Qualities that made for a great aircraft that don't show up in performance stats.

[michael rauls]

I'll throw in my 2 cents worth. I think had the F6f not come along and we had only the Fm2 and later some Corsairs for carrier fighters we still would have won the Pacific war but it would have been more costly. How much more is hard to say but my guess is substantially so.
If you have a positive kill ratio with an oponent and you are massively out producing them then the outcome is inevitable. Heck if you are massively out producing an oponent and are exchanging one for one with them the outcome is still inevitable.
I think the F6F made a huge difference however being, at least in my mind, an exceptional airplane for alot of reasons as we've already discussed at length that don't nescesarily show up in performance stats.

 

[GrauGeist]

I'll throw in my 2 cents worth. I think had the F6f not come along and we had only the Fm2 and later some Corsairs for carrier fighters we still would have won the Pacific war but it would have been more costly. How much more is hard to say but my guess is substantially so.
If you have a positive kill ratio with an oponent and you are massively out producing them then the outcome is inevitable. Heck if you are massively out producing an oponent and are exchanging one for one with them the outcome is still inevitable.
I think the F6F made a huge difference however being, at least in my mind, an exceptional airplane for alot of reasons as we've already discussed at length that don't nescesarily show up in performance stats.

The F6F could have made it to production a bit sooner, but for delays.
An interesting side note, is that the USN was also looking at a navalized P-51 (several versions), but the F6F and F4U negated any serious consideration beyond testing.

An interesting "what if" to toss out there, would be if for some reason, Grumman didn't get the F6F into production (for whatever reason), the P-51 *may* have taken it's place. Key word here: *may have*.

The USN was looking at the P-51 early on, so if the F6F failed to deliver, there would have been time to maturate a navalized P-51 along the natural timeline.

Here's the USN's P-51 (41-37426) - not to be confused with the later P-51D or P-51H trials.

 

[Ivan1GFP]

What data supports the notion that the Hellcat was "draggier" than the Zeke? Was it really a "sleeker" aircraft as you say?

Rudimentary calculations are actually pretty simple in this case.
Determine the maximum speeds and altitudes (for air density) and Horsepower required to achieve that speed.
Horsepower can be converted to force * speed.
When speed is substituted, what you get is force required to drive that carcass through the air.
This ignores propeller efficiency, but it is reasonably fair since you are doing it for both aircraft and the numbers are only for comparison purposes rather than an actual measurement.

I guess it depends on you interpretation of what was a "typical" example of these two aircraft. Knowing that the Japanese were having severe difficulties with maintaining their aircraft as the war progressed, I feel it was quite representative of an average in-service A6M5 at the time of the tests (latter half of 1944) and IMHO indicative of what was being encountered in combat at this stage of the war. And while I'm in agreement that Hellcat under test may have been a very well-maintained example of the type, no one can argue that the US Navy wasn't vastly superior to the Japanese army or navy at keeping the performance of their aircraft as close as possible to factory numbers. If we add in the little improvements made by Grumman to the F6F along the way I am quite certain that the Hellcat was a true 400 mph airplane by the time that these tests were conducted.

If I recall correctly, the F6F-5 achieved 409 MPH and the A6M5 achieved 335 MPH.
Regardless of the results achieved by those two particular aircraft on that particular day, those numbers are about 25-30 MPH higher than the typically quoted speeds for the F6F-5 and about 15-20 MPH lower than the typically quoted speeds for the A6M5.

If the typical F6F-5 really were that fast, then one has to wonder why the new engine and propeller on the F6F-6 prototype did not improve speeds much at all (417 MPH) and why the Standard Aircraft Characteristics sheet lists maximum speed as 330 Kts.

- Ivan.

 

[XBe02Drvr]

What data supports the notion that the Hellcat was "draggier" than the Zeke? Was it really a "sleeker" aircraft as you say

The mark 8 eyeball provides all the data you need. It's bigger, it's fatter, it's heavier, its cowling is less streamlined and its larger, more powerful engine has way more cooling drag. The difference in frontal area is greater than the difference in horsepower. I'm sure you could dig up the data, but it would say the same thing.

I count FM-2s right in there with F4Fs. The basic difference between then was just the engine dash number

I think the change from a 14 cylinder Pratt to a 9 cylinder Wright might be a bit more than just a dash number change.
Cheers,
Wes

 

[DarrenW]

I worded it poorly.

I should have said it was not the determining factor. And probably not a major factor.

