Narrative:

Night VFR to sna airport en route from see airport. Was working approach control as sic. Socal approach cleared us from 8000 ft to 5000 ft then to 4000 ft. Aircraft was on downwind, #2 for approach to runway 19R at sna. Pre-landing checklist and watching for aircraft on final distraction both pilots from altitude alertness. We descended through 4000 ft by at least 5000 ft. Approach reminded us of assigned altitude of 4000 ft then cleared to 3000 ft and the visual approach for runway 19R. We complied and performed rest of pattern without incident. At no time were we close to another aircraft.

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Original NASA ASRS Text

Title: A SABRELINER 65 FO RPTED THAT HE BECAME DISTR DURING THE APCH TO SNA AND DID NOT BACK HIS CAPT (PF) UP ON THE ALT CAPTURE.

Narrative: NIGHT VFR TO SNA ARPT ENRTE FROM SEE ARPT. WAS WORKING APCH CTL AS SIC. SOCAL APCH CLRED US FROM 8000 FT TO 5000 FT THEN TO 4000 FT. ACFT WAS ON DOWNWIND, #2 FOR APCH TO RWY 19R AT SNA. PRE-LNDG CHKLIST AND WATCHING FOR ACFT ON FINAL DISTR BOTH PLTS FROM ALT ALERTNESS. WE DSNDED THROUGH 4000 FT BY AT LEAST 5000 FT. APCH REMINDED US OF ASSIGNED ALT OF 4000 FT THEN CLRED TO 3000 FT AND THE VISUAL APCH FOR RWY 19R. WE COMPLIED AND PERFORMED REST OF PATTERN WITHOUT INCIDENT. AT NO TIME WERE WE CLOSE TO ANOTHER ACFT.

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.