For a GPU start at ambient temperatures below approximately -15 C, the DC voltage minimum should be what value?

For a GPU start at ambient temperatures below approximately -15 C, the DC voltage minimum should be what value?

• A. 28V
• B. 24V
• C. 26V
• D. 30V

Answer: (A)

Cold-weather starts demand more robust power to the starter and avionics because the battery and sources have higher internal resistance and the starting current is, therefore, harder to supply. When the ambient temperature falls below about -15 C, the DC bus must be able to deliver enough voltage under load, so the minimum DC voltage for starting the GPU is set at 28 volts. This 28-volt threshold ensures the starter and control circuits receive adequate power even with the extra cold-start stress. A lower value like 24V would risk the voltage sagging below what’s needed during start, and 26V doesn’t provide the required margin for very cold conditions. 30V is higher than the minimum required and is acceptable, but it isn’t the specified minimum for these cold-start circumstances.

Cold-weather starts demand more robust power to the starter and avionics because the battery and sources have higher internal resistance and the starting current is, therefore, harder to supply. When the ambient temperature falls below about -15 C, the DC bus must be able to deliver enough voltage under load, so the minimum DC voltage for starting the GPU is set at 28 volts. This 28-volt threshold ensures the starter and control circuits receive adequate power even with the extra cold-start stress.

A lower value like 24V would risk the voltage sagging below what’s needed during start, and 26V doesn’t provide the required margin for very cold conditions. 30V is higher than the minimum required and is acceptable, but it isn’t the specified minimum for these cold-start circumstances.