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Frankthetank36
02-22-2010, 07:00 PM
Well, I finally got IL2 compare and it has been quite useful in determining best climb speed, turn rate, etc. However, it seems that some of the planes do not have the same performance statistics as I have seen everywhere else. I have always found it strange that the Japanese never mass-produced a single 400mph fighter during the entire war when all of the other powers had 400mph planes by 1944 (but then again, the Japanese planes generally climb faster so perhaps it is just a trade-off). The N1K2 seems pretty accurate with a 370mph top speed, but all of the sources I have seen say that the Ki-84 had a top speed of just over 390mph and the J2M5 around 380. In IL-2, the Frank is capable of just about 400mph at 100% and 425 with 110% and boost, while the Jack is capable of 430 (a whopping 50mph advantage over the statistics that I have seen everywhere else). Is Oleg making these planes overpowered to make them competitive against P-51s and Corsairs or does he know something that the rest of us don't?

Frankthetank36
02-22-2010, 07:00 PM
Well, I finally got IL2 compare and it has been quite useful in determining best climb speed, turn rate, etc. However, it seems that some of the planes do not have the same performance statistics as I have seen everywhere else. I have always found it strange that the Japanese never mass-produced a single 400mph fighter during the entire war when all of the other powers had 400mph planes by 1944 (but then again, the Japanese planes generally climb faster so perhaps it is just a trade-off). The N1K2 seems pretty accurate with a 370mph top speed, but all of the sources I have seen say that the Ki-84 had a top speed of just over 390mph and the J2M5 around 380. In IL-2, the Frank is capable of just about 400mph at 100% and 425 with 110% and boost, while the Jack is capable of 430 (a whopping 50mph advantage over the statistics that I have seen everywhere else). Is Oleg making these planes overpowered to make them competitive against P-51s and Corsairs or does he know something that the rest of us don't?

ImpStarDuece
02-22-2010, 07:28 PM
The data available for Japanese aircraft is a nasty mix of scantly first hand tests, second and third hand accounts and the occasional test of captured wartime aircraft.

USAAF wartime performance estimates for the Ki-84 are 422 mph, and 407 mph for the J2M2.

It seems odd that the Japanese would be able to achieve circa 375 mph with the Ki-44, with 1520 hp, and then only add a few mph with designs that are only slightly heavier but feature another 300-480 hp.

Ba5tard5word
02-22-2010, 07:29 PM
Well this should be fun...make sure about the altitude listed for a top speed, top speeds differ at different altitudes and so does the true airspeed compared with the indicated airspeed.

And yeah I've never understood why the Japanese never had a good high speed fighter but other people here can answer that way better than I could. Having slower but very maneuverable planes worked well for them in the early war when the planes they faced were pretty slow. I'm not sure if it was a case of them being blinded by early success or the fact that maybe the IJN and IJA weren't able to stay well equipped after around Midway, so they didn't have the resources to put out a good high speed fighter. The Ki-84, N1K1 and J2M are rockets but they were too little too late and were also plagued with problems.

mortoma
02-22-2010, 07:43 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Ba5tard5word:
Well this should be fun...make sure about the altitude listed for a top speed, top speeds differ at different altitudes and so does the true airspeed compared with the indicated airspeed.

And yeah I've never understood why the Japanese never had a good high speed fighter but other people here can answer that way better than I could. Having slower but very maneuverable planes worked well for them in the early war when the planes they faced were pretty slow. I'm not sure if it was a case of them being blinded by early success or the fact that maybe the IJN and IJA weren't able to stay well equipped after around Midway, so they didn't have the resources to put out a good high speed fighter. The Ki-84, N1K1 and J2M are rockets but they were too little too late and were also plagued with problems. </div></BLOCKQUOTE>Top speed of all aircraft is top TAS at optimum altitude, it's as simple as that. This even holds true today for general aviation aircraft. If top speed at sea level is listed for an aircraft it's pretty much both TAS and IAS as they are roughly the same at sea level. In many cases CAS is used instead of IAS as the calibrated airspeed is more useful.

Ba5tard5word
02-22-2010, 09:58 PM
But then when you get to like 10000 feet up the IAS and TAS diverge a lot right?

And something I find annoying is that a lot of casual airplane sources, like wikipedia, will list a top speed without telling what altitude that is for...even some more professional sites will do this, so it's hard to figure out what the plane's performance was. I bet a lot of people get Il-2 expecting something like a P-47 to go 450mph right when they take off and get annoyed when it only goes around 350mph...

