N1K, J2M and Ki-44 vs. 1941 and 1942 vintage Bf 109

[Shortround6]

Spring '45; flying a P-47 try to turn with a Me 262 at 450 mph

Well, the P-47 isn't going to be doing 450mph while turning, unless in a dive.

One the other hand, the P-47 had a wing that was 28% bigger than the wing on the 262.
Even if the P-47 is carrying a larger percentage of it's take off fuel (having used drop tanks) and the 262 has used a higher percentage of it's take off fuel the 262 cannot turn with the P-47. The clean loaded weight is less than 500lbs apart even with drop tanks the P-47 is not going to be totally full of internal fuel.
If the 262 slows down enough for the slats to come out it is in serious trouble, if not from the plane it was trying to hit but from his squadron mates.

 

[Ivan1GFP]

That is not a P-36 in the photo.

I find the P-36/P-40 series interesting because from the firewall back we have the same airplane (wing, fuselage, tail, etc) but powered by number of different engines and some rather different performance envelopes. It was not until the P-40Q that there was much change in either the wing or fuselage.
As I said, the plane in the photo was a P-40 (no letter) that P & W got ahold of an stuck a two stage engine similar to the engine in the F4F-4 Wildcat.
Granted in had no guns and no armor but it wound up being the 4th fastest P-40 ever built. It was faster than the P-40F/L by a measurable margin.
the P & W home Field was also home to an training squadron of P-40Fs and the experimental plane often flew mock dogfights against the P-40Fs.

The Point is that the large amount of power the P-40Q had, it wasn't much faster than the Hawk 81 experimental.
So how do you judge performance based on looks?

Here is another picture.
View attachment 723571
The two big scoops don't look very streamlined. The cowl opening doesn't look like anything special.
The exhaust pipes and ducts are very out of the ordinary for 1942/43.

This thing was supposed to be about as fast in 1942 as a Ki 84 was in 1944 according to some sources on Japanese aircraft.
The P-40Q was about as fast as some people claim the the Ki-84 was if it hand good fuel.

What I am saying is that is very hard to base anything on "looks".

Hello Shortround6,
In actuality, when discussing the P-36 / P-40 series of aircraft, there are at least three distinct types of airframes. There are four if the P-40Q is included, but we will ignore that one for now. The first type, is the P-36 or Hawk 75 according to the Curtiss designation. Although the prototype P-37 / P-40 was based on the P-36, production models differed a bit. They were the Hawk 81 series and were the P-40 through P-40C. Although superficially, only the tail gear is different, the internal equipment isn't all the same and I don't believe the dimensions are all the same either. Look at the fuselage fuel tank for an obvious difference. The P-40 got a pretty radical change with the P-40D model (Curtiss Hawk 87). The P-40 fuselage is constructed as an upper and lower half and the entire upper half was replaced. That is why the earlier aircraft look slightly hump backed while later aircraft do not. Of course there was also the lengthening of the tail starting with some models of the P-40K and P-40F/L. The P-40Q actually doesn't have much similarity to the earlier aircraft other than name and some construction methods and equipment such as the goofy landing gear.
As for mock dogfights, the best model of P-40 depends on the altitude. At low altitudes, the P-40E and P-40K were much superior to the Merlin powered P-40F/L because of the ability of the V-1710 with the smaller supercharger impeller to tolerate a lot more boost than officially listed. The difference in straight line performance changed at about 17-18,000 feet but even then, the Merlins were heavier and worse balanced aircraft with heavier engines and radiators.

I don't know that this really changes the substance of the discussion to any meaningful degree, but it is worth noting that just because they look similar does not mean they actually are.

On a more related note, from casual review, it appears to me that relatively low boosted Japanese engines with a maximum manifold pressure of +300-350 mm seem to not require Water Methanol injection past cruise settings. It also seems rather peculiar that the Japanese Army managed to get the Sakae engine to run reliably with Water Methanol while the Navy did not.

- Ivan.

 

[Shortround6]

There are four if the P-40Q is included, but we will ignore that one for now. The first type, is the P-36 or Hawk 75 according to the Curtiss designation. Although the prototype P-37 / P-40 was based on the P-36, production models differed a bit. They were the Hawk 81 series and were the P-40 through P-40C. Although superficially, only the tail gear is different, the internal equipment isn't all the same and I don't believe the dimensions are all the same either. Look at the fuselage fuel tank for an obvious difference. The P-40 got a pretty radical change with the P-40D model (Curtiss Hawk 87). The P-40 fuselage is constructed as an upper and lower half and the entire upper half was replaced. That is why the earlier aircraft look slightly hump backed while later aircraft do not. Of course there was also the lengthening of the tail starting with some models of the P-40K and P-40F/L. The P-40Q actually doesn't have much similarity to the earlier aircraft other than name and some construction methods and equipment such as the goofy landing gear.