Point well taken. I believe that the same could be said of the Spitfire during the BoB. The Hurricane had more than an adequate performance to take on anything the Luftwaffe could throw at it, and with the use of RADAR it could always be expected to be in the right place at the right time. Add in the huge tactical blunders made by the German High Command along with the superiority of the average British pilot and there's no reason to ever imagine any other possible outcome of the battle.

 

[DarrenW]

Rudimentary calculations are actually pretty simple in this case.
Determine the maximum speeds and altitudes (for air density) and Horsepower required to achieve that speed.
Horsepower can be converted to force * speed.
When speed is substituted, what you get is force required to drive that carcass through the air.
This ignores propeller efficiency, but it is reasonably fair since you are doing it for both aircraft and the numbers are only for comparison purposes rather than an actual measurement.

Using that mentality the Zero was actually less streamlined than any mark of the Bf 109 and we all know how dirty of a bird it was.

The mark 8 eyeball provides all the data you need. It's bigger, it's fatter, it's heavier, its cowling is less streamlined and its larger, more powerful engine has way more cooling drag. The difference in frontal area is greater than the difference in horsepower. I'm sure you could dig up the data, but it would say the same thing.

Looks can be very deceiving when discussing aerodynamic drag. We are talking science here and not just casual observations. Do you have any wind tunnel tests to back up your claims of aerodynamic superiority? Just take a look at all the gaps and protuberances of the A6M cowling and you might change your mind.

And the size difference of the two aircraft wasn't a factor here because the power to weight ratios of the A6M5 and F6F-5 were nearly identical at sea level and as altitude rose the Hellcat's ability to maintain a greater percentage of it's horsepower eventually gave it an edge here as well. That's why it's performance totally astounded many Japanese pilots, including the more seasoned veterans such as Sakai, Tanimizu, Komachi, Saito, and others.

 

[DarrenW]

If I recall correctly, the F6F-5 achieved 409 MPH and the A6M5 achieved 335 MPH.
Regardless of the results achieved by those two particular aircraft on that particular day, those numbers are about 25-30 MPH higher than the typically quoted speeds for the F6F-5 and about 15-20 MPH lower than the typically quoted speeds for the A6M5.

I admit that 409 mph was on the outer limits of the F6F's maximum level speed ability but it does show that under certain circumstances it was able to go much faster than the oft quoted speeds one has seen in published works over the years. But without knowing the condition of the aircraft under test, such as it's configuration (racks/no racks), and how "cleaned up" the surface was it's impossible to determine what factors allowed for this. I have several sources which put the maximum level speed of the -5 at or near 400 mph so I'm not totally surprised by the test results as you seem to be.

And do you honestly believe that the average A6M5 in the field could manage 350 mph?

 

[DarrenW]

think the change from a 14 cylinder Pratt to a 9 cylinder Wright might be a bit more than just a dash number change.
Cheers,
Wes

Should we call a Spitfire with a Griffon engine a different aircraft than one with a Merlin engine installed? And what about a P-51A as opposed to the B/C/D models? In your view should the installation of the Packard make it a totally different aircraft?

 

[DarrenW]

If the typical F6F-5 really were that fast, then one has to wonder why the new engine and propeller on the F6F-6 prototype did not improve speeds much at all (417 MPH) and why the Standard Aircraft Characteristics sheet lists maximum speed as 330 Kts.

I have a source putting the maximum level speed of the -6 at 425 mph @25,000 feet. With the same engine and propeller the F4U-4 was faster than the latest F4U-1D version by about 25 mph so using this increase as a guideline we can safely put the F6F-5 max speed at around 400 mph.

And it really depends on which BuAer document you are looking at. I have one dated 1 Jul 1944 which puts the maximum speed of the -5N using WEP at 391 mph - this with a drag invoking radome on the starboard wing (which obviously reduced it's maximum possible speed).

 

[eagledad]

Gentlemen,

The attached report gives the tested weights of the A6M5 and F6F-5. Just my 2 cents,wouldn't the high number of F6F kills be due to the fact that in the engagements where they were used, the F6Fs were usually provided a "target rich" environment? Obviously for the F6F to be successful, it had to have well trained pilots and outstanding performance versus its competition.

FWIW

Eagledad

 

[DarrenW]

The attached report gives the tested weights of the A6M5 and F6F-5. Just my 2 cents,wouldn't the high number of F6F kills be due to the fact that in the engagements where they were used, the F6Fs were usually provided a "target rich" environment? Obviously for the F6F to be successful, it had to have well trained pilots and outstanding performance versus its competition.

