Narrative:

We were being vectored for a visual approach. At 7;000 ft; airspeed 170 KTS assigned and flaps at two degrees when we suddenly experienced violent vibration or turbulence. It felt like a stall but there was no pli [pitch limit indicator] and we were well above the asi green dot. The aircraft rolled as if in wake turbulence and the first officer either disconnected the autopilot or it automatically disconnected. The first officer was using large aileron inputs and could not hold altitude. We started descending. I tried calling ATC but was blocked. By the third attempt to contact we were at 6;200 ft. I advised we needed lower and they cleared us to 6;000 ft. At this point things were smooth. I said we needed to get out of some-one's wake. They said the only traffic was an airbus at 4;400 ft. I think we might have hit their wake while they were descending.this flight had been delayed because of a 'flight control no dispatch' cas message. After talking with maintenance and resetting some systems with no effect the whole airplane was powered down. This cleared the alert. I don't know if it was a control malfunction. The event did feel like something was wrong--as in runaway trim; flutter or control surface operating incorrectly; however we had no alerts or messages during the event. It could also have been wake turbulence caused by the airbus descending through our altitude. Upon reaching the gate we had no alerts or messages indicating a malfunction. I do not know what caused it or how it could be prevented. I have never had a situation like this. I feel the first officer did an excellent [job] of aircraft control.

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Original NASA ASRS Text

Title: An ERJ-170 flight crew suffered momentary loss of control and loss of altitude when they encountered likely wake turbulence during arrival vectoring.

Narrative: We were being vectored for a visual approach. At 7;000 FT; airspeed 170 KTS assigned and flaps at two degrees when we suddenly experienced violent vibration or turbulence. It felt like a stall but there was no PLI [Pitch Limit Indicator] and we were well above the ASI green dot. The aircraft rolled as if in wake turbulence and the First Officer either disconnected the autopilot or it automatically disconnected. The First Officer was using large aileron inputs and could not hold altitude. We started descending. I tried calling ATC but was blocked. By the third attempt to contact we were at 6;200 FT. I advised we needed lower and they cleared us to 6;000 FT. At this point things were smooth. I said we needed to get out of some-one's wake. They said the only traffic was an Airbus at 4;400 FT. I think we might have hit their wake while they were descending.This flight had been delayed because of a 'FLT Control No Dispatch' CAS message. After talking with Maintenance and resetting some systems with no effect the whole airplane was powered down. This cleared the alert. I don't know if it was a control malfunction. The event did feel like something was wrong--as in runaway trim; flutter or control surface operating incorrectly; however we had no alerts or messages during the event. It could also have been wake turbulence caused by the Airbus descending through our altitude. Upon reaching the gate we had no alerts or messages indicating a malfunction. I do not know what caused it or how it could be prevented. I have never had a situation like this. I feel the First Officer did an excellent [job] of aircraft control.

Data retrieved from NASA's ASRS site as of July 2013 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.