is worth, Wikipedia, William Green and Gordon Swansborough
also agree that the Ki.43-IIIb were equipped with the Ha 112(-II?).
Francillon is only human. He may make some mistakes from time to time.

Click to expand...

My turn rates are calculated at sea level where the air density is 1.225kg/m3
At 4000m the air density is 0.8194kg/m3

So if Ki-43-I has 14 sec at 4000m, it is roughly 11 sec at sea level. Also at 4000m the engine has less power than at sea level, effecting the power to Weight in negative way further reducing the sustained turn time

There's no way there is only 0.5 sec turn rate difference between the Hayabusa 1 and 2.

Ha-112-II is a 1500hp engine and it's used on Ki-100. Ki-43-III didn't have this engine. It had Ha-115-II

I think you should throw that francillon book in the bin. Bunrindo is better source for Japanese planes. It's a secondary source that uses primary sources such as Japanese manuals as it's source.

Laurelix said:

My turn rates are calculated at sea level
where the air density is 1.225kg/m3 At 4000m the air density is 0.8194kg/m3
Your turn rates? I believe you stated in post #6, and I quote, " Re-Calculated the
turn rates based on the fact Ki-43-I manual states 11 seconds turn time."
Woops! .....I actually mostly apologize sir. I couldn't help that weak moment.

"So if Ki-43-I has 14 sec at 4000m, it is roughly 11 sec at sea level."
Wow, on what do you base that theory? I have the Russian actual figures for 99
aircraft turn times at 1,000 m. and 85 aircraft turn times observed figures at 4,000 m.
The turn times for the aircraft I have both figures for are generally equal or favor the
higher altitude where the air is less dense which posses less resistance, allowing the
aircraft to travel at a greater speed through the turn. Larger turning circle yes, lower
turn time yes. I would like to give your statements some credence but the truth is
the Yak-7A turn times was 21-22 seconds @ 1,000 m. vs. 19.0 seconds @ 4,000 m.

Also at 4000m the engine has less power than at sea level, effecting the power to Weight in negative way further reducing the sustained turn time
One must keep in mind that the weight of the aircraft decreases with altitude (fuel used).
If you look at the charts that you have posted you will observe the power drop from S.L.
to 3,400 m. is only 20 hp., 990 vs 970 hp for the Ki.43-i.

There's no way there is only 0.5 sec turn rate difference between the Hayabusa 1 and 2.
The wing area of the Ki.43-I is 236.805 sq. ft. and the wing area of the Ki.43-II is
230.367 sq. ft. The power difference is about 950 vs 1050 hp. at 4,000 m. Shorter
wing span more power.

Ha-112-II is a 1500hp engine and it's used on Ki-100. Ki-43-III didn't have this engine. It had Ha-115-II
OK, I revised my post,....for now.

I think you should throw that francillon book in the bin.
Nope, I'm good.

Bunrindo is better source for Japanese planes.
That is an opinion.


It's a secondary source that uses primary sources such as Japanese manuals as it's source.
I do not know that for a fact, but one must keep in mind that the Japanese
published figures were for military rating of the engine, not war emergency (combat).
View attachment 551019

Click to expand...

I would just like to point out that the aircraft's full throttle height is 4,000 m. That
means that its best altitude of performance was 4,000 m.

For those that are following this thread I found a very interesting
tidbit. In Profile Publications "The Nakajima Ki-43 Hayabusa number 46"
the authors are Martin C. Windrow and R. F. Francillon.
"The final development of the Hayabusa was the Ki-43-IIIb, a version
of which only two prototype had been completed before the Super-
fortress Enola Gay opened the last brief chapter of the Pacific war.
Developed by Tachikawa, the -IIIb featured extensive modification
of wing and fuselage structure and mounted two HO-5 20 mm. Cannon.
This version was intended as a B-29 interceptor and was powered by
a 1,250 hp. Mitsubishi Ha-32/42 engine.......

Just because an aircraft has top speed at certain altitude, does not mean the engine provides the most power at it.

Look at Ash-89FN engine. 1850hp at SL and only around 1250hp at 6000m
Yet Lavochkin top speed is at 6000m. Why? The reduced air density also means less drag which means that even with less horsepower, the lower drag allows it to go faster than when it has more power but more air resistance at sea level.

If Ki-43-III Otsu used a different engine, it would of been called the Hayabusa 4. Not a IIIb. As soon as you change the engine, it's no longer a hayabusa 3.



The Ki-43-III Otsu had to be modified heavily to fit 20mm Ho-5's cannons with it having Ha-115-II... never mind putting bigger engine into it like the Ha-112....

