Date: 201401
Local time of day: 1801-2400
Location: ZZZ.ARTCC, US
Aircraft: A320
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight; Pre-flight
Result: Flight Crew Diverted; General Maintenance Action
Contributing factors: Human Factors; Weather; Aircraft
Primary problem: Ambiguous

Narrative: During the pre flight I became aware that the aircraft was downgraded to Cat 1 only and the ILS was inoperative on my side. The forecast for our arrival time was 400/1 and well within our landing minimums for the RNAV approach. When we were approximately within 600 miles of the airport the weather had deteriorated to VV 100 and 1/16 of a mile. I notified Dispatch that this made any approach impossible and that I felt it was time to divert to our alternate airport. The new forecast did not have the weather improving to RNAV landing minimums until XA:00 CST. I was informed that he would like me to continue in hopes of improvement. We were within 200 miles of the alternate and moving further away as we flew. After another ACARS message to company I was informed that I was to continue on and hold for an hour and then divert. As we got closer; the weather was still not improving; so I decided to contact Dispatch. At this time I made it clear that there was no way to land in this weather with the downgraded conditions of our aircraft. He felt that by that time we would be able to shoot the RNAV if there were no simultaneous approaches being conducted. I was told to continue on and hold and hope for better weather. When we arrived in the terminal area we were placed in holding and I once again contacted Dispatch via ACARS. I was then told to refer to the chart for the RNAV. I was then told that my landing minimums were RVR 2400 with no simultaneous approaches. I explained that the minimums for us were RVR 4000. We were not category A or B aircraft and that the best visibility on the field was only RVR 1200. He then wanted me to try the approach and if I went missed to continue on to my alternate. At this point I felt there was a lack of understanding of how poor the weather was and decided to depart for the alternate before something bad happened. Upon arrival at the alternate; maintenance met the aircraft. The aircraft was restored to CAT 3 status and we departed for our original destination. We shot a CAT 3 autoland and the weather was VV100 and RVR 1100. We did not see the runway until 50 feet and would never have gotten in on the RNAV. When I got to the gate I was told MX had been waiting all night for us because our aircraft had all the MX parts for RON aircraft. I suddenly got the feeling that this may have been the reason for all the pressure to get in at all cost. I don't feel Dispatch had any malice in pushing me; I just feel he was pressured to get us in. I had notified them that the aircraft was downgraded and my First Officer was high minimums on his first trip out of OE. I had a MX Supervisor on the aircraft the whole time and he couldn't believe the aircraft was not signed off before being dispatched into that kind of weather. I don't really have any suggestions on how to fix this type of problem. I just hope the next guy doesn't shoot an approach that is illegal because of being pressured. I would hate for someone to lose their license or worse.




Synopsis: A320 Captain reports being dispatched in an aircraft downgraded to CAT I with weather forecast to be above approach minimums. Enroute the weather goes below minimums and a diversion is requested from Dispatch but denied. After holding with no improvement; Dispatch suggests that the Captain attempt an approach with the weather below applicable minimums. The Captain diverts to his alternate.