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Widebody transport aircraft in descent, annunciators indicated normal operations for altitude capture, but descent rate increased and before reporter captain could catch it, the aircraft descended 500 ft below assigned.
| Attributes | |
| ACN | 373610 |
| Time | |
| Date | 199707 |
| Day | Sat |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : cap |
| State Reference | IL |
| Altitude | msl bound lower : 23500 msl bound upper : 24000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zkc tower : hya |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other Other |
| Flight Phase | cruise other descent other |
| Route In Use | arrival other arrival star : star |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp pilot : flight engineer |
| Experience | flight time last 90 days : 180 flight time total : 22154 flight time type : 4200 |
| ASRS Report | 373610 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : commercial |
| Events | |
| Anomaly | aircraft equipment problem : less severe altitude deviation : crossing restriction not met 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:
Flight inbound to cvg. We were inbound to cap VOR at FL330 when ATC issued a southeast heading for traffic. We were then cleared to a northeast heading to intercept the 087 degree radial, cap VOR, cleared for the mican 3 arrival, to cross lewey intersection at FL240. I programmed the descent on the FMS and initiated the descent. The descent appeared normal. As the aircraft approached the assigned altitude of FL240, all annunciations indicated a normal altitude capture. During the final several hundred ft, the rate of descent increased to 3000-3500 FPM with still a normal altitude capture annunciated. As we passed FL240 it then became obvious the aircraft was not going to level off. I disconnected the autoplt approximately 100 ft below FL240 and began to initiate a recovery. With the excessive nose down trim and rate of descent, it took 500 ft to reverse the descent. We returned to FL240.
Original NASA ASRS Text
Title: WDB ACFT IN DSCNT, ANNUNCIATORS INDICATED NORMAL OPS FOR ALT CAPTURE, BUT DSCNT RATE INCREASED AND BEFORE RPTR CAPT COULD CATCH IT, THE ACFT DSNDED 500 FT BELOW ASSIGNED.
Narrative: FLT INBOUND TO CVG. WE WERE INBOUND TO CAP VOR AT FL330 WHEN ATC ISSUED A SE HDG FOR TFC. WE WERE THEN CLRED TO A NE HDG TO INTERCEPT THE 087 DEG RADIAL, CAP VOR, CLRED FOR THE MICAN 3 ARR, TO CROSS LEWEY INTXN AT FL240. I PROGRAMMED THE DSCNT ON THE FMS AND INITIATED THE DSCNT. THE DSCNT APPEARED NORMAL. AS THE ACFT APCHED THE ASSIGNED ALT OF FL240, ALL ANNUNCIATIONS INDICATED A NORMAL ALT CAPTURE. DURING THE FINAL SEVERAL HUNDRED FT, THE RATE OF DSCNT INCREASED TO 3000-3500 FPM WITH STILL A NORMAL ALT CAPTURE ANNUNCIATED. AS WE PASSED FL240 IT THEN BECAME OBVIOUS THE ACFT WAS NOT GOING TO LEVEL OFF. I DISCONNECTED THE AUTOPLT APPROX 100 FT BELOW FL240 AND BEGAN TO INITIATE A RECOVERY. WITH THE EXCESSIVE NOSE DOWN TRIM AND RATE OF DSCNT, IT TOOK 500 FT TO REVERSE THE DSCNT. WE RETURNED TO FL240.
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.