TR3 as backup source for TR2
The last weeks I have spent to step deeper in the electrical system of the 737. The only issue I have found so far is the following:
According to the FCOM TR3 can backup TR1 and TR2. If the TR3 disconnect relay is open, TR3 can only backup TR2.
My test:
* Bus transfer switch is set to off (so TR1 can not backup TR2)
* Transfer Bus 2 failed
* Assuming that DC Bus 2 is still powered by TR3 as backup source
* But indications which are connected to DC Bus 2 (e. g. Right OIL QTY)
While you are at it, some more electrical questions/issues
STBY PWR shows no AC frequency with STANDBY POWER switch on AUTO but works when on BAT. However voltage shows in both cases - bug? feature?
DC meter does not show BAT voltage with BAT switch off - not sure if it is supposed to though.
Failing AC Electronic 1 seems to fail (some) DC Electronic 1 circuits as well, while DC Elec 1 fails less than it should - at least according to the 737 technical site, so I'm not too