N1K2-J Shiden-Kai Performance

[DarrenW]

I believe I read a US informal test of N1K1-J in Philippines and they said it got close to 400mph (before it was written off by landing gear collapsed).

Was this speed obtained in level flight? According to a post-war interrogation of Minoru Genda the N1K2 had a nasty habit of having it's landing gear "fall apart" when diving at 420 mph or more....

 

[taly01]

The N1K1-J seems to have been 360mph in the US test, and the landing gear collapsed upon landing in a crosswind.
I found the thread here N1K1-J Shinden Model 11 contains a linked magazine article of the report. The original test report is floating around on the web somewhere.

Japanese sources are scathing about the N1K1-J poor speed for all combat versions and 343Ku mostly used them for training and recon after they got the 2-J, the N1K2-J test pilot claimed 644kph (400.2 mph).

It depends what Laurelix is trying to model, wartime performance or best case performance. I think these are pretty close.

N1K1-J w/gondola cannon
583km/h (362mph) at >6000m - MIL
607km/h (377mph) at <6000m - WEP

N1K2-J
611km/h (380mph) at >6000m - MIL
637km/h (396mph) at <6000m - WEP

I might try to make these Flight Models for il2:1946 and see if the same engine really can be used for both for these performances!

 

[DarrenW]

The N1K1-J seems to have been 360mph in the US test,

I read the report you provided, thank you for posting it.

It says that the aircraft was tested from a stall up to 360 mph indicated. This is a bit ambiguous as it doesn't say whether it was achieved in level flight or a dive, and without a stated altitude or an airspeed indicator correction factor it's hard to say with any assurance what the true airspeed really was.

And if those figures you present are "best case performance" then I am in complete agreement with you. I never claimed that the Shiden-Kai couldn't match the level speed of the Hellcat IF it were in "factory working order" and maintained/operated as specified by the manufacturer. The problem is that this wasn't the case late in the war for all the reasons that I have explained up to this point.

I feel it's safe to say that, just like with German aircraft during this same period, it would be logical to reduce maximum speed by 20-30 mph (30-50 km/h) from accepted and verified performance figures for the aircraft in question.

 

[Peter Gunn]

This excerpt is quoted from Genda's Blade (page 183):

On 16 October 1945, the time came to ferry flight to Yokosuka. LCdr Shiga met with Cdr Yamada and several Marine officers to discuss plans. One of the officers, a handsome man, appeared very familiar to Shiga. The plan was for a flight of three Shiden-Kais to be escorted by four Corsairs, with the Shiden-Kais in the middle, flanked by a pair of F4Us on the outside. The Americans ordered the Japanese to fly straight and level, otherwise they would be shot down. The 20mm cannon were reinstalled on the fighters, but obviously not loaded. Mechanics attached belly tanks for the long journey.

When all aircraft were airborne, the three Japanese pilots decided to unleash the full power of the Shiden-Kai. With no ammunition, the aircraft was a little lighter. Using high octane American aviation fuel, the Homare engine exhibited it's maximum power. As if on cue, the three ferry pilots gave full throttle and virtually left their escorts behind.

"The Corsairs raced after us at full speed!" recounted CPO Toshio Tanaka. "It was very thrilling and delightful! I gestured to them to speed up and try to catch us"

What I get from this exchange is that the Corsair pilots were set in cruise for the long flight and were caught completely off guard by the actions of the Shiden-Kai pilots. No where does it state that they outran the Corsairs. It's merely a playful story that is often taken out of context.

Speaking of pilot testimonials, here is an excerpt from page 86 of the same book concerning a mission report filed by VF-47 after a 16 April 1945 encounter with the 343rd Kokutai (VF-17 also participated in the action). The Japanese lost nine N1K2s with no losses to US Navy pilots (these figures have been verified):

Pilots of VF-47 who participated in this air battle came out of it with tremendous confidence in the F6F-5. They feel that their aircraft offers them tremendous advantage in firepower, armour protection and speed over the Japanese "Zeke", "Tojo", or "Tony". Even the F6Fs that were hit carried their pilots back to base. In contrast, the Japanese aircraft burned easily, often broke up when hit and seemed to lack effective firepower when in a good offensive position. Moreover, the F6F-5 easily matches the speed of these Japanese fighters. It is evident, however, that these Jap aircraft can out-turn the F6F.

