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B737 crew wound up navigating direct to a VOR rather than flying the airway radials. This placed them about 5 mi south of the airway.
| Attributes | |
| ACN | 418770 |
| Time | |
| Date | 199810 |
| Day | Fri |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : pmm |
| State Reference | MI |
| Altitude | msl bound lower : 28000 msl bound upper : 28000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | B737 Undifferentiated or Other Model |
| Navigation In Use | Other |
| Flight Phase | cruise other |
| Route In Use | arrival other arrival star : star |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Experience | flight time last 90 days : 210 flight time total : 9500 flight time type : 700 |
| ASRS Report | 418770 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : commercial |
| Events | |
| Anomaly | non adherence : clearance other spatial deviation |
| Independent Detector | other controllera other flight crewa |
| Consequence | Other |
| Supplementary | |
| Air Traffic Incident | Pilot Deviation |
Narrative:
En route from bos to ord on LNAV, we were filed on pmm arrival fnt transition to ord. At FL280, approximately 60 mi northeast of pmm, the controller asked if we were direct pmm or on airway. We replied on airway, as that is what we were cleared. But in checking the FMC, we were actually direct to pmm, approximately 5 mi south of the airway. Neither copilot nor I knew how this happened. We discussed FMC entries and neither remembered changing the course, only the cruise altitude. We had descended from FL350 to FL280 due to turbulence. I assume the FMC did not malfunction but that somehow we programmed the FMC wrong to start with or altered it en route without realizing it.
Original NASA ASRS Text
Title: B737 CREW WOUND UP NAVING DIRECT TO A VOR RATHER THAN FLYING THE AIRWAY RADIALS. THIS PLACED THEM ABOUT 5 MI S OF THE AIRWAY.
Narrative: ENRTE FROM BOS TO ORD ON LNAV, WE WERE FILED ON PMM ARR FNT TRANSITION TO ORD. AT FL280, APPROX 60 MI NE OF PMM, THE CTLR ASKED IF WE WERE DIRECT PMM OR ON AIRWAY. WE REPLIED ON AIRWAY, AS THAT IS WHAT WE WERE CLRED. BUT IN CHKING THE FMC, WE WERE ACTUALLY DIRECT TO PMM, APPROX 5 MI S OF THE AIRWAY. NEITHER COPLT NOR I KNEW HOW THIS HAPPENED. WE DISCUSSED FMC ENTRIES AND NEITHER REMEMBERED CHANGING THE COURSE, ONLY THE CRUISE ALT. WE HAD DSNDED FROM FL350 TO FL280 DUE TO TURB. I ASSUME THE FMC DID NOT MALFUNCTION BUT THAT SOMEHOW WE PROGRAMMED THE FMC WRONG TO START WITH OR ALTERED IT ENRTE WITHOUT REALIZING IT.
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.