ALTDEV ALT UNDERSHOT IN DSCNT. ALT XING RESTR NOT MET.

Narrative

AIRLINES FLT OPERATING FROM EWR TO PHX. ACFT B-757-200. WHILE CRUISING AT FL330 ON A CLRNC DIRECT TO SACHO INTXN ON THE FOSSL 2 ARR TO PHX; ZAB ISSUED A CLRNC DIRECT TO THE PIINE INTXN CROSS TONTO INTXN AT 12000 FT/250 KTS. THE FMS WAS IN VNAV PATH WITH 12000 FT SELECTED. THE FO JUST GOT THE ATIS WHICH INDICATED RWY 26 IN USE. THE FMS WAS PROGRAMMED FOR RWY 08 ARR. JUST AS THE FO WAS ABOUT TO CALL THE COMPANY FOR GATE INFO THE #1 FLT ATTENDANT CAME FORWARD WITH A REQUEST FROM A FEMALE PAX WITH A SMALL CHILD WHO'S BAG HAD BEEN IMPROPERLY CHKED. I; THE PF; STARTED REPROGRAMMING THE FMS FOR A RWY 26 ARR AND THE NEW XING RESTR. THE RWY 08 ARR HAD A 280 KT SPD RESTR. AFTER I HAD COMPLETED THIS I NOTICED THAT THE FMS WAS NOT IN VNAV PATH NOW AND WE HAD OVERFLOWN THE DSCNT POINT ON THE EFIS. I MADE EVERY EFFORT TO MAKE THE XING RESTR BUT WAS ABOUT 6000 FT TOO HIGH. ZAB ASKED IF WE COULD MAKE THE XING RESTR WHICH WE REPLIED WE COULD NOT. THEY THEN ASKED US TO MAKE A 360 DEG TURN AND WHY DID WE MISS THE XING RESTR. WE REPLIED 'A COMPUTER PROB.' THIS EVENT OCCURRED BECAUSE THE 2 MAN COCKPIT OF THE NEW HIGH TECHNOLOGY AIRLINERS DOES NOT HAVE THE BACKUP NECESSARY WHEN CONFRONTED WITH HIGH WORKLOAD SITS REQUIRED BY TODAY'S AIRLINE OP PROCS. SINCE THE FO WAS HANDLING OTHER NON ACFT OP PROBS; I WAS LEFT WITH REPROGRAMMING THE NEW ARR AND FLYING THE ACFT TOTALLY MYSELF; WHICH MEANS I AM FLYING A 182 PAX ACFT SOLO. NOT HAVING THE FO BACKUP MAKES FOR AN UNSAFE OP. I KNOW THAT EFIS; FMS; VNAV; AND LNAV ARE HERE TO STAY; BUT I FEEL THAT THE INCREASED WORKLOAD THEY REQUIRE SHOULD BE CONSIDERED WITH 2 MAN COCKPIT OP. I FLEW THE DC-9 FOR 14 YEARS SO I KNOW WHAT A 2 MAN COCKPIT WORKLOAD CAN BE. SUPPLEMENTAL INFO FROM ACN 297961: PHX ARRS FROM THE NE SEEM TO REQUIRE YOU TO BE CLOSER THAN NORMAL BEFORE GETTING THE ATIS; PROBABLY DUE TO SHIELDING OF THE SIGNALS BY MOUNTAINS. THEREFORE; SOME IN-RANGE ACTIVITIES ARE STARTED LATER THAN NORMAL. WHEN THE ATIS STARTED COMING IN; I WENT OFF FREQ TOGET THE WX AND GATE INFO. I SPENT EXTRA TIME AND EFFORT ON BEHALF OF THIS PAX TO TRY TO GET HER BAGGAGE PROB SOLVED WITHOUT HER HAVING TO RECLAIM HER BAGS THEN RE-CHK THEM. AT SOME POINT WHILE I WAS WORKING ON IN-RANGE ACTIVITIES INSTEAD OF BACKING UP THE PF; APPARENTLY THE FMS VERT NAV (VNAV) MODE HAD DISENGAGED. THIS OCCURS SOMETIMES FOR NO APPARENT REASON. DURING THAT TIME; THE ACFT FLEW PAST THE TOP OF DSCNT POINT WITH NEITHER PLT NOTICING IT. MY HABIT PATTERN IS THAT WHEN I RETURN TO 'THE LOOP' AFTER ACTIVITIES SUCH AS IN-RANGE; I WILL IMMEDIATELY TRY TO BRING MYSELF UP TO DATE ON EXACTLY WHAT MODE THE ACFT IS IN; THE CURRENT ATC CLRNC; THE STATUS OF THE FMS PROGRAMMING; AND ANY ERRORS THAT MAY BE OCCURRING. IN THIS INSTANCE HOWEVER; THE PF WAS REBUILDING THE CLOSE IN PORTIONS OF THE ARR DUE TO THE ATIS RPTING LNDG ON A DIFFERENT RWY THAN WE HAD ANTICIPATED AND CONNECTING IT WITH THE FINAL APCH. I BROKE MY HABIT OF CHKING WHERE WE WERE AND WHERE WE SHOULD BE TO WATCH HIM COMPLETE THE PROGRAMMING RATHER THAN REESTABLISH MY SITUATIONAL AWARENESS ON THE LATERAL AND VERT CLRNCS. MY PERCEPTION WAS THAT WE WERE STILL IN THE CRUISE MODE WHICH IS THE PLACE TO DO THIS TYPE OF PROGRAMMING. I REPLIED WE HAD A COMPUTER PROBLEM BECAUSE AT THE MOMENT I WAS STILL TRYING TO FIGURE OUT WHAT HAD HAPPENED. CONTRIBUTING FACTOR: PILOT FATIGUE. ALTHOUGH WE WERE ONLY ABOUT 4 1/2 HRS INTO OUR FIRST FLYING LEG; WE WERE ABOUT 11 HRS INTO THE DUTY DAY AS THE PAIRING REQUIRED A DEADHEAD LEG AND THEN ACFT CHANGE PRIOR TO ACTUALLY FLYING. DEADHDG IN THE BACK OF AN AIRPLANE IS JUST AS TIRING; IF NOT MORE SO; THAN FLYING IN THE COCKPIT. CONSIDERING TIME TO GET UP ; PACK; DRIVE TO THE ARPT; CHK COMPANY MAILBOX; ETC; I HAD BEEN UP APPROX 16 HRS AT THIS TIME. CONTRIBUTING FACTOR: 2 PERSON COCKPIT. IT MAY NOT NECESSARILY REQUIRE 3 PEOPLE TO FLY MODERN JET ACFT; BUT AT TIMES IT CAN REQUIRE 3 PEOPLE TO OPERATE THESE ACFT. THIS INCIDENT WOULD HAVE BEEN AVOIDED IF A THIRD CREWMEMBER IN THE COCKPIT WERE DOING THE ADMINISTRATIVE ITEMS WHILE 2 PLTS DEVOTING ALL THEIR TIME TO FLYING.