When is locked wheel protection deactivated?

• A. Wheelspeed below 10 kt
• B. Wheelspeed below 30 kt
• C. Wheelspeed above 50 kt
• D. Wheelspeed above 70 kt

Answer: (B)

Locked Wheel Protection prevents tire skidding by backing off brake pressure when it detects that a wheel is about to lock. It’s designed to work when the wheel speeds are high enough that a lock would be dangerous, but it shouldn’t interfere with braking when the airplane is moving slowly on the ground. When wheel speed falls below a certain threshold, the protection is disabled so braking can proceed normally without the system trying to modulate pressure for a condition that isn’t a skid threat at very low speeds. That threshold is around 30 knots, so the deactivation occurs when wheels are below 30 kt. The other options describe speeds where the system would still be active or aren’t the standard deactivation point, which is why they aren’t correct.