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An air carrier DC9 flight crew report that the first officer's attitude gyroscope was intermittently failing and while on autoplt caused the aircraft to make an inadvertent descent. The aircraft was recovered manually.
| Attributes | |
| ACN | 378420 |
| Time | |
| Date | 199708 |
| Day | Fri |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : mmj airport : pit |
| State Reference | PA |
| Altitude | msl bound lower : 5725 msl bound upper : 6000 |
| Environment | |
| Flight Conditions | Mixed |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : pit |
| Operator | common carrier : air carrier |
| Make Model Name | DC-9 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise other descent : approach |
| Route In Use | enroute : on vectors |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 60 flight time total : 10000 flight time type : 3000 |
| ASRS Report | 378420 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance non adherence : far other anomaly |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other flight crewa |
| Resolutory Action | flight crew : returned to intended course or assigned course flight crew : regained aircraft control |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | other |
Narrative:
Problem: first officer's gyroscope partially (intermittent) inoperative (autoplt received input from gyroscope). During approach inbound direct to montour VOR at 6000 ft, given a turn for downwind to runway 28R. While on autoplt, the aircraft descended approximately 250 to 275 ft before being overridden manually. Nothing was said by ATC (approach), there was nothing on TCASII and no other traffic was noted in the area. The captain corrected back to 6000 ft and we proceeded to land with no further incident. Avionics replaced first officer's gyroscope and a related box underneath.
Original NASA ASRS Text
Title: AN ACR DC9 FLC RPT THAT THE FO'S ATTITUDE GYROSCOPE WAS INTERMITTENTLY FAILING AND WHILE ON AUTOPLT CAUSED THE ACFT TO MAKE AN INADVERTENT DSCNT. THE ACFT WAS RECOVERED MANUALLY.
Narrative: PROB: FO'S GYROSCOPE PARTIALLY (INTERMITTENT) INOP (AUTOPLT RECEIVED INPUT FROM GYROSCOPE). DURING APCH INBOUND DIRECT TO MONTOUR VOR AT 6000 FT, GIVEN A TURN FOR DOWNWIND TO RWY 28R. WHILE ON AUTOPLT, THE ACFT DSNDED APPROX 250 TO 275 FT BEFORE BEING OVERRIDDEN MANUALLY. NOTHING WAS SAID BY ATC (APCH), THERE WAS NOTHING ON TCASII AND NO OTHER TFC WAS NOTED IN THE AREA. THE CAPT CORRECTED BACK TO 6000 FT AND WE PROCEEDED TO LAND WITH NO FURTHER INCIDENT. AVIONICS REPLACED FO'S GYROSCOPE AND A RELATED BOX UNDERNEATH.
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.