On a climb, thrust required is equal to:

• A. Total Drag + Weight Component
• B. Lift + Drag
• C. Weight alone
• D. Drag alone

Answer: (A)

In a climb, you must balance everything along the flight path. Drag acts opposite the direction you’re moving, and gravity adds a component that resists climbing, equal to W sin(γ) where W is weight and γ is the climb angle. To maintain a steady climb, the thrust has to overcome both of these, so the thrust required is D + W sin(γ). This is larger than in level flight (where γ is 0, so T = D). Lift isn’t directly part of the balance against forward flight, since it acts mainly perpendicular to the flight path, so it doesn’t set the thrust needed to climb.