Ki84

[Krusty]

I don't think you understand the original request.   


I agree with Eagle in that there's no need for this. On full internal fuel you can take 2 bombs halfway across a map and back. It's not like you're flying across the PTO and need all the gas you can for a 1000000-mile mission or anything. IMO it brings no new functionality to the game. I personally don't take the 1 bomb 1 DT loadout on corsairs or p38s all that much either.

[EagleDNY]

You are incorrect in regards to the lighter, more powerful version. The later engines could not be run at any higher a power rating than the engines they replaced. They were derated and ran at lower power levels. The quality of production as well as the quality of the gas and lubricants available meant that the Ki-84-IIs had no more power than the model they were supposed to replace.

Fortunately for us late-war ridin' IJN pilots, AH does not model poor fuel and lubricant quality, or the effect of lack of spare parts, poor maintenance, or generally poor reliability in design. 

That said, I was interested by the postwar testing of the Ki-84 with a model 21 engine at Wright Field.  Found this set of specs on it:

Wright Field Interim Report No. F-1IM-1119B-ND released January 1947 of a Ha.45 Model 21 engine equipped Frank 1, Serial No. 302:

Speed

Normal fighter Military Power

At sea level 350 mph ( 563 km/h )
At 10,000 ft 389 mph ( 626 km/h )
At 20,000 ft 412 mph ( 663 km/h )
At 23,000 ft 426 mph ( 686 km/h )
At 30,000 ft 400 mph ( 644 km/h )
At 35,000 ft 370 mph ( 596 km/h )

Climb Normal fighter

Time to 10,000 ft 2.6 min
Time to 20,000 ft 5.8 min
Time to 30,000 ft 10.0 min

at S.L. Military Power 3790 ft/min
at Military Power 20,900 ft 3195 ft/mi
at 17,900 ft W.E.P. 3615ft/min

Service Ceiling 38,800 ft   

This stuff is on Richard Dunn's site, and notes the tests were done with American fuel, which had to be a lot better than the stuff they were getting in the field.  I don't remember ever reading what grades of AvGas the IJN specified though. 

[Karnak]

Actually, it does model the poor fuel.  That is why the Japanese aircraft don't break 400mph even with their 1900+hp engines.

[Krusty]

Precisely. The engines were DERATED, not just on a whim. They were only allowed to run at such-and-such settings, providing so-much power.

In the end they were running the exact same power as the predecessors they were supposed to surpass. It just didn't happen the way the Japanese wanted.

[nrshida]

You are incorrect in regards to the lighter, more powerful version. The later engines could not be run at any higher a power rating than the engines they replaced. They were derated and ran at lower power levels. The quality of production as well as the quality of the gas and lubricants available meant that the Ki-84-IIs had no more power than the model they were supposed to replace.

Once again Krusty, your ignorance is only surpassed by the smugness of your presentation. When we debated this subject approximately six months ago, you were shown that your opinion was wrong by several people, and I see you have done no further original research and learned nothing regarding scientific method since then.

What I posted is generally accepted by historians to be correct and as accurate as possible given the circumstances. The data is presented in numerous sources and yet you alone seem to disagree with the accepted authorities on the subject.

Please substantiate your claims, by citing references to literature, that the late production airframes were the same weight as the early production version and that improved engines were 'derated'.

If you cannot substantiate what you say, then please henceforth prefix your comments with: 'in my opinion' so we can all be clear about the origins of what you write.



Regarding FTJR's original request. Some of the literature states that this aircraft was usually operated with one drop tank and one 250-kg bomb.

[Krusty]

Once again Krusty,

Once again nrshida you think you know everything and you attack me when I disagree. I think you're relying too heavily on Francillon, who has been shown a number of times to get the details on Japanese planes wrong. Some of the things you say seem to parrot his mistakes. This is one of them.

It's not my opinion. It's the opinions of others that have done research on the matter, and there is a general concensus. Even "Busa", a forum member here who delves personally into original Japanese resources (he is Japanese himself) has done research that proves the Ha45-21 was derated to Ha45-12 levels (i.e. 1825hp). I've read about it on numerous different places, ranging from j-aircraft.org forums to more research-oriented webpages with excerpts from books and so forth.

The engine which KI84 installed is neither Homare21 nor Homare11 (Ha45sp).
The engine is Homere21 with documents.
But special operation restrictions are carried out.
The performance of the engine is completely the same as Homare12 (NK9 H-B).

The Ha 45-11 and then the -12 was the original engine. While the replacement, the Ha 45-21, was supposed to have 1990hp it never generated this due to many engine problems and quirks. They were derated to run exactly at the same power levels as the Ha 45-12 engines they replaced. End result: NO increase in power. They had a nasty habit of losing all fuel pressure if run too high.

