For IMC flight operations, what is the minimum SFI battery voltage required on CDU TDL 2/2 page?

For IMC flight operations, what is the minimum SFI battery voltage required on CDU TDL 2/2 page?

• A. 20 volts
• B. 23 volts
• C. 18 volts
• D. 25 volts

Answer: (B)

In IMC flight, you have to be able to rely on the standby flight instruments if the primary displays are degraded or unavailable. The CDU’s TDL 2/2 page shows the status and requirements for the standby power system, including the minimum voltage the SFI battery must hold to ensure the standby instruments remain powered and dependable. Twenty-three volts is the threshold chosen to guarantee enough electrical headroom for the Standby Flight Instrument under load. If the battery voltage falls much below this level, the standby attitude and related information may not be accurate or could reset, which is unacceptable in instrument flight. Values like 18 or 20 volts would indicate the standby system is not reliable enough for IMC operations, and while 25 volts is acceptable, the minimum required to proceed is 23 volts.

In IMC flight, you have to be able to rely on the standby flight instruments if the primary displays are degraded or unavailable. The CDU’s TDL 2/2 page shows the status and requirements for the standby power system, including the minimum voltage the SFI battery must hold to ensure the standby instruments remain powered and dependable.

Twenty-three volts is the threshold chosen to guarantee enough electrical headroom for the Standby Flight Instrument under load. If the battery voltage falls much below this level, the standby attitude and related information may not be accurate or could reset, which is unacceptable in instrument flight. Values like 18 or 20 volts would indicate the standby system is not reliable enough for IMC operations, and while 25 volts is acceptable, the minimum required to proceed is 23 volts.