RPTED SIT OF RPTR'S F100 AT TOUCHDOWN WHEN A DEPARTING ACFT WAS ROTATING ON THE SAME RWY.

Narrative

WE WERE CLRED TO LAND RWY 30L STL. 1 ACFT CLRED FOR TKOF PRIOR TO LNDG AT APPROX 500 FT. AT TOUCHDOWN; ACFT WAS ROTATING. LNDG WAS UNEVENTFUL. WE CALLED TWR TO DISCUSS THE SPACING AND WAS TOLD THEY ARE ONLY REQUIRED 6000 FT AND SIGN OF ROTATION FOR SEPARATION. I TRIED TO DISCUSS THE RAMIFICATIONS OF MISSED APCH AND/OR HIGH SPD ABORT FROM OUR PERSPECTIVE. WAS TOLD NORMAL OPS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR THOUGHT THE DEPARTING ACFT WAS A B727. THE ACFT WAS ON THE RWY AND NOT AIRBORNE WHEN RPTR'S ACFT TOUCHED DOWN. RPTR THOUGHT IT WAS BETTER TO LAND THAN GO AROUND AS THEY WOULD HAVE TO CLB OUT OVER THE DEPARTING B727. RPTR WAS PF AND INDICATED THAT TFC WAS NOT HVY AT THE TIME AND THAT THE B727 WAITED IN POS WHILE ANOTHER ACFT CROSSED THE RWY BEFORE BEING CLRED FOR TKOF. RPTR CLAIMED THERE HAVE BEEN OTHER OCCASIONS WHERE SEPARATION BTWN ARRS AND DEPS HAS BEEN PRETTY CLOSE BUT NOT AS CLOSE AS THIS ONE. RPTR ALLEGED OTHER PLTS HAVE EXPRESSED CONCERN FOR THE ARR/DEP SEPARATION. SUPPLEMENTAL INFO FROM ACN 403799: WE TOUCHED DOWN WHEN OTHER ACFT WAS LIFTING OFF. A CALL TO THE TWR SUPVR INDICATED THIS WAS NORMAL OP -- 6000 FT AND SIGN OF ROTATION. QUESTION: ISN'T TWR BETTING ON THE COME? THEY HAD NO IDEA THAT ACFT WOULD BE ABLE TO ROTATE WHEN WE WERE CLRED TO LAND. IT IS DOUBTFUL THAT VISUAL COULD BE MAINTAINED ON AN ACFT CLBING BENEATH US DURING OUR GAR. THIS SPACING IS UNSAFE.