What three electrical sources can be used to start the APU?

What three electrical sources can be used to start the APU?

• A. GPU, Battery 2, Battery 2 assisted by the main generators
• B. GPU, Battery 1, External power
• C. Battery 1, Battery 2, APU
• D. External power, GPU, SHED Bus

Answer: (A)

The APU needs a DC power source to drive its start motor, so on the ERJ-145 you can energize the APU start from three possible sources. First, a Ground Power Unit (GPU) provides immediate external DC power on the ground, which is the most common way to start the APU when the aircraft is on a stand. If no GPU is available, the APU can be started from onboard power using Battery 2. In some situations Battery 2 alone isn’t enough, so the start sequence can be assisted by the main generators, meaning Battery 2 plus the generators together provide the necessary current to turn the APU start motor. This combination covers the typical ground-start options: GPU, Battery 2, or Battery 2 with assistance from the main generators. Battery 1 is not the designated source for starting the APU on this aircraft, and the SHED Bus isn’t used as a primary source for APU start in standard ops.

The APU needs a DC power source to drive its start motor, so on the ERJ-145 you can energize the APU start from three possible sources. First, a Ground Power Unit (GPU) provides immediate external DC power on the ground, which is the most common way to start the APU when the aircraft is on a stand. If no GPU is available, the APU can be started from onboard power using Battery 2. In some situations Battery 2 alone isn’t enough, so the start sequence can be assisted by the main generators, meaning Battery 2 plus the generators together provide the necessary current to turn the APU start motor. This combination covers the typical ground-start options: GPU, Battery 2, or Battery 2 with assistance from the main generators.

Battery 1 is not the designated source for starting the APU on this aircraft, and the SHED Bus isn’t used as a primary source for APU start in standard ops.