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MD88 flight crew fails to make a crossing restr even though they were monitoring their descent profile as set up by the FMS. Too late they realized that they were too high to make it. Controller then asked for an expedited descent.
| Attributes | |
| ACN | 378580 |
| Time | |
| Date | 199708 |
| Day | Fri |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : flm |
| State Reference | KY |
| Altitude | msl bound lower : 18000 msl bound upper : 19000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zid |
| Operator | common carrier : air carrier |
| Make Model Name | MD-88 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other Other |
| Flight Phase | descent other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 200 flight time total : 10200 flight time type : 630 |
| ASRS Report | 378580 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : commercial pilot : instrument |
| Events | |
| Anomaly | aircraft equipment problem : less severe altitude deviation : crossing restriction not met altitude deviation : undershoot non adherence : clearance |
| Independent Detector | other controllera other flight crewa |
| Resolutory Action | flight crew : became reoriented other other |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | Pilot Deviation other |
Narrative:
En route from atl to day, ATC clearance was to descend out of cruise (FL350) to FL330 with pilot's discretion to cross 20 NM south of flm VORTAC at FL180. The FMS computer was programmed and VNAV selected. Initially, FMS showed us well below glide path and first officer manually verified that we were. First officer continued through FL330 and we were well below glide path and manually derived glide path. Further into descent, the first officer and I got distraction with ATIS and in-range report to company. First officer kept eye on VNAV glide path which still indicated we were low for crossing restr. Once again, first officer manually checked descent progress and he/we realized we were actually way higher -- almost 6000 ft above FL180 with only 10.5 NM to get down! First officer did his best to smoothly get aircraft down but we actually crossed the fix about 1000 ft high. No traffic conflicts were noted (ATC did ask us to expedite our descent just after error was noted). Subsequent examination revealed the FMS had been programmed correctly, but had malfunctioned on glide path computations. Moral to story: pilots must never totally rely on automation.
Original NASA ASRS Text
Title: MD88 FLC FAILS TO MAKE A XING RESTR EVEN THOUGH THEY WERE MONITORING THEIR DSCNT PROFILE AS SET UP BY THE FMS. TOO LATE THEY REALIZED THAT THEY WERE TOO HIGH TO MAKE IT. CTLR THEN ASKED FOR AN EXPEDITED DSCNT.
Narrative: ENRTE FROM ATL TO DAY, ATC CLRNC WAS TO DSND OUT OF CRUISE (FL350) TO FL330 WITH PLT'S DISCRETION TO CROSS 20 NM S OF FLM VORTAC AT FL180. THE FMS COMPUTER WAS PROGRAMMED AND VNAV SELECTED. INITIALLY, FMS SHOWED US WELL BELOW GLIDE PATH AND FO MANUALLY VERIFIED THAT WE WERE. FO CONTINUED THROUGH FL330 AND WE WERE WELL BELOW GLIDE PATH AND MANUALLY DERIVED GLIDE PATH. FURTHER INTO DSCNT, THE FO AND I GOT DISTR WITH ATIS AND IN-RANGE RPT TO COMPANY. FO KEPT EYE ON VNAV GLIDE PATH WHICH STILL INDICATED WE WERE LOW FOR XING RESTR. ONCE AGAIN, FO MANUALLY CHKED DSCNT PROGRESS AND HE/WE REALIZED WE WERE ACTUALLY WAY HIGHER -- ALMOST 6000 FT ABOVE FL180 WITH ONLY 10.5 NM TO GET DOWN! FO DID HIS BEST TO SMOOTHLY GET ACFT DOWN BUT WE ACTUALLY CROSSED THE FIX ABOUT 1000 FT HIGH. NO TFC CONFLICTS WERE NOTED (ATC DID ASK US TO EXPEDITE OUR DSCNT JUST AFTER ERROR WAS NOTED). SUBSEQUENT EXAMINATION REVEALED THE FMS HAD BEEN PROGRAMMED CORRECTLY, BUT HAD MALFUNCTIONED ON GLIDE PATH COMPUTATIONS. MORAL TO STORY: PLTS MUST NEVER TOTALLY RELY ON AUTOMATION.
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.