Date: 201410
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Light: Night
Aircraft: Citation Excel (C560XL)
Operator: Fractional
Operating under: Part 135
Flight phase: Parked
Aircraft component: Emergency Light
Component problem: Malfunctioning
Reporter organization: Fractional
Reporter function: First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Troubleshooting; Training / Qualification; Confusion; Communication Breakdown
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Pre-flight
Result: General None Reported / Taken
Contributing factors: Procedure; Chart Or Publication; Aircraft; Human Factors; Manuals
Primary problem: Human Factors

Narrative: On preflight we checked the Emergency lights before hooking up battery to check the emergency batteries; the rear battery pack was dead.  Called Maintenance Control and they said since they work with the ship's battery connected then they are fine. This doesn't change the fact the battery pack was dead. The company procedure is only to verify the light bulbs themselves are working; it's not a check of the system. Maintenance Control said it doesn't matter; I said it does because if we lose DC power those lights won't work.  This went in a circle a few times until Maintenance Control angrily said 'I don't care; write it up; we'll break it.'  And hung up on me.  PIC sent in the write up.  Assistant Chief Pilot (ACP) called the PIC and said the plane is fine despite the fact we both know those lights are suppose to work but weren't working. Those are the facts from this morning. I've been working on this for maybe 5 years now.  The original company reports and closure letters have been purged from the system.  My first report was on the same situation; battery pack dead.  We wrote it up and it was fixed; no pushback or questions asked (maybe three times actually we've had this squawk and never received any pushback). The report was filed because we were always taught that the emergency lights were powered off of the main DC [bus] which is battery connected and the Main Battery switch 'On'.  If that were true then the lights would remain dim or inop with a bad battery pack when the ship's battery was connected.  But that is not what happened years ago.  This generated the report since either our training was wrong or the airplane was miswired.  In the closure letter it was mentioned a third party group (not Cessna) reviewed the wiring schematics and the emergency lights are actually on the Hot Battery Bus.  I filed another report in response to this closure letter about our information being incorrect; nothing happened. When I was on the phone with Maintenance Control this morning he said the Emergency lights are powered by the Emergency light battery packs when you have the Emergency light switch 'On'.  According to my information that is only partially correct. They are powered from their emergency battery packs FROM the ship's battery (main battery connected; hot battery bus).  Not even Maintenance knows how they work.  And this masks when a battery pack is inoperative.  On the Excel if the nose gear collapses or departs the aircraft you cannot egress through the main cabin door; you must use the aft overwing exit.  What if this was an Excel; at night; and in the crash the battery broke?  No lights to help you out of the plane.  Now set the plane on fire and fill the cabin with smoke. We have had several smoke filled cabins in the fleet. It's only a matter of time before the events converge. The company preflight checklist has you connect the main battery first and foremost.  We have a known issue with the battery packs dying before their maintenance inspection and when we find one we're pressed into flying the plane because the procedure is outline; even though it's fundamentally flawed.  We find a problem but are told there is no problem.  This is a perfect example of what is legal may not be right; or safe.   The maintenance interval on the emergency batteries is (I believe) two years.  Obviously this needs to be addressed and either the interval shortened or allow the crews to actually be pilots and determine when the aircraft is broke regardless of what procedures the company writes - especially in this case where we have a known issue with these battery packs. To my knowledge this happens at least a few times per year.




Synopsis: A First Officer (F/O) describes his efforts and frustration with an unresolved cabin safety issue involving emergency light battery packs that are found dead on their Cessna CE-560XL aircraft during preflight. Misunderstandings between flight crew and Maintenance Control about how the emergency lights function when operated from the aircraft's main battery or from the emergency light battery packs; continue to plague the discussion.