If the "On Bat" light illuminates during ground ops, it indicates the unit is running on its emergency battery, often due to a loss of primary AC power.
To operate the LTN-92, users follow specific sequences outlined in the manual: Turn MSU to ALIGN. ltn-92 manual
Disclaimer: This article is for informational purposes only. Always refer to the official manufacturer's documentation or the specific Aircraft Maintenance Manual (AMM) for your airframe before performing maintenance or flight operations. If the "On Bat" light illuminates during ground