What is the function of TRUs when two are installed?

What is the function of TRUs when two are installed?

• A. They provide DC power to the DC buses; if one TRU is offline, the other maintains DC power to essential/nonessential buses.
• B. They convert AC to AC for avionics.
• C. They regulate cabin lighting.
• D. They manage fuel pumps.

Answer: (A)

Transformer Rectifier Units convert AC power into DC power to feed the DC buses. When two TRUs are installed, they share the load and provide redundancy so that essential and nonessential DC buses remain powered if one TRU goes offline. In other words, the system is built so a single TRU can still supply the necessary DC power, maintaining avionics and other critical systems. TRUs don’t convert AC to AC, regulate cabin lighting, or manage fuel pumps, which is why the other functions aren’t correct.

Transformer Rectifier Units convert AC power into DC power to feed the DC buses. When two TRUs are installed, they share the load and provide redundancy so that essential and nonessential DC buses remain powered if one TRU goes offline. In other words, the system is built so a single TRU can still supply the necessary DC power, maintaining avionics and other critical systems. TRUs don’t convert AC to AC, regulate cabin lighting, or manage fuel pumps, which is why the other functions aren’t correct.