Thoughts on the Nakajima Ki-84 and Kawasaki Ki-100

[Admiral Beez]

On paper these two aircraft look like excellent fighters. The Ki-100 is more of Ta 152 like HA bomber interceptor, but still the Ki-84 and Ki-100 look able to mix it up with the best of 1944-45 fighters. Thoughts? Had better fuels been available I imagine they'd even more impressive.

 

[Just Schmidt]

Honestly I think the Ki 100 is overrated. Sure, it dived well, had a reliable engine and handled well, indeed seem to have been a forgiving airplane. But if the performance figures we have is anything to go on, something in the area of 580 km/h is not going to cut it for a fighter entering service in 1945. I really don't think it can be compared to the Ta-152, though they did try to make it into a high attitude fighter. They did not approach reliability in that role. It was not bad for its 1500 hp radial, and it was an impressive enough feat of engineering to convert it in so little time.

Add to that the overwhelming number of aircraft the allied possessed.That inexperienced pilots could fly it is a mixed blessing, these pilots may have been better served with not having an aircraft at all. I think I've said something along these lines before.

The Ki 84 was plagued by an unreliable engine, and decreasing standards of production didn't help. IIRC it at least initially had problems with collapsing undercarriage. The performance figures I've seen range between app. 630 km/h and 690 km/h. Not enough to set a world record, but quite decent. it entered service long before the Ki 100. Some may not have had a homare that delivered as much as 1500 hp, but I think it was a match for the best upon entering service. Of course it was outnumbered too, though far more were produced. While the unluckier individual examples may have performed no better (or even worse), it was always potentially a superior aircraft, and often so in practice too.

Of course better fuel would help both of them.

 

[Clayton Magnet]

The Ki-100 has always been a bit of mystery to me. Most literature generally sings its praises, as one of the greatest high performance late war fighters to enter service, however that is juxtaposed with its actual performance numbers. The airplane probably would have been excellent in 1942-43, but its contemporaries in 1945 were the P-47N, Spitfire Mk.XIV, Ta-152, etc. Some of which had an almost 100mph speed advantage

 

[Admiral Beez]

Has anyone seen the US report on their testing?

Nakajima Ki-84 Hayate (Gale) 'Frank' from the right

Here we see a Nakajima Ki-84 Hayate (Gale) 'Frank' that had been captured by the Americans and used as a test aircraft. The K-84 was the best Japanese fighter to see significant service during the Second World War, and Nakajima's last radial powered fighter.

www.historyofwar.org

 

[GregP]

The Ki-84 that the Planes of Fame used to have was captured and brought to the USA. While it was with the Navy, it was the most-flown aircraft on the station and accumulated a lot of hours with no reliability issues. Everyone loved it.

Just saying ... from all reports, it was a match for late-war Allied fighters.

About the Ki-100. I have only read good things about it, and I am recalling that the F4U-1d Corsair and F6F-3 Hellcat could fly side-by-side at equal power settings with the Corsair indicating 25 - 35 more mph of airspeed. I have never seen very reliable report of the Ki-100, but would love to. Most of what I have seen are quotes from TAIC estimates of performance. I do have one Japanese book with 367 mph top speed and pretty good climb ... about on par with the F6F-5, which was its main adversary.

 

[tonycat77]

Flying both in IL-2 (i know, i know we shouldn't really use flight sims, but i'm not Elon, so i can't just build them again and fly them). i'd rather have the better climb rate and firepower of the 84.
Both are really not good enough vs P-51's specially at higher altitudes, my best tactic is either bounce someone who decided to kill some poor ensigns flying low or bait them into a scissors or turn fight.
Ki-100 really lacks firepower, 20mms in the hood are excellent, but 2 .50s in the wings are not.

 

[GregP]

A flight sim has very little to do with reality in a WWII fighter that has few, if any, reliable flight reports. But, you know that, Mr. not-Elon. Not a knock on your post, just saying.

I seriously doubt the climb rate often quoted. The Ki-61 was just shy of 3,000 fpm, and the Ki-100 had some 380 more hp and was over 800 pounds lighter. It SHOULD have climbed much better than the Ki-61, all things being equal. I'd expect 3,500 fpm or better, about like an F6F-5 Hellcat.

 

[tonycat77]

A flight sim has very little to do with reality in a WWII fighter that has few, if any, reliable flight reports. But, you know that, Mr. not-Elon. Not a knock on your post, just saying.

