MD-11 Flight Crew Operations Manual
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Ice and Rain Protection -
Description and Operation
Ice.10.4
If electrical power to the valve fails, the valve fails open.
Air Data Heater System
The air data sensor heater system consists of integral heating elements within the
pitot tubes, AOA sensors, and the TAT probe. Heaters are also mounted to the
static pressure ports.
A Miscellaneous Systems Controller (MSC) automatically controls, monitors
operation of the air data heater system and provides alerts to the flight crew.
The pitot tubes are installed on the underside of the fuselage. Each pitot tube is
electrically anti-iced with two self-regulating heaters. Each pitot tube heater
contains two elements which may be powered individually or in series. When on
the ground, the elements operate in series to prolong their life
The TAT probe and AOA sensors each contain a single heating element. On the
ground, the TAT probe heater is not powered and the AOA heaters operate from
28-volt ac. In the air, the AOA heaters operate from 115-volt ac.
All static pressure port heaters contain dual heater elements.
The MSC turns on all air data heat (except TAT) when any engine FUEL switch
is moved to ON. The MSC turns these heating systems (except TAT) off when all
three engine FUEL switches are moved to OFF.
The MSC allows the TAT heat to be on only when the ground sense mechanism
senses flight. However, maintenance personnel can override the MSC, as
necessary, with switches on the maintenance panel.
Windshield/Window Anti-Ice and Defog Systems
The clearview windows and aft windows are equipped with a defog system only.
The windshields are equipped with both defog and anti-ice systems.
All cockpit windshields/windows can withstand full airplane pressurization with
one glass pane cracked.
The windshield anti-ice system (which may also be used for backup windshield
defogging) consists of separate, independent, electrically-heated left and right
windshields, selector switches, temperature controllers and temperature sensors.
A controller and sensor maintains the windshield at the correct temperature. The
controller automatically provides ramp warm-up (gradually increasing) power to
the windshield for three to four minutes during initial turn-on to minimize thermal
shock. The controller automatically removes power from the windshield if an
overheat condition occurs.
Windshield anti-ice can be selected on at NORM anti-ice heat or HIGH anti-ice
heat without thermal shock to the windshield.
October 02, 2006
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