ERJ-145 Electrical Practice Test 2026 - Free Electrical Practice Questions and Study Guide

During an electrical emergency, the batteries are relied on to keep essential systems alive while you work to restore power from other sources. The endurance figure for essential power is calculated to include the energy used during APU start attempts, because starting the APU is a standard step to bring generating power back online. For the ERJ-145, the batteries are sized so that essential systems can be powered for about 40 minutes even when you are attempting to start the APU. This gives crews enough time to try to start the APU and, if successful, to bring the generators back on line while maintaining essential flight deck and avionics power. The other durations are not the designed endurance; 40 minutes reflects the aircraft’s emergency battery capability including APU start attempts.