ThomasP
Senior Master Sergeant
Very nice, Aeroweanie.
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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?
I apologize if I have missed something previously posted. I haven't had time to read through all 11+ pages of this thread.
Recently, I have been working on an evaluation of the P-38. While this isn't complete, I have put together an E-M model of it. I also put together a model of the A6M2, which is a little approximate. Here are comparisons of the P-38H against the A6M2 and P-40C against the A6M2. The P-38H is a bit faster than the A6M2, but otherwise is the A6M2 can easily outturn it. As you can see, the P-40C could transiently pull more G than the A6M2 and could out dive it, but the A6M2 could outturn it.
For the uninitiated, the Ps=0 line is the limit of sustained maneuvering, while the outer line is the limit of transient maneuvering. Where the Ps line touches the zero turn rate line is the maximum level speed of the aircraft.
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The Wooden Eyeball part was a rather poor joke about your name as it translates from German.
Regarding the Testing of Koga's A6M2, there is actually some documentation in this thread if you missed it.
Look for Post #156 by R Leonard.
The tests did not seem to exceed the 2550 RPM limit, list the Manifold Pressures used and don't even seem to have hit the limit of what the engine was capable of.
There are comments in at least one of the reports as to the poor finish and ill fitted panels and carburetor problems.
As for an indication of what the actual Manifold Pressure limitations were, it is worth looking at the drawing of the Manifold Pressure Gauge in one of the other reports.
From earlier research, I believe that the limits as shown on the gauge were correct for A6M2 (Type 0 Mk. I) but the Japanese used the SAME gauge for the Type 0 Mk.II fighter which used the Sakae 21 engine. This was strange.
As for a comparison with the J22, keep in mind that the Nakajima Sakae was a smaller diameter engine than the R-1830. The speed advantage of J22 was probably BECAUSE it had a much smaller wing. It is definitely a fatter aircraft.
As for the Sakae 12, it was not a highly boosted engine and did not get that much development in the A6M series.
The Sakae 21 as I mentioned before got some additional low altitude power and a higher critical altitude. It wasn't a great improvement over Sakae 12 but any more powerful engine would have entirely lost the long range capability of Type 0 as in the eventual A6M8.
As for eyeball determination of drag, sometimes this works and sometimes it does not. A good example of this was the experiments conducted on Spitfire to simulate flush versus round rivets. This proved that on the fuselage, the round rivet heads had no great effect. This is probably because these little imperfections are in the boundary layer of stagnant air. This is also why the radiator intake of a P-51D has about a 3 inch gap from the fuselage. This is also why a model airplane is not necessarily a good aerodynamic test for the full scale beast. You can leave off the windscreen off a model and probably not notice any impact on speed
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.
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?
Yes, ALL FW-190A pilots will tell you this: In a low speed turn that you made as tight as possible, you were pushing on the stick during the turn.
What would your aerodynamics professors say to that?
I see now that I connected the 326 mph estimate to the wrong boost level in my previous replies. Sorry for that. The 326 mph value was actually for the Sakae 12 at 2500 rpm, and looking at my tuning data I'm actually assuming a top speed of around 335 mph based on the US test at 2600 rpm and 35" of boost (see the circa 540 km/h top speed in the attached figure). But in that report (Wright Field 23rd Oct 1942) they say that the 335 mph top speed has not been adjusted to standard atmospheric conditions and compensated for compressibility effects, so that number is probably not a 100% either.
Then about round rivets not having any effect: This may be true further down on the fuselage in a thick boundary layer, but on the forward parts, and on the parts of the wings where you have a negative pressure gradient and a thin boundary layer, they definitely do have an impact. However, I certainly agree about the risks of drawing any conclusions on a model about full scale effects given the huge difference in Reynolds number.
Then about the reason for the boundary layer separator on the P-51: Before this was added there were problems with boundary layer separations in the diffusor part of the intake that caused rumbles in the duct and poor pressure recovery AFAIK. However, given that Aerowenie has written a whole paper about the P-51 radiator installation, I think he can give a much better summary about this than me.
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Nice charts. Good idea to include radius and g-load info in them as well.
I'm happy to see that I get results for the sustained turn rate that are pretty well aligned with yours under those conditions (15,000 ft, 50% fuel): About 13 deg/s max for the Warhawk (albeit the P-40E) and circa 20 deg/s max for the A6M2 Zero. Especially since it looks like I'm assuming slightly higher top speeds than you for both aircraft by the looks of it, at least if the turn rate equal zero in your chart align well with your top speed estimates. In addition, we probably have slightly different power and weight estimates as well.
I'm currently working on a paper comparing these two aircraft, and while it's not quite ready yet, I attach a part of the draft with a simulation showing my estimate on how they compare when it comes to instantaneous turn performance. However, this is at almost 20,000 ft and in that particular simulation I'm assuming full fuel load for both which of course is to the Zero's disadvantage given its massive internal fuel capacity.
Of course, I don't think anyone is expecting the Warhawk to out-turn the Zero, but the chart still serves to give an idea about just how big the difference was I think.
