B737-300 CREW HAD TRACK AND ALTDEV ON A STAR INTO LAX.

Narrative

FLT XXX DEPARTED LAS ENRTE FOR LAX ARPT ON ATC FLT PLAN OF IDALE 1 DEP HECTOR TRANSITION AND THEN J64 TO LAX VOR. THE AIRPLANE; A B737-300; WAS EQUIPPED WITH FMC THAT HAD ONLY 1 FMC-CDU BOX LOCATED ON THE CAPT'S SIDE WITH NO EFIS SCREENS. AFTER BEING HANDED OFF TO SOCAL APCH CTL WITH AUTOPLT ENGAGED; WE WERE TOLD TO EXPECT MITTS 1 ARR TO RWY 24R AT LAX ARPT. AT THIS TIME; THE CAPT BEGAN TO INPUT THE MITTS 1 ARR INTO THE FMC CDU FOR RWY 24R. AT THE SAME TIME SOCAL APCH CTL THEN INSTRUCTED FLT XXX TO DSND VIA MITTS 1 ARR FOR RWY 24R. THE CAPT WAS STILL ENTERING THE ARR WHEN I TOLD HIM THAT HE WOULD NEED TO DSND RIGHT NOW IN ORDER TO MAKE THE FIRST ALT XING RESTR. SO HE BEGAN THE DSCNT IMMEDIATELY FOR THE FIRST STEP-DOWN FIX. MEANWHILE; BECAUSE OF A RTE DISCONTINUITY IN FMC CDU BOX THE NEXT FIX WAS NOT ACTIVE AND THE AIRPLANE DID NOT TURN AS REQUIRED; IN ORDER TO JOIN THE ARR PROC. I THEN NOTICED AIRPLANE WAS NOT TURNING BECAUSE OF DISCONTINUITY AND TOLD HIM WE NEED TO TURN TO JOIN ARR. HE SELECTED HDG SELECT ON MCP FOR AUTOPLT AND SELECTED A HDG TO JOIN ARR AND CLOSE RTE DISCONTINUITY. AT THIS TIME; APCH CTL INSTRUCTED US TO TURN ALSO BECAUSE THE PLANE WAS DEVIATING S OF THE DESIRED ARR COURSE. CAPT TURNED AIRPLANE TO 280 DEG HDG AS INSTRUCTED AND REJOINED ARR AND THEN DSNDED TO 10000 FT MSL AS INSTRUCTED BY SOCAL APCH. APCH CTL INSTRUCTED US TO TURN IN ORDER TO NOT HAVE CONFLICT WITH AN ACFT ON THE S ARR PROC. WE THEN ASKED SOCAL IF HE WANTED US TO CONTINUE DSCNT VIA MITTS 1 ARR RWY 24R. SOCAL INSTRUCTED US TO CONTINUE DSCNT VIA MITTS 1 ARR COMPLYING WITH REST OF ALT RESTRS. LANDED AND TAXIED TO THE GATE. ONCE ESTABLISHED ON THE ARR AGAIN; WE TOLD SOCAL APCH THAT WE DID NOT HAVE ENOUGH TIME TO CHANGE RTE IN FMC BOX AND CONTINUE THE DSCNT AS INSTRUCTED. SOCAL APCH SAID NO PROB. IN SUMMARY; SOCAL APCH CTL NEEDS TO ALLOW MORE TIME TO CHANGE THE ARR PROC IN FMC CDU AND MORE NOTICE ABOUT EXPECTING AN ARR ESPECIALLY WHEN GIVEN INSTRUCTIONS TO DSND VIA THE ARR SHORTLY AFTER SAYING TO EXPECT AN ARR BECAUSE IT TAKES TIME TO CHANGE THE ARR PROC. NEXT TIME; WE PROBABLY SHOULD QUERY ATC OF WHAT TO EXPECT IF NOT TOLD SOONER TO ALLOW MORE TIME FOR PLANNING PURPOSES. IF GIVEN LAST MIN INSTRUCTIONS BY ATC; PROBABLY SHOULD ASK FOR VECTOR TO HAVE TIME TO MAKE CHANGES TO ARR PROC.