Narrative:

Established on a right downwind for runway 18R at cvg, ATC cleared us to descend to 7000 ft. During our descent, ATC cleared another company flight to expedite from 7000 ft to 4000 ft. We were passing 10000 ft when the captain extended our speed brake to increase our descent. At 8000 ft, the captain noticed traffic at our 12 O'clock position and lower. The traffic did not appear on TCASII. I then heard the first officer call out '7000 ft, 7000 ft.' I looked at the captain's altimeter and observed us descending below 7000 ft as the captain arrested our descent, added power, and retracted the speed brake. Lowest indicated altitude was 6650 ft. No inquiry was made from ATC and we quickly returned to 7000 ft. I believe that the traffic that was ahead of our flight path provided enough distraction at a critical time and caused a scan breakdown to occur. Supplemental information from acn 475021: ATC was talking with company flight and asked him to expedite his descent through 7000 ft to 4000 ft. We checked on frequency, but got no reply. I don't know why, but I was now expediting my descent through 7000 ft for 4000 ft. I extended the speed brakes and was descending through 8000 ft at 2500 FPM.

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Original NASA ASRS Text

Title: A DSNDING B727 OVERSHOOTS ITS ASSIGNED ALT WHEN THE CAPT BECOMES DISTR AND MENTALLY ACCEPTS ANOTHER ACFT'S CLRNC TO A LOWER ALT W OF CVG, OH.

Narrative: ESTABLISHED ON A R DOWNWIND FOR RWY 18R AT CVG, ATC CLRED US TO DSND TO 7000 FT. DURING OUR DSCNT, ATC CLRED ANOTHER COMPANY FLT TO EXPEDITE FROM 7000 FT TO 4000 FT. WE WERE PASSING 10000 FT WHEN THE CAPT EXTENDED OUR SPD BRAKE TO INCREASE OUR DSCNT. AT 8000 FT, THE CAPT NOTICED TFC AT OUR 12 O'CLOCK POS AND LOWER. THE TFC DID NOT APPEAR ON TCASII. I THEN HEARD THE FO CALL OUT '7000 FT, 7000 FT.' I LOOKED AT THE CAPT'S ALTIMETER AND OBSERVED US DSNDING BELOW 7000 FT AS THE CAPT ARRESTED OUR DSCNT, ADDED PWR, AND RETRACTED THE SPD BRAKE. LOWEST INDICATED ALT WAS 6650 FT. NO INQUIRY WAS MADE FROM ATC AND WE QUICKLY RETURNED TO 7000 FT. I BELIEVE THAT THE TFC THAT WAS AHEAD OF OUR FLT PATH PROVIDED ENOUGH DISTR AT A CRITICAL TIME AND CAUSED A SCAN BREAKDOWN TO OCCUR. SUPPLEMENTAL INFO FROM ACN 475021: ATC WAS TALKING WITH COMPANY FLT AND ASKED HIM TO EXPEDITE HIS DSCNT THROUGH 7000 FT TO 4000 FT. WE CHKED ON FREQ, BUT GOT NO REPLY. I DON'T KNOW WHY, BUT I WAS NOW EXPEDITING MY DSCNT THROUGH 7000 FT FOR 4000 FT. I EXTENDED THE SPD BRAKES AND WAS DSNDING THROUGH 8000 FT AT 2500 FPM.

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.