Equation 6 · Part 2 · Flight at the Energy Floor: Transport Selection to 2100
Symbol D
What this part means
the lift-to-drag ratio, and .
Its job in the formula
D is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.
Full expression→Symbol D→Article meaning
Where the article explains it
where a is the local speed of sound, M is cruise Mach number, g is standard gravity, is thrust-specific fuel consumption, L/D is the lift-to-drag ratio, and and are the aircraft’s weight at the start and end of the cruise segment [ 1 ] .
The passage around this formula
where a is the local speed of sound, M is cruise Mach number, g is standard gravity, is thrust-specific fuel consumption, L/D is the lift-to-drag ratio, and and are the aircraft’s weight at the start and end of the cruise segment [ 1 ] . Three of those four factors — speed, engine efficiency, and aerodynamic efficiency — are where a century of aeronautical engineering has already done most of its work and where further gains now come in single-digit percentages per generation, the flattened tail of aviation’s S-curve. The fourth factor, the mass-ratio term , is where the aviation lineage’s entire battery-versus-kerosene argument actually lives, because / is set…
Learn the underlying idea
A variable is a named place for a value. Its letter is a local label: x can mean position in one formula and a data point in another.
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Sources cited in the surrounding passage
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