I'm no guru, but comparing specs over at Baugher's place shows a few things. Comparing the B-17E with the B-24D shows the B-24 could haul half a ton more bombs and go a further 300 miles than the B-17. The B-24 also cruised at 200mph, while the B-17 tooled along around 180mph. Both had a max bomb load of 8,000 lbs, which isn't entirely relevant as you can't carry that big a load very far.
Comparing the B-17G with the B-24J showed roughly the same thing. The B-24J moved a touch faster than the -17G and carried half a ton more bombs in a typical load (4k vs 5k). The B-17G went a tad further though; 1,700 miles for the -24J while the -17G droned on for 1,850 miles. But, the Lib in any version could fly higher. Typically B-17's flew around 25,000 feet, with B-24's moving along up to 5,000 feet higher. The B-17's Wright engines were certified to produce 1,200 hp up to 25,000 ft, while the Pratt & Whitney on the B-24 could maintain that same power setting up to 31,500 ft. I find this odd because aside from the difference in engine makes, both used the same turbo system.
http://home.att.net/~jbaugher2/thirdseriesbombers.html-----------------------
Flakbait [Delta6]
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