Which component failure would most directly affect the DC distribution by causing the DC bus it serves to lose power while the other bus remains powered if online?

Which component failure would most directly affect the DC distribution by causing the DC bus it serves to lose power while the other bus remains powered if online?

• A. TRU failure on a DC bus
• B. Hydraulic pump failure
• C. Engine fire
• D. Flight deck comms failure

Answer: (A)

The key idea is how power is fed to the DC buses. On the ERJ-145, each DC bus is supplied by Transformer Rectifier Units that convert aircraft AC to DC. The buses are designed with redundancy so that if one TRU or one bus fails, the other bus can stay energized as long as its own TRU and the AC source are healthy. When a TRU that serves a particular DC bus fails, that bus loses its DC power because the rectifier that provides it is no longer feeding it. The other DC bus remains powered by its own TRU(s) because that path isn’t affected. This is the most direct way a single component failure can cause one DC bus to go dark while the other bus stays powered. Hydraulic pump failure, engine fire, or flight deck comms failure involve nonessentially tied electrical paths or loads and don’t directly remove power from a specific DC bus in the same direct manner.

The key idea is how power is fed to the DC buses. On the ERJ-145, each DC bus is supplied by Transformer Rectifier Units that convert aircraft AC to DC. The buses are designed with redundancy so that if one TRU or one bus fails, the other bus can stay energized as long as its own TRU and the AC source are healthy.

When a TRU that serves a particular DC bus fails, that bus loses its DC power because the rectifier that provides it is no longer feeding it. The other DC bus remains powered by its own TRU(s) because that path isn’t affected. This is the most direct way a single component failure can cause one DC bus to go dark while the other bus stays powered.

Hydraulic pump failure, engine fire, or flight deck comms failure involve nonessentially tied electrical paths or loads and don’t directly remove power from a specific DC bus in the same direct manner.