PSA Airlines CRJ 700 & 900 Systems Practice Test

With DC power only, you’re limited by the available energy in the plane’s DC electrical system and battery. The design provides enough power for essential operations for a short window, but without an additional power source (AC power or APU), the energy would run out and critical systems could be impaired. That’s why the maximum duration for ground operations under DC power alone is five minutes. If you need more time, you must connect external power or start the APU to supply additional power.