Yes you had the Hawk 75, the Hawk 81 (P-40 through P-40C/Tomahawks) and the Hawk 87 (P-40D through N) and there were quite a few internal changes. Oil tank for one went from behind the engine on the 75 to behind the pilot on 81 to back behind the engine on 87.

However it appears that the wing, while internal structure changed (guns and beefing up) the external shape did not. Same span, same plan form, same airfoil, same flaps and ailerons.
Wing gained 250-265lbs in weight be didn't change shape (aerodynamics)
Pretty much the same for the tail, horizontal stabilizer and elevators stayed the same and in the same location. The vertical fin/rudder also stayed pretty much the same even when the moved it back 20 inches. Some of them got a small fin addition. The bigger fin addition went away or got smaller when they moved the vertical fin back.
There were minor differences in the Canopy and wind screen. But no external BP glass or Malcom hoods , except for the Q's, bubble canopies.

The landing gear changed a bit in length but from the aerodynamic view the change was from the 75 to 81 when they changed the doors and got rid of the wheel covers on the Hawk 75, which never came back even on the Q's.

Very fighters changed as little aerodynamically as the Hawk series from beginning to end, especially considering the changes in engines. Five different radials (or more depending on how you count the various Cyclone 9s or the early 2 stage R-1830?) two different Allisons (shape not power output) and not counting the Q and the Merlin.

According to some accounts the Qs just cut 1 ft off each wing tip. No change to the leading edge or ailerons. Yes, a lot changed to fuselage.

It does make a good plane for comparing the drag of radials vs V-12 engines as so little was changed. And we have several different V-12s and several different radials to hep average things out. We also have the Hawk 81 P & W Special to help show how radial engine installations progressed.

The Hawk 87s got a little skinner from top to bottom (they didn't have to look over the top of the radial engines anymore) but the Hawk 75 fuselage was pretty skinny side to side even at the beginning. Apparently Berlin/Curtiss didn't subscribe to tear drop school of streamlining.

 

[GregP]

Yes you had the Hawk 75, the Hawk 81 (P-40 through P-40C/Tomahawks) and the Hawk 87 (P-40D through N) and there were quite a few internal changes. Oil tank for one went from behind the engine on the 75 to behind the pilot on 81 to back behind the engine on 87.

However it appears that the wing, while internal structure changed (guns and beefing up) the external shape did not. Same span, same plan form, same airfoil, same flaps and ailerons.
Wing gained 250-265lbs in weight be didn't change shape (aerodynamics)
Pretty much the same for the tail, horizontal stabilizer and elevators stayed the same and in the same location. The vertical fin/rudder also stayed pretty much the same even when the moved it back 20 inches. Some of them got a small fin addition. The bigger fin addition went away or got smaller when they moved the vertical fin back.
There were minor differences in the Canopy and wind screen. But no external BP glass or Malcom hoods , except for the Q's, bubble canopies.

The landing gear changed a bit in length but from the aerodynamic view the change was from the 75 to 81 when they changed the doors and got rid of the wheel covers on the Hawk 75, which never came back even on the Q's.

Very fighters changed as little aerodynamically as the Hawk series from beginning to end, especially considering the changes in engines. Five different radials (or more depending on how you count the various Cyclone 9s or the early 2 stage R-1830?) two different Allisons (shape not power output) and not counting the Q and the Merlin.

According to some accounts the Qs just cut 1 ft off each wing tip. No change to the leading edge or ailerons. Yes, a lot changed to fuselage.

It does make a good plane for comparing the drag of radials vs V-12 engines as so little was changed. And we have several different V-12s and several different radials to hep average things out. We also have the Hawk 81 P & W Special to help show how radial engine installations progressed.

The Hawk 87s got a little skinner from top to bottom (they didn't have to look over the top of the radial engines anymore) but the Hawk 75 fuselage was pretty skinny side to side even at the beginning. Apparently Berlin/Curtiss didn't subscribe to tear drop school of streamlining.
View attachment 724930

I agree with comparing raidials with inlines, but not so much the drag.

The P-40 airframe was designed for a radial as the P-36 Hawk and, when the inline was fitted, they didn't redesign the fuselage for an optimum fit for the Allison ... they made the engine mount and cowling to fit the existing fuselage that was designed for the radial. So, yes, you can compare the two. But, no, the Allison-powered unit was never designed for the Allison ... it was adapted to fit the originally radial-powered P-36 Hawk.

It is quite possible that had the P-40 been reworked to fit the Allison more optimally, it would have performed better. But I doubt the increase would have amounted to more than 10 - 15 mph even if exactly optimal because the military was running the Allison V-1710 with very conservative MAP numbers. Now, had they optimized the P-40 in a redesign and then used 70" MAP combined with a better propeller, then you might have something on a different level of performance than the basic P-40. It might have been a 400 mph unit.