Thank you eagledad for providing this important document. The detractors of the Hellcat's merits often dismiss the findings here and in other reports which happen to shed a favorable light on it's performance when being compared to it's adversaries.

 

[Barrett]

Late to this party--have not seen recent issues of this excellent site.

The F6F's primary virtues were an extremely rugged airframe mated to a superb engine with potent armament and excellent range. Beyond that, the "docile" flight characteristics meant unexcelled carrier suitability. A friend who was among the youngest USN aces said "It was a good old man's airplane."

Speaking of aces: the "I'd marry it" quote was from Gene Valencia, certainly a colorful personality.

 

[Ivan1GFP]

I think the change from a 14 cylinder Pratt to a 9 cylinder Wright might be a bit more than just a dash number change.

Hello XBe02Drvr,
The FM-2 or F4F-8 wasn't the first Wildcat equipped with a Wright R-1820. Earlier export versions to the British and French also had the R-1820.

Using that mentality the Zero was actually less streamlined than any mark of the Bf 109 and we all know how dirty of a bird it was.
.......
Looks can be very deceiving when discussing aerodynamic drag. We are talking science here and not just casual observations. Do you have any wind tunnel tests to back up your claims of aerodynamic superiority? Just take a look at all the gaps and protuberances of the A6M cowling and you might change your mind.

Hello DarrenW,
It really depends on what you mean by "Draggy" and "Streamlined".
I am referring to absolute drag or the amount of power it takes to drive an aircraft at a particular speed.
The aerodynamic term would be "Equivalent Flat Plate Area".
We have had this discussion before.
This is the only number that makes sense when discussing aircraft of significantly different size but performing the same mission.
By this measurement, the Me 109 has an advantage because although its form drag (Coefficient of Drag) is fairly high, its size is very small and it requires less power to drive it through the air. The A6M is significantly bigger and the Hellcat is huge by comparison.

And the size difference of the two aircraft wasn't a factor here because the power to weight ratios of the A6M5 and F6F-5 were nearly identical at sea level and as altitude rose the Hellcat's ability to maintain a greater percentage of it's horsepower eventually gave it an edge here as well. That's why it's performance totally astounded many Japanese pilots, including the more seasoned veterans such as Sakai, Tanimizu, Komachi, Saito, and others.

Keep in mind that the 343 Kokutai pilots thought the Hellcat was an easy kill, so opinions differ.
I don't disagree with what you are saying about power to weight, but the discussion here is about drag and not about power loading.
The number that you seem to like is Coefficient of Drag and by that measurement, the Hellcat does well.
Perhaps we should look at WHY the Hellcat does so well with such a measurement.
The Coefficient of Drag is calculated by measuring the amount of actual drag and dividing by the reference area for the aircraft.
For typical calculations, the reference area that is used is the Wing Area.
The Hellcat had a Wing Area of 340 feet^2
The A6M5 had a Wing Area of 229 feet^2
The A6M2 had a Wing Area of 241.5 feet^2
The Me109G had a Wing Area of 173 feet^2

Note that the wing of the Hellcat is about twice the area of the Me 109.
In order for the Hellcat to have a better Coefficient of Drag that the Me 109 would require that the actual airframe drag be LESS THAN TWICE that of the Me 109. That number isn't difficult to achieve.
The problem though is that it is the actual drag of the aircraft that determines the amount of power needed to achieve a certain speed.
If one aircraft needs twice the power, then it certainly needs significantly more fuel to accomplish the same objective.

One can of course argue that the aircraft have different capabilities, but for the simple discussion of drag, the measurements really are that simple.

The reason I threw in the example of the A6M2 is that if one does a calculation of Coefficient of Drag in comparing the A6M2 to A6M5, the reduced wing area of the A6M5 puts it at a disadvantage and would suggest that it is the "less streamlined" aircraft, but is this REALLY the case?

I admit that 409 mph was on the outer limits of the F6F's maximum level speed ability but it does show that under certain circumstances it was able to go much faster than the oft quoted speeds one has seen in published works over the years. But without knowing the condition of the aircraft under test, such as it's configuration (racks/no racks), and how "cleaned up" the surface was it's impossible to determine what factors allowed for this. I have several sources which put the maximum level speed of the -5 at or near 400 mph so I'm not totally surprised by the test results as you seem to be.

