When are the drain masts heated?

The drain masts on the CRJ550 are heated whenever 115V AC power is applied. This heating is essential to prevent ice formation in the drain masts, particularly during ground operations. Ice accumulation could obstruct proper drainage, which is critical to ensure that any water or other fluids can exit the system without issue.

Heating of the drain masts is not solely dependent on the engine start or flight conditions, as this approach ensures the masts are warmed during the ground operations, making them susceptible to freezing even before takeoff. The application of the correct voltage, in this case, 115V AC, is what activates the heating elements in the drain masts. This keeps the system effective and mitigates potential hazards related to ice accumulation.

In contrast, other voltage options mentioned, such as 220V AC, would not be applicable under normal operational circumstances for the heating of the drain masts, as they are specifically designed to function with a 115V AC power source.