The Zero's Maneuverability (2 Viewers)

Holtzauge said:

That is really a strawman argument: I never said he read off 300 knots on his ASI: What I wrote was : "Did he actually read off an IAS corresponding to 290 or 295 knots and rounded this off to 300?"

And Sakai saying "about 300 knots" still sounds very much of a ballpark number and not something one would tune a simulation model based on. At least not in my book.

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I can't comment as to the accuracy of that quote. At one point I believed it to be overly optimistic but as I read more, I am finding that his claim is quite plausible in the context of other evidence.

Holtzauge said:

No torque curves needed: I have an original Japanese chart for the Sakae 12 where I can read off power for different boosts from -350 to +250 mm in the 1700-2550 rpm range, and the Japanese +150 mm 2500 rpm setting generates a little less power than the US test at +35" 2550-2600 rpm, hence the slightly lower speed (330 mph) with that setting in my estimate.

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b
US test reports seem to always quote RPM figures in the 2500 - 2550 RPM range. You are stating that the Japanese chart gives a power reading for +129 mm at 2600 RPM for a Sakae 12 engine? That would be interesting.
If the +150 mm boost setting at 2500 RPM is giving 330 MPH in a bent bird then what do you suppose +250 mm and 2550 RPM would be giving on a non-bent bird?

Holtzauge said:

You seem to miss my point: I'm saying that the Japanese changed the pitch range to improve the Zero's range at the cost of performance (trading high speed and high climb rate for long range). So the fact that this seems to be the case with many of the wrecks found actually bolsters my point that the low revs mentioned in US evaluations before they changed the pitch range was due to the Japanese employing this setting on a wider scale to get range, and not due to the engine in the US Wright Field test of the A6M2 being worn out.

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I believe this is a poor argument for the following reasons:
1. At the "Normal" engine setting of 2350 RPM, A6M2 cruised at 316 MPH.
2. The long range missions to Guadalcanal were flown at very slow airspeeds on lean mixtures.
Assuming the same advance ratio, half the airspeed and half the RPM is awfully low, my guess is that it is too low to be practical.
3. One other point that is worth noting is that Koga's A6M2 had no need to be configured for any super long ranges if such a configuration was even possible. He was flying off a carrier where low speed acceleration off the carrier deck was certainly more important.

Ivan1GFP said:

I can't comment as to the accuracy of that quote. At one point I believed it to be overly optimistic but as I read more, I am finding that his claim is quite plausible in the context of other evidence.

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Well here we just have to agree to disagree: For me "about 300 knots" remains just that: An about number just as in a ballpark number.

Ivan1GFP said:

b
US test reports seem to always quote RPM figures in the 2500 - 2550 RPM range. You are stating that the Japanese chart gives a power reading for +129 mm at 2600 RPM for a Sakae 12 engine? That would be interesting.
If the +150 mm boost setting at 2500 RPM is giving 330 MPH in a bent bird then what do you suppose +250 mm and 2550 RPM would be giving on a non-bent bird?

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Yes. The chart goes up to 2550 and and this line drawn above the 2500 line in the chart is quite close, meaning that the engine was close to peak rpm's and would not be producing much more power at 2600.

Then about what the +250 mm and 2550 RPM would add: I already explained that with the Spitfire MkI chart I linked to in post #334: The extra 50 rpm's from 2500 move the FTH speed a little towards higher speeds, but this is only marginal adding just a few mph at the FTH. The main gain is at lower latitudes, not at the FTH. Just as the effects on the Spitfire MkI when going from 6.25 to 12 and ultimately +16 boost.

And I don't understand why you are so fixated with "bent birds"? Unless a rebuilt aircraft is put together in a very bad way the effects on performance would be minimal. But since you seem to think there are many mph to be had here, just what was "bent" and how many mph would "un-bending" these defects do? 1,2, 3 or 5 or 10 mph? Because if this was missed by the BuAer engineers in charge of the testing, they were not very good at their jobs were they?

Ivan1GFP said:

I believe this is a poor argument for the following reasons:
1. At the "Normal" engine setting of 2350 RPM, A6M2 cruised at 316 MPH.
2. The long range missions to Guadalcanal were flown at very slow airspeeds on lean mixtures.
Assuming the same advance ratio, half the airspeed and half the RPM is awfully low, my guess is that it is too low to be practical.
3. One other point that is worth noting is that Koga's A6M2 had no need to be configured for any super long ranges if such a configuration was even possible. He was flying off a carrier where low speed acceleration off the carrier deck was certainly more important.

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We have been so fixated with speeds so far in this thread, that we have forgotten to consider that the climb rates in the US tests tell a story as well: And if you look at the climb rates in those tests you can see that the engines were delivering according to specs since they measured a bit over 2700 fpm SL climb rate for the A6M2's in both those tests, which is just as expected looking at the power loading W/P. So this proves without a shadow of a doubt that there was nothing wrong with the engines and that that reason for the low revs they measured when testing initially was due to the propeller pitch setting being adjusted for range, and not performance.

Ivan1GFP said:

Just for context: In many flight tests, the specification is a maximum of 60 pounds of force on the stick. A real pilot may be able to apply more but that was how the aeroplane was tested.
Also worth noting is that in one of the reports, there is a comment that at 200 Knots, A6M2 would complete a 360 degree roll in 5.4 seconds. That may not be great performance for the time, but it is still over 60 degrees per second.

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We've been through stick forces before

tyrodtom said:

If he didn't or couldn't keep count of how many turns he made, it's just a guess.

What I find amazing is that the guy behind him would do 75-100 turns behind him before he finally decided it wasn't going to work.
It wouldn't be fatal for the German to reverse his turn, and that's probably how he broke off the combat.

Staying on one opponent so long, in the same airspace, while the Mustang pilot is on the radio trying get all his buddies to come help him, just doesn't seem smart, or likely.

You seem to have your own misunderstanding of basic facts.

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I am curious as to how long it would take to do 100 circles. Does anyone have any idea?
I believe it would take about 20 seconds to complete a circle. If so that's over 3 minutes at full power. Fuel becomes an issue. Also 3 minutes at high Gs must be very tiring.

If it takes 20 seconds to complete a circle, then it would take 33 minutes to complete 100.
Somebody check my math.
That's a long time at full power, and in one area.

Depends on what escort mission he was on , but just how much extra time did a Mustang have to go after the Luftwaffe ( as Doolittle told them to do) after escorting the bombers to the target, and was then released to search and destroy.

tyrodtom said:

If it takes 20 seconds to complete a circle, then it would take 33 minutes to complete 100.
Somebody check my math.
That's a long time at full power, and in one area.

Depends on what escort mission he was on , but just how much extra time did a Mustang have to go after the Luftwaffe ( as Doolittle told them to do) after escorting the bombers to the target, and was then released to search and destroy.

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Yes I missed a zero. Since 5 minutes at full power is the budget the P51 pilot isn't getting home