ADI STBY Emergency Battery

What it is

A dedicated Li-Ion battery, installed in the left side of the nose avionics bay, that automatically feeds the standby attitude indicator for at least 30 minutes after a total failure of the electrical generating system. It connects through the CB panel to EMER BUS 1, protected by a 7.5A ADI STBY circuit breaker — a self-contained backup for exactly one instrument, not the wider emergency bus.

Controlled by a Control Switch Annunciator on the right side of the interseat console, three positions: ARM (battery powered through EMER BUS 1, ready to supply output), OFF (disconnected from both EMER BUS 1 and the ADI STBY), and TEST (press and hold — checks state of charge is above 80% plus the internal heater and temperature monitoring; TEST illuminates green if it passes). The STBY annunciator itself lights amber whenever the battery is actually delivering power to the ADI.

The only procedure that touches it

Engine pre-start checks: press and hold ADI STBY BATT TEST until TEST illuminates, release, then set the switch to ARM. That's the entire normal-procedures footprint of this system — it's a check-and-arm item, nothing more.