Narrative:

This encounter with wake turbulence occurred at FL240 just as our flight began descent to cross bronc intersection at 11000 ft and 250 KTS. We experienced a sudden upset, moderate turbulence with a rolling moment causing our B737-300 to roll to about 45 degree (I would estimate) right bank before the first officer who was flying, could disengage the autoplt and right the aircraft, all the while encountering the turbulence. Our airspeed was about 310 KTS, autothrottles were engaged and a slight descent had been initiated with the 'capture' function on the descent page in the FMS. We could see position lights on another aircraft ahead, observed to be near our altitude some 10 mi away (from TCASII reference). That aircraft had been descending from a higher altitude, also on the gardner ii arrival to bos. The encounter lasted less than 30 seconds, partly because I instructed the first officer to increase the descent to get below the flight path we were on and to still work to make the crossing restr. As we then rapidly moved away from FL240, we flew out of the path of the aircraft's wake we presumed to be the one mentioned. It took some time to get a break in radio traffic on bos center's frequency to inquire about the type aircraft we were following. The controller responded that is was a DC10, so we believed our suspicions about turbulence from a 'heavy' were confirmed. Problem was having a 'heavy' descending ahead of us from a higher altitude crossing our altitude. No warning from ATC about the type, and we would never expect such from ATC in that phase of flight, but the effect was dramatic for a few moments. I am not sure I would have been wary of this on a day to day experience. Now, I might be more prone to notice a clearance to descend for an aircraft higher and in front. Callback conversation with reporter revealed the following information: reporter participated in wake turbulence incident report and was very knowledgeable on ATC procedures at complex airports and CRM procedures. He stated that he wished that ATC, workload permitting, would issue more traffic advisories especially on STAR routes when you are IMC and do not know what type of aircraft you are following.

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Original NASA ASRS Text

Title: WAKE TURB ENCOUNTER.

Narrative: THIS ENCOUNTER WITH WAKE TURB OCCURRED AT FL240 JUST AS OUR FLT BEGAN DSCNT TO CROSS BRONC INTXN AT 11000 FT AND 250 KTS. WE EXPERIENCED A SUDDEN UPSET, MODERATE TURB WITH A ROLLING MOMENT CAUSING OUR B737-300 TO ROLL TO ABOUT 45 DEG (I WOULD ESTIMATE) R BANK BEFORE THE FO WHO WAS FLYING, COULD DISENGAGE THE AUTOPLT AND RIGHT THE ACFT, ALL THE WHILE ENCOUNTERING THE TURB. OUR AIRSPD WAS ABOUT 310 KTS, AUTOTHROTTLES WERE ENGAGED AND A SLIGHT DSCNT HAD BEEN INITIATED WITH THE 'CAPTURE' FUNCTION ON THE DSCNT PAGE IN THE FMS. WE COULD SEE POS LIGHTS ON ANOTHER ACFT AHEAD, OBSERVED TO BE NEAR OUR ALT SOME 10 MI AWAY (FROM TCASII REF). THAT ACFT HAD BEEN DSNDING FROM A HIGHER ALT, ALSO ON THE GARDNER II ARR TO BOS. THE ENCOUNTER LASTED LESS THAN 30 SECONDS, PARTLY BECAUSE I INSTRUCTED THE FO TO INCREASE THE DSCNT TO GET BELOW THE FLT PATH WE WERE ON AND TO STILL WORK TO MAKE THE XING RESTR. AS WE THEN RAPIDLY MOVED AWAY FROM FL240, WE FLEW OUT OF THE PATH OF THE ACFT'S WAKE WE PRESUMED TO BE THE ONE MENTIONED. IT TOOK SOME TIME TO GET A BREAK IN RADIO TFC ON BOS CTR'S FREQ TO INQUIRE ABOUT THE TYPE ACFT WE WERE FOLLOWING. THE CTLR RESPONDED THAT IS WAS A DC10, SO WE BELIEVED OUR SUSPICIONS ABOUT TURB FROM A 'HVY' WERE CONFIRMED. PROB WAS HAVING A 'HVY' DSNDING AHEAD OF US FROM A HIGHER ALT XING OUR ALT. NO WARNING FROM ATC ABOUT THE TYPE, AND WE WOULD NEVER EXPECT SUCH FROM ATC IN THAT PHASE OF FLT, BUT THE EFFECT WAS DRAMATIC FOR A FEW MOMENTS. I AM NOT SURE I WOULD HAVE BEEN WARY OF THIS ON A DAY TO DAY EXPERIENCE. NOW, I MIGHT BE MORE PRONE TO NOTICE A CLRNC TO DSND FOR AN ACFT HIGHER AND IN FRONT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR PARTICIPATED IN WAKE TURB INCIDENT RPT AND WAS VERY KNOWLEDGEABLE ON ATC PROCS AT COMPLEX ARPTS AND CRM PROCS. HE STATED THAT HE WISHED THAT ATC, WORKLOAD PERMITTING, WOULD ISSUE MORE TFC ADVISORIES ESPECIALLY ON STAR ROUTES WHEN YOU ARE IMC AND DO NOT KNOW WHAT TYPE OF ACFT YOU ARE FOLLOWING.

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.