Narrative:

While level at FL320; on J107 south of mlf; we encountered moderate turbulence caused by an aircraft passing directly overhead. The ride prior to the event was smooth. The conditions at FL320 were IMC; however; the sky above was visible. TCAS indicated traffic at our 12 O'clock position at FL330 approaching on J9/J107; the exact reciprocal of our course. Slc ARTCC did not identify the traffic. We monitored the TCAS and acquired a visual of the traffic as it passed overhead. To our surprise it was a B747-400. Within seconds of the pass; we encountered its wake and experienced at least moderate turbulence for 1 to 2 mins in duration. I notified ATC of the event; the controller did not seem concerned. Prior to the encounter; the flight attendant was conducting her cabin service and the seat belt sign was off. Fortunately; the flight attendant and passenger survived the unexpected rough ride with just a few spilled drinks. In trail of the B747 was another B747-400 at FL330. We deviated east of course and avoided perhaps a similar experience. We requested the type of aircraft approaching before ATC reported that traffic. I understand that it is my responsibility; ultimately; to see and avoid other traffic when practical; that I could have requested a traffic report from ATC. However; with rvsm in practice; ATC should be required to report a possible wake encounter so pilots can alert the cabin occupants and deviate as necessary to avoid the wake. We were very lucky that all passenger and crew were unharmed.

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Original NASA ASRS Text

Title: CRJ FLT CREW AT FL320 RPTS ENCOUNTERING WAKE TURB FROM AN OPPOSITE DIRECTION B747-400 AT FL330.

Narrative: WHILE LEVEL AT FL320; ON J107 S OF MLF; WE ENCOUNTERED MODERATE TURB CAUSED BY AN ACFT PASSING DIRECTLY OVERHEAD. THE RIDE PRIOR TO THE EVENT WAS SMOOTH. THE CONDITIONS AT FL320 WERE IMC; HOWEVER; THE SKY ABOVE WAS VISIBLE. TCAS INDICATED TFC AT OUR 12 O'CLOCK POSITION AT FL330 APCHING ON J9/J107; THE EXACT RECIPROCAL OF OUR COURSE. SLC ARTCC DID NOT IDENTIFY THE TFC. WE MONITORED THE TCAS AND ACQUIRED A VISUAL OF THE TFC AS IT PASSED OVERHEAD. TO OUR SURPRISE IT WAS A B747-400. WITHIN SECONDS OF THE PASS; WE ENCOUNTERED ITS WAKE AND EXPERIENCED AT LEAST MODERATE TURB FOR 1 TO 2 MINS IN DURATION. I NOTIFIED ATC OF THE EVENT; THE CTLR DID NOT SEEM CONCERNED. PRIOR TO THE ENCOUNTER; THE FLT ATTENDANT WAS CONDUCTING HER CABIN SVC AND THE SEAT BELT SIGN WAS OFF. FORTUNATELY; THE FLT ATTENDANT AND PAX SURVIVED THE UNEXPECTED ROUGH RIDE WITH JUST A FEW SPILLED DRINKS. IN TRAIL OF THE B747 WAS ANOTHER B747-400 AT FL330. WE DEVIATED E OF COURSE AND AVOIDED PERHAPS A SIMILAR EXPERIENCE. WE REQUESTED THE TYPE OF ACFT APCHING BEFORE ATC RPTED THAT TFC. I UNDERSTAND THAT IT IS MY RESPONSIBILITY; ULTIMATELY; TO SEE AND AVOID OTHER TFC WHEN PRACTICAL; THAT I COULD HAVE REQUESTED A TFC RPT FROM ATC. HOWEVER; WITH RVSM IN PRACTICE; ATC SHOULD BE REQUIRED TO RPT A POSSIBLE WAKE ENCOUNTER SO PLTS CAN ALERT THE CABIN OCCUPANTS AND DEVIATE AS NECESSARY TO AVOID THE WAKE. WE WERE VERY LUCKY THAT ALL PAX AND CREW WERE UNHARMED.

Data retrieved from NASA's ASRS site as of January 2009 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.