I am extremely skeptical of that claim. It might be true for the original 747-100 (with GE’s first turbofan engine) in unfavorable conditions, but it certainly isn’t for any 747 made in the last 40 years with even a semi-optimal flight plan.
Wikipedia gives the TSFC of Concorde’s Rolls-Royce 593 engines as 1.195 lb/lbf-hr and 0.6 lb/lbf-hr for a 747-400’s Rolls-Royce RB211. So that’s 45% less fuel burn per pound of thrust in favor of the 747.
Furthermore, drag increases as the cube of airspeed (which corresponds to fuel per mile scaling as speed squared). That means at constant air density, Concorde would consume (2.37)^2 = 5.6 times more fuel (not accounting for the difference in engines)
A 747 cruising very low at 30k feet would have ~4 the air density to contend with, but even that doesn’t make up for the speed difference. 747-400’s routinely cruise at over 40k feet…
Unfortunately, you can’t just wave your hands and shout “supersonic turbofan”, because high bypass ratios (what accounts for subsonic efficiency gains since the 1960’s) are incompatible with supersonic flight.
Edit, one more thing: The General Electric GEnx found on modern 747-8’s are 15% more efficient than the old 747-400’s engines!
What is true is that a Concorde flying at subsonic speeds is more efficient per passenger mile than a 747. But that’s mostly due to the very high fineness ratio and drag-reduction-above-all-else design philosophy.
Wikipedia gives the TSFC of Concorde’s Rolls-Royce 593 engines as 1.195 lb/lbf-hr and 0.6 lb/lbf-hr for a 747-400’s Rolls-Royce RB211. So that’s 45% less fuel burn per pound of thrust in favor of the 747.
Furthermore, drag increases as the cube of airspeed (which corresponds to fuel per mile scaling as speed squared). That means at constant air density, Concorde would consume (2.37)^2 = 5.6 times more fuel (not accounting for the difference in engines)
A 747 cruising very low at 30k feet would have ~4 the air density to contend with, but even that doesn’t make up for the speed difference. 747-400’s routinely cruise at over 40k feet…
Unfortunately, you can’t just wave your hands and shout “supersonic turbofan”, because high bypass ratios (what accounts for subsonic efficiency gains since the 1960’s) are incompatible with supersonic flight.
Edit, one more thing: The General Electric GEnx found on modern 747-8’s are 15% more efficient than the old 747-400’s engines!
What is true is that a Concorde flying at subsonic speeds is more efficient per passenger mile than a 747. But that’s mostly due to the very high fineness ratio and drag-reduction-above-all-else design philosophy.