ThomasP
Senior Master Sergeant
Very nice, Aeroweanie.
The Zero's Maneuverability
- Thread starter MIflyer
- Start date
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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
Holtzauge
Airman 1st Class
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.
Holtzauge
Airman 1st Class
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.
wrathofatlantis
Airman
- 35
- Oct 2, 2023
"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.
wrathofatlantis
Airman
- 35
- Oct 2, 2023
Let me ask you this: Why does Eric Brown say that below 220 mph, in a turn with the FW-190A, you had to push on the stick to keep the nose from going up too high on its own?
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?
Still waiting for a Spitfire gaining turns on a FW-190A below 20 000 feet.
You say something was happening ALL the time, with a huge margin of advantage, but won't provide ONE example. Curious.
No credentials here but I would say it was due to a migration of center of lift forward due to the particular airfoil characteristics as AoA increases or aeroelasticity.
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.
View attachment 798703
I believe there are a few problems with your information. First of all, A6M2 really did not carry all that much internal fuel. It just had a very economical engine.
Your speed estimates imply engine power outputs that are inconsistent with documentation.
There was no 2600 RPM setting. Power at critical altitude was nearly identical to Takeoff power.
Maximum speed really was achieved at around 15,000 Feet.
Where did you get your information for the P-40E running at 60 inches Manifold Pressure?
Yes, these turning/speed envelopes are interesting, but the basic data is always a question, and you can concoct so many possible scenario's and starting points that can make an unlimited range of illustrations, the shear scale of which could power an unlimited discussion!
The 500kph/6km instantaneous turn depiction could mislead. Why are the triangle points all labeled "P40E deflection shot" when the "shots" are unattainable after the start point in S/L 200m trail? These plots are estimated flightpath tracks, the aircraft longitudinal sightline would be many degrees tighter with increasing AoA, by the 2s point I estimate that the Zero would be around 30 degrees below P40 boresight, remaining well below this until flashing past the nose at 50m just after 5s. In reality, taking aimed shots by the P40 at any point in this scenario after the pull started would be impossible AND without visual, the manoeuvre is only theoretical.
The better illustration would be the Zero behind the P40, this would show that the Zero could easily match the turn rate, staying visual and pulling lead as required to take shots all the way around at will.
Eng
GregP
Major
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.
Of course, there weren't many A6M Zeros at 30,000 feet in combat, either. Sure, it could get there. But it wasn't a good place to be for the Zero.
Hardly anybody in WWII stayed in a turning fight for multiple circles, getting slower the entire time. The entire task for the potential victim out front was to get off-plane so the guy behind couldn't hit you with his armament. 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.
But if you think compressing air between the propeller and the wing causes lift, this discussion will not be possible. I studied aerodynamics in the late 60s and early 70s, and switched into electrical engineering when they laid off the aeronautical engineers after the F-111 was completed. I have no desire to argue aero with you or anyone else. I'll just say that I am a pilot of both full scale and RC airplanes, and have a pretty decent working knowledge of WWII aircraft since I work with, on, and around them on a weekly basis at a flying museum.
I have to laugh at your P-51B Me 109G-6 above. The Bf 109 has a lower stall speed than the P-51B, and fights quite well at lower speeds. No self-respecting P-51B pilot would try to get SLOWER against a Bf 109 unless he was VERY fast to begin with. Best corner speed was about 270 mph IAS at 8,000 pounds and 10,000 feet (not many P-51 fights at 10,000 feet. Some, yes). It changed as you got heavier. By "best", I mean 8-g at the slowest speed where it can GET 8-g, meaning smallest radius of turn, at least for a part of a turn.
Nobody flew 75 - 100 turns in combat. Assume the pilot is flying a good fighter. His 360 degree turn is about 25 seconds give or take a bit. 75 turns would take half and hour or more. Right ...
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And there is the rub, if you have to increase the G, you need to trade height for speed. Ultimately, if your machines are similar performance, you end up in the descending circle of joy.
Fighting is quite surprising though, a rookie even in a superior machine will likely lose early encounters with a skilled enemy. If badly placed on manoeuvre ability , don't slow and circle to death, keep energy high and try to find his mistakes, run and come back fast.
