Bingo!
Japanese Zero vs Spitfire vs FW 190
- Thread starter Chiron
- Start date
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If we were having this conversation down the pub or at a BBQ with people with no idea most likely we would be glamourising the Spit, but smart people look at all the information available and understand how different factors affect the overall outcome. A good example, Heinrich Baer fought throughout the war right across Europe but ended the war with a lower score than those who fought just in Russia, even though he finished with a lower score he is still held in very high regard because the kills he did make were against a much stronger better organised opposition.
No way, I'd have to take the hood off and have my ugly mug poking out above the seat armour, and the top bar on the windscreen would be straight across my eye line, great photo showing just how small the 109 actually is.
fubar57
General
Fw190
fubar57
General
?
Airframes
Benevolens Magister
???
Hello Gentlemen,
I am kind of late in on this discussion but am a bit surprised that no one has actually pointed out the major flaw in the test of Spitfire Vc against A6M3 Model 32.
This report is not new to me and I was surprised that it was quoted here and that no one has yet disputed its results.
First of all, I won't even try to argue whether the Spitfire V in the test should have been running +9 pounds or +16 pounds boost.
That has been beaten to death with no clear result.
The important factors to consider from this test IMHO are:
1. The J-fighter being tested was a A6M3 Model 32 or Type Zero Mark II.
This is a bit different from the A6M2 Model 21 or Type Zero Mark I that was encountered over Darwin.
The A6M2 had more wingspan and wing area and was a lighter and more agile aircraft.
2. The A6M3-32 at Eagle Farm was rebuilt from wrecks. It was flyable but hardly representative of a properly performing aircraft
as can be seen by its maximum speed and critical altitudes.
The Japanese manual lists a speed of 290 Knots at 6150 meters for the Model 32.
The same manual lists a speed of 275 Knots at 4400 meters for the Model 21 and
294 Knots at 5900 meters for the Model 52, but these are not "maximum speeds" as we understand them.
Note that the A6M5 model 52 in good condition is generally listed at capable of 351 MPH.
Note that the test against the Spitfire only showed a maximum speed that was 2 MPH faster than the "accepted" value from the Akutan A6M2 tested in the US and THAT aircraft also was not flown at "overboost" for those tests.
In looking over other information listed in my copy of the test of the Eagle Farm A6M3-32, they apparently ran the engine at no more than 2600 RPM and 40 inches Hg (about +256 mm Boost) which is quite a bit under the Take-Off / Emergency Rating of 2750 RPM and +300 mm Boost.
Those differences might have also made a difference.
With these factors in mind, I suspect that the actual A6M2 that fought over Darwin were a bit more capable than the A6M3-32 that was tested.
Thoughts?
- Ivan.
I am kind of late in on this discussion but am a bit surprised that no one has actually pointed out the major flaw in the test of Spitfire Vc against A6M3 Model 32.
This report is not new to me and I was surprised that it was quoted here and that no one has yet disputed its results.
First of all, I won't even try to argue whether the Spitfire V in the test should have been running +9 pounds or +16 pounds boost.
That has been beaten to death with no clear result.
The important factors to consider from this test IMHO are:
1. The J-fighter being tested was a A6M3 Model 32 or Type Zero Mark II.
This is a bit different from the A6M2 Model 21 or Type Zero Mark I that was encountered over Darwin.
The A6M2 had more wingspan and wing area and was a lighter and more agile aircraft.
2. The A6M3-32 at Eagle Farm was rebuilt from wrecks. It was flyable but hardly representative of a properly performing aircraft
as can be seen by its maximum speed and critical altitudes.
The Japanese manual lists a speed of 290 Knots at 6150 meters for the Model 32.
The same manual lists a speed of 275 Knots at 4400 meters for the Model 21 and
294 Knots at 5900 meters for the Model 52, but these are not "maximum speeds" as we understand them.
Note that the A6M5 model 52 in good condition is generally listed at capable of 351 MPH.
Note that the test against the Spitfire only showed a maximum speed that was 2 MPH faster than the "accepted" value from the Akutan A6M2 tested in the US and THAT aircraft also was not flown at "overboost" for those tests.
