Ki-43 Hayabusa Performance

[CORSNING]

Good deduction sir. Maybe you should stick around a while and slow
down and do some more research like the rest of us before you post. I hope
you didn't contact Pilawskii, he's somewhat nasty.

 

[Laurelix]

Good deduction sir. Maybe you should stick around a while and slow
down and do some more research like the rest of us before you post. I hope
you didn't contact Pilawskii, he's somewhat nasty.

I'd message him to tell him his source is trash xp

 

[CORSNING]

I do not know what xp means at this time, but I would strongly
recommend against that.

 

[Ivan1GFP]

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.

Hello Laurelix,
I am kind of late in on this discussion. Just out of curiosity, what speed does Francillon give for the N1K2-J?
Is it as bad as the number typically given for the J2M series?

I am curious as to what you calculated for G loads. Remember that the Ki 43-I had much less structural strength than the later aircraft.
As for turn times, I believe that some of your calculations based on wing loading might be a little too simplistic.

Keep in mind the following factors:
None of these aircraft could maintain speed at their maximum turn rate.
As the speed decayed, the maximum G load possible would decrease.
What are you getting for entry and exit speeds for a 360 degree turn?
You might want to consider that at certain altitudes, there is a pretty serious difference in power between Ha-25 / Sakae 12 and Ha-115 / Sakae 21. The critical altitudes are about 4000 meters and 6000 meters respectively.
At sea level though, there is a MASSIVE difference in power.
940 HP versus 1130 HP Take-Off ratings.
Yes, the military power for Sakae 21 is quite a bit closer, but please remember that for the Oscar, TAIC notes that the aircraft is capable of pretty high "Flash Performance" because the pilots apparently disregard the limits in the manual and get away with it.

Also remember that Ki-43-I was swinging a two blade NON Constant Speed propeller and while that lesser propeller may not make a difference in maximum speed, at low speeds, it is a serious disadvantage.

Now what does an engine power / thrust difference have to do with this?
As mentioned before, ALL the aircraft are bleeding speed in a max rate turn.
The power difference may allow one aircraft to maintain its speed for longer and be able to sustain higher G for longer.
You also did not mention if these calculations were done with or without the butterfly flaps in use. Extra engine power would also overcome some of the drag penalty of using the combat flaps.

Hayabusa is a cool aeroplane!
- Ivan.

 

[Laurelix]

Hello Laurelix,
I am kind of late in on this discussion. Just out of curiosity, what speed does Francillon give for the N1K2-J?
Is it as bad as the number typically given for the J2M series?

I am curious as to what you calculated for G loads. Remember that the Ki 43-I had much less structural strength than the later aircraft.
As for turn times, I believe that some of your calculations based on wing loading might be a little too simplistic.

Keep in mind the following factors:
None of these aircraft could maintain speed at their maximum turn rate.
As the speed decayed, the maximum G load possible would decrease.
What are you getting for entry and exit speeds for a 360 degree turn?
You might want to consider that at certain altitudes, there is a pretty serious difference in power between Ha-25 / Sakae 12 and Ha-115 / Sakae 21. The critical altitudes are about 4000 meters and 6000 meters respectively.
At sea level though, there is a MASSIVE difference in power.
940 HP versus 1130 HP Take-Off ratings.
Yes, the military power for Sakae 21 is quite a bit closer, but please remember that for the Oscar, TAIC notes that the aircraft is capable of pretty high "Flash Performance" because the pilots apparently disregard the limits in the manual and get away with it.

Also remember that Ki-43-I was swinging a two blade NON Constant Speed propeller and while that lesser propeller may not make a difference in maximum speed, at low speeds, it is a serious disadvantage.

Now what does an engine power / thrust difference have to do with this?
As mentioned before, ALL the aircraft are bleeding speed in a max rate turn.
The power difference may allow one aircraft to maintain its speed for longer and be able to sustain higher G for longer.
You also did not mention if these calculations were done with or without the butterfly flaps in use. Extra engine power would also overcome some of the drag penalty of using the combat flaps.

