DRAIN AND WATER SUPPLY LINE HEATING -WASTE TANK DRAIN LINE HEATERS -FUNC. DESC.
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BOEING PROPRIETARY -Copyright # -Unpublished Work -See title page for details.
ICE DETECTION SYSTEM -INTRODUCTION
Purpose
The ice detection system (IDS) supplies information about ice conditions to the wing anti-ice (WAI) and the engine anti-ice (EAI) systems.
General Description
The IDS has two ice detectors that operate independently. The left detector connects to the ARINC buses through the left EAI ACIPS card. The right detector connects to the ARINC buses through the right EAI ACIPS card.
Each ice detector has a circuit that calculates when the EAI systems should be on or off and a circuit that calculates when the wing anti-ice system should be on or off. The circuits give separate signals to the EAI ACIPS control cards.
On the ground, the signals are inhibited (ground mode).
In the air, the ACIPS control cards use the signals to control the applicable anti-ice systems and EICAS messages (air mode). The ice signal to the EAI system occurs first (ice detected for a short period of time). If ice is detected for a longer period of time, the ice signal goes to the WAI system. When no ice is detected for more than three minutes, the detectors remove thee ice signals to the EAI and the WAI systems.
All ACIPS control cards get information from both ice detectors, directly or through the ARINC 629 buses. An ice signal from either detector is used for control and indication.
See the wing anti-ice section for more information about the wing anti-ice system (SECTION 30-11). See the engine anti-ice section for more information about the engine anti-ice system (SECTION 30-21).
BITE circuits in the ice detectors monitor the condition of internal functions. BITE circuits in the left and right EAI ACIPS control cards make the detectors do a test when the detectors first get power and periodically do a test of these interfaces:
*
Power to the detectors
*
Output signals (ice for engine, ice for wing and fault).
The AIMS gives information about the system through the EICAS display, status display, and the ice protection maintenance page. You use the MAT to do a ground test for the system and to see maintenance messages.
The IDS has these other interfaces:
*
Air ground system (AGS)
*
Electrical load management system (ELMS).
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ICE DETECTION SYSTEM -INTRODUCTION
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ICE DETECTION SYSTEM -ICE DETECTORS
Purpose
The ice detectors monitor for ice conditions and supply the information to the airfoil and cowl ice protection system (ACIPS).
Location
The ice detectors are on the left and right sides of the nose section of the fuselage (STA 209 WL 162).
Physical Description
The left and right ice detectors are the same. The detectors have these parts:
*
Electrical connector
*
Housing
*
Circuit cards, internal to the housing
*
Microprocessor, internal to the housing
*
Probe (sensing-element) with a heater
*
Strut.
The detectors are LRUs, they have no parts that are LRUs.
Functional Description
Each ice detector operates independently. The ice detector probe vibrates at approximately 40,000 Hz. The probe vibrates at a lower frequency when it collects ice. A heater for the probe turns on when the probe vibrates less than 39,867 Hz. The heater stays on until the probe vibration returns to its usual value or the heater operates for 25 seconds. The usual time that the heater is on is 5 -7 seconds. If the heater is on for 25 seconds, the heater turns off, and a fault condition is latched.
Control logic in the detector counts the number of heater on to off cycles.
If there are two or more cycles, and the airplane is in the air, the ice detector gives an engine icing signal to the ACIPS. The detector also gives an engine icing signal if the airplane is in the air, and the heater is on for 15 seconds or more.
If there are ten cycles and the airplane is in the air, the detector gives a wing icing signal to the ACIPS.
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