Author Topic: Ki-84.........420 MPH??? (Read 2185 times)

brady · « **on:** June 10, 2004, 10:23:32 AM »

From another forum posted by Mike, does anyone care to comment on his findings:

........................

U.S. Far East Command. Mil Intell Sec. "Interrogations of Japanese Officials (English translations)." 2 vols. Typescripts, various dates. D811A2I3713.

_____. "Statements of Japanese Officials on World War II (English Translations)." 4 vols.
Typescripts, various dates. D811A2S7313.

Much of the rest of my research is Rene Francillon's work.
I believe that Gary uses Gustin as a source as the numbers seem to match.
Gustin actually does good research and provides much interesting info about aircraft but his summaries at the end of a section will usually just have one model listed. The problem is that he often does not list what model he is refrencing!

For example Gustin lists the Ki-84 as having a top speed of 392mph. That is it. One model.

Francillon on the other hand says the first prototype in November 1942 flew at 388mph, the fourth prototype flew at 392mph, and the pre-production arcraft added seperate exhaust stacks which gave another 9-10mph.

The problem with the speed for the actual production model is that the number did not seem to survive the war. No one has found a clear refrence.
However, I was able to put some info together. The most common engine in the Ki-84-1 was the type 21 engine. The engine chosen for the Ki-84-2 (part wooden) was also the type 21. The German & Japanese designers both stated numerous times during the war that making an aircraft part wooden would lose you 5-6mph. The Ki-84-2 flew at a speed of 415mph with a combat load. The engine on the pre-production Ki-84 developed 1800hp while the main production engine developed 1990hp on the same weight.

So, since the speed of the Ki-84-2 is a known value, and the engines were the same, i would guess the speed for the main production Ki-84-1 was about 420mph.
I would be willing to be talked down to 415mph for general lack of quality control.

However, that is a seperate issue in many ways as it ASSUMES that Japan is being bombed and that i have overdrafted my population. What idiot drafts his tool & die makers and heat treaters?
Well, Tojo. Moron. I probably will not.
I would be willing to make a change in my scenario that in return for my aircraft numbers i will slightly lower Japanese manpower.

Anyway, NARA is a great source for almost anything related to the war. especially since Clinton (who actually believed in Democracy) declassified virtually everything related to the -TINTS reports.

Mike

Karnak · « **Reply #1 on:** June 11, 2004, 01:28:13 AM »

Interesting.

I hope (kinda, thinking of my poor Mossie) you can get some more data.

moot · « **Reply #2 on:** June 11, 2004, 02:40:06 AM »

will be punting this one

Mitsu · « **Reply #3 on:** June 11, 2004, 06:17:17 AM »

If the engine could put out 2000HP.....

SunTracker · « **Reply #4 on:** June 11, 2004, 07:47:06 AM »

What octane fuel was the 415mph achieved at?

Also, didnt the U.S. test Ki-84s with 150 octane fuel at the end of the war?

Shuckins · « **Reply #5 on:** June 11, 2004, 07:55:01 AM »

My memory may be playing tricks on me here, but I don't believe Japanese aviation fuel ever had an octane rating greater than 100, if it was THAT good.

Poor quality control exacted a bigger penalty in performance from the Ki-84 than many would admit. Top speeds for those aircraft that were actually flown in combat were considerably less than the 420mph quoted above. Late-war Japanese aircraft engines were notoriously unreliable and produced less power than the designers had intended.

On the other hand, a captured Ki-84 was brought to the U.S. and meticulously restored by the Army Air Corps. With high-octane American aviation fuel and a superbly tuned engine that Ki-84 did, indeed, approach that performance figure.

Regards, Shuckins/Leggern

brady · « **Reply #6 on:** June 11, 2004, 10:01:53 AM »

This guy I quoted above, says that the higher octane fuel would not of increased the Ki-84 preformance, since it was designed to operate on lower (well 87) Octane fuel. He also says that the test was run using 87 octaine fuel for the Ki-84. I will link the thread hear so you can read it in detail it is very interesting and their are more figures and referances:

A quote from the thread linked below:

"Just for reference about aviation gas, during WWII the US used 3 grades and they were classified as 80/87, 100/130, and 115/145. I'm also pretty sure that high performance American fighters only used the 115/145 grade. Also my 1972 Sanderson 'Private Pilot Manual' says it is ok to use a higher grade of the gasoline than your engine is rated for if your grade isn't available for a short period of time but it will not improve performance. "

See this thread all te good stuff is buried in the middle of it:

http://www.matrixgames.com/default.asp?URL=http%3A//www.matrixgames.com/forums/

moot · « **Reply #7 on:** June 15, 2004, 02:24:37 PM »

Vermillion · « **Reply #8 on:** June 17, 2004, 12:28:57 PM »

The test was performed with 100 octane fuel. In a war condition (no ammo, but with guns) aircraft that was reconditioned here in the US.

I have several magazine articles from the 70's that talk about this in depth. However, there is no known records from the flight tests, and I've checked with the Air Force Musuem on the issue.

FDutchmn · « **Reply #9 on:** June 17, 2004, 05:12:42 PM »

Quote

Originally posted by brady
This guy I quoted above, says that the higher octane fuel would not of increased the Ki-84 preformance, since it was designed to operate on lower (well 87) Octane fuel.

This didn't occur to me... sounds logical in a way but kinda contradicts what I read about Japanese pilots account of flying the N1K2s right after the war. They were ordered by the GHQ to fly the fighters to the location where they were impounded... on American fuel. They noted quite a difference...

On the other hand, I remember in the modelling of AirWarrior, the Bf109 did not take a knock down in performance when the fuel was hit on a base (fuel hit on a base was to lower octane on AW). The reason for that modelling was that the Bf109s were designed to operate at lower octanes. Is that true? This doesn't seem to match things talked about here or we just can't generalize things?

gripen · « **Reply #10 on:** June 17, 2004, 06:02:51 PM »

My impression is that in the Wright field tests of the Ki-84 they used higher octane fuel to substitute water injection. Only way to check this out is to find a report which contains used MAP values. Anyway, it's very unlikely that the USAAF used somekind of higher ratings than were used by the Japananese with water injection.

gripen

BUG_EAF322 · « **Reply #11 on:** June 17, 2004, 06:04:48 PM »

401mph

otherwise perk it

Karnak · « **Reply #12 on:** June 17, 2004, 07:49:23 PM »

Quote

Originally posted by Vermillion
The test was performed with 100 octane fuel. In a war condition (no ammo, but with guns) aircraft that was reconditioned here in the US.

I have several magazine articles from the 70's that talk about this in depth. However, there is no known records from the flight tests, and I've checked with the Air Force Musuem on the issue.

It seems that the Ki-84-II Japanese performance tests do exist, if brady is correct. Why would the Ki-84-II test out at 415mph on Japanese fuel when using the same engine but the Ki-84-I only 392mph? It seems likely,if the Ki-84-II data is real, that a common Ki-84-I in good working order would do 415-420mph.

FDutchmn · « **Reply #13 on:** June 17, 2004, 11:09:17 PM »

Mitsu... any comment?

gonna go to the public library over the weekend...

-ammo- · « **Reply #14 on:** June 17, 2004, 11:34:05 PM »

I cant see HTC modeling that AC with anything other than published top speeds..which is 392 MPH TAS. They didn't model anything else that way, with the eception of the G-10. However, it always good to dream.