An A320 flight crew diverted to the nearest suitable airport when the vibration level of the right engine suddenly increased beyond limits.
Synopsis
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.
Second reporter narrative
At FL360; in and out of clouds; SAT -54; lower EWD [Engine Warning Display] rolled to ENGINES. The right engine indicated N1 VIB (vibrations) of over 5.0; peaking at 8.3. [We] descended to FL280 with the thrust lever retarded; unable to bring VIB below 5.0. Descended to FL200 with the thrust level at idle; we were able to bring VIB to below 5.0. We were in contact with Dispatch and Maintenance Control. With thrust lever at idle and per the Irregular checklist we decided to divert.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.