MD-11 Flight Crew Operations Manual
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Ice and Rain Protection -
Description and Operation
Ice.10.6
The secondary method of detecting ice buildup on the aircraft is the monitoring of
Outside Air Temperature (OAT) and humidity combined with visual inspection of
the aircraft windshield wipers and window frames during flight. This method is
used when both left and right ice detector systems are inoperative.
If one of the two systems fails, the flight crew must act based on the following:
• A single operative ice detector may be used for advisor information only.
• Monitoring of OAT and humidity.
• Visual inspection of windshield wipers and window frames.
If both left and right ice detector systems fail, the flight crew must rely entirely on
the following:
• Monitoring of OAT and humidity.
• Visual inspection of windshield wipers and window frames.
In icing conditions, ice builds up on the sensing probe. The resonant frequency of
the probe then decreases due to the added mass of the ice. When this frequency
shift is sensed by the controller, an ICE alert is displayed if any airfoil or engine
anti-ice switch is not on. Simultaneously, the probe starts to deice itself in
preparation for the next ice detection cycle.
Heaters in the probe are powered for about ten seconds to melt the ice buildup. If
during the next cycle, no ice is detected, a NO ICE DETECTED alert is displayed
if the anti-ice system is commanded on.
An ICE DET SINGLE alert will warn the crew that one of the 2 systems has failed.
An ICE DETECTOR FAIL alert will warn the crew that both ice detection
systems have failed.
Ice detector system faults are stored in the ESC fault review.
System Operation
When electrical power is on, the ice detection system is operative. Powerup of the
aircraft electrical system will automatically initiate a system powerup test. This
test checks the system interface signals, the heater, and the software memory. If
no faults are detected during the powerup test, the ice detection system begins
normal operation for the detection of ice. If a fault is detected during the test, the
ICE DET SINGLE or ICE DETECTOR FAIL alert will be displayed and the ESC
will store the fault in fault review.
The ice detection system is operational on the ground. The system alerts are
inhibited from display during takeoff and landing.
October 02, 2006
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