Narrative:

We were enroute at FL360; deviating around thunderstorms and in light turbulence at about .76 mach when number two engine exceeded normal limits in N1 vibration. Our limits are 5.0 and the engine lower display ECAM was flashing at 6.0. Over the next five minutes the vibration number increased to a high of 8.3 and noticable vibration was felt throughout the airplane and controls. No other adverse indications from any other engine indications. We referred to the flight manual and contacted maintenance through dispatch. As the captain tried to communicate problem to maintenance we reduced the bad engine power to idle. I coordinated a slow descent with ATC since we could not hold altitude with one engine at idle. The N1 vibration at idle initially indicated 3.5 which was below the 5.0 limit. We decided it best to keep the engine at idle. We did try one increase and the vibration increased again. We did not try again. After discussions with dispatch and maintenance we made the decision to divert to the closest suitable airport. We made an uneventful descent and landing using the good engine and keeping the vibrating one in idle. I did note the N1 vibration was almost zero once we were with approach and at about 10;000 feet. After landing we shut the engine down as soon as we cleared the runway. Our checklist in the flight manual provided very little guidance. It did direct us to land at the nearest suitable airport and that's the only statement that really provided any useful guidance in this situation. It should be also noted that our maintenance did not have access to engine data while we were airborne as is provided by other modern aircraft. This resulted in us having to spend time to accurately report the condition of the engine to maintenance. I think ZZZ logistically would have been a better divert airfield but would not have met our requirement to land at the nearest suitable airfield.

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Original NASA ASRS Text

Title: An A320 flight crew diverted to the nearest suitable airport when the vibration level of the right engine suddenly increased beyond limits.

Narrative: WE were enroute at FL360; deviating around thunderstorms and in light turbulence at about .76 mach when number two engine exceeded normal limits in N1 vibration. Our limits are 5.0 and the engine lower display ECAM was flashing at 6.0. Over the next five minutes the vibration number increased to a high of 8.3 and noticable vibration was felt throughout the airplane and controls. No other adverse indications from any other engine indications. We referred to the Flight Manual and contacted maintenance through Dispatch. As the Captain tried to communicate problem to Maintenance we reduced the bad engine power to idle. I coordinated a slow descent with ATC since we could not hold altitude with one engine at idle. The N1 vibration at idle initially indicated 3.5 which was below the 5.0 limit. We decided it best to keep the engine at idle. We did try one increase and the vibration increased again. We did not try again. After discussions with Dispatch and Maintenance we made the decision to divert to the closest suitable airport. We made an uneventful descent and landing using the good engine and keeping the vibrating one in idle. I did note the N1 Vibration was almost zero once we were with approach and at about 10;000 feet. After landing we shut the engine down as soon as we cleared the runway. Our checklist in the Flight Manual provided very little guidance. It did direct us to land at the nearest suitable airport and that's the only statement that really provided any useful guidance in this situation. It should be also noted that our maintenance did not have access to engine data while we were airborne as is provided by other modern aircraft. This resulted in us having to spend time to accurately report the condition of the engine to Maintenance. I think ZZZ logistically would have been a better divert airfield but would not have met our requirement to land at the nearest suitable airfield.

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.