ALTDEV ALT EXCURSION. ACFT EQUIP PROB IN A NIGHT OP. INFLT ENG SHUTDOWN.

Narrative

ALL PHASES OF FLT LEADING UP TO INCIDENT WERE NORMAL. ACFT WAS CLRED TO 'FLY HDG 220 DEGS; MAINTAIN 2000 FT; AND CLRED FOR ILS RWY 25L.' AT APPROX 2500 FT; I HAD JUST DISCONNECTED THE AUTOPLT TO HAND FLY THE APCH (DISCONNECT ALERT WAS STILL SOUNDING). SIMULTANEOUSLY WE HEARD A LOUD BANG; AND THE ACFT SHUDDERED. OUR INITIAL BELIEF WAS THAT WE HAD STRUCK SOMETHING. IT WAS AT THAT TIME THE MASTER CAUTION LIGHT ILLUMINATED AND WE RECEIVED AN ENG 1; 'N1' LO ALERT. I SCANNED THE OTHER ENG PARAMETERS AND THEY INDICATED THAT THE ENG HAD SEIZED. THE INITIAL SHOCK AND DISBELIEF THAT WE HAD A POSSIBLE MIDAIR AND A DEFINITE SEIZED ENG CAUSED A MOMENTARY BREAKDOWN IN COCKPIT RESOURCE MGMNT; BOTH PLTS WERE MAKING INPUTS TO THE FLT GUIDANCE PANEL. THE ALT ALERT WAS MISTAKENLY RESET TO 1400 FT. I FAILED TO NOTICE THIS; AND WAS FOLLOWING THE FLT DIRECTOR; WHILE DIVERTING SOME ATTN TO THE ENG SEIZURE CHKLIST. NEITHER PLT NOTICED THAT WE HAD GONE THROUGH 2000 FT UNTIL ADVISED BY LAX TWR. THE DSCNT WAS ARRESTED AT 1600 FT. I CLBED BACK TO 2000 FT; AND THE REMAINDER OF THE APCH AND LNDG WAS NORMAL. UNFORTUNATELY; THIS INCIDENT WOULD NOT HAVE HAPPENED IF COCKPIT RESOURCE MGMNT HAD BEEN MAINTAINED. WE ALL NEED TO BE ABLE TO ALLOW THE NON-FLYING CREWMEMBERS TO COMPLETE THE APPROPRIATE PROCS; WHILE WE FLY THE ACFT.