Aside from the obvious misidentification of aircraft here, one can see that the performance of the N1K2 did not impress the Hellcat pilots, even with seasoned pilots at the controls. If the N1K2 could in fact reach 400 mph in level flight there would have been more positive feedback concerning it's performance IMHO.

For what it's worth, the F6Fs involved most likely had wing pylons and rocket launchers so top speed would have been limited to about 380 mph at roughly 18,000 ft.

Excellent post, great info and I think your dissemination of what happened is pretty much spot on. I was always suspect of the claims about the latest IJN/IJA fighters knocking down Hellcats (and Corsairs) at will, sounded like a lot of bollocks to me. I've seen other boards where apparently all the N1K2 had to do was show up and droves of F6F's simply fell from the skies against this mighty giant killer.

I shudder to think, well, an N1K2 pilot might shudder to think what would happen if they ran into the latest P-47N or P-51H, which people tend to forget in their breathless "what if" comparisons, is what they'd be running into. Had the war continued into 1946 those were the USAAF fighters they should be compared with, not to mention the P-80.

 

[taly01]

I was always suspect of the claims about the latest IJN/IJA fighters knocking down Hellcats (and Corsairs) at will,

I think people translated WW2 era Japanese reports as gospel when they were wartime newspaper propaganda. The actual amazing thing about 1945 is that a large Japanese fighter sweep may have 50 planes but then find themselves against some 400 US ones, often it was more like 20 vs 200.

 

[DarrenW]

Excellent post, great info and I think your dissemination of what happened is pretty much spot on. I was always suspect of the claims about the latest IJN/IJA fighters knocking down Hellcats (and Corsairs) at will, sounded like a lot of bollocks to me. I've seen other boards where apparently all the N1K2 had to do was show up and droves of F6F's simply fell from the skies against this mighty giant killer.

I shudder to think, well, an N1K2 pilot might shudder to think what would happen if they ran into the latest P-47N or P-51H, which people tend to forget in their breathless "what if" comparisons, is what they'd be running into. Had the war continued into 1946 those were the USAAF fighters they should be compared with, not to mention the P-80.

Yes, it would have been even a worse blood bath for the Japanese. Thankfully for both sides the war ended before such events took place.

And people tend to forget that most American fighters flying over Japan in 1945 were concentrating on the destruction of airfields for the expected invasion so they normally weren't flying at heights conducive for the element of surprise (a tactic necessary when entering a dogfight). The Japanese on the other hand were waiting over their own territory and could vector on the Americans by means of radar, coast watchers, and reconnaissance aircraft. They most surely had the tactical advantage but still suffered great losses in the end.

 

[Schweik]

Eye of the beholder I guess, its looks don't do much for me, reminiscent of the svelte A6M after one too many wagyu steaks. It's not ugly but not (to me) beautiful.

Again, just my personal opinion on its looks, not performance.

Yeah to me it just has that look of a kind of flying muscle car, while being reasonably elegant (compared to say, a P-47)

 

[DarrenW]

I shudder to think, well, an N1K2 pilot might shudder to think what would happen if they ran into the latest P-47N

On 28 May 1945 a flight of P-47Ns from the 318 Fighter Group ran into the 343rd Kokutai, and knocked down three Japanese pilots and wounded another with no losses or casualties to themselves.

 

[DarrenW]

The actual amazing thing about 1945 is that a large Japanese fighter sweep may have 50 planes but then find themselves against some 400 US ones, often it was more like 20 vs 200.

While this definitely was the case when one counts the total numbers of US warplanes participating in fighter sweeps throughout any given day, individual units of 12-24 aircraft where often tasked with neutralizing Japanese air resistance in localized areas solely on their own or in tandem with another. There were a multitude air bases throughout mainland Japan that could respond locally to attacks at any time with a couple dozen fighters or more. For instance, the 343rd Kokutai were able to muster 40 'Georges' out of a total of 63 airborne before attacking 20 Hellcats of VBF-17 on the 19th of March. Outnumbered two-to-one the Americans brought down four of the enemy while losing six in return. The outcome for the rest of the day was fully in favor of F6F pilots, with eight more verified shoot downs and no losses. The F4U units involved with the 343rd broke even with three victories and three losses to Shiden-Kais. All of these results have been cross referenced and verified.

