XVIII Boeing 777 Hydraulic System................................12-42 Left and Right System Description.....................12-43 Center Hydraulic System....................................12-45 Aircraft Pneumatic Systems.......................................12-47 High-Pressure Systems...........................................12-48 Pneumatic System Components .........................12-48 Emergency Backup Systems...............................12-51 Medium-Pressure Systems .....................................12-52 Low-Pressure Systems ...........................................12-52 Pneumatic Power System Maintenance .................12-52 Large Aircraft .........................................................13-30 Shimmy Dampers ...................................................13-32 Steering Damper .................................................13-33 Piston-Type.........................................................13-33 Vane-Type ..........................................................13-33 Non-Hydraulic Shimmy Damper........................13-34 Aircraft Wheels..........................................................13-34 Wheel Construction................................................13-35 Inboard Wheel Half ............................................13-36 Outboard Wheel Half..........................................13-36 Wheel Inspection....................................................13-37 On Aircraft Inspection ........................................13-37 Proper Installation...............................................13-37 Off Aircraft Wheel Inspection ............................13-37 Aircraft Brakes...........................................................13-42 Types and Construction of Aircraft Brakes............13-43 Single Disc Brakes..............................................13-43 Dual-Disc Brakes................................................13-46 Multiple-Disc Brakes..........................................13-46 Segmented Rotor-Disc Brakes............................13-47 Carbon Brakes ....................................................13-51 Expander Tube Brakes........................................13-51 Brake Actuating Systems .......................................13-52 Independent Master Cylinders............................13-52 Boosted Brakes ...................................................13-54 Power Brakes ......................................................13-55 Emergency Brake Systems.....................................13-56 Parking Brake .....................................................13-58 Brake Deboosters................................................13-58 Anti-Skid ................................................................13-61 System Operation................................................13-61 Wheel Speed Sensors..........................................13-62 Control Units ......................................................13-62 Anti-Skid Control Valves ...................................13-64 Touchdown and Lock Wheel Protection ............13-65 Auto Brakes ........................................................13-66 Anti-Skid System Tests ......................................13-66 Anti-Skid System Maintenance ..........................13-66 Brake Inspection and Service .................................13-66 On Aircraft Servicing .........................................13-67 Lining Wear ........................................................13-67 Air in the Brake System......................................13-68 Bleeding Master Cylinder Brake Systems..........13-68 Bleeding Power Brake Systems..........................13-70 Aircraft Landing Gear Systems........................13-1 Landing Gear Types.....................................................13-1 Landing Gear Arrangement......................................13-2 Tail Wheel-Type Landing Gear............................13-3 Tandem Landing Gear ..........................................13-3 Tricycle-Type Landing Gear ................................13-3 Fixed and Retractable Landing Gear........................13-5 Shock Absorbing and Non-Shock Absorbing  Landing Gear............................................................13-6 Leaf-Type Spring Gear .........................................13-6 Rigid .....................................................................13-7 Bungee Cord .........................................................13-7 Shock Struts ..........................................................13-8 Shock Strut Operation ............................................13-12 Servicing Shock Struts ...........................................13-12 Bleeding Shock Struts ............................................13-13 Landing Gear Alignment, Support, and Retraction ...13-15 Alignment...............................................................13-15 Support ...................................................................13-16 Small Aircraft Retraction Systems .........................13-18 Large Aircraft Retraction Systems .........................13-20 Emergency Extension Systems ..............................13-22 Landing Gear Safety Devices.................................13-22 Safety Switch ......................................................13-23 Ground Locks .....................................................13-23 Landing Gear Position Indicators .......................13-24 Nose Wheel Centering........................................13-24 Landing Gear System Maintenance ...........................13-25 Landing Gear Rigging and Adjustment..................13-26 Adjusting Landing Gear Latches .......................13-27 Gear Door Clearances.........................................13-27 Drag and Side Brace Adjustment ......................13-28 Landing Gear Retraction Test ............................13-29 Nose Wheel Steering Systems ...................................13-30 Small Aircraft ........................................................13-30 Chapter 13