XP-39 II - The Groundhog Day Thread

P-39 Expert said:

In 1943 there aren't going to be any FW190As at 30000'. No F4Fs. Not many Zeros or Oscars. I agree that there were not many P-39Ns cruising at 30000' but the capability was there.

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P-39 Expert said:

Initial combat dates: P-38 November 1942, Corsair Feb 1943, P-47 May 1943, Hellcat August 1943, Merlin P-51 December 1943. P-38 barely made combat in 1942 a full year after the war started. P-39, P-40 and F4F were all that was available in 1942.

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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.

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.

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Cherry-picking data to suit an argument? Surely not!

It's tiresome to beat a dead horse, or to feed a troll. I vote on quitting both endeavors.

The speed test you showed in post 958 is at 13,000 feet. At wide open throttle, the P-39 went 358 mph on 1170 hp. Figure cruise at maybe 75% of that, or 877 hp. Your chart shows 321.5 mph at 850 hp. According to wwiaircraftperformance, the P-39D climbed at 1,880 fpm at 15,000 feet at wide open throttle.

Figure an A6M3 since we are in 1943.

According to wwiaircraftperformance, they operated their Zero at 36" MAP and 2,400 rpm! The Sakae 21 engine made 1,130 hp at 2,750 rpm for takeoff. So, they only ran it at about 900 hp or less out of the possible 1,130 to get their performance numbers. Think a Japanese Naval pilot would do that in combat? I doubt it. At that reduced power, reduced even further by altitude, the A6M3 climbed at 2,180 fpm at 15,000 feet. Compare that to the P-39D above (1,880 fpm). They only tested the Zero at 36" MAP @ 2,400 rpm, where it went 310 mph at 9,300 feet. I don't know why they only tested at 36" MAP (which is only about 3" of boost). The A6M3 is often quoted at 4,500 fpm climb, but that's at full power and 2,700 rated rpm (not 2,750 for takeoff only), and not restricted to 36" MAP.

They deliberately ran the zero at low power as far as I can see. WAY low power.

To me, it as advantage Zero, big time. I think the P-39 was pretty competitive below 10,000 feet.

Hello P-39 "Expert",

P-39 Expert said:

Like what?
.....
And plenty of test pilots and combat pilots report that it handled just fine. P-39 was a perfectly good handling airplane that served the country well when there wasn't anything else except the P-40 and F4F.

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If you have to ask what unsubstantiated claims Bell made, then you need to do a lot more reading.
.....
Perfectly good handling as long as it was loaded correctly.... If not, then not so much.

P-39 Expert said:

I have no idea, but there were sure a lot of captured Zeros tested. And after the war Zero pilots who were interviewed substantiated the results of those tests. The Zero was many things, but fast wasn't one of them.

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There are actually very few reports with a fully functional A6M of any version tested.
I never claimed the A6M2 was all that fast. I am saying your repetitive claim that the early P-39 had a 40 MPH speed advantage is total garbage.

P-39 Expert said:

More like around 14000' with ram, and they were able to hold that speed up to around 16000'. You talk like they stopped running when they reached their critical altitude.

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Then performance reports must be lying and the people testing the P-39D must have been really stupid to be testing at only 13,000 feet. I think not. Putting a supercharger intake into a low pressure area isn't going to make it work particularly well.

P-39 Expert said:

And those tanks were dropped for combat, weren't they.

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....and that would be a really bad time to find that your enemy has a significant altitude advantage over you because you couldn't climb worth anything with the drop tank.

P-39 Expert said:

Initial combat dates: P-38 November 1942, Corsair Feb 1943, P-47 May 1943, Hellcat August 1943, Merlin P-51 December 1943. P-38 barely made combat in 1942 a full year after the war started. P-39, P-40 and F4F were all that was available in 1942.

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I was replying to your comment about numerous axis fighters that were not available in 1943 when they were available in 1942 and being replaced with newer versions by 1943.

P-39 Expert said:

Returning from a mission where it had to drop the tank it would have 120gal less a 20 minute landing reserve (10gal) less 15 minute combat reserve (18gal at 25000') leaving 92gal left using 48gal/hr at 30000' resulting in 1.92hr at 305mphTAS or 585mi after reserves. A radar alerted interception mission with no drop tank and 120gal internal would be reduced by the takeoff allowance of 16gal, 15min combat allowance at 30000' of 14gal and a landing reserve of 10gal resulting in 80gal useable at 48gph or 1.7hours patrol time. Plenty of time to intercept a bombing raid.

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You are conveniently forgetting a few things here.
First, you can't magically gain altitude without expending fuel. How did you get to 30,000 feet?
Second, it would be amazingly convenient to retain ALL (remember that "All") internal fuel when heading home.
Third, Are you forgetting that the Reserve tank is used for Take-Off?

P-39 Expert said:

Why couldn't it fight there? All it had to do was be above the enemy and dive on him.

