XP-39 II - The Groundhog Day Thread

Ivan1GFP · Oct 27, 2020

Peter Gunn said:
Regarding the Zeke/Zero testing referenced above, were the test pilots also probably aware that this was a finite resource that they did not want to push too hard lest they lose it? I always speculated that these EA were not pushed to the edge so as to preserve them for continued testing and not cause irreparable damage ergo cancel further testing.

As GregP points out, that particular test is at a lower RPM and MAP than the SAKAI seems capable of.

Hello Peter Gunn,

I don't think this was really the problem. This A6M3 was rebuilt from wrecks. There were plenty of engines. There were plenty of wrecks that they were working from.
They simply had no experience with the Mark II fighter and the Japanese were not kind enough to supply a manual, so they had to make best guesses. They might have also been using some equipment from A6M2 aircraft without knowing any better.

Hello SaparotRob,

The A6M2 was the Navy Type Zero Carrier Fighter Model Two One.
The 'Zero' was for the year of adoption (1940 or 2600 in the Japanese calendar).
The Allied code name was "Zeke".
The A6M3 short wing version was the Navy Type Zero Carrier Fighter Model Three Two.
The Allied code name was "Hap" because they originally thought it was a completely new fighter.
Eventually it was renamed "Hamp" and then "Zeke-32".

There were many "Type Zero" aircraft in Japanese Service.

The Army used a pretty similar system.
The Ki 43 Hayabusa was the Army Type 1 Single Engine Fighter.
The Allied code name was "Oscar" or "Ben" earlier in the war.

- Ivan.

SaparotRob · Oct 27, 2020

I knew about the reporting names but I was wondering what name the A6M (any variant) was most popularly known by. BTW, the A6M3 reporting name was changed to Hamp because General "Hap" Arnold said so. At least that's the "Caidin" version.

SaparotRob · Oct 27, 2020

fubar57 said:
You could include the "Rufe" A6M float-plane as well.

That was a classy airplane.

fubar57 · Oct 27, 2020

I'm not quoting Caidin but from what I've read, Arnold was mightily P.O.'d and hauled the guy in charge, Captain Frank T. McCoy in for a severe keester kickin' and the name was quickly changed

SaparotRob · Oct 27, 2020

fubar57 said:
I'm not quoting Caidin but from what I've read, Arnold was mightily P.O.'d and hauled the guy in charge, Captain Frank T. McCoy in for a severe keester kickin' and the name was quickly changed

You must have been posting this just before my comment about General Arnold.

GregP · Oct 27, 2020

The official designation of the early A6M was "Navy Type 0 Carrier Fighter." If was a "Type 0" because the Japanese calendar rolled over to 0 (actually 2600) in 1940. The designation was A6M. The "A" in "A6M" meant carrier-based fighter. It was the 6th carrier-based fighter built for the IJN, and the M meant the manufacturer, Mitsubishi. Hence, A6M was literally "carrier-based fighter, 6the type, by Mitsubishi."

It was called a Zero because that was the Japanese term for it and we used it, too. If was given the Allied Code name "Zeke." We gave make name to fighters. Japanese pilots called it the Reisen (rei sen = Zero sen).

Later, two variants received their own code name. The floatplane was called Rufe, and the A6M3 was originally thought to be a new type and was called "Hap," but that was an embarrassment to General Henry "Hap" Arnold, so it was changed to "Hamp." After it became known the A6M3 was just another Zero, the name stayed because it was already in use.

jmcalli2 · Oct 27, 2020

Ivan1GFP said:
Hello jmcalli2,

Actually that helps a lot.

Note that the P-39D In this particular test was only able to achieve 358 MPH @ 13,000 feet.
The aircraft was not carrying a belly tank or any of the mounting hardware in that particular test configuration.
It was making about 20 HP more than nominal and at the typical critical altitude for the early model P-39.

The only way this is 40 MPH faster than the A6M2 is if the A6M2 is puttering along at cruise power +50 mm Boost 2350 RPM (275 Knots).

- Ivan.

Seems to me you're cherry picking your test results.
The fastest P-39 was the N, clocked at 398.5.
The fastest A6M couldn't hit 360, even the versions with increased HP.
And the A6M had a very hard time maneuvering above 300; those big ailerons were very hard to move.

The problem the P-39 had in the PTO was in large part due to the USAAC being at the bottom of the learning curve in tactics and maintenance while the Japanese were experienced in both.
The Japanese had their logistics worked out, the USAAC did not.
The P-39s were often sent up to intercept Japanese bombers flying at 20,000 ft. It would take 6-8 minutes for a P-39 to reach them, by which time the bombers would be gone. Meanwhile, the climbing P-39s would be bounced by A6Ms.
Try reading P-39/P-400 vs A6M3 Zero New Guinea 1942 by Michael John Claringbould. It has some good combat accounts, some of which will say the P-39 and A6M were close in speed, some were the P-39 was faster, likely due to acceleration being close for the two aircraft. But the main reason to read the book is the in-depth look at combat records; the P-39 and A6M were even in the win-loss stats. That surprised me.