But that depends on some rather vague optimization. Another "what if" that cannot be adequately explored since it was never built. The P-4Q came closest to this and DID exceed 400 mph in level flight. But it also was made over a year and a half later than when it could have been made. Another case of "too little, too late."

Last, if you have ever taken a close look at a P-40, and I have, it appears it could easily gain some speed by cleaning up the general fit and finish. There are a lot s small, square overlaps than COULD be made into flush-fit skins.

 

[Shortround6]

I agree with comparing raidlas with inlines, but not so much the drag.

I am not saying that they designed the Hawk 75 in 1935-36 for the Allison. However it was better plane to put the Allison in than a P-35/P-43
There are also a bunch of tests on WWII Aircraft Performance that give power used at different speeds for the P-36 and the XP-40 and early P-40s that make comparisons easy. At least for particular points in time.
Changes in air cooled cowl/cooling and changes in liquid cooled cowls and ducts tended to leap frog each other somewhat and certainly did not stay constant for 5-6 years through WW II.

Max fuselage width for a P-40 was under 40in and they achieved that by about the firewall (?) which isn't bad with Cyclone 9 powered Hawk 75s or the Twin Wasp

You could have designed a plane to fit the Allison somewhat better. Like don't put the cockpit on top of the wing (like the Hurricane) with all that space under the cockpit.
!5% wing thickness and 108 in at the wing root. Spitfire was 13% and 100 in cord at the root and the pilots seat was bit further back on the wing (thinner).



But in 1938-40/41 the P-36 vs P-40 comparison was valid and in fact the Ki-61 vs Ki-100 comparison isn't far off.

I have mentioned the fuel and expectations earlier.
IN 1940 the US 100 octane fuel was better than the British 87 octane fuel, but it would not support the boost pressures the British were using with their 100 octane fuel (that whole under 2% aromatics and not less than 20% aromatics thing). Which tends to delay supercharger development in the 1939-40 period. If your supercharger can deliver all (or most of) the boost the fuel will tolerate.

1. why speed time designing a 'better' supercharger'?
2. How do you develop a better supercharger in testing if the limit is the fuel?

In 1940 the British didn't even know what they had exactly and were setting boost limits to use the worst batches of fuel because they couldn't test the fuel and predict how it work.
With later work they found the following formula . Example is comparing 91-96 fuel to 100/130 fuel but 91-96 fuel has a performance number of 88.
36in Hg ans is max boost that can be used on the engine in question (each engine is different) using the 91-96 fuel/PN 88.

[ (36-7) X 130/88] +7 = (29 X 130/88) =7

= 42.8 +7 = 50" Hg abs.

Now is what you have is 100/115 fuel (worst BoB fuel) you adjust your boost setting accordingly. and with testing and learning how to test the fuel raise the boost limits for 100/130 fuel.
For the the US they had to adopt the 20% aromatic fuel mix or they were never going to reach the 120-130 rich mixture number. Now at what point do you start developing engines and superchargers that will operate at even 50in Hg abs. ?

And we have the complication of the heating of the intake mixture by the supercharger. At sea level the supercharger only has to compress the air at a 2 to 1 ratio to hit 60in Hg abs.
At 11,000ft we have to compress the air at a 3 to 1 ratio to hit 60in Hg abs.
At 17,000ft we have to compress the air at a 4 to 1 ratio to hit 60in Hg abs
and so on.
Rounded up a few things to make things a bit easier
A two speed blower in high gear could heat the intake air by over 350 degrees F. (and this may be a late war blower?) And it was this heat combined with the boost level that helped set the actual boost limit.

Once they had the fuel issue straightened out (what they would be suppling and when) you could really work on the superchargers and engines.
For the US the Army had tried to shortcut this process with the turbocharger.
By splitting the work of compressing the air into two stages and using an intercooler they could get sea level performance at 20-25,000ft using the US style 100 octane fuel.
Trouble was the Turbos and intercoolers were large, heavy, and expensive.

the flip side of this was that US wasn't looking at the actual supercharger that closely (Wright and P & W were trying) but since GE had been supplying the supercharger expertise to both Wright and P & W for much of the 30s (and they were not happy) there wasn't much expertise to draw from. GE had their turbos that could supply hundreds of HP to power the compressor so they weren't really looking at the efficiency of the compressor. (power in for amount of compressed air out) and since they were looking at intercoolers the effect of a more efficient compressor (more compressed air for less power means less temperature rise) also was not at the top of the list. They may not have been ignoring it but the list of things to be looked it may not have been at the top.

 

[Wild_Bill_Kelso]

I agree with comparing raidials with inlines, but not so much the drag.

