Narrative:

On arrival in sdf ATIS was 340-07; 7SM; -RA; 006SCT; 036 ovc 12/11 29.47. ILS runway 35R and 35L (GS OTS) runway 35R has a displaced threshold as they are doing runway construction on the approach end. I briefed the runway 35R ILS. When we checked in on approach; he said we would be #9 for runway 35R and to expect runway 35L. I then briefed the runway 35L ILS (GS out) with the use of the autoplt; and elected to not use company procedures as the WX was above minimums for this procedure. On altitude hold at 2400 ft the first officer selected 900 ft for minimums. We had both mentioned in the briefing that 1400 ft was the MDA if we didn't have DME to identify 4.5 irli and so we agreed our MDA was 900 ft with DME. At the FAF crdnl; I selected 1100 FPM and continued to flaps 40 degrees and we completed the before landing checklist. We both had the runway in sight; but continued the approach. I had reduced the descent to 1000 FPM and as we approached MDA we received one terrain alert. I began the climb to 1100 ft and we never received it again. Simultaneously; the tower gave us a low terrain alert and a new altimeter setting of 29.52. We only received one alert from the GPWS; and the runway was in sight throughout the entire event. We then continued the approach and landed without further incident. We both debriefed one another when we got to the gate. I believe that the first error was made in doing a rushed briefing for a non-precision approach. In doing so; we both missed the 4.5 irli step-down fix of 1400 ft. Our attention had been drawn to the bottom of the approach plate believing that 1400 ft was only a factor if the DME was inoperative. I did not see the step-down on the plate. The first officer even mentioned it when setting the MDA; and we had a quick discussion about it. It is my belief that he caught it at the last minute. When we received the terrain alert; I had the field in sight. I began adding power; although I did not call 'emergency thrust;' climbed to 1100 ft and then we never received the alert again. We both felt the closure rate must have set it off.

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Original NASA ASRS Text

Title: B737-700 FLT CREW HAS A GPWS TERRAIN ALERT DURING APCH TO SDF.

Narrative: ON ARR IN SDF ATIS WAS 340-07; 7SM; -RA; 006SCT; 036 OVC 12/11 29.47. ILS RWY 35R AND 35L (GS OTS) RWY 35R HAS A DISPLACED THRESHOLD AS THEY ARE DOING RWY CONSTRUCTION ON THE APCH END. I BRIEFED THE RWY 35R ILS. WHEN WE CHKED IN ON APCH; HE SAID WE WOULD BE #9 FOR RWY 35R AND TO EXPECT RWY 35L. I THEN BRIEFED THE RWY 35L ILS (GS OUT) WITH THE USE OF THE AUTOPLT; AND ELECTED TO NOT USE COMPANY PROCS AS THE WX WAS ABOVE MINIMUMS FOR THIS PROC. ON ALT HOLD AT 2400 FT THE FO SELECTED 900 FT FOR MINIMUMS. WE HAD BOTH MENTIONED IN THE BRIEFING THAT 1400 FT WAS THE MDA IF WE DIDN'T HAVE DME TO IDENT 4.5 IRLI AND SO WE AGREED OUR MDA WAS 900 FT WITH DME. AT THE FAF CRDNL; I SELECTED 1100 FPM AND CONTINUED TO FLAPS 40 DEGS AND WE COMPLETED THE BEFORE LNDG CHKLIST. WE BOTH HAD THE RWY IN SIGHT; BUT CONTINUED THE APCH. I HAD REDUCED THE DSCNT TO 1000 FPM AND AS WE APCHED MDA WE RECEIVED ONE TERRAIN ALERT. I BEGAN THE CLB TO 1100 FT AND WE NEVER RECEIVED IT AGAIN. SIMULTANEOUSLY; THE TWR GAVE US A LOW TERRAIN ALERT AND A NEW ALTIMETER SETTING OF 29.52. WE ONLY RECEIVED ONE ALERT FROM THE GPWS; AND THE RWY WAS IN SIGHT THROUGHOUT THE ENTIRE EVENT. WE THEN CONTINUED THE APCH AND LANDED WITHOUT FURTHER INCIDENT. WE BOTH DEBRIEFED ONE ANOTHER WHEN WE GOT TO THE GATE. I BELIEVE THAT THE FIRST ERROR WAS MADE IN DOING A RUSHED BRIEFING FOR A NON-PRECISION APCH. IN DOING SO; WE BOTH MISSED THE 4.5 IRLI STEP-DOWN FIX OF 1400 FT. OUR ATTN HAD BEEN DRAWN TO THE BOTTOM OF THE APCH PLATE BELIEVING THAT 1400 FT WAS ONLY A FACTOR IF THE DME WAS INOP. I DID NOT SEE THE STEP-DOWN ON THE PLATE. THE FO EVEN MENTIONED IT WHEN SETTING THE MDA; AND WE HAD A QUICK DISCUSSION ABOUT IT. IT IS MY BELIEF THAT HE CAUGHT IT AT THE LAST MINUTE. WHEN WE RECEIVED THE TERRAIN ALERT; I HAD THE FIELD IN SIGHT. I BEGAN ADDING PWR; ALTHOUGH I DID NOT CALL 'EMER THRUST;' CLBED TO 1100 FT AND THEN WE NEVER RECEIVED THE ALERT AGAIN. WE BOTH FELT THE CLOSURE RATE MUST HAVE SET IT OFF.

Data retrieved from NASA's ASRS site as of January 2009 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.