Anti-Ice and Rain - Engines

Amendment: Link to Boeing Technical Bulletin regarding high altitude ice crystals. Both TAI indication and EPR adjustment are signalled by switch position - not valve position.

Engine Anti-Ice System

Anti-Icing Control Panel

The Engine anti-ice system uses engine bleed air to provide engine cowl inlet ice protection. Engine anti-ice can be operated in flight or on the ground. The left and right engines have identical, independent anti-ice systems. This allows the remaining system to operate if one engine fails.

The cowl anti-ice valves are electrically controlled and pressure actuated. An open cowl anti-ice valve permits the cowl leading edge to be anti-iced by engine bleed air.

Engine Anti-Ice System Operation

On the ground or in flight, pushing the ENGINE ANTI-ICE switches ON allows engine bleed air to anti-ice the engine cowl inlets.

The engine Thermal Anti-Ice (TAI) annunciation appears above the EICAS N1 indication when an engine anti-ice valve is selected open.

The VALVE light illuminates and the EICAS advisory message L/R ENG ANTI-ICE displays when the engine anti-ice valve disagrees with the switch position.

When the Engine Anti-ice switches are selected ON, the following also occurs:

  • The Engine Idle setting is increased.
  • The Maximum EPR limit is reduced. Note: The adjustment is based on the position of the Switch, not the position of the valve.
  • For flame-out prevention from ice ingestion, Engine Ignition is automatically activated when the Engine Anti-Ice Switch is turned on, provided the Engine Start Selector is in AUTO.

Anti-Ice System Schematic

Anti-ice Schematic (RR).

Thermal Anti-Ice Duct Burst (Pop-Out) Indicator

Thermal Anti-Ice Duct Burst (Pop-Out) Indicator

Some engines have a Thermal Anti-Ice Duct Burst (Pop Out) Indicator installed on the left side of the fan cowling.

Spinner Anti-Ice

Spinner Rubber Tip

Spinner anti-ice is provided by a flexible rubber tip that sheds ice as it oscillates.