Originally Posted by
Stuart Midgley
IIRC, the -100 through -300 had a noticeably higher max cruise than the -400, due to wing changes on the -400 I think? (Please correct me, those who flew them).
The wing was basically unchanged on the -400 (aside from the added winglets - and the winglets didn't really do much) - it was the -8 that got an aerodynamically re-profiled wing. The passenger 747-400 (and -300) had slightly better cruise drag relative to the -100/200 because the longer upper deck resulted in better area ruling at higher Mach numbers. Between about Mach 0.82 and 0.87 it all boiled down to fuel burn vs. speed.
During the 747-8 flight testing, I looked at flight test data from the flutter testing at Mach 0.98+ (presumably in a shallow dive - that was SOP for high speed flutter testing). I don't remember the altitude (it wasn't relevant to what I was looking for in the data - I was just interested in very high Mach number data). I was also on a 747-8 flight test where we cruised for over an hour at 37k/Mach 0.84
with an engine shutdown (granted, we were fairly light).