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While deviating around thunderstorms near the airport, an air carrier flight crew inadvertently descended 1000 ft below their assigned altitude. The flight crew reports overreliance upon automation and a heading knob (similar shape) near the altitude select, as contributing factors.
| Attributes | |
| ACN | 340653 |
| Time | |
| Date | 199607 |
| Day | Tue |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | airport : okc |
| State Reference | OK |
| Altitude | msl bound lower : 5000 msl bound upper : 6000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | tracon : okc |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other Other |
| Flight Phase | descent : approach |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp pilot : commercial pilot : instrument |
| Experience | flight time last 90 days : 200 flight time total : 9000 flight time type : 4500 |
| ASRS Report | 340653 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : flight engineer pilot : commercial pilot : instrument pilot : cfi pilot : atp |
| Experience | flight time last 90 days : 200 flight time total : 12000 flight time type : 70 |
| ASRS Report | 340650 |
| Events | |
| Anomaly | altitude deviation : overshoot inflight encounter : weather 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:
Cleared with approach control to 6000 ft. Preoccupied with approach preparations and heavy thunderstorm activity just southeast of the airport. Noticed altitude of 5000 ft. We had no altitude warning alert. Altitude select window showed 8000 ft (previously set at 6000 ft). Climbed immediately back to 6000 ft. There was no traffic in the vicinity and no comment from approach. This deviation was caused by a busy approach complicated by thunderstorms nearby, and overreliance on autoplt and altitude alert to level us off at 6000 ft. One of us must have bumped altitude select window knob inadvertently and not noticed that it changed to 8000 ft. Supplemental information from acn 340650: heading select knob is in nearly the same position and feels nearly the same.
Original NASA ASRS Text
Title: WHILE DEVIATING AROUND TSTMS NEAR THE ARPT, AN ACR FLC INADVERTENTLY DSNDED 1000 FT BELOW THEIR ASSIGNED ALT. THE FLC RPTS OVERRELIANCE UPON AUTOMATION AND A HDG KNOB (SIMILAR SHAPE) NEAR THE ALT SELECT, AS CONTRIBUTING FACTORS.
Narrative: CLRED WITH APCH CTL TO 6000 FT. PREOCCUPIED WITH APCH PREPARATIONS AND HVY TSTM ACTIVITY JUST SE OF THE ARPT. NOTICED ALT OF 5000 FT. WE HAD NO ALT WARNING ALERT. ALT SELECT WINDOW SHOWED 8000 FT (PREVIOUSLY SET AT 6000 FT). CLBED IMMEDIATELY BACK TO 6000 FT. THERE WAS NO TFC IN THE VICINITY AND NO COMMENT FROM APCH. THIS DEV WAS CAUSED BY A BUSY APCH COMPLICATED BY TSTMS NEARBY, AND OVERRELIANCE ON AUTOPLT AND ALT ALERT TO LEVEL US OFF AT 6000 FT. ONE OF US MUST HAVE BUMPED ALT SELECT WINDOW KNOB INADVERTENTLY AND NOT NOTICED THAT IT CHANGED TO 8000 FT. SUPPLEMENTAL INFO FROM ACN 340650: HDG SELECT KNOB IS IN NEARLY THE SAME POS AND FEELS NEARLY THE SAME.
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.