Narrative:

Arriving from den, WX was good enough for CAT 1 at top of descent, but we elected to brief and do CAT III approach, just in case. WX deteriorated on descent, but RVR varied between 800 and 1600. On final, configured and just inside the FAF, tower advised RVR, and midfield was called 600. I mentioned I thought we needed the midfield to be 700. The captain referred to a card he keeps in his pocket, and said all we need is 600. I was confused, but didn't think that was the time for a detailed discussion. We continued the approach and landed without incident. After shutdown, we talked about the situation. He referred to the fom where it says our company mins are 600, but we eventually agreed that the specific approach mins overrule that, and we should have gone around unless we could get the controller to advise of improvement prior to DH. Supplemental information from acn 595455: the first officer brought up the question of 700 RVR on the seattle approach chart. I looked at it again, and agreed that I probably made a mistake, but it was a classic 'simulator' question that happened quickly and in real time, and I did know that we were approved for 600 RVR, and of course, subsequently, the RVR went right back up again. In retrospect, and honest mistake and a good lesson.

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Original NASA ASRS Text

Title: B737 FLT CREW CONTINUES A CAT III APCH AND LANDS WHEN THE RVR IS RPTR BELOW PUBLISH MINIMUMS AT SEA.

Narrative: ARRIVING FROM DEN, WX WAS GOOD ENOUGH FOR CAT 1 AT TOP OF DSCNT, BUT WE ELECTED TO BRIEF AND DO CAT III APCH, JUST IN CASE. WX DETERIORATED ON DSCNT, BUT RVR VARIED BTWN 800 AND 1600. ON FINAL, CONFIGURED AND JUST INSIDE THE FAF, TWR ADVISED RVR, AND MIDFIELD WAS CALLED 600. I MENTIONED I THOUGHT WE NEEDED THE MIDFIELD TO BE 700. THE CAPT REFERRED TO A CARD HE KEEPS IN HIS POCKET, AND SAID ALL WE NEED IS 600. I WAS CONFUSED, BUT DIDN'T THINK THAT WAS THE TIME FOR A DETAILED DISCUSSION. WE CONTINUED THE APCH AND LANDED WITHOUT INCIDENT. AFTER SHUTDOWN, WE TALKED ABOUT THE SIT. HE REFERRED TO THE FOM WHERE IT SAYS OUR COMPANY MINS ARE 600, BUT WE EVENTUALLY AGREED THAT THE SPECIFIC APCH MINS OVERRULE THAT, AND WE SHOULD HAVE GONE AROUND UNLESS WE COULD GET THE CTLR TO ADVISE OF IMPROVEMENT PRIOR TO DH. SUPPLEMENTAL INFO FROM ACN 595455: THE FO BROUGHT UP THE QUESTION OF 700 RVR ON THE SEATTLE APCH CHART. I LOOKED AT IT AGAIN, AND AGREED THAT I PROBABLY MADE A MISTAKE, BUT IT WAS A CLASSIC 'SIMULATOR' QUESTION THAT HAPPENED QUICKLY AND IN REAL TIME, AND I DID KNOW THAT WE WERE APPROVED FOR 600 RVR, AND OF COURSE, SUBSEQUENTLY, THE RVR WENT RIGHT BACK UP AGAIN. IN RETROSPECT, AND HONEST MISTAKE AND A GOOD LESSON.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.