N1K, J2M and Ki-44 vs. 1941 and 1942 vintage Bf 109

[qaz]

Didn't the avgas used in these tests positively affect the performance of the Japanese aircraft?

It's a common myth that the TAIC performance numbers are derived from US tests with high octane fuel. In most cases, they're just calculated estimates using data that was often dubious. The ones that are derived from actual test data are much tamer.
Reasonably, they would rather overestimate than underestimate the enemy's new fighters at the time, which is pretty overtly stated in the TAIC manual.

Compared to Japanese performance test conditions, very high-octane fuel would certainly not hurt, but would be unlikely to significantly improve speed performance. That is, unless modifications were done to run the engine at higher performance than design, which is unlikely.

 

[Wild_Bill_Kelso]

I myself am highly dubious that a Japanese 2,000 horsepower engine somehow produces a slower aircraft than a US 2,000 horsepower engine, all things being equal (let alone when factors like weight and drag are leaning heavily into the Japanese aircraft's favor, as is the case say, if you compare an N1K to an early to mid- run P-47.)

But unlike with some other planes, there are not of records for the Japanese aircraft on WW2aircraftperformance, and that is the best source I know of. I personally do not have faith in what the 1960s-1980s vintage Bill Gunston or Martin Caidin book says, because I have run into too many other ridiculous and extreme errors in those books, as much as I like them for nostalgia reasons.


Until someone else finds some more accurate records to go by, we really can't do a comparison of N1K with any other aircraft, though I will note that even if we assumed 620-630 kph suggested above, which I suspect is a lowball, the N1K would still probably be very competitive against a 109F or G model. It might not have the advantage in top speed but it would be close enough and still have many other advantages as noted upthread.

 

[Shortround6]

Didn't the avgas used in these tests positively affect the performance of the Japanese aircraft?

This is often said but you aren't going to get much more power just by changing fuel unless your run higher than normal boost pressures.
Now since the Homare was set up to use Methanol/water and if you don't have Methanol/water for the test or the Methanol/water injection system is not working correctly, you could substitute higher rated fuel and run without the Methanol/water to try to get the higher manifold pressure/s.

You may be able to use 100/130 fuel to run at the same pressures that the Japanese 92 octane Plus Methanol/water ran at. But it may require a bit of experimentation to get the mixture right.

 

[qaz]

I myself am highly dubious that a Japanese 2,000 horsepower engine somehow produces a slower aircraft than a US 2,000 horsepower engine, all things being equal (let alone when factors like weight and drag are leaning heavily into the Japanese aircraft's favor, as is the case say, if you compare an N1K to an early to mid- run P-47.)

But unlike with some other planes, there are not of records for the Japanese aircraft on WW2aircraftperformance, and that is the best source I know of. I personally do not have faith in what the 1960s-1980s vintage Bill Gunston or Martin Caidin book says, because I have run into too many other ridiculous and extreme errors in those books, as much as I like them for nostalgia reasons.


Until someone else finds some more accurate records to go by, we really can't do a comparison of N1K with any other aircraft, though I will note that even if we assumed 620-630 kph suggested above, which I suspect is a lowball, the N1K would still probably be very competitive against a 109F or G model. It might not have the advantage in top speed but it would be close enough and still have many other advantages as noted upthread.

I definitely do not mean to say my vague guess there should be considered reliable. Assessing the real top speed of planes with Ha-45/Homare is nightmarish because there were so many varying factors and very few actual test records.

Mainly I just want to caution against the use of high Allied estimates and the lowest-end Japanese tests without context. The actual numbers will be somewhere between.

As for the comparison to P-47, I'm not terribly familiar, but if R-2800 made 2,000hp @ around ~20000ft, military power, it must be considered that the fully-rated Homare actually made ~1650hp @ ~20000ft, military power. This is about where Homare planes achieved their top speeds, as it's near the critical alt for the supercharger, while P-47 of course continues maintaining power higher up.

 

[Shortround6]

I myself am highly dubious that a Japanese 2,000 horsepower engine somehow produces a slower aircraft than a US 2,000 horsepower engine,

Problem is that only P-47 was making 2000hp at altitude. Everybody else (F4U, F6F, the Japanese, An early radial Tempest) were all down around 1600-1700hp, give or take, at around 20,000ft where the max speeds are given.
Granted the P-47 is a bit of porker but it actually had lower drag (at least a low speeds) than the navy fighters.
F6F-3 was good for 315mph at 2,000ft with 2000hp. (Dry)
P-47B was good for 352mph at 5,000ft with 2000hp. It would have been slower at 2,000ft but not over 35mph slower.

If you can find decent speed numbers at low altitudes that will give a better comparison of the drag.

One book (maybe in error) claims 325mph at sea level for a Ki-84, take off was 2000hp but max not at take-off may have been something different?
Power at 5905ft (1800 meters) is given as 1860hp and 1620hp at 20,995ft (6400 meters)
This is is for the Homare 21 engine. Other Homare's could be different.