Hayabusa is a cool aeroplane!
- Ivan.

structural strength doesnt matter for sustained turn rate because it happens at constant low speed in a horizontal turn. Ki-43-I turn time is out of the Ki-43 manual itself.
the turn times are stated at altitude of 0-1000m
Stall Speed and Power to weight ratio are the 2 biggest factors in sustained turn rate.

regarding N1K2-J, i made a post on it moments ago.
N1K2-J Shiden-Kai Performance

 

[Ivan1GFP]

structural strength doesnt matter for sustained turn rate because it happens at constant low speed in a horizontal turn. Ki-43-I turn time is out of the Ki-43 manual itself.
the turn times are stated at altitude of 0-1000m
Stall Speed and Power to weight ratio are the 2 biggest factors in sustained turn rate.

regarding N1K2-J, i made a post on it moments ago.
N1K2-J Shiden-Kai Performance

Hello Laurelix,
Not having read the Hayabusa's manual, what kind of "low speed" are we talking about here?
Is it enough to pull 6G at the start of the turn?
I am not disputing the time for Ki-43-I, but believe that Ki-43-II might be a bit closer despite the weight difference.
Also, keep in mind that the Ki-43-II ALSO started with the same size wing as Ki-43-I. They just were made stronger so they would not break off so easily.
You might want to adjust your calculation using the same wing planform for the -II and see how close the numbers are.

Stall Speed: Power-ON stall speed is really what you need here and I don't think you can calculate that all too easily.
Power to Weight: It really isn't POWER but THRUST you are interested in here. My point is that Ki-43-II has a pretty significant thrust advantage at low speeds and at sea level and above 4000 meters.

Heading over to see about the Shiden-Kai. It's one of my favourites.

- Ivan.

 

[Laurelix]

Hello Laurelix,
Not having read the Hayabusa's manual, what kind of "low speed" are we talking about here?
Is it enough to pull 6G at the start of the turn?
I am not disputing the time for Ki-43-I, but believe that Ki-43-II might be a bit closer despite the weight difference.
Also, keep in mind that the Ki-43-II ALSO started with the same size wing as Ki-43-I. They just were made stronger so they would not break off so easily.
You might want to adjust your calculation using the same wing planform for the -II and see how close the numbers are.

Stall Speed: Power-ON stall speed is really what you need here and I don't think you can calculate that all too easily.
Power to Weight: It really isn't POWER but THRUST you are interested in here. My point is that Ki-43-II has a pretty significant thrust advantage at low speeds and at sea level and above 4000 meters.

Heading over to see about the Shiden-Kai. It's one of my favourites.

- Ivan.

Maybe but Ki-43-II turn rate should be very similar to Ki-43-III. By low speed i mean its the speed the plane can maintain whilst doing 360 horziontal turn non stop.

 

[Ivan1GFP]

Maybe but Ki-43-II turn rate should be very similar to Ki-43-III. By low speed i mean its the speed the plane can maintain whilst doing 360 horziontal turn non stop.

Hello Laurelix,
Part of the problem with describing the Ki-43-II is that one has to first decide WHICH version we are talking about.
Weights, Armament, Fuel Tanks, Wings, Cowl Shape and probably much more differed during the rather long manufacturing run.

Also, do you mean continuous turn at a constant reduction in speed (which is how most people did their testing) or a constant speed until the fuel runs out which is a pretty meaningless test from a tactical standpoint?

- Ivan.

 

[Laurelix]

Hello Laurelix,
Part of the problem with describing the Ki-43-II is that one has to first decide WHICH version we are talking about.
Weights, Armament, Fuel Tanks, Wings, Cowl Shape and probably much more differed during the rather long manufacturing run.

Also, do you mean continuous turn at a constant reduction in speed (which is how most people did their testing) or a constant speed until the fuel runs out which is a pretty meaningless test from a tactical standpoint?

- Ivan.

Well what matters is the weight, power, wing Area. It's calculated turn rate from the general data. I mean I can calculate their stall speed and you wouldn't doubt their turn rates.

 

[taly01]

What I would love to see is some original data on the later Ki-43-IIb and -II kai and what effect the thrust exhaust stacks actually made IRL.

But they were rejected since the performance degradation compared to the Ki-43-III Ko was severe

On Ki-43-IIIb with 20mm guns I believe this is an English language "myth" that has been repeated over time and is not supported on J-wiki. Indeed the Ki-43-IIIb only added 20cm to fuselage and some 46kg to plane weight. My take is simply the Ki-43-IIIb was too little too late (and the 12.7mm had TA rounds with 3x HE filler of "standard" 12.7mm HE).

My opinion is that if the IJAAF had visionaries in higher ranks the Ki.43 would never have past the Ki.43-II stage. .........

