What is the function of the wheel brake master cylinder in a hydraulic braking system?

• A. Converts rudder pedal or toe brake input into hydraulic pressure to actuate calipers and apply braking force.
• B. Converts air pressure into brake pad wear.
• C. Stores hydraulic fluid for the braking system.
• D. Controls anti-skid logic.

Answer: (A)

Pressing the toe brake turns into hydraulic pressure because the wheel brake master cylinder converts mechanical input into fluid pressure that operates the brakes. As you push the pedal, the master cylinder piston moves and compresses brake fluid in the line, sending pressure to the wheel brake calipers. That pressure makes the caliper pistons push the brake pads against the rotors, creating friction to slow the wheel. In many aircraft, there are dual circuits for safety, so if one circuit leaks, the other can still provide braking. The master cylinder is about generating and delivering pressure, not about storing fluid (that’s the reservoir’s job) or handling anti-skid logic, which is managed by ABS/ASR systems.