Eng
ThomasP
Senior Master Sergeant
Hey wrathofatlantis,
re
Many aircraft in WWII had to ease-up on the stick and a few had to push it forward in high energy turns, in order to not involuntarily exceed AOA and/or G limits. This phenomenon was most commonly encountered while pulling out of high speed dives, but was not uncommon when pulling into high G instantaneous turns - this is part of what the prohibition against snap turns was intended to prevent. Less common, but occasionally encountered by some aircraft, was when there was a forward movement of the center of lift (as Ivan1GFP mentioned above), when the center of gravity moved to the rear (due to fuel or ammunition depletion), or a combination thereof. Depending on the aircraft design, this could happen anywhere in the envelope depending on the specifics of an aircraft designed to be marginally stable - or marginally unstable - in combat load conditions.
The reason you might end up actually pushing on the stick (as opposed to just easing-up) is that the forces on the elevators become so high that the control linkages transmit the force to the stick (overcoming the normal advantage the mechanical advantage of the lever/cam control linkage the pilot otherwise enjoys), whereupon the pilot has to use forward force to keep the stick from going fully to the rear and potentially tightening the turn to the point where the aircraft either stalls out or exceeds the allowable G load.
This is basic mechanics in engineering and physics (and hence in aerodynamics as well).
Modern combat fighters (F-16 is one example) that are designed to be inherently unstable in combat condition use the computerized fly-by-wire control system to overcome the inherent tendency to immediately go into a high G turn.
(I feel like I am leaving something out but cannot see what it is at the moment.)
re
Many aircraft in WWII had to ease-up on the stick and a few had to push it forward in high energy turns, in order to not involuntarily exceed AOA and/or G limits. This phenomenon was most commonly encountered while pulling out of high speed dives, but was not uncommon when pulling into high G instantaneous turns - this is part of what the prohibition against snap turns was intended to prevent. Less common, but occasionally encountered by some aircraft, was when there was a forward movement of the center of lift (as Ivan1GFP mentioned above), when the center of gravity moved to the rear (due to fuel or ammunition depletion), or a combination thereof. Depending on the aircraft design, this could happen anywhere in the envelope depending on the specifics of an aircraft designed to be marginally stable - or marginally unstable - in combat load conditions.
The reason you might end up actually pushing on the stick (as opposed to just easing-up) is that the forces on the elevators become so high that the control linkages transmit the force to the stick (overcoming the normal advantage the mechanical advantage of the lever/cam control linkage the pilot otherwise enjoys), whereupon the pilot has to use forward force to keep the stick from going fully to the rear and potentially tightening the turn to the point where the aircraft either stalls out or exceeds the allowable G load.
This is basic mechanics in engineering and physics (and hence in aerodynamics as well).
Modern combat fighters (F-16 is one example) that are designed to be inherently unstable in combat condition use the computerized fly-by-wire control system to overcome the inherent tendency to immediately go into a high G turn.
(I feel like I am leaving something out but cannot see what it is at the moment.
)
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GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
Pushing foreward on the stick to break out of a dive compression situation also worked.
Sometimes...
Sometimes...
GregP
Major
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.
Aeroweanie
Airman 1st Class
- 102
- Jan 17, 2021
Since P-51B vs. Bf 109G was mentioned, here is my comparison. The P-51B totally dominates the Bf 109G
Thumpalumpacus
Major
We can do the math on it. That sort of thing drinks a hell of a lot of fuel ... not something you want to do once you've jettisoned externals.
A P-51 turning on an 800' radius in a 75-turn fight is covering about 70 miles without moving more than a mile towards home, and is presumably moving at highest possible speed in this circle, meaning the fuel efficiency is awful.
It's a crummy argument. Any fighter pilot staying inside a 1600' circle for ten minutes has already screwed up.
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GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
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...
On the otherhand, it is possible for a Rebel X-Wing or Cylon Raider to do it.
But that's different...
Well, that is also totally conditional as it is for any powered aircraft. It is always a matter of how fast, how high, how tight, how much weight, how much drag and how much power?
With modern agile Fighters it is likely that the human is the limiting factor, but many heavily loaded or less powerful types will have a lower performance, it all depends..
Eng
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
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
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.
