getting to grips with COLD WEATHER OPERATIONS 寒冷天气运行(27)

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● Automatic system
The ice detection system automatically activates or deactivates the ice protection system,
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according to the status of the icing conditions it senses. Status (detection/no detection,

protection system activated/not activated and failures) is provided to the crew for information.
Note 1: A primary ice detection system can either have manual actuation (by the crew) or
automatic actuation of the ice protection systems. Note 2: An automatic system should be designed as a primary system.
● Intrusive detector
The detector protrudes into the aerodynamic flow. The detector, or its sensitive part, is impinged by the water droplets. These detectors generally sense ice information on their sensitive parts or measure the icing conditions’ characteristics.
● Non intrusive detector
The detector is flush-mounted with the aerodynamic surface. It senses the ice formation or deposit on its sensitive parts, or makes an analysis of the atmosphere characteristics at a distance.
Ice detection systems assist the pilot in operating in icing conditions. They also have the potential of fuel saving, due to the optimization of hot bleed air for NAI/WAI activation. This can be deduced from the fact that, when an ice detection system is used, the ice protection system is only activated when icing conditions are really encountered. When following the conservative AFM procedures, the ice protection system may be activated when no real icing occurs. Statistical studies have shown that the AFM-defined icing conditions may lead to up to 80% of .unnecessary. activation of the ice protection systems.
A3.3.2 The Airbus Dual Advisory Ice Detection System (DAIDS)
The Dual Advisory Ice Detection System is intended to support the pilot in identifying outside meteorological conditions which might lead to ice accumulations on the airframe. In this sense, the meaning of icing conditions is less conservative and more precise than AFM definition, because the icing condition detected by the DAIDS is based on real ice build-up measured by the probes. The location of the DAIDS has been chosen such that two ice detection thresholds can be provided indicating the severity of the icing conditions and allowing the separate activation of the wing and nacelle anti-ice systems.
The operation of the DAIDS can be summarized as follows:
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The flight crew activates and de-activates the Engine and Wing Anti-Ice Systems based on the AFM procedure (TAT < 10 °C and visible moisture).

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The ice detection signal provides the flight crew with an additional indication of icing.

The AFM procedures are not replaced
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The system is operational in flight only (Altitude >= 1500 ft and TAT < 8°C).

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Two warning levels are provided:

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The ICE DETECTED message is generated to activate the engine anti-ice system.

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The SEVERE ICE DETECTED message is generated to activate the wing anti-ice
　
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