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[Günther]

Hi

My question is the following that this aircraft has a top speed of 594 km/h with water-methanol boost which gives it close to 2000hp performance isn't that top speed a bit too low,I've read on many internet sites that its 594 km/h but to me it seems quite odd when the ki-84 does around 630-684 km/h with the same engine (Nakajima Homare)?

[razor1uk]

The Shiden is a bit more 'rounded' (plumper) than the Ki 84.
As a bad analogy, shape wise (a parasitic drag/aero wise) the N1K2 is akin to a shrunken P47 bubbletop, while the 84 is more like a lighter Fw190.
The Shiden should have perhaps better dive acceleration and possibly higher dive speed than the Nakajima, but in level flght (at same altitude,) 'racing' each other, the slimmer 84 should eek ahead IMO, assuming same engine and prop size/area - although I think the N1K2 has longer prop blades by a few inches...

[Bombnick]

Japanese typically tested their warplanes "top" speed at 100 % throttle, not war emergency power (like everyone else did).

This often overlooked fact causes widespread misconception about Japanese planes top speeds. Hayate, for example, achieved 620 kph with 100 % throttle and 680 kph with WEP.

The famous 594 kph value for the N1K initially came from Francillon's excellent "Japanese aircraft of WW2" and it simply got copy pasted a gazzillion times around the net, but it's still without WEP!

TAIC report, for example, lists N1K1-J top speed with WEP as 408 mph (=660 kph!!) at 20.000 ft!

[Günther]

That sounds interesting!,and off course realistic for a 2000 hp class radial fighter.

[Günther]

Also its climb rate to medium altitudes feels bit low even with Gerd's mod.

[Metatron]

Japanese typically tested their warplanes "top" speed at 100 % throttle, not war emergency power (like everyone else did).

This often overlooked fact causes widespread misconception about Japanese planes top speeds. Hayate, for example, achieved 620 kph with 100 % throttle and 680 kph with WEP.

The famous 594 kph value for the N1K initially came from Francillon's excellent "Japanese aircraft of WW2" and it simply got copy pasted a gazzillion times around the net, but it's still without WEP!

TAIC report, for example, lists N1K1-J top speed with WEP as 408 mph (=660 kph!!) at 20.000 ft!

Can you please provide a source for this information? It seems to make a lot of sense.

[Günther]

Also to add many sites write 360-370 mph to add to the confusion maybe it was originally in knots? which means around 667-685 km/h ?

[FANATIC MODDER]

As it turned out, most of the original Pacific Fighters FMs need a rework. Most japanese planes seem to have just a bit less top airspeed that was actually the case. How about the Ki-100? Does anybody knows more about that?
I intend to start working on FMs, it's finally time to do so.

[Juri_JS]

There are a number of other things to keep in mind when discussing this subject. The Japanese tests were done under ideal conditions, with new and perfectly maintained engines. Many N1K2 and Ki-84 serving in frontline units were never able to reach the top speeds achieved in the tests, because of inadequate maintenance of the complex Homare engines and the declining quality of aircraft engine and fuel production at the end of the war.

On the other hand, when the Americans tested captured planes after the war they were able to achieve even higher top speeds than the Japanese during their tests, by using high octane fuel, which wasn't available to the Japanese.

All this makes it very hard to decide, which is the most historical correct max. speed for the N1K2 and Ki-84 in the game.

[Günther]

But also the american planes use their best performace figures.

[Juri_JS]

There are many controversies between experts what the best performance figures of the late war Japanese fighters really were and how reliable the Japanese and American test results are.
The question is very complex and has been discussed numerous times at j-aircraft. Here just a few examples:
http://www.j-aircraft.org/smf/index.php?topic=11204.0
http://www.j-aircraft.org/smf/index.php?topic=3441.0
http://www.j-aircraft.org/smf/index.php?topic=10056.0

[Günther]

Very interesting! and it seems that japanese used military power for top speed tests,but the us in tests they but the plane on its limits using it with WEP.