With power to the bus and the fuel selector switched to the right-hand tank, how many relays in the system are operating?

With power to the bus and the fuel selector switched to the right-hand tank, how many relays in the system are operating?

• A. One
• B. Two
• C. Three
• D. Four

Answer: (C)

With power on the bus, the master relay closes, letting energy flow to the fuel system relays. Switching the fuel selector to the right-hand tank completes the control paths for the right side, energizing two more relays: one that powers the right-hand electric pump and another that controls the right-tank portion of the fuel selector/transfer valve to route fuel from that tank. So three relays are active: the master relay, the right-hand pump relay, and the right-side valve/transfer relay.

With power on the bus, the master relay closes, letting energy flow to the fuel system relays. Switching the fuel selector to the right-hand tank completes the control paths for the right side, energizing two more relays: one that powers the right-hand electric pump and another that controls the right-tank portion of the fuel selector/transfer valve to route fuel from that tank. So three relays are active: the master relay, the right-hand pump relay, and the right-side valve/transfer relay.