AndyJWest
02-22-2010, 10:23 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">...something I find annoying is that a lot of casual airplane sources, like wikipedia, will list a top speed without telling what altitude that is for. </div></BLOCKQUOTE>

Actually, it's worse than that. Quoting a 'top speed' without stating the engine limitations is utterly misleading. Late Luftwaffe planes, with their various boost systems, were theoretically capable of speeds that if they tried to sustain for more than a few minutes, would result in bits of 'precision German engineering' being scattered all over the countryside. Likewise, Allied planes maximum speed is often taken as representing some sort of 'maximum cruise speed' rather than something you only do if you'd rather arrive back at base with a written-off engine than a 20mm cannon shell in the small of your back. Hopefully SoW:BoB will model this a little more realistically.

JtD
02-22-2010, 10:35 PM
I think the Ki-84 and the J2M did not quite achieve the performance we see of them when they were in Japanese service. However, I would like to note that the number you usually see for the J2M are for the J2M3, while you quote the speed for the J2M5.

Also, the popular speeds you see are often for the military rating and not war emergency power, and therefore somewhat slow.

Frankthetank36
02-22-2010, 10:40 PM
So is the P-51's 437mph top speed full throttle with WEP, or just maximum cruise, or what? Just seems like a bit of a disparity when the Ki-84 is noted for its speed and yet the Mustang is some 45mph faster. Or was it because the Japanese fighters were faster relative to American fighters at lower altitudes and therefore the TAS wouldn't be as high?

JtD
02-22-2010, 10:45 PM
To quote:

"...but after the war the Ki-84 was tested in the US with a top speed of 427 mph, beating the P-51 by a small margin and the P-47 by a substantial one".

Guess that is one reason for the Ki-84 to be noted for it's speed.

The advantage noted can only have been at low altitude, at high altitude the power of the engine and the speed of the Ki-84 would drop off, and the US birds would be faster.

Another one is indeed the fact, that it was a lot faster than other contemporary Japanese fighters, in particular the most widely used A6M and Ki-43.

The P-51's 437 mph are at WEP rating, I was referring to the Japanese planes.

Romanator21
02-22-2010, 10:52 PM
I think that although some numbers may be fudged, Oleg decided to model planes at peak performance, straight from the factory and without faults in manufacture and maintenance.

Late war Japanese planes never attained the speed we have in game because of lack of maintenance, and using fuels that were of a much lower octane than the engines were designed for.

Likewise, the wings of Yaks don't seem to fall off in level flight, and the windows don't become opaque yellow. Hispano cannon don't jam while pulling Gs. An overheated engine runs happily for 10-20 minutes before starting to run rough, rather than exploding violently.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Top speed of all aircraft is top TAS at optimum altitude, it's as simple as that. This even holds true today for general aviation aircraft. If top speed at sea level is listed for an aircraft it's pretty much both TAS and IAS as they are roughly the same at sea level. </div></BLOCKQUOTE>

If a source says, for instance "350 mph at sea level" that doesn't necessarily mean that sea level is the optimum altitude. It's always better to mention this optimum altitude. In terms of Il-2, if my plane can go 400 mph at 6000 meters and your plane can go 400 mph at 3000 meters, the stats will say our planes are evenly matched in speed. While true, I have the bigger advantage of altitude, and ability to chose when/how/with whom to fight.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I bet a lot of people get Il-2 expecting something like a P-47 to go 450mph right when they take off and get annoyed when it only goes around 350mph... </div></BLOCKQUOTE>

I remember wasting a few minutes of my life trying to argue with someone that the Me-262 top speed of 600 mph was not measured at sea level. He was stubborn enough to believe it regularly exceeded the speed of sound in level flight at this altitude, and so, wanted to adjust the FM accordingly. http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif

TheCrux
02-22-2010, 11:21 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Ba5tard5word:
But then when you get to like 10000 feet up the IAS and TAS diverge a lot right?

And something I find annoying is that a lot of casual airplane sources, like wikipedia, will list a top speed without telling what altitude that is for...even some more professional sites will do this, so it's hard to figure out what the plane's performance was. I bet a lot of people get Il-2 expecting something like a P-47 to go 450mph right when they take off and get annoyed when it only goes around 350mph... </div></BLOCKQUOTE>

Very true, and if I may add, the numbers "on paper" only represent the peak, and at optimum conditions, which will vary greatly from A/C to A/C due to weight/wing-loading, aerodynamics, engine power curves, and altitude ( and how easily you can get there ). It quickly becomes apparent that in many A/C, one cannot hit top speed with a quick wave of a magic wand, or conversely, be nearly uncontrollable at it's top speed.

