Narrative:

Aircraft was on a left base at 1600 ft. Was given a turn to final and intercept of localizer and cleared for approach. We were also given traffic at 11 O'clock, 5 mi on final that we were following. In the turn to final, both pilots were scanning for traffic, autoplt was engaged with altitude hold on, and the turn knob actuated manually for intercept turn. While turning turn knob, the captain accidentally moved the descent wheel to a 300 FPM descent rate. First indication of descent by both crew members was the altitude alert at 1300 ft MSL. Climb was initiated immediately but approach control (btr) called low altitude alert to us and advised us of the MSA for our position. Correct altitude was obtained within seconds of call from approach control.

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Original NASA ASRS Text

Title: AN ACR FLC FLYING DC9 ON APCH TO BTR FAILED TO MAINTAIN ASSIGNED ALT AS ASSIGNED BY ATC.

Narrative: ACFT WAS ON A L BASE AT 1600 FT. WAS GIVEN A TURN TO FINAL AND INTERCEPT OF LOC AND CLRED FOR APCH. WE WERE ALSO GIVEN TFC AT 11 O'CLOCK, 5 MI ON FINAL THAT WE WERE FOLLOWING. IN THE TURN TO FINAL, BOTH PLTS WERE SCANNING FOR TFC, AUTOPLT WAS ENGAGED WITH ALT HOLD ON, AND THE TURN KNOB ACTUATED MANUALLY FOR INTERCEPT TURN. WHILE TURNING TURN KNOB, THE CAPT ACCIDENTALLY MOVED THE DSCNT WHEEL TO A 300 FPM DSCNT RATE. FIRST INDICATION OF DSCNT BY BOTH CREW MEMBERS WAS THE ALT ALERT AT 1300 FT MSL. CLB WAS INITIATED IMMEDIATELY BUT APCH CTL (BTR) CALLED LOW ALT ALERT TO US AND ADVISED US OF THE MSA FOR OUR POS. CORRECT ALT WAS OBTAINED WITHIN SECONDS OF CALL FROM APCH CTL.

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.