The Zero's Maneuverability

[special ed]

A good point (I summarise it) is made in summary No 85 on page 3, para 2, item 3, Never follow a Zero into a climb at low speeds, as you slow and stall (or have to reduce climb rate), the Zero can complete a "loop" to position for a rear quarter attack.
So this "loop" would probably be a continued and tightened pull up and back in a normal looping manoeuvre, back onto the tail of the (previous) pursuer wallowing below. This is quite a thing, and remember the Zero was being flown by a test pilot with relatively little experience of the type.

Eng

Somewhere in one of my books on the AVG, one pilot describes his disregarding Chennault's orders about not climbing after the Ki-43 in a tail attack. Remember, the AVG were using the 99 Tomahawks from the scheduled British shipment with the engines assembled by Allison supervisors, so their performance was slightly better than the average P-40B. The AVG pilot remembered opening fire on the tail of the Ki-43 when the Oscar pulled straight up and out of sight in a loop. The AVG pilot also pulled hard up, but soon realised the Ki-43 was about to be on his tail, and he quickly spun out and dived away. I no longer remember which book or which AVG pilot, however if there is enough years left in my life, I plan to reread all my books when I am to old to come out and play.

 

[Ivan1GFP]

Yes, that is a good document and an interesting summary. And the top speed for the Sakae 12 engined variant in that report is the highest I've seen: 326 mph. Granted, those speeds in that document were not corrected for compressibility, but even knocking off a mph or two for that, still quite fast. But IIRC then they did the test at 2600 rpm's, which is a bit higher than the 2500-2550 I've seen from Japanese data. But the top speed of the A6M2 variant with the Sakae 12 engine seems to be an area of contention: there are many different numbers out there to choose from.

If 326 MPH is the best number you have seen then you need to look further. There were a few discussions on J-aircraft and other places suggesting higher speeds.
The US test of Koga's A6M2 gave over 330 MPH in an aircraft that was only about "90%" condition.
That number was "corrected" for reports.
Sakai claimed 345 MPH on overboost but I am not entirely convinced that number is accurate either.

 

[GregP]

I think he must be Gaston.

Especially the creating more energy than was put into it part. YouTube videos don't make it possible to violate basic laws of Physics. Go try it yourself.

WWII airplanes don't have enough excess power to complete 3 consecutive 360° turns at best cornering speed. They will inevitably descend during three turns and, when they get to ground level, they will turn less quickly or hit the ground. Most WWII fighters capable of ONE 20-second 360° turn can only sustain maybe 25 - 30-second turns after the first one unless they descend to add energy to the situation. Yes, they are capable of continuing to turn, but really generally didn't. If the stories above are true, then someone was caught and had a closely-match opponent right behind and was forced to continue turning or die.

3 or 4 examples of that out of 5 years of war is not unreasonable, but NOBODY would want to be in the front airplane.

I think we being Gastonated, AGAIN.

 

[Holtzauge]

If 326 MPH is the best number you have seen then you need to look further. There were a few discussions on J-aircraft and other places suggesting higher speeds.
The US test of Koga's A6M2 gave over 330 MPH in an aircraft that was only about "90%" condition.
That number was "corrected" for reports.
Sakai claimed 345 MPH on overboost but I am not entirely convinced that number is accurate either.

Well I would not expect the A6M2 to be faster than the 326 mph in that report but if there is compelling evidence then that would be interesting.

In the mean time and as a sanity check: The Swedish J22 was also powered by an R-1830 (unlicensed copy!) that put out about the same power, and it did all of 357 mph. However, it was much smaller, with a wing area of 16 sqrm, span 10 m and length 7.8 m. If we compare that to the Zero, it had a wing area of 22.44 sqrm, span 12 m, and a length of 9.06 m.

Eyeballing the two, I would say that the J22 was as clean, if not cleaner aerodynamically than the Zero. So I would say it would be fair to compare them based on size and using the cube law, and if we scale up the J22 to a wing area of 22.44 just like the Zero has, this would result in the following speed:

V=357*(16/22.44)^(1/3)=318 mph

So with that in mind, the 326 mph in the US report seems quite reasonable to me.

 

[GregP]

Well I would not expect the A6M2 to be faster than the 326 mph in that report but if there is compelling evidence then that would be interesting.

In the mean time and as a sanity check: The Swedish J22 was also powered by an R-1830 (unlicensed copy!) that put out about the same power, and it did all of 357 mph. However, it was much smaller, with a wing area of 16 sqrm, span 10 m and length 7.8 m. If we compare that to the Zero, it had a wing area of 22.44 sqrm, span 12 m, and a length of 9.06 m.