AndyJWest
02-22-2010, 11:49 PM
Just to add another factor - top speed is 'top speed in level flight': how often is this actually relevant to an air-combat situation? I'd have thought general performance over a broad range of speeds and altitudes was more significant, not to mention factors not susceptible to simple numeric comparison - early bubble-top P-51s were probably slower than razorbacks, but the bubble canopy was adopted for good reasons. Likewise, much earlier in WWII, the RAF accepted the known penalties of installing external rear-view mirrors on fighters. Can anyone put a numeric advantage to that? And if they can't, do they think the RAF were wrong? An Obsession with a particular aspect of aircraft performance is unlikely to tell us much about the realities of air warfare.

BillSwagger
02-23-2010, 12:07 AM
I think the fuel quality had a lot to do with the performance (or lack there of) for some of the late war Japanese planes.

In order for the Japanese to get a Ki-84 to run at 427mph top speed they need to have run it with 100 octane av gas. The engine was designed to run with 92 octane, but the USAAF was able to use the higher octane and get higher boost pressures which resulted in the top speed above 20,000ft.

There is probably a varied degree of data based on different accounts and tests depending on the quality of fuel grade. I read somewhere they were using turpentine mixed with gasoline at one point.
Its also argued that the Ki-84 of 1944 may have outperformed the Ki-84 of 1945 for this reason.
I think the game tends to take an optimistic approach to most planes so we see the 400+ mph performance. Whether that actual performance was attained in combat has much to do with the time period and region the plane was flown from.



Bill

Frankthetank36
02-23-2010, 12:08 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by AndyJWest:
Just to add another factor - top speed is 'top speed in level flight': how often is this actually relevant to an air-combat situation? I'd have thought general performance over a broad range of speeds and altitudes was more significant, not to mention factors not susceptible to simple numeric comparison - early bubble-top P-51s were probably slower than razorbacks, but the bubble canopy was adopted for good reasons. Likewise, much earlier in WWII, the RAF accepted the known penalties of installing external rear-view mirrors on fighters. Can anyone put a numeric advantage to that? And if they can't, do they think the RAF were wrong? An Obsession with a particular aspect of aircraft performance is unlikely to tell us much about the realities of air warfare. </div></BLOCKQUOTE>

^Have you played the Glowing Glory campaign that comes with the game? I did, and I found that when it had me flying the Raiden, the P-51s were not particularly hard to take out, despite the plane's horrendous visibility. When it switched to the much slower Shiden, things got far more difficult. I simply could not get an altitude advantage and hold it, nor could I catch the Mustangs while they made their passes with absolute impunity. There is a big difference between a 370mph fighter and a 400+mph one.

JtD
02-23-2010, 09:14 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">If a source says, for instance "350 mph at sea level" that doesn't necessarily mean that sea level is the optimum altitude. It's always better to mention this optimum altitude. In terms of Il-2, if my plane can go 400 mph at 6000 meters and your plane can go 400 mph at 3000 meters, the stats will say our planes are evenly matched in speed. While true, I have the bigger advantage of altitude, and ability to chose when/how/with whom to fight. </div></BLOCKQUOTE>

Well, as a general statement that might be ok, but it is not as simple. A relevant match up would for instance be a Bf 109E vs. a Spitfire V LF. The performance advantage of the Spit down low is so large, that the 109 cannot do it much harm.
Speaking of the Spit V, this is one of the historical planes where high altitude performance was given up for added low altitude performance, and considered worth it.

Frankthetank36
02-23-2010, 09:20 AM
^What exactly determines whether a plane performs better at high or low altitude? Is it just supercharger ratios, or is it a more complex aerodynamic issue?

JtD
02-23-2010, 09:32 AM
Basically the engine, and there the supercharger.

But if you really mean "what exactly" determines this, then it becomes complex. Aerodynamics play their part, too.

Wildnoob
02-23-2010, 11:03 AM
The Ki-84 top speed in game is the 687 km/h obtained in post war US trials with 140 octane. The Japanese tried to provide 95 octane for the plane, but at end standard 87 octane was used. In witch the top speed was 624 km/h.

