A CPR JET PIC DSNDS BELOW THE ASSIGNED ALT REQUIRED FOR CULVE INTXN DURING AN INST APCH NEAR SMO; CA.

Narrative

THE ACFT WAS BEING VECTORED BY ATC TO INTERCEPT THE INBOUND COURSE OF THE VOR APCH TO SMO. AN INTERCEPT ANGLE OF APPROX 90 DEGS TO THE INBOUND COURSE WAS ISSUED; AS WELL AS A CLRNC TO COMMENCE THE VOR APCH (212 DEGS INBOUND). AT THIS TIME; THE CTLR ALSO ISSUED A CLRNC TO DSND FROM 7000 FT AND THE ACFT WAS BTWN DARTS (12.8 DME) AND BEVEY (6.7 DME). THE PF WAS INITIALLY USING THE AUTOPLT AND SELECTED THE 'APCH MODE' ONCE CLRED FOR THE APCH; TO EFFECT AN INBOUND COURSE INTERCEPT; INSTEAD OF THE 'NAV' FUNCTION ON THE FMS. WHEN THE INBOUND COURSE FAILED TO CAPTURE; THE PF DISCONNECTED THE AUTOPLT AND HAND-FLEW THE ACFT TO REINTERCEPT THE INBOUND COURSE. THE ACFT DSCNT WAS CONTINUED INSIDE BEVEY TOWARDS CULVE (2.4 DME AND 1120 FT MINIMUM ALT). AT THIS TIME; THE CDI WAS CTRED AND THE ACFT WAS IN VFR CONDITIONS AT APPROX 1600 FT. THE PF INADVERTENTLY DSNDED TO ABOUT 1050 FT BEFORE REACHING CULVE AND THE PNF CALLED OUT 'LOW ALT.' THE PF IMMEDIATELY COMMENCED A RECOVERY TO THE PROPER ALT OF 1120 FT; AT WHICH TIME ATC RADIOED 'LOW ALT ALERT; MINIMUM ALT TO CULVE IS 1120 FT; CHK YOUR EQUIP.' PNF RESPONDED 'ROGER' AS THE ACFT HAD ALREADY RECOVERED TO THE APPROPRIATE ALT OF 1120 FT. THE ATTN OF THE PF HAD BEEN DIVERTED FROM THE NORMAL SEQUENCES BY NOT HAVING PROPERLY ARMED THE 'NAV' FUNCTION OF THE FMS TO FACILITATE THE CAPTURE OF THE INBOUND COURSE. INATTN TO THE ALT RESTR; WHILE FOCUSING ON COURSE CORRECTION; CAUSED THE SLIGHT ALTDEV. ADDITIONALLY; THE DSCNT INTO VFR CONDITIONS MAY HAVE CONTRIBUTED TO THE RELAXATION OF ALT SCAN.