Narrative:

Hourly sequence report and ATIS stated prevailing visibility 1/8 mi. Tower visibility 1/4 mi, RVR out of service. Our operations specifications allow 1/4 mi takeoff as well as takeoff minimums on back of chart at eug. Another air carrier departed 10 min ahead of us with the same visibility. The eug tower cleared us for takeoff then immediately notified FAA of our departure below minimums. Since tower visibility was reported 1/4 mi we felt we had legal minimums. Not until we were later notified of the investigation into this matter did we find out the lower of the 2 visibilities is used to determine takeoff minimums. Tower visibility and prevailing visibility measurements are taken at separate sites at eug. The ground and tower controllers also did not inform us we were departing below minimums. It is the crews fault for not knowing about the most restrictive of the 2 visibilities used for takeoff. The ATC controller knew but did not convey that information to us and the preceeding air carrier that departed. Yet ATC was quick to notify the FAA of the violations. Better communication can prevent these situations. Had ATC informed us and the preceeding crew of our impending errors we certainly would not have departed. The tower was not busy at the time either as we were the only 2 aircraft operating in their area at the time.

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Original NASA ASRS Text

Title: WX REPORT ON THE SEQUENCE ONE EIGHTH MILE VISIBLITY. TWR GAVE ONE QUARTER. PLT TOOK TWR VISIBILITY AND TOOK OFF. TWR CTLR ADVISED FAA OF BELOW ARPT MINIMUMS TKOF.

Narrative: HOURLY SEQUENCE RPT AND ATIS STATED PREVAILING VISIBILITY 1/8 MI. TWR VISIBILITY 1/4 MI, RVR OUT OF SVC. OUR OPS SPECS ALLOW 1/4 MI TKOF AS WELL AS TKOF MINIMUMS ON BACK OF CHART AT EUG. ANOTHER AIR CARRIER DEPARTED 10 MIN AHEAD OF US WITH THE SAME VISIBILITY. THE EUG TWR CLRED US FOR TKOF THEN IMMEDIATELY NOTIFIED FAA OF OUR DEP BELOW MINIMUMS. SINCE TWR VISIBILITY WAS RPTED 1/4 MI WE FELT WE HAD LEGAL MINIMUMS. NOT UNTIL WE WERE LATER NOTIFIED OF THE INVESTIGATION INTO THIS MATTER DID WE FIND OUT THE LOWER OF THE 2 VISIBILITIES IS USED TO DETERMINE TKOF MINIMUMS. TWR VISIBILITY AND PREVAILING VISIBILITY MEASUREMENTS ARE TAKEN AT SEPARATE SITES AT EUG. THE GND AND TWR CTLRS ALSO DID NOT INFORM US WE WERE DEPARTING BELOW MINIMUMS. IT IS THE CREWS FAULT FOR NOT KNOWING ABOUT THE MOST RESTRICTIVE OF THE 2 VISIBILITIES USED FOR TKOF. THE ATC CTLR KNEW BUT DID NOT CONVEY THAT INFO TO US AND THE PRECEEDING AIR CARRIER THAT DEPARTED. YET ATC WAS QUICK TO NOTIFY THE FAA OF THE VIOLATIONS. BETTER COM CAN PREVENT THESE SITUATIONS. HAD ATC INFORMED US AND THE PRECEEDING CREW OF OUR IMPENDING ERRORS WE CERTAINLY WOULD NOT HAVE DEPARTED. THE TWR WAS NOT BUSY AT THE TIME EITHER AS WE WERE THE ONLY 2 ACFT OPERATING IN THEIR AREA AT THE TIME.

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.