Narrative:

This event was the product of preconceived expectations, complacency, and a suddenly and rapidly changing set of circumstances. I was the PF. Our flight was inbound to pit with the ATIS reporting winds 300 degrees at 10 KTS, visibility 10 mi, 3500 ft broken, 4400 ft overcast. The expectation was that we would be flying a visual approach to runway 32 and would back it up with the ILS for runway alignment and approach slope guidance. The approach was briefed as a visual and as such there was no mention of the required ILS minimum. Because it was going to be a routine visual approach, my approach plate binder was open to the proper plate, but I had not put the plate up on the control yoke. As we approached the airport and were being vectored onto the final approach course, the visibility began dropping rapidly due to apparently fast moving and intense snow showers. As the visibility began dropping progressively first at the rollout end of the runway and then mid runway and then the approach end, it became clear that a snow shower was moving across the field and that the approach might very possibly be one to minimums. For some reason I had it in my head that the minimums were 200 ft and 1/2 mi or RVR 1800 ft. The minimums are in fact 200 ft and 1 mi or RVR of 5000 ft. At one point an aircraft behind us told the controller that he would need an RVR value of 5000 ft and I remember thinking 'he must be on a high minimums.' as the visibility was dropping, we were on the localizer at 3000 ft and starting down or about to start down. I was hand flying the approach so the level of concentration on the instruments went up measurably as the visibility values dropped. In the backgnd, I could hear the 3 RVR values being read off by the controller and they were generally going lower and lower. At some point during the approach, the approach RVR value went below 5000 ft, but as I was mistakenly thinking we only required a RVR value of 1800 ft, I continued the approach. We may have in fact been on the final approach segment before the value dropped below 5000 ft. If we were, we were legal -- if not, we weren't. I just don't know for sure, and of course, therein is the problem. Legality, is of course a primary concern, but the real 'problem' was that I was operating using flawed logic brought about by complacency. The complacency might have been the result of understandable circumstances, but it was still my complacency and I dislike that part most of all. The first officer had his plate up on his control column and once it became apparent the ILS had the earmarks of an ILS for real and not just a way to transition to visual conditions, he made all the normal altitude calls. He did not mention the 5000 ft RVR requirement. It may be that he felt that we had passed the point in the approach where that was a factor. He may have been right. I don't know and that brings us back to the real problem. Once below the clouds we had good visibility up to the edge of the snow shower, which by then extended just past the approach lights. As we got down to minimums the visibility was restr, but seeing the approach lights and the runway was not a problem. The landing was not remarkable other than it was snowing hard over the runway for an otherwise sunny april day. It wasn't until we cleared the runway and were 1/2 way to the terminal that it occurred to me that we might have initiated an approach without proper landing minimums. In the future, any time I am shooting an 'ILS to the visual' I will put the approach chart up on the control column where I can easily refer to it should the need arise.

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Original NASA ASRS Text

Title: A DHC8 PIC TELLS OF POSSIBLY NOT ADHERING TO PUBLISHED WX MINIMUMS FOR LNDG, RELATED TO THE RVR REQUIREMENTS, WHEN ENCOUNTERING AN UNEXPECTED SNOW STORM WHEN LNDG RWY 30, PIT, PA.

