How does a TRU failure affect the DC distribution?

How does a TRU failure affect the DC distribution?

• A. The DC bus serviced by that TRU will lose DC power; the other TRU may keep it powered if still online.
• B. All DC buses fail and require external power.
• C. The DC bus automatically transfers to the standby battery.
• D. The remaining TRU powers the entire DC system automatically.

Answer: (A)

TRUs are the power sources for the DC distribution, and each TRU feeds a specific DC bus (with some systems designed to allow sharing if needed). When one TRU fails, the DC bus it powers loses its power source and goes dark unless the other TRU is online and connected to that same bus through a crossfeed or tie. If the remaining TRU is online and capable, it can continue supplying power to that bus, so not all DC power is lost. So, the DC bus served by the failed TRU loses DC power, while the other TRU may keep it powered if it’s still online.

TRUs are the power sources for the DC distribution, and each TRU feeds a specific DC bus (with some systems designed to allow sharing if needed). When one TRU fails, the DC bus it powers loses its power source and goes dark unless the other TRU is online and connected to that same bus through a crossfeed or tie. If the remaining TRU is online and capable, it can continue supplying power to that bus, so not all DC power is lost.

So, the DC bus served by the failed TRU loses DC power, while the other TRU may keep it powered if it’s still online.