AN ACR MLG ON APCH TO ORD RWY 14R EXPERIENCES AN ALT EXCURSION PRIOR TO REACHING THE NDB. THE CREW HAD 'BUILT' AN NDB APCH INTO THEIR FMC; BUT THE FIX WAS DEPICTED IN THE WRONG AREA. CREW STARTED DSCNT WITH A PREMATURE NEEDLE SWING. CFIT.

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AS THE FO AND PF; I BRIEFED THE NDB RWY 14R APCH AT ORD. BECAUSE AN NDB IS A RARE OCCURRENCE IN OUR OP; WE DECIDED TO 'BUILD' AN NDB APCH WITH THE FMC. DOING THIS WOULD GIVE US A BACKUP ON OUR POS AND A WAY TO ANTICIPATE THE XING OF THE FAF. THE ONLY PROB IS THAT THE CONSTRUCTED APCH DEPICTED 'OR' BEACON 5.2 MI N OF ITS ACTUAL POS. ORD APCH CTL WAS VERY BUSY AND AFTER SEVERAL RADAR VECTORS; LEFT US ON A 140 DEG HDG BUT DID NOT CLR US FOR THE APCH. WITH A STRONG W WIND WE WERE DRIFTING E OF FINAL. AFTER RECEIVING APCH CLRNC; IT WAS A SCRAMBLE TO REINTERCEPT AND GET THE ACFT IN THE LNDG CONFIGN PRIOR TO THE FAF. RAW DATA WAS BEING DISPLAYED ON BOTH THE RDMI AND THE NAV DISPLAY. I THOUGHT WE WERE VERY CLOSE TO THE BEACON AND WHEN I SAW A 10 DEG SWING ON THE ADF NEEDLE; I ASSUMED WE WERE AT 'OR.' WE DSNDED ABOUT 500 FT WHEN APCH CTL SAID THEY HAD A LOW ALT ALERT ON US. WE CLBED BACK TO 2400 FT AND THEN REALIZED WHAT HAD HAPPENED. FACTORS WERE: INFO OVERLOAD; INACCURATE INFO (FMC FIX); HIGH WORKLOAD PORTION OF FLT; NONROUTINE OP; FIRST CREW PAIRING (2ND LEG). SUPPLEMENTAL INFO FROM ACN 414118: IT WAS A HURRIED TURN BACK TO INTERCEPT THE COURSE; BECAUSE THE FMC SHOWED US ALMOST AT THE NDB. WE BOTH SAW THE NEEDLE START TO SWING AND THE FO CALLED FOR THE NEXT ALT. I SELECTED THE NEXT ALT; STARTED THE TIME; AND GOT READY TO CALL THE TWR. TWR FREQ WAS BUSY SO I DIDN'T GET A CALL IN RIGHT AWAY. AFTER DSNDING ABOUT 500 FT; THE TWR GAVE US AN ALT ALERT. WE HAD BEEN DSNDING IN VFR CONDITIONS AND HAD GND CONTACT FROM ABOUT 7000 FT. WE COULD SEE THAT THERE WERE NO OBSTACLES IN OUR VICINITY AND WE WERE STILL ABOUT 1200 FT ABOVE THE GND. THEN WE BOTH LOOKED AT THE ADF NEEDLE AND SAW THAT IT WAS STILL POINTING UP. THE FMC SHOWED THE NDB FURTHER OUT ON THE APCH THAN IT SHOULD HAVE BEEN. A DOUBLECHK MIGHT HAVE CAUGHT THE ERROR. POOR RADAR VECTORS. IT CAUSED US TO BE IN A SLIGHT RUSH TO COMPLETE ALL RECEIVED CONFIGNS AND CHKLISTS. THE NDB'S AND OTHER NON PRECISION APCHS WE FLY AT RECURRENT TRAINING REQUIRE A DSCNT STARTED ALMOST IMMEDIATELY AT STATION PASSAGE. OTHERWISE; THE ACFT WON'T BE AT MDA IN TIME FOR A NORMAL APCH TO THE RWY.