Landing Gear Normal Brakes Alternate Brakes Reserve Brakes & Steering Brake Accumulator Autobrakes Parking Brake Brake Units Tyre Serviceability Schematics EICAS Messages

Normal Brakes Show Schematic only

Normal Brakes schematic Alternate Brakes Right Hydraulic system Brake Accumulator Autobrakes Parking Brake
Brake System

Each main gear wheel has a multiple disc brake. The nose wheels have no brakes. The brake system includes:


Normal Brake Hydraulic System

The normal brake hydraulic system is powered by the Right Hydraulic system. The brake pedals provide independent control of the left and right brakes. Pushing a brake pedal opens the respective Brake Metering Valve allowing pressure to pass through Antiskid Valves provided for each wheel.

Gear Retract Braking

AMM When a gear-up signal is detected (left and right landing gears not down and locked), Alternate Brakes system pressure (Left Hydraulic system) stops the main wheels rotating before the gear is retracted into wheel wells. The nosewheels are braked by snubber units in the nose gear wheelwell.

Brake Source

Brake Source Warning The BRAKE SOURCE light illuminates and the EICAS advisory message BRAKE SOURCE displays if both the normal and the alternate brake system pressures are low. The light extinguishes if the Reserve Brakes and Steering system is selected and pressure is available. If the BRAKE SOURCE Light remains illuminated, the Brake Accumulator is the only source of power to the brakes.

QRH If BRAKE SOURCE light remains illuminated:

  • Only accumulator pressure is available for braking. During landing rollout, apply steady, increasing brake pressure and hold to a full stop. Do not taxi.
        [Prevents possible loss of braking due to accumulator depletion]
Antiskid

The normal/reserve brake hydraulic system provides each main gear wheel with individual antiskid protection based on eight separate Wheel Speed Transducer inputs. When a wheel speed sensor detects a skid, the Antiskid Controller signals the appropriate the associated antiskid valve reduces brake pressure until skidding stops, giving maximum braking efficiency.

The alternate brake hydraulic system provides antiskid protection to laterally paired wheels.

Touchdown, hydroplaning, and locked wheel protection is provided.

Non-Normal Indications

Antiskid Warning The ANTISKID light illuminates and the EICAS advisory message ANTISKID displays to indicate a fault is detected in the antiskid system.

The ANTISKID light illuminates and the EICAS advisory message ANTISKID OFF displays to indicate the antiskid system is inoperative.

The light will also illuminate if the Parking Brake is released, but the parking brake valve is not open.

MEL (Antiskid Inoperative) Aircraft braking should be accomplished as follows:

  • Initially, on landing, use partial pedal inputs (approximately one third pedal travel). As the rollout continues, further pedal travel may be necessary.
  • Ensure that the nose wheel is on the ground and the speedbrakes extended before applying brakes.
  • Apply steady pressure and DO NOT PUMP the pedals.
  • Braking requires even greater care during light weight landings.

Alternate Brakes Next