FK10 CREW MAY HAVE TAKEN OFF BELOW MINIMUMS.

Narrative

TKOF MINIMUM WX. AT THE GATE PRIOR TO DEP; ATIS RPTED LOW CEILINGS AND 1 SM VISIBILITY WITH ALL RWYS IN USE. THE BOOK SHOWED RWY 24 AS PRIMARY; ALONG WITH DATA FOR RWY 6. WE BRIEFED A RWY 24 TKOF WITH RVR TOUCHDOWN 6; MID RVR 6; ROLLOUT RVR 6 AS MINIMUMS. WE THEN BRIEFED OUR PLAN FOR A RETURN TO THE ARPT; IF NECESSARY; AND SET THE RADIOS FOR THE ILS RWY 6; WHICH PROVIDED LOWEST MINIMUMS. PRIOR TO OUR CALL FOR TAXI; AN ACFT AHEAD OF US REQUESTED RWY 6. OUR BOOK SHOWED A HIGHER RWY LIMITED WT FOR RWY 6 (A BETTER SAFETY MARGIN); SO WHEN ATC ASKED FOR OUR RWY PREFERENCE; WE REQUESTED AND WERE CLRED TO RWY 6. WE DID NOT CHK RWY 6 TKOF MINIMUMS. THERE WAS PATCHY FOG ON THE ARPT; BUT BOTH TXWY VISIBILITY AND RWY VISIBILITY WERE VERY GOOD. WHILE TAXIING; I RECALL HEARING ATC BROADCAST SOME FAIRLY HIGH RVR'S WITHOUT A REQUEST FOR AN ACKNOWLEDGEMENT. AT THE TIME; I RECALLED THE RVR TOUCHDOWN 6; MID RVR 6; ROLLOUT RVR 6 RVR WE HAD BRIEFED FOR RWY 24; AND WITH OUR PRESENT GOOD VISIBILITY; PRESSED ON; MAKING AN UNEVENTFUL TKOF AND DEP. IT WAS NOT UNTIL SOME 5 HRS AND 2 LEGS AFTER WHEN PREPARING FOR ANOTHER DEP THAT THE THOUGHT OCCURRED TO ME THAT WE NEVER SPECIFICALLY CHKED BHM RWY 6 DEP MINIMUMS. WHEN I CHKED; I FOUND A REQUIREMENT FOR AN RVR OF 50 OR 1 SM VISIBILITY. WE HAD AN ATIS RPTED VISIBILITY OF 1 SM; BUT SINCE I CANNOT RECALL THE SPECIFIC RVR RPTED DURING TAXI OUT; WE MAY HAVE DEPARTED RWY 6 WITH LESS THAN MINIMUM VISIBILITY.