P-39 or P-40 for rest of war?

Nikademus said:

If not already posted somewhere in this thread, this article on the captured A6M2 model 21 might offer additional insights.

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Interesting,

Most of what i've read says different and even Sabaru Saki is quoted as saying the top speed of the Model 21 was 309mph but what do pilots know.

i actually think people confuse Model 21 and Sakae 21 and end up siting them as the same aircraft.

There is a lot of obscurity with the US tests because they tested with higher octane gas which allows for higher boost pressures.
Thats what the 44-1 summary is about.

Furthermore, only the Sakae 31 engine had water-methanol injection for anti-detonation purposes. I suppose its possible that the A6M3 could've been retrofitted with these engines but we are talking at a time after the development of the A6m5c.

I still haven't found anything that supports a higher output than whats already been published and reiterated over several other sources.

www.warbirdsresourcegroup.org - Imperial Japanese Aviation Resource Center - Mitsubishi A6M Zero-Sen

I still haven't seen anything else to suggest otherwise.

billswagger said:

Interesting,

Most of what i've read says different and even Sabaru Saki is quoted as saying the top speed of the Model 21 was 309mph but what do pilots know.

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That paper is deinitely correct that Sakai spoke as quoted in the source it refers to, "Samurai", where he said (it's pg 43 in my edition rather than 48 as the article says) "Under normal full power conditions the Zero was capable of 275kts [~316mph] and, when overboosted for short emergencies could reach its maximum speed of around 300kts [~345mph]". It's clear from the context he was speaking of the Model 21 (discussing preparation for war during 1941). That is just what he said as reported in that book, but if you have a source where he quoted a much lower speed, I think you'd have to cite it specifically.

Other sources beside that article also quote US pilots who had met the Zero in combat as saying the Akutan test results foir speed of the Zero seemed too low to them. And in general, that article gives all its sources, Rick Dunn is a reliable expert on the topic, and I don't think just saying 'that's not what I've read' is a very effective comeback to his conclusion, with all due respect.

Joe

Thats a very popular memoir but its also received a lot of criticism. http://www.warbirdforum.com/samurai.htm
There are some stories described in the book that never happened, and the author has been scrutinized for his mishandling of the facts. I would take that quote about the zero with a grain of salt.

The zero reaching 345mph in level flight sounds like a misquote considering max dive speed nears 350mph depending on altitude.

In another interview with Sakai, he mentions that the Zero gets very difficult to fly above 250 mph.
http://www.warbirdforum.com/sakai.htm
There's even modern A6M3 pilots at airshows who fly using original parts. They confirm that flight above 250mph causes the controls to get really stiff and unresponsive.

With that said, i only question speed figures on the basis that higher boost pressures would be necessary to obtain them. I also question the context they are reported under because the speed figures quoted are similar to other model numbers, obscure US military testing, or numbers that lack adjustment from compressibility. If higher boost pressures were obtained there should be published data on these settings, right? Published data also says water methanol (WEP) was not used on those engines. So the fuzziness for me is just determining what the max boost pressures were.


Bill

billswagger said:

Thats a very popular memoir but its also received a lot of criticism. http://www.warbirdforum.com/samurai.htm
There are some stories described in the book that never happened, and the author has been scrutinized for his mishandling of the facts. I would take that quote about the zero with a grain of salt.

The zero reaching 345mph in level flight sounds like a misquote considering max dive speed nears 350mph depending on altitude.
l

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I know all about that book, am probably one of the ones criticzing it on the other thread, or have anyway pointed out specific errors in other threads on this forum. I'm simply pointing out here that Dunn is correctly quoting the book. You OTOH said Sakai was elsewhere quoted saying the Zero's max speed was 309mph: where?

Dunn is also quoting a number of sources in that article all supporting his general conclusion that the Zero's speed was *probably* greater than what was shown in the Akutan Zero test.

Joe

Agree with JoeB on this one. I garnered a similar impression from reading Lundstrom regarding the Zero's real world speed as well as from Shores' accounts. The J-aircraft article seems solid in it's conclusions and well cites it's bibliography.

I guess for me, its not really enough until i see a document that specifies the actual boost pressures that were attainable. The rest is open to interpretation, and/or misinterpretation.
It appears some of what Dunn is refering to can also be found on mike williams site, and that's where i garner most of my position from. I have a hard time reading into obscurities in a time when propaganda was rampant and the Japanese would have everyone believe the Zero was unbeatable. That's just my opinion on the matter.
Its more a passion for the subject, and the reason why i'd like to know more about the boost pressures obtained by the aircraft.

http://www.wwiiaircraftperformance.org/japan/a6m2-oct2342.pdf
Most people just look at the speed figures and move on, but there are couple things that pop out at me here. One is the lack of correction for compressibility, and standard conditions, which means these figures are going to be a little higher than actual speeds.

The other thing this report says is that the plane had an automatic boost regulator that permitted a max of 35" .

So tell me, how do you run higher boost pressures when it has a regulator to keep it from overboosting?
In fact, its entirely possible that the 35" is a conversion error on the part of the USN and that max boost was obtained.

http://www.wwiiaircraftperformance.org/japan/p5016.pdf
The more i look at this, the more i agree it is bogus.
It shows 2050rpm at 120mm pressure, being at max throttle position. (120mm = ~35")
Of course pilots in combat are going to report higher operational speeds than whats found here. The top speed found was 289mph at 15,000ft at a boost of 2cm,(~31" max throttle)
I would think not only would more speed be obtainable, but higher boost pressures would show with the proper RPMs.

This is why i would like to see a document that specifies which boost pressures were used outside of what is already known. (200-300mm)
Requoting what's already been determined or getting someone else's take on it doesn't offer up any more incite to what boost pressures were actually achieved.

BTW, the quote i am searching for, where i read the 309mph figure from Sakai, i don't agree with and probably needs the altitude to put it in better context.