Eyeballing the two, I would say that the J22 was as clean, if not cleaner aerodynamically than the Zero. So I would say it would be fair to compare them based on size and using the cube law, and if we scale up the J22 to a wing area of 22.44 just like the Zero has, this would result in the following speed:

V=357*(16/22.44)^(1/3)=318 mph

So with that in mind, the 326 mph in the US report seems quite reasonable to me.

View attachment 798448

One of my favorite relatively obscure airplanes.

 

[Holtzauge]

One of my favorite relatively obscure airplanes.

Yep, it's a nice looking plane. And not only was it fast, but it also climbed well. After the war, Sweden bought a lot of P-51 Mustangs from the US, and designated them the J26. Up high the J22 ran out of steam, but apparently they held their own against the J26 at lower altitudes, and the J22 was actually quite popular with many SwAF pilots.

 

[GregP]

Here's one of my drawings of it:

 

[GregP]

That's one of the most craptacular posts I ever saw!

"Compression of air between the prop and the wing, creating lift from longitudinal tension ..."

My old aerodynamics professors would swoon, as long as they had a brandy to go with it, that is. That makes as much sense as not going hunting because your accordion is in for repairs on one of the reeds.

Compression is not possible without either containment or a shock wave to act as a barrier just as you can't produce thrust in a rocket engine without containment. I'm assuming the virtual airplane above is not supersonic, so ...

But, hey, when you're on a roll, go with it. Tell me more.

How does thrust move a WWII piston fighter aircraft forward?

 

[SaparotRob]

Creatively.

 

[GrauGeist]

That's one of the most craptacular posts I ever saw!

"Compression of air between the prop and the wing, creating lift from longitudinal tension ..."

My old aerodynamics professors would swoon, as long as they had a brandy to go with it, that is. That makes as much sense as not going hunting because your accordion is in for repairs on one of the reeds.

Compression is not possible without either containment or a shock wave to act as a barrier just as you can't produce thrust in a rocket engine without containment. I'm assuming the virtual airplane above is not supersonic, so ...

But, hey, when you're on a roll, go with it. Tell me more.

How does thrust move a WWII piston fighter aircraft forward?

Careful, Greg, or else you might start a lecture on the P-39's amazing virtues...

 

[GrauGeist]

Well I would not expect the A6M2 to be faster than the 326 mph in that report but if there is compelling evidence then that would be interesting.

In the mean time and as a sanity check: The Swedish J22 was also powered by an R-1830 (unlicensed copy!) that put out about the same power, and it did all of 357 mph. However, it was much smaller, with a wing area of 16 sqrm, span 10 m and length 7.8 m. If we compare that to the Zero, it had a wing area of 22.44 sqrm, span 12 m, and a length of 9.06 m.

Eyeballing the two, I would say that the J22 was as clean, if not cleaner aerodynamically than the Zero. So I would say it would be fair to compare them based on size and using the cube law, and if we scale up the J22 to a wing area of 22.44 just like the Zero has, this would result in the following speed:

V=357*(16/22.44)^(1/3)=318 mph

So with that in mind, the 326 mph in the US report seems quite reasonable to me.

View attachment 798448

Seeing the A6M and J22 together in this post reminded me that Sweden was in contact with Japan about a possible purchase of A6Ms.

Negotiations broke down over the complexities of having them shipped safely to home ports.

 

[GregP]

Careful, Greg, or else you might start a lecture on the P-39's amazing virtues...

My apologies. I'd rather go lie down on a highway.

I'll just let it go and resist anything not related to Zero Maneuverability from our new friend. As I recall, it is quite maneuverable. Perhaps I disremember.

You are a gentleman, a scholar, and a judge of fine horseflesh for setting me on the straight and narrow path.

Strike my earlier comments and slap me.

 

[Greg Boeser]

Slap GIFs - Get the best GIF on GIPHY

Found on Google from giphy.com

images.app.goo.gl

 

[Ivan1GFP]

Well I would not expect the A6M2 to be faster than the 326 mph in that report but if there is compelling evidence then that would be interesting.

In the mean time and as a sanity check: The Swedish J22 was also powered by an R-1830 (unlicensed copy!) that put out about the same power, and it did all of 357 mph. However, it was much smaller, with a wing area of 16 sqrm, span 10 m and length 7.8 m. If we compare that to the Zero, it had a wing area of 22.44 sqrm, span 12 m, and a length of 9.06 m.