Ki-43-IV which was planned was to be armed with 20mm Ho-5 and to have that new engine. However western sources confused it to the Ki-43-IIIb. This is why I even mentioned the Ki-43-IV to show distinction to the Ki-43-IIIb because I'm aware of the confusion. If you don't believe me, look at the photos and tell me the Ki-43-III Ko and Ki-43-III Otsu don't have the very same engine...

The plane Francillon is talking about is not the Ki-43-IIIb but the planned Ki-43-IV which was not built. However yes 2 Ki-43-III Otsu's were built but they had Ha-115-II like the Ki-43-III Ko. But they were rejected since the performance degradation compared to the Ki-43-III Ko was severe. The added weight and drag whilst having same engine is basically what the Ki-43-III Otsu was.

Laurelix said:

Just because an aircraft has top speed at certain altitude, does not mean the engine provides the most power at it.
I believe I acknowledge that fact in my post 990 vs.970 hp. That does not change
the facts.

Look at Ash-89FN engine. 1850hp at SL and only around 1250hp at 6000m
Yet Lavochkin top speed is at 6000m. Why? The reduced air density also means less drag which means that even with less horsepower, the lower drag allows it to go faster than when it has more power but more air resistance at sea level.
I am not quite sure what your point was here, but I think you have just solidified
my point.

If Ki-43-III Otsu used a different engine, it would of been called the Hayabusa 4. Not a IIIb. As soon as you change the engine, it's no longer a hayabusa 3.
No! you would have called it something different, apparently not Nakajima.

View attachment 551069

The Ki-43-III Otsu had to be modified heavily to fit 20mm Ho-5's cannons with it having Ha-115-II... never mind putting bigger engine into it like the Ha-112....
OK, so?

Ki-43-IV which was planned was to be armed with 20mm Ho-5 and to have that new engine. However western sources confused it to the Ki-43-IIIb. This is why I even mentioned the Ki-43-IV to show distinction to the Ki-43-IIIb because I'm aware of the confusion. If you don't believe me, look at the photos and tell me the Ki-43-III Ko and Ki-43-III Otsu don't have the very same engine...
I do not believe anybody but you confused it to be anything other than
what Nakajima designated it as.

The plane Francillon is talking about is not the Ki-43-IIIb but the planned Ki-43-IV which was not built. However yes 2 Ki-43-III Otsu's were built but they had Ha-115-II like the Ki-43-III Ko. But they were rejected since the performance degradation compared to the Ki-43-III Ko was severe. The added weight and drag whilst having same engine is basically what the Ki-43-III Otsu was.

Click to expand...

Maybe it is time you quit posting your opinions on this site and contact Francillon, Green and Swansborough and give them a good piece of your mind...?

I forgot to add, I wouldn't bother contacting Mr. Pilawskii if
I were you. He is very opinionated and will have no problem kicking
your @$$ with the truth.

Well since there is confusion regarding this, its better to keep out out of the post. they are meaningless prototypes anyways.
If Ki-43-IIIb did really have Ha-112, i found a secondary source that states:
585km/h at 6800m at military power

Laurelix said:

Well since there is confusion regarding this, its better to keep out out of the post. they are meaningless prototypes anyways.
If Ki-43-IIIb did really have Ha-112, i found a secondary source that states:
585km/h at 6800m at military power

Click to expand...

My opinion is that if the IJAAF had visionaries in higher ranks the Ki.43 would never have
past the Ki.43-II stage. The Ki.44-I was an improvement and the Ki.44-II was a tremendous
leap forward for Japan. P-51A pilot and ace Tex Hill believe at first that the Ki.44-II was more
aircraft than they could deal with. He went straight to Chennaut with that information.

As a common knowledge in Japan, any Nakajima Ki-43s did not adopt Mitsubishi engines.
Nakajima considered Ha-45(Nakajima), Ha-112-II(Mitsubishi) and Ha-33-42(Mitsubishi) for the upgraded version of Ki-43-III but this was ended as a desk plan. There was no formal model as Ki-43-IV.

Thank you Shinpachi for your reaffirmation. My question to you sir is, what
engine was actually installed in the Ki.43-IIIb Otsu?

It was Ha-115-II which was a water-methanol injection type but did not necessarily work well.
This would be why Nakajima considered better engines, even Mitsubishi's.

Laurelix,
I stand corrected sir in the engine compartment. You have some
good information to add. I just ask that you spend more time researching
your information before you post.

Sinpachi,
Thank you for all your input sir.

CORSNING said:

Laurelix,
I stand corrected sir in the engine compartment. You have some
good information to add. I just ask that you spend more time researching
you information before you post.

Sinpachi-San,
Thank you for all your input sir.

Click to expand...

I just relied on the Japanese classification system.

Ki-61-I used the 1175 PS engine.
It was still Tony 1 no matter the different variants.

BUT as soon as the engine was changed, it became Ki-61-II. That's why I know Ki-43-III Otsu would have same engine as the Ko.