I seriously doubt the climb rate often quoted. The Ki-61 was just shy of 3,000 fpm, and the Ki-100 had some 380 more hp and was over 800 pounds lighter. It SHOULD have climbed much better than the Ki-61, all things being equal. I'd expect 3,500 fpm or better, about like an F6F-5 Hellcat.

I tend to agree.
However, while in our commonly available simulations even the williams car in f1 can compete with a mercedes, Redbull's much superior computer and their world leader simulation software makes them competitive with the top team despite having almost always a weaker engine.
Point is, although i'm not a expert, i think we should be able to simulate CG, drag, engine performance, thrust from the blades,etc to a degree that is at least agreeable with combat reports and tests.
IL-2 1946 uses a 20+ year game engine, while the west and eastern front have been updated by many games to a great degree this past few years (DCS, IL-2 Great Battles), I think it's long overdue that the Pacific receives some loving and i think we should be able to at least get 75% right using just a well calibrated fluid based simulation of the airframe itself, in lieu of documents that were probably destroyed some 80 years ago.

 

[GregP]

Most of the WWII sims are just games. They have very little to do with reality. It's been a LONG while but, as I recall in Il-2, the aircraft almost always crash if you land them off-airfield. In reality, real WWII airfields were just off-airport fields and many were quite rough.

Perhaps I misremember ...

 

[Clayton Magnet]

Modern flight sims can be surprisingly good, but have obvious limitations. Especially when trying to model an aircraft like the Ki-100, it really is just a guess, when all the developers have to work with are rough estimations based on badly translated Japanese reports. The aircrafts true performance is lost to history unfortunately. We do know more about the Ki-84, as it was evaluated post war, and spent many years being flown in the US, albeit with a damaged propeller if I remember correctly, that caused a persistent vibration and prevented really exploring the performance. But by all accounts it was a real performer, and could outrun both the P-51 and P-47 at specific altitudes.
I suppose running on good fuel can do wonders, instead of the palm grease and boiled banana's that the Japanese were concocting at the tail end of the war.
I assume the 360mph listed top speed for the Ki-100 was from Japanese reports, but I may be wrong. It was probably capable of much more if tuned and run on proper fuel

 

[Shortround6]

I do wonder about the "running on proper fuel".

The Fuel will have about the same BTUs per pound unless really, really crappy.
What the allied fuel did was allow higher boost to be used without going into detonation.
This assumes your your supercharger has the capacity/ability to provided higher boost (more air) at the desired altitudes.

You could have filled a P-40E with 150 octane fuel, you were only going to get 1150hp at around 12-13,000ft because the supercharger simply wasn't going to flow anymore air unless you over revved the engine.

 

[tonycat77]

Most of the WWII sims are just games. They have very little to do with reality. It's been a LONG while but, as I recall in Il02, the aircraft almost always crash if you land them off-airfield. In reality, real WWII airfields were just off-airport fields and many were quite rough.

Perhaps I misremember ...

Well, i ask you to please reconsider and try experimenting some of the newer ones.
DCS FW-190D9 was made with direct inputs by a surviving pilot for example:

Modern flight sims can be surprisingly good, but have obvious limitations. Especially when trying to model an aircraft like the Ki-100, it really is just a guess, when all the developers have to work with are rough estimations based on badly translated Japanese reports. The aircrafts true performance is lost to history unfortunately. We do know more about the Ki-84, as it was evaluated post war, and spent many years being flown in the US, albeit with a damaged propeller if I remember correctly, that caused a persistent vibration and prevented really exploring the performance. But by all accounts it was a real performer, and could outrun both the P-51 and P-47 at specific altitudes.
I suppose running on good fuel can do wonders, instead of the palm grease and boiled banana's that the Japanese were concocting at the tail end of the war.
I assume the 360mph listed top speed for the Ki-100 was from Japanese reports, but I may be wrong. It was probably capable of much more if tuned and run on proper fuel

I do wonder about the "running on proper fuel".

The Fuel will have about the same BTUs per pound unless really, really crappy.
What the allied fuel did was allow higher boost to be used without going into detonation.
This assumes your your supercharger has the capacity/ability to provided higher boost (more air) at the desired altitudes.

You could have filled a P-40E with 150 octane fuel, you were only going to get 1150hp at around 12-13,000ft because the supercharger simply wasn't going to flow anymore air unless you over revved the engine.

