KI-84 ? Is it Dissed?

[Shane]

I admit I do like the looks of the ki-84 - very nice lines, good performance overall, but for some reason I just can't wrap my head around it. I attribute this to the tiny instruments and the canopy framing. I also find it interesting the flaps won't deploy at such a relatively slow speed compared with its contemporaries. I haven't really flown it enough, but have done reasonably well in it. I actually think its ENY is a tad too low - ditto for the 109k, but that's just imho. (Both are just as easy-mode as a spixteen.    )

[2bighorn]

If it was modeled using US 100 octane fuel like it did in the US tests, it would be a very, very popular plane.  Right up there with the P-51D but sadly, it's hampered by the Japanese fuel it used and it really did have a negative impact on the performance of the Ki-84.

Sorry, but fuel by itself won't increase performance. However, higher octane fuel makes possible higher manifold pressure.

Ha-45 engine was designed to run on fuel Japanese had at the time. As far as I know, in US tests, even though higher octane fuel was used, max manifold pressures weren't increased above what factory throttle settings allowed.

[Karnak]

Sorry, but fuel by itself won't increase performance. However, higher octane fuel makes possible higher manifold pressure.

Ha-45 engine was designed to run on fuel Japanese had at the time. As far as I know, in US tests, even though higher octane fuel was used, max manifold pressures weren't increased above what factory throttle settings allowed.

I thought they had designed it for 100 octane in the hope that the Japanese petrochemical companies would develop higher quality of fuel?

[2bighorn]

I thought they had designed it for 100 octane in the hope that the Japanese petrochemical companies would develop higher quality of fuel?

No. The difference between Japanese and US KI-84 tests is solely due to the fact that Japanese tests were performed on pre-production aircraft. Production KI-84 had many improvements, most notably the exhaust stacks.

[Citabria]

ki84 like the 205 suffers from very dated graphics. it was the first plane done to ah2 polu count but it was still heavily angular and compared to the more recent additions its very polygonal and not much fun to look at like the new stuff.

its also slow with small ammo load and bad high speed tendancies making it ignored more than the recently redone big ammo clip n1k2.

[Karnak]

ki84 like the 205 suffers from very dated graphics. it was the first plane done to ah2 polu count but it was still heavily angular and compared to the more recent additions its very polygonal and not much fun to look at like the new stuff.

its also slow with small ammo load and bad high speed tendancies making it ignored more than the recently redone big ammo clip n1k2.

Well, to be fair, the C.205 is an AH v1.00 polygon and the the Ki-84 is an AH v2.00 polygon.  That said, while much of it is a significant improvement over AH1 models, its cockpit framing is actually graphically inferior to a number of AH1 models such as the Hurricanes and the pre-update A6Ms.

[titanic3]

ki84 like the 205 suffers from very dated graphics. it was the first plane done to ah2 polu count but it was still heavily angular and compared to the more recent additions its very polygonal and not much fun to look at like the new stuff.

its also slow with small ammo load and bad high speed tendancies making it ignored more than the recently redone big ammo clip n1k2.

  300 Cannon rounds is more than enough. Those MGs alone can get you a few kills if you can sit on their butt for 2 seconds at D200.

[nrshida]

I'm sorry to differ with you Bighorn, but that's not correct. The production aircraft did indeed have altered exhausts and this added some thrust. The prototypes had a grouped outlet system. However the manufacturer's figures for each model is known and the U.S. tests far exceed the best of those. The higher performance for the U.S. test was due to a combination of higher octane fuel and the engine being in tune to use that.



Regarding the flaps, I have similarly been able to find no data regarding a maximum airspeed for flaps to be deployed. I'm sure there was one in the manual or printed on a decal somewhere but I also doubt it was as low as 164 m.p.h as it is in the game. The whole wing structure is really built around this flap design which was carried over from the Ki-43 (and earlier) from the outset and is a distinctive Nakajima feature. If you inspect the deployment rails and mechanism it implies they were intended to be used for manoeuvring and not just landing flaps. The deployment mechanism is hydraulic and the flaps themselves are a considerable structure. There are four rails per flap.

