Thorlifter
Captain
Can your typical airliner (757, A300, etc) break the sound barrier? If so, why don't they fly faster? Not fuel efficient?
Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
Drag increases dramatically when speed gets too close to speed sound. So it can be done (Concord did it for many years), but it's definitely not fuel-efficient.
Discussions of the efficiency of Concorde are confusing. Some people, such as Stanley Hooker, will tell you that Concorde's engines were much more efficient than those of a 747 and of course they were because the high speed supercharged them so they were giving almost twice the thrust per unit of fuel burnt. However, Concorde was flying twice as fast as a 747, so the drag had gone up by a factor of four. Thus Concorde needed to burn fuel at twice the rate of a 747. However, the flight would only last half the time.Most airliners are rated by passenger miles per gallon. When a Concorde was at capacity (they weren't always full), it was rated at 15.8 pmpg. A 707 was 33.3, a 747 was 46.4, a DC-10 was 53.6.
Discussions of the efficiency of Concorde are confusing. Some people, such as Stanley Hooker, will tell you that Concorde's engines were much more efficient than those of a 747 and of course they were because the high speed supercharged them so they were giving almost twice the thrust per unit of fuel burnt. However, Concorde was flying twice as fast as a 747, so the drag had gone up by a factor of four. Thus Concorde needed to burn fuel at twice the rate of a 747. However, the flight would only last half the time.
What hurt Concorde was that they had to land at almost the same speed as a subsonic airliner. Thus they needed wings with about the same wing loading for take off and landing. If they were a cruise missile, they would have suffered much less drag. They could avoid some of the drag by flying higher but then the engines became less efficient as there is less air up there and it is hotter (the lowest temperature is roughly where the 747s fly).
The figures for passenger miles per gallon are distorted because Concorde was all first class.
Most airliners are rated by passenger miles per gallon. When a Concorde was at capacity (they weren't always full), it was rated at 15.8 pmpg. A 707 was 33.3, a 747 was 46.4, a DC-10 was 53.6.
Perhaps you meant it is colder?...They could avoid some of the drag by flying higher but then the engines became less efficient as there is less air up there and it is hotter (the lowest temperature is roughly where the 747s fly)...
The Concord/SST flew at about 16,764m/55,000ft. which puts it just above the tropopause boundary. The temps in this region are around -60C/-76F.