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

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

• A. 15 sec
• B. 30 sec
• C. 45 sec
• D. 60 sec

Answer: (B)

Waiting 30 seconds after EICAS powers up lets the system complete its initialization and stabilize before you command the APU to start. When EICAS is energized, the aircraft’s displays and associated buses go through boot-up checks and voltage levels settle. Starting the APU during that unsettled phase can cause unreliable monitoring, spurious warnings, or an unstable electrical load on the buses. The 30-second delay provides a safe window for the EICAS to reach normal operation and for the electrical system to settle, ensuring the APU start sequence proceeds with proper monitoring and avoids unnecessary faults. So, the correct timing is 30 seconds.

Waiting 30 seconds after EICAS powers up lets the system complete its initialization and stabilize before you command the APU to start. When EICAS is energized, the aircraft’s displays and associated buses go through boot-up checks and voltage levels settle. Starting the APU during that unsettled phase can cause unreliable monitoring, spurious warnings, or an unstable electrical load on the buses.

The 30-second delay provides a safe window for the EICAS to reach normal operation and for the electrical system to settle, ensuring the APU start sequence proceeds with proper monitoring and avoids unnecessary faults. So, the correct timing is 30 seconds.