Narrative:

While conducting an ILS to runway 18L at cvg in IMC, we noticed the abrupt change in terrain as our aircraft passed the FAF. As one crosses the ohio river, southbound, the terrain rises sharply at approximately 1 1/2 mi from the threshold of runway 18L. At 500' AGL our radio altimeter still showed 1000', then almost instantaneously changing to 500' AGL. We were on course and on glide path and at normal, stabilized approach speed. This change in radio altitude was enough to trigger a mode 2 (rising terrain) GPWS warning. At night, or in the WX, we would have had no choice but to execute our evasive procedure, which includes setting engine power to the mechanical stops. In this situation, a normal landing was accomplished. I contacted the approach control supervisor immediately after arrival by phone to appraise him of our experience. Dispatch was notified the next morning, and a company report filed. At the very least, the possibility of this phenomenon should be included in the NOTAMS, if not published on the actual approach chart. Both approach control and dispatch indicated this is a recurring problem.

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Original NASA ASRS Text

Title: FLT CREW OF MLG ON 18L APCH TO CVG HA GPWS ALERT CAUSED BY BLUFF ALONG RIVER EDGE 1 MILE FROM ARPT.

Narrative: WHILE CONDUCTING AN ILS TO RWY 18L AT CVG IN IMC, WE NOTICED THE ABRUPT CHANGE IN TERRAIN AS OUR ACFT PASSED THE FAF. AS ONE CROSSES THE OHIO RIVER, SBND, THE TERRAIN RISES SHARPLY AT APPROX 1 1/2 MI FROM THE THRESHOLD OF RWY 18L. AT 500' AGL OUR RADIO ALTIMETER STILL SHOWED 1000', THEN ALMOST INSTANTANEOUSLY CHANGING TO 500' AGL. WE WERE ON COURSE AND ON GLIDE PATH AND AT NORMAL, STABILIZED APCH SPD. THIS CHANGE IN RADIO ALT WAS ENOUGH TO TRIGGER A MODE 2 (RISING TERRAIN) GPWS WARNING. AT NIGHT, OR IN THE WX, WE WOULD HAVE HAD NO CHOICE BUT TO EXECUTE OUR EVASIVE PROC, WHICH INCLUDES SETTING ENG PWR TO THE MECHANICAL STOPS. IN THIS SITUATION, A NORMAL LNDG WAS ACCOMPLISHED. I CONTACTED THE APCH CTL SUPVR IMMEDIATELY AFTER ARR BY PHONE TO APPRAISE HIM OF OUR EXPERIENCE. DISPATCH WAS NOTIFIED THE NEXT MORNING, AND A COMPANY RPT FILED. AT THE VERY LEAST, THE POSSIBILITY OF THIS PHENOMENON SHOULD BE INCLUDED IN THE NOTAMS, IF NOT PUBLISHED ON THE ACTUAL APCH CHART. BOTH APCH CTL AND DISPATCH INDICATED THIS IS A RECURRING PROB.

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.