You set autobrakes to '3'. What happens to braking force when reverse thrust is applied?

• A. Braking force remains constant
• B. Braking force increases
• C. Braking force varies to maintain constant rate of deceleration
• D. Braking force decreases

Answer: (C)

The autobrake system is designed to achieve and hold a chosen rate of deceleration during landing rollout. When you apply reverse thrust, it adds to the overall braking. To keep the overall deceleration at the programmed rate, the autobrake controller adjusts wheel-brake pressure as needed—reducing braking when reverse thrust provides more braking, or increasing it if reverse thrust is reduced. So the braking force is not fixed; it varies to maintain the constant deceleration rate you selected.