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An MD80 in cruise at FL310 had right autoplt disconnect with first officer's momentary flags in the airspeed indicator.
| Attributes | |
| ACN | 604265 |
| Time | |
| Date | 200401 |
| Day | Mon |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : zzz.artcc |
| State Reference | US |
| Altitude | msl bound lower : 31000 msl bound upper : 31400 |
| Environment | |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | tracon : zzz.tracon tower : svmi.tower |
| Operator | common carrier : air carrier |
| Make Model Name | MD-80 Super 80 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain |
| Qualification | pilot : atp |
| ASRS Report | 604265 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : multi engine pilot : commercial pilot : instrument |
| ASRS Report | 604262 |
| Events | |
| Anomaly | aircraft equipment problem : critical altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : fo a/s + ivsi flag warning other flight crewa other flight crewb |
| Resolutory Action | controller : provided flight assist flight crew : returned to assigned altitude flight crew : became reoriented other |
| Consequence | other other |
| Supplementary | |
| Problem Areas | Aircraft Flight Crew Human Performance |
| Primary Problem | Aircraft |
Narrative:
In cruise at FL310, autoplt #2 disconnected. First officer (PF) had momentary flags in airspeed indicator. His altimeter and vsi were showing a descent while mine was showing a climb. ATC was notified immediately. During recognition and analysis of problem, maximum altitude gain was 300-400 ft. ATC advised us there was no traffic conflict. Callback conversation with reporter revealed the following information: the reporter stated the first indication of a problem was the right autoplt tripped off and then momentary flags appeared in the first officer's airspeed indicator. The reporter said it was noted the first officer's instruments indicated a slight descent while the captain's instruments were showing a climb. The reporter stated ATC was advised of the altitude excursion of 400 ft. Supplemental information from acn 604262: I (the first officer) was flying. The dfgc switch was on #2 and we were in navigation track and altitude hold modes. I took over manually. ATC was immediately notified of the problem and queried about what they showed our altitude to be. This information, along with the standby instruments confirmed that the first officer's flight instruments were erratic and unreliable, and now the first officer's 'off' flags were beginning to appear intermittently. It was later diagnosed that the aircraft was experiencing a failure of the #2 central air data computer. The flight was completed with both the captain's and first officer's instruments operating off of the #1 central air data computer. Once stabilized back at FL310, ATC was queried and responded that traffic separation was never jeopardized.
Original NASA ASRS Text
Title: AN MD80 IN CRUISE AT FL310 HAD R AUTOPLT DISCONNECT WITH FO'S MOMENTARY FLAGS IN THE AIRSPD INDICATOR.
Narrative: IN CRUISE AT FL310, AUTOPLT #2 DISCONNECTED. FO (PF) HAD MOMENTARY FLAGS IN AIRSPD INDICATOR. HIS ALTIMETER AND VSI WERE SHOWING A DSCNT WHILE MINE WAS SHOWING A CLB. ATC WAS NOTIFIED IMMEDIATELY. DURING RECOGNITION AND ANALYSIS OF PROB, MAX ALT GAIN WAS 300-400 FT. ATC ADVISED US THERE WAS NO TFC CONFLICT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE FIRST INDICATION OF A PROB WAS THE R AUTOPLT TRIPPED OFF AND THEN MOMENTARY FLAGS APPEARED IN THE FO'S AIRSPD INDICATOR. THE RPTR SAID IT WAS NOTED THE FO'S INSTS INDICATED A SLIGHT DSCNT WHILE THE CAPT'S INSTS WERE SHOWING A CLB. THE RPTR STATED ATC WAS ADVISED OF THE ALT EXCURSION OF 400 FT. SUPPLEMENTAL INFO FROM ACN 604262: I (THE FO) WAS FLYING. THE DFGC SWITCH WAS ON #2 AND WE WERE IN NAV TRACK AND ALT HOLD MODES. I TOOK OVER MANUALLY. ATC WAS IMMEDIATELY NOTIFIED OF THE PROB AND QUERIED ABOUT WHAT THEY SHOWED OUR ALT TO BE. THIS INFO, ALONG WITH THE STANDBY INSTS CONFIRMED THAT THE FO'S FLT INSTS WERE ERRATIC AND UNRELIABLE, AND NOW THE FO'S 'OFF' FLAGS WERE BEGINNING TO APPEAR INTERMITTENTLY. IT WAS LATER DIAGNOSED THAT THE ACFT WAS EXPERIENCING A FAILURE OF THE #2 CENTRAL AIR DATA COMPUTER. THE FLT WAS COMPLETED WITH BOTH THE CAPT'S AND FO'S INSTS OPERATING OFF OF THE #1 CENTRAL AIR DATA COMPUTER. ONCE STABILIZED BACK AT FL310, ATC WAS QUERIED AND RESPONDED THAT TFC SEPARATION WAS NEVER JEOPARDIZED.
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.