Eyeballing the two, I would say that the J22 was as clean, if not cleaner aerodynamically than the Zero. So I would say it would be fair to compare them based on size and using the cube law, and if we scale up the J22 to a wing area of 22.44 just like the Zero has, this would result in the following speed:

V=357*(16/22.44)^(1/3)=318 mph

So with that in mind, the 326 mph in the US report seems quite reasonable to me.

I would not trust (wooden) eyeballing an aircraft profile for how aerodynamic it is. Looks can be quite deceiving.
The problem here is that the actual test of the captured and restored (wrecked) aircraft gave higher numbers than that report stated.
The Aleutian A6M2 came down in a bog with full flaps and gear down.
The initial contact wiped off both main gear and destroyed the flaps and bent the propeller.
The aircraft dug in the nose and flipped which destroyed the fin and canopy and broke the radio mast
and probably bent things up a bit with an airframe of such light construction.
Parts of the aircraft sat underwater for about a month.
The details of the repair are listed in various places.
When asked whether the aircraft was 100%, one of the pilots (I believe it was Eddie Sanders) commented that it was about 90%.
There were places such as the landing gear where the panels did not really meet flush when retracted.
The carburetor was apparently rebuilt incorrectly. It DID have a feature to compensate for negative G but this obviously did not work in the rebuild.

Even with all this that wasn't quite right, the aircraft was able to achieve over 330 MPH in testing and had fewer failures than some of the US fighters it was tested against.
On has to wonder that if a bent bird is doing over 330 MPH, what would an unbent bird do?

Another thing worth noting is that the Sakae 21 was better than Sakae 12 in only two areas.
It had higher power at very low altitude (low blower) and could maintain about the same HP up to around 20,000 Feet (high blower) instead of 15,000 Feet.

As for comparisons with the R-1830 in the J22, one has to know something about what version of R-1830 was installed.
The US had a tendency NOT to export versions with the most modern superchargers. At what altitude was the J22 reaching its maximum speed?

 

[Ivan1GFP]

Seeing the A6M and J22 together in this post reminded me that Sweden was in contact with Japan about a possible purchase of A6Ms.

Negotiations broke down over the complexities of having them shipped safely to home ports.

I have always wondered how differently things may have turned out if the Luftwaffe had flown A6M2 instead of Me109E.

 

[GrauGeist]

The Allies would have adapted to Luftwaffe A6Ms just as they did with the Japanese in the Pacific.

However, the Luftwaffe would have been able to project further into Great Britain than was possible historically.

This would have created some serious difficulties for Britain.

 

[Greg Boeser]

I would not trust (wooden) eyeballing an aircraft profile for how aerodynamic it is. Looks can be quite deceiving.
The problem here is that the actual test of the captured and restored (wrecked) aircraft gave higher numbers than that report stated.
The Aleutian A6M2 came down in a bog with full flaps and gear down.
The initial contact wiped off both main gear and destroyed the flaps and bent the propeller.
The aircraft dug in the nose and flipped which destroyed the fin and canopy and broke the radio mast
and probably bent things up a bit with an airframe of such light construction.
Parts of the aircraft sat underwater for about a month.
The details of the repair are listed in various places.
When asked whether the aircraft was 100%, one of the pilots (I believe it was Eddie Sanders) commented that it was about 90%.
There were places such as the landing gear where the panels did not really meet flush when retracted.
The carburetor was apparently rebuilt incorrectly. It DID have a feature to compensate for negative G but this obviously did not work in the rebuild.

Even with all this that wasn't quite right, the aircraft was able to achieve over 330 MPH in testing and had fewer failures than some of the US fighters it was tested against.
On has to wonder that if a bent bird is doing over 330 MPH, what would an unbent bird do?

Another thing worth noting is that the Sakae 21 was better than Sakae 12 in only two areas.
It had higher power at very low altitude (low blower) and could maintain about the same HP up to around 20,000 Feet (high blower) instead of 15,000 Feet.

As for comparisons with the R-1830 in the J22, one has to know something about what version of R-1830 was installed.
The US had a tendency NOT to export versions with the most modern superchargers. At what altitude was the J22 reaching its maximum speed?

The Swedes built a licenced version of the SC3-G rated at 1065 hp for take off.
This same engine was used in Finland in their Hawk 75s.

