As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: DURING TEST OF THE EMERGENCY LIGHT SYSTEM TEST FAULT. EMERGENCY POWER SUPPLY SUPPLY UNIT BATTERY AFT LEFT OCCURRED.**SUPPLEMENTAL REPORT FOR AALA202111096642: REPLACED EMERGENCY POWER SUPPLY UNIT 10WL AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK PER AMM 33-51-38.** (CLOSED)