Possibly your disagreement stems from considering different flight situations?
I only had a short look at Kweassa's test, but weren't they comparing sustained turning ability? I could imagine that Ack-Ack is actually using the flaps in instantaneous turns where they might make more of a difference.
(Simplifying things, I'd say that sustained turns are primarily limited by engine power, while instantaneous turns are primarily limited by lift.)
Hi Hohun!
My point is that the key factor in "instantaneous turns" is the stability itself rather than the effects flaps have to offer. Like you've mentioned, my tests measured the tightest turn radius possible to each plane in sustained turns - and when looking at its results, the P-38s were shockingly large in turn radius, and none of the tested data matches real combat experiences.
The most critical component in turns, in my conclusions after doing the tests, seems to be not sustained turns or even instantaneous turns, but rather the very moment where a plane that entered an "instantaneous" turn shifts to "sustained" turn status. The amount of time spent in this "borderline" seems to be the key factor attributing to the P-38's success - since obviously the turn radius itself is actually pitifully large, and flaps actually do not really help much in cutting down the overall radius.
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For example, let's assume a Bf109G at flying at 300mph, is chasing a P-38J that is flying at 300mph. The P-38J enters an evasive turn, and the Bf109G follows.
According to my tests, the tightest turn radius a Bf109G-6 can pull(at maximum throttle) with one notch of flaps out, is 204.9m, at 160mph, which takes 18 seconds to complete 360 degrees.
On the other hand, the P-38J, takes 19 seconds at 170mph, to complete a 360 degrees circle that is 229.9m in radius.
Now, according to above figures, the P-38J should be pretty much dead meat. If we assume a linear increase/decrease in turn radius with different throttle positions, the Bf109G-6 should still be able to outturn the P-38J handily, and pull a turn radius tight enough to shoot it down within the first circle.
However, it doesn't happen that way at all in actual AH combat.
The critical point in maneuvering is when the P-38J pilot enters an evasive turn while flying at 300mph. He chops throttle and kicks hard rudder to cut down on his speed, engages first notch of combat flaps as the speed hits 250mph IAS, and pulls tight as possible.
For the P-38, the time taken to shift from an "instantaenous turn" beginning at 300mph, to a "sustained turn" at 150~180mph at almost idle throttle and flaps out, is very short. The essential factor is that the plane is torqueless, and unless it is pushed to absolutely drastically high levels of AoA over its stalling limit, it will not destabilize.
For the Bf109G-6, it is very different. As he sees the P-38J enter a tight turn, he decides to follow it, also chops throttle and kicks rudder. However, the difference in torque that effects the attitude of the plane is severe when throttle setting is changed drastically over a course of such short time. The destabilization in the roll axis when the speed creeps under 200mph, where the 109 is able to use its own flaps, is also severe.
A slightly wrong input will halt the 109s turn, where the pilot must correct its position and stop pulling back on the stick. While the P-38J has already entered a very tight turn at very slow speeds, and truckin' it's way to 360, the Bf109 is halted here and there during its turn, since the overall difficulty of maintaining such tight turn in the plane is often overwhelmingly difficult a task for the pilot.
To me, it is clear that this critical factor which allows the P-38, a plane with a relatively large turning radius, to so often outmaneuver much tighter turning planes, is not the flaps, but it's stability during the turns. A stability which allows the plane to dump it's speed very fast, and very easily enter a turn that is slow in speed, and keep it there.
The flaps itself ofcourse, helps greatly in keeping the plane slow, and offers more stability due to its effects. However, the largest factor in work is not the flaps, but the torquelessness.
By comparison, the twin-engined fighters of German Bf110 or the British Mosquito, outturns every P-38 in the turn radius by quite a handful. Except I've never seen anyone claiming the P-38 cannot match a 110 or a Mosquito during maneuvers. The key difference between the Mosquito/110 and the P-38 is power, and, stability.
