Quest for the 427mph Ki-84 Continues......

[Vermillion]

As most of you know, one of my "quests" is to find more information on the 1946 post war test in the US where a Ki-84 Frank achieved 427mph maximum speed, as reported in Francillons book "Japanese Aircraft of the Pacific War".

So a couple of weeks ago, I posted over on the Warbirds Worldwide BBS, on this and asked if anyone knew of more information.

A gentleman responded that he had some old magazine articles on this particular aircraft, and what happened too it. So he offered the magazines up for sale on E-Bay and I bought them for $10. What a deal !  

Air Combat, Vol. 1 No. 1 (original edition) Winter 1973. Article: "The Ki-84 Hayate"

Air Classics Vol. 13 No. 10, October 1977. Article: "Japans Last Samurai, The Only Flying Japanese Warbird."

Both articles confirm the information in Francillons book, and also mirror one another. Here are the highlights:

The tests were conducted at Middletown Air Depot (PA), and at Wright Field. (1946) On captured Japanese war stock, brought over on the escort carriers CVE-13 USS Core and CVE-20 USS Barnes.

"Four Hayates are assumed to have been included  in the total bourght back, althought only two were given technical evaluations numbers, T-301 and 302.  Two were destroyed immediately, the rationale being that they were merely scaled up Zero-Sens, a third disappeared sometime after 1949, and the fourth suddenly appeared in the early 1960's in the hands of Ed Maloney's Claremont Air Musuem."

"...its all out speed proved amazing, 427 mph at 20,000 ft as compared to 405 for the Thunderbolt and 424 for the Mustang".

"In 1963 the plane .... where it was completely restored by Garret AiResearch and put into airworthy condition... and registered with the license N3385G... "

Eventually in 1973, the aircraft was sold to an Japanese industrialist for $100,000, restored once more, flown once, and placed in a musuem where it sits today. The last known Ki-84 on Earth.

Hmmm... Does Maloney's Museum still exist? And if so, I wonder if they would have kept any documents on the aircraft or tests.



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Vermillion
**MOL**, Men of Leisure
Carpe Jugulum
"Real Men fly Radials, Nancy Boys fly Spitfires"

[funked]

Oh, come on <saracasm> Don't you know all Axis aircraft tested by the US were clapped-out beaters that were intentionally derated for propaganda reasons? </sarcasm>

[Citabria]

The data I found for the actual Ki-84-1a *used* by the Japanese during the war:

325mph at sea level
392mph at 20,080ft
service ceiling 34,450ft

the 1a, 1b and 1c differed only in armament,
1a: 2 13mm, 2 20 mm
1b: 4 20mm
1c: 2 20mm and 2 30mm! (buff buster?)

[Vermillion]

Thats pretty typical Citabria of the numbers you see for the Ki-84 in most references, but occaisonally you see the 427 mph number crop up.

FYI the Ki-84 I am talking about was a plane *used* in the war   Straight off a CVE that brought it from the Pacific. This plane was not a stripped down civilian sport version.

One major difference in the US Test and the Japanese Tests that are the source of numbers in the 380-390 range.

The 1946 US Test used standard 100 octane avgas.

The Japanese tests were using war time 85 octane avgas with a pine oil additive.

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Vermillion
**MOL**, Men of Leisure
Carpe Jugulum
"Real Men fly Radials, Nancy Boys fly Spitfires"

[Citabria]

I understand that,

I just think that in the spirit of things I would rather have the plane perform the way it did for the japanese aces who flew it in combat rather than the aircraft that in 1946 with 100LL avgas was so fast it blew its own paint off  

[Vermillion]

So to paraphrase your statement   You want the plane to fly just like it did for the Japanese Aces (read 18 year old with 20 flight hours) so that you can kill it easier in your P-38?  

Just kidding.  I know what you mean. I am more interested in the test data from the point of view of engineering and aviation history.


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Vermillion
**MOL**, Men of Leisure
Carpe Jugulum
"Real Men fly Radials, Nancy Boys fly Spitfires"

[Kieren]

I have a copy of the Aero series K-84, and it does quote 427mph.

[sr2053]

So u need 2 fuel tanks on airfield one with 85 octanes and second 100 octanes. Wny u just cant put 100 octanes in your japanise plane?  