I conjecture that in real life the flaps might limit your speed once deployed and not the other way around. I once had both flaps shot off when deployed and flew around until my fuel ran out experimenting. It was impossible to accelerate past a certain speed (I'm afraid I have forgotten the figure).

I thought I had a convincing case that the flaps were modelled incorrectly in Aces High but trying to substantiate it I'm now not so sure, but I'll present the info anyway for your consideration.


On the instrument panel of Aces High's Ki-84 is a flap position gauge, below and slightly to the left of the manifold pressure gauge. There is no equivalent for this on the instrument panel of the real Ko (this position is occupied by the oil temperature gauge) nor can I find such an indicator elsewhere in the cockpit.

The Aces High gauge is is labelled 0, 15 and 30 degrees respectively although I believe the pointer does go slightly off this scale at the 30 mark which would be commensurate with the specifications.

However, according to Wieliczko's book, there was a third setting for the flaps which we do not have which allowed them to be extended even further to 53 degrees:-

"The flaps were all-metal and consisted of fourteen ribs. They were placed between ribs 2 and 14 and extended asymmetrically on four guides, with hydraulic control. Their maximum extension angle for landing was 53 degrees, 35 degrees for take-off, and 15 degrees in combat maneuvers". [Nakajima Ki-84 Hayate, Leszek A. Wieliczko, Kagero].


I cannot validate this information from a second source, so I suppose we must remain sceptical. Information is so scarce I think a more convincing photograph would clinch it but I have been unable to find one. There is a picture of the flaps deployed in a position apparently exceeding 35 degrees, but perhaps you can judge for yourselves:-




Flaps at 35 degrees from Aero Detail (in which flap deployment maximum angle is states as 35 degrees).





Flap deployment picture from Wieliczko.



I believe the flap positions may not have been discrete however as they were controlled by lever which actuated a hydraulic valve and might have allowed a variable angle of deployment instead of the fixed positions we have.



Regarding the dive of the aircraft: the flight testing implies that the elevators did become very stiff at high speeds which would be reflected in the game, however the shedding of control surfaces in Aces High is rather inexplicable.
 
During a discussion of the development of the Mansu produced Ki-116, which was a developmental version of the Ki-84 featuring a smaller, less powerful and lighter engine fitted to an otherwise identical Ko, Wieliczko mentions that this aircraft achieved 800 km/h (497 m.p.h.) in a dive. In Aces High I believe you would lose all of your surfaces in random sequence by the time you reached that speed, even if unloaded.

Finally there is some evaluation of the aircraft for which the source is not cited but which I am assuming stems from the flight testing of the captured Ko (Ki-84-Ia Late Production version (serial number 2366 assigned tail number S17)):-

"The construction of the Ki-84 was very strong and allowed both rapid maneuvers with high overloads and high speed dives".

[EagleDNY]

Ki-84 flap deployment video - this also has an underside view of it.  It definitely looks like the flap is deploying in excess of 45 degrees. 

http://www.youtube.com/watch?v=NiqBOIVLRig&feature=topics

[2bighorn]

However the manufacturer's figures for each model is known

I'd love to see those figures. I was searching for ages and could not find any, except the official Japanese test on pre-production aircraft, by which AH Ki-84 performance is modeled.

and the U.S. tests far exceed the best of those.

Possible, but we shouldn't speculate unless there's some hard evidence.

The higher performance for the U.S. test was due to a combination of higher octane fuel and the engine being in tune to use that.

Again, just speculation. We know the aircraft was overhauled, but I have never seen any evidence whatsoever about any performance enhancing modifications. Such modifications would also defeat the purpose of testing.


So far, everything points to Ki-84 being (when well maintained) 400+ mph aircraft.

[Slash27]

300 Cannon rounds is more than enough. Those MGs alone can get you a few kills if you can sit on their butt for 2 seconds at D200.

