Auto brake valve Park Brake Antiskid controller Antiskid Metering valve Metering valve Antiskid valves Antiskid valves Antiskid return Accumulator Accumulator isolation valve Park brake  valve Right  hydraulic system Alternate brake press P a r k b r a k e AUTO BRAKE  OFF 1 2 4 Max Auto Disarm 3 Auto Brakes OFF Anitskid ON 2 3 4 5 1 0 Brake Press Figure 13-112.  The Boeing 757 normal brake system with auto brake and antiskid. Lining Wear On Aircraft Servicing 13-67 Brake lining material is made to wear as it causes friction  during application of the brakes. This wear must be monitored  to ensure it is not worn beyond limits and sufficient lining  is available for effective braking. The aircraft manufacturer  gives specifications for lining wear in its maintenance  information. The amount of wear can be checked while the  brakes are installed on the aircraft.  Inspection and servicing of aircraft brakes while installed  on the aircraft is required. The entire brake system must be  inspected in accordance with manufacturer’s instructions.  Some common inspection items include: brake lining wear,  air in the brake system, fluid quantity level, leaks, and proper  bolt torque. 