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.