NOTE:LEFT ICE DETECTOR PROBE SHOWN, RIGHT PROBE OPPOSITE.
Ice Detection System - Component Location Figure 1
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C. If the heater cannot melt the ice after 25 seconds, or if the internal temperature of the ice detector exceeds 300° F, the heater and the detector outputs are automatically deactivated.
D. Each ice detector provides an output to activate the corresponding left or right side engine anti-ice systems, and a separate output to activate the wing anti-ice system at a different level of ice buildup than the engine systems. Computations for identifying icing conditions and for activating anti-ice systems are performed in the ice detector.
3. Anti-Ice/Rain Removal Module
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A. The anti-ice/rain removal module is located on the P5 pilots' overhead panel (AMM 30-11-00, AMM 30-21-00). The module includes four NACELLE ANTI-ICE switches and one WING ANTI-ICE switch. Each switch has 3 positions to place the corresponding anti-ice system on, off, or in automatic mode under control of the ice detection system.
4. Operation (Fig. 2)
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A. Functional Description
(1)
As ice builds up on the ice detector sensor element during flight, the resonant frequency of the sensing element decreases. When a
0.02 |0.005 inch ice layer accumulates, the heater turns on to melt the ice. When the resonant frequency returns to its initial value, the heater turns off, normally 7-8 seconds after it turns on. This process is repeated as long as icing conditions exist. The ice detector keeps count of the number of icing/de-icing cycles of the sensor element.
(2)
When 2 consecutive probe icing/de-icing cycles are counted, the detector outputs a signal to activate the engine anti-ice system for 180 |10 seconds. If an additional icing/de-icing cycle occurs during this time interval, the 180-second engine anti-ice activation period is begun again.
(a) If it takes more than 15 seconds to melt the ice on the first icing/de-icing cycle, the ice detector will activate the engine anti-ice system for 180 |10 seconds without waiting for a second cycle.
(3)
When 10 consecutive probe icing/de-icing cycles are counted, the detector outputs a signal to activate the wing anti-ice system for 180 |10 seconds. If an additional icing/de-icing cycle occurs during this time interval, the 180-second wing anti-ice activation period is begun again.
(4)
If the wing anti-ice control switch has been placed in the OFF position, or a wing anti-ice valve does not open for any other reason, the EICAS advisory message >ICING WING is displayed when the ice detector tries to activate the wing anti-ice system.
(5)
If any nacelle anti-ice control switch has been placed in the OFF position, or an engine anti-ice control valve does not open for any reason, the EICAS caution message >ICING NAC is displayed when the ice detector tries to activate that engine inlet anti-ice system.
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ENGINE TAI SYSTEMS
WING TAI
(30-21-00)SYSTEM (30-11-00)
P415 RIGHT POWER M6703 RIGHT ICE
WING TAI
DISTRIBUTION CENTER DETECTOR SYSTEM E2-6 ELECTRONICS SHELF (30-11-00)
ENGINE TAI SYSTEMS (30-21-00)
Ice Detection System Schematic
Figure 2
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(6)
If any wing or nacelle anti-ice control switch has been placed in the ON position, the corresponding EICAS advisory message >ANTI-ICE WING or >ANTI-ICE NAC is displayed when total air temperature exceeds 54° F (12° C). If an ice detector probe fails, the EICAS status message ICE DETECTOR L or ICE DETECTOR R is displayed. If both ice detector probes fail, the EICAS advisory message >ICE DETECTORS is also displayed.
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