Narrative:

As the first officer and PF, I briefed the NDB runway 14R approach at ord. Because an NDB is a rare occurrence in our operation, we decided to 'build' an NDB approach with the FMC. Doing this would give us a backup on our position and a way to anticipate the crossing of the FAF. The only problem is that the constructed approach depicted 'or' beacon 5.2 mi north of its actual position. Ord approach control was very busy and after several radar vectors, left us on a 140 degree heading but did not clear us for the approach. With a strong west wind we were drifting east of final. After receiving approach clearance, it was a scramble to reintercept and get the aircraft in the landing confign prior to the FAF. Raw data was being displayed on both the RDMI and the navigation display. I thought we were very close to the beacon and when I saw a 10 degree swing on the ADF needle, I assumed we were at 'or.' we descended about 500 ft when approach control said they had a low altitude alert on us. We climbed back to 2400 ft and then realized what had happened. Factors were: information overload, inaccurate information (FMC fix), high workload portion of flight, nonroutine operation, first crew pairing (2ND leg). Supplemental information 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 first officer called for the next altitude. I selected the next altitude, started the time, and got ready to call the tower. Tower frequency was busy so I didn't get a call in right away. After descending about 500 ft, the tower gave us an altitude alert. We had been descending in VFR conditions and had ground 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 ground. 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 approach 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 checklists. The NDB's and other non precision approachs we fly at recurrent training require a descent started almost immediately at station passage. Otherwise, the aircraft won't be at MDA in time for a normal approach to the runway.

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Original NASA ASRS Text

Title: 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.

Narrative: 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.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.