Yep this appears to be an issue/bug with the APU shutdown process.
Starting with the aircraft (v1.0.8) cold and dark w/ the default 6000kg of fuel in the left and right outer tanks:
- Connect Batteries 1, 2, and 3
- Connect Ground Power
- APU Master ON
- APU Start ON
- Wait for APU to spool up
- Review APU LVARS: INI_apu_n1=100, INI_apu_PSI=10, INI_apu_RUN=1, INI_apu_egt=479.99, INI_APU_CONSUMPTION=300, INI_apu_available=1
- APU Master OFF.
APU Running ECAM is removed. N1 starts decreasing until it suddenly drops to 0. APU N1 then proceeds to spool up again before announcing AVAIL. N1 falls to 31, EGT falls to 150.
- Review APU LVARS: INI_apu_n1=100, INI_apu_PSI=3.15, INI_apu_RUN=1, INI_apu_egt=149.63, INI_APU_CONSUMPTION=300, INI_apu_available=0, INI_APU_SHUTDOWN_ACTIVE=1,INI_APU_SHUTDOWN_PHASE=0
- Review external CAM. APU exhaust heat effect and noise still active.
- Monitor fuel level: Fuel continues to drain.
It looks like there is a bug with the APU shutdown process where it never fully shuts down, and continues to drain fuel as if it's still running at 100%, while the exhaust heat and noise effect remain.
Interestingly, using the EFB Panel State "Ready for Takeoff" will fire up the APU to start the engines before shutting it back down again. the N1 and PSI do correctly drop to 0, but the EGT remains at 150 on one attempt and 340 on another attempt. The heat and noise effect remains on the APU exhaust. Fuel weight in the left outer tank drops faster.
Setting the EFB Panel State to "On GPU" or "Cold and Dark" appear to correctly reset the APU to the off state. No detectable fuel flow, no heat effect from APU exhaust.