Wouldn't the methanol injection help with knocking?
Japanese and Luftwaffe had large methanol tanks to compensate for lower octane ratings on their fuel (BF-109 enough mw-50 for around 20-30 minutes of use, with basically one hour of flight time on internal fuel).

 

[GregP]

OK, but sims are all the same. There is no turbulence, no feel of g-forces, ... it is all on-screen.

Every single non-pilot person I have taken up for a brief aerobatic ride froze when we got upside down without positive g-force on the airplane. They had never felt like they were going to fall out of the airplane before and just froze.

So, the sim might fly "better," but it's still a sim with no real feeling of flight. I once flew a military simulator that was pretty realistic. But that wasn't exactly a standard PC with a screen in front of it, either. It was a cockpit with screens all around, and you could turn your head and see the scenery without using a hat switch to look sideways on the only screen. So, you could have situational awareness and could see the other airplane as you flew a scissors with him. It made a huge difference in situational awareness.

After that experience, a PC with one screen in front of it is just not much fun by comparison.

 

[GregP]

And I have to say, methanol injection (or nitrous oxide, for that matter) was not something you would use very often. It was NOT like a modern nitrous system that gives you a 100 hp or more "shot" into a well-modulated digital fuel-injected engine. It was a large dump of it into an imperfect intake manifold and there was no guarantee it wouldn't blow a jug or worse.

It was very hard on the engine and was used to save your life when it looked like you were about to die. It was NOT used to go hunt down a wayward bogey over enemy territory. That from multiple pilots who were there. The last thing you wanted to do was to blow up your own engine over the enemy while chasing a possible kill. It could mean death at the worst, severe injury and pain for life, or several years of unpleasant imprisonment at best. So, sure, a few idiots DID chase the enemy with it and got away with it. Most had WAY better sense than to do that. WER was used when you were about to be killed ... mostly to get away from a very BAD situation ... sort of like when Kurt Tank ran away from some P-51s when flying a prototype Ta-152.

The Germans could use WER since they were over Germany. But a P-51 driver over the fatherland wanted his engine to get him home more than he wanted that last victory ... most of the time, anyway.

 

[wuzak]

A flight sim has very little to do with reality in a WWII fighter that has few, if any, reliable flight reports. But, you know that, Mr. not-Elon. Not a knock on your post, just saying.

I seriously doubt the climb rate often quoted. The Ki-61 was just shy of 3,000 fpm, and the Ki-100 had some 380 more hp and was over 800 pounds lighter. It SHOULD have climbed much better than the Ki-61, all things being equal. I'd expect 3,500 fpm or better, about like an F6F-5 Hellcat.

Or a Spitfire Mk V!

 

[wuzak]

About the Ki-100. I have only read good things about it, and I am recalling that the F4U-1d Corsair and F6F-3 Hellcat could fly side-by-side at equal power settings with the Corsair indicating 25 - 35 more mph of airspeed. I have never seen very reliable report of the Ki-100, but would love to. Most of what I have seen are quotes from TAIC estimates of performance. I do have one Japanese book with 367 mph top speed and pretty god climb ... about on par with the F6F-5, which was its main adversary.

Surely when performance was being measured they didn't just rely on the speedo in the cockpit?

 

[GregP]

Don't have any idea, wuzak, and not too sure anyone else around to day does, either. But that has been written by Corky Meyer in several articles, and he was a Grumman production test pilot. They sometimes got an aircraft from the "other guys" to fly against their own product. I've seen nobody from the era disagree with him.

What he said, pretty accurately, was: If ram air was not used, then both the Hellcat and the Corsair flew side by side with equal manifold pressure and rpm. One or the other, and not always the same one, would slowly pull ahead for a short time and then they would fly at the same speed. In service use, the Hellcat did not use ram air in order to prevent carburetor icing. The F4U did use am air. When ram air was being used, the Corsair was very slightly faster when they were flown side by side.

Not my claim. Came via Corky Meyer. All I can really say is the F4U1d/d and F6F-3 used the same basic engine and propeller. The F4U-1a had CD0 of 0.0163. The F6F-3 had a CD0 of 0.0184. That's just under 13% difference, and that didn't seem to affect the speed very much between them with same basic engine and propeller.

The F6F-3 had a propeller with diameter of 13 feet 1 inch. The engine was an R-2800-10. 2,000 hp. No water injection for the 2,000 hp rating at 2,700 rpm. The 10W had a different carburetor.

