F4F Wildcat versus P-40E Tomahawk

[renrich]

I believe that I will not ignore the statement of a career USN pilot, squadron commander, aeronautical engineer, test pilot and combat pilot. There are imnumerable examples in WW2 where AC with a Vmax disadvantage were more effective in combat than those with higher Vmaxs, the most obvious of those being the Zero versus P40s and Spitfires. I don't have much data regarding ACM between Spitfires and Zeros but in reading the posts on this forum, I gather the Spitfire did not enjoy any marked statistical advantage over the Zero. I know these are different times and I cannot discuss this with any veracity but the FA18 is supposed to be a premier ACM fighter. It is substantially slower than it's predecessor and slower than most of the "enemy" fighters it would be likely to encounter. Apparently a Vmax advantage is no longer much of an "advantage." To me, going back to the P40E V FM2 question, a 40 mph Vmax advantage could be tactically significant but a 1000 FPM climb advantage for the Wildcat could be also, as well as an AC less susceptible to battle damage and one having a significant advantage in turning. It all goes back to my original statement which is that the advantage the P40 might have is not necessarily clear. Here is a quote from Eric Brown on his opinion of a fight between two fighters with somewhat similar performance characteristics as our two. The Fw190A4 had a speed advantage over the F6F3 but was at a disadvatage in climb. "This was a contest so finely balanced that the skill of the pilot would probably be the deciding factor." In a contest between a F6F3 V BF109G6, the German had both a speed and climb advantage. "The Hellcat had a distinct advantage over the BF but would not be able to overcome it without a lot of pilot sweat." Finally, BF109F V Wildcat, "The BF was 60 mph faster than the Wildcat and although the Wildcat was superior as a dogfighter, the initiative lay with the BF because of superior performance. At low altitudes the BF had the advantage but not by much." The significance of this is that I don't believe the record indicates the P40 was anywhere near as good as the BF in ACM. LOL, I know, Eric Brown may not have much credibility with me or you!

[HoHun]

Hi Renrich,

>I believe that I will not ignore the statement of a career USN pilot, squadron commander, aeronautical engineer, test pilot and combat pilot.

But you're happily ignoring the statement of a career FAA pilot, test pilot and combat pilot along with the statement of a knighted aerodynamicist, president of the Royal Aeronautical Society, director of the RAE Farnborough? :-)

>There are imnumerable examples in WW2 where AC with a Vmax disadvantage were more effective in combat than those with higher Vmaxs

Don't fall into the trap of thinking that the success in a certain campaign means that this success is owed to the quality of the aircraft. It can as easily have been the men as the machines - and with better machines, they might have gotten even better results.

That's why Robert Shaw, author of "Fighter Combat - Tactics and Maneuvering", relied on engineering analysis of fighter performance data. (In case you do not know the book: It has been called the fighter pilots' bible - by fighter pilots.)

>I know these are different times

Indeed, and just how many fractions of a Mach a modern jet fighter can achieve above or below Mach 2 is not relevant to our discussion.

However, the idea of looking at a general trend in fighter design is in fact a good one - and you will notice that the universal trend in WW2 was towards larger, heavier, less manoeuvrable, but faster fighters. Obviously, the air forces that procured the fighters had decided the speed was the most important criterion of them all.

>To me, going back to the P40E V FM2 question, a 40 mph Vmax advantage could be tactically significant but a 1000 FPM climb advantage for the Wildcat could be also

Hm, here a couple of graphs showing P-40E vs. FM-2 performance. I used 7431 lbs as the FM-2 take-off weight, and the engine power graph for MIL (no water injection) from the FM-2 manual. I also assumed the FM-2 to have slightly better aerodynamics than the F4F due to the relocation of the oil cooler. If you have different data, I could plug that into the calculation, too.

Regards,

Henning (HoHun)

[renrich]

I have Shaw's book and have read it. I don't understand why a difference of Mach 2.4 and 1.8 is not significant. My source says that the P40 E had a rate of climb at sea level of 2000 fpm and the FM2's was more than 3000 fpm. I don't understand why that is not significant. As a matter of act, at mil power my source shows the Vmax of the P40E at 20000 feet to be 330 MPH where as the FM2 at 20000 feet has a Vmax of 320 mph. I don't regard that as tactically significant. I don't do calculations. I gave that up a long time ago. As a matter of fact, I seem to remember in Shaw's book that he showed situations where angles tactics could be used to defeat energy tactics.

[HoHun]

Hi Renrich,

>I don't understand why a difference of Mach 2.4 and 1.8 is not significant.

What I said is that it is "not relevant to our discussion". Both the technology and the order of magnitude of the characteristic values in jet combat have changed so much that it is difficult to transfer the concepts to WW2 air combat.

>My source says that the P40 E had a rate of climb at sea level of 2000 fpm and the FM2's was more than 3000 fpm.

