Narrative:

The autoplt was engaged (controled by the first officer) and used for the approach as per company SOP. We crossed reebo at 2000 ft with gear down and flaps 30 degrees, speed 160 KTS as requested by approach. MDA is 660 ft so 700 ft was selected in autoplt altitude window. The vertical speed mode was used after reebo with 1200 FPM down selected. Reaching 700 ft MSL the tower called 'low altitude alert, check your altitude.' I responded that we were at MDA, 700 ft. We maintained 700 ft to the vdp and then continued the descent to a landing. Talking to ground control later, we were told that their computer generated a low altitude warning because of our gradient and distance from the airport. We were not below MDA when tower called with their low altitude warning. Either the tower computer parameters need to be changed or a step down altitude needs to be added to the localizer 27 profile inside of reebo.

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Original NASA ASRS Text

Title: AN ACR WDB RECEIVED AN UNWARRANTED LOW ALT WARNING FROM THE TWR WHILE ON A LOC APCH.

Narrative: THE AUTOPLT WAS ENGAGED (CTLED BY THE FO) AND USED FOR THE APCH AS PER COMPANY SOP. WE CROSSED REEBO AT 2000 FT WITH GEAR DOWN AND FLAPS 30 DEGS, SPD 160 KTS AS REQUESTED BY APCH. MDA IS 660 FT SO 700 FT WAS SELECTED IN AUTOPLT ALT WINDOW. THE VERT SPD MODE WAS USED AFTER REEBO WITH 1200 FPM DOWN SELECTED. REACHING 700 FT MSL THE TWR CALLED 'LOW ALT ALERT, CHK YOUR ALT.' I RESPONDED THAT WE WERE AT MDA, 700 FT. WE MAINTAINED 700 FT TO THE VDP AND THEN CONTINUED THE DSCNT TO A LNDG. TALKING TO GND CTL LATER, WE WERE TOLD THAT THEIR COMPUTER GENERATED A LOW ALT WARNING BECAUSE OF OUR GRADIENT AND DISTANCE FROM THE ARPT. WE WERE NOT BELOW MDA WHEN TWR CALLED WITH THEIR LOW ALT WARNING. EITHER THE TWR COMPUTER PARAMETERS NEED TO BE CHANGED OR A STEP DOWN ALT NEEDS TO BE ADDED TO THE LOC 27 PROFILE INSIDE OF REEBO.

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.