At touchdown, wheel lock-up is prevented by the ______.

The anti-skid system is designed to help maintain wheel traction during braking, especially during touchdown. When an aircraft lands, the wheels are subjected to rapid deceleration as the brakes are applied. If too much braking force is applied and the wheels begin to skid or lock up, the anti-skid system automatically modulates the braking pressure on each wheel. This modulation prevents the wheels from locking, allowing them to continue rotating and maintain contact with the runway surface, which is crucial for directional control and stability during landing.

In contrast, while the brake system is essential for decelerating the aircraft, it is the anti-skid system that specifically differentiates between “normal braking” and conditions that could lead to wheel lock-up. The hydraulic system provides the necessary pressure to operate the brakes but does not have the capability to prevent lock-up. The yaw damper primarily helps maintain directional stability and does not play a role in preventing wheel lock during braking. Therefore, the anti-skid system is specifically tailored to prevent wheel lock-up effectively during touchdown.