Narrative:

We were inbound on the oxi arrival to ord. We crossed bearz intersection at 11000 ft, called approach as instructed by ATC. Approach gave us a descent to 7000 ft. I acknowledged the clearance and the first officer, who was the PF, started his descent. I made a PA telling the flight attendant to prepare for landing. Around 10000 ft on the way down, we were rolled several times left and right by wake turbulence. I informed ATC of the wake encounter and asked for a slight heading change upwind. At that time we had a light quartering tailwind from the left. ATC's response was that we were not following a heavy, and instructed us to turn to a heading of 360 degrees. As soon as we turned, we were out of the wake turbulence. The only act I noticed in front of us at the time was about 7 to 8 mi ahead on the same heading and about 2500 ft below us. Upon arrival after the passenger deplaned, the flight attendant informed me that as she was conducting her safety compliance check, she hit her head in the cabin when we encountered the wake turbulence. She told me she felt ok. As a precaution, I had her go to in-flight and fill out a report. As far as the wake encounter, I have a theory why we encountered wake turbulence. But it would be hard to prove. One thing I have noticed lately, especially on the arrs over bearz intersection, is that ATC is spacing aircraft closer. In fact, earlier in the day on the same arrival, they had us following a B747 who was 5 to 6 mi ahead and 1000 ft above and had him descend to our altitude. To me it seems ATC is spacing aircraft closer and compromising safety to get more flts in on a given time. I feel that there will be more wake encounters unless we do what's necessary to stay out of it. Callback conversation with reporter revealed the following information: they were following a B737 and had a light quartering tail wind of about 5 to 6 KTS. He said the aircraft rolled about 30 degrees several times. He thinks the spacing of aircraft is too close.

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Original NASA ASRS Text

Title: AN EMJ CREW INBOUND TO ORD DSNDING AND FOLLOWING A B737, 7 MI AHEAD, ENCOUNTERED WAKE TURB CAUSING THE ACFT TO ROLL SEVERAL TIMES L AND R.

Narrative: WE WERE INBOUND ON THE OXI ARR TO ORD. WE CROSSED BEARZ INTXN AT 11000 FT, CALLED APCH AS INSTRUCTED BY ATC. APCH GAVE US A DSCNT TO 7000 FT. I ACKNOWLEDGED THE CLRNC AND THE FO, WHO WAS THE PF, STARTED HIS DSCNT. I MADE A PA TELLING THE FLT ATTENDANT TO PREPARE FOR LNDG. AROUND 10000 FT ON THE WAY DOWN, WE WERE ROLLED SEVERAL TIMES L AND R BY WAKE TURB. I INFORMED ATC OF THE WAKE ENCOUNTER AND ASKED FOR A SLIGHT HDG CHANGE UPWIND. AT THAT TIME WE HAD A LIGHT QUARTERING TAILWIND FROM THE L. ATC'S RESPONSE WAS THAT WE WERE NOT FOLLOWING A HVY, AND INSTRUCTED US TO TURN TO A HDG OF 360 DEGS. AS SOON AS WE TURNED, WE WERE OUT OF THE WAKE TURB. THE ONLY ACT I NOTICED IN FRONT OF US AT THE TIME WAS ABOUT 7 TO 8 MI AHEAD ON THE SAME HDG AND ABOUT 2500 FT BELOW US. UPON ARR AFTER THE PAX DEPLANED, THE FLT ATTENDANT INFORMED ME THAT AS SHE WAS CONDUCTING HER SAFETY COMPLIANCE CHK, SHE HIT HER HEAD IN THE CABIN WHEN WE ENCOUNTERED THE WAKE TURB. SHE TOLD ME SHE FELT OK. AS A PRECAUTION, I HAD HER GO TO INFLT AND FILL OUT A RPT. AS FAR AS THE WAKE ENCOUNTER, I HAVE A THEORY WHY WE ENCOUNTERED WAKE TURB. BUT IT WOULD BE HARD TO PROVE. ONE THING I HAVE NOTICED LATELY, ESPECIALLY ON THE ARRS OVER BEARZ INTXN, IS THAT ATC IS SPACING ACFT CLOSER. IN FACT, EARLIER IN THE DAY ON THE SAME ARR, THEY HAD US FOLLOWING A B747 WHO WAS 5 TO 6 MI AHEAD AND 1000 FT ABOVE AND HAD HIM DSND TO OUR ALT. TO ME IT SEEMS ATC IS SPACING ACFT CLOSER AND COMPROMISING SAFETY TO GET MORE FLTS IN ON A GIVEN TIME. I FEEL THAT THERE WILL BE MORE WAKE ENCOUNTERS UNLESS WE DO WHAT'S NECESSARY TO STAY OUT OF IT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THEY WERE FOLLOWING A B737 AND HAD A LIGHT QUARTERING TAIL WIND OF ABOUT 5 TO 6 KTS. HE SAID THE ACFT ROLLED ABOUT 30 DEGS SEVERAL TIMES. HE THINKS THE SPACING OF ACFT IS TOO CLOSE.

Data retrieved from NASA's ASRS site as of July 2007 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.