The thrust of a turbofan engine decreases as the flight velocity increases. The maximum thrust of the Rolls-Royce RB211 turbofan at zero velocity at sea level is 50,000 lb. Calculate the thrust at an altitude of 3 km at Mach 0.6.
\[\frac{T}{T_{V=0}} = 0.369M_{\infty}^{-0.305}\]\[\Rightarrow T_{3\,km} = 50000\left \{ 0.369\left ( 0.6 \right )^{-0.305} \right \} = 21560.57\,lb\]
