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An A300-600 experienced 2 momentary FMC position shifts while descending to mdsd's pirer intersection with the autoplt attempting to correct to the new invalid tracks.
| Attributes | |
| ACN | 676954 |
| Time | |
| Date | 200511 |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | intersection : pirer |
| State Reference | FO |
| Altitude | msl single value : 20000 |
| Environment | |
| Flight Conditions | VMC |
| Aircraft 1 | |
| Controlling Facilities | artcc : zsu.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | A300 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other |
| Flight Phase | descent : vacating altitude descent : approach |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| ASRS Report | 676954 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Events | |
| Anomaly | non adherence : company policies non adherence : far non adherence : published procedure non adherence : clearance other spatial deviation |
| Independent Detector | other flight crewa |
| Resolutory Action | flight crew : overcame equipment problem |
| Supplementary | |
| Problem Areas | Navigational Facility Aircraft |
| Primary Problem | Ambiguous |
Narrative:
During descent 30 DME north of pirer on approach to runway 35 mdsd passing about 20000 ft aircraft banked 30 degrees to the left. When immediately corrected back on course HSI showed a deviation 25 miles left of course. When direct to pirer selected again; aircraft again banked left when corrected again a 19 mile left of course deviation shown. Callback conversation with reporter revealed the following information: reporter stated that at the time these events occurred; the aircraft was flying a 'direct to' track to pirer on the FMS. He could not say for sure; but this could have been a map shift. He has heard of this happening before but is at a complete loss to explain why it occurred.
Original NASA ASRS Text
Title: AN A300-600 EXPERIENCED 2 MOMENTARY FMC POSITION SHIFTS WHILE DSNDING TO MDSD'S PIRER INTXN WITH THE AUTOPLT ATTEMPTING TO CORRECT TO THE NEW INVALID TRACKS.
Narrative: DURING DSCNT 30 DME N OF PIRER ON APCH TO RWY 35 MDSD PASSING ABOUT 20000 FT ACFT BANKED 30 DEGS TO THE L. WHEN IMMEDIATELY CORRECTED BACK ON COURSE HSI SHOWED A DEV 25 MILES L OF COURSE. WHEN DIRECT TO PIRER SELECTED AGAIN; ACFT AGAIN BANKED L WHEN CORRECTED AGAIN A 19 MILE L OF COURSE DEV SHOWN. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT AT THE TIME THESE EVENTS OCCURRED; THE ACFT WAS FLYING A 'DIRECT TO' TRACK TO PIRER ON THE FMS. HE COULD NOT SAY FOR SURE; BUT THIS COULD HAVE BEEN A MAP SHIFT. HE HAS HEARD OF THIS HAPPENING BEFORE BUT IS AT A COMPLETE LOSS TO EXPLAIN WHY IT OCCURRED.
Data retrieved from NASA's ASRS site as of January 2009 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.