AN ACR BAE ATP FLC HIT THE WAKE OF AN ACR B727 DURING THEIR APCH AND FO EXECUTED GAR.

Narrative

THE CAPT WAS FLYING THE LEG AND ON SHORT FINAL INTO O'HARE INTL RWY 9R. SEVERE WAKE TURB WAS ENCOUNTERED AT LESS THAN 100 FT AGL. THE ACFT ROLLED INTO AN APPROX 45 DEG L BANK AND THE NOSE PITCHED DOWN. A GAR WAS EXECUTED AND SUBSEQUENT APCH TO RWY 4R WAS EXECUTED WITHOUT INCIDENT. IT IS UNKNOWN WHAT TYPE OF ACFT WE WERE FOLLOWING. HOWEVER SPACING LOOKED ADEQUATE VISUALLY AND THE ENTIRE APCH WAS FLOWN APPROX 1 1/2 DOTS HIGH ON GS. IN MY OPINION; THE ONLY METHOD OF PREVENTION WOULD BE GREATER SPACING BTWN ACFT; ESPECIALLY FOLLOWING HVY ACFT. SEVERAL PAX WERE IRATE BECAUSE NO PA WAS GIVEN AS TO REASON FOR OUR ABORTED LNDG. PA WAS NOT POSSIBLE DUE TO HVY WORKLOAD WITH ANOTHER IMMEDIATE VISUAL APCH. IN RETROSPECT; A PA SHOULD HAVE BEEN MADE UPON ARR AT GATE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR WAS THE FO ON A BAE ATP THAT HIT THE WAKE OF A B727 AND HAD TO MAKE A GAR AND AN APCH TO ANOTHER RWY. THE FO SEEMED TO BE MORE FOCUSED ON THE FACT THAT HE DID NOT MAKE AN ANNOUNCEMENT EXPLAINING THE EVENT TO THE PAX THAN ON THE DYNAMICS OF THE WAKE AND ITS AVOIDANCE. HE ADMITTED THAT THE B727 MAY HAVE BEEN AS LITTLE AS 2 MI AHEAD OF THEM DURING THE APCH AND HE FELT THAT THIS WAS NORMAL. THE ATP'S TCASII EQUIP WAS INOP ON THIS FLT AND HE HAD TO VISUALLY ESTIMATE HIS DISTANCE BEHIND THE B727. HOWEVER; HE STATED THAT THE B727 WAS JUST TURNING OFF OF THE RWY WHEN THEY HIT THE WAKE OVER THE THRESHOLD.