B757 CREW MISSES CROSSING RESTRICTION ON CIVET5 INTO LAX AFTER RWY CHANGE.

Narrative

I WAS ON THE JUMPSEAT OF THE FLT AS A LINE CHK AIRMAN; PERFORMING A LINE CHK. SOCAL TRACON CLRED THE CREW TO DSND VIA THE CIVET ARR; BUT GAVE NO RWY. THE ARR CONTAINS RWY SPECIFIC ROUTING AND ALT RESTRICTIONS. I HAD BRIEFED THE CREW THAT A GOOD TECHNIQUE TO BE PREPARED FOR A RWY CHANGE ON THIS ARR WAS TO PROGRAM RT2 IN THE FMS FOR THE OTHER LIKELY RWY. THEY OPTED NOT TO DO SO. 1.2 MILES FROM GRAMM INTXN; ATC ASSIGNED RWY 24R; AND GAVE A SPD RESTRICTION OF 250 KIAS. THE CAPT; WHO WAS THE PF; DIRECTED THE FO; WHO WAS THE PNF; TO REPROGRAM THE FMS FOR RWY 24R. AS THE PNF WAS REPROGRAMMING; THE NEXT FIX AFTER GRAMM; RUSTT; DISAPPEARED FROM THE HSI MAP AND FROM THE FMS LEGS PAGE AS THE PNF WAS SELECTING ARR; RWY AND TRANSITION; THEN CLEANING UP THE ROUTING AS WE HAD ALREADY PASSED GRAMM BY THIS TIME. THERE WAS AN ALT RESTRICTION AT RUSTT OF CROSS AT OR ABOVE 15000 FT MSL. THE PF USED THE AUTOPLT HDG SELECT MODE TO STEER THE ACFT TOWARDS CIVET; THE NEXT FIX AFTER RUSTT. APPROX 1-2 MILES PRIOR TO RUSTT WE REALIZED THAT WE HAD MISSED THE ALT RESTRICTION AT RUSTT AND THE ACFT HAD DSNDED TO APPROX 14200 FT MSL. AT THIS POINT; THE CAPT ELECTED TO REMAIN AT THAT ALT RATHER THAN TRY TO CLB BACK TO 15000 FT MSL IN 1 MILE; THEN RAPIDLY REVERSE THE CLB TO DSND TO THE NEXT RESTRICTION SO AS TO AVOID THE RISK OF INJURING SOMEONE IN THE CABIN WITH THE PITCH CHANGES AND POSSIBLE G CHANGES REQUIRED. TCAS SHOWED NO TFC CONFLICT; AND ATC GAVE NO INDICATION OF TFC CONFLICT. THE CREW THEN REACQUIRED THE CIVET ARR DSCNT PROFILE; AND ACCOMPLISHED A SAFE LNDG AT LAX. TO MY MIND THERE ARE A COUPLE OF PERTINENT ISSUES TO BE ADDRESSED HERE. FIRST; THE CREW SHOULD HAVE BEEN PREPARED FOR THE POSSIBILITY OF A CLRNC TO A RWY OTHER THAN WHAT THEY HAD PROGRAMMED IN THE FMS. FAILING THAT; THEY SHOULD HAVE ADVISED ATC THEY WERE UNABLE TO COMPLY WITH THE 'CLRED TO DSND VIA THE CIVET ARR' CLRNC. SECOND; ATC SHOULD BE MADE AWARE OF THE EFFECT OF A LATE RWY ASSIGNMENT ON CREWS AS THEY REPROGRAM THE FMS. IT GREATLY REDUCES SITUATIONAL AWARENESS. ON ARRS THAT HAVE RWY DEPENDENT ROUTING AND ALT RESTRICTIONS; ATC SHOULD BE REQUIRED TO ASSIGN A RWY NO LATER THAN ABOUT 2 MINUTES PRIOR TO THE COMMENCEMENT OF THAT PROC.