As for the A6M having a service ceiling of 35-38,000 ft, that didn't mean that it fought at that height.
Service ceiling means the rate of climb is 100 feet/minute.
A6M performance fell off at 20-22,000 ft, like the P-39's did at 18,000 ft. That 2-4,000 ft made a difference.

Also recommended is this December 1942 comparison report between the A6M-2 and various US aircraft including the P-39D: http://www.wwiiaircraftperformance.org/japan/intelsum85-dec42.pdf

jmcalli2 · Oct 27, 2020

Ivan1GFP said:
Hello jmcalli2,

Actually that helps a lot.

Note that the P-39D In this particular test was only able to achieve 358 MPH @ 13,000 feet.
The aircraft was not carrying a belly tank or any of the mounting hardware in that particular test configuration.
It was making about 20 HP more than nominal and at the typical critical altitude for the early model P-39.

The only way this is 40 MPH faster than the A6M2 is if the A6M2 is puttering along at cruise power +50 mm Boost 2350 RPM (275 Knots).

- Ivan.

An interesting thing is the variation in performance from one aircraft to another. it could be due to many things; better/worse tune on the engines, length of time for the speed run, etc.
Remember the purpose of the test was to measure the difference in performance with and without the drop tank and shackles. It could be that the test was to run at altitude X for Y seconds at WO throttle. The aircraft may not have reached maximum speed. We'll never know.

GrauGeist · Oct 27, 2020

SaparotRob said:
As long as we're on the subject, in World War 2, was the A6M more popularly known as the Zeke or the Zero?

Their own pilots were known to call it a zero as well: reisen or rei-sen.

There were at least three other Type 0 aircraft in service, two being recon and one was the L2D (Douglas license) transport.

All were Type 0 because the Japanese used the last one or two digits of the Imperial year to denote "type" when the aircraft enters service.
Imperial year 2600 (1940) = Type 0

The A6M meant:
A = Fighter, Carrier based
6 = 6th type in the A class
M = Mitsubishi

The number following A6M meant revisions to the aircraft production (A6M2, A6M5, etc.)
And the Model number that followed denoted modifications to that particular production type.

As an aside, the aforementioned L2D Type 0 transport was manufactured by Nakajima, but it's designation is as follows:
L = transport
2 = second type in the transport class
D = Douglas

P-39 Expert · Oct 27, 2020

wuzak said:
Interesting that you omit aircraft that were around in 1941/42 that could fly and fight at 30,000ft and above. Such as the Bf 109 and Spitfire.

Was listing the planes that couldn't cruise at 30000' in 1942.

DerAdlerIstGelandet · Oct 27, 2020

Well since the war was only going on for a year in 1942, they had not developed aircraft that could cruise at 30K.

SaparotRob · Oct 27, 2020

Right, Zero it is.

Ivan1GFP · Oct 27, 2020

jmcalli2 said:
Seems to me you're cherry picking your test results.
The fastest P-39 was the N, clocked at 398.5.
The fastest A6M couldn't hit 360, even the versions with increased HP.
And the A6M had a very hard time maneuvering above 300; those big ailerons were very hard to move.
,,,,,,,
Also recommended is this December 1942 comparison report between the A6M-2 and various US aircraft including the P-39D: http://www.wwiiaircraftperformance.org/japan/intelsum85-dec42.pdf

Hello jmcalli2,

I referenced the report you listed because P-39 Expert was constantly claiming "40 MPH faster" when we were comparing the early P-39 and A6M2.
The P-39N was that fast in one test. Most references don't ist it as quite that fast.
As I commented recently, I am not claiming any version of the A6M was really particularly fast.

Regarding IIS 85, I am quite familiar. I have already quoted from it quite a few times.

- Ivan.

GregP · Oct 27, 2020

The A6M didn't have especially big ailerons. They were long but rather narrow. The gearing left something to be desired.

In general ailerons should have from 1/8 to 1/4 chord and the length can run from about 1/4 span to half span minus fuselage half-width.

The ailerons on the Zero are about 8.7% of the wing area and about 7.8% on the P-39. There is not much difference there, but the internal gearing of control surfaces in another story. Both the Bf 1098 and the A6M could have had the aileron gearing addressed during the war, but neither was.

windhund116 · Oct 27, 2020

SaparotRob said:
I knew about the reporting names but I was wondering what name the A6M (any variant) was most popularly known by. BTW, the A6M3 reporting name was changed to Hamp because General "Hap" Arnold said so. At least that's the "Caidin" version.

