Date: 201408
Local time of day: 1201-1800
Location: ZZZZ.Airport, FO
Flight conditions: VMC
Weather elements / visibility: Rain; Thunderstorm
Light: Daylight
Aircraft: Airbus 318/319/320/321 Undifferentiated
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class E ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Gear Extend/Retract Mechanism
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Human factors: Workload; Troubleshooting; Training / Qualification; Human-Machine Interface; Confusion; Communication Breakdown; Distraction
Second reporter function: Pilot Flying; First Officer
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Aircraft Equipment Problem Dissipated; Flight Crew Diverted; Flight Crew Became Reoriented; Flight Crew Landed As Precaution; General Maintenance Action; General Declared Emergency
Contributing factors: Human Factors; Weather
Primary problem: Human Factors

Narrative: During takeoff we were focused on avoiding thunderstorms in the departure corridor. A small single engine Cessna had taken off just prior to us and was given a right turn for departure to the same area we planned for weather avoidance. Immediately after takeoff we requested a right turn from Departure Control which was granted. Our 90 degree turn worked well as we remained vigilant of the Cessna which we immediately out climbed. There was now another concentrated area of cumulus nimbus about 15 miles directly ahead. I was trying to break into the congested Departure Control frequency for a right turn on course; which would provide adequate weather clearance. This took a couple minutes and dominated our attention. I noticed a slight airframe rumbling; but thought it might be the landing lights which were still extended per SOP. Once we were given the right turn on course and accelerated to 250 KTS; we both started to focus on the increasing noise and vibration. I raised the landing lights with very little improvement. We completely concentrated on things that might be wrong with the airplane and searched through numerous system ECAM pages for answers. Everything appeared normal and all symbols were green (including the large green landing gear down and locked symbols which were as we always see them. On the ground. But the gear doors I concentrated on were in fact up and green); so we started hypothesizing about abnormal things that might be wrong with the jet. Things like a missing engine cowl; flap track fairings; gear doors open; flight controls out of position. We continued north as we attempted troubleshooting and began to think of an airport behind us as a good choice of diversion airport. The Lead Flight Attendant had identified himself as a pilot earlier in the day; and we asked him to take a look at the wings; etc. to report back any anomalies. He found nothing unusual. I had asked the First Officer to keep the speed back at 210 KTS; and to level off at 15;000 FT to remain in a safe speed and altitude range for flight controls if something was extended; and to simply protect the airframe. I attempted a radio patch through Dispatch to include Maintenance. The reception quality was poor and we never spoke with Maintenance. We decided to continue communications through ACARS.Enough troubleshooting time had passed that I decided we simply needed to get the plane on the ground safely. I instructed the First Officer to coordinate diversion and landing at the divert airport as I briefed the Lead Flight Attendant with basic TEST information and that we were diverting. I performed the Airframe Vibration QRC as we continued. Nearing the divert airport we received an unclear ACARS message from Dispatch about an emergency being declared. The First Officer and I were not certain whether an emergency had been declared by Dispatch or not. Since we were near our final approach segment I decided to clarify with ATC that we were an emergency aircraft since there was insufficient time to clarify with Dispatch. As the First Officer flew the visual approach he called for Gear Down; Landing Checklist.  It then became immediately clear that our 'problem' was that the landing gear had never been retracted. We continued to a landing without incident since there was not enough time to verify adequate fuel to continue to [our destination] as well as simply wanting to finish the flight to regroup. When Maintenance entered the cockpit; I immediately told them the vibration problem was caused by our failure to raise the landing gear. I told him we had not exceeded any gear speed limits. They performed a gear door inspection; initiated the maintenance write-up and provided a new Maintenance Release for the next flight.I attribute this error to saturation with weather and traffic avoidance on departure followed by a lack of performing normal SOP climb out procedures for the same reason. I had actually verbalized to the First Officer upontakeoff clearance that we may be better off waiting. There was another aircraft on short final approach and we quickly determined it would be safe to depart and simply ask Departure Control for an immediate right turn away from departure corridor weather. We were handed off to Departure immediately; and my/our focus became intensely on clearing traffic and weather on a very congested frequency. Obviously; I did not raise the gear and after raising flaps we had already completed our 90 degree right turn and were quickly headed toward the cumulus nimbus area directly ahead. My attention was now primarily on trying to break in to the busy Departure Control frequency for an immediate clearance north away from the weather. This dominated both of our attention; and I believe I never accomplished the After Takeoff Checklist since it's simply so out of sequence climbing out of approximately five or six thousand feet. The First Officer and I were flying together for the first time; and had completed an uneventful SOP flight in this same aircraft just prior to this flight. Between us we have around 30;000 flight hours; and about eight years each of experience in the Airbus. I believe this is an important contributing factor since I have never experienced even a delayed gear retraction on takeoff. It's such an unusual thing that we simply didn't consider it. As we scrolled through ECAM system pages and other troubleshooting attempts/hypothesis; we never considered such a simple error. Our experience level simply lead us directly to troubleshooting a problem; rather than look for the obvious solution. It's the most embarrassing event of my flying career. This flight encountered a confluence of flight operation challenges as well as human dynamic factors which resulted in a sub par performance. It's not like we lacked understanding of landing gear panel or ECAM symbols. I simply allowed my focus on weather and aircraft avoidance to lead to my neglect of basics. I simply failed to raise the landing gear and perform the After Takeoff Checklist properly since we were so far past the normal flight sequence to accomplish it while concentrating on immediate safety of flight procedures. The primary satisfaction I derive from my career is the reward of providing a high level of safety to the passengers and crew who have entrusted their lives to me. It has had a profound impact on me and the only thing I can do now is ensure it is an event which leads to improved piloting skills on my part. I am glad the company allowed us to continue as the flight crew; since I personally wanted to get back in the saddle and put this behind us. While reflecting on the incident with a determination to make something positive come of this; I have developed some new strategies/goals for myself. Should I ever encounter an unusual occurrence while operating an aircraft devoid of obvious cautions and warnings I will simply start with a review of the last checklist to have been accomplished prior to the event. Then; I will simply take a detailed look at things such as ECAM pages; system switch positions and lights; etc. Just a basic; quiet; uninterrupted review of all the basics before heading down a path of more advanced troubleshooting. Lacking a solution; I will take control of the aircraft and ask the First Officer and any jumpseating pilot to do the same procedure. This will not require much time and will ensure a thorough; pragmatic analysis prior to more advance troubleshooting which can obviously prevent the accomplishment of required simple solutions. Additionally; transferring aircraft control may provide clues to the pilot taking control as well as clearing the previously flying pilot's mind to now focus exclusively on troubleshooting. Obviously; this type of regrettable error can occur to a very experienced flight crew which is working well together.


Second narrative: [Report narrative contained no additional information]


Synopsis: An Airbus crew departed toward weather and while working with ATC for weather avoidance failed to raise the landing gear but did not recognize the vibration's source until an emergency had been declared for a diversion to a nearby airport.