EASY way :)
Given: Aeroplane mass: 50 000kg. Lift/Drag ratio: 12. Thrust per engine: 60 000N. Assumed
g: 10m/sē. For a straight, steady, wings level climb of a twin engine aeroplane, the allengines
climb gradient is:
just :
(T - D)/W = sin alpha !!!
T (thrust) = number of engines (2) * they thrust (60 000 N) = 120 000 N
W (weight) = aeroplane mass (50 000kg) ! * 10g (m/sē) = 500 000 N
D (drag) = W/ (Lift/Drag) -> 500 000 / 12 = 41666
so !
-> (120 000 - 41666) / 500 000 = 0,156668
result * 100 (to get %) = 15,6668 -> 15,7% !