[Kieren]

Actually I am interested in an engineer's viewpoint. Wells, funked, what are the possibilities the Ki-84 could have broken 400mph on the available horsepower? Being sized comparably to Allied aircraft of the time, seems to me the poor altitude performance for the engine would prevent it from reaching the thinner air with enough power to pull it that fast. Am I close?

[funked]

I think it all comes down to engine performance.

Up to 2000 hp was claimed for the Homare, but manufacturing variation was so large that many Ki-84's were no faster than Ki-44's.

Obviously running on gasoline instead of pine scented air freshener will help you make the rated power.  

[wells]

If the engine did in fact produce it's rated power (1990, 2000, whatever), there's no doubt in my mind that it could achieve 425 mph, with the George even breaking the 400 mark, but alas, I fear this was not the case (at least in Japanese hands) and the engine did not produce what it was designed for.

[Kieren]

And there is the dilemma for the HTC gang; do you go by the numbers, or do you use anecdotal data to arrive at a more logical representation of the real plane?

As all the real life foibles of all aircraft are not modeled, it seems the slide rule approach is most consistant- unless one wants to "fudge" the horsepower a bit to arrive at a more realistic power output. Didn't the Homare in the George realistically come out more like 1,700 hp, far below its rated power?

[SnakeEyes]

Which test data should a flight model be based on?

1) Consistency/Fairness - If particularly the Allied numbers correspond to prototypes, then for the sake of consistency/fairness, you have to give serious consideration to doing this for all aircraft.

2) Play balance - You can argue about it all you want, but if the prototype specs for a given aircraft would make it overwhelmingly better than the majority of its counterparts... well... this would have to be seriously considered as well. Would you rather have the production model, or no model at all?

3) Historical impact - Which numbers best enable the aircraft to simulate the historical impact which it had during the war (in terms of air combat, not winning and/or losing the war).

This is best illustrated by an example: The Ki84 was tested after the war using 100 octane gas which the Japanese had little access to during the war. As a result, its performance was astoundingly better than the Japanese manufacturer's statistics. Combined with the fact that none of the flight sim manufacturers are going to simulate random engine fires, a Ki84 based on the American test data would not accurately represent the Ki84 that the US encountered in the Pacific (the same would probably be true for the George also). And that has a domino effect on other historical aspects we can only guess at... had the George and Frank had access to high quality gas, you can bet that planes like the F4U-4, P-51H, and F8F would have reached the PTO much sooner in response. In short, if you choose data which over- (or under-) represents the performance of the Real Life aircraft vis-a-vis its peers, that can cause huge problems.

4) Resources and future game growth - Can HTC (or any other sim manufacturer) afford to model both versions? Again, while it has the cost of the company spending the time to model the additional "variant" and create features that enable these variant models to be turned "on" or "off" (for scenario use, for example), the benefit is flexibility and a wider range of "options" for the user base (not to mention if HTC gets into doing Scenarios).

Again, no value judgement on any particular aircraft here... just my thoughts on the various decision-making factors involved (as I see them).

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SnakeEyes
o-o-o-
=4th Fighter Group=

[wells]

Part of another problem that I see with the numbers is that almost every source quotes 2000 hp for the engine, but then also quotes the lower top speed along with it, which is probably misleading.  If a plane were modelled that way, the drag coefficient may be artificially higher, affecting both turn and climb performance.

I agree that the plane should be modelled as it was for the most part.  After all, fuel is a weapon every bit as much as the guns.  If you give a Ki-84 100 octane fuel where it didn't use it, then you might as well give it 6 cannons or something silly like that...same thing to me.  On the other hand, part of a good game, IMO, is the fantasy of it...the ability to perhaps change the course of the war.  It would be neat if somehow through some strategic element, the quality of the fuel (say along with the quantity as it is currently) could be altered, allowing aircraft to either perform better or worse than they did historically.

Imagine a Ki-84 or a F4u-4 with 115/140 grade fuel!!

[This message has been edited by wells (edited 05-06-2000).]

[Vermillion]

And Guys, please don't think I am lobbying for the 427 mph variant of the Ki-84 here.

I guess it intrests me because it goes against the "American Planes are always faster, and the Japanese could only build slow turn fighters." fallacy.

But hey maybe some day we could get Pyro to build us a Ki-84Ic that can do the 427 for a "evil con" missions some time  

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Vermillion
**MOL**, Men of Leisure
Carpe Jugulum
"Real Men fly Radials, Nancy Boys fly Spitfires"