A320 FLT CREW ENCOUNTERS WAKE TURB DURING APCH AND EXECUTES A GAR AT ORD.

Narrative

AFTER A NON EVENTFUL FLT FROM CYVR INTO ORD; WE WERE BEING VECTORED FROM DOWNWIND ONTO FINAL FOR A VISUAL TO RWY 22R. ON THE BASE LEG; WE NOTICED A PLANE BEING TURNED ONTO FINAL FROM BEHIND US. BASED ON THE RELATIVE PROX; WE THOUGHT THAT THE PLANE WAS BEING VECTORED TO A DIFFERENT RWY. WE KEPT IT IN SIGHT. THE CTLR TURNED US TOWARDS FINAL; BUT LEFT US FAIRLY HIGH. SINCE WE WERE HIGH AND WERE GOING TO HAVE TO WORK TO GET DOWN; I AS THE PF ELECTED TO DIRTY UP A BIT EARLIER THAN NORMAL. WE CONFIGURED TO GEAR DOWN; FLAPS 3 DEGS; SPD BRAKES OUT AND ASSIGNED SPD OF 180 KTS TO GET DOWN. AS WE TURNED ONTO FINAL; IT WAS NOW BECOMING MORE CLR THAT THE ACFT WE WERE KEEPING AN EYE ON WAS ACTUALLY GOING TO RWY 22R. WE HAD NO PREVIOUS HEADS UP FROM THE CTLR. AS SOON AS WE ROLLED OUT ON FINAL; IT WAS CLR THAT WE WERE GOING TO BE WAY TOO CLOSE. THE CAPT ASKED THE CTLR ABOUT THE PRECEDING ACFT AND ASKED WHY WE WERE TURNED IN SO CLOSE BEHIND HIM. THE CTLR RESPONDED SOMETHING TO THE EFFECT THAT THE PRECEDING ACFT HAD STARTED SLOWING TOO EARLY AND THAT WAS THE CAUSE OF THE RELATIVE CLOSENESS. I BELIEVE THAT EVEN WITH CONSTANT SPDS; IT WOULD HAVE BEEN CLOSE AT BEST AS TO WHETHER WE WERE GOING TO GET PROPER SEPARATION. WE NEVER DID GET A REASON AS TO WHY AN ACFT THAT APPEARED TO BE BEHIND US ON DOWNWIND WAS TURNED ONTO FINAL BEFORE US. I HAD BEEN HAND FLYING THE ACFT WITH THE AUTOTHROTTLES ON. I INITIATED AN S-TURN TO THE R TO TRY TO GAIN SOME SEPARATION AS WE WERE DSNDING FROM ABOVE THE GS. AS WE WERE DSNDING AND IN A R TURN AWAY FROM THE LOC; WE RAN INTO THE PRECEDING ACFT'S WAKE TURB. THOUGH THE TURB WAS EQUIVALENT TO MODERATE TURB; WE STARTED TO ROLL TO THE L. I COUNTERED WITH FULL R SIDE STICK; WHICH INITIALLY HAD NO EFFECT AT ALL. SIMULTANEOUSLY WE START GETTING LOTS OF BELLS; LIGHTS AND WHISTLES. IT WAS ONLY A SECOND OR TWO THAT I COULD NOT CTL THE ACFT. I FIRST NOTICED THE AMBER 'USE MAN PITCH' ON THE PFD INDICATING THAT WE WERE IN DIRECT LAW. THOUGH THAT GOT MY HEART RATE UP A BIT; I WAS CONSOLED BY THE FACT THAT THE PLANE WAS RESPONDING TO MY INPUTS NOW. SIMULTANEOUSLY; AND JUST TO KEEP THINGS INTERESTING; WE WERE GETTING THE 'SPD; SPD; SPD' AURAL WARNING. AS I WAS GETTING CTL OF THE PLANE AND GETTING BACK TO WINGS LEVEL; I ALSO CLICKED OFF THE AUTOTHROTTLES TO MANUALLY CTL THE THROTTLES TO ENSURE THAT WE HAD ENOUGH PWR ON THE PLANE. AS FAR AS THE SPD ISSUE; I DIDN'T FEEL THAT WE WERE GETTING THAT SLOW; BUT THIS WAS ALL HAPPENING SIMULTANEOUSLY. THOUGH I DID SEE 160 KTS AS I WAS HEARING THE 'SPD' CALL; THE SPD TAPE WAS NOT IN THE VLS RANGE. MANUAL THROTTLES ALLEVIATED THAT PROB UNTIL I COULD GET BACK TO IT. THE CAPT HAS A TON OF A320 TIME AND IN A FAIRLY QUICK AND ACCURATE MANNER DETERMINED WHAT HAD HAPPENED. WE BELIEVED THAT WE HAD HAD A WAKE TURB INDUCED; ABNORMAL UPSET OF THE ACFT; AND SINCE WE HAD THE GEAR DOWN; WE WENT DIRECTLY TO DIRECT LAW AS OPPOSED TO ALTERNATE LAW. THE TIME THAT THE ACFT WAS NOT RESPONDING TO MY INPUTS WAS ACTUALLY VERY BRIEF; BUT DIFFICULT TO PUT A NUMBER TO. PROBABLY NO MORE THAN 1.5 SECONDS OR SO. ONCE STABLE; WE INITIATED A GAR. AS ADVERTISED; WE WENT TO ALTERNATE LAW AS WE RAISED THE GEAR. WE FLEW A NORMAL GAR PATTERN; TALKED ABOUT AND BRIEFED THE APCH. I CONTINUED TO FLY. THE CAPT HANDLED THE ECAMS; WHICH WERE MANY. AS PRESCRIBED; WE DID A FLAPS 3 DEG LNDG TO ORD RWY 27L. WITH THE INCREASED LNDG DISTANCE; WE PREFERRED THE LONGER RWY. WE LANDED ON RWY 27L; FLAPS 3 DEGS UNEVENTFULLY. WE OPTED NOT TO DECLARE AN EMER AS WE FELT WE KNEW WHY WE WENT TO DIRECT LAW AND WE WERE ALREADY IN THE PATTERN AT ORD. THE PLAN WAS FLYING AS ADVERTISED. IN RETROSPECT; IT MIGHT HAVE HELPED A BIT TO GET MORE DISTANCE BTWN US AND THE PRECEDING ACFT ON RWY 27L FINAL AS WE WERE IN A REDUCED CTL MODE; BUT I WAS STILL VERY COMFORTABLE WITH THE DECISION THAT WE MADE. ACFT TAXIED UNEVENTFULLY TO THE GATE AND THE MECHS RESET EVERYTHING. WE TOOK THAT PLANE TO ATL 1 HR LATER.