What are wheel speed sensors used for in aircraft braking systems?

• A. They measure wheel temperature.
• B. They monitor tire wear.
• C. They provide tire pressure readings to the cockpit.
• D. They provide wheel speed data to the anti-skid/ABS control to modulate brake pressure and prevent wheel lock.

Answer: (D)

Wheel speed sensors provide real-time data on how fast each wheel is turning, and that information goes straight to the anti-skid/ABS control. The system watches for one wheel slowing down much faster than the others—an indication of impending lockup. When that happens, it quickly reduces brake pressure on that wheel and then reapplies it as speed returns, cycling to keep the tire at an optimal slip level. This prevents wheel lock, preserves directional control, and maintains effective braking on the runway. Temperature, tire wear, and tire pressure are measured by other sensors or maintenance checks, not by wheel speed sensors, so their role is specifically to feed the anti-skid system to modulate brake pressure and prevent lock.