Wildnoob
02-23-2010, 11:11 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Romanator21:
Oleg decided to model planes at peak performance, straight from the factory and without faults in manufacture and maintenance. </div></BLOCKQUOTE>

The Ki-84 top speed in game is the 687 km/h obtained in post war US trials with 140 octane. The Japanese tried to provide 95 octane for the plane, but at end standard 87 octane was used. In witch the top speed was 624 km/h (prototype's and high quality pre production models data). As the war progressed speed started to drop, but this that should be the "peak performance".

Heliopause
02-23-2010, 11:32 AM
I thought the Japanese used 80-octane fuel.

JtD
02-23-2010, 11:47 AM
92 and 87 were common.

TinyTim
02-23-2010, 12:03 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Wildnoob:
The Ki-84 top speed in game is the 687 km/h obtained in post war US trials with 140 octane. The Japanese tried to provide 95 octane for the plane, but at end standard 87 octane was used. In witch the top speed was 624 km/h </div></BLOCKQUOTE>

At 100% or WEP?

M_Gunz
02-23-2010, 02:06 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JtD:
To quote:

"...but after the war the Ki-84 was tested in the US with a top speed of 427 mph, beating the P-51 by a small margin and the P-47 by a substantial one". </div></BLOCKQUOTE>

Strange. I have 1942 P-47B trial putting to speed at 429mph at 27,800 ft. There it is. (http://www.wwiiaircraftperformance.org/p-47/p-47.html)

M_Gunz
02-23-2010, 02:13 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Ba5tard5word:
But then when you get to like 10000 feet up the IAS and TAS diverge a lot right? </div></BLOCKQUOTE>

Grab yourself a copy of this, maybe even print it out. (http://www.maw-superaereo.it/utility/IAS-TAS-CHART.pdf)

TAS is 20% more at 3km alt which is about 9,843 ft.

horseback
02-23-2010, 02:58 PM
Generally speaking, the fit and finish of late war Japanese aircraft was very inferior to early war production standards. Attrition in skilled manpower and the low availability of critical materials took a serious toll on their manufacturing quality. As a result, the factory fresh production model was often much slower than the hand made preproduction models' test flights would indicate.

In the case of the Frank, what I've read indicated that performance dropped off fairly quickly over 20,000 ft, and great efforts were expended trying to super- or turbocharge the engines to get better high altitude performance, to counter the expected high altitude bombing raids of B-29s from China. These were unsuccessful, at least in terms of reaching fullscale production before war's end.

I would therefore expect that the top speed of the 'ideal' Frank was achieved between 18 and 20 thousand feet, where it would be very competitive with Mustangs and -1 Corsairs, and slightly faster than the P-47D/N.

Our understanding of how good some of the late war Japanese fighters actually were or should have been is badly skewed by their poor manufacturing conditions, fuel and maintenance problems and the vast training/experience advantages of the Allied fighter pilots who encountered them in combat.

History tells us that they were much better than what came immediately before, but still overmatched. However, there were other factors at work.

cheers

horseback

BillSwagger
02-23-2010, 04:22 PM
Here's a translated flight manual for the Ki-84.

Includes performance specs as well as consumption rates.

Section III shows aircraft limitations.

http://translate.google.com/tr...=ja|en&hl=en&ie=UTF8 (http://translate.google.com/translate?u=http%3A%2F%2Fwww.warbirds.jp%2Fsiryo%2 Ffrank.htm&langpair=ja%7Cen&hl=en&ie=UTF8)

(untranslated) http://www.warbirds.jp/siryo/frank.htm

And a little blurp on a P-47B and P-47M test flight.
The whole article is a great read, but the P-47M part goes into the use of dive flaps.

http://findarticles.com/p/arti...10/ai_n9324510/pg_7/ (http://findarticles.com/p/articles/mi_qa3897/is_200310/ai_n9324510/pg_7/)



Bill

Frankthetank36
02-23-2010, 10:28 PM
So did the Japanese never develop 140-octane fuel, or was it simply not available to them when they were cut off from Indonesia?

JtD
02-23-2010, 10:31 PM
They didn't have it, as their engines didn't need it.

zardozid
02-26-2010, 01:50 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Frankthetank36:
So did the Japanese never develop 140-octane fuel, or was it simply not available to them when they were cut off from Indonesia? </div></BLOCKQUOTE>

I believe that Japan lacked the refinery's to produce high octane fuel...I (think) that their where some underground stores of raw crude oil, but the refinery plants had been destroyed.

