Narrative:

Upon receiving information 'XXXX' at the gate and calling for our IFR clearance and advising them we have 'XXXX' which indicated visibility 1 1/2 mi, we received our clearance and pushed back and were cleared to taxi to runway 31 nashville. Upon reaching the area just short of our departure runway and taxiing up to the hold short line we were cleared for takeoff and to turn to a certain heading at 2 or 3 DME which was followed by a 'visibility now 3/16 mi'. I was turning onto the runway and starting to push the power up for takeoff power when we heard the visibility report. Up until this point the first officer and I, the captain, had no reason to question the visibility reported by the ATIS 'XXXX' of 1 1/2 mi since at the takeoff roll we could see almost ot the other end of the runway. I thought rapidly and felt since I knew there was an ILS to runway 31 the takeoff legality was 600'-600'-600' RVR and that 3/16 was legal for our operation. With a takeoff clearance in hand I did not feel it necessary to ask permission to hold on an active runway while pulling out the charts to determine for sure if we were legal when I felt we really were. After takeoff I found to my dismay that runway 31 does not have RVR and we needed 1/4 mi visibility. We were illegal by 1/16 mi. Nobody informed us on taxi out that the ATIS had changed and we had no idea the visibility was being reported lower than the information on ATIS since it appeared we had at least 1 1/2 mi visibility if not more. Next time I will stop the aircraft and take whatever delay I must to determine our legality but as far as the tower never advising us the ATIS had changed and giving us the new visibility with a takeoff clearance, that was very poor communication on their part. If I had been given the new visibility report while I was taxiing out I would have had time to look up my legality just to be sure, as it was I felt rushed at the end.

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Original NASA ASRS Text

Title: ACR MLG TKOF IN WX BELOW RWY TKOF MINIMUMS.

Narrative: UPON RECEIVING INFO 'XXXX' AT THE GATE AND CALLING FOR OUR IFR CLRNC AND ADVISING THEM WE HAVE 'XXXX' WHICH INDICATED VISIBILITY 1 1/2 MI, WE RECEIVED OUR CLRNC AND PUSHED BACK AND WERE CLRED TO TAXI TO RWY 31 NASHVILLE. UPON REACHING THE AREA JUST SHORT OF OUR DEP RWY AND TAXIING UP TO THE HOLD SHORT LINE WE WERE CLRED FOR TKOF AND TO TURN TO A CERTAIN HDG AT 2 OR 3 DME WHICH WAS FOLLOWED BY A 'VISIBILITY NOW 3/16 MI'. I WAS TURNING ONTO THE RWY AND STARTING TO PUSH THE POWER UP FOR TKOF POWER WHEN WE HEARD THE VISIBILITY REPORT. UP UNTIL THIS POINT THE F/O AND I, THE CAPT, HAD NO REASON TO QUESTION THE VISIBILITY REPORTED BY THE ATIS 'XXXX' OF 1 1/2 MI SINCE AT THE TKOF ROLL WE COULD SEE ALMOST OT THE OTHER END OF THE RWY. I THOUGHT RAPIDLY AND FELT SINCE I KNEW THERE WAS AN ILS TO RWY 31 THE TKOF LEGALITY WAS 600'-600'-600' RVR AND THAT 3/16 WAS LEGAL FOR OUR OPERATION. WITH A TKOF CLRNC IN HAND I DID NOT FEEL IT NECESSARY TO ASK PERMISSION TO HOLD ON AN ACTIVE RWY WHILE PULLING OUT THE CHARTS TO DETERMINE FOR SURE IF WE WERE LEGAL WHEN I FELT WE REALLY WERE. AFTER TKOF I FOUND TO MY DISMAY THAT RWY 31 DOES NOT HAVE RVR AND WE NEEDED 1/4 MI VISIBILITY. WE WERE ILLEGAL BY 1/16 MI. NOBODY INFORMED US ON TAXI OUT THAT THE ATIS HAD CHANGED AND WE HAD NO IDEA THE VISIBILITY WAS BEING REPORTED LOWER THAN THE INFO ON ATIS SINCE IT APPEARED WE HAD AT LEAST 1 1/2 MI VISIBILITY IF NOT MORE. NEXT TIME I WILL STOP THE ACFT AND TAKE WHATEVER DELAY I MUST TO DETERMINE OUR LEGALITY BUT AS FAR AS THE TWR NEVER ADVISING US THE ATIS HAD CHANGED AND GIVING US THE NEW VISIBILITY WITH A TKOF CLRNC, THAT WAS VERY POOR COM ON THEIR PART. IF I HAD BEEN GIVEN THE NEW VISIBILITY REPORT WHILE I WAS TAXIING OUT I WOULD HAVE HAD TIME TO LOOK UP MY LEGALITY JUST TO BE SURE, AS IT WAS I FELT RUSHED AT THE END.

Data retrieved from NASA's ASRS site as of August 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.