A321
Flight Crew Air Transport Pilot (ATP)
Deviation - Altitude Excursion From Assigned Altitude; Inflight Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued Advisory / Alert; Flight Crew Regained Aircraft Control; Flight Crew Returned To Clearance
Weather
Encountered moderate to severe turbulence about 30 miles north of OMN. Aircraft then entered a downdraft and lost 700 feet of altitude in about 10 seconds. ATC called and said to maintain FL300; we told ATC we were in turbulence and a down draft. Aircraft climbed back to FL300.
We were in cruise flight at FL300. Radar was in calibrated and auto mode. There were some light green returns on the radar on our right side but no different than returns we had seen for the last 100 or so miles while getting a good ride. We were about 30 NM north of the OMN VOR and started to get moderate turbulence; then got an updraft which pushed us up about 200 feet followed by a significant downdraft which caused us to lose 700 feet. The aircraft was on autopilot the entire time and the FMA showed ALT CRUISE. We got a burst or two of moderate rain which caused significant radio static which is a common problem in the Airbus. I could barely hear the controller say to maintain FL300 to which I replied that we were in moderate and greater turbulence. She responded to return to FL300 as soon as possible. There was no traffic showing on the TCAS at the time. The altitude loss was probably a duration of one minute or so from the time the downdraft began until we were back at FL300.I can only guess that a rapidly growing cell was below us. The new radar in the advanced airbuses does seem to sometimes paint WX less severe than the older radars when in the calibrated position. We were in an area with a lot of other aircraft on basically the same route and no one was deviating or reporting significant turbulence. There were no injuries. I would call the turbulence moderate to severe. The jolts were moderate but downdraft was similar to a mountain wave in that the aircraft could not overpower it but the ride during the altitude loss was not terribly violent.Although not a causative factor in this incident; the airbus radio static problem should be looked into. Whenever you are in cold precipitation it is sometimes impossible to communicate due to the static. I have never experienced that to this degree in 23;000 hours in many types of aircraft. I can only conclude it's a design flaw.
A321 flight crew experiences moderate to severe turbulence at FL300 causing a 700 foot altitude loss with the autopilot and autothrust engaged. Radar did not indicate any significant weather in the area.