Gaston444
02-27-2010, 02:34 PM
Top speed for the Ki-44 Tojo was quoted as 650 km/h in a 1945 Japanese home defense wartime self-evaluation. This is a wartime Japanese document, and in fact that Ki-44 unit was evaluated as the only unit of a satisfactory combat standard for the Tokyo defense area, even with the famous 244th Sentai present.

The short-nosed Ki-61 Kai-1a,b,c used by the 244th Sentai was quoted in that document as having a top speed of 595 km/h, making it one of the Japanese fighters that closely match widely published post-war top speeds.

The Ki-100, which weighted exactly as much as the short-nose Ki-61 (it was barely a little heavier), is quoted as 590 km/h, but had 325 more hp. So the widely quoted top speed of 590 km/h is not possible, and 620-630 km/h is much more likely.

The later longer-nosed Ki-61 Kai-1d was 600 lbs heavier and slower at 580 km/h, and, despite amounting to half the 2400 Ki-61s built, was widely used as a Kamikaze aircraft, or for spare parts to keep the earlier short-nose in service. An amazing waste of ressources... I have never seen a single picture of one flying, though these probably exist...

Many Japanese aircraft commonly quoted top speeds are at Military Power: Japanese tests often did not include full War Emergency Power. This explains the discrepancy with US captured tests, that were run with in-service Japanese fuel standards (What would be the point otherwise?). This has been discussed many times over decades now...

Interviews of captured Japanese pilots confirmed the Ki-84 as having an in-service top speed of about 700 km/h, the fastest of WWII Japanese fighters. (And still considered by the Japanese as so inferior to the Ki-100 that one Ki-100 could, in mock combat, take on 3 Ki-84s and still win, and repeat that when exchanging pilots: Source: "Aeroplane"...)

J2M3 and N1K1 were also tested by the US TAIC at 650 km/h, which is much more consistent with the available 1800 hp+ power output than the usually quoted 595 km/h...

Late Ki-43-IIs were quoted as 530 km/h, but 550-560 km/h seems much more likely, since the 576 km/h quoted for the later III was achieved with only 150 more hp (1230 vs 1180). Note that Ki-43-II/III production is so late-war in nature that well over a third of all the 5900 built (2124 total) were made AFTER April of 1944 by the Tachikawa Hikoki plant... One can only conclude that given the availability of more advanced types, the later Ki-43II/IIIs still produced comparatively favourable results, if only because of better reliability...

The early, lighter, A6M5 Zero is quoted at 570 km/h with 1180 hp, which is not implausible. The slightly slower but much more heavily armed later versions were a massive improvement that came far too late... The problem was that the Navy Type 99 20 mm guns had far too slow a rate of fire for effective wing-mounted convergence fire with only one gun per wing, a source of continual and bitter complaint from Zero pilots. (The Army's Ho-5 20 mm had nearly double the rate of fire when mounted in the wings, so no such complaints there...)

Japanese top speeds are a real can of worms, but US captured tests do offer a reliable guide to the real top speed: If the Ki-61 was tested by the US at the correct 595 km/h, why would the same US tests of the Ki-84 at 683 km/h, and the J2M3 and N1K1 at 650 km/h, be unrepresentative?

With the exception of the Ki-43, Ki-61 and Zero, the late-war single engine Japanese fighter set were all 400 MPH+(640 km/h) fighters (the Ki-100 being real close). The power output alone makes it obvious...

Oleg apparently did this correctly.

Gaston

P.S. This has all been discussed many times before, and the widespread conclusion on top speeds was the above...

G.

Gaston444
02-27-2010, 02:43 PM
That was 50 more hp on the Ki-43-III over the II, not 150... But there were refinements in the III's exhausts and cowling shape.

Still, the Ki-43-II is plausibly closer to 560 km/h if the III was at 576 km/h.

Gaston

horseback
02-27-2010, 05:23 PM
Horsepower is not the primary determiner of top speed. P-47D, Corsair and Hellcat all had the same engine (R-2800) with the same horsepower but very different top speeds and accelerations at varying altitudes.

Drag, fit and finish make a big difference as well.

Ki-100 bested 3 Ki-84s? Only if they fought under Japanese style turning dogfight rules, and the Franks were not permitted to extend. I understand that the Japanese thought that the Frank was significantly superior to the razorback Mustang from their tests, but the combat results came back badly skewed in the other direction. Put Allied pilots in those cockpits and I'd wager the Frank takes out 3 Ki-100s more often than not, assuming the engines were working close to properly (a crapshoot, in real life).

The game engine still appears to favor lightweight turn type fighters over heavier wingloaded high speed type disproportionately.

cheers

horseback