B737-300 CREW MISSED A XING RESTR ON THE KEPEC 1 RNAV ARR TO LAS. ACFT IS ONLY EQUIPPED WITH A SINGLE FMS; AND HAS NO NAV DISPLAY.

Narrative

I WAS THE PF B737-300 AT FL270 ON THE KEPEC1 RNAV ARR INTO LAS. ZLA CLRED US TO CROSS THE MISEN RNAV FIX AT FL240. THE PLT MONITORING SET FL240 INTO THE ALT WINDOW AND I SET FL240 OPPOSITE THE MISEN FIX IN THE FMC. I SELECTED DSCNT ON THE FMC TO DETERMINE TOP OF DSCNT. THE FMC DATA INDICATED A TOP OF DSCNT OF APPROX 30 NM AHEAD. THE PLT MONITORING THEN SELECTED THE MENU PAGE TO OBTAIN THE CURRENT ATIS FOR LAS. SEVERAL MINS PASSED IN OBTAINING THIS INFO; HOWEVER THE PLT MONITORING STATED THAT THE INFO WAS 1 HR OLD AND WOULD CHANGE IN SEVERAL MINS. THE FMC CRUISE PAGE WAS SELECTED AND THEN THE PLT MONITORING LEFT CTR FREQ TO OBTAIN STATION GATE INFO. AFTER A MIN OR SO THE PLT MONITORING RETURNED TO CTR FREQ AND SELECTED MENU AGAIN ON THE FMC TO OBTAIN THE NEW/CURRENT ATIS. SEVERAL MINS PASSED IN OBTAINING THIS NEW DATA. ATC CTLR GAVE US A DIFFERENT ATC FREQ AND ASKED US WHAT ALT WE WERE AT. I SELECTED THE DSCNT PAGE AGAIN AND NOTED 2600 FT HIGH; 12 MI PAST TOP OF DSCNT; WHICH PUT US JUST SEVERAL MI FROM OUR XING RESTR AT MISEN. A DSCNT WAS INITIATED IMMEDIATELY TO FL240 AND THE PLT MONITORING CHKED IN WITH THE NEW ATC CTLR AT FL240. NO TFC CONFLICTS WERE NOTED ON THE TCASII. ON RNAV ARRS IN THE B-300 SERIES ACFT SITUATIONAL AWARENESS IS COMPROMISED DUE TO SEVERAL FACTORS. BOTH PLT MONITORING AND PF ARE IN NAV MODE AND SO ALL SIT DATA IS PROVIDED VIA THE FMC. IN THIS CASE THERE WAS ONLY ONE FMC DISPLAY/HEAD; SO WHILE THE FMC IS BEING UTILIZED FOR OTHER TASKS SITUATIONAL AWARENESS CAN; AND IN THIS CASE WAS; COMPROMISED. IN THIS ACFT ON RNAV ARRS I FEEL THAT OBTAINING ATIS VIA THE #2 COM WOULD BE A WORTHWHILE OP POLICY OR THE INSTALLATION OF DUAL FMC'S. WE BOTH KNEW THAT A DSCNT WAS REQUIRED VERY SOON; HOWEVER WITH THE OPC; STATION CALL; ATIS; AND LNDG BRIEFING; AND OTHER DISTRS; IT IS EASY TO LOSE SITUATIONAL AWARENESS. WE MISSED THE BIGGER PICTURE BECAUSE WE WERE TRYING TO COMPLY WITH ALL OF THE DETAILS.