737 EXPERIENCES WAKE TURB FOLLOWING ANOTHER 737.

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ENCOUNTERED WAKE TURB AT 2000 FT BEHIND A B-737 4 MI AHEAD. WE WERE AT 200 KIAS; 2000 FT; FLAPS GOING TO POS 5; AUTOPLT OFF; WHEN WE ENTERED PRECEDING B-737'S VORTICES. OUR B-737 FIRST FELT LIKE LIGHT TURB; THEN R WING DROPPED QUICKLY. I USED RUDDER AND YOKE TO BRING WING BACK TO LEVEL; THEN WING DROPPED TO THE L BEFORE I COULD AGAIN PICK IT UP WITH RUDDER AND YOKE. PLANE CONTINUED TO ROLL; YAW; AND HEAVE FOR 10 SECONDS OR SO. WE WERE TRAPPED INSIDE A VORTEX; NOT JUST TRANSITORY. ESTIMATE WING DROPS OF AROUND 25 DEGS L AND R. HAD WE BEEN IN AUTOPLT CTL I BELIEVE THE ACFT WOULD HAVE GONE PAST 90 DEGS WING DOWN. B-737 AUTOPLTS DON'T HAVE RUDDER AUTH -- ONLY THE PLT DOES. IN WAKE TURB; DISCONNECT THE AUTOPLT AND FLY THE JET! CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR HAS VERY POSITIVE IDEAS REGARDING USE OF AUTOPLT ON APCH. HE FEELS STRONGLY THAT ONE SHOULD BE PREPARED TO CLICK IT OFF IMMEDIATELY IF ACFT GIVES ANY ADVERSE INDICATIONS OF UNCTLED INPUT OR FORCES. MOST AUTOPLTS TAKE 8 SECONDS TO KICK OFF ON THEIR OWN IF MOTION IS BEYOND AUTOPLT CAPABILITY. THAT IS TOO LONG IN SUCH A SIT AS THIS. THE AUTOPLT DOES NOT USE RUDDER INPUT TO MAKE CORRECTIONS AND THAT IS PRECISELY WHAT WAS NEEDED IN THIS INCIDENT TO REGAIN CTL. RPTR'S COMPANY IS ABOUT TO INSTALL HUD AND THIS WILL REQUIRE A HAND FLOWN ACFT ON APCH. HE FEELS THIS WILL BE A MUCH BETTER APCH. RPTR CALLED HIS CHIEF PLT AS HE IS A MEMBER OF THE SAFETY COMMITTEE AND WANTED TO PULL THE FLT DATA RECORDER. RPTR WAS IN THE PROCESS OF WRITING A SAFETY ARTICLE ON WAKE TURB AND GOT FIRST HAND KNOWLEDGE FOR THE ARTICLE.