Quite possible - but you have to take the specific operating conditions into account. As Koolkitty pointed out earlier in this thread, the P-40E was rated for 56" Hg:

http://www.raafwarbirds.org.au/targe...fs/1710-39.pdf

If you look at the graphs I provided for the 44" Hg MIL power setting, you'll see that it results in a climb rate close to the 2000 fpm you quote. However, this was not the highest possible power setting for the P-40E.

Regarding the FM-2, my calculations show a 2900 fpm climb rate already. However, the graphs I posted are for the R-1820-56 without water injection, and water injection would give the FM-2 an increased climb rate below 3000 ft - probably even greater than the 3000 rpm you quoted. I don't have any data for the R-1820-56W with water injection, though.

>As a matter of act, at mil power my source shows the Vmax of the P40E at 20000 feet to be 330 MPH where as the FM2 at 20000 feet has a Vmax of 320 mph.

Well, quite possible - data tends to vary between different sources. The combination of high altitude and high speed doesn't seem to fit the FM-2's engine characteristics really well, though. What's your source for the FM-2 data?

>As a matter of fact, I seem to remember in Shaw's book that he showed situations where angles tactics could be used to defeat energy tactics.

Speed is just a tool, it doesn't automatically win a dogfight for you.

Regards,

Henning (HoHun)

[renrich]

Actually, in looking at the chronology of the two Ac, a comparison of the F4F3 and P40E makes more sense. The performance of the F4F3 is pretty similar to the FM2. The performance charts I have are based on military power for both.

[HoHun]

Hi Renrich,

>Actually, in looking at the chronology of the two Ac, a comparison of the F4F3 and P40E makes more sense.

OK, here it is. Do you think the A6M2 is the most representative Zero variant to compare these two against?

Regards,

Henning (HoHun)

[renrich]

I think the A6M2 is contemporaneous with the two. I do not believe the A6M2 ever had WEP. Are your graphs based on your calculations or are they taken from some other source?

[HoHun]

Hi Renrich,

>I think the A6M2 is contemporaneous with the two. I do not believe the A6M2 ever had WEP. Are your graphs based on your calculations or are they taken from some other source?

My graphs always rely on other sources, often a collection of sources that have been compared and assessed by running the calculations for each of them and noting the inconsistencies and contradictions, and deciding on the most realistic parameters to use for the 'final' calculation.

In the case of the A6M2, you're right that it is usually portrayed as not having any WEP capability. However, the Navy's own tactical intelligence sheets list the engine of the A6M2 with MIL and WEP boost levels:

TAIC 1944 p. 851
Sakae model 12
Take-off: 925 hp/2550 rpm/39.8" SL
WEP: 925 hp/2550 rpm/39.8" SL
WEP: 1010 hp/2550 rpm/39.8" 11000*
MIL: 820 hp/2500 rpm/35.8" SL
MIL: 935 hp/2500 rpm/35.8" 13800 ft

Additionally, Richard Dunn has also mentioned "overboost" in his article on A6M performance: Zero Model 21 Performance: Unraveling Conflicting Data (Not that I agree with his conclusion, but the article is interesting nevertheless.)

However, the TAIC engine data seems a bit suspect to me at least for the Sakae 21 and 31A data, and I'm not sure it's entirely realistic especially for the latter engine. If you're aware of any other sources, please let me know :-)

Regards,

Henning (HoHun)

[renrich]

I have a source which published the test results in abbreviated form for the Attu A6M2 versus US fighters and a later model 52 Zero but there are no exact technical data. The comparison for the Wildcat V Zero is pretty complete but the flyoff for the P40F is not because almost all of the AAF fighters broke down during the tests and could not achieve max performance. I have a fairly lengthy technical article on the Zero and I can find no mention of WEP on A6M2.

[kool kitty89]

It may just refer to it as "take-off" power instead of WEP. (as the rating is the same)

[HoHun]

Hi Renrich,

>I have a source which published the test results in abbreviated form for the Attu A6M2 versus US fighters and a later model 52 Zero but there are no exact technical data.

Sounds interesting! Is it available online somewhere?

>The comparison for the Wildcat V Zero is pretty complete but the flyoff for the P40F is not because almost all of the AAF fighters broke down during the tests and could not achieve max performance.

I think this must be Informal Intelligence Summary No. 85, which is available at Richard Dunn's site, I believe. Unfortunately, it has no information on the engine settings used for the A6M2, except that power is estimated at 900 HP @ 16000 ft, which as the speed graph shows is the high-speed figure (rated altitude increased by ram effect). If the TAIC engine data is correct, this is consistent with a lower boost level than what TAIC lists for MIL, meaning we should expect the A6M2 at the WEP settings to be faster than the No. 85 figures.

Richard Dunn notes in his abovementioned article that Intelligence Brief #3 (which I have not seen) gave the boost pressures as follows 35" Hg and 38" Hg: "U.S. notations 35 and 38 in. Hg actually reflect Japanese ratings of +150mm/35.4 in. Hg and +250mm/37.8 in. Hg)". On checking his conversion, that does not seem to be correct as +250 mm Hg amounts to 39.8" Hg according to my calculation, which is the figure also given in the TAIC report.

