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Flight crew of a B737-400 undershot crossing altitude during descent due to the FMC not holding the correct DME distance, or the flight crew not assuring that the FMC was properly programmed prior to activating the execute button.
| Attributes | |
| ACN | 430675 |
| Time | |
| Date | 199903 |
| Day | Tue |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | navaid : das.vortac |
| State Reference | TX |
| Altitude | msl bound lower : 10000 msl bound upper : 10800 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zhu.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B737-400 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other other vortac |
| Flight Phase | descent : intermediate altitude |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp pilot : cfi pilot : multi engine pilot : flight engineer |
| Experience | flight time last 90 days : 120 flight time total : 11000 flight time type : 7000 |
| ASRS Report | 430675 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : multi engine pilot : flight engineer pilot : commercial pilot : atp |
| Experience | flight time total : 15000 |
| ASRS Report | 430680 |
| Events | |
| Anomaly | altitude deviation : undershoot altitude deviation : crossing restriction not met non adherence : clearance |
| Independent Detector | other flight crewa |
| Resolutory Action | other |
| Supplementary | |
| Problem Areas | Flight Crew Human Performance |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
We were given a clearance to cross 10 mi northeast of das VOR at 10000 ft then slow to 250 KTS at das. The captain entered the clearance in the FMC. It appeared correct. About 7-8 mi out, I realized on raw data (VOR DME) that we had missed the 10 mi point. Upon checking the FMC, it was showing 1 mi instead of 10 mi. The captain took over manually. We were probably about 800 ft high. There was no conflict. Either we missed the 10 mi being entered incorrectly or the FMC dropped the zero before the execute button was pressed.
Original NASA ASRS Text
Title: FLC OF A B737-400 UNDERSHOT XING ALT DURING DSCNT DUE TO THE FMC NOT HOLDING THE CORRECT DME DISTANCE, OR THE FLC NOT ASSURING THAT THE FMC WAS PROPERLY PROGRAMMED PRIOR TO ACTIVATING THE EXECUTE BUTTON.
Narrative: WE WERE GIVEN A CLRNC TO CROSS 10 MI NE OF DAS VOR AT 10000 FT THEN SLOW TO 250 KTS AT DAS. THE CAPT ENTERED THE CLRNC IN THE FMC. IT APPEARED CORRECT. ABOUT 7-8 MI OUT, I REALIZED ON RAW DATA (VOR DME) THAT WE HAD MISSED THE 10 MI POINT. UPON CHKING THE FMC, IT WAS SHOWING 1 MI INSTEAD OF 10 MI. THE CAPT TOOK OVER MANUALLY. WE WERE PROBABLY ABOUT 800 FT HIGH. THERE WAS NO CONFLICT. EITHER WE MISSED THE 10 MI BEING ENTERED INCORRECTLY OR THE FMC DROPPED THE ZERO BEFORE THE EXECUTE BUTTON WAS PRESSED.
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.