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Captain of a DC9 noticed aircraft altitude 300 ft low shortly after leveloff at an intermediate descent altitude on arrival STAR and immediately corrected back. Subsequently found the aircraft 300 ft too high. After making the next correction more slowly, the aircraft remained on assigned altitude until landing.
| Attributes | |
| ACN | 429220 |
| Time | |
| Date | 199902 |
| Day | Sun |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | navaid : smo.vor |
| State Reference | CA |
| Altitude | msl bound lower : 6700 msl bound upper : 7300 |
| Environment | |
| Flight Conditions | Mixed |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | tracon : sct.tracon |
| Operator | common carrier : air carrier |
| Make Model Name | DC-9 10 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other vortac |
| Flight Phase | descent : intermediate altitude |
| Route In Use | arrival star : flm.moor3 |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp pilot : cfi |
| Experience | flight time last 90 days : 110 flight time total : 9600 flight time type : 2300 |
| ASRS Report | 729220 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : multi engine pilot : instrument pilot : commercial |
| Events | |
| Anomaly | aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance |
| Independent Detector | other flight crewa |
| Resolutory Action | flight crew : returned to original clearance |
| Supplementary | |
| Problem Areas | Aircraft |
| Primary Problem | Aircraft |
| Air Traffic Incident | Pilot Deviation |
Narrative:
We were cleared to descend and maintain 7000 ft. We approached 7000 ft as we made the turn to smo VOR. As I leveled off slightly below 7000 ft, I noticed the altimeter jump to about 6700 ft. I overcorrected and suddenly the altimeter jumped to about 7300 ft. Using more gradual control inputs, I eased the aircraft down to 7000 ft. The rest of the flight was uneventful. After parking at lax, we noticed the instrument vibrator circuit breaker had popped and would not reset, thus accounting for the oversensitive or jumpy altimeter indications.
Original NASA ASRS Text
Title: CAPT OF A DC9 NOTICED ACFT ALT 300 FT LOW SHORTLY AFTER LEVELOFF AT AN INTERMEDIATE DSCNT ALT ON ARR STAR AND IMMEDIATELY CORRECTED BACK. SUBSEQUENTLY FOUND THE ACFT 300 FT TOO HIGH. AFTER MAKING THE NEXT CORRECTION MORE SLOWLY, THE ACFT REMAINED ON ASSIGNED ALT UNTIL LNDG.
Narrative: WE WERE CLRED TO DSND AND MAINTAIN 7000 FT. WE APCHED 7000 FT AS WE MADE THE TURN TO SMO VOR. AS I LEVELED OFF SLIGHTLY BELOW 7000 FT, I NOTICED THE ALTIMETER JUMP TO ABOUT 6700 FT. I OVERCORRECTED AND SUDDENLY THE ALTIMETER JUMPED TO ABOUT 7300 FT. USING MORE GRADUAL CTL INPUTS, I EASED THE ACFT DOWN TO 7000 FT. THE REST OF THE FLT WAS UNEVENTFUL. AFTER PARKING AT LAX, WE NOTICED THE INST VIBRATOR CIRCUIT BREAKER HAD POPPED AND WOULD NOT RESET, THUS ACCOUNTING FOR THE OVERSENSITIVE OR JUMPY ALTIMETER INDICATIONS.
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.