Overview
The function of the engine anti–icing system is to keep some of the engine components free of ice. The engine bleed air from the HP bleed port gives intake anti–ice protection. The HP bleed port is found on the external side of the outer fan duct at the top of the engine.
Tt2 Sensor
There is a Tt2 sensor installed at the top of the engine, at the 12 o'clock position of the engine inlet. The Tt2 sensor sends temperature signals to the ECU and uses a sensor heater to prevent icing. The sensor heater receives 28 VDC from the essential busses L ESS BUS and R ESS BUS.
Anti-Ice Control Panel
The anti–ice control panel is installed on the center pedestal of the flight compartment. The left (L) and right (R) ENG pushbutton annunciators (PBA) on the ANTI–ICE control panel, when pushed, turn on the engine anti–icing system. A signal is then sent to the ECUs that the nacelle anti-ice is set ON. The 28 VDC power from the L ESS BUS and R ESS BUS de–energizes the anti–ice solenoid which opens the anti–ice valve and the nacelle anti–icing starts. Power from the 28 VDC essential buses is also supplied to the Tt2 sensor heaters. When the anti–ice PBAs are pushed a second time, the cowl anti–ice valve closes and the nacelle anti–icing stops, and the Tt2 sensor heaters de–energize.
01/18/16
Operation
The engine control system controls the flow of bleed air for nacelle anti–ice through a cowl anti–ice valve and solenoid. Discrete inputs to the ECU come from the ANTI–ICE control panel in the flight compartment. The solenoid opens or closes the cowl anti–ice valve. When the solenoid is de-energized, the valve goes to the open position. Thus, it is made to fail open.
Bleed air is available to the aircraft at all levels of engine operation, and during all flight conditions, but not during engine starts. Anti–icing must be turned off during engine starts.
The FADEC controller supplies ARINC data for display on the anti–ice synoptic page.
The EICAS messages that follow are related to the engine anti-icing system:
| EICAS MESSAGES | LEVEL (COLOR) |
|---|---|
| L ENG ANTI-ICE FAIL | CAUTION (amber) |
| R ENG ANTI-ICE FAIL | CAUTION (amber) |
| L ENG ANTI-ICE ON | ADVISORY (cyan) |
| R ENG ANTI-ICE ON | ADVISORY (cyan) |
| ENG ANTI-ICE ON | STATUS (white) |
System Interface
The engine anti-icing system interfaces with the following systems/components:
- Anti-Ice Control Panel
- Cowl Anti-Ice Valve
- Electronic Control Unit (ECU)
- Inlet Temperature (Tt2) Sensor