B737-200 FLC EXPERIENCES AN ALTDEV ALT OVERSHOT IN DSCNT. RPTR ERROR ADMITTED.

Narrative

WHILE DSNDING THROUGH 8000 FT FOR 7000 FT MSL I WAS COPYING NEWLY UPDATED ATIS FROM OKC WHILE CAPT WAS FLYING. DURING THIS TIME FRAME; WAS ALSO CHANGING VOR FREQS IN PREPARATION FOR NEWLY ASSIGNED CLRNC FROM ATC. AT THAT ALT WE WERE PICKING UP MODERATE ICING. THE CAPT FLYING WAS WATCHING FOR ACCUMULATION OF ICING ON WINGS ABOUT THE TIME THE CTLR CHANGED FREQS. SINCE I WAS COPYING ATIS HE HAD THE RADIOS FOR ATC. ABOUT THE TIME HE WAS CHANGING FREQS; I LOOKED UP WHEN I HEARD THE ALT WARNING HORN GO OFF. WE WERE AT 6600 FT MSL INSTEAD OF THE REQUIRED 7000 FT. I POINTED THIS OUT TO THE CAPT AND HE IMMEDIATELY RETURNED TO 7000 FT. THE AUTOPLT WAS ENGAGED WITH CTL WHEEL STEERING MODE. PREVIOUS TO THIS FLT WE HAD BEEN FLYING B737-300'S WITH A DIFFERENT AUTOPLT AND FLT DIRECTOR SYS. I BELIEVE THAT WAS PART OF THE PROB FOR THE ALT MISS. THE OTHER PROB WAS TOO MUCH ACTIVITY IN THE COCKPIT BY BOTH PLTS AT THE SAME TIME. THE BEST SOLUTION TO THE PROB IS TO MAKE SURE BOTH PLTS ARE FAMILIAR WITH THE PARTICULAR INSTRUMENTATION OF THE ACFT THEY ARE FLYING AND TO MAKE SURE THAT 1 PLT IS MONITORING ACFT FLT PATH IF OTHER PLT IS BUSY WITH HEAD DOWN.