MD-11 Flight Crew Operations Manual
k
Landing Gear and Brakes -
Description and Operation
Land.10.6
Automatic Brake System (ABS)
The ABS automatically applies the brakes during landing and rejected takeoff.
The system consists of an AUTO BRAKE control panel on the forward pedestal,
an amber ABS DISARM light on each side of the glareshield, two Integrated
Brake Control Valves (IBCV), and an autobrake control unit.
Hydraulic systems 1 and 3 are required for normal auto brakes.
In the landing mode, the ABS operates from both brake system 1 (hyd sys 1) and
brake system 2 (hyd sys 3) and provides selection of one of three modes: MIN,
MED, or MAX. ABS is available in HIGH deceleration rates. With the AUTO
BRAKE selector in the MIN and MED position, the system compares actual
aircraft deceleration data obtained from the Inertial Reference Units (IRU) with
the selector position. The system then maintains a constant level of deceleration.
In the MAX position, maximum pressure from brake system 1 and 2 is applied to
the brakes by both of the IBCVs. The maximum individual brake pressure is
reduced only by anti-skid operation. Maximum deceleration is achieved.
The ABS landing mode is armed after the gear is down prior to landing by
selecting the deceleration level desired. Arming of the ABS requires:
• ABS operative (no system failure).
• Deceleration level selected prior to landing.
• Anti-skid armed and operational.
• IRU1 and IRU2 operational.
• Flaps more than 28 degrees.
The ABS landing mode is activated when the spoilers are deployed automatically
or manually with throttles retarded to the idle position and brake pedals released.
Automatic braking is delayed after spoiler deployment for about 1 second in MAX
position and 3 seconds in MIN and MED positions. This allows for a normal
nosewheel touchdown.
Pilot takeover can be initiated at any time and ABS will disarm if:
• Brake pedal is depressed beyond about 40 percent travel (ABS DISARM
lights illuminate).
• Throttle 1 or 3 is advanced beyond 5 degrees (ABS DISARM lights
illuminate).
• AUTO BRAKE selector is placed in OFF position (ABS DISARM lights
do not illuminate).
The ABS will also disarm and ABS DISARM lights will illuminate if flaps are less
than or equal to 28 degrees when spoilers are deployed.
October 02, 2006
To Next Page
Loading...