Question

ANSWER:

One of the 3 IR's is operating on DC Power (Batt)

if ASKED:
ON THE GROUND:
during Pre-Flight is normal, as when you select the NAV selection Switch and you place it to NAV the "ON BAT" light will illuminate for 5 seconds to ensure that the IRU can receive DC power from the Battery.

Answer 1

The question involves the operation of aircraft Inertial Reference Systems using DC power from the battery during pre-flight checks.

It's normal for the 'ON BAT' light to illuminate momentarily when the NAV switch is set to NAV, confirming that the IRU can receive DC power.

Step-by-step explanation:

The question pertains to the operation of Inertial Reference Systems (IRS) on aircraft and their reliance on DC power sources, such as a battery, particularly during the pre-flight phase.

When conducting the pre-flight procedure, it's expected that upon positioning the NAV selection switch to NAV, the 'ON BAT' light will illuminate for approximately 5 seconds.

This is a standard check to ensure that the Inertial Reference Unit (IRU) can operate on battery power, which is essential for the alignment process when the aircraft is not receiving external or auxiliary power.

This step is significant as it provides confirmation of the IR's ability to switch to and operate on DC power in case the main AC power source fails during flight.