Narrative:

We were cleared to descend via the arrival except maintain 12;000 ft. We were cruising at 24;000 ft northeast of momar. We began to experience turbulence that resembled wake. At that point in time I was under the impression we were cleared to 12;000 ft. I selected altitude intervention to begin a descent out of the turbulence. I selected altitude intervention a second time to begin the descent. The crossing attitudes were erased at momar due to selecting altitude intervene. During both presses of the altitude intervene the captain and I vvmi'd. We descended below the published altitude at momar.

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Original NASA ASRS Text

Title: B737 Flight Crew reported overshooting an altitude restriction in descent due to a programming error.

Narrative: We were cleared to descend via the arrival except maintain 12;000 ft. We were cruising at 24;000 ft northeast of MOMAR. We began to experience turbulence that resembled wake. At that point in time I was under the impression we were cleared to 12;000 ft. I selected Altitude Intervention to begin a descent out of the turbulence. I selected Altitude Intervention a second time to begin the descent. The crossing attitudes were erased at MOMAR due to selecting ALT Intervene. During both presses of the ALT Intervene the Captain and I VVMI'd. We descended below the published altitude at MOMAR.

Data retrieved from NASA's ASRS site 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.