The Ha 45-23 solved some of the problems and quirks with the loss in fuel pressure, but by this time production had been moved to underground caves and the war was almost over. It was so late in the game that the Homare quality was in the sewers. They could not be run at full power. They were derated (perhaps not officially, but they could only output so much power). Also note the theoretical output of the Ha 45-23 was actually lower than the -21 it replaced, at only 1900. Not that it ever showed it could reach this.

The Homare factory was hit by B-29s no less than 12 times between 11/24/1944 and 8/8/1945. The quality and performance of the engines produced actually declined as the war progressed, growing worse and worse until the Ki-84 was useless above 30k at the end. Japanese pilots took off never knowing if they'd have enough power to climb, let alone fight.



This isn't something I should have to re-hash. Take some initiative and do the research yourself. It's out there in the public domain. It's freely available. I'm getting tired of defending myself over and over because others (like you) like insulting me and dismissing anything I type.

[nrshida]

Well you are almost correct Krusty. The devil is in the details which for some reason you fail to sift apart correctly.

Busa's statements which you quoted only pertain to engines which equipped the models of Hayate which have commonly become known in the West as the Ki-84-Ia early production version, and everything he said is generally accepted to be true. I believe based on the power output and weight that this is the version we have in Aces High and I agree with your power output of approximately 1825 hp.

The final version of this model utilized the model 21 engine with a factory-rated output of 1990 hp. This is the model which Busa suggested was detuned and this may be true since the fuelling issues persisted. This unit was replaced by the model 23, as you stated, with an output of 1900 hp, 90 hp less than the model it superceded.

Your fault lies in the assumption as to why this model lost power over its predecessor. In fact the engine starvation issues were solved once and for all with the employment of a lower pressure fuel injection system in this model. This was a design choice and not an accidental consequence of poor manufacture (that came later) nor a deliberate 'derating' / detuning of the unit. The benefit was the resolution of the fuelling issues at the penalty of 90 hp.

The introduction of the model 23 Ha-45 roughly marks the beginning of the so called Ki-84-Ia late production version upon which the four-cannon equipped Otsu was later based (which some people refer to as the Ki-84-Ib). Even at 90 hp less than the previous model it is still superior to the original model rated at 1825 hp. That was my original statement. Disprove this with references to credible literary sources and I will happily accept it and even apologise to you.

Francillon's errors are well known and documented. Your attempts to dismiss his whole body of work based on a few known mistakes is a sad commentary on your research methods and your apparent goal. In fact I did not use Francillon as a source for the power outputs in this instance.

The shocking quality control and manufacturing deficiencies you mention towards the closing stages of the war are impossible to document with any accuracy at all and therefore is open to conjecture. It is however irrelevant to Aces High anyway which I understand does not model this aspect of historical accuracy.

Finally, you continually imply that it is a personal attack on you when this is not the case. I actually don't care about you either way. I'm attacking your academic method, which is at best unsound and at worst nonobjective, biased and illustrative of a fundamental flaw in comprehension.



I apologise to the original poster whose original request has now been derailed by another instalment of 'battle of the hobbyist historians', and can only make amends by again pointing out that one 250 kg bomb and one drop tank was apparently normal operating procedure for the Ki-84.

[FTJR]

I apologise to the original poster whose original request has now been derailed by another instalment of 'battle of the hobbyist historians', and can only make amends by again pointing out that one 250 kg bomb and one drop tank was apparently normal operating procedure for the Ki-84.

I'll accept your apology on the condition that you stop killing me with the dam thing in the MA 

[nrshida]

No disrespect intended.

  to the Raw Prawns, worthy and respected opponents.

[BnZs]

Look, if you want to add more beastly Ki-84s, I'll might vote aye myself, with the understanding that it will be because "The Japanese set needs a perk plane too".

[ink]

Look, if you want to add more beastly Ki-84s, I'll might vote aye myself, with the understanding that it will be because "The Japanese set needs a perk plane too".

yes yes yes...give ma a 4 20 mill cannon KI-84 ill fly nothing but

[Krusty]

Very well I retract any comments of the personal nature. I will try to keep things nice.

However you claiming ignorance of poor Japanese production conditions at the end of the war is facetious. You know better. Or, you should!

We've had many discussions about the Ki-84 and other Japanese craft, the quality and conditions of the engines, the production, the actual performance vs theoretical performance... etc... You've even participated in said discussions! We've (as a community) discussed the engines before as well.

I read a few really interesting things about the production and the different engine of the later models (even on the Ki-84-II) but couldn't find the same resource right now, so I've had to settle for some of the many other easy to find comments.