The F4U-1 has a propeller with a diameter of 13 feet 3 or 4 inches depending on source. The engine was an R-2800-8. 2,000 hp. Later 2,250 hp with water injection (8W) at 2,700 rpm.

 

[Dimlee]

About the post-war evaluation of Ki-100.
"Several Ki-100-Ibs were recovered from Komaki airfield, near Nagoya, and shipped back to the US on board either USS Core (CVE-13) or USS Bogue (CVE-9) in late 1945. At least one of these aircraft was restored to airworthiness at Middletown Air Depot, after which it undertook a series of flights against Allied fighters, including the P-51D. It was found that the Japanese aircraft was extremely maneuverable and capable of staying with the Mustang in a dive and when it pulled out. USAAF test pilots noted that when in the hands of an experienced IJAAF pilot, the Ki-100 could be superior to both the P-51D and P-47N in terms of maneuverability."
Chambers, Mark. Wings of the Rising Sun (p. 132). Bloomsbury Publishing. Kindle Edition.

 

[BiffF15]

Well, i ask you to please reconsider and try experimenting some of the newer ones.
DCS FW-190D9 was made with direct inputs by a surviving pilot for example:



Wouldn't the methanol injection help with knocking?
Japanese and Luftwaffe had large methanol tanks to compensate for lower octane ratings on their fuel (BF-109 enough mw-50 for around 20-30 minutes of use, with basically one hour of flight time on internal fuel).

Good video. I didn't notice but did he mention what year he went through pilot training? Just curious if he was instrument qualified (it didn't sound like it as he is or was a very much contact pilot - flew by sound and feel and not so much by the numbers).

 

[Dawncaster]

Don't have any idea, wuzak, and not too sure anyone else around to day does, either. But that has been written by Corky Meyer in several articles, and he was a Grumman production test pilot. They sometimes got an aircraft from the "other guys" to fly against their own product. I've seen nobody from the era disagree with him.

What he said, pretty accurately, was: If ram air was not used, then both the Hellcat and the Corsair flew side by side with equal manifold pressure and rpm. One or the other, and not always the same one, would slowly pull ahead for a short time and then they would fly at the same speed. In service use, the Hellcat did not use ram air in order to prevent carburetor icing. The F4U did use am air. When ram air was being used, the Corsair was very slightly faster when they were flown side by side.

Not my claim. Came via Corky Meyer. All I can really say is the F4U1d/d and F6F-3 used the same basic engine and propeller. The F4U-1a had CD0 of 0.0163. The F6F-3 had a CD0 of 0.0184. That's just under 13% difference, and that didn't seem to affect the speed very much between them with same basic engine and propeller.

The F6F-3 had a propeller with diameter of 13 feet 1 inch. The engine was an R-2800-10. 2,000 hp. No water injection for the 2,000 hp rating at 2,700 rpm. The 10W had a different carburetor.

The F4U-1 has a propeller with a diameter of 13 feet 3 or 4 inches depending on source. The engine was an R-2800-8. 2,000 hp. Later 2,250 hp with water injection (8W) at 2,700 rpm.

His argument could be said to be error because he overlooked several facts.

It was a common occurrence between different models that IAS read differently. According to Pilot's Handbook, Even if the Spitfire IX and P-47D were flying side by side, the IAS seen by the pilots would have been different. The problem was that the difference between F6F and F4U was very large, and it was caused by the F6F, not the F4U, and Grumman worked on it and the measurement location was changed. In conclusion, the difference between IAS readings was nothing special. The actual speed was shown in TAS after calibration. Since the calculation of TAS includes all errors of IAS, the maximum speed of the document can be accepted as it is. Things like the fact that the F4U was faster than the F6F.

The latest model F4U-1D he claimed was actually an outdated F4U-1A BuNo.17781. It didn't even have a fixed upper section of the cowl flap that even the birdcage F4U-1s had installed for that time. It wasn't an F4U-1D as he claimed, nor was it a lastest model, so it used an older type of propeller blades that was less efficient than the F6F's (As you can see in the F4U-1 BuNo.17781 photo above). According to the report of the US Navy F4U-1 BuNo.17930 and the F4U-1 Airplane Characteristic & Performance, the increase in Vmax was about 14 mph when the F6F type 13 feet 1 inch diameter propeller blades were installed. The test-bad F6F-3 of Grumman's later model (F6F-5) achieved a speed of 410 mph, almost as fast as the early F4U-1A. However, under the similar conditions, the F4U-1A achieved 431 mph. Although both type could not cleared that speed in the mass production models.