Narrative:

ATIS visibility was reported as 2 mi in fog. Approach control had cleared us for the ILS runway 7 sba approach. We were in a position at which we could descend to gsia (G/south intercept altitude). Approach control told us to contact the tower. We checked in with the tower and were advised by the tower that runway 7 RVR was less than 2400 (I cannot recall the exact figure given). The captain said we could not continue the approach since we were outside the FAF (final approach fix). I agreed (since we were on gsia but had not yet intercepted the G/south). Next however, the captain asked for the visibility at the field. Surprisingly the tower read back 2 mi. The captain then said we were ok to continue the approach since the visibility was above 1/2 mi and we only needed 1/2 mi or 2400 RVR. He asked if I agreed. I responded that as I understood RVR was governing to a runway for which RVR is reported. The captain said 'no, the or allows us to have either', therefore, he concluded we were legal to continue the approach. We continued the approach. I felt uncomfortable. We saw the ALS (approach lighting system) and then the runway at about 300'-350'. The aircraft was landed uneventfully. I believe this situation was the result of a misinterp of the visibility requirements presented on the approach chart and the captain's misunderstanding of controling determination of visibility. Far 135 pt 225 could be made more specific on this area on how to determine minimum visibility requirements to continue an approach. 135 operations specifications does address the issue, but many pilots I spoke to consider the RVR/visibility determination to be a grey area. I however still interpret as RVR governs.

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Original NASA ASRS Text

Title: COMMUTER FLT CREW'S DECISION TO USE TWR REPORTER VISIBILITY INSTEAD OF RVR LEADS TO BELOW MINIMUMS APCH.

Narrative: ATIS VISIBILITY WAS RPTED AS 2 MI IN FOG. APCH CTL HAD CLRED US FOR THE ILS RWY 7 SBA APCH. WE WERE IN A POS AT WHICH WE COULD DSND TO GSIA (G/S INTERCEPT ALT). APCH CTL TOLD US TO CONTACT THE TWR. WE CHKED IN WITH THE TWR AND WERE ADVISED BY THE TWR THAT RWY 7 RVR WAS LESS THAN 2400 (I CANNOT RECALL THE EXACT FIGURE GIVEN). THE CAPT SAID WE COULD NOT CONTINUE THE APCH SINCE WE WERE OUTSIDE THE FAF (FINAL APCH FIX). I AGREED (SINCE WE WERE ON GSIA BUT HAD NOT YET INTERCEPTED THE G/S). NEXT HOWEVER, THE CAPT ASKED FOR THE VISIBILITY AT THE FIELD. SURPRISINGLY THE TWR READ BACK 2 MI. THE CAPT THEN SAID WE WERE OK TO CONTINUE THE APCH SINCE THE VISIBILITY WAS ABOVE 1/2 MI AND WE ONLY NEEDED 1/2 MI OR 2400 RVR. HE ASKED IF I AGREED. I RESPONDED THAT AS I UNDERSTOOD RVR WAS GOVERNING TO A RWY FOR WHICH RVR IS RPTED. THE CAPT SAID 'NO, THE OR ALLOWS US TO HAVE EITHER', THEREFORE, HE CONCLUDED WE WERE LEGAL TO CONTINUE THE APCH. WE CONTINUED THE APCH. I FELT UNCOMFORTABLE. WE SAW THE ALS (APCH LIGHTING SYS) AND THEN THE RWY AT ABOUT 300'-350'. THE ACFT WAS LANDED UNEVENTFULLY. I BELIEVE THIS SITUATION WAS THE RESULT OF A MISINTERP OF THE VISIBILITY REQUIREMENTS PRESENTED ON THE APCH CHART AND THE CAPT'S MISUNDERSTANDING OF CTLING DETERMINATION OF VISIBILITY. FAR 135 PT 225 COULD BE MADE MORE SPECIFIC ON THIS AREA ON HOW TO DETERMINE MINIMUM VISIBILITY REQUIREMENTS TO CONTINUE AN APCH. 135 OPS SPECS DOES ADDRESS THE ISSUE, BUT MANY PLTS I SPOKE TO CONSIDER THE RVR/VISIBILITY DETERMINATION TO BE A GREY AREA. I HOWEVER STILL INTERPRET AS RVR GOVERNS.

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.