Whe we even had direct second hand commentary, so diverse is the AH community:

Post by: AmRaaM on July 27, 2005, 11:13:53 PM
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My moms neighbors brother was an engineer at a plant producing k84s during the war, when he came to visit and we all went to dinner he said that the being chosen to shuttle the aircraft to deliver them was akin to being chosen to be a kamakazi pilot, many of the shuttle pilots crashed because of the engineering  with  avail. materials made the plane very dangerous and prone to catastophic failure of various components. Said it was very disheartening to see brand new aircraft and more importantly pilots not making it even a few hundred yards from the runway before hitting the water.

Not to mention too many articles, reports, anecdotes, and actual performance tests and historical documents (the equivelant to a T.O. and other decrees/specifications) that combine to show the piss-poor quality of production as well as the below average performance on new materials across the board.

From Busa:

Finally on documents, the engine which Ki84 installed is Homare21 (Ha45).
But operation restrictions were made the same as Homare11 and Homare12 (NK9 H-B) around April, 1944.
This fact can be checked till around April, 1945.

That's checkable up to and possibly after April 1945.

So... when did they start using that Ha45-23? Was it in the 3 month gap where the Ha45-23 were being built underground before the atomic bombs dropped, effectively ending the war in August 6 1945?

We know the Ki-84 with 4x20mm was literally just taken from the standard production lines. It would match performance and engine power of a typical late-war Ki-84-Ia, if that. Regardless of the designation you want to call it, those planes or that production line was just changed by adding different weapons. The rest of the process was uninterrupted, basically speaking.

taken from:
http://www.j-aircraft.org/smf/index.php?topic=281.0

The so-called 427mph quotation - often claimed from postwar test-flight (Apr-May '46/Middletown AAF Depot, Harrisburg/PA) - was already found published inside a wartime-issued TAIC manual!  Furthermore, the falling-quality of production (esp: 2nd-gen...)Homare's - pre-empted them ever reaching their newly-assigned power-ratings, before 'overheating' or other component-failures.  It's likely that - not withstanding the new exhaust-system contribution - many (or maybe most FRANKS...) likely saw their BEST performances  - only w/their 1st-gen Homare's!(Ha.45-11, Ha.45-12, i.e., with only their original: 1800-1825HP!), and the spec avgas previously commonly available, or whatever.

He was giving a balanced response to an inquiry about Ki-84 performance, giving pros and cons for either the high or low speeds listed, but that is a pretty good example of what you'll find of the late war examples.

The deplorable construction quality is not under debate. The engines were quite regularly derated, and not just because of the fuel injection problems. Seals, rods, pistons, gaskets, valves, the entire system was shoddy, not just a fuel injection nozzle. The derating continued until the end of the war.


I hope that sways you a bit more.


To the original topic: To take 1 step further, some Ki-84s flew with a single DT and no bomb, as well! This was not unusual, as they also did this on Ki-44s and some other craft. Perhaps it was a resource-saving thing (why drop 2 tanks when you only need to lose 1?)

[FTJR]

No disrespect intended.

Never thought there was

[nrshida]

Well fair enough. Shake Krusty?

I did imply with this comment: '...poor manufacture (that came later)' that I wasn't ignorant of the manufacturing problems. The point I was making was how can we quantify this without a plane by plane inventory?

I think we can all here present agree that we'd love to see all kinds of new aircraft and variants introduced. HTC has obviously limitted resources which restricts the rate at which they can introduce new types. Here is a way to introduce another interesting, competitive and apparently popular variant to Aces High at the cost of a tiny external change to the model, a new instrument panel and interior detail and some tweaks to an existing flight model.

Not a significantly larger amount of work than was needed to introduce the last P-47 variant and a lot less work than completely modelling a new aircraft from scratch. The Japanese planeset gets one more example, perked if necessary and everyone's happy. Of course it's their decision as to what they work on so we're just discussing anyway.

What should we do to address or recognise the shortcomings of production? Our current Ki-84 has no problems with the pitch control motor, collapsing undercarriage, fuel starvation problems and so on, although we know these were significant problems in the field.

Should the Ko be dismissed altogether? Should its performance be arbitrarily reduced to reflect the random faults? Should HTC just take Nakajima's data and pretend it is modelling a Thursday morning plane?

Here are some pictures illustrating the visible differences between the Ki-84-Ia Ko and the Ki-84-Ib Otsu:-

This is the Ko, or the Ki-84-Ia we currently have in Aces High:-



and this is the Otsu, the four cannon version (so called Ki-84-Ib):-



Here's the only observable difference. In the gas ejection ports:-






The interior was changed also, to accommodate the slightly larger breeches and to simplify production. Here is our (AH) version:-



Here is the simplified Panel of the Otsu:-



Both photographs of captured examples hence additional labels and some instruments and equipment removed / replaced. Obviously cannons removed from the Otsu. The engine cowls were identical as was the shell casing ejection port.

[JunkyII]

KI84 in game could use a facelift anyways.....