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Air carrier medium large transport altitude deviation overshot during descent using 'advanced flight guidance system.'
| Attributes | |
| ACN | 122911 |
| Time | |
| Date | 198909 |
| Day | Fri |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : bna |
| State Reference | TN |
| Altitude | msl bound lower : 10500 msl bound upper : 11000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Dusk |
| Aircraft 1 | |
| Controlling Facilities | tracon : bna |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Navigation In Use | Other |
| Flight Phase | cruise other descent other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : flight engineer pilot : atp |
| Experience | flight time last 90 days : 200 flight time total : 6000 flight time type : 2000 |
| ASRS Report | 122911 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Events | |
| Anomaly | altitude deviation : overshoot non adherence : clearance |
| Independent Detector | other flight crewa |
| Resolutory Action | flight crew : returned to intended course or assigned course |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
Descending to cross 30 DME south of bna at and maintain 11000'. Aircraft on autoplt with altitude capture armed. I flew through altitude anyway. Aircraft bottomed out at 10500' after autoplt disengaged. This type medium large transport is notorious for altitude busts because it has an 'advanced flight guidance system,' incorporating automatic altitude capture. This system works just well enough to trap you. Older mlgs west/O this system were not noted for this problem. What's wrong here? A misguided desire to rely on poorly designed automation reduces safety margins.
Original NASA ASRS Text
Title: ACR MLG ALT DEVIATION OVERSHOT DURING DESCENT USING 'ADVANCED FLT GUIDANCE SYSTEM.'
Narrative: DSNDING TO CROSS 30 DME S OF BNA AT AND MAINTAIN 11000'. ACFT ON AUTOPLT WITH ALT CAPTURE ARMED. I FLEW THROUGH ALT ANYWAY. ACFT BOTTOMED OUT AT 10500' AFTER AUTOPLT DISENGAGED. THIS TYPE MLG IS NOTORIOUS FOR ALT BUSTS BECAUSE IT HAS AN 'ADVANCED FLT GUIDANCE SYS,' INCORPORATING AUTOMATIC ALT CAPTURE. THIS SYS WORKS JUST WELL ENOUGH TO TRAP YOU. OLDER MLGS W/O THIS SYS WERE NOT NOTED FOR THIS PROB. WHAT'S WRONG HERE? A MISGUIDED DESIRE TO RELY ON POORLY DESIGNED AUTOMATION REDUCES SAFETY MARGINS.
Data retrieved from NASA's ASRS site as of August 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.