The Me-109G was likely not more maneuverable than the P-40 on the horizontal, especially in prolonged sustained turns, because it tended to bleed speed on level turns… Spiralling down it did better, but that usually meant giving up on shooting the pursuer, since being below makes this near impossible…
The Me-109G was more of an Eastern Front fighter in late 1944: By then, 70% of Western Front fighters were FW-190As, which was more competitive in sustained turns vs the P-47D and P-51s… The FW-190A was simply better, period, and the Me-109G would have been phased out if the FW-190A had better handling at high altitudes above 21 000 ft, where the bombers were…
The Me-109G was best used on the vertical as a high speed dive and climb fighter, but was cornered into using the high speed spiral climb against the better vertical performance of higher flying US fighters, which could use their extra cruising altitude to negate the better Me-109G sustained climb by zooming up to it after diving… The Me-109G was a poor turn fighter that could barely match the P-51 in sustained turns, and had no hope at all in left turns vs the P-47 in prolonged turns…
The P-51 was very close to the Me-109G, but, by lowering the power and dropping its flaps, it could gain in sustained turns with the prop pitch set on coarse at lower speeds. Maybe the Me-109G would again be close if it did the same, but, as I said, the Me-109G was actually more often used as a high speed vertical maneuvering fighter. “A Floret” in the words of Gunther Rall…
Despite some tests done claiming the contrary, the sustained turning ability of the P-47D, in actual real-life combat, was superior to both the P-51 and the Me-109G, even with its deceptive wider initial radius… KG 200’s conclusion on an early P-47D Razorback’s performance was unequivocal: “The P-47 out-turns our Bf-109G”
The FW-190A was another kettle of fish, and had poor high speed handling, but was the only mass-produced Luftwaffe fighter to out-match the P-47D in sustained turns, though not by much vs the early Razorback to left. Again, the FW-190A had a wider initial radius of turn than a Spitfire, but if an immediate solid hit was not achieved by the British fighter (within around the first 360°), the Spitfire would then almost inevitably fall behind and be caught in level turns by the FW-190A… (The Spitfire was in fact not competitive at all with the FW-190A in sustained turns, and not with the Hurricane either, which could out-turn the Spitfire but not the FW-190A in the words of Canadian Hurricane pilot John Weir: Many other British, Russian and German sources all confirm this, usually pointing out to precisely the same peculiar FW-190A handling features, like its poor tail-down “sinking” or wing-drop “snapping” high speed handling…)
The FW-190D was less maneuverable in sustained turns than the A, but climbed better. One Allied pilot in 1946 felt the loss of handling clearly was too great for the gains in performance…
The FW-190A was truly “it” on the Western Front, and was only limited by poor high altitude handling and dreadful high speed handling at any altitude, which made the Me-109G complementary when going high or fast…
In general, the actual performance relationship of all these famous fighters is shockingly misunderstood if my reading of thousands of actual combat accounts is any guide (1300 of them for the P-51 and P-47 can be found in one place if you google “Mike Williams WWII Aircraft Performance”: I did read them all)… I know from discussing this with several Aeronautic engineers that they do not recognize the effect of nose length leverage and the slight thrust slanting (caused by the turn’s curvature causing slight assymetrical thrust compression) to increase the wingload when the prop’s thrust is beaten by tilting it back when changing the angle of attack… This adds easily around 20-30% to the entire wingload, which is why reducing power (or a shorter nose) helps prolonged multiple 360° turning at low speed… The nose location of the thrust is the basic cause of this, and this does not really apply to jets for obvious reasons, which is why the effect is still ignored…
Ignoring the P-38 and P-40, the two most able US and German turn fighters in the West were the FW-190A and the P-47D… Again contrary to the usual dogma, boom and zoom fighting was more an Eastern front and Pacific Theater staple than a Western European one, especially in 1944-45…
Gaston