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A B757 flight crew turns off autoplt to leveloff due to high rate of descent, resulting in an altitude overshoot of 300-400 ft.
| Attributes | |
| ACN | 587085 |
| Time | |
| Date | 200307 |
| Day | Thu |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | navaid : psp.vortac |
| State Reference | CA |
| Altitude | msl bound lower : 23600 msl bound upper : 24000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zla.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B757 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other other vortac |
| Flight Phase | descent : intermediate altitude |
| Route In Use | arrival star : n/s |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 185 flight time total : 11000 flight time type : 1400 |
| ASRS Report | 587085 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Events | |
| Anomaly | altitude deviation : overshoot non adherence : clearance non adherence : far |
| Independent Detector | other flight crewa |
| Resolutory Action | flight crew : returned to assigned altitude |
| Supplementary | |
| Problem Areas | Flight Crew Human Performance Aircraft |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
During descent into sna, autoplt was struggling to stay on VNAV path descent to cross palm springs VOR at FL240. Captain flying, needed speed brakes and manually closed throttles to idle power to prevent an overspd. First officer and I noticed 4000 FPM descent when he called one thousand feet to go. At 500 ft prior to assigned altitude, the autoplt was disconnected and a manual leveloff was accomplished. No other aircraft in vicinity and no call from ZLA. Smoothly stopped descent at FL237 to FL236, and returned to assigned altitude of FL240. Lessons learned: 1) VNAV is not full proof and 2) will not always hack a large descent or climb, 3) always check throttles at idle in VNAV path descent and throttle hold even though the magenta football is on target, and 4) always check vertical speed when calling out 1000 ft to leveloff.
Original NASA ASRS Text
Title: A B757 FLT CREW TURNS OFF AUTOPLT TO LEVELOFF DUE TO HIGH RATE OF DSCNT, RESULTING IN AN ALT OVERSHOOT OF 300-400 FT.
Narrative: DURING DSCNT INTO SNA, AUTOPLT WAS STRUGGLING TO STAY ON VNAV PATH DSCNT TO CROSS PALM SPRINGS VOR AT FL240. CAPT FLYING, NEEDED SPD BRAKES AND MANUALLY CLOSED THROTTLES TO IDLE PWR TO PREVENT AN OVERSPD. FO AND I NOTICED 4000 FPM DSCNT WHEN HE CALLED ONE THOUSAND FEET TO GO. AT 500 FT PRIOR TO ASSIGNED ALT, THE AUTOPLT WAS DISCONNECTED AND A MANUAL LEVELOFF WAS ACCOMPLISHED. NO OTHER ACFT IN VICINITY AND NO CALL FROM ZLA. SMOOTHLY STOPPED DSCNT AT FL237 TO FL236, AND RETURNED TO ASSIGNED ALT OF FL240. LESSONS LEARNED: 1) VNAV IS NOT FULL PROOF AND 2) WILL NOT ALWAYS HACK A LARGE DSCNT OR CLB, 3) ALWAYS CHK THROTTLES AT IDLE IN VNAV PATH DSCNT AND THROTTLE HOLD EVEN THOUGH THE MAGENTA FOOTBALL IS ON TARGET, AND 4) ALWAYS CHK VERT SPD WHEN CALLING OUT 1000 FT TO LEVELOFF.
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.