Date: 201307
Local time of day: 0001-0600
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Aircraft: A319
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Window Ice/Rain System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Human-Machine Interface; Troubleshooting; Situational Awareness
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Weight And Balance
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed As Precaution; Flight Crew Diverted; General Declared Emergency; General Maintenance Action
Contributing factors: Logbook Entry; Procedure; Aircraft; Company Policy; Human Factors
Primary problem: Aircraft

Narrative: In cruise at FL370 I noticed some arcing in the left windshield. I had the First Officer look in the AOM for a procedure to follow. Unable to quickly locate any procedure in the Anti Ice; Electrical or Fire sections and with the arcing getting worse; I transferred control to the First Officer and got out of my seat to try and locate the circuit breaker for windshield heat. Within moments; and prior to locating the proper circuit breaker the situation degraded further as larger arcs and small flames were observed between the layers of windshield glass. At this time I returned to my seat and we commenced an emergency descent while considering a diversion to a near airport. The area between the glass plies appeared to be melting in a line from the lower middle toward the upper left of the glass. Shortly thereafter; the outer glass ply shattered. Sometime during the remainder of the descent the arcing ceased and I believe we received an ECAM for the Windshield heat. After this there were no further signs of damage; however I was very concerned about the integrity of the inner glass ply; though there was no obvious damage to it. During descent we notified the flight attendants and passengers. We sent an ACARS to Dispatch advising them of our situation. We landed overweight at 140.4. The First Officer landed as my visibility was severely compromised. He made a very smooth landing and brought the aircraft to a stop without overheating the brakes. We taxied the aircraft and unloaded the passengers.  The location of the left windshield heat circuit breaker creates an undue hazard in an event such as this. Not only is this circuit breaker difficult to locate; it is also difficult to access without removing a seatbelt and getting up. In this situation being unbelted at the same time that a windshield is compromised is not a good idea. A more suitable location would be in the overhead panel. Failing that solution; a switch on the overhead panel could accomplish the same thing. The location of the procedure for dealing with a faulty windshield heater is also not in the best place. As I have witnessed how rapidly this situation can develop; I believe that a more logical location in the AOM could shorten the time that it takes to locate the circuit breaker for windshield heat. The procedure in the AOM is also incomplete. Having located and pulled the circuit breaker; the procedure seems to imply that barring obvious damage to the interior ply; (i.e. a crack detectable with a finger nail or credit card) the airplane could safely continue to its regular destination. Having watched a heat source (the arcing and flame) cause the fracture of the outer ply of glass; I can assure you that this heat source could very likely have also damaged the inner ply. Continuing on for another couple of hours in this state was never an option for me; and no procedure in the AOM or personnel in MOC should ever recommend continuing to planned destination without having the information that we as pilots possess. I hope that none of my fellow pilots would ever follow the recommendation to continue the flight as planned; however; I am fearful that someday one might. The windshield in question had been written up [three years ago] for delamination and had received numerous inspections over this three year period enabling it to continue in service. I am no expert on these issues; therefore; I can only wonder if the delamination had anything to do with the catastrophic failure of the windshield. Perhaps this needs to be looked into in more depth by the people with expertise in this field.


Second narrative: Initially I opened the AOM to look for Anti Ice procedure since this is what was burning and looked in index under A; there was 'ANTI ICE L (R) Windshield' which was crew awareness only [but] there was no linked or associated page for (Arcing; which in my limited time I couldn't find) and didn't know was hidden under C for cockpit!?Captain transferred controls and attempted to find the circuit breaker to stop the electrical short and was only able to locate the left window as we later learned the windshield circuit breaker is hidden behind the jump seat. As someone that's gone through this I would like to mention that this event happens fast. There is very limited time to access the AOM. Pilots will recognize this is an Anti ice event and will initially flip to that section [under] 'A'. They will not be flipping to 'C' for cockpit...looking for Arcing Anti Ice under 'C' for cockpit was not intuitive for me; especially while in an emergency descent; declaring an emergency and wearing the oxygen mask/goggles.


Synopsis: When the Captain's windshield arced and the outer pane soon shattered the flight crew of an A319 declared an emergency; performed an emergency descent and diverted to a nearby airport. Difficulty in locating the associated procedure in the AOM and difficulty finding the appropriate circuit breaker contributed to their dilemma. The windshield had been written up for delamination but not addressed by Maintenance for three years.