ATR 42 HAS MOMENTARY LOSS OF ACFT CTL DUE TO WAKE TURB FROM PRECEDING AIRBUS 340.

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ATR-42 ON A VISUAL APCH TO JFK RWY 4R. FOLLOWING AN AIRBUS 340; WE WERE APPROX 8 NM BEHIND (USING TCASII TO ESTIMATE) DISTANCE. WE HAD THE ILS TUNED IN AND WERE FLYING ABOVE GS WHEN WE ENCOUNTERED THE AIRBUS WAKE. IT WAS A VIOLENT ROLL. WE WERE ABLE TO COUNTERACT IT; HOWEVER; IT LASTED ONLY ABOUT 5 SECOND. THIS ENCOUNTER HAPPENED OUTSIDE THE HVY WAKE PARAMETERS. I FLY THE ATR- 42. IT HAS A SPLIT ELEVATOR DISCONNECT SYS. WHEREBY; IF 1 SIDE GETS JAMMED YOU CAN DISCONNECT AND RECOVER 1 SIDE. DURING THE WAKE ENCOUNTER; IT WAS ROUGH ENOUGH TO ELICIT A MOMENTARY (CREW ALERT COMPUTER) 'WARNING' OF A 'PITCH (ELEVATOR) DISCONNECT' FOR A SPLIT SECOND; WHICH MEANS IT CAME VERY CLOSE TO SPLITTING BY ITSELF. LUCKILY IT DID NOT. CONCLUSION: IT APPEARS THAT NEW GENERATION ACFT ARE PRODUCING WAKES THAT ARE GREATER THAN THEIR PREDECESSORS AND BEAR STUDYING. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATES THAT THE CREWS ARE VERY AWARE OF THE EFFECTS OF WAKE TURB AND THEY TRY TO AVOID IT. IN THIS CASE; THEY WERE 8 MI BEHIND THE A340 IN THEIR ATR-42 AND OFFSET TO THE LOC COURSE WHEN THE WAKE WAS ENCOUNTERED. PART OF THE PROB IS THAT EVERYONE IS VECTORED AT THE SAME ALTS WHILE IN THE PATTERN AND ON A CALM DAY SOME OF THE WAKES ARE VERY PERSISTENT. ANOTHER FACTOR THE RPTR HAS NOTED IS THAT IN WX THE CTLRS WILL HAVE AS LITTLE AS 2 1/2 MI IN-TRAIL ON THE ILS APCH. THE RPTR THINKS THAT THE NEWER TECHNOLOGY ACFT HAVE MUCH MORE VIOLENT VORTICES THAN OLDER ACFT. HE ALSO DOES NOT THINK THAT CTLRS ARE CONCERNED ABOUT THE PROB. HE FEELS THAT THE HVY; NEW TECH ACFT SHOULD BE SENT TO A SEPARATE RWY AND FROM A SEPARATE PATTERN.