Editing Thrust-to-weight ratio (section)

===Propeller-driven aircraft===
For propeller-driven aircraft, the thrust-to-weight ratio can be calculated as follows in imperial units:<ref>Daniel P. Raymer, ''Aircraft Design: A Conceptual Approach'', Equations 3.9 and 5.1</ref>
:<math>\frac{T}{W} = \frac{550\eta_\mathrm{p}}{V} \frac{\text{hp}}{W},</math>
where <math>\eta_\mathrm{p}\;</math> is [[propulsive efficiency]] (typically 0.65 for wooden propellers, 0.75 metal fixed pitch and up to 0.85 for constant-speed propellers), hp is the engine's [[shaft horsepower]], and <math>V\;</math>is [[true airspeed]] in feet per second, weight is in lbs.

The metric formula is:
:<math>\frac{T}{W}=\left(\frac{\eta_\mathrm{p}}{V}\right)\left(\frac{P}{W}\right).</math>