Why are the Japanese planes so slow?

[HoHun]

Hi F4UDOA,

>The A6M2 in that report was faster than the F4F-4 at sea level and outclimbed the P-38F to almost 15,000FT.

>So take the listed performance as being a little generous.

The listed performance for which aircraft?

Regards,

Henning (HoHun)

[F4UDOA]

Hohun,

Well based on that report

1. The F4F-4 should have been faster at sea level according to listed performance.
2. The P-38F should have out climbed the A6M2 at low alt.
3. The P-39 as tested was overboosted to 70" MAP and then lowered to 54"MAP. These settings are well above it's normal ratings. Also the Zero overtook t in speed at moderate altitudes and was faster at alt. This is also contrary to stated P-39 performance.

The A6M5 test is most interesting to me. The speeds of the F6F, F4U, P-38L, P-47D as tested are really interesting.

[HoHun]

Hi F4UDOA,

>1. The F4F-4 should have been faster at sea level according to listed performance.

I've listed the USN speeds in my comparison. If something was wrong, it must have been with the F4F-4 as the recorded A6M2 speeds show it being slower than a properly operating F4F-4.

>3. The P-39 as tested was overboosted to 70" MAP and then lowered to 54"MAP. These settings are well above it's normal ratings.

Well, it seems to have been a cowboy style comparison :-) But the Navy figures for the A6M2 look realistic anyway.

(The RAF speed test figures I quoted are for 2950 rpm, 42" Hg. The comparison used 70" Hg, 52" Hg and 55" Hg. It might well be that the USAAF operationally used higher pressures than the 42" Hg indicated by the RAF report, but these were only available at low altitudes of course.)

>Also the Zero overtook t in speed at moderate altitudes and was faster at alt. This is also contrary to stated P-39 performance.

Actually, the report shows that the P-39 was faster at all altitudes though the A6M2 at some altitudes at the better initial acceleration from cruise speed.

Regards,

Henning (HoHun)

[flakbait]

Originally posted by HoHun
Hi Flakbait,

Well, in fact the debate is somewhat academic as both radial and inline engines finally evolved into quite similar three-dimensional engines, so they both have to be considered interim types :-) Note that V engines aren't strictly inline, anyway, nor are twin-row radials strictly radial.

The point about the A6M's radial is simply that it has about the same power as the DB601A, and less than the Merlin III, while being an air-cooled radial with a big drag penalty compared to a liquid-cooled V engine of the same output.

Regards,

Henning (HoHun)

What they evolved into really isn't relavent, as WW2 aircraft either had a skinny, sleak cowling indicating a hot-water motor, or a very round one indicating a radial. And it is a rather moot point regarding the A6M engine being radial since it hit nearly the same speeds as some of the hot-water, 12 cylinder engines with slightly higher HP ratings. Isegrim said radials had higher drag; true, but that higher drag is hardly enough to cause a massive discrepency between a radial fighter and a hot-water fighter. Look at the difference between the P-51H and the P-47M; it's only 17mph (487mph vs 470mph). Look at the difference between the A6M3 and Bf-109E4; 9mph with a 45 hp differential between the two. Everyone knows the Sake 12 (later 21) engine had less hp than nearly every radial and most hot-water 12s. Besides, I posted that info. The most power any Sake-series engine produced regularly was 1,130 hp. Roughly the same as early Alison or DB engines. The kicker is it couldn't crank out any more hp and the more powerful engine designs were held up by bombing, material shortages, or the fact Japanese labor quality stunk by January of '44.

The Japanese military had a nasty practice of drafting any man fit to hold a rifle. This meant people who ordinarily worked on machine tools were stuck in the mud with a gun. What's worse, as the war went on Japan had fewer and fewer people trained in how to work metal to exacting tolerances. How can you expect to get 1,500 hp out of an engine if the cylinder barrels are 0.2" out of round and the valves don't meet spec? You won't. As for why Japanese fighters were so slow when compared to everything else, it could be shoddy workmanship, bad design, faulty carbs, fuel pump glitches or any number of other reasons.



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Flakbait [Delta6]

[HoHun]

Hi Flakbait,

>And it is a rather moot point regarding the A6M engine being radial since it hit nearly the same speeds as some of the hot-water, 12 cylinder engines with slightly higher HP ratings.

Actually, it didn't even come close:

Spitfire I: 571 km/h @ 5000 m, 487 km/h @ sea level
Me 109E-4:  584 km/h @ 5000 m, 480 km/h @ sea level
A6M2:       524 km/h @ 4880 m, 434 km/h @ sea level

Quite obviously, the higher drag of the radial engine was at least partially responsible for that.

