From 747 Classic FCTM -
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The following table shows optimum climb vs. gross weight for
min trip fuel.
500,000 lbs (227 tonnes) = 290 KIAS - M. 83
600,000 lbs (273 tonnes) = 305 KIAS - M. 83
700.000 lbs (318 tonnes) = 320 KIAS - M. 83
800.000 lbs (364 tonnes) = 335 KIAS - M. 835
833,000 lbs (377 tonnes) = 338 KIAS - M. 84
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The above speeds are valid for 747-100/200 types.
The 747-300 - requires 10 KIAS and Mach .01 higher speeds.
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Happy contrails