Ki-84 - uber aircraft?

[Tony Williams]

Originally Posted by Sgt. Pappy

True, Williams. But this cannot be said for all engines. The Merlin 66 at one point ran on 100 grade UK Octane (100/125 US grade I think?). With almost no modification to the engine took on 150 UK grade (115/145 US grade) and look at the huge performance boost it got at low-med alts just from that octane grade.

It seems that some octane grades differ enough to boost performance.

The "almost no modification" consisted of changes to the supercharging in order to increase the boost pressure quite considerably, and that's what increased the performance - which is the point I made.

I have in front of me "The Merlin in Perspective", an official publication of the Rolls-Royce Heritage Trust. This includes the following information:

The Merlin was first developed on 87 octane fuel, at which the maximum permissible boost pressure was +6 psi. Changing to 100 octane immediately enabled the pressure to be increased to +12 psi, which increased the power from just over 1,000 to 1,300 hp.

Further development (particularly a two-stage supercharger, together with modifying the constituents of the fuel to better suit the engine) enabled the boost pressure to be increased to +18 psi, increasing the power to 1,600 hp.

The final development came with 150 octane fuel in 1944, which enabled the boost pressure to be raised to +25 psi and the power to over 2,000 hp.

Through all of the above, the Merlin stayed basically the same (apart from durability/longevity improvements); the increasing performance was entirely down to increasing supercharger boost pressures, which was only made possible by using improved fuels.

[Sgt. Pappy]

Ah yes. I have borrowed that book and I really want to get myself a copy.

That's interesting. The 150 grade, though, doesn't seem to need modification to the supercharger. I'm still bad with my terminologies but I'm reading off of Spitfire IX Trials at +25 boost
I could be wrong, but I just haven't found any modification pertaining to the supercharger or other parts to allow the use of 150 grade.

The other grades, yes but not 150.

[merlin]

Fellow 'posters' may be interested in the introductions to the Nakajima Ki-84 Hayate.

First from Francillon:

The Nakajima Ki-84 Hayate, undoubtedly the best Japanese fighter aircraft to see large-scale operation during the last year of the war, was as feared by Allied crews as it was praised by Japanese pilots. Well protected, well armed, fast and manoeuvrable, this fighter gave a good account of itself in the desperate battles over the Phillipines, the Ryukyu Islands and the Japanese Home islands, and Japan's faith in it is emphasized by the fact that at the end of the war they were building inderground factories with a planned rate of 200 Hayates per month.

Second from Wllm Green:

During the summer of 1944 the J.A.A.F. introduced a new warplane, the Ki-84-1a or Type 4 Fighter, Model 1a, which was destined to become for the Allies the most troublesome Army fighter encountered in combat from that time until the end of the war. Employed in all operational theatres, and used for high-, medium-, and low-altitude interception, close-support and dive-bombing, the Hayate differed radically from earlier J.A.A.F. fighters, in that relatively light construction gave place to an extremely sturdy structure. It compared favourably with the best of its antagonists; it was slightly slower than the P-51H Mustang and the P-47N Thunderbolt, but it could out-climb and out-manoeovre both American fighters.

For such good write-ups, the designers must have done something right. It was not the aircraft's fault if, at times poor workmanship or maintenance gave it problems at crucial times.

[JoeB]

Originally Posted by merlin

Fellow 'posters' may be interested in the introductions to the Nakajima Ki-84 Hayate.

First from Francillon:

The Nakajima Ki-84 Hayate, undoubtedly the best Japanese fighter aircraft to see large-scale operation during the last year of the war, was as feared by Allied crews as it was praised by Japanese pilots.
Second from Wllm Green:

During the summer of 1944 the J.A.A.F. introduced a new warplane, the Ki-84-1a or Type 4 Fighter, Model 1a, which was destined to become for the Allies the most troublesome Army fighter encountered in combat from that time until the end of the war.
For such good write-ups, the designers must have done something right. .

This is apropo to the recent off topic tangent on another thread about aviation authors. It particularly mentioned criticism of Green, who I defended as a good basic source but outdated. Francillon wasn't mentioned but has also written a lot of accurate, and some pretty inaccurate, things over his long career.

See my post on the first page (and the link to excellent earlier thread on this forum about Type 4 ops in China). I don't know of any two side documented combats where Type 4's were so successful as to be 'feared' or even very 'troublesome'. A potentially good plane yes, but actually successful or 'feared' in the circumstances pertaining, much more doubtful, at least as far as fighter v fighter combat.

As a kid I read Green's series when it was pretty new, and I still refer to Francillon's 'Japanese A/c...' all the time (though with due caution, not just about those kind of generalizations, but which units operated planes, how many produced, etc. there are apparently a fair number of errors in that info). Once upon a time I would assume the kind of general characterizations in those books were backed up with a lot of well documented examples of particular combats, but now I realize that's a doubtful assumption.

Joe

[renrich]

Merlin, I would be extremely surprised if the KI 84 could out climb a P51 H although I don't know if they ever encountered one another. A fighter the KI 84 probably did encounter which it would not have had many if any advantages over would have been the F4U4.

[attack!!!]

I think the best Japanese fighter aircraft is the Kawanishi N1K-J Shiden Kai:

In air-to-air combat, experienced Japanese pilots flying Shiden Kais could more than hold their own against most American pilots flying F6F Hellcats. In February 1945, a brave pilot, Warrant Officer Muto, single-handedly engaged 12 Hellcats and shot down four of them before the remainder disengaged

Is this story true?

[renrich]

If you are referring to the Shinden, a canard AC, my source says that it had a total flying time of 45 minutes before the war ended so I doubt if it had any kills.