 

[Snautzer01]

Granted the P-47 is a bit of porker

 

[Wild_Bill_Kelso]

Problem is that only P-47 was making 2000hp at altitude. Everybody else (F4U, F6F, the Japanese, An early radial Tempest) were all down around 1600-1700hp, give or take, at around 20,000ft where the max speeds are given.
Granted the P-47 is a bit of porker but it actually had lower drag (at least a low speeds) than the navy fighters.
F6F-3 was good for 315mph at 2,000ft with 2000hp. (Dry)
P-47B was good for 352mph at 5,000ft with 2000hp. It would have been slower at 2,000ft but not over 35mph slower.

If you can find decent speed numbers at low altitudes that will give a better comparison of the drag.

One book (maybe in error) claims 325mph at sea level for a Ki-84, take off was 2000hp but max not at take-off may have been something different?
Power at 5905ft (1800 meters) is given as 1860hp and 1620hp at 20,995ft (6400 meters)
This is is for the Homare 21 engine. Other Homare's could be different.

Ok well 1650-1860hp at 20,000 ft with a ~7,800 lb aircraft with 39' wingspan and 253 sq ft wing area I think gives you better than 360 mph.

P-40F with 37' / 236 sq ft wing, 8,500 lbs was doing 370 mph at something like 1,100 hp at 20,000 ft
Hellcat with 42' 10" / 334 sq ft wing, 12,500 lb was doing 391 mph with 1,650 HP at 25,000 ft

 

[Shortround6]

P-40F with 37' / 236 sq ft wing, 8,500 lbs was doing 370 mph at something like 1,100 hp at 20,000 ft

A P-40B was around 30-40mph faster than a P-36 at the same altitudes with the same power while being much heavier. Pretty much the same airplane from the firewall back.
There is a lot more than weight and wing area that comprise drag,
The faster a plane goes the less important weight is. Lift goes up with the square of the speed.

The Japanese planes may be faster than some credit them with. But are they 420mph airplanes?

Also it might help not to use USN "Detail Specification" s. If you open up the report and it looks like blue print paper it is pretty certain that all the performance numbers are calculated.
At least six F4F-3s that were involved in different tests didn't make it past 380mph. Best altitude varied by over 1000ft.

Not saying that comparing things down low doesn't have problems but two things we are not taking into account just on thrust are the exhaust thrust and the propellers.
We always assume that the props are 80% efficient but are they? and what works at sea level/2,000ft may not work that well at 20,000ft.
Not all ejector exhausts are the same.
The Ki-84 used a 10ft 2in prop. maybe it was enough ??

 

[Wild_Bill_Kelso]

If anyone has any more real performance data for N1K, Ki-84, J2M, Ki-44 etc. I'd love to see it!

I admit it is just a guess but I suspect the F6F is more draggy than the N1K. It's certainly larger and heavier.

 

[Shortround6]

If anyone has any more real performance data for N1K, Ki-84, J2M, Ki-44 etc. I'd love to see it!

I admit it is just a guess but I suspect the F6F is more draggy than the N1K. It's certainly larger and heavier.

the Drag figures for the F6F are not good,
For 11 US fighters the P-47B is right in the middle, right in-between the F2A-3 and the F4F-3 (and they are tightly grouped) but this is profile drag.
The F6F-3 is next to last, in-between the P-38J and the P-61B and yes there is a huge jump between the P-61 and the F6F-3

the next problem is that all the simple drag models crap out much over 300mph, Much like the problems that the British had with their thick wings and the faster you go the wider apart they get.

 

[Wild_Bill_Kelso]

the Drag figures for the F6F are not good,
For 11 US fighters the P-47B is right in the middle, right in-between the F2A-3 and the F4F-3 (and they are tightly grouped) but this is profile drag.
The F6F-3 is next to last, in-between the P-38J and the P-61B and yes there is a huge jump between the P-61 and the F6F-3

the next problem is that all the simple drag models crap out much over 300mph, Much like the problems that the British had with their thick wings and the faster you go the wider apart they get.

Wait, explain that a bit further? Are you saying the thick wings like of the Hurricane and Typhoon expanded at high speeds?

 

[Simon Thomas]

No, the difference between theoretical drag and actual drag gets wider.

Although in practice, the higher speeds leads to lower pressures on both the upper and lower surfaces, which means the centre of the unsupported skins will deflect ever so slightly and thus the wings will get thicker. (We are talking less than a thou)

 

[Shortround6]

To show the problem with trying to judge speed by appearance.

Curtiss P-40Q, 422mph at about 22,000ft using 1700hp.

Hawk 81 (P-40) with an upgraded engine from an F4F-4.
P & W claims 315mph at sea level and 388mph at 25,000ft using 1,015hp.
They estimated 370mph at 24,000ft in service condition.
The P-40Q managed about 40mph more using over 50% more power and a more "streamlined" nose.

