How is a typical 28-volt DC aircraft electrical system grounded?

How is a typical 28-volt DC aircraft electrical system grounded?

• A. Grounding is achieved by connecting the system negative to a dedicated external grounding point away from the airframe.
• B. The negative is grounded to a separate negative bus located in the avionics bay.
• C. A common airframe ground point is used with a dedicated grounding strap returning the system’s negative to the airframe.
• D. Grounding is achieved by bonding the positive conductor to the airframe.

Answer: (C)

Ground return for a typical 28V DC aircraft system is provided by a single common ground path to the airframe. The system’s negative conductor is connected to a dedicated grounding strap that ties to a common point on the airframe. This creates a low-impedance, unified return path for all currents, keeping all equipment referenced to the same ground potential and reducing stray currents or interference. Connecting the ground away from the airframe or using a separate negative bus would complicate the return path and risk ground loops. Bonding the positive conductor to the airframe would effectively create a direct short to ground, which is not how the system is designed.

Ground return for a typical 28V DC aircraft system is provided by a single common ground path to the airframe. The system’s negative conductor is connected to a dedicated grounding strap that ties to a common point on the airframe. This creates a low-impedance, unified return path for all currents, keeping all equipment referenced to the same ground potential and reducing stray currents or interference.

Connecting the ground away from the airframe or using a separate negative bus would complicate the return path and risk ground loops. Bonding the positive conductor to the airframe would effectively create a direct short to ground, which is not how the system is designed.