How long must you wait after energizing the EICAS before starting the APU?

The correct answer is based on the specific operational procedures established for the CRJ aircraft. After energizing the Engine Indication and Crew Alerting System (EICAS), it is important to allow a minimum of 30 seconds before starting the Auxiliary Power Unit (APU). This waiting period ensures that the EICAS has enough time to complete its initial system checks and diagnostic routines. It allows the crew to have a fully operational EICAS, which provides critical information on the aircraft's systems and alerts, ensuring a safe start of the APU. This procedure contributes to the overall safety and workflow efficiency during ground operations.