What is the Breguet range equation and what does it tell us?

The Breguet range equation R = (V/SFC) * (L/D) * ln(Wi/Wf) calculates maximum range for jet aircraft, where V is velocity, SFC is specific fuel consumption, L/D is lift-to-drag ratio, Wi is initial weight, and Wf is final weight. It shows range depends on: aerodynamic efficiency (L/D), propulsive efficiency (1/SFC), structural efficiency (fuel fraction through Wi/Wf), and cruise speed. For maximum range, aircraft should fly at speed for best L/D/SFC combination and maximize fuel fraction. This equation guides design decisions and operational planning.