The P-40 airframe was designed for a radial as the P-36 Hawk and, when the inline was fitted, they didn't redesign the fuselage for an optimum fit for the Allison ... they made the engine mount and cowling to fit the existing fuselage that was designed for the radial. So, yes, you can compare the two. But, no, the Allison-powered unit was never designed for the Allison ... it was adapted to fit the originally radial-powered P-36 Hawk.

It is quite possible that had the P-40 been reworked to fit the Allison more optimally, it would have performed better. But I doubt the increase would have amounted to more than 10 - 15 mph even if exactly optimal because the military was running the Allison V-1710 with very conservative MAP numbers. Now, had they optimized the P-40 in a redesign and then used 70" MAP combined with a better propeller, then you might have something on a different level of performance than the basic P-40. It might have been a 400 mph unit.

But that depends on some rather vague optimization. Another "what if" that cannot be adequately explored since it was never built. The P-4Q came closest to this and DID exceed 400 mph in level flight. But it also was made over a year and a half later than when it could have been made. Another case of "too little, too late."

Last, if you have ever taken a close look at a P-40, and I have, it appears it could easily gain some speed by cleaning up the general fit and finish. There are a lot s small, square overlaps than COULD be made into flush-fit skins.

Actually they did put it in a wind tunnel and made a bunch of changes which boiled down to a 30 mph increase in speed over the earliest attempts.

 

[Wild_Bill_Kelso]

(the original conversion of the P-36 to the V-1710 was disappointing until they did this, and I think that included making some changes to the fuselage thickness)

 

[Shortround6]

Note air intake on the top of the cowl near the back of the engine.
The rather sizable radiator hanging out the bottom.
Oil cooler scoop under the nose?
The shrouded exhaust pipes. Air inlet in the front but all six cylinders trying exit out the pipe at the rear.

In the wind tunnel
No propeller blades.
No carb intake.
interim exhausts?
Can't see the radiator.
Oil cooler is larger? or combined with other things?

A truck load of P-40 images on this thread. eBay: Curtiss P-40

Try page 12 for not only a few pictures of the XP-40 but some pictures of the first P-40Q ( standard canopy and full span wings)

 

[SaparotRob]

View attachment 725634
Note air intake on the top of the cowl near the back of the engine.
The rather sizable radiator hanging out the bottom.
Oil cooler scoop under the nose?
The shrouded exhaust pipes. Air inlet in the front but all six cylinders trying exit out the pipe at the rear.

View attachment 725635In the wind tunnel
No propeller blades.
No carb intake.
interim exhausts?
Can't see the radiator.
Oil cooler is larger? or combined with other things?

A truck load of P-40 images on this thread. eBay: Curtiss P-40

Try page 12 for not only a few pictures of the XP-40 but some pictures of the first P-40Q ( standard canopy and full span wings)

It does, however, look really cool.

 

[wrathofatlantis]

The Ki-100 has always baffled me. It is usually reported on with glowing praise, yet on paper, seems to have 1941 era Spitfire Mk.V performance.
From Wiki;
" A well-handled Ki-100 was able to outmanoeuvre any American fighter, including the P-51D Mustangs and Republic P-47N Thunderbolts which escorted the B-29s over Japan, and was comparable in speed, especially at medium altitudes"

" The Ki-100 along with the Army's Nakajima Ki-84 and the Navy's Kawanishi N1K-J were equal to the latest Allied types in the final year of the Pacific War."

Not sure how that would be possible, considering the "latest allied types in the final year of the Pacific war" would be P-47N's, P-51D's, F4U-4 and a smattering of Spitfire MK.XIV's all of which would have enjoyed a 80 mph speed advantage

The reason for the Ki-100's perceived superiority is that turning easily made a mess of hit and run attacks, but the general knowledge of WWII tactics is so poor people just assume hit and run tactics were superior... Hit and run tactics could work, sort of, but required a target that cooperated by going straight, and also firing at point blank range, because the overtaking allowed only a limited firing window. Any shooting from afar would warn the target, which by turning would ruin the approach. Hit and Run ("Dive and zoom") as a superior prop/gun tactic to turning was largely a 1930s assumption.

Turning by contrast did not allow a good aiming lead to a non-turning opponent without this opponent first sharing the circle, and this then also "trapped" the turning opponent in the turn, because rolling out of a turn was usually a bad mistake.

Another myth is that the Imperial Japanese Navy had a strong turning doctrine(!). This has never been true throughout the entire War, Hit and Run being by far preferred by the Navy, with the Zero placing a great emphasis on the Hinero-Komi maneuver, which is a kind of twisted vertical loop.

1975 Saburo Sakai interview: "It was great in dogfights, especially in the vertical. In a vertical looping maneuver like this (looping) the Zero was absolutely wonderful! Even if they got behind you, if you enter a vertical looping contest, in about 3 or 4 loops we'd be right back on their tail. That's how good the Zero was in vertical maneuvers." "We used a diagonal looping maneuver. No two pilots had the same Hinero Komi maneuver."