In looking over other information listed in my copy of the test of the Eagle Farm A6M3-32, they apparently ran the engine at no more than 2600 RPM and 40 inches Hg (about +256 mm Boost) which is quite a bit under the Take-Off / Emergency Rating of 2750 RPM and +300 mm Boost.
Those differences might have also made a difference.
With these factors in mind, I suspect that the actual A6M2 that fought over Darwin were a bit more capable than the A6M3-32 that was tested.
Thoughts?
- Ivan.
They were rebuilt aircraft -- but apparently with the fuel used in the US it made up the difference and them some.
From the Bunrin-Do Co Ltd. 'Famous Airplanes of the World' series (as translated by Shinpachi):
In general, these performance values tested by the US are higher than those by IJA or Nakajima.
Maximum speed, above all, indicates incredibly superior values that the Japanese were unable to achieve at all.
That would have been because they used high octane gasoline.
This was in reference to Ki-43 data, but I wouldn't be surprised if it applied to other types.
From the Bunrin-Do Co Ltd. 'Famous Airplanes of the World' series (as translated by Shinpachi):
In general, these performance values tested by the US are higher than those by IJA or Nakajima.
Maximum speed, above all, indicates incredibly superior values that the Japanese were unable to achieve at all.
That would have been because they used high octane gasoline.
This was in reference to Ki-43 data, but I wouldn't be surprised if it applied to other types.
Shortround6
Major General
Higher octane gas does not have more energy per gallon, it allows for higher power by allowing extra boost, unless the test pilots were using higher than normal boost as used by the Japanese there should be no extra performance.
If at less that full throttle height even running the engine 100-200rpm under max rpm might not have much effect on power as depending on the throttle linkage and boost limit mechanism the same boost or higher boost can be achieved as at the slightly higher rpm. With more boost the engine may make more power at lower altitudes than at full rpm, lower boost at near the full throttle height.
Some non engine differences between the Hamp and the earlier Zeros are the clipped wing, it was not just the wing tip left off but the ailerons were modified. and actually made smaller. However since they ran practically to the tip (and the control forces were less) they may have been more effective than the A6M2 and allowed a higher roll rate (which might still have been poor). between the clipped tips and heavier skinning in places the A6M3 was allowed a dive speed about 20kts higher than the earlier Zeros, not a dramatic change but against less than stellar diving allied planes it may have tipped the balance in a few combats.
The loss of about 9sq ft of wing and the increase of 240-280lbs of weight may have had a minor change to the handling of the Hamp.
If at less that full throttle height even running the engine 100-200rpm under max rpm might not have much effect on power as depending on the throttle linkage and boost limit mechanism the same boost or higher boost can be achieved as at the slightly higher rpm. With more boost the engine may make more power at lower altitudes than at full rpm, lower boost at near the full throttle height.
Some non engine differences between the Hamp and the earlier Zeros are the clipped wing, it was not just the wing tip left off but the ailerons were modified. and actually made smaller. However since they ran practically to the tip (and the control forces were less) they may have been more effective than the A6M2 and allowed a higher roll rate (which might still have been poor). between the clipped tips and heavier skinning in places the A6M3 was allowed a dive speed about 20kts higher than the earlier Zeros, not a dramatic change but against less than stellar diving allied planes it may have tipped the balance in a few combats.
The loss of about 9sq ft of wing and the increase of 240-280lbs of weight may have had a minor change to the handling of the Hamp.
Hello Greyman,
Although I trust that Shinpachi translated the FAOTW excerpt correctly, I do not believe the excerpt itself is correct.
Here is why:
The Allies knew the grade of fuel that was used by the Japanese services. They were interested in the level of performance that they were likely to encounter when meeting these aircraft in combat. It would make no sense and be a waste of resources to try to "hot-rod" a captured fighter in less than pristine condition to see what the Japanese were not doing.
This can be seen by the test of the Ki-84 and its engine that was done at Middletown, PA after the war: Japanese Aircraft Performance
Claims have been made that this aircraft was tested with higher grade US fuel, but the test account clearly shows that 92 octane fuel was used along with anti detonant as was normal practice for the Japanese Army.
