What is the required OAT for the cowl anti-ice function to be ON during ground operations?

The request to have the cowl anti-ice function ON during ground operations is critically determined by the Outside Air Temperature (OAT). For the CRJ 900, the requirement is to activate the cowl anti-ice when the OAT is at or below 10°C (50°F). This temperature threshold is established because the risk of ice accumulation on engine cowlings increases as the temperature approaches freezing, especially when conditions are conducive to moisture in the air, such as during takeoff or taxiing in cloudy or wet conditions.

Operating with the cowl anti-ice system ON at this temperature helps ensure safe engine performance by preventing ice formation that could lead to engine stall or other performance issues. Above this temperature, the risk is significantly reduced, making the activation of the cowl anti-ice unnecessary and potentially wasting energy and system resources.