Best Angle / Best Rate of Climb

V_X is best angle of climb — the most altitude gained per unit of distance, used to clear obstacles. V_Y is best rate of climb — the most altitude gained per unit of time. With altitude, V_X increases and V_Y decreases until they meet at the absolute ceiling.

Source FAA Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25)↗ · checked 2026-08-25