MD-11 Flight Crew Operations Manual
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Ice and Rain Protection -
Description and Operation
Ice.10.2
Wing Anti-Ice System
The wing anti-ice system provides ice protection for the outboard wing slats. Ice
protection is not provided for the inboard slats.
Each wing has 8 leading-edge slats. The outermost slats (4 through 8) are anti-iced
with hot engine bleed air. The bleed air source is either low stage air, high stage
air, or low stage air augmented with high stage air, depending on the engine power
setting.
The bleed air, drawn from the main pneumatic manifold, flows through a stainless
steel duct to the piccolo duct. The piccolo duct, installed in the slats, controls the
anti-ice airflow rate. The anti-ice air is discharged from the piccolo duct and
through double skin passages. After leaving the double skin passages, the air is
discharged overboard at the slat lower trailing edge.
Pushing the WING ANTI-ICE switch to ON before takeoff arms the airfoil
anti-ice system to automatically function when the left and/or right ground sense
mechanism senses flight. The system automatically turns off when the aircraft
lands. An alert warns the flight crew if the system fails to shut off when on the
ground. The slats may be damaged if the anti-ice system is on longer than 15
seconds while on the ground.
During a Center Accessory Compartment (CAC) manifold fail condition, wing
anti-ice is turned off automatically in order to facilitate the automatic manifold
decay check.
The wing anti-ice valves are armed on the ground or open during flight if selected
on. The two wing anti-ice shutoff valves are normally opened and closed with the
WING ANTI-ICE switch on the ANTI-ICE/WINDSHIELD control panel. The
valves open only in flight, when pneumatic pressure is available. Pushing the
WING ANTI-ICE switch opens the wing anti-ice valve. ON illuminates. DISAG
illuminates when the open limit switch is tripped and the switch is off, or the
closed limit switch is tripped and the switch is ON. A WNG A-ICE (L or R)
DISAG alert is displayed.
On the ground, the WNG A-ICE DISAG alert is displayed and the DISAG light
illuminates when an anti-ice valve is open, regardless of the switch position.
If wing anti-ice valve power fails, the valves fail in the closed position.
Tail Anti-Ice System
The tail (horizontal stabilizer) anti-ice system functions in the same manner as the
wing anti-ice system.
Hot engine bleed air from pneumatic system 2 manifold is routed over the
horizontal stabilizer box, diverging to right and left leading edges. Piccolo tubes,
positioned along the leading edges, supply the hot engine bleed air.
October 02, 2006
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