As Shortround6 stated, it would not make a difference anyway unless the boost pressure were raised beyond what the Japanese were using. This is clearly NOT the case and in fact the boost and RPM are below what the Sakae 21 engine were capable of and the critical altitude is also below even what the manual states.
My suspicion in reading over the TAIC testing summaries is that although the manuals and Japanese testing used typically "Normal" or "Rated" power, the Allied testing used Take-Off ratings as the equivalent of War Emergency which is never listed in the Japanese manual. (Their Normal power seems to be very similar to what we would consider the max continuous rating.)
In the case of this particular "Hamp", I believe it was not representative in performance because according to the manual it should have been capable of 290 Knots at 6150 meters (333.5 MPH) at normal power.
Normal Power is 2500 RPM and +75 mm boost.
Take-Off Power is 2750 RPM and +300 mm boost.
Eagle Farm testing was at 2600 RPM and +256 mm (40 inches Hg) and gave just one knot more speed. Seeing these numbers, one would have to wonder, "WHY did they pick these numbers?".....
Now back to the A6M2 that fought over Darwin..... (We will come back to the Mark II fighter in a bit.)
The manual lists a maximum speed of 275 Knots at 4400 meters (316 MPH)
This is at Normal Power which is 2350 RPM and +50 mm boost.
Take-Off Power is 2550 RPM and +250 mm boost.
The 316 MPH is clearly NOT a maximum speed if a captured and repaired example in the US in about 98% condition is capable of achieving 332 MPH. If you go through the list of repairs, it is obvious that this aircraft though repairable was hardly in "as new" condition when tested. As an example, the automatic mixture control did not work, and the gear doors were not quite flush.
The next part is from an article by Richard Dunn and seems somewhat plausible. According to Saburo Sakai who was intimately familiar with the A6M2, when asked about the maximum speed, stated 345 MPH on overboost.
An overboost setting was noted but not used in US testing.
What is the actual maximum speed of A6M2? I can say *I* am not really sure.
Now back to the A6M3 at Eagle Farm.
I suspect that the people working on the new Mark II Zero were not really familiar with the changes and did not have a manual to know how to operate it.
That is why they used settings that were pretty similar to the maximums for the Mark I Zero: 2550 RPM and +250 mm boost.
They didn't realise that the RPM and boost limits were much higher than the earlier engine and the critical altitude in high blower was also much higher.
Here is something I found to be quite odd when looking for differences between the Mark I and Mark II Zero:
Look at the Manifold Pressure gauge that is to the right of the stick. Note the part that is in Red.
This panel is from the A6M5 (Mark II) but the interesting thing is that this gauge apparently is unchanged from the one used on the A6M2 (Mark I) that only allowed up to +250 mm boost.
That might be another reason why the folks at Eagle Farm thought the maximum boost was no different between the two engines.
- Ivan.
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Hello Shortround6,
Although people don't mention it much, the A6M actually had a pretty high roll rate at low to medium speeds. This can be confirmed by video interviews of current A6M pilots and also by timing the roll performance of modern aircraft with a stopwatch.
It's at high speed that life got a bit ugly.
I am sure you already know this, but the later A6M didn't just lose aileron span at the wing tip. It also had the inboard edge of the aileron moved one wing station outboard.
Regarding diving speed:
Although the diving speed of A6M3-32 is 20 Knots higher than A6M2-21, I believe this was because of the difference in load due to the reduced wing span. The reason for this conclusion is because the A6M3-22 which came after the Model 32 has the same diving speed limitation as the older Model 21.
In comparing the Mark I and Mark II Zero, it can also be noted that the Japanese themselves considered the Mark I to have greater fighting ability below 20,000 feet and even made that statement in their manual. That would be a bit discouraging to a fellow about to climb into a brand new Mark II fighter.
- Ivan.
Hello XBe02Drvr,
There are a couple issues with this evaluation. First of all, the elliptical planform would be optimal if there were no aerodynamic twist built into the wing, but there actually is, so the lift distribution isn't quite what it would be with a simple elliptical wing.