And do you honestly believe that the average A6M5 in the field could manage 350 mph?

While I do believe that the Hellcat may have been significantly faster than the typically quoted 370-380 MPH, I believe there was something strange going on for the test aircraft to hit 409 MPH on that day.
Japanese manufacturing quality and maintenance was certainly not good by this stage of the war but I do not believe this particular A6M5's performance was a fair representation of the capabilities of the type.

- Ivan.

 

[XBe02Drvr]

The FM-2 or F4F-8 wasn't the first Wildcat equipped with a Wright R-1820. Earlier export versions to the British and French also had the R-1820.

Were the Martlet and other export Wildcats true FM2 "prototypes" with all the airframe as well as engine changes, or were they just F4Fs with a different engine?
Part of the reason I picked on Greg's "dash number" comment was its use in lumping the F4F and FM2 together in discussing kill-loss and sortie-loss ratios. While a Wildcat is a Wildcat is a Wildcat, the two aircraft had significant differences and were used in different combat scenarios. The F4F had to do the heavy lifting, which was mostly over by the time the FM2 showed up, and a large portion of the FM2 fleet was assigned to ASW duty, a generally less risky proposition.
Cheers,
Wes

 

[DarrenW]

Keep in mind that the 343 Kokutai pilots thought the Hellcat was an easy kill, so opinions differ.

Firstly that unit was primarily equipped with the N1K1-2, a much more advanced and potent fighter than the A6M, and was almost entirely comprised of elite aces. But even still, according to official US Navy records they never stood out as anything special (F6F kill/loss ratio found in NACS for the type equates to 28/0).

The Coefficient of Drag is calculated by measuring the amount of actual drag and dividing by the reference area for the aircraft.

I do appreciate what you are trying to explain about drag and how wing area is part of the equation that makes up the CD0. But remarks that the cowling of the F6F was larger which automatically made it less aerodynamically efficient than that of the A6M is not based on any sound scientific principals. In fact just looking at area alone the cowling of the Zeke at it's largest diameter is not less than half that of the Hellcat's cowling, as alluded to in a previous post (it's more like 2/3 according to cross-sectional diagrams). This includes the chin cooling intakes of both aircraft. The statement that the "the difference in frontal area is greater than the difference in horsepower" just doesn't hold water when one compares the power of the R-2800 to the Sakae 21 engine and then looks at the cross-sectional diagrams.

And you are absolutely right that I shouldn't have brought up power to weight ratios when discussing drag. There was reference made that the A6M5 somehow had a superior ratio at lower altitudes and this comment again is without merit. But I do need to be better at organizing my thoughts going forward. Thank you for pointing that out to me.

The reason I threw in the example of the A6M2 is that if one does a calculation of Coefficient of Drag in comparing the A6M2 to A6M5, the reduced wing area of the A6M5 puts it at a disadvantage and would suggest that it is the "less streamlined" aircraft, but is this REALLY the case?

I really don't know. The exhaust stacks and larger inlet of the A6M5 cowling look like they could be a large component of additional parasitic drag, plus there was a 180 horsepower increase with the new model which should have had an effect on overall speed and thus effect the CD0 accordingly as well. Point being, wing area does affect drag but there are additional components that are important to consider as well.

 

[GrauGeist]

The FM-2 also had a taller tail to compensate for the higher horsepower rating of the R-1820-56 (1,350 hp).

 

[XBe02Drvr]

The exhaust stacks and larger inlet of the A6M5 cowling look like they could be a large component of additional parasitic drag

I have an apology to make. When I made that half asleep, bleary eyed "Mark 8 Eyeball" remark I was conveniently forgetting that the topic was A6M5, and I had A6M2 on the brain, which did have a smoother, sleeker cowling/prop spinner profile than the M5, IIRC. As I recall the parameter under discussion was initial acceleration from slower ("dogfighting") speeds in level flight and in a dive. A speed right in the middle of the Zero's optimum dogfighting range would be almost bordering on slow flight for a clean Hellcat. The 'cat would be flying at an elevated AOA, imposing both an induced and a parasite drag penalty on the initial acceleration until it developed enough speed to flatten out. The Zero, OTOH, with its lighter wing loading and closer to the center of its speed range, would already be "flattened out".
Cheers,
Wes

 

[Ivan1GFP]

