Narrative:

During preflight I turned the emergency lights on to check them before I connected the main battery. The aft aisle lights were inoperative; the remainder of the after section emergency lights were dim and the over wing emergency lights were inoperative. I turned the emergency lights off; then connected the main battery. All emergency lights functioned normally. This means the battery pack powering the after emergency lights was discharged. Checking the lights before connecting the main batter is contrary to how we normally operate. There is no specified procedure but the battery is nearly always connected before you enter the aircraft. This is how we have been trained. The battery compartment is adjacent to the aft baggage door. You take your bags to the bagger compartment; connect the battery and begin removing the engine covers. The emergency light batteries trickle charge off of ship's power so with the main battery connected; unless light bulbs are inoperative; the emergency light will always test fine. This is a test of the lighting system but not of the battery that powers the system. Under this 'normal' procedure you would never detect a bad battery pack until you had an actual emergency requiring these lights. This may be the same type of system in other fleets of our aircraft and could go undetected there too. Publish fleet memo to make certain to do a check of the emergency lighting system with the main battery disconnected. This will verify that the entire system is operative.

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Original NASA ASRS Text

Title: CE560 First Officer reports that the normal preflight procedure of testing the emergency lighting with the main battery connected is invalid.

Narrative: During preflight I turned the emergency lights on to check them before I connected the main battery. The aft aisle lights were inoperative; the remainder of the after section emergency lights were dim and the over wing emergency lights were inoperative. I turned the emergency lights off; then connected the main battery. All emergency lights functioned normally. This means the battery pack powering the after emergency lights was discharged. Checking the lights before connecting the main batter is contrary to how we normally operate. There is no specified procedure but the battery is nearly always connected before you enter the aircraft. This is how we have been trained. The battery compartment is adjacent to the aft baggage door. You take your bags to the bagger compartment; connect the battery and begin removing the engine covers. The emergency light batteries trickle charge off of ship's power so with the main battery connected; unless light bulbs are inoperative; the emergency light will always test fine. This is a test of the lighting system but not of the battery that powers the system. Under this 'normal' procedure you would never detect a bad battery pack until you had an actual emergency requiring these lights. This may be the same type of system in other fleets of our aircraft and could go undetected there too. Publish fleet memo to make certain to do a check of the emergency lighting system with the main battery disconnected. This will verify that the entire system is operative.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.