737 MRG stupid question about refuelling panel

[zuxrat]

Good afternoon!
There is one question in MRG that I can't solve.

Q36 What indication on the flight deck tells you that the door of the Fuelling Station is open?
Hint: No, don't look through the window. The answer is on the overhead panel.

Does anyone have any idea? I couldn't find anything.

Thanks!

[Flying Wild]

Originally Posted by zuxrat

Good afternoon!
There is one question in MRG that I can't solve.

Q36 What indication on the flight deck tells you that the door of the Fuelling Station is open?
Hint: No, don't look through the window. The answer is on the overhead panel.

Does anyone have any idea? I couldn't find anything.

Thanks!

Battery Voltage.

When the panel is open it will read ~27 Vdc. When it’s closed it will read ~31 Vdc

[hans brinker]

Originally Posted by Flying Wild

Battery Voltage.

When the panel is open it will read ~27 Vdc. When it’s closed it will read ~31 Vdc

Not on the 737 myself, but curious. I am assuming this is with the aircraft on external power. Does this mean the battery gets isolated from external by opening the fuel panel? And if true, why?

[FlyingStone]

With the refueling panel open, the main battery charger isn't (trickle) charging the battery, so the voltage displayed is that of the battery (~28V), not the charger (~31V).

[zuxrat]

Thank you for reply. Have a nice day!

[Bulfer]

I think to be completely accurate one should say the battery charger enters the TR mode (fixed at 27.5v)
Of course I could be incorrect