Yes even as a fan of the Ki-43 I have said by Pearl Harbour it was clear the A6M2 was far superior to the Ki-43, and the JAAF should have made a army Zero (but its internal Army vs Navy politics).

Also remember that Ki-43-I was swinging a two blade NON Constant Speed propeller and while that lesser propeller may not make a difference in maximum speed, at low speeds, it is a serious disadvantage.

Ki-43-I propellor types is confused due to the prototypes using basic designs. Air Information Summary #12 report of 3 June 1943 states Ki-43-I has a "DeHavilland" type constant speed variable pitch propellor.

 

[Ivan1GFP]

Hello Taly01,

Yes even as a fan of the Ki-43 I have said by Pearl Harbour it was clear the A6M2 was far superior to the Ki-43, and the JAAF should have made a army Zero (but its internal Army vs Navy politics).

It is a pretty hard call as to which was superior. Both had their problems.

Ki-43-I propellor types is confused due to the prototypes using basic designs. Air Information Summary #12 report of 3 June 1943 states Ki-43-I has a "DeHavilland" type constant speed variable pitch propellor.

Thanks for the information. Do you know where I can find this report?
I just did some calculations and have to take back what I stated earlier.
The propeller power coefficients between -I and -II were actually not that different.

- Ivan.

- Ivan.

 

[taly01]

Hi Ivan, The wing failures and aileron problems at high speeds of the early Zero is something I only recently found out about, so with the Ki-43-I they were both not safe divers!

Thanks for the information. Do you know where I can find this report?...

Report covers 1942 Japanese fighters, also supports current knowledge that even later Ki-43-I still used 1x7.7 and 1x12.7.
Researcher@Large - 1943 Air Information Summary 12

The propeller power coefficients between -I and -II were actually not that different.

I have been looking at 2 blade vs 3 blade prop sizes (actually for 1/48 models), the 2 blade prop is only slightly longer but blades are fatter. Is their some calculation for HP/blade?

 

[CORSNING]

Ki.43-Ib turn time is 14 seconds. Not 11-12
A6M2 model 21 turn time is 14.1 seconds.

Laurelix,
Where did the turn times come from for the Ki.44-II and J2M3?

 

[Ivan1GFP]

Hello Taly01,

Hi Ivan, The wing failures and aileron problems at high speeds of the early Zero is something I only recently found out about, so with the Ki-43-I they were both not safe divers!

My understanding is that the failures on the early A6M were not so much a structural weakness problem as a matter of harmonics and flutter problems. A hobby shop in my area that closed many years back used to have a section of wing skin from a Ki-43. It was amazingly flimsy.

Report covers 1942 Japanese fighters, also supports current knowledge that even later Ki-43-I still used 1x7.7 and 1x12.7.
Researcher@Large - 1943 Air Information Summary 12

Thanks for the link. This report makes for some really good reading. An interesting note is the speed that is listed for the "Hap" which is a bit higher than other sources show.

I have been looking at 2 blade vs 3 blade prop sizes (actually for 1/48 models), the 2 blade prop is only slightly longer but blades are fatter. Is their some calculation for HP/blade?

You are correct, the propeller diameters are 2.900 meters for Ki-43-I and 2.800 meters for Ki-43-II.
There isn't much difference there, but there are more factors involved.

The concept to look at is something called "Propeller Power Coefficient" which is described as "Power" or Cp at this site:
Propeller Formulas

Basically it is a relationship of "How Hard" the Engine can turn the Propeller as compared to how hard the Propeller is to turn. It isn't Torque and it isn't Power, but rather is a non-dimensional number.
Note that the formula is fairly simple and doesn't take into account things like number of propeller blades or blade profiles or anything like that. I see those factors as modifier when comparing different shaped propellers.
I believe it is pretty safe to assume that a 3 blade propeller with the same blade profile as a 2 blade would have 50% more ability to absorb power.

I am sure there are some folks out there who are probably thinking that the efficiency of a 2 blade propeller would be higher because fewer blades are more efficient. At least that is the Theory.
From what I have seen, this is not supported by actual experimental data including NACA reports. Peak efficiency tends to be about the same regardless of the number of blades.

