From what I recall, the B-29's were capable of cruising at around 310-320 mph at altitudes of about 33000' when operating out of Burma and China, with operations shifting to Tinian owing to logistical issues. While I'm not sure when the operational altitudes of the B-29 were reduced from 33000' to 31500', whether this was before the move to Tinian (and what effect this had on payload), and seemed that once Iwo Jima was occupied: Fighter escorts started to be employed out of there by P-51D's, then P-47N's (I'm not sure if any P-47D's were used, and I'm not sure how many P-47N sorties were flown) and P-51H's.
I'm curious about escort missions were flown over the Pacific/Japan versus over Europe: Superficially, I'd imagine they'd be easier for the P-51's because of the need to burn down much of the center-tank prior to using the drop-tanks and, since you'd be several hundred miles from enemy territory (IIRC: Iwo Jima to Tokyo is about 750 miles), you could burn up much of (if not all of) the external tanks prior to engaging in combat. Because the B-29's aren't slower than the P-51's, S-weaving wouldn't be necessary, so you could fly a straight path instead of a flight path that looks like a sine-wave.
That said, the B-29's have a higher cruise speed than the P-51D (I have no idea what the cruise speed of the P-47N and P-51H were) which flew around 300-305 mph on long escort tactics up to that point (over Europe) favored escorts flying (IIRC) from 2000'-5000' above the height of the bombers (which would have called for escort altitudes ranging from 33500'-38500'): I'm curious if the elimination of the S-weave, potential ability to retain drop-tanks longer, and the presence of 165 gallon tanks appearing in theater allowed them to simply push the speed up without too much cost; I'm also curious if they used the same escort altitude requirements, or used lower ones? From what I remember, the P-51B's (and most -C's) used the V-1650-3, and the later -C's and P-51D's using the V-1650-7 and, while both engines were capable of cruising well above their critical altitudes (As I understand it: Fuel/air ratios will see lower fuel burn and, provided you could still hold the cruise speed with enough surplus to accelerate to a suitably high speed, one should be decent provided you're able to perform better than enemy aircraft): The V-1650-3 had higher critical altitude (w/o ram: 24000'; w/ ram: 29800') than the -7 (w/o ram: 19000; w/ ram: 24000-25000'). While the -7 had more overall horsepower than the -3, meaning that you'd equal the -3 at some point above the -7's rated altitude: It stands to reason that you would lose a greater degree of performance by the time you got into low 30000' range, where both engines were above their rated altitudes and seems to make escorts at altitudes over 34000'-35000' seem kind of tough (Interestingly, I do remember seeing a document on Greg's Planes and Automobiles that showed that there were kits that allowed the -3's supercharger gearing to be fitted to the -7's), though the P-51H had better altitude performance, and the P-47N was probably the best (IIRC the P-47N-5RE could produce 2100 HP @ 38750'), though it wasn't generally as agile as the P-51's.
I'm curious about escort missions were flown over the Pacific/Japan versus over Europe: Superficially, I'd imagine they'd be easier for the P-51's because of the need to burn down much of the center-tank prior to using the drop-tanks and, since you'd be several hundred miles from enemy territory (IIRC: Iwo Jima to Tokyo is about 750 miles), you could burn up much of (if not all of) the external tanks prior to engaging in combat. Because the B-29's aren't slower than the P-51's, S-weaving wouldn't be necessary, so you could fly a straight path instead of a flight path that looks like a sine-wave.
That said, the B-29's have a higher cruise speed than the P-51D (I have no idea what the cruise speed of the P-47N and P-51H were) which flew around 300-305 mph on long escort tactics up to that point (over Europe) favored escorts flying (IIRC) from 2000'-5000' above the height of the bombers (which would have called for escort altitudes ranging from 33500'-38500'): I'm curious if the elimination of the S-weave, potential ability to retain drop-tanks longer, and the presence of 165 gallon tanks appearing in theater allowed them to simply push the speed up without too much cost; I'm also curious if they used the same escort altitude requirements, or used lower ones? From what I remember, the P-51B's (and most -C's) used the V-1650-3, and the later -C's and P-51D's using the V-1650-7 and, while both engines were capable of cruising well above their critical altitudes (As I understand it: Fuel/air ratios will see lower fuel burn and, provided you could still hold the cruise speed with enough surplus to accelerate to a suitably high speed, one should be decent provided you're able to perform better than enemy aircraft): The V-1650-3 had higher critical altitude (w/o ram: 24000'; w/ ram: 29800') than the -7 (w/o ram: 19000; w/ ram: 24000-25000'). While the -7 had more overall horsepower than the -3, meaning that you'd equal the -3 at some point above the -7's rated altitude: It stands to reason that you would lose a greater degree of performance by the time you got into low 30000' range, where both engines were above their rated altitudes and seems to make escorts at altitudes over 34000'-35000' seem kind of tough (Interestingly, I do remember seeing a document on Greg's Planes and Automobiles that showed that there were kits that allowed the -3's supercharger gearing to be fitted to the -7's), though the P-51H had better altitude performance, and the P-47N was probably the best (IIRC the P-47N-5RE could produce 2100 HP @ 38750'), though it wasn't generally as agile as the P-51's.