Were the Martlet and other export Wildcats true FM2 "prototypes" with all the airframe as well as engine changes, or were they just F4Fs with a different engine?
Part of the reason I picked on Greg's "dash number" comment was its use in lumping the F4F and FM2 together in discussing kill-loss and sortie-loss ratios. While a Wildcat is a Wildcat is a Wildcat, the two aircraft had significant differences and were used in different combat scenarios. The F4F had to do the heavy lifting, which was mostly over by the time the FM2 showed up, and a large portion of the FM2 fleet was assigned to ASW duty, a generally less risky proposition.
Cheers,
Wes

Hello XBe02Drvr,
I would have to say that regardless of whether they were the same aircraft, the fact that they performed different missions is enough to justify your distinction. I didn't quite understand your point originally but am in agreement now.

- Ivan.

 

[fliger747]

The F4U-4 was a Very different aircraft and the "C" model R2800 engine a very different engine than any "B" model. Greater HP, higher max RPM, four bladed prop. The internal modification of the oil scavenging system alone gained several hundred HP.

330 Knots is 380 mph. This seems a reasonable number for the F6-F. Whether this was a dry or a wet power speed is open to question. The streamlining between the Zeke and the Hellcat and several other mentioned aircraft isn't as important as the drag associated with wing loading. The light wing loading had penalties in maximum speed, the Zeke was by definition an "angles" fighter.

 

[Ivan1GFP]

Firstly that unit was primarily equipped with the N1K1-2, a much more advanced and potent fighter than the A6M, and was almost entirely comprised of elite aces. But even still, according to official US Navy records they never stood out as anything special (F6F kill/loss ratio found in NACS for the type equates to 28/0).

Hello DarrenW,
This is very interesting. The 343 had more than the average number of elite pilots, but it also had quite a few inexperienced pilots.
The "never stood out as anything special" is not in agreement with the combat reports from the US pilots encountering them and 28/0 is also interesting because of what it implies: that Hellcats never suffered any losses to the N1K and of course that 343 Kokutai never killed a Hellcat....

I do appreciate what you are trying to explain about drag and how wing area is part of the equation that makes up the CD0. But remarks that the cowling of the F6F was larger which automatically made it less aerodynamically efficient than that of the A6M is not based on any sound scientific principals. In fact just looking at area alone the cowling of the Zeke at it's largest diameter is not less than half that of the Hellcat's cowling, as alluded to in a previous post (it's more like 2/3 according to cross-sectional diagrams). This includes the chin cooling intakes of both aircraft. The statement that the "the difference in frontal area is greater than the difference in horsepower" just doesn't hold water when one compares the power of the R-2800 to the Sakae 21 engine and then looks at the cross-sectional diagrams.

You are actually responding to an argument that I did not make. The only mention I had about size differences between A6M and F6F was in Wing Area. The same applies to Cowl Diameters and cross sectional area and relative power of their engines. These were not my arguments.
My argument is for actual drag force which is described by Equivalent Flat Plate Area.
This sounds like a size measurement but it is not. As an example, an actual Flat Plate has an equivalent flat plate area of about 1.3 times its actual cross sectional area.

I really don't know. The exhaust stacks and larger inlet of the A6M5 cowling look like they could be a large component of additional parasitic drag, plus there was a 180 horsepower increase with the new model which should have had an effect on overall speed and thus effect the CD0 accordingly as well. Point being, wing area does affect drag but there are additional components that are important to consider as well.

By my Mark I Mod 0 Eyeball, the A6M5 is a bit more aerodynamic than the A6M2 for the following reasons:
The cowling is more tapered in at the front.
This is probably due to the longer reduction gear housing for the Sakae 21 vs Sakae 12.
The carb scoop under the cowl is replaced by an inlet integrated into the upper lip of the cowl opening.
The consequence is that the upper edge of the cowl is higher but it is still not higher than the fuselage ahead of the cockpit.
The gun troughs are gone.
The cowl is longer but that should make no significant difference in drag.
The ejector exhausts do stand above the fuselage line but whatever drag this adds is more than offset by the exhaust thrust as can be seen when comparing the A6M3 and A6M5 which have otherwise identical engines.

Although a comparison of Take-Off power 950 HP to 1130 HP would seem to show a great superiority to the later aircraft, the actual power available at altitude is much closer. At some altitudes it is no more than 50 HP. This fact surprised me when I plotted the power graphs between the two engines. The later engine just has a bit more altitude performance because of a two speed supercharger.

- Ivan.