When should the accessory breakers be ON?

When should the accessory breakers be ON?

• A. Before priming
• B. After cranking the engine and starting
• C. After the engine has run for 5 minutes
• D. After cranking the engine and successfully starting the engine.

Answer: (D)

During starting, the starter motor demands a large burst of current from the battery. If nonessential electrical loads are connected through the accessory breakers, they add to that demand and can cause a voltage drop or a sluggish crank, making it harder to start. Keeping the accessory breakers OFF during cranking reserves the battery current for the starter. Once the engine has cranked and is running, the generator or alternator takes over supplying power. At that point, you can safely switch on the accessory breakers to power avionics and other equipment without risking a failure to start. This sequencing protects the starting effort and ensures electrical systems are powered only when the engine can sustain them.

During starting, the starter motor demands a large burst of current from the battery. If nonessential electrical loads are connected through the accessory breakers, they add to that demand and can cause a voltage drop or a sluggish crank, making it harder to start. Keeping the accessory breakers OFF during cranking reserves the battery current for the starter.

Once the engine has cranked and is running, the generator or alternator takes over supplying power. At that point, you can safely switch on the accessory breakers to power avionics and other equipment without risking a failure to start. This sequencing protects the starting effort and ensures electrical systems are powered only when the engine can sustain them.