Narrative: THIS EVENT WAS THE PRODUCT OF PRECONCEIVED EXPECTATIONS, COMPLACENCY, AND A SUDDENLY AND RAPIDLY CHANGING SET OF CIRCUMSTANCES. I WAS THE PF. OUR FLT WAS INBOUND TO PIT WITH THE ATIS RPTING WINDS 300 DEGS AT 10 KTS, VISIBILITY 10 MI, 3500 FT BROKEN, 4400 FT OVCST. THE EXPECTATION WAS THAT WE WOULD BE FLYING A VISUAL APCH TO RWY 32 AND WOULD BACK IT UP WITH THE ILS FOR RWY ALIGNMENT AND APCH SLOPE GUIDANCE. THE APCH WAS BRIEFED AS A VISUAL AND AS SUCH THERE WAS NO MENTION OF THE REQUIRED ILS MINIMUM. BECAUSE IT WAS GOING TO BE A ROUTINE VISUAL APCH, MY APCH PLATE BINDER WAS OPEN TO THE PROPER PLATE, BUT I HAD NOT PUT THE PLATE UP ON THE CTL YOKE. AS WE APCHED THE ARPT AND WERE BEING VECTORED ONTO THE FINAL APCH COURSE, THE VISIBILITY BEGAN DROPPING RAPIDLY DUE TO APPARENTLY FAST MOVING AND INTENSE SNOW SHOWERS. AS THE VISIBILITY BEGAN DROPPING PROGRESSIVELY FIRST AT THE ROLLOUT END OF THE RWY AND THEN MID RWY AND THEN THE APCH END, IT BECAME CLR THAT A SNOW SHOWER WAS MOVING ACROSS THE FIELD AND THAT THE APCH MIGHT VERY POSSIBLY BE ONE TO MINIMUMS. FOR SOME REASON I HAD IT IN MY HEAD THAT THE MINIMUMS WERE 200 FT AND 1/2 MI OR RVR 1800 FT. THE MINIMUMS ARE IN FACT 200 FT AND 1 MI OR RVR OF 5000 FT. AT ONE POINT AN ACFT BEHIND US TOLD THE CTLR THAT HE WOULD NEED AN RVR VALUE OF 5000 FT AND I REMEMBER THINKING 'HE MUST BE ON A HIGH MINIMUMS.' AS THE VISIBILITY WAS DROPPING, WE WERE ON THE LOC AT 3000 FT AND STARTING DOWN OR ABOUT TO START DOWN. I WAS HAND FLYING THE APCH SO THE LEVEL OF CONCENTRATION ON THE INSTS WENT UP MEASURABLY AS THE VISIBILITY VALUES DROPPED. IN THE BACKGND, I COULD HEAR THE 3 RVR VALUES BEING READ OFF BY THE CTLR AND THEY WERE GENERALLY GOING LOWER AND LOWER. AT SOME POINT DURING THE APCH, THE APCH RVR VALUE WENT BELOW 5000 FT, BUT AS I WAS MISTAKENLY THINKING WE ONLY REQUIRED A RVR VALUE OF 1800 FT, I CONTINUED THE APCH. WE MAY HAVE IN FACT BEEN ON THE FINAL APCH SEGMENT BEFORE THE VALUE DROPPED BELOW 5000 FT. IF WE WERE, WE WERE LEGAL -- IF NOT, WE WEREN'T. I JUST DON'T KNOW FOR SURE, AND OF COURSE, THEREIN IS THE PROB. LEGALITY, IS OF COURSE A PRIMARY CONCERN, BUT THE REAL 'PROB' WAS THAT I WAS OPERATING USING FLAWED LOGIC BROUGHT ABOUT BY COMPLACENCY. THE COMPLACENCY MIGHT HAVE BEEN THE RESULT OF UNDERSTANDABLE CIRCUMSTANCES, BUT IT WAS STILL MY COMPLACENCY AND I DISLIKE THAT PART MOST OF ALL. THE FO HAD HIS PLATE UP ON HIS CTL COLUMN AND ONCE IT BECAME APPARENT THE ILS HAD THE EARMARKS OF AN ILS FOR REAL AND NOT JUST A WAY TO TRANSITION TO VISUAL CONDITIONS, HE MADE ALL THE NORMAL ALT CALLS. HE DID NOT MENTION THE 5000 FT RVR REQUIREMENT. IT MAY BE THAT HE FELT THAT WE HAD PASSED THE POINT IN THE APCH WHERE THAT WAS A FACTOR. HE MAY HAVE BEEN RIGHT. I DON'T KNOW AND THAT BRINGS US BACK TO THE REAL PROB. ONCE BELOW THE CLOUDS WE HAD GOOD VISIBILITY UP TO THE EDGE OF THE SNOW SHOWER, WHICH BY THEN EXTENDED JUST PAST THE APCH LIGHTS. AS WE GOT DOWN TO MINIMUMS THE VISIBILITY WAS RESTR, BUT SEEING THE APCH LIGHTS AND THE RWY WAS NOT A PROB. THE LNDG WAS NOT REMARKABLE OTHER THAN IT WAS SNOWING HARD OVER THE RWY FOR AN OTHERWISE SUNNY APRIL DAY. IT WASN'T UNTIL WE CLRED THE RWY AND WERE 1/2 WAY TO THE TERMINAL THAT IT OCCURRED TO ME THAT WE MIGHT HAVE INITIATED AN APCH WITHOUT PROPER LNDG MINIMUMS. IN THE FUTURE, ANY TIME I AM SHOOTING AN 'ILS TO THE VISUAL' I WILL PUT THE APCH CHART UP ON THE CTL COLUMN WHERE I CAN EASILY REFER TO IT SHOULD THE NEED ARISE.

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.