Yes. Also according to Japanese Aircraft Code Names, by Robert Mikesh. Schiffer Military Press. 1993. Pages 15 & 63.
-----

"The Ki 43 Hayabusa was the Army Type 1 Single Engine Fighter.
The Allied code name was "Oscar" or "Ben" earlier in the war."

AFAIK, "Ben" was another early name for the IJ Navy Zero. "Oscar" were reported by early encounters in CBI Theater as a separate fighter "Jim." Until later intelligence ID'ed both "Oscars" and "Jims" as the same Nakajima Army Type 1 fighter.

ThomasP · Oct 27, 2020

Hey guys,

re:"(rei sen = Zero sen)"

With the understanding that I do not speak or read Japanese, I thought that the meaning of the words "rei sen" was literally "model new" or maybe "type new", with "rei" = type or model and "sen" = new. In spoken English it would be "new model" or "new type". Maybe the word "sen" can also mean 0 in Japanese usage? Does anyone know for sure?

P-39 Expert · Oct 27, 2020

jmcalli2 said:
Seems to me you're cherry picking your test results.
The fastest P-39 was the N, clocked at 398.5. A graph in wwiiaircraftperformance shows a P-39Q-30 without wing guns at 410mph at 10000' and 400mph at 16000'.
The fastest A6M couldn't hit 360, even the versions with increased HP.
And the A6M had a very hard time maneuvering above 300; those big ailerons were very hard to move.

The problem the P-39 had in the PTO was in large part due to the USAAC being at the bottom of the learning curve in tactics and maintenance while the Japanese were experienced in both. Agree, they had experience in China.
The Japanese had their logistics worked out, the USAAC did not. True, AAF had a hard time maintaining their planes. They got better, but it was rough in 1942.
The P-39s were often sent up to intercept Japanese bombers flying at 20,000 ft. It would take 6-8 minutes for a P-39 to reach them, by which time the bombers would be gone. Meanwhile, the climbing P-39s would be bounced by A6Ms.
Try reading P-39/P-400 vs A6M3 Zero New Guinea 1942 by Michael John Claringbould. It has some good combat accounts, some of which will say the P-39 and A6M were close in speed, some were the P-39 was faster, likely due to acceleration being close for the two aircraft. But the main reason to read the book is the in-depth look at combat records; the P-39 and A6M were even in the win-loss stats. That surprised me. Especially with pilot quality, the Japanese were experienced carrier pilots, the Americans just out of flying school. Some didn't even have any fighter training. Smart kids, they learned fast.

As for the A6M having a service ceiling of 35-38,000 ft, that didn't mean that it fought at that height. Right, service ceiling was largely a test number achieved under test conditions.
Service ceiling means the rate of climb is 100 feet/minute. Better measure is combat ceiling where it would no longer climb at 1000fpm. Hard to climb at less than 1000fpm in combat.
A6M performance fell off at 20-22,000 ft, like the P-39's did at 18,000 ft. That 2-4,000 ft made a difference. With a little less weight (300lbs or so) P-39 would climb with a Zero.

Also recommended is this December 1942 comparison report between the A6M-2 and various US aircraft including the P-39D: http://www.wwiiaircraftperformance.org/japan/intelsum85-dec42.pdf

fubar57 · Oct 27, 2020

How fast did the P-39 climb with 300lbs of less weight?

XBe02Drvr · Oct 27, 2020

ThomasP said:
Does anyone know for sure?

According to Google Translate, "Zero fighter" translates to "Reisen" in contemporary Japanese. Oddly enough, it doesn't come up the same translating in the opposite direction. Contemporary Japanese has many usage variations from "classic" prewar Japanese.
My mother, born in Shizuoka in 1924 and brought to US in 1933, had a reunion with some of her Japanese elementary school classmates before she died. What remained of her prewar Japanese was the subject of some amusement for her former classmates.

Ivan1GFP · Oct 27, 2020

ThomasP said:
Hey guys,

re:"(rei sen = Zero sen)"

With the understanding that I do not speak or read Japanese, I thought that the meaning of the words "rei sen" was literally "model new" or maybe "type new", with "rei" = type or model and "sen" = new. In spoken English it would be "new model" or "new type". Maybe the word "sen" can also mean 0 in Japanese usage? Does anyone know for sure?

Hello ThomasP,

The full name should be:
Rei Shiki Kanjo Sentohki
or
Zero Type Carrier Fighter

but just like everyone else, the Japanese had a tendency to abbreviate, so we get Rei Sen.
Now keep in mind I don't speak or read Japanese either.
I am sure there are some Japanese speakers who can do better.

- Ivan.

XP-39 II - The Groundhog Day Thread

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