Not saying much of anything about the Japanese fighters, just that it is hard to go on looks alone.

 

[Wild_Bill_Kelso]

No, the difference between theoretical drag and actual drag gets wider.

Although in practice, the higher speeds leads to lower pressures on both the upper and lower surfaces, which means the centre of the unsupported skins will deflect ever so slightly and thus the wings will get thicker. (We are talking less than a thou)

Ah ok. Becuase with some early US and Soviet types, at high speeds weird and very bad things would happen like wheel covers coming partly open etc. This was an issue with P-39, LaGG-3 and others.

 

[Wild_Bill_Kelso]

To show the problem with trying to judge speed by appearance.
View attachment 723389
Curtiss P-40Q, 422mph at about 22,000ft using 1700hp.
View attachment 723390
Hawk 81 (P-40) with an upgraded engine from an F4F-4.
P & W claims 315mph at sea level and 388mph at 25,000ft using 1,015hp.
They estimated 370mph at 24,000ft in service condition.
The P-40Q managed about 40mph more using over 50% more power and a more "streamlined" nose.

Not saying much of anything about the Japanese fighters, just that it is hard to go on looks alone.

P-40Q was a long way from a P-36, not sure what your point is here precisely

 

[GregP]

I myself am highly dubious that a Japanese 2,000 horsepower engine somehow produces a slower aircraft than a US 2,000 horsepower engine, all things being equal (let alone when factors like weight and drag are leaning heavily into the Japanese aircraft's favor, as is the case say, if you compare an N1K to an early to mid- run P-47.)

But unlike with some other planes, there are not of records for the Japanese aircraft on WW2aircraftperformance, and that is the best source I know of. I personally do not have faith in what the 1960s-1980s vintage Bill Gunston or Martin Caidin book says, because I have run into too many other ridiculous and extreme errors in those books, as much as I like them for nostalgia reasons.


Until someone else finds some more accurate records to go by, we really can't do a comparison of N1K with any other aircraft, though I will note that even if we assumed 620-630 kph suggested above, which I suspect is a lowball, the N1K would still probably be very competitive against a 109F or G model. It might not have the advantage in top speed but it would be close enough and still have many other advantages as noted upthread.

I am somewhat dubious when it come to that, too, Wild Bill.

I came across a comparison of the J2M and an F6F-5. The F6F-5 was 5.45 pounds per horsepower and the J2M was 3.70 pounds per horsepower.

For clarity, I attach the file. If you read it, it has a lot to say about the J2M versus the Hellcat, including climb, combat maneuverability and a few other items, and it even mentions the N1K in there.

A lot to think about.

 

[Wild_Bill_Kelso]

(Edit - posted this in the wrong thread, moved to the other one)

 

[Wild_Bill_Kelso]

(moved)

 

[Clayton Magnet]

The Ki-100 has always baffled me. It is usually reported on with glowing praise, yet on paper, seems to have 1941 era Spitfire Mk.V performance.
From Wiki;
" A well-handled Ki-100 was able to outmanoeuvre any American fighter, including the P-51D Mustangs and Republic P-47N Thunderbolts which escorted the B-29s over Japan, and was comparable in speed, especially at medium altitudes"

" The Ki-100 along with the Army's Nakajima Ki-84 and the Navy's Kawanishi N1K-J were equal to the latest Allied types in the final year of the Pacific War."

Not sure how that would be possible, considering the "latest allied types in the final year of the Pacific war" would be P-47N's, P-51D's, F4U-4 and a smattering of Spitfire MK.XIV's all of which would have enjoyed a 80 mph speed advantage

 

[BarnOwlLover]

Latest Allied types were P-51H and P-47Ns, which saw little to no use in the Pacific before the end of the war (only a few P-47Ns were in service and USAAF squadrons were just working up on the P-51H before Aug. 15th 1945). Those were more like 100+ mph faster than the Ki-100.

In fairness to the Ki-100, it was rated a better dogfighter than the Ki-84, and most IJA/IJN fighters preformed better at lower altitudes. But then again, the USAAF's successful pilots held the "don't dogfight at low speeds" edict with Zeros and Ki-43s also applied to most other IJA/IJN fighters, and that all IJA/IJN pilots could be skilled aces. Probably prudent obviously to make those assumptions.

Also remember the PDF earlier in this thread that showed that while a Hellcat had huge overmatch over the Zero, the J2M was a significantly better dogfighter than the Hellcat in the right hands (and shows that all aircraft are compromises, and that comparing a land-based interceptor vs a carrier-based long range fighter could be an apples to oranges comparison).

And though I can see the P-47N not being much more maneuverable than a P-47D, the P-51H was not only very fast, but also very fast climbing (even set up as a long range fighter) and more agile than the B/D models (reduced weight and improved controls). Also, the F8F Bearcat would've been a great foil for most Japanese fighters, but compared to the F6F, it gave up max range, and, initially, air to air armament.