Narrative:

I was the captain and the pilot flying to ord. We were in contact with chicago center and given a descent to FL270 and we were given a speed restriction prior to upset event of 270 knots. The aircraft ahead of us was a boeing 747. The B747 was doing 300 knots or better to increase the separation. At the time of the upset; we were separated by 11 NM.approaching the level off at FL270; approximately 200 feet above that altitude descending at a rate of 500 feet per minute we encountered some moderate buffeting characteristic of aircraft wake turbulence. Within about 1 second of the onset of the turbulence; the aircraft started to roll to the left and the autopilot was unsuccessfully struggling to counteract the roll. I disconnected the autopilot and the first officer called out 'upset'. We had entered the B747's right wingtip vortex.heading changed by a few degrees to the left and we were out of the rolling moment just as quickly as we entered. The seatbelt sign was quickly turned during that event by me. After the event; we were about 50 feet above our level off altitude and I hand flew the level off. I returned the aircraft to course and reengaged the autopilot. The first officer commented after the event that we reached about 35 degrees of left bank. I had the first officer make a PA explaining the event to the passengers to help calm their fears they may have had. I made a report to chicago center that they flew us into the B747's wake turbulence. They apologized and offered me an offset if I wanted. I accepted and we setup 1 mile right of course. The B747 was given direct fytte shortly after the upset while leaving us on the fytte five arrival to bhawk to further increase lateral separation and reduce the possibility that we would fly back into his wake turbulence.

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Original NASA ASRS Text

Title: B737NG Captain reported an inflight upset occurred at FL270 descending into ORD 11 miles in trail of a B747.

Narrative: I was the Captain and the Pilot Flying to ORD. We were in contact with Chicago Center and given a descent to FL270 and we were given a speed restriction prior to upset event of 270 knots. The aircraft ahead of us was a Boeing 747. The B747 was doing 300 knots or better to increase the separation. At the time of the upset; we were separated by 11 NM.Approaching the level off at FL270; approximately 200 feet above that altitude descending at a rate of 500 feet per minute we encountered some moderate buffeting characteristic of aircraft wake turbulence. Within about 1 second of the onset of the turbulence; the aircraft started to roll to the left and the autopilot was unsuccessfully struggling to counteract the roll. I disconnected the autopilot and the First Officer called out 'Upset'. We had entered the B747's right wingtip vortex.Heading changed by a few degrees to the left and we were out of the rolling moment just as quickly as we entered. The seatbelt sign was quickly turned during that event by me. After the event; we were about 50 feet above our level off altitude and I hand flew the level off. I returned the aircraft to course and reengaged the autopilot. The First Officer commented after the event that we reached about 35 degrees of left bank. I had the First Officer make a PA explaining the event to the passengers to help calm their fears they may have had. I made a report to Chicago Center that they flew us into the B747's wake turbulence. They apologized and offered me an offset if I wanted. I accepted and we setup 1 mile right of course. The B747 was given direct FYTTE shortly after the upset while leaving us on the FYTTE FIVE ARRIVAL to BHAWK to further increase lateral separation and reduce the possibility that we would fly back into his wake turbulence.

Data retrieved from NASA's ASRS site 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.