The Zero not habitually turning in Japanese service (unlike American assumptions based on evaluations of captured examples) is a recent discovery by Intelligence historian Justin Pyke (a specialist in Intelligence archival research), who is interviewed here:


View: https://youtu.be/ApOfbxpL4Dg?si=8unn86EM2X5BSGqy

57:55: Useful intro to the discovery.

1:01:45 (USN pilot, late 1942) "[Japanese Zero] pilots have generally poor fighter tactics. Zeroes could not be shaken by us if they would chop their throttles and sit on our tails. [Meaning turn]"

At 59:07 "Intelligence reports assumed that these tactics indicated the Zero lacked maneuverability."

59:22 "Judging from their apparently long fuselage, these planes do not have a small turning circle, and are not very maneuverable."

59:33 "The Chinese report in question noted the reluctance of the Japanese Navy pilots to dogfight."

1:00:05 "Chinese pilots report that the Japanese will not engage in a turning duel."

1:01:32 "Accounts (from intelligence archives) of Japanese hit and run tactics against the Allies are so numerous, we'd be here for days..."


All this is also borne out by N1K pilot interviews, who used the same tactics all the way to the end. To think Imperial Japanese Navy tactics encouraged turning is to know virtually nothing about the most stalwart "Hit and Run" institution of WWII... German Me-109G pilots were similarly holding on to Hit and Run because of their Eastern Front experience, but finally, way too late, Eastern Front 100 kill aces started to relent by late 1944, as 5 kills Western newbies literally pleaded with them to start turning...:

-"Defenders of the Reich" JG 1 p. 247: Ofhr. Hubert Heckmann (5 kills, survived the War): "I became wingman to the new Kommandeur, Hptm. Karl-Heinz Weber (136 kills). His only experience was from the Eastern Front, and from time to time he used the words "pull up during air combat". I assumed that he would make use of this method in the West, and I warned him about doing so. As his "Kaczmarek", I did not want to lose my "protégé" on his first mission- that would be a bad omen. But he cast all my well-meant recommendations to the wind on our first mission. Weber had a highly polished aircraft [thus emphasizing speed] and whereas we all looked like gray mice, he differed from the rest of the formation. Besides he had Methanol on board [again, emphasis on speed in every option: Me-109G-6AS with MW-50]—7th June Flying at 1000 m. about 30 P-51s showed up some 500 meters above us. After passing us they made a downward turn. Weber didn't turn in, but pulled up steep into the sky, dragging a Methanol cloud behind him. I yelled "turn in!" but he did not listen. I saw 4 P-51s coming down on me, and pulled into a slight left bank [meaning he reduced his turn to entice them to him] to distract them from Weber. My self-sacrifice was of no use; two P-51s stayed behind me, and the other two went after Weber. I fought my two opponents for more than 30 minutes. They moved off when, eventually, they lost much of their speed. That evening we were informed Hptm. Weber (136 kills) was dead." (Killed on his first Western Front mission)

So here you have a relative newbie (with less than 5 kills) desperately trying to protect a 136 kill ace from his mistake of not turning... Interesting...

Concerning the Ki-100 and its turning superiority:

"Aeroplane" November 2005, "Ki-100 fighter Database": p. 61-77 "The conclusion drawn by the Akeno pilots left little to the imagination: In short, it stated that given equally skilled pilots, the Ki-100 (585 km/h) would always win a fight with the Ki-84 (640-660 km/h) in any one-to-one combat. They further added that in a combat situation with up to three Ki-84s, the Ki-100 pilot could still develop the battle to his advantage. The results of the evaluations at the Hitachi school were just as clear-cut: [Captain Yasuro Mazaki] added that the Ki-84 was "only superior to the Ki-100 in diving speed. The Ki-100 was much better in the turn and while climbing." P.77 -The maneuverability of the Ki-100 was the best of the Army's frontline fighters. with the exception of the Ki-43."

Massive Japanese Army pilot preference for the Ki-43 over the Ki-84, simply for basic survival...:

Osprey "Ki-43 aces of WWII" p.50: Sgt. Toshimi Ikezawa, Ki-43 ace: "I heard Major Eto had refused delivery of the Ki-84 (640-660 km/h). They could not avoid an attack if it came from above, because of the Ki-84's poor rate of turn (17-18 s. left, 20-21 s. right). I think we owe our survival to the Ki-43 (540 km/h, 12 s. turn either way), as the Ki-84 would have left you in a tight spot if attacked from above by P-51s. Skilled Spitfire [Mk VIII] pilots would pull out of their dives (!!!) when they realized they could not catch us [unaware]. New [inexperienced] pilots would continue to dive straight down on us, leaving them vulnerable in a turning fight..."

