Narrative:

At 7;000 ft MSL and 8.5 miles in trail of a B777; we encountered severe wake turbulence. Our aircraft began an un-commanded roll to the right. I was the pilot flying and immediately disconnected the autopilot and applied the appropriate control inputs. Aircraft slowly responded and returned to straight and level flight. Approximately four minutes after the first encounter; and while the aircraft was being hand flown; the airplane again commenced an un-commanded right roll. Aircraft did not respond to left rudder and left aileron inputs. Full left rudder (all the way to the stops) and full left aileron (also to the stops) was applied with the airplane continuing to roll right. I applied forward elevator in an attempt to 'unload' the airplane and regain control. This proved to be an effective technique. The airplane slowly rolled back to straight and slightly nose down flight. Controls were then neutralized. Altitude loss was 700 ft. Bank angle was approximately 45 degrees of bank. First officer attempted several times during event to contact approach control to advise them of our situation; but due to frequency congestion; they did not hear our initial calls. Only after the airplane was under control and we had returned to our assigned altitude of 7;000 ft did approach control acknowledge our radio calls and cleared us to change altitude. Approach control did not mention any altitude deviation; nor did they seem overly concerned with our report of the severe wake turbulence encounter. A visual approach with ILS back-up was conducted with our aircraft flown 1/2 dot above glide slope. This was done because the B777 was still 8 miles in front of us on the same approach to runway 22R. No further wake turbulence encountered. After landing and after completion of all checklists; the first officer suggested that in accordance with [the] flight manual [that] the aircraft be inspected and appropriate personnel notified. I agreed with his suggestion and contacted the necessary persons. The aircraft was subsequently removed from service pending inspection.

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Original NASA ASRS Text

Title: An MD83 encountered wake turbulence in trail of a B777 on approach to ORD; resulting in considerable roll and altitude loss.

Narrative: At 7;000 FT MSL and 8.5 miles in trail of a B777; we encountered severe wake turbulence. Our aircraft began an un-commanded roll to the right. I was the pilot flying and immediately disconnected the autopilot and applied the appropriate control inputs. Aircraft slowly responded and returned to straight and level flight. Approximately four minutes after the first encounter; and while the aircraft was being hand flown; the airplane again commenced an un-commanded right roll. Aircraft did not respond to left rudder and left aileron inputs. Full left rudder (all the way to the stops) and full left aileron (also to the stops) was applied with the airplane continuing to roll right. I applied forward elevator in an attempt to 'unload' the airplane and regain control. This proved to be an effective technique. The airplane slowly rolled back to straight and slightly nose down flight. Controls were then neutralized. Altitude loss was 700 FT. Bank angle was approximately 45 degrees of bank. First Officer attempted several times during event to contact Approach Control to advise them of our situation; but due to frequency congestion; they did not hear our initial calls. Only after the airplane was under control and we had returned to our assigned altitude of 7;000 FT did Approach Control acknowledge our radio calls and cleared us to change altitude. Approach Control did not mention any altitude deviation; nor did they seem overly concerned with our report of the severe wake turbulence encounter. A visual approach with ILS back-up was conducted with our aircraft flown 1/2 dot above glide slope. This was done because the B777 was still 8 miles in front of us on the same approach to Runway 22R. No further wake turbulence encountered. After landing and after completion of all checklists; the First Officer suggested that in accordance with [the] flight manual [that] the aircraft be inspected and appropriate personnel notified. I agreed with his suggestion and contacted the necessary persons. The aircraft was subsequently removed from service pending inspection.

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.