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Corner velocity means the minimum speed at which you can sustain max g. At 10,000 feet, corner speed for a P-38 was 290 mph IAS and 6-g. At 20,000 feet, corner speed was about 270 mph IAS and 4.2-g. At 30,000 feet, corner speed was 220 mph IAS and about 3.2 g or so. There weren't many airplanes in WWII that could turn harder than a P-38 at 30,000 feet. Pull much more than about 3.2 g at 30,000 feet, though, and you were just falling."Best cornering speed", by which I presume you mean the maximum G a pilot could sustain at the time, was 6 G.
The SETP in 1989 found the lowest speed to touch 6G horizontally on the P-51D (and by that I mean truly horizontally) was "very close to the maximum level speed", which at METO at 10 000 feet in those 1989 tests meant 320 mph. So say 300 mph.
The lowest speed they could touch 6G at was 279 mph spiralling down, probably with partial flaps, which shows spiralling does unload the prop.
The claimed lowest 6G values in the P-51D pilot's manual? 255 mph flaps up, 240 mph with partial flaps.
The P-51D pilot manual does not match real world 6G horizontal turn minimum speed values by at least 24 mph at best, and possibly 60-80 mph at worst, probably because the G load tests were done in dive recoveries. (prop unloaded)
The fact you think of it in 6G terms is the same old misunderstandfing of what WWII air to air combat actually looked like.
6G in combat was rare in WWII combat, and mostly reached in pull-outs (as the SETP found out in 1989). In horizontal turns 6Gs was basically non-existant. You can't use your gunsight, and you would lose your situational awareness.
View: https://youtu.be/wkaTGSpRuJI?si=Oolu80vxuQFWKXvD
1:20 "Fortunately, those shells went just behind my tail. I made I think probably 75 to 100 circles. Whether the Mustang was that much better (makes a small pinching gesture) or I was that much better than him, or a combination of both, I was gaining on him."
3-6 circles was TYPICAL. Just in this thread, one of the roll reversal posts I made has a FW-190A vs P-51B example with 7 consecutive circles, the FW-190A being on par with several P-51s.
The simple fact 75-100 circles did occur multiple times should indicate to you how common were 3-6 circles.
Quote: "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.
As the speed lowers the radius becomes smaller, so the rate probably stays a little closer than that. They would not be constantly reducing the throttle if this was not the case...
They do spiral down, but not always, and on some types they probably should not, especially against the P-51. The P-51 benefitted from spiralling down more than most types.
That speed and power did not help turns can be deduced from a series of Finnish tests on the LaGG-3, but I already knew this from multiple other sources:
"Just got my hands on the scans of the original test reports of the LaGG-3 Series 35 done by FiAF. Plane got designation LG-3 and flew operational sorties. Now reading through and translating the text, but has already shown some interesting stuff."
Maneuverability
360deg turn with full power
2000m altitude 25sec.
4000m altitude 25sec.
6000m altitude 26sec.
360deg at cruise power
2000m altitude 26sec.
4000m altitude 26sec.
6000m altitude 27sec.
According to Karhila, reducing power should little to no effect on the turn rate, and large beneficial effects on radius, which mattered more than rate:
" (Kyösti Karhila, 32 kill Fin ace, most on Me-109G-6 with gondolas): "I found that when fighter pilots got in a battle, they usually applied full power and then began to turn. In the same situation I used to decrease power. When the enemy decreased power, I used to throttle back even more. In a high speed the turning radius is wider, using less speed I was able to out-turn him having a shorter turning radius. Then you got the deflection. 250kmh seemed to be the optimal speed. (BF-109G-6 with gondolas.)"
- Kyösti Karhila, Finnish fighter ace. 32 victories.
But my favourite in that regard is the hansemann quote:
P-51B vs Me-109G-6
"The second Me-109 was maneuvering to get on my tail, and a dogfight developed at 500 ft. (after climbing, from 150 ft. out of attacking a landing Me-109, and this with only a slow gain) At first he began to turn inside me. Then he stopped cutting me off as I cut throttle, dropped 20 degrees of flaps and increased prop pitch. Every time I got to the edge of the [German] airdrome they opened fire with light AA guns. [Meaning he was forced to turn multiple consecutive 360s continuously, even when going towards the enemy ground fire!] Gradually I worked the Me-109G away from the field, and commenced to turn inside of him as I reduced throttle settings."
It was a contest of slowness and smaller radiuses.
That doesn't involve repeated circles, unless YOU have the better-turning airplane. Generally, against Japanese competition, we didn't.
Most WWII fighters COULD generate a 6-g turn, but not for too long. maybe for 90 degrees or so. By then, it had slowed up enough to be out of the envelope where 6-g was possible. The excess power just wasn't there for sustained-g maneuvering.
Yes, ALL FW-190A pilots will tell you this: In a low speed turn that you made as tight as possible, you were pushing on the stick during the turn.
Anyone who believes a WWII fighter would circle 75 - 100 time is not someone I need to try to discuss rational things with. Honorable block earned.
Even jets cannot execute consecutive tight turns without bleeding off airspeed and losing altitude.
On the otherhand, it is possible for a Rebel X-Wing or Cylon Raider to do it.
But that's different...
Since P-51B vs. Bf 109G was mentioned, here is my comparison. The P-51B totally dominates the Bf 109G
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I was also wondering which Bf109G sub-type was being shown, as there was a difference in performance even between the Bf109G-2 and Bf109G-6.Hi,
Please can you be specific on the Power and detail of the types? I can give you a huge range of "Bf 109 G" differences in power and weight. The "P-51B" probably also.
Eng