When does the L/R FUEL XFR PRESS LO annunciator illuminate?

The L/R FUEL XFR PRESS LO annunciator illuminates when the pressure in the fuel transfer lines drops below 5.0 +/- 0.5 psi. This means that the system is monitoring the pressure necessary for fuel to be effectively transferred from the mid tanks to the wing tanks. Maintaining adequate pressure is crucial for ensuring that fuel can flow properly; if the pressure is too low, it could indicate a problem with the fuel transfer system or insufficient fuel flow, which might lead to fuel starvation in the engine.

When the pressure is within the acceptable range, fuel transfer can occur efficiently. If the pressure falls below the specified threshold, the annunicator alerts the crew that the transfer process is compromised and needs attention. Understanding this context is critical for preemptive troubleshooting and ensuring safe operations during flight.