The TAIC captured a Ki-43-II pilot manual and noted: "There is evidence to believe Japanese Army pilots have a strong preference for the Ki-43 over the higher performing Tony and Tojo."

To give perspective, typical P-51B turn times are around the 21-22 seconds mark. Me-109Gs in Soviet tests are 20 left and 21.6 right (above 400 km/h this preference reversed), but I believe they might go one second lower in some hands, or with reduced power. So even the heavy Ki-84 was better in left turns, but similar in right turns to Western types.

Another example of turning's ability to disrup diving attacks:

"Unknown Sword, the battlefield of Army test pilots" p.86-89 and "Aviation decisive battle weapons."(Japanese books): Oblt Losigkeit (German test flying Me-109E-7, in Japan, against Ki-27): "The Ki-27 often turns, so I cannot dive on it."


As to the Ki-84 performance, I think all Army fighter units were ensured 90-92 octane to the end, or at the very least with the Ki-84 units. The Ki-84 did have lemons, but I think the lemons were simply used to upkeep the better ones, and that pilots were not risked on them. The idea of greatly reduced Ki-84 performance because of low quality fuels or maintenance is dubious at best, since pilots were in short supply. Several captured front line pilots reported a top level speed of about 640 km/h (400 mph) at 5 km, which they say they "possibly" (?) could exceed, but never did in practice.

Besides the known Homare problems (it apparently required a full overhaul every time the engine was boosted beyond limits in combat), a more significant issue is that the climb rate performance of the Ki-84 is wildly overstated, as the high power to weight ratio brings on speculations that have no basis in reality. This can quite clearly be seen in the above Ki-100 vs Ki-84 comparison, where it is clear the Ki-84's climb rate is quite modest... I think the cause for Ki-84 climb rate being no better than a FW-190A-8 is the small diameter of its prop (8 inches shorter than the N1K1), which is why the heavier N1K1 climbed significantly better with less power (but probably did not exceed 610 km/h).

This below is from Japanese sources for a Ki-84b (the designations Ki-84-Ia and Ib are Rene Francillon creations, they were Just Ki-84a and Ki-84b in actual Japanese documents), and I believe it is a best case late production value for the speed (659 km/h), and realistic on the climb and ceiling for typical Ki-84as:
Ki 84-Ib: 4x20mm Ho-5 with 120 shells per cannon.
P /L: 4.1 lb /hp; Max speed: 410 mph /20,000'
Initial Climb: 3,787 fpm; Climb to 16,405': 6'54" (this is similar to a FW-190A-8)
W /L: 35.5 lb /sf
Ceiling: 34,449
Normal Range: 1,025

I hope this clarifies a bit what is a series of very confused subjects.

 

[Wild_Bill_Kelso]

Wow... fascinating post

 

[Snautzer01]

mistake of not turning

There was overwheling allied fighter cover on d-day plus. Turning or not with a bunch of brit mustangs behind will make your chanches slim.

 

[Geoffrey Sinclair]

wrathofatlantis, more correct to say hello again Gaston? These turn fighter ideas have been put forward for the last 10 or more years. See for example, Spitfire IX v. FW 190A A thread which does far more than I could pointing out the flaws in the turning fighter ideas, let alone the use of the data.

Another visitation is at http://forum.1cpublishing.eu/archive/index.php/t-15392.html

There are also Britmodeller posts under the new name.

 

[Wild_Bill_Kelso]

Maybe neither emphasis is fully correct, but some of this has the ring of truth to me. It certainly helps explain the success of the Ki-43.

 

[AerialTorpedoDude69]

The reason for the Ki-100's perceived superiority is that turning easily made a mess of hit and run attacks, but the general knowledge of WWII tactics is so poor people just assume hit and run tactics were superior... Hit and run tactics could work, sort of, but required a target that cooperated by going straight, and also firing at point blank range, because the overtaking allowed only a limited firing window. Any shooting from afar would warn the target, which by turning would ruin the approach. Hit and Run ("Dive and zoom") as a superior prop/gun tactic to turning was largely a 1930s assumption.

Turning by contrast did not allow a good aiming lead to a non-turning opponent without this opponent first sharing the circle, and this then also "trapped" the turning opponent in the turn, because rolling out of a turn was usually a bad mistake.

Another myth is that the Imperial Japanese Navy had a strong turning doctrine(!). This has never been true throughout the entire War, Hit and Run being by far preferred by the Navy, with the Zero placing a great emphasis on the Hinero-Komi maneuver, which is a kind of twisted vertical loop.

1975 Saburo Sakai interview: "It was great in dogfights, especially in the vertical. In a vertical looping maneuver like this (looping) the Zero was absolutely wonderful! Even if they got behind you, if you enter a vertical looping contest, in about 3 or 4 loops we'd be right back on their tail. That's how good the Zero was in vertical maneuvers." "We used a diagonal looping maneuver. No two pilots had the same Hinero Komi maneuver."