It is "small" when compared to a N1K with over 800 rounds. The rate of fire is faster on the Ho5 than the Type 99s as well so the spray and pray is not a very good option. That being said I think she's the finest dogfighter in game and damn sexy to boot. Like Hayate brother Ink mentioned, she's very tough to boot. We ever get a 4 cannon option I may never touch another plane.

[ink]

It is "small" when compared to a N1K with over 800 rounds. The rate of fire is faster on the Ho5 than the Type 99s as well so the spray and pray is not a very good option. That being said I think she's the finest dogfighter in game and damn sexy to boot. Like Hayate brother Ink mentioned, she's very tough to boot. We ever get a 4 cannon option I may never touch another plane.

oh man I start drooling when I hear 4 cannon KI-84

[Slash27]

I said " to boot" twice and I'm not really sure what it means. 

Give us 4 cannons HTC!!! 


And by us I'm mean just Ink and myself. Well Shida too, he's obviously got good taste.

[FTJR]

When it was released, I couldn't believe the flap speeds, so i found the museum in Japan that had one, I wrote, and by way of reply they sent me a copy of the pilots manual, in Japanese, the extension speeds are correct.

I still have the manual.

[nrshida]

Well that settles it then. FTJR, would you be willing to share a scanned copy of the manual? That would make my day.


Thank you for the contribution EagleDNY but that is a scale model and I'm afraid it looks like 35 degrees to me. Good illustration of the mechanism though.


Bighorn, here are the manufacturer's ratings for the different models of the Homare, as you requested:-

- Ha-45-11 (Ha-45 11-Gata) rated at 1342 kW for take-off (1800 hp) at 2900 rpm and 1230 kW (1650 hp) at an altitude of 2000 m.

- Ha-45-12 (Ha- 45 12-Gata) rated at 1361 kW for take-off (1825 hp) at 2900 rpm and 1245 kW (1670 hp) at an altitude of 2400 m.

- Ha-45-21 (Ha-45 21-Gata) rated at 1484 kW for take-off (1990 hp) at 3000 rpm, 1380 kW (1850 hp) at an altitude of 1750 m and 1208 kW (1620 hp) at an altitude of 6400 m.

- Ha-45-23 (Ha-45 23-Gata) rated at 1417 kW for take-off (1900 hp) at 3000 rpm and 1245 kW (1670 hp) at an altitude of 1440 m.

- Ha-45-25 (Ha-45 25-Gata) rated at 1491 kW for take-off (2000 hp) at 3000 rpm and 1268 kW (1700 hp) at an altitude of 6000 m.


I did not say the engine was modified, I said it was in tune (as opposed to some of those in the field) and I was not speculating, I would have stated that if I was. The data is known. The aircraft was apparently standard, the only difference between the fielded aircraft was the better fuel:-


The Americans captured two aircraft in the Philippines. These received black tailfin numbers S10 and S17 and American markings and were tested by the Allied Technical Air Intelligence Unit - South-West Pacific Area (ATAIU-SWPA). In 1946 two additional aircraft were found at the Utsonomiya Army Flying Training School and transported to America where they were restored to flying condition. They received the numbers FE-301 and FE-302 (later changed to T2-301 & T2-302 respectively).

One of the two aircraft captured in the Phillipines, tailmark S17 was Nakajima serial number 1446 which would make it a Ki-84-Ia Ko Late Production fitted with a Ha-45-21 Homare (which has slightly more power and slightly less weight than the AH version). This is the only remaining existant Ki-84 and is presently situated in the Tokko Heiwa Kinen-kan museum in Chiran, Japan. The aircraft is no longer airworthy and has been allowed to degrade in condition.

Here is the table from Wieliczko:-



The third column is the data from the ATAIU-SWPA tests. Please note the speeds and climb rates.


Slash and Ink, nuts to the 4 cannon Otsu, I say us three get the only Ki-84 Hei, fitted with a single Ho-155 30-mm cannon in the right wing:-
 

http://www.j-aircraft.com/research/30_mm_ho155_browning.htm