FLC ENCOUNTER UNCOMMANDED 30 DEG ROLL ON FINAL 5 MI BEHIND B727.

Narrative

SHORTLY AFTER INTERCEPTING LOC FOR RWY 27L AT ORD; ACFT BEGAN AN ABRUPT UNCOMMANDED L ROLL. 90 DEGS OF R AILERON INPUT AND FULL R RUDDER AND FORWARD STICK WERE REQUIRED TO STOP THE ROLL AND RETURN TO CTLED FLT. ACFT WT WAS 110000 LBS. SPD WAS 180 KTS. CONFIGN WAS FLAPS 15 DEGS; GEAR UP AND FLT SPOILERS RETRACTED. WE WERE APPROX 4 MI BEHIND A B727-200. TWR RPTED NO HVY JET TFC. MAX BANK ANGLE IS ESTIMATED TO BE ABOUT 35-40 DEGS WHEN THE ROLL WAS STOPPED. THERE WERE NO INJURIES RPTED BY THE FLT ATTENDANTS OR PAX. THE PREPARE FOR LNDG HAD BEEN DONE SEVERAL MINS BEFORE WHILE ON DOWNWIND. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED IN THE CALLBACK HE HAD FLAPS 11 DEGS. IN THE RPT HE SAID THE FLAPS WERE 15 DEGS. THE RPTR STATED HE HAD BEEN FLYING 25 YRS AND NEVER ENCOUNTERED SUCH ALARMING WAKE. THE CHARACTERISTIC OF THE WAKE WAS A SUSTAINED LOSS OF ROLL CTL FOR 5-6 SECONDS. DURING THE SLOW ROLL THE OPPOSITE AILERON AND RUDDER WERE APPLIED TO CTL LIMITS WITHOUT ANY APPARENT ACFT RESPONSE OR REDUCTION OF ROLL RATE UNTIL FORWARD ELEVATOR PRESSURE WAS APPLIED. THE RPTR STATED HE WAS ABOUT 12 MI OUT ON FINAL ON GS BTWN 3500 AND 4000 FT AGL. HE STATED FLT CONDITIONS WERE IMC AND IT WAS DAYLIGHT. HE STATED HE WAS THE CAPT; HE WAS FLYING AND HE HAD ABOUT 9000 HRS TOTAL TIME; 6000 HRS IN THE MD80 AND 210 HRS IN THE LAST 90 DAYS. THE CREW WERE TALKING WITH APCH CTL.