Narrative:

Sea center cleared us to seatac via 'malay 1 arrival, btg transition.' we were given holding instructions for btg with an efc of about XA00 elapsed time. After about 20 mins of hold we were given a vector towards sea and told to expect holding at glasr or jaksn intersection on the glasr 2 arrival (north of sea). We eventually held at jaksn for about 50 mins. While holding there, the sea WX was mostly below CAT III mins but occasionally fluctuating above. Mid and rollout were generally ok, but touchdown RVR seemed to want to stay at 600. When we were near our diversion fuel figure I informed center of this and said we would soon have to divert to pdx. They said it looked like things were improving and they would vector us for an approach if we desired. I accepted as this would head us south toward pdx and also enable us to 'get in' if the RVR improved. We were vectored and cleared for an approach. From this point on I recall mid and rollout RVR as being at 1000 with touchdown varying between 600 and 800 ft. Mins were 700 ft. From the cockpit it did not look bad at all. Except for patches of ground fog it was bright and sunny. I could see 80-90 percent of the surface. It did look like it was clearing up rapidly near the airport, I'm not sure what the touchdown RVR was when we were cleared for the approach, but after established on the GS it went to 600 ft (below mins). As we continued we kept asking for RVR's, hoping for a 'special observation' that would enable us to take a 'look see.' we have only been doing CAT III approachs in the medium large transport for a little over a month. My CAT III certification training was 9 months ago. With touchdown RVR at 600, mid and rollout at 1000, I wasn't sure if company SOP allowed me to go on. The copilot said nothing nor did I ask. It just didn't look bad, so I continued. I saw the approach lights at 150-200 ft (well above CAT ii mins), and the runway touchdown zone at 100-120 ft (well above CAT III) a touchdown RVR looked fine so I continued to automatic land. Visibility on rollout was at least 1000 ft. Obviously I was prepared to go around, if all was not well. I reported my observations to the tower. They immediately reported touchdown RVR at 1000 ft. There were no missed approachs after we landed and visibility rapidly improved. Afterwards I reviewed our company CAT III automatic land procedures. My 'gut feeling' was correct. I should not have started or continued the approach if touchdown RVR went below min of 700. This is different than CAT ii 'look see' and should be emphasized. I really stuck my neck out.

Related reports:

Google
 

Original NASA ASRS Text

Title: RPTR CONCERNED THAT HE MAY HAVE LANDED SEA BELOW RVR MINS.

Narrative: SEA CENTER CLRED US TO SEATAC VIA 'MALAY 1 ARR, BTG TRANSITION.' WE WERE GIVEN HOLDING INSTRUCTIONS FOR BTG WITH AN EFC OF ABOUT XA00 ELAPSED TIME. AFTER ABOUT 20 MINS OF HOLD WE WERE GIVEN A VECTOR TOWARDS SEA AND TOLD TO EXPECT HOLDING AT GLASR OR JAKSN INTXN ON THE GLASR 2 ARR (N OF SEA). WE EVENTUALLY HELD AT JAKSN FOR ABOUT 50 MINS. WHILE HOLDING THERE, THE SEA WX WAS MOSTLY BELOW CAT III MINS BUT OCCASIONALLY FLUCTUATING ABOVE. MID AND ROLLOUT WERE GENERALLY OK, BUT TOUCHDOWN RVR SEEMED TO WANT TO STAY AT 600. WHEN WE WERE NEAR OUR DIVERSION FUEL FIGURE I INFORMED CENTER OF THIS AND SAID WE WOULD SOON HAVE TO DIVERT TO PDX. THEY SAID IT LOOKED LIKE THINGS WERE IMPROVING AND THEY WOULD VECTOR US FOR AN APCH IF WE DESIRED. I ACCEPTED AS THIS WOULD HEAD US S TOWARD PDX AND ALSO ENABLE US TO 'GET IN' IF THE RVR IMPROVED. WE WERE VECTORED AND CLRED FOR AN APCH. FROM THIS POINT ON I RECALL MID AND ROLLOUT RVR AS BEING AT 1000 WITH TOUCHDOWN VARYING BTWN 600 AND 800 FT. MINS WERE 700 FT. FROM THE COCKPIT IT DID NOT LOOK BAD AT ALL. EXCEPT FOR PATCHES OF GND FOG IT WAS BRIGHT AND SUNNY. I COULD SEE 80-90 PERCENT OF THE SURFACE. IT DID LOOK LIKE IT WAS CLRING UP RAPIDLY NEAR THE ARPT, I'M NOT SURE WHAT THE TOUCHDOWN RVR WAS WHEN WE WERE CLRED FOR THE APCH, BUT AFTER ESTABLISHED ON THE GS IT WENT TO 600 FT (BELOW MINS). AS WE CONTINUED WE KEPT ASKING FOR RVR'S, HOPING FOR A 'SPECIAL OBSERVATION' THAT WOULD ENABLE US TO TAKE A 'LOOK SEE.' WE HAVE ONLY BEEN DOING CAT III APCHS IN THE MLG FOR A LITTLE OVER A MONTH. MY CAT III CERTIFICATION TRAINING WAS 9 MONTHS AGO. WITH TOUCHDOWN RVR AT 600, MID AND ROLLOUT AT 1000, I WASN'T SURE IF COMPANY SOP ALLOWED ME TO GO ON. THE COPLT SAID NOTHING NOR DID I ASK. IT JUST DIDN'T LOOK BAD, SO I CONTINUED. I SAW THE APCH LIGHTS AT 150-200 FT (WELL ABOVE CAT II MINS), AND THE RWY TOUCHDOWN ZONE AT 100-120 FT (WELL ABOVE CAT III) A TOUCHDOWN RVR LOOKED FINE SO I CONTINUED TO AUTO LAND. VISIBILITY ON ROLLOUT WAS AT LEAST 1000 FT. OBVIOUSLY I WAS PREPARED TO GAR, IF ALL WAS NOT WELL. I RPTED MY OBSERVATIONS TO THE TWR. THEY IMMEDIATELY RPTED TOUCHDOWN RVR AT 1000 FT. THERE WERE NO MISSED APCHS AFTER WE LANDED AND VISIBILITY RAPIDLY IMPROVED. AFTERWARDS I REVIEWED OUR COMPANY CAT III AUTO LAND PROCS. MY 'GUT FEELING' WAS CORRECT. I SHOULD NOT HAVE STARTED OR CONTINUED THE APCH IF TOUCHDOWN RVR WENT BELOW MIN OF 700. THIS IS DIFFERENT THAN CAT II 'LOOK SEE' AND SHOULD BE EMPHASIZED. I REALLY STUCK MY NECK OUT.

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.