In normal unaccelerated flight, the forces of flight are in what state?

• A. Equilibrium
• B. Acceleration
• C. Deceleration
• D. Balance

Answer: (A)

When a aircraft is in normal, unaccelerated flight, the forces acting on it sum to zero. This means there’s no net force causing it to speed up, slow down, or change direction. In steady flight, the lift pushing up exactly balances the weight pulling down, and the thrust pushing forward exactly balances the drag pulling backward. With these pairs canceling out, the airplane moves with a constant velocity.

The precise term for this state is equilibrium, indicating zero net force and no acceleration. “Balance” is a intuitive idea but the physics phrasing is equilibrium. If the aircraft were accelerating, one would have a nonzero net force (for example, thrust exceeding drag would speed the plane up, or lift not matching weight would change altitude).