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You are assuming that 30,000 feet puts you above the enemy. What if your opponent is there too?

- Ivan.

Hello GregP,

Which Zero report are you reading from?

It sounds like it is from the A6M2 captured by the AVG, beaten to crap when it was transported to the USA and then rebuilt by Curtiss to fly in 1943. After its ocean voyage, it never was in good shape again and the reason the RPM was so low was that IIRC Curtiss never figured out what the propeller pitch range was supposed to be.

- Ivan.

glennasher said:

It's tiresome to beat a dead horse, or to feed a troll. I vote on quitting both endeavors.

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I finally broke out the Pear Schnapps. Makes it easier.

I need to start drinking again

I never quit...

A6M3 report.

The closest U.S. engine to the Sakae 21 (1,687 cubic inches) is the Pratt & Whitney R-1830-S1C-G (1,830 cubic inches). It produces 1,200 hp at 2,700 rpm and 48" MAP. It likely makes the 1,200 hp instead of 1,130 hp of the Sakae due to more displacement ... but there is no way the Sakae 21 will make rated power at only 2,400 rpm and only 36" MAP. It just won't move enough air/fuel to do that.

I have several reference that state the Sakae 21 made its power at 2,700 rpm ... not 2,400 rpm, but none that specify the manifold pressure. My estimate would be around 48" MAP.

Hello GregP,

EB-201, right? That was the A6M3 Model 32 "Hap" rebuilt from a collection of wrecks at Eagle Farm.

The reality of the Sakae 21 performance may surprise you a bit.
It wasn't quite as much of an improvement over the Sakae 12 as you might be thinking.
The Sakae 21 wasn't that much more powerful than the Sakae 12. It just had a greater critical altitude because of its two speed supercharger instead of the single speed supercharger on the earlier engine.

I believe their Take-Off is equivalent to War Emergency and that is how TAIC evaluated it even though Japanese never listed in their manuals as anything but Take-Off and never listed it as something that could be used at altitude though evidence is that some pilots obviously did this.
Rated is probably equivalent to what we consider "Military Power".
Normal Power is most likely equivalent to "Maximum Continuous"
Boost pressures are mm Hg over ambient at Sea Level (760 mm Hg).

Sakae 12:
Take-Off
+250 mm Hg @ 2550 RPM - 940 HP

Rated Power - Sea Level
+150 mm Hg @ 2500 RPM - 830 HP

Critical Altitude 4200 Meters - Single Stage, Single Speed.
Rated Power - 4200 Meters
+150 mm Hg @ 2500 RPM - 950 HP

Normal Power
+50 mm Hg @ 2350 RPM -??? HP.

.......

Sakae 21
Take-Off
+300 mm Hg @ 2750 RPM - 1130 HP

Rated Power - Sea Level (Low Blower)
+200 mm Hg @ 2700 RPM - 1010 HP

Rated Power - Sea Level (High Blower) - Yes, this is listed in the manual.
+200 mm Hg @ 2700 RPM - 810 HP

Critical Altitude - Low Blower -2850 Meters
Rated Power Critical Altitude Low Blower
+200 mm Hg @ 2700 RPM - 1100 HP

Critical Altitude - High Blower - 6000 Meters
Rated Power Critical Altitude High Blower
+200 mm Hg @ 2700 RPM - 980 HP

Normal Power
+75 mm Hg @ 2500 RPM - ??? HP

.......

Now here is a rather screwy thing and probably a reason the folks at Eagle Farm and others got a bit confused:
The manifold pressure gauge apparently was the same on aircraft equipped with the Sakae 12 and Sakae 21.
Please see attached image which is a crop from NASM A6M5 panel image.
Note that it reads from -450 mm to +250 mm which is just fine for a Sakae 12 engine.
Who-da thunk they would use the SAME gauge for aircraft with a Sakae 21 that can get to +300 mm at Take-Off???

To save some calculation time: (GregP, I already know you know this, but others may not.)
+50 mm == 31.89 inches Hg
+75 mm == 32.87 inches Hg
+150 mm == 35.83 inches Hg
+ 200 mm == 37.80 inches Hg
+250 mm == 39.76 inches Hg
+300 mm == 41.73 inches Hg

- Ivan.

GrauGeist said:

I never quit...

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Me either but after reading this,

"P-38 barely made combat in 1942 a full year after the war started"

Im gonna drink a bit more

rochie said:

Me either but after reading this,

"P-38 barely made combat in 1942 a full year after the war started"

Im gonna drink a bit more

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What, the war started in 1942???

Now I'm really getting scared.

I like this one...

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.

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

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?

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I'm probably wrong but as far as I remember "Zero" was what most Navy/Marine pilots called them, "Zeke" seemed more of an AAF designation. Forum experts feel free to correct me.

Thanks!

Every Japanese fighter was a Zero (at least until sometime in 1942)...saying that with tongue slightly in cheek, but only slightly.

Note that the A6M had 2 reporting names: Zeke and Hamp,

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