B757-200 HAS SERIOUS WAKE TURB ENCOUNTER BEHIND HVY JET DESPITE REPEATED REQUESTS FOR A TRACK DEV FOR SEPARATION.

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ON INITIAL TKOF FROM DFW; CAPT KEPT THE FLT ATTENDANTS DOWN DUE TO TCU IN THE AREA. ATC RESTR US ON CLB SPD TO 250 KTS AND HELD US DOWN TO 10000 FT. AS WE PROCEEDED E; DODGING BUILDUPS; A DC10 PASSED DIRECTLY OVERHEAD. HE WAS ABOUT 2000 FT ABOVE US AND CLRLY FASTER. ATC CONTINUED TO STEP US UP IN 1000-2000 FT INCREMENTS AS HE CONTINUED TO CLB IN FRONT OF US. WE ALL HAD TO STAY ON THE SAME GND TRACK DUE TO THE WX. AS WE PASSED 14000 FT; THE CAPT COMMENTED THAT HE WAS KEEPING THE FLT ATTENDANTS DOWN IN THEIR SEATS DUE TO OUR CLOSE PROX TO THE DC10. WE WERE AT 14000 FT WHEN WE FIRST REQUESTED 'OFF-COURSE TO AVOID THE WAKE TURB.' THE DC10 WAS ABOUT 4 MI AHEAD AND 2000 FT ABOVE US AND WE COULD FEEL 'NIBBLES' OF HIS WASH. ATC STATED UNABLE DUE TO ARR TFC AND WE SHOULD CHK WITH THE NEXT SECTOR. HE SWITCHED US TO THE NEXT SECTOR WHERE WE WERE TOLD TO CLB TO FL230. WE REQUESTED A TURN OFF-COURSE TO AVOID THE WAKE TURB OF THE HVY THAT WAS NOW ABOUT 8 MI AHEAD OF US AND 2700 FT ABOVE US -- ATC AGAIN SAID UNABLE; STAY ON COURSE AND DIRECTED US TO CLB TO FL310. THE DC10 ASKED TO LEVEL AT FL330 SINCE HE WAS HEAVIER THAN PLANNED AND WE STARTED TO DISCUSS THE FACT THAT HE WAS GOING TO CONTINUE TO BE A THREAT DUE TO THE LIMITED AREA TO MANEUVER BECAUSE OF THE TSTMS. AS WE PASSED FL270 TO FL280; WE GOT A STRONG; SHARP L ROLL WITH A R YAW AND HVY AIRFRAME SHAKING. THE CAPT (CALMLY) ALLOWED THE L TURN TO DEVELOP AND I TOLD ATC (IN A HIGH VOICE) THAT WE WERE 'IN SERIOUS WAKE TURB AND TURNING TO A HDG OF 060 DEGS TO ESCAPE.' (WE HAD BEEN ON ABOUT A 075 DEG HDG.) ATC TOLD US TO STAY ON COURSE(!) SO I REPEATED THE CALL AND TOLD THEM THAT WE WERE 'UNABLE; IT IS TOO ROUGH BEHIND THE HVY.' MEANWHILE; THE CAPT WAS STRUGGLING TO STAY UPRIGHT AS WE ESCAPED FROM THE WAKE. THE CTLR'S RESPONSE TO MY SECOND CALL WAS A SARCASTIC 'WELL; IF YOU NEED TO TURN L; COME TO 360 DEGS AND I'LL GET YOU GOOD SEPARATION FROM THE HVY.' LUCKY THE CAPT HAD ELECTED TO KEEP THE FLT ATTENDANTS DOWN. AFTER 2 CALLS TO 2 DIFFERENT CTLRS; ATC SHOULD HAVE BEEN ABLE TO RECOGNIZE THE DEVELOPING SITUATION AND HELP US OUT. I RESOLVED TO BE MORE AGGRESSIVE AND NOT ALLOW THE SITUATION TO DEVELOP IN THE FUTURE. SUPPLEMENTAL INFO FROM ACN 707624: NEXT TIME I FIND MYSELF IN THIS SITUATION; I WILL BE MUCH MORE ASSERTIVE ABOUT GETTING CLR OF TURB FROM ACFT ABOVE ME EVEN THOUGH CTR IS BUSY/UNCOOPERATIVE.