Now comes the opinion part: (Not my original thinking)
Fewer blades ARE more efficient but only if the propeller has no forward motion and each blade is going through the turbulence / wake of the other blades. In practical use, the propeller is moving forward and the blades don't interfere much with each other because each blade takes a path through a different part of the airstream.
Although it isn't seen much, there ARE single blade propellers with a counterweight. Typically they are seen in very light flying model aeroplanes. I believe that in those cases, there are other factors involved such as a limited number of rotations of the propeller (rubber band power) or very low torque and very low forward speeds so that even with two blades, they would operate in each other's wake.

Here are the actual numbers I used for calculations:
Ki-43-I
Power: 990 HP @ 2700 RPM (Take-Off and WEP at SL)
Propeller: 2.900 meters (9.514 feet)
Reduction: 16/11 or 1.454545
Cp = 0.1042

Ki-43-II
Power: 1150 HP @ 2800 RPM (Take-Off and WEP at SL)
Propeller 2.800 meters (9.186 feet)
Reduction: 12/7 or 1.7428 - This is probably the biggest difference between the two.
Cp = 0.2118

Yes, the number is twice as high for the Ki-43-II, but when adjusted for two blade versus three blade propellers and using Military HP, they get a little closer. WW2 prop driven fighters tend to cluster around the 0.13 to 0.17 range. The Ki-43-I is about middle of the pack and Ki-43-II is just above the high end of this range.

- Ivan.

 

[Laurelix]

Ki.43-Ib turn time is 14 seconds. Not 11-12
A6M2 model 21 turn time is 14.1 seconds.

Laurelix,
Where did the turn times come from for the Ki.44-II and J2M3?

Calculated
Ki-44 has 1.41 CL_Max Wing Lift Coefficient
J2M with laminar wings has 1.33-1.34 CL_Max wing lift Coefficient

In my calculation ^^^

Ki-43-I manual states 11 seconds at 0-1000m

Your 14 sec turn time source is listed at 4000m. The higher the planes go the less air thrrr is and thus the higher the stall speed and also thus the worse turn rate compared to sea level.

 

[Ivan1GFP]

Calculated
Ki-44 has 1.41 CL_Max Wing Lift Coefficient
J2M with laminar wings has 1.33-1.34 CL_Max wing lift Coefficient

In my calculation ^^^

Ki-43-I manual states 11 seconds at 0-1000m

Your 14 sec turn time source is listed at 4000m. The higher the planes go the less air thrrr is and thus the higher the stall speed and also thus the worse turn rate compared to sea level.

Hello Laurelix,

How are you getting your CL values?
Normally one uses the Stall Speed at a particular Aircraft Weight to calculate max CL, but from these threads, it seems like you are calculating the stall speeds as well which I presumed were because you KNEW the max CL.

Are the max CL values from experimental data or are you calculating them as well?

- Ivan.

 

[CORSNING]

Laurelix Post #35:

In my calculation ^^^
Yes sir, I believe that.

Ki-43-I manual states 11 seconds at 0-1000m
No sir, it does not. You plainly stated in another thread that you calculated
that figure, after being questioned by me.

Your 14 sec turn time source is listed at 4000m.
Yes sir, that is correct. The source was Erik Pilawskii's "Fighter Aircraft Performance
of WW2 ". And the 14 second turn was observed, not calculated.

The higher the planes go the less air thrrr is and thus the higher the stall speed and also thus the worse turn rate compared to sea level.[/QUOTE]
Oh really? The following are turn times L/R (if two are given) for 1,000 m. and 4,000 m.
All figures given are observed (actual) not calculated.
Aircraft............1,000 m.........4,000 m
MS.406..............16.....................15
Fw-190A-4......22/23...............22.8
Fw-190D-9......22/23.................24
Bf 109E-4..........25.....................25
Bf 109F-4.......19.6/20.5..........20.5
Bf 109G2/R6..22.6/22.8..........22.6
Spitfire Vb.......18.8.................17.5
Spitfire LF IX...18.5.................18.5
Hurricane IIb...20.5.................16.5
LaGG-3 S.28.....19....................18.5
I-16 type 24....17/18...............16.5

I have at least 184 observed turn times for WW2 fighters. They are all
pretty much the same as above.

 

[Laurelix]

Laurelix Post #35:

In my calculation ^^^
Yes sir, I believe that.

Ki-43-I manual states 11 seconds at 0-1000m
No sir, it does not. You plainly stated in another thread that you calculated
that figure, after being questioned by me.