 

[soaringtractor]

There are many misconseptions and confusions regarding the real performance of this fighter. If you look at the Specification of performance of IJN Fighters table from 10th september 1945, or US TAIC for George 21 or sources like Francillon. They all state the Performance of the N1K2-J was 595km/h at 5600m and 7:22 to 6000m rate of climb.

But they are wrong. Its not feasable and my only explanation to those performance figures is if it had a big external fuel tank under its fuselage which wasnt uncommon for it to mount.
Why are these figures not believable?
N1K2-J has 3800kg loaded weight and a Ha-45-21 (1990hp engine)
Ki-84 has 3600kg loaded weight and uses the same Ha-45-21 (1990hp engine)

Ki-84 with Ha-45-21 had top speed of 674km/h (687km/h according to US TAIC calculations)
It could climb to 6100m in 5:48 (from US TAIC)

There is literally only 200kg weight difference between the two planes and we can see such huge difference in the rate of climb, nvm the top speed. Why would this plane with much better power to weight ratio compared to an A6M3 have a rate of climb worse compared to an A6M3? It makes no sense. Those performance figures just have to be with external fuel tank adding drag and the weight of it is definitly over 3800kg.

So then if they are wrong, what is the real performance of the Shiden-Kai?
Well luckily the N1K2 manual exists.
View attachment 551269
View attachment 551270
View attachment 551271
View attachment 551272

On the first image youll see a left and a right hand side with performance figures.
On the right hand side are the actual japanese flight tests results on the Prorotype N1K2-J which was using derated Ha-45-21 since the engine was suffering issues at the time. It achieved 611km/h at 6000m at military Power and it could climb to 6000m in 6:20 at military power. On the left hand side are the japanese estimated performance values for N1K2-J once the engine is running at its full 1990hp power setting, however its overoptimistic since the engine didnt have as much power at 6000m as they thought it would. They estimated 644km/h at 6000m at military power and 5:15 to 6000m at military power. The actual performance would be about 628km/h at 6000m at military power and 5:30 to 6000m at military power. At WEP the top speed would be about 652km/h

As you can see now it actually looks believable.
Top Speed: (WEP)
N1K2-J - Roughly 652km/h
Ki-84 - Roughly 672km/h

It's unsurprising the final result shows only 20km/h difference in top speed between N1K2-J and Ki-84 when both are using full power Ha-45-21 (1990hp) engine because
N1K2-J with de-rated Ha-45-21 engine achieved 611km/h at 6000m whilst Ki-84 with the same de-rated engine achieved 631km/h at 6000m at Military Power.

Note:
Taic used calcaulations to state Ki-84 top speed. the drag coefficient is a bit overoptimistic. I used the japanese Ki-84 manaul which states 624km/h at 6000m at military power top speed using the Ha-45-11 (1800hp) engine which is what the early Ki-84's had. 1460hp at 5700m = 624km/h at 6000m. With 1625hp at 6000m using this same drag coefficient gives you about 648km/h. At WEP youre looking at about 672km/h

—————————-

N1K2-J Shiden-Kai

Empty Weight: 2650kg
Loaded Weight: 3800kg
Wing Area: 23.5m2
Engine: Ha-45-21
WEP: 1990hp at Sea Level
Military Power: 1825hp at 1750m / 1625hp at 6100m

Max Speed: (Military / WEP)
Sea Level: 529kph / 550kph
1000m: 551kph / 574kph
2000m: 574kph / 597kph
3000m: 597kph / 606kph
4000m: 599kph / 603kph
5000m: 603kph / 628kph
6000m: 628kph / 652kph

Rate of Climb: (Military / WEP)
Time to 6000m: 5:30 / 5:06

Stall Speed: (Sea Level, No Flaps, 3800kg)
158km/h IAS

Sustained Turn Time: (360 horizontal turn, 1000m, No Flaps)
Military Power: 18 sec
WEP: 17 sec

Firepower:
4x 20mm Type 99 Mk 2 (225 rounds per gun)

WHY does it matter ????? The war is over 75 years ago !!!!

 

[Schweik]

Well that's a bit against the raison d'etre of the entire forum...

 

[SaparotRob]

Well that's a bit against the raison d'etre of the entire forum...

..and use lots of punctuation.

 

[taly01]

WHY does it matter ????? The war is over 75 years ago !!!!

There are lots of computer flight simulators that have these planes, some are pay-to-play online competitive games so people like to have "real" plane performance.

