ZERO-SEN Model 21 Performance: Unraveling Conflicting Data

[Jan Masterson]

hello everyone,

i was surfing on the web and i found a very interisting article on http://www.j-aircraft.com about the multiple and conlifcting data available actually about Zero's maximum speed.

It vary from 316 mph to 345 mph.

The author, Richard L. Dunn, demonstrate why most datas are false, even the most common "331 mpph", and show that there's enough evidence to conclude that the maximum speed of 345 mph for the Zero A6M2 model 21 is highly credible and so probably the correct one among all the others.

Here's a link to the article:
ZERO-SEN Model 21 Performance: Unraveling Conflicting Data

As a complement, one more evidence in favor of the 345mph max speed:

A technical intelligence report dated 7 Dec 43 issued by the Joint Intelligence Agency Reception Center gives performance figures for the "Navy 0 Mk 1 ZEKE with Sakae 12...engine installed" stating the maximum true airspeed is 345 m.p.h. It says "These results have been calculated from all available data and are considered to be substantially accurate." Note this report is more than a year after the Akutan Zero was flight tested.

In 1940 the pilot of a Type 99 carrier bomber was captured in China. He was questioned about the performance of the then new Zero fighter. He stated its maximum speed was 300 knots. This equates to 345 statute m.p.h.

RLD

May you read it and come back to write your own conclusion.

Regards,

Jan

[Jim Oxley]

I've always tended to go with the man who flew the aircraft for' several years' as the best source of information ie Saburo Sakai. After all, his life depended on the accuracy of his knowledge of what the aircraft could, and could not, do.

If he says 345mph that's good enough for me.

[Graham Boak]

Referring specifically to the captured Val pilot's comment: any statement with a nice round number in it must be taken with a pinch of salt. Particularly as it does not come from a source with direct experience.

I'd certainly agree about the "highly credible" nature of the 345mph figure. This is comparable to contemporary fighters with the same power: if anything somewhat less than might be expected from 1941. It is below the Spitfire and the 109, but above the Hurricane and about level with the P-40. 331mph is only what the Hurricane could (at best) achieve on less power in 1938. A range of 331-345 is about what might be expected from "natural" variation from one aircraft (and engine!) to another, and 316 would not be unexpected from a used aircraft in a poor state.

I don't know if Sakai ever quoted any specific number. It is worth pointing out that this maximum speed was only obtained at the optimum pressure altitude, and at this altitude the pilot would be seeing Indicated Air Speed which is lower than the True Air Speed. So the quoted calculated max. speeds were not numbers that pilots actually needed to use - though I suspect they did know them, or could carry out the necessary conversion from what they did see.