The Zero not habitually turning in Japanese service (unlike American assumptions based on evaluations of captured examples) is a recent discovery by Intelligence historian Justin Pyke (a specialist in Intelligence archival research), who is interviewed here:


View: https://youtu.be/ApOfbxpL4Dg?si=8unn86EM2X5BSGqy

57:55: Useful intro to the discovery.

1:01:45 (USN pilot, late 1942) "[Japanese Zero] pilots have generally poor fighter tactics. Zeroes could not be shaken by us if they would chop their throttles and sit on our tails. [Meaning turn]"

At 59:07 "Intelligence reports assumed that these tactics indicated the Zero lacked maneuverability."

59:22 "Judging from their apparently long fuselage, these planes do not have a small turning circle, and are not very maneuverable."

59:33 "The Chinese report in question noted the reluctance of the Japanese Navy pilots to dogfight."

1:00:05 "Chinese pilots report that the Japanese will not engage in a turning duel."

1:01:32 "Accounts (from intelligence archives) of Japanese hit and run tactics against the Allies are so numerous, we'd be here for days..."


All this is also borne out by N1K pilot interviews, who used the same tactics all the way to the end. To think Imperial Japanese Navy tactics encouraged turning is to know virtually nothing about the most stalwart "Hit and Run" institution of WWII... German Me-109G pilots were similarly holding on to Hit and Run because of their Eastern Front experience, but finally, way too late, Eastern Front 100 kill aces started to relent by late 1944, as 5 kills Western newbies literally pleaded with them to start turning...:

-"Defenders of the Reich" JG 1 p. 247: Ofhr. Hubert Heckmann (5 kills, survived the War): "I became wingman to the new Kommandeur, Hptm. Karl-Heinz Weber (136 kills). His only experience was from the Eastern Front, and from time to time he used the words "pull up during air combat". I assumed that he would make use of this method in the West, and I warned him about doing so. As his "Kaczmarek", I did not want to lose my "protégé" on his first mission- that would be a bad omen. But he cast all my well-meant recommendations to the wind on our first mission. Weber had a highly polished aircraft [thus emphasizing speed] and whereas we all looked like gray mice, he differed from the rest of the formation. Besides he had Methanol on board [again, emphasis on speed in every option: Me-109G-6AS with MW-50]—7th June Flying at 1000 m. about 30 P-51s showed up some 500 meters above us. After passing us they made a downward turn. Weber didn't turn in, but pulled up steep into the sky, dragging a Methanol cloud behind him. I yelled "turn in!" but he did not listen. I saw 4 P-51s coming down on me, and pulled into a slight left bank [meaning he reduced his turn to entice them to him] to distract them from Weber. My self-sacrifice was of no use; two P-51s stayed behind me, and the other two went after Weber. I fought my two opponents for more than 30 minutes. They moved off when, eventually, they lost much of their speed. That evening we were informed Hptm. Weber (136 kills) was dead." (Killed on his first Western Front mission)

So here you have a relative newbie (with less than 5 kills) desperately trying to protect a 136 kill ace from his mistake of not turning... Interesting...

Concerning the Ki-100 and its turning superiority:

"Aeroplane" November 2005, "Ki-100 fighter Database": p. 61-77 "The conclusion drawn by the Akeno pilots left little to the imagination: In short, it stated that given equally skilled pilots, the Ki-100 (585 km/h) would always win a fight with the Ki-84 (640-660 km/h) in any one-to-one combat. They further added that in a combat situation with up to three Ki-84s, the Ki-100 pilot could still develop the battle to his advantage. The results of the evaluations at the Hitachi school were just as clear-cut: [Captain Yasuro Mazaki] added that the Ki-84 was "only superior to the Ki-100 in diving speed. The Ki-100 was much better in the turn and while climbing." P.77 -The maneuverability of the Ki-100 was the best of the Army's frontline fighters. with the exception of the Ki-43."

Massive Japanese Army pilot preference for the Ki-43 over the Ki-84, simply for basic survival...:

Osprey "Ki-43 aces of WWII" p.50: Sgt. Toshimi Ikezawa, Ki-43 ace: "I heard Major Eto had refused delivery of the Ki-84 (640-660 km/h). They could not avoid an attack if it came from above, because of the Ki-84's poor rate of turn (17-18 s. left, 20-21 s. right). I think we owe our survival to the Ki-43 (540 km/h, 12 s. turn either way), as the Ki-84 would have left you in a tight spot if attacked from above by P-51s. Skilled Spitfire [Mk VIII] pilots would pull out of their dives (!!!) when they realized they could not catch us [unaware]. New [inexperienced] pilots would continue to dive straight down on us, leaving them vulnerable in a turning fight..."