Your 14 sec turn time source is listed at 4000m.
Yes sir, that is correct. The source was Erik Pilawskii's "Fighter Aircraft Performance
of WW2 ". And the 14 second turn was observed, not calculated.

The higher the planes go the less air thrrr is and thus the higher the stall speed and also thus the worse turn rate compared to sea level.

Oh really? The following are turn times L/R (if two are given) for 1,000 m. and 4,000 m.
All figures given are observed (actual) not calculated.
Aircraft............1,000 m.........4,000 m
MS.406..............16.....................15
Fw-190A-4......22/23...............22.8
Fw-190D-9......22/23.................24
Bf 109E-4..........25.....................25
Bf 109F-4.......19.6/20.5..........20.5
Bf 109G2/R6..22.6/22.8..........22.6
Spitfire Vb.......18.8.................17.5
Spitfire LF IX...18.5.................18.5
Hurricane IIb...20.5.................16.5
LaGG-3 S.28.....19....................18.5
I-16 type 24....17/18...............16.5

I have at least 184 observed turn times for WW2 fighters. They are all
pretty much the same as above. [/QUOTE]
something is fishy here, someone of these planes have better sustained turn at 4000m than at 1000m.

Ki-84:
Loaded Weight: 3600kg
Wing Area: 21m2
Wing Lift Coefficient: 1.46 CL_Max (according to the manual)
Air Density:
1.225kg/m3 at Sea Level
0.8194kg/m3 at 4000m

Stall Speed: (Power on Stall, No Flaps)
156km/h IAS at Sea Level
191km/h IAS at 4000m

Heres is the equation to calculate stall speed...
V = Stall Speed in m/s
L = Lift Force [You multiply the loaded weight by gravity] (in this case its 3600 x 9.81 = 35316 Newtons
CL = Wing Lift Coefficient
P = Air Density
A = Wing Area (metres squared)

At Sea level Ki-84 has lower stall speed and better power to weight ratio. At 4000m it has higher stall speed and worse power to weight ratio. Ki-43 Also obeys physics just like Ki-84...

Soviets for example tested BF-109E turn time to be 21 seconds whilst the British concluded 17 seconds turn time.

 

[CORSNING]

Soviets for example tested BF-109E turn time to be 21 seconds whilst the British concluded 17 seconds turn time.[/QUOTE]
I will need to see that 17 second turn time report to believe it. The Germans tested
the Bf 109E-3 at 1,000 m. and came up with 18.92 seconds. I am guessing this test
was under ideal conditions.
All the best calculations in the world are still just that, calculations. I do use calculations,
but only when no actual testing has been done. To the best of my knowledge I never
use calculated turn time unless I state that fact and give source.

PS: One other note: There was no statement in any of the observed turn time
test that state anything about stall speed being used for there minimum turn
times. Stall speed is used for minimum circumference, not minimum time.

 

[Ivan1GFP]

Ki-84:
Loaded Weight: 3600kg
Wing Area: 21m2
Wing Lift Coefficient: 1.46 CL_Max (according to the manual)
Air Density:
1.225kg/m3 at Sea Level
0.8194kg/m3 at 4000m

Stall Speed: (Power on Stall, No Flaps)
156km/h IAS at Sea Level
191km/h IAS at 4000m

Hello Laurelix,

I believe I found your error.
See the Bold Underline above.

Stall speed in INDICATED Air Speed does not change with altitude.
Stall speed in TRUE Air Speed increases.
Do you remember I asked earlier about entry and exit speeds from the turns?
At higher altitude, a turn can be entered at higher true airspeed and I believe that although the radius is larger, the turn may end up quicker. I have seen photographs of this with F-16 versus F-4, in which the F-16 made a larger radius turn but turned at a faster rate in degrees per second, but to be sure in this case requires a few calculations.
Intuitively it seems like it should work.

Hello Corsning,

Stall speed actually does need to be considered for minimum turn times.
The reason is that you want to have enough speed to be able to sustain a turn without encountering an accelerated stall (perhaps at 6G) but don't want to be going so fast that the turn has too great a circumference and increases time.
Centripetal force increases as speed increases according to M*V^2/R, so going a little faster also makes numbers worse if the load limit on the pilot is limited.
....And then the turn needs to finish with enough speed to still be abl to pull some reasonable G which is probably a lot less than the peak acceleration.
It is a pretty fine balancing act as I see it and probably why different pilots sometimes get different results if they started at different speeds.

- Ivan.