In which position should the DSPLY FAN switch be placed to allow conditioned air to cool the flight deck CRT displays?

The proper position for the DSPLY FAN switch to allow conditioned air to cool the flight deck CRT displays is "STBY." When the switch is in the STBY position, it activates the display cooling fan without the need for the air conditioning system to be fully operational. This ensures that the CRT displays maintain a suitable operating temperature by providing the necessary cooling, thus preventing overheating and allowing for optimal performance.

The "STBY" setting is specifically designed to keep the displays cooled without the additional load of the main cooling system. In contrast, other options like OFF would not provide any cooling airflow. The ON setting does activate the fan, but it is typically used for broader ventilation needs rather than specifically targeting the CRT screens. The COOL setting may imply an active cooling mode, but it is not the designated option for managing the cooling of the CRT displays directly. Therefore, STBY is the most suitable position for this specific purpose.