The TAIC captured a Ki-43-II pilot manual and noted: "There is evidence to believe Japanese Army pilots have a strong preference for the Ki-43 over the higher performing Tony and Tojo."

To give perspective, typical P-51B turn times are around the 21-22 seconds mark. Me-109Gs in Soviet tests are 20 left and 21.6 right (above 400 km/h this preference reversed), but I believe they might go one second lower in some hands, or with reduced power. So even the heavy Ki-84 was better in left turns, but similar in right turns to Western types.

Another example of turning's ability to disrup diving attacks:

"Unknown Sword, the battlefield of Army test pilots" p.86-89 and "Aviation decisive battle weapons."(Japanese books): Oblt Losigkeit (German test flying Me-109E-7, in Japan, against Ki-27): "The Ki-27 often turns, so I cannot dive on it."


As to the Ki-84 performance, I think all Army fighter units were ensured 90-92 octane to the end, or at the very least with the Ki-84 units. The Ki-84 did have lemons, but I think the lemons were simply used to upkeep the better ones, and that pilots were not risked on them. The idea of greatly reduced Ki-84 performance because of low quality fuels or maintenance is dubious at best, since pilots were in short supply. Several captured front line pilots reported a top level speed of about 640 km/h (400 mph) at 5 km, which they say they "possibly" (?) could exceed, but never did in practice.

Besides the known Homare problems (it apparently required a full overhaul every time the engine was boosted beyond limits in combat), a more significant issue is that the climb rate performance of the Ki-84 is wildly overstated, as the high power to weight ratio brings on speculations that have no basis in reality. This can quite clearly be seen in the above Ki-100 vs Ki-84 comparison, where it is clear the Ki-84's climb rate is quite modest... I think the cause for Ki-84 climb rate being no better than a FW-190A-8 is the small diameter of its prop (8 inches shorter than the N1K1), which is why the heavier N1K1 climbed significantly better with less power (but probably did not exceed 610 km/h).

This below is from Japanese sources for a Ki-84b (the designations Ki-84-Ia and Ib are Rene Francillon creations, they were Just Ki-84a and Ki-84b in actual Japanese documents), and I believe it is a best case late production value for the speed (659 km/h), and realistic on the climb and ceiling for typical Ki-84as:
Ki 84-Ib: 4x20mm Ho-5 with 120 shells per cannon.
P /L: 4.1 lb /hp; Max speed: 410 mph /20,000'
Initial Climb: 3,787 fpm; Climb to 16,405': 6'54" (this is similar to a FW-190A-8)
W /L: 35.5 lb /sf
Ceiling: 34,449
Normal Range: 1,025

I hope this clarifies a bit what is a series of very confused subjects.

Thank you for providing such an excellent overview of Japanese aircraft performance and maneuverability. The sources that you've rounded up are both high quality and compelling in their presentation of data.

Regarding the Frank's Ko (A) and Otsu (B) classifications (which were loadouts and not engine differences IIRC), I believe you are referring to Francillon's data where he wrote that the Ki-84-II had a 416 MPH top speed. But he clearly indicates in the text (as well as other texts) that this is with either a Homare 23 or Homare 25 engine and not with the model 21. I think he made this point to show that there were substantial performances differences based on the engine. It's also clear from having read many of his books that he never understood that the Japanese recorded top speed differently than the Allies did. This is something that postwar scholarship has only recently discovered.

One thing that I love about the video you've provided is that its sources reconcile the discrepancies between TAIC and Japanese sources for top speed. So if the reported "overboost" of an A6M2 is 4% higher than its military speed, we can add 4% to Japanese-derived top speed values to arrive at a reasonable estimate for WEP performance.

This would suggest that the Frank II (or more accurately, late model Frank) had a top speed of around 433 MPH with 92 octane fuel (1.04 x 416 MPH = ~433 MPH). However, Francillon's book seems to show no other performance data for the late-model Frank and it may be that this was provided anecdotally, which would cast a shadow of doubt over the precision of that number.

Regarding your analysis of the Ki-84, you are almost certainly correct about its prop sucking. I would add that many other aircraft had superior performance with smaller or similar sized props based on better aerodynamic design and better pitch angles. But these post-war designs had one thing that the Ki-84 didn't have: better electrical systems. The low-voltage Ki-84 electrical system couldn't accommodate better pitch angles and as far as I can tell, unless the voltage system improved on late-series production, the prop couldn't be used to its fullest potential. We've discussed it here, but the La-9 had a three-bladed prop and an 1,850 HP engine.

 

[Wild_Bill_Kelso]

Revisionist theories notwithstanding, I'm just very pleased to see a deeper dive into the Japanese aircraft. Everything I'd been able to find on them is so superficial. There is almost nothing on WW2aircraftperformance (unlike for most British and American types)