What was found
ON FLIGHT 4027 THE CREW REPORTED THAT THE EMERGENCY LIGHT SWITCH WAS LEFT IN THE ON POSITION. THE EMERGENCY LIGHT WAS INOPERABLE. THE AIRCRAFT WAS REMOVED FROM SERVICE. REMOVED AND REPLACED EMERGENCY POWER SUPPLY UNIT BATTERY PACKS NR 1 THROUGH NR 4 IAW CRJ 700 AMM 33-51-17. THE OPERATIONAL CHECK WAS GOOD. THE SERIAL NUMBERS: NR 1, 70984, NR 2, 105214, NR 3, 79757 AND NR 4, 73139. THE AIRCRAFT WAS RETURNED TO SERVICE.