What method is used for heating the S-Duct when Engine 2 Anti-ice is active?

The S-Duct's heating mechanism, particularly when Engine 2 Anti-ice is activated, relies on Engine #2 bleed air. This approach utilizes hot air extracted from the engine to prevent ice formation in the duct, which is critical for maintaining optimal airflow and engine performance, especially in adverse weather conditions where icing can occur.

Using bleed air is effective because it provides a consistent and efficient source of heat directly from the engine, ensuring the S-Duct remains within operational temperature limits. The warmth from the bleed air helps melt any potential ice buildup, promoting safe aircraft operation and enhancing performance during critical phases of flight where anti-icing is essential.

In contrast, methods such as fuel heating and electric heating elements serve different functions and may not directly apply to the specific heating process of the S-Duct when the anti-ice system is engaged. Engine #1 bleed air would not be utilized for Heating Engine 2’s S-Duct, as that specifically involves the resources from Engine 2.