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A descending DC9 flight crew overshoots their assigned altitude when the autoplt trim wheel is out of the leveloff detent over tlh, fl.
| Attributes | |
| ACN | 475530 |
| Time | |
| Date | 200006 |
| Day | Mon |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : tlh.airport |
| State Reference | FL |
| Altitude | msl bound lower : 23700 msl bound upper : 24000 |
| Environment | |
| Flight Conditions | Mixed |
| Weather Elements | Thunderstorm |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zjx.artcc tower : poc.tower |
| Operator | common carrier : air carrier |
| Make Model Name | DC-9 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other vortac |
| Flight Phase | descent : intermediate altitude |
| Route In Use | arrival : on vectors |
| 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 : 12000 flight time type : 1000 |
| ASRS Report | 475530 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 210 flight time total : 5800 flight time type : 1500 |
| ASRS Report | 475516 |
| Events | |
| Anomaly | altitude deviation : overshoot inflight encounter : weather non adherence : clearance other anomaly other |
| Independent Detector | other controllera |
| Resolutory Action | controller : issued advisory flight crew : returned to assigned altitude |
| Consequence | Other |
| Supplementary | |
| Problem Areas | ATC Human Performance Aircraft Flight Crew Human Performance Weather |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
On taylor one arrival requested vectors for thunderstorm avoidance. Aircraft was in a descent from FL310 to FL240 while trying to find a clear area to penetrate WX on the arrival and talking to ATC to find an acceptable course through the WX. Aircraft was on autoplt with descent wheel in detent (altitude hold upon arriving at FL240) descent wheel did not fully engage in altitude hold and aircraft descended to approximately FL237. Autoplt disconnect by PF (captain) and leveled back to FL240 after called by ATC. Contributing factors were high workload in thunderstorm activity while trying to deviate to acceptable course for ATC arrival requirement and aircraft safety to avoid WX. Visual and WX radar confirmation of thunderstorms not visible by ATC radar also contributed to high workload due to communication or WX to ATC by crew. Corrective action: 1) reduce workload on both flight crew and ATC by improved WX radar capability in aircraft, 2) more reliable autoplt altitude hold capability at ATC, and 3) increased awareness by flight crew of altitude during high workload.
Original NASA ASRS Text
Title: A DSNDING DC9 FLC OVERSHOOTS THEIR ASSIGNED ALT WHEN THE AUTOPLT TRIM WHEEL IS OUT OF THE LEVELOFF DETENT OVER TLH, FL.
Narrative: ON TAYLOR ONE ARR REQUESTED VECTORS FOR TSTM AVOIDANCE. ACFT WAS IN A DSCNT FROM FL310 TO FL240 WHILE TRYING TO FIND A CLR AREA TO PENETRATE WX ON THE ARR AND TALKING TO ATC TO FIND AN ACCEPTABLE COURSE THROUGH THE WX. ACFT WAS ON AUTOPLT WITH DSCNT WHEEL IN DETENT (ALT HOLD UPON ARRIVING AT FL240) DSCNT WHEEL DID NOT FULLY ENGAGE IN ALT HOLD AND ACFT DSNDED TO APPROX FL237. AUTOPLT DISCONNECT BY PF (CAPT) AND LEVELED BACK TO FL240 AFTER CALLED BY ATC. CONTRIBUTING FACTORS WERE HIGH WORKLOAD IN TSTM ACTIVITY WHILE TRYING TO DEVIATE TO ACCEPTABLE COURSE FOR ATC ARR REQUIREMENT AND ACFT SAFETY TO AVOID WX. VISUAL AND WX RADAR CONFIRMATION OF TSTMS NOT VISIBLE BY ATC RADAR ALSO CONTRIBUTED TO HIGH WORKLOAD DUE TO COM OR WX TO ATC BY CREW. CORRECTIVE ACTION: 1) REDUCE WORKLOAD ON BOTH FLC AND ATC BY IMPROVED WX RADAR CAPABILITY IN ACFT, 2) MORE RELIABLE AUTOPLT ALT HOLD CAPABILITY AT ATC, AND 3) INCREASED AWARENESS BY FLC OF ALT DURING HIGH WORKLOAD.
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.