INFLT WAKE TURB ENCOUNTER CAUSES AUTOPLT PITCH TRIM DISCONNECT.

Narrative

WHILE APCHING ATLANTA FROM THE SW; WE WERE GIVEN A DSCNT TO 4000 FT. THE AUTOPLT WAS ENGAGED AND WE WERE INDICATING 245 KTS. OUT OF THE CORNER OF MY EYE I CAUGHT SIGHT OF AN L1011 XING R TO L. APPROX 30 SECONDS LATER; WE HIT HIS WAKE AT A 90 DEG ANGLE. THE ENCOUNTER WAS VERY BRIEF BUT EXTREME. THE AUTOPLT DISCONNECTED ITSELF AND THE CAPT AND I BOTH LIGHTLY PLACED OUR HANDS ON THE CTLS TO GAIN CTL OF THE ACFT. SHORTLY AFTER THAT; WE ONCE AGAIN ENGAGED THE AUTOPLT AND THE REMAINING TURNS WERE DONE IN SMOOTH AIR WITH THE AUTOPLT ENGAGED. AFTER LINING UP ON FINAL; I DISENGAGED THE AUTOPLT AND PROCEEDED TO HAND FLY THE ACFT. THE L1011 LANDED ON RWY 27R. WE WERE INITIALLY GIVEN THIS RWY BUT RWY 27L BECAME AVAILABLE SO WE CHOSE IT. THE LNDG APCH WAS UNEVENTFUL. THE ACFT WOULD TRIM (PITCH) JUST FINE BUT I DID NOTICE SOMETHING ODD WITH THE PITCH FORCES WITH THE YOKE. I COULDN'T PUT MY FINGER ON IT AT THE TIME. ON LNDG ROLLOUT WE GOT A LEVEL 3 LLAS ALERT (EMER). FIRST THOUGHT WAS ENG FIRE. AS IT TURNS OUT IT WAS A PITCH DISCONNECT. AS BEST AS WE CAN FIGURE THE WAKE ENCOUNTER HAD DISCONNECTED THE CLUTCH INFLT BUT NOT FAR ENOUGH TO SET OFF THE SENSOR. AERODYNAMIC FORCES KEPT THE CTL SURFACES TOGETHER INFLT (SMOOTH CONDITIONS). WE WERE NEVER WARNED OF POSSIBLE WAKE. MAINT RECONNECTED THE CLUTCH AND WE FINISHED OUR TRIP. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR PARTICIPATED IN STRUCTURED WAKE TURB CALLBACK PROGRAM. FEELS THAT EDUCATIONAL FACTS AND EXPERIENCE SHOULD BE SHARED AND REVIEWED BY OTHER PLTS. LACK OF ATC ADVISORIES AND CREW COMPLACENCY LED TO THIS EVENT.