A B717-200 FO RPTED THAT ZID REFUSED THEIR REQUEST FOR A LOWER ALT AFTER THEY ENCOUNTERED ICING WHICH CAUSED SIGNIFICANT PROBS FOR THE FLT.

Narrative

AT FL350; ENG ANTI-ICE ON; R ENG SYS FAIL ALERT; ALL OTHER ENG INDICATIONS NORMAL. WX CONDITIONS WERE IMC; VECTORING (RADAR VECTORS) FOR WX AROUND CQO AREA; ICING CONDITIONS; BUT NO INDICATIONS ON ACFT (ACCUMULATION). AIRSPD BEGAN TO SLIGHTLY DECREASE. AIRFRAME AND TAIL ANTI-ICE WERE TURNED ON BUT THERE WAS STILL NO ACCUMULATION. ASKED ATC FOR LOWER. ATC WANTED US TO STAY WHERE WE WERE DUE TO XING TFC (ABOUT 5 MI). FMA THRUST INDICATION WENT TO MCT AND AIRSPEED SLIGHTLY DECREASED AGAIN. AGAIN REQUESTED LOWER ALT FROM ATC. ATC AGAIN DENIED BUT GAVE US A TURN INSTEAD. BEGAN A 5 DEG TURN TO THE R; ENCOUNTERED A WAVE-TYPE TURB (LIKE GOING LENGTHWISE OVER A WAVE). AS A RESULT OF WAVE TURB; STICK SHAKER FOR ABOUT 1/2 SECOND; OCCURRED WITH A DSCNT STARTING DOWN. CAPT PADDLED AUTOPLT TO STOP DSCNT. TOLD ATC THAT WE NEEDED LOWER; THEN GOT A TA FROM OTHER ACFT BUT WAS NOT IN A DANGEROUS POS TO ACFT (NOTE: ATC GAVE THE LOWER ACFT A R TURN BUT THEY REFUSED TURN.) DSCNT WAS STOPPED APPROX 1200 FT BELOW OUR FLT LEVEL. LOWER ACFT PASSED 2 NM BEHIND US. ATC GAVE US LOWER. ACFT RESPONDED NORMALLY AT LOWER ALT. THE REST OF FLT WAS UNEVENTFUL AND ACFT RESPONDED NORMALLY. DURING THE ABOVE SIT THE FLT ATTENDANT CALLED NUMEROUS (3-4) TIMES ABOUT A VIBRATION IN BUSINESS AND AFT CABIN. JUMPSEATERS (PLTS) IN BUSINESS CLASS INDICATED THE VIBRATION AND NOISE WAS NOT NORMAL. WHILE IN THE COCKPIT NEITHER I NOR THE CAPT HEARD NOR FELT A VIBRATION THROUGHOUT THE SIT.