- First, in the standby power section. The CBT said that if the Standby power is
at auto position and battery is place to off and no AC generator is operate
the AC and DC standby bus will not be energize by battery. Why?
It's just the way the aircraft was designed. The internal logic of the Standby Power Control Unit (SPCU) prevents power from going to the AC Standby Bus. Logic inside the SPCU controls a Remote Control Circuit Breaker (which supplies power to the Static Inverter) won't close in this configuration, and you get no hot battery power going to the Static Inverter. Therefore you have no AC Standby Power.
There is also a relay inside the SPCU, called K3, which prevents hot battery bus power going to the DC Standby Busses in your specified configuration.
- Why during making the Auto land, the DC Bus tie open and separate the
Left & Right Electric sys.
It is a legal/safety requirement that equipment used for Autoland receive electrical power from separate sources. When navigating so close to the ground, you don't want one electrical failure to affect too many devices.
Regards
NSEU