 

[Holtzauge]

I would not trust (wooden) eyeballing an aircraft profile for how aerodynamic it is. Looks can be quite deceiving.
The problem here is that the actual test of the captured and restored (wrecked) aircraft gave higher numbers than that report stated.
The Aleutian A6M2 came down in a bog with full flaps and gear down.
The initial contact wiped off both main gear and destroyed the flaps and bent the propeller.
The aircraft dug in the nose and flipped which destroyed the fin and canopy and broke the radio mast
and probably bent things up a bit with an airframe of such light construction.
Parts of the aircraft sat underwater for about a month.
The details of the repair are listed in various places.
When asked whether the aircraft was 100%, one of the pilots (I believe it was Eddie Sanders) commented that it was about 90%.
There were places such as the landing gear where the panels did not really meet flush when retracted.
The carburetor was apparently rebuilt incorrectly. It DID have a feature to compensate for negative G but this obviously did not work in the rebuild.

Even with all this that wasn't quite right, the aircraft was able to achieve over 330 MPH in testing and had fewer failures than some of the US fighters it was tested against.
On has to wonder that if a bent bird is doing over 330 MPH, what would an unbent bird do?

Another thing worth noting is that the Sakae 21 was better than Sakae 12 in only two areas.
It had higher power at very low altitude (low blower) and could maintain about the same HP up to around 20,000 Feet (high blower) instead of 15,000 Feet.

As for comparisons with the R-1830 in the J22, one has to know something about what version of R-1830 was installed.
The US had a tendency NOT to export versions with the most modern superchargers. At what altitude was the J22 reaching its maximum speed?

I would not disparage a plane just because it was built in wood: Even in WW2, it would be more appropriate to call it composite which of course has much more positive connotations to our modern ears. An advantage with wooden "composites" is that you can easily do compound curved panels and improve the aerodynamics that way. The Mosquito was a "composite" plane and so was the J22 in some parts, and I think few would say the Mosquito was crap just because it was built of "wood"?

When it comes to drag the biggest dominating factor is size: The frontal area and wetted area. The Bf-109 was actually not a very clean design, but it was still fast simply due to its small size. Then when it comes to eyeballing, this can actually tell you a lot if you look at the right things: For example, are there bulges for guns etc? Is there a razorback fuselage or a bubble type canopy? If the latter, how well faired is it? Is the radiator/air cooling entry well done? Is the forward windscreen upright and plane or angled backwards, rounded and faired? How are the wing and fuselage "lines" and are there ill-fitting openings, hatches and gaps? Is the main landing gear totally retractable and fully hatched in? Is there a fixed or retractable tailwheel?

And comparing this list between the J22 and Zero I don't find the J22 wanting, so as a first order approximation scaling on wing area alone will give you a good idea about their relative performance. However, that being said, I have not seen good data on how much power they (the Japanese pilots) extracted from the Sakae 12 at WEP. But in the US test they ran at 2600 rpm (no boost data), and to the best of my knowledge Japanese data says max 2550 rpm WEP. I have a Japanese power chart that goes up to 2550 and in that I have extrapolated what 2600 RPM would do, and apart from increasing the FTH, the power in that chart goes up from 960 hp to about 980 hp. However, that chart is from May 1939 and the boost pressure is not given. And it's of course possible that they increased boost pressure later on. So if anyone has data on this, this would be interesting to hear about.

About the J22: It only had a single stage blower (TWC-3 R-1830-SC3-G) and the speed point at altitude is not point shaped but like on the Zero more rounded in shape with the top speed achieved at about 15,000 ft. However, digging a bit deeper, I found some simulations done by the Swedish aeroengineer Håkan Langebro, and it seems it only did the 360 mph with 100 octane fuel and the engine producing circa 1200 hp, and with 87 octane it only did slightly under 350 mph with 1050 hp which is still quite good for that amount of hp.

So if the small and clean J22 did 350 mph with 1050 hp, then the 345 mph Sakai claims for the much bigger Zero sounds optimistic to me. Especially if the absolute top power they got out of the Sake 12 was only 980 hp. But it would of course help to be able to pin down the exact power output of the Sakae 12 when it was at the peak of development, and if this was higher than the 980 hp at 2600 rpm which is the highest I know about. In addition, are we sure that the 345 mph with the Zero Sakai claims was with a Sakae 12, and not the Sakae 21 engine?

 

[PAT303]

No argument, you are comparing Spitfire Mk IX with Merlin 66 25lb boost 1944 performance against the 1941 Fw 190. Further to that, the July 1942 AFDU trial against the captured Fw 190 showed that the 1941 Fw 190 had the edge over the new Spit Mk IX, below 20,000 feet, which was also badly placed with the float carb weaknesses.

Eng

Wasn't comparing a 1944 MkIX to the FW190 at all, in 1942 both aircraft were as closely matched in performance as the BoB MkII and Emil were, it was the later Mk IX LF that showed a clear performance edge over the 190A as I have already posted.