Jim Rearden's "Koga's Zero" shows a photograph of the boost gauge of the A6M2 recovered on the Aleutians, and it has a marked arch from 0 to +25, which would be consistent with Dunn's "250 mm Hg" figure (presumably from intelligence brief #3) and the 1944 TAIC data sheet.

So the question remains whether the data given in Intelligence Summary No. 85 was for +150 mm Hg or for +250 mm Hg. With the later TAIC data being consistent with No. 85, the high full throttle height of 16000 ft mentioned in No. 85 suggests that the speed figures were really achieved at just +150 mm Hg. Whatever one would call the +250 mm Hg setting, an A6M2 using it would be faster than the No. 85 figures

Regards,

Henning (HoHun)

[renrich]

The test summaries for the Attu and model 52 Zeros are in "The Great Book of WW2 Airplanes" in the section about the Zero. I have not seen them online. I was surprised at how well the FM2 compared with the Model 52. The earlier test with the A6M2 was against an F4F4 and was not nearly as even. The test with the P40F was not completed because the engine in the P40F could not get full power.The A6M2 had a Sakae 12 engine. The model 52 had a Sakae 21 with takeoff power of 1130 HP.

[HoHun]

Hi Renrich,

>The test summaries for the Attu and model 52 Zeros are in "The Great Book of WW2 Airplanes" in the section about the Zero. I have not seen them online.

I guess the A6M5 material is from the reports uploaded here: http://home.att.net/~historyworld/TAICzero.pdf

>The model 52 had a Sakae 21 with takeoff power of 1130 HP.

According to the linked file above, both the examples tested by the US Navy and the USAAF had a Sakae 31A with 1120 HP take-off power. Not much of a difference, I'll admit - the Sakae 31A only differed noticably in its high supercharger gear.

The Navy A6M5, which was the heavier example, had the higher top speed - 335 mph @ 18000 ft. The Air Force noted poor aerodynamic condition, smoke and rough running for their example. Their 326 mph were achieved at 19400 ft though, and they give the engine conditions as 42" Hg, 2750 rpm.

All considered, this looks more like the Sakae 21 ata than the Sakae 31A data since the latter ran at 2800 rpm in WEP, 2700 rpm in MIL, and had a full throttle height of 20400 ft (static) in WEP, 21700 ft in MIL. You book might be right regarding the engine :-)

Regards,

Henning (HoHun)

[renrich]

The book says the Sakae 21 is rated at 1130 hp takeoff, 1100 HP at 2850 M, and 980 HP at 6000 M. The model 52a has Vmax at 6000M of 302 knots, 343mph. Time to climb to 6000 M is 7 min 1 sec.

[HoHun]

Hi Renrich,

>The book says the Sakae 21 is rated at 1130 hp takeoff, 1100 HP at 2850 M, and 980 HP at 6000 M. The model 52a has Vmax at 6000M of 302 knots, 343mph. Time to climb to 6000 M is 7 min 1 sec.

The quoted ratings seem to be close to the ratings the TAIC quotes for MIL power (see below). However, either the full throttle height at full speed would be higher than 6000 m, or the engine data is for power with dynamic pressure (in high-speed flight), meaning it would be decidedly different from the TAIC data.

Here is an interesting article on the A6M3 Model 32:

http://skyraider.allaboutwarfare.com...n_Analysis.pdf

One interesting thing is the manifold pressure gauge which shows a marked arch ending at +250 mm boost. This is the same as on the A6M2, and less than the TAIC engine data ascribes to the A6M3. The TAIC data for the Sakae 21 is:

Sakae model 21, TAIC 1944 p. 852
Take-off 1115 hp/2750 rpm/41.7" SL
WEP 1115 hp/2750 rpm/41.7" SL
WEP 1180 hp/2750 rpm/41.7" 7500*
WEP 1040 hp/2750 rpm/41.7" 18000*
MIL 995 hp/2700 rpm/37.8" SL
MIL 1085 hp/2700 rpm/37.8" 9350 ft
MIL 965 hp/2700 rpm/37.8" 19700 ft

41.7" Hg converts to +300 mm Hg, so if we assume that the marked arch indicates the boost range up to the war emergency rating, the A6M3 at least would have to be considered to have a lower maximum power than this TAIC data.

The article I linked above shows that there is a supercharger control on the throttle quadrant, and while the scan is not very good, I think I can make it out in the cockpit shot too, which would verify that the picture is not from an A6M2 cockpit (which would be misleading).

Interestingly, the article also identifies one button in the cockpit as "emergency power booster", which might answer one of our open questions.

>The model 52a has Vmax at 6000M of 302 knots, 343mph. Time to climb to 6000 M is 7 min 1 sec.

Is the weight for the specific aircraft given? I get about 6 min for 6 km if I use MIL power from the TAIC data with the weight of the heavier of the two tested A6M5 examples, 6096 lbs.

Regards,

Henning (HoHun)