What is the function of wheel speed sensors in the landing gear/braking system?

• A. They provide wheel speeds to anti-skid and autobrake systems and can feed data for gear status indications.
• B. They measure airspeed to adjust landing gear retraction.
• C. They detect gear position for landing gear doors only.
• D. They supply hydraulic pressure to wheel brakes.

Answer: (A)

Wheel speed sensors deliver real-time rotation data for each wheel, which is essential for braking control. The anti-skid system uses these wheel speeds to detect that a wheel is about to skid (rapidly slowing while others keep turning) and immediately modulates brake pressure to prevent wheel lock while maintaining steerability. The autobrake system also relies on wheel speed information to control braking force and achieve a desired deceleration profile during landing or an aborted takeoff.

In addition, the wheel speed signals can feed cockpit indicators or gear-status logic to help confirm gear and wheel conditions (such as whether the wheels are rotating after touchdown or provide related status information).

They do not measure airspeed (that’s done by the air data system), they do not determine gear position for door operation (that uses gear position sensors), and they do not supply hydraulic pressure to brakes (that’s handled by the hydraulic braking system and valves).