 

[SaparotRob]

There are lots of computer flight simulators that have these planes, some are pay-to-play online competitive games so people like to have "real" plane performance.

Do the sims have Griffon powered Whirlwinds?

 

[mad_max]

There are lots of computer flight simulators that have these planes, some are pay-to-play online competitive games so people like to have "real" plane performance.

They do and not just the Theoretical on paper or from one off prototypes that had exceptional performance compared to airframes used in service.

 

[mack8]

Really fascinating this reapraisal of Shiden's speed.

I'm very curious, on the N1K1-J, by how much did the gondolas reduced the speed? Why they went for that solution is beyond me. And also that horrible "wart" on the lower right of the nose, i saw it described as a fuel cooler or oil cooler, how much would that cut into speed too?

There is a later N1K1-Jb (i think) variant with all 4 guns in the wing, very curious what kind of speed would it have compared to the initial model?

 

[AerialTorpedoDude69]

There are many misconseptions and confusions regarding the real performance of this fighter. If you look at the Specification of performance of IJN Fighters table from 10th september 1945, or US TAIC for George 21 or sources like Francillon. They all state the Performance of the N1K2-J was 595km/h at 5600m and 7:22 to 6000m rate of climb.

But they are wrong. Its not feasable and my only explanation to those performance figures is if it had a big external fuel tank under its fuselage which wasnt uncommon for it to mount.
Why are these figures not believable?
N1K2-J has 3800kg loaded weight and a Ha-45-21 (1990hp engine)
Ki-84 has 3600kg loaded weight and uses the same Ha-45-21 (1990hp engine)

Ki-84 with Ha-45-21 had top speed of 674km/h (687km/h according to US TAIC calculations)
It could climb to 6100m in 5:48 (from US TAIC)

There is literally only 200kg weight difference between the two planes and we can see such huge difference in the rate of climb, nvm the top speed. Why would this plane with much better power to weight ratio compared to an A6M3 have a rate of climb worse compared to an A6M3? It makes no sense. Those performance figures just have to be with external fuel tank adding drag and the weight of it is definitly over 3800kg.

So then if they are wrong, what is the real performance of the Shiden-Kai?
Well luckily the N1K2 manual exists.
View attachment 551269
View attachment 551270
View attachment 551271
View attachment 551272

On the first image youll see a left and a right hand side with performance figures.
On the right hand side are the actual japanese flight tests results on the Prorotype N1K2-J which was using derated Ha-45-21 since the engine was suffering issues at the time. It achieved 611km/h at 6000m at military Power and it could climb to 6000m in 6:20 at military power. On the left hand side are the japanese estimated performance values for N1K2-J once the engine is running at its full 1990hp power setting, however its overoptimistic since the engine didnt have as much power at 6000m as they thought it would. They estimated 644km/h at 6000m at military power and 5:15 to 6000m at military power. The actual performance would be about 628km/h at 6000m at military power and 5:30 to 6000m at military power. At WEP the top speed would be about 652km/h

As you can see now it actually looks believable.
Top Speed: (WEP)
N1K2-J - Roughly 652km/h
Ki-84 - Roughly 672km/h

It's unsurprising the final result shows only 20km/h difference in top speed between N1K2-J and Ki-84 when both are using full power Ha-45-21 (1990hp) engine because
N1K2-J with de-rated Ha-45-21 engine achieved 611km/h at 6000m whilst Ki-84 with the same de-rated engine achieved 631km/h at 6000m at Military Power.

Note:
Taic used calcaulations to state Ki-84 top speed. the drag coefficient is a bit overoptimistic. I used the japanese Ki-84 manaul which states 624km/h at 6000m at military power top speed using the Ha-45-11 (1800hp) engine which is what the early Ki-84's had. 1460hp at 5700m = 624km/h at 6000m. With 1625hp at 6000m using this same drag coefficient gives you about 648km/h. At WEP youre looking at about 672km/h

—————————-

N1K2-J Shiden-Kai

Empty Weight: 2650kg
Loaded Weight: 3800kg
Wing Area: 23.5m2
Engine: Ha-45-21
WEP: 1990hp at Sea Level
Military Power: 1825hp at 1750m / 1625hp at 6100m

Max Speed: (Military / WEP)
Sea Level: 529kph / 550kph
1000m: 551kph / 574kph
2000m: 574kph / 597kph
3000m: 597kph / 606kph
4000m: 599kph / 603kph
5000m: 603kph / 628kph
6000m: 628kph / 652kph

