 |
37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
|
When their autoflight system; operating in VNAV path mode; failed to comply with the first two altitude constraints on the gibbz RNAV STAR to iad the flight crew of a B757-200 reverted to manual control on their descent path. The STAR had been properly programmed including descent wind forecasts and the autoflight system had conducted a previous RNAV STAR descent without incident.
| Attributes | |
| ACN | 1054397 |
| Time | |
| Date | 201212 |
| Local Time Of Day | 0001-0600 |
| Place | |
| Locale Reference | ZDC.ARTCC |
| State Reference | VA |
| Environment | |
| Flight Conditions | Mixed |
| Light | Night |
| Aircraft 1 | |
| Make Model Name | B757 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Descent |
| Route In Use | STAR GIBBZ ONE |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | FMS/FMC |
| Person 1 | |
| Function | First Officer Pilot Flying |
| Qualification | Flight Crew Flight Engineer Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine |
| Experience | Flight Crew Last 90 Days 160 Flight Crew Total 11400 Flight Crew Type 4500 |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe Deviation - Altitude Crossing Restriction Not Met Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy |
Narrative:
We were cleared to descend via the gibbz RNAV STAR to iad. We started the arrival in VNAV path allowing the FMC to calculate our vertical navigation. The airplane started down on VNAV path; however after looking at our distance and altitude we were going to cross jimve intersection very high; probably 2;000 ft high. I disconnected the autopilot and immediately started a steeper descent with speed brakes deployed. Despite our effort we crossed jimve 600 ft high.the same occurred at the next waypoint on the arrival; VNAV path was calculating a high crossing again. We discontinued VNAV and reverted to manual vertical navigation. The FMC had been programmed correctly and wind information input. We had flown this same aircraft on a previous leg that same day and no problems occurred on a previous RNAV arrival. The remainder of the flight was normal.
Original NASA ASRS Text
Title: When their autoflight system; operating in VNAV PATH mode; failed to comply with the first two altitude constraints on the GIBBZ RNAV STAR to IAD the flight crew of a B757-200 reverted to manual control on their descent path. The STAR had been properly programmed including descent wind forecasts and the autoflight system had conducted a previous RNAV STAR descent without incident.
Narrative: We were cleared to descend via the GIBBZ RNAV STAR to IAD. We started the arrival in VNAV PATH allowing the FMC to calculate our vertical navigation. The airplane started down on VNAV PATH; however after looking at our distance and altitude we were going to cross JIMVE Intersection very high; probably 2;000 FT high. I disconnected the autopilot and immediately started a steeper descent with speed brakes deployed. Despite our effort we crossed JIMVE 600 FT high.The same occurred at the next waypoint on the arrival; VNAV path was calculating a high crossing again. We discontinