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.