[Sgt. Pappy]

He's referring to the Kawanishi N1K2-J Shiden Kai "George".
Kawanishi N1K1-J Shiden (Violet Lightning) and N1K2-J Shiden Kai

It's a conventional monoplane .. not like the Shinden.

[merlin]

No attack!! is not refering to the Shinden, the reference 'Shiden' is correct the Allied code name being 'George'.
As soon as the prototype of the floatplane fighter 15-shi Kyofu (Mighty Wind) flew, work began on a land-based version. The first version had almost mid-fuselage set wings - which meant low undercarriage.
This to quote Green:
.... entered service with the J.N.A.F. early in 1944, and despite troubles with its Homare engine and shortcomings resulting from the inadequate development period, it soon proved itself a redoutable warplane, and its pilots came to lool upon the formidable Gruman Hellcat as a relatively easy 'kill'.
The second version the Kawanishi N1K2-J Shiden-Kai (George 21) was a simplified aircraft - only 43,000 parts compared with 66,000 on the first, it was now a low-set wing yielding a less complicated undercarriage.
It was this machine that Flight Warrant Officer Kinsuke Muto is quoted by Green as having his 'success' - what a competent pilot can do.

[JoeB]

Originally Posted by attack!!!

'a brave pilot, Warrant Officer Muto, single-handedly engaged 12 Hellcats and shot down four of them before the remainder disengaged'
Is this story true?

No, and it's not even a claim actually made by Muto. It was invented in a war time Japanese press release, then repeated by writers like Green and Francillon and ever since.

Again see my earlier post mentioning "Genda's Blade" about the 343rd Air Group. The author, Henry Sakaida, estimated from correlating their and US accounts of their various combats that this elite Shiden ('George') unit's actual exchange ratio v US fighters (it met USAAF, USN and USMC) was around 1:3, ie. in the US favor; although it did have some successful combats. I recommend that book, and as I mentioned regret there isn't so far anything similar dealing comprehensively with a Type 4 ('Frank') unit's actual results, even in Japanese AFAIK.

Like the Type 4, the Shiden* was inherently a good plane, but its combat record in the actual cirsumstances, as far as can be verified from two sided accounting, was not all that impressive.

*紫電 shiden=violet [colored] lightning v 震電 shinden=tremor causing lightning (or 'magnificent' lightning as often rendered).

Joe

[renrich]

I strongly question that any Japanese pilot ever looked on a Hellcat as an easy kill. At least Saburo Sakai did not indicate that although he did score some kills against that AC, although I don't believe it was in a George. My source shows the George as having performance about like an F6F3 but not up to the Level of the F6F5.

[JoeB]

Originally Posted by merlin

This to quote Green:
.... it soon proved itself a redoutable warplane, and its pilots came to lool upon the formidable Gruman Hellcat as a relatively easy 'kill'.

I didn't notice the quotation of that classic chestnut before. There's simply no evidence to support that statement, AFAIK no evidence Green even thought he had any particular evidence . Let me ask again more directly, why exactly *are* we quoting Green at this stage of the game?

Joe

[Graeme]

Originally Posted by JoeB

Once upon a time I would assume the kind of general characterizations in those books were backed up with a lot of well documented examples of particular combats, but now I realize that's a doubtful assumption.

You discussed a number of authors in another thread Joe and now Francillion joins the list?

Originally Posted by merlin

It compared favourably with the best of its antagonists; it was slightly slower than the P-51H Mustang and the P-47N Thunderbolt, but it could out-climb and out-manoeovre both American fighters.

This is also mentioned in Francillion's biblical "Japanese Aircraft of the Pacific War" of 1970. He mentions the Ki-84 reaching;

"427mph at 20,000 ft using War Emergency Power. This speed exceeded that of the American P-51D-25-NA Mustang and Republic P-47D-35-RA Thunderbolt at the same altitude by 3 mph and 22 mph respectively."

Joe has mentioned that Francillion provides no evidence where this comparison data came from.

Interestingly he wrote an article for the part-work series Airplane in 1990 and makes no mention of the above comparison, simply concluding that a Ki-84 was;

.."extensively tested in the Philippines and the United States, this evaluation confirming the high opinion in which the Hayate was held by allied crews."

[JoeB]

Originally Posted by Graeme

You discussed a number of authors in another thread Joe and now Francillion joins the list?

...Francillion's biblical "Japanese Aircraft of the Pacific War" of 1970. He mentions the Ki-84 reaching;

Yes, "Japanese a/c..." is an important book but you can't rely on it entirely, not for those sort of unfootnoted characterizations, and also not for the order of battle info (which units operated which planes at the end of each section), or necessarily the production histories, etc. Though there isn't any one English language book that covers the whole topic better that I know of.

Francillon way back also wrote stuff on the Pacific War apparently using popularized Japanese publications as source. I remember one article, though can't remember the exact citation, reciting vastly inflated Japanese aerial claims at Coral Sea as if facts. Now as we all know, older Western work usually did the inverse, some lower quality stuff still does, repeating Allied claims clearly not verified as losses in long known and credible Japanese sources. But it's something to keep in mind, that Francillon's original approach to this topic seems to have been via popularized Japanese accounts and that's where some of those statements probably come from. Anyway again, with 'Hellcat easy kill', whether it's from Green or Francillon, and while it may have appeared first in some Japanese article or book, it's highly questionable whether that was actually the view of Japanese air units, and it clearly can't be supported with two sided facts of F6F v Shiden combats; likewise the 1 George v 12 F6F's comes out 4:1 in favor of George, was a Japanese wartime press claim, not an actual JNAF claim, besides not being true.

Joe

[Sgt. Pappy]

What is really needed is hardcore test data... the aircraft's condition, loading etc. Hard to find especially on Japanese planes.