The Spitfire (David Lednicer)
Although the Spitfire appears very nicely streamlined, the appearance may be deceptive. At one point, there was a question about how much drag resulted from normal domed rivets as opposed to flush rivets. (The famous split pea test) Eventually it was determined that domed rivets were worse (no surprise) but could be tolerated with very little penalty in fuselage construction.
The twin underwing radiators were not really the optimal choice but many aircraft had the same design issue. Note that the successor design, the Spiteful / Seafang went with a single radiator under the aft fuselage and was a much faster aircraft for the same installed power.
I believe you and I are thinking the same thing here. The wing and fuselage may be at an optimal relative angle for parasitic drag in a high AoA condition such as when maneuvering but in a low AoA attitude such as in level flight or zero G for maximum acceleration in a dive, the fuselage may not be at the optimum angle for low parasitic drag even though the wing is an an optimum angle.
I am not an engineer but as I understand the issue, without a restriction into the bowl of the carburetor, under negative G the float goes up and the carb floods and the engine cuts. With the restrictor, the float still goes up, but the bowl cannot flood as quickly and although there is a loss of power, there isn't flooding unless the negative G is sustained.
I don't believe the Merlin Spitfires had fuel injection at least up through the Mk. IX and contemporaries but perhaps later ones did.
- Ivan.
I think you're right there, but didn't they go through an intermediate step of pressure carb between the float bowls and the full-on fuel injections? I know from personal experience there's no negative G penalty with a pressure carb.
Cheers,
Wes
[QUOTE="
I am not an engineer but as I understand the issue, without a restriction into the bowl of the carburetor, under negative G the float goes up and the carb floods and the engine cuts. With the restrictor, the float still goes up, but the bowl cannot flood as quickly and although there is a loss of power, there isn't flooding unless the negative G is sustained.
I don't believe the Merlin Spitfires had fuel injection at least up through the Mk. IX and contemporaries but perhaps later ones did.
- Ivan.[/QUOTE]
I'm not a engineer either, but I do know that when the float goes up in a carburetor, it shuts off the fuel flow to the float bowl in the carb., the engine cuts out because it's starved for fuel, not flooded.
I am not an engineer but as I understand the issue, without a restriction into the bowl of the carburetor, under negative G the float goes up and the carb floods and the engine cuts. With the restrictor, the float still goes up, but the bowl cannot flood as quickly and although there is a loss of power, there isn't flooding unless the negative G is sustained.
I don't believe the Merlin Spitfires had fuel injection at least up through the Mk. IX and contemporaries but perhaps later ones did.
- Ivan.[/QUOTE]
I'm not a engineer either, but I do know that when the float goes up in a carburetor, it shuts off the fuel flow to the float bowl in the carb., the engine cuts out because it's starved for fuel, not flooded.
I'm not a engineer either, but I do know that when the float goes up in a carburetor, it shuts off the fuel flow to the float bowl in the carb., the engine cuts out because it's starved for fuel, not flooded.[/QUOTE]
Hello Tyrptom,
You are absolutely correct.
Thanks for the reminder.
Perhaps it is an issue of what happens to the fuel that is already in the bowl. We don't run into a lot of negative G situations when tuning automotive carbs.
- Ivan.
Reluctant Poster
Staff Sergeant
- 1,464
- Dec 6, 2006
The Spitful radiators were under each wing, not the back of the fuselage. The gain in speed was due to the laminar flow wing.
The vast majority of Spitfire Mk 8s and 9s were equipped with Merlin 66s or 70s which had Bendix injection carbs. Before that the internals of the SU float chamber had been modified to mitigate g effects in which case the flow restriction office was deleted.
Hello Reluctant Poster,
Thanks for the correction. I was just looking over some photographs of the Spiteful / Seafang and found the same thing about the radiators and was wondering which aircraft I was confusing it with.
Do you happen to know when the SU carbs were modified?
- Ivan.
Reluctant Poster
Staff Sergeant
- 1,464
- Dec 6, 2006
I am unable to find an exact date.
The Martin Baker MB5 had a P51 style radiator.
