 |
37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
|
Aircraft descends 1000 ft without a command to do so. Aircraft was flown on autoplt at the time. Apparently, aircraft followed unreliable instrument data.
| Attributes | |
| ACN | 274809 |
| Time | |
| Date | 199406 |
| Day | Sun |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : adm |
| State Reference | OK |
| Altitude | msl bound lower : 21000 msl bound upper : 22000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zfw |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other Other |
| Flight Phase | cruise other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain instruction : trainee |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 70 flight time total : 4800 flight time type : 200 |
| ASRS Report | 274814 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer observation : company check pilot oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 150 flight time total : 13300 flight time type : 150 |
| ASRS Report | 274814 |
| Events | |
| Anomaly | aircraft equipment problem : critical altitude deviation : excursion from assigned altitude non adherence : clearance |
| Independent Detector | other flight crewa |
| Resolutory Action | aircraft : equipment problem dissipated flight crew : returned to intended course or assigned course |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | Pilot Deviation other |
Narrative:
In cruise at FL220 with captain's 'a' autoplt engaged, the aircraft began an uncommanded descent. The captain's altitude indicator and vertical speed indicator became erratic, and the autoplt followed the erratic altitude. There was no altitude warning horn nor off flags. The autoplt and autothrottles were disconnected and recovery made back to FL220. After a descent to FL210 using the copilot's and standby instruments, which were operating normally. ZFW was immediately called and advised of the situation. Center appeared to be unaware of the altitude deviation. There appeared to be no conflict with other aircraft. Supplemental information from acn 274814: the aircraft was flown from the first officer flight instruments. No actual altitude deviation occurred. There were no conflicts. After several mins, the captain's flight instruments returned to normal.
Original NASA ASRS Text
Title: ACFT DSNDS 1000 FT WITHOUT A COMMAND TO DO SO. ACFT WAS FLOWN ON AUTOPLT AT THE TIME. APPARENTLY, ACFT FOLLOWED UNRELIABLE INST DATA.
Narrative: IN CRUISE AT FL220 WITH CAPT'S 'A' AUTOPLT ENGAGED, THE ACFT BEGAN AN UNCOMMANDED DSCNT. THE CAPT'S ALT INDICATOR AND VERT SPD INDICATOR BECAME ERRATIC, AND THE AUTOPLT FOLLOWED THE ERRATIC ALT. THERE WAS NO ALT WARNING HORN NOR OFF FLAGS. THE AUTOPLT AND AUTOTHROTTLES WERE DISCONNECTED AND RECOVERY MADE BACK TO FL220. AFTER A DSCNT TO FL210 USING THE COPLT'S AND STANDBY INSTS, WHICH WERE OPERATING NORMALLY. ZFW WAS IMMEDIATELY CALLED AND ADVISED OF THE SIT. CTR APPEARED TO BE UNAWARE OF THE ALTDEV. THERE APPEARED TO BE NO CONFLICT WITH OTHER ACFT. SUPPLEMENTAL INFO FROM ACN 274814: THE ACFT WAS FLOWN FROM THE FO FLT INSTS. NO ACTUAL ALTDEV OCCURRED. THERE WERE NO CONFLICTS. AFTER SEVERAL MINS, THE CAPT'S FLT INSTS RETURNED TO NORMAL.
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.