Rate of Climb: (Military / WEP)
Time to 6000m: 5:30 / 5:06

Stall Speed: (Sea Level, No Flaps, 3800kg)
158km/h IAS

Sustained Turn Time: (360 horizontal turn, 1000m, No Flaps)
Military Power: 18 sec
WEP: 17 sec

Firepower:
4x 20mm Type 99 Mk 2 (225 rounds per gun)

I came across an interesting comment on a YouTube video which mentioned that the mismatch between top speed of IJN aircraft is because of a translation error. According to this comment, the IJN reported all its top speed estimates in knots, which was standard among some naval forces (knots were once used to gauge ship speeds by counting knots on a rope). A French interpreter recorded the knots as MPH.

The commentor said that his source is from archival content contained within the Pacific Theatre Interrogation Reports (held by the Library of Congress). It is significant because this report was used by other "primary" sources such as Francillon and has informed all post-war scholarship on the N1K's performance.

 

[tomo pauk]

I came across an interesting comment on a YouTube video which mentioned that the mismatch between top speed of IJN aircraft is because of a translation error. According to this comment, the IJN reported all its top speed estimates in knots, which was standard among some naval forces (knots were once used to gauge ship speeds by counting knots on a rope). A French interpreter recorded the knots as MPH.

The commentor said that his source is from archival content contained within the Pacific Theatre Interrogation Reports (held by the Library of Congress). It is significant because this report was used by other "primary" sources such as Francillon and has informed all post-war scholarship on the N1K's performance.

Hate to rain on this parade, but...
Why on earth will US military give such an important job to a Frenchman?? And one person to translate all docs dealing with capabilities of Japanese A/C? Francillion used a host of sources for his book on Japanese A/C. .There is a lot of Japanese tables that post modest performance numbers for their latest aircraft.
As they say - extraordinary claims require extraordinary evidence - it was easy even in 2000 to take photos of original docs and spread them via publications. Hopefully the commentator is a more ... straightforward person than the one that claimed that he saw docs saying that Napier Sabre was good for 5000 HP, but, alas, RR made sure that such docs disappear.

I do hope I'll be proved wrong.

 

[AerialTorpedoDude69]

Hate to rain on this parade, but...
Why on earth will US military give such an important job to a Frenchman?? And one person to translate all docs dealing with capabilities of Japanese A/C? Francillion used a host of sources for his book on Japanese A/C. .There is a lot of Japanese tables that post modest performance numbers for their latest aircraft.
As they say - extraordinary claims require extraordinary evidence - it was easy even in 2000 to take photos of original docs and spread them via publications. Hopefully the commentator is a more ... straightforward person than the one that claimed that he saw docs saying that Napier Sabre was good for 5000 HP, but, alas, RR made sure that such docs disappear.

I do hope I'll be proved wrong.

I'm also very skeptical of the commentor's claim. But there are a few things in it that explain the odd mismatch between IJA and IJN aircraft top speeds.

Regarding your claim that extraordinary claims require extraordinary evidence: we are not dealing with an extraordinary claim. Low IJN top speeds have puzzled researchers like ourselves for years. None of the explanations handle well under scrutiny. Just because someone considers a claim to be extraordinary doesn't mean that the burden of proof is now higher.

But in this case, because the claim is sourced, it's only needed to find the original document in the Library of Congress and then read it for ourselves. It might turn out that the documents or archival footage do not contain what the commentor claims. However, this appears to be a falsifiable claim. There is somewhere recorded tape, video, or documents that can simply read for ourselves and find out the truth.

Regarding the translator, you make a good point. In this case, the commentor said that it was a translator who spoke French (possibly English), and Japanese and they were involved in the interrogations of Japanese ground crew during the TAIC interviews with Japanese groundcrew. However, as you say, there were 6,000+ interpreters who spoke Japanese and English fluently, working for the US military. There would have been no reason to use a French interpreter unless they used diplomatic staff for political reasons.

There are other issues with the claim as well. For starters, the N1K2's top speed was recorded as 369 MPH. If this were knots, it would be completely outside what other sources have claimed. But the commentor claimed that the actual claim was 360 knots for the N1K2 in interrogation. But as all these things are easily scrutinized on examination, it's just a matter of someone getting access to those documents. Unfortunately, the Library of Congress requires people to register in person to access their documents.