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37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
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An air carrier widebody transport flight crew finds that upon arming the approach mode, after receiving clearance approximately 15 NM of the airport, the aircraft turned to a course that paralleled the approach course without intercepting it. The flight crew waited and then armed the approach mode within 1 mi of the ILS and the aircraft then performed normally.
| Attributes | |
| ACN | 384614 |
| Time | |
| Date | 199710 |
| Day | Sun |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : mxp |
| State Reference | FO |
| Altitude | msl bound lower : 4000 msl bound upper : 4000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : mxp |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other Other |
| Flight Phase | descent : approach |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : flight engineer pilot : atp pilot : commercial |
| Experience | flight time last 90 days : 100 flight time total : 11000 flight time type : 100 |
| ASRS Report | 384614 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : commercial pilot : instrument |
| Events | |
| Anomaly | aircraft equipment problem : less severe other anomaly other other spatial deviation |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other flight crewa |
| Resolutory Action | other |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | other |
Narrative:
On heading 025 degrees and 4000 ft west of ILS runway 35R at mxp altitude and heading assigned by ATC to intercept ILS for CAT IIIB approach. Armed approach mode and autoplts approximately 3-5 mi west of localizer course and aircraft executed immediate left turn paralleling approach. Reengaged heading select and returned to intercept heading. Verified and positively idented that we had entered proper course, approach and frequency. All checked ok. Rearmed approach mode and autoplts and maneuver occurred again and aircraft started down (lost 300 ft). Disconnected autoplt selected heading select and manually returned to altitude and intercept heading. Waited till less than a mi from localizer course and rearmed approach mode and autoplts. Aircraft then executed normal CAT IIIB autoland approach. We were less than 15 mi radius from airport during entire incident. Map/localizer/GS indicators never corroborated we were on approach in first 2 instances. Related incident to outbound captain and he stated he'd had a similar experience, but no others have been reported before or since. Also heading bug slewed to inbound course as if localizer capture had occurred, even though localizer/GS needles were off scale. Had no indications of aircraft system malfunction, notified mxp station manager, who contacted italian aviation auths and they assured us ILS would be checked.
Original NASA ASRS Text
Title: AN ACR WDB FLC FINDS THAT UPON ARMING THE APCH MODE, AFTER RECEIVING CLRNC APPROX 15 NM OF THE ARPT, THE ACFT TURNED TO A COURSE THAT PARALLELED THE APCH COURSE WITHOUT INTERCEPTING IT. THE FLC WAITED AND THEN ARMED THE APCH MODE WITHIN 1 MI OF THE ILS AND THE ACFT THEN PERFORMED NORMALLY.
Narrative: ON HDG 025 DEGS AND 4000 FT W OF ILS RWY 35R AT MXP ALT AND HEADING ASSIGNED BY ATC TO INTERCEPT ILS FOR CAT IIIB APCH. ARMED APCH MODE AND AUTOPLTS APPROX 3-5 MI W OF LOC COURSE AND ACFT EXECUTED IMMEDIATE L TURN PARALLELING APCH. REENGAGED HEADING SELECT AND RETURNED TO INTERCEPT HEADING. VERIFIED AND POSITIVELY IDENTED THAT WE HAD ENTERED PROPER COURSE, APCH AND FREQ. ALL CHKED OK. REARMED APCH MODE AND AUTOPLTS AND MANEUVER OCCURRED AGAIN AND ACFT STARTED DOWN (LOST 300 FT). DISCONNECTED AUTOPLT SELECTED HEADING SELECT AND MANUALLY RETURNED TO ALT AND INTERCEPT HEADING. WAITED TILL LESS THAN A MI FROM LOC COURSE AND REARMED APCH MODE AND AUTOPLTS. ACFT THEN EXECUTED NORMAL CAT IIIB AUTOLAND APCH. WE WERE LESS THAN 15 MI RADIUS FROM ARPT DURING ENTIRE INCIDENT. MAP/LOC/GS INDICATORS NEVER CORROBORATED WE WERE ON APCH IN FIRST 2 INSTANCES. RELATED INCIDENT TO OUTBOUND CAPT AND HE STATED HE'D HAD A SIMILAR EXPERIENCE, BUT NO OTHERS HAVE BEEN RPTED BEFORE OR SINCE. ALSO HEADING BUG SLEWED TO INBOUND COURSE AS IF LOC CAPTURE HAD OCCURRED, EVEN THOUGH LOC/GS NEEDLES WERE OFF SCALE. HAD NO INDICATIONS OF ACFT SYS MALFUNCTION, NOTIFIED MXP STATION MGR, WHO CONTACTED ITALIAN AVIATION AUTHS AND THEY ASSURED US ILS WOULD BE CHKED.
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.