Regards,

Henning (HoHun)

[flakbait]

Originally posted by HoHun
Hi Flakbait,

>And it is a rather moot point regarding the A6M engine being radial since it hit nearly the same speeds as some of the hot-water, 12 cylinder engines with slightly higher HP ratings.

Actually, it didn't even come close:

Spitfire I: 571 km/h @ 5000 m, 487 km/h @ sea level
Me 109E-4:  584 km/h @ 5000 m, 480 km/h @ sea level
A6M2:       524 km/h @ 4880 m, 434 km/h @ sea level

Quite obviously, the higher drag of the radial engine was at least partially responsible for that.

Regards,

Henning (HoHun) [/B]

You're ignoring something. The A6M2 had an engine with a max rating of 950hp, which means its giving up 225hp to the 109E4. That's a lot more than just radial engine drag. Take the A6M3 Sake 21 engine which produced 1,130hp, and the differential is only 45hp and 9mph. If you upped the Sake 21 to match the 1,175hp the DB601 pumped out, the difference would probably be 5-7mph and most likely related more to overall airframe design than just engine drag.



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Flakbait [Delta6]

[HoHun]

Hi Flakbait,

>You're ignoring something.

Actually, I think you're overestimating the power of the DB601A-1. It had a maximum emergency rating of 1050 HP, so it's not that far off the 950 HP you're using.

I was using 1000 HP for the Sakai 12, so if it was 950 HP that helps to bridge the gap. (Do you have a good source for that engine's power chart?)

Using the 30 min power for the DB601A-1, which gave 970 HP maximum, the Me 109E-4 still got 465 km/h @ sea level, compared to the Zero's 431 km/h.

>Take the A6M3 Sake 21 engine which produced 1,130hp, and the differential is only 45hp and 9mph. If you upped the Sake 21 to match the 1,175hp the DB601 pumped out, the difference would probably be 5-7mph and most likely related more to overall airframe design than just engine drag.

Well, you're right that in comparison to the Me 109, it's not all engine drag.

If I use the Spitfire I as reference point and reduce its power to 950 HP artificially, guessing the sea level as somewhat below that, I get 448 km/h @ sea level. That's for an airframe with a very similar (actually slightly larger) wing area. It's still 27 km/h faster than the Zero at the same power, and most of that can safely be attributed to the radial engine's drag.

Regards,

Henning (HoHun)

[flakbait]

I'm using a hoge-podge of references because I'm lacking in German and Japanese aircraft books. Mostly Baugher's site (Aircraft of the World), J-Aircraft and Aircraft of WW2 (real thin book). AC of WW2 gives the 109E4 using a DB601Aa engine at 1,175hp while Baugher, AC of WW2 and J-Aircraft have the A6M2 pushing out 940-950hp at takeoff. The A6M3 data from J-Aircraft and Baugher gives 1,130hp from the Sake 21. Hence the reason I chose to compare the 1,175hp DB601Aa with the 1,130hp Sake 21. I really wish I had good power vs alt charts for the Sake and Db engine series, but unfortunately I don't. Still, no matter which way you cut it, the difference in speed between a radial engine and a hot-water 12 of similar power isn't much. Not nearly enough to account for the huge speed discrepancy of Japanese fighters after 1942, anyway.

Here's some links to chew on...

http://www.j-aircraft.com/research/zerofacts.htm
http://www.csd.uwo.ca/~pettypi/elevon/baugher_other/


But back to the original question (sorry for the temp hijack, Kweassa)... how come Japanese aircraft were so danged slow? Bad data, bad engines, crummy workforce or just a lack of innovation? After all, once the Sake 21 came around the Japanese used it on every A6M mark that saw combat and didn't change much of anything until mid '44. The DB601A copy on the Hien was a notorious beast to maintain that rarely put out the same hp twice. The Ha45 engine I don't know too much about. Maybe Busa could chime in on that?


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Flakbait [Delta6]

[Pongo]

The Japanese learned the wrong lesson from their overwhelming success in early  1942.

The western powers learned some of the right lessons from thier failures and successes in 1939-41.

The Americans were just about ready to unleash the results of those lessons. The Japanese faltered on what they wanted and by the time they started to have more modern ideas about what a fighter should be it was too late.
But even then. Planes with good modern deisgn qualities like the Raiden where not looked on favourably even in 1944.

victory disease. (why did the germans invade russia with tanks with 50mm guns?)

counter productive fighter pilot culture

very poor country, seriosly overmatched by her enemies.

The US and Brits could afford to make some huge mistakes in aircraft developement and procurment. The Japanese could not.

[NobAkimoto]

I think it was probably expressed best in the counterfactual series of novels "Super Carrier Yamato"(in case anyone's interested, yeah it's a crazy series of books where Yamato is laid down as an angled deck super carrier...but nevermind about that) when staff officer remarks about how the F8F is eating the newly introduced A7M for breakfast.

"Our engines are at least a decade behind the West, and we simply can't produce them at a high enough quality." Examples of underpowered engines like the Homare 22(NK9K) being used in aircraft intended for service past 1942 by the Navy AGAINST the wishes of aircraft designers shows both a reluctance to move towards heavy designs and perhaps just as importantly an inability to adequately produce these things in quantities where they're going to be making a difference.

I mean let's just compare theoritical 1945 designs between the USN and IJN here.

A7M2-
MK9A Radial 2200hp at takeoff/1800hp 20,000 ft.
Performance: Max Speed- 390mph@21,655ft

F4U-4
R-2800-42W war emergency power 2760hp
Performance: Max Speed- 446mph

F8F-1
R-2800-34W 2100hp at altitude
Performance: Max Speed- 434mph

Any other difference?

Quality of aircraft fuel definitely has something to do with it. American fuel was certainly far better and Japanese industry never came close to reproducing it.

Dunno, probably given equal quality engines and fuel you'd see more competitive Japanese designs, but they had jack **** to work with to begin with and even less to work with as the war dragged on. The A6M itself was a bit of a compromise made by a nation which didn't have the highest quality engines available.

[Karnak]

I don't agree that their engines, as described on paper, were too far behind to break 400mph.  The Ki-46 at the start of the war was already doing 386mph.

If the engine on the Ki-84 was actually putting out 1,650hp at 21,000ft it would be doing better than 400mph.

The Spitfire Mk XIV did 448mph with a 2,050hp engine.  You don't need monster 2,750hp engines to break 400mph.


The options I see are as follows:

1) Japanese engines did not produce nearly the claimed power.

2) Japanese fuel was even worse than is generally thought.

3) Japanese fighters were faster than is noted in surviving records but supporting documentation did not survive or never existed.

4) Allied aircraft and German aircraft were slower than the official speed documents claim.  For example I recall reading that the He219 never broke 400mph level flight in service despite the official speed being 416mph.


Certainly it could be more than one of these things and certainly Japanese aircraft were more adversely affected than others.  However I cannot see a change in fuel taking the Ki-84 from 388mph to 427mph and American comments about the P-51H being slightly faster do not at all match the 323mph at sea level and 388mph at best altitude Ki-84.

[F4UDOA]

Karnak,

I think there are two factors contributing to the disparity of performance between the KI-84 and P-51H.

1. An overstatement of performance of the P-51H.
2. The high octane fuel use by the AAF in the testing of the Ki-84.

The truth lies somewhere in between.

[MiloMorai]

Originally posted by Karnak
For example I recall reading that the He219 never broke 400mph level flight in service despite the official speed being 416mph.

And that was with a 'cleaned up' a/c that had some guns removed, antenna removed and exhaust shrouds removed.

[Karnak]

Originally posted by F4UDOA
Karnak,

I think there are two factors contributing to the disparity of performance between the KI-84 and P-51H.

1. An overstatement of performance of the P-51H.
2. The high octane fuel use by the AAF in the testing of the Ki-84.

The truth lies somewhere in between.

That is the feeling I get too and it is leading me to wonder how many other aircraft had overstated performance numbers published, or how many only obtained the published numbers under ideal circumstances that service aircraft would never have obtained.  If that were true a lot of things I've been looking at would start to make sense and not just for Japanese aircraft.

[joeblogs]

First, the Japanese built (in large numbers) many good radial engines up to about 1200 HP. Most of these were derivatives of western designs licensed from the U.S. & U.K. in the early 1930s. The engines were reliable and the pilots trained to operate them at extremely lean fuel mixtures (hence the remarkably long range in some extraordinary missions in 1941).

Second, the Japanese did not devote much resources to two-stage superchargers until the war was already on. This was due in part to a lack of interest in high-altitude interceptors.

To my knowledge, Pratt & Whitney was the first to put a two stage supercharger on a production engine and it took several years to make them reliable. But P&W had already been experimenting with these for several years prior to the war.

Third, U.S. engine makers made the jump to larger, two row radial engines before the war began. Wright had the reliable 2,600 and P&W got the R2800 into production remarkably fast for the typical gestation period of piston engines. Wright was not so fortunate with the R3350, which was also in development well before the war. The Japanese were nowhere as far along and did not have the option of licensing designs after its relations with the west soured.

Fourth, Japanese manufacturers were operating flat out in order to produce existing designs for the airforce and navy. They did not have adequate resources to simultaneusly develop new engines. In other words, The Japanese industry could not scale up as the U.S. industry did.

BTW there is a similar tale for Italy.

-blogs