DC service switch powers which systems?

DC service switch powers which systems?

• A. Navs, Lavs, Dome and Beacon
• B. Primary flight controls
• C. Engine ignition
• D. Cabin lights

Answer: (A)

The main idea here is understanding what the DC service switch powers. This switch controls a nonessential service bus that provides power to loads used for servicing and passenger comfort, not for flight-critical functions. The items on that bus are navigation lights, lavatories, the overhead dome light, and the beacon. These are things you’d want powered for ground operations or preflight checks, but they aren’t required to fly and aren’t part of the essential flight power system. Primary flight controls and engine ignition must stay on power from the essential systems, so they aren’t driven by the DC service switch. Cabin lights, while related to the interior, are typically fed by other circuits and aren’t the focus of this service-switch set.

The main idea here is understanding what the DC service switch powers. This switch controls a nonessential service bus that provides power to loads used for servicing and passenger comfort, not for flight-critical functions. The items on that bus are navigation lights, lavatories, the overhead dome light, and the beacon. These are things you’d want powered for ground operations or preflight checks, but they aren’t required to fly and aren’t part of the essential flight power system. Primary flight controls and engine ignition must stay on power from the essential systems, so they aren’t driven by the DC service switch. Cabin lights, while related to the interior, are typically fed by other circuits and aren’t the focus of this service-switch set.