APU Running but electrical power not available

[Will]

Hi everyone,

Yesterday I selected the APU ON after landing, and it was eventually running and supplying bleed air, but neither of the AVAIL lights illuminated on the overhead electrical power panel. There was no electrical power coming from the APU.

I solved the problem by turning off the APU, waiting a few minutes, and then turning it on again--when I did that, the AVAIL lights illuminated and electrical power was available as normal. I suppose I could have tried cycling the generator field switches too, but I didn't do that. There weren't any malfunctions active, and no circuit breakers were out.

What could I have done to make this condition happen (APU running, no electrical power)? I haven't seen it before.

Thanks.

[ASCTU744]

Are you able to recreate it? And did you have any malfunctions on that flight?

[John H Watson]

Same thing just happened to me. I had to cycle the generator field switches.

I thought I saved the situ (before the field reset), but must have pushed the wrong instructor page buttons.

It was after an Autoland, so I made sure there wasn't something strange going on with bus isolation. Aircraft was at a standstill on the runway with engines at idle.

I may have done a java update before running the sim.

 

[ASCTU744]

Maybe you forgot to turn off the APU after start: https://aerowinx.com/board/index.php?topic=2973.0

[Will]

I turned off the APU after start, and anyway, didn't PSX 10.0.5-beta9 change the issue? If I read that thread correctly, Hardy modified the logic so that the AVAIL lights would extinguish on takeoff with the APU running, but would illuminate again upon landing. I think? (But that is a helpful and informative thread, thanks for linking to it.)

I didn't Autoland like John, but nothing was abnormal about the flight. No malfunctions, and anyway restarting the APU resolved the issue. I taxied to the gate to troubleshoot, kept the engines running, cycled the APU (which then worked as expected), and then shut down the aircraft as usual with no further abnormalities.

[John H Watson]

Maybe you forgot to turn off the APU after start

The APU selector was in OFF on landing. I hadn't used PSX for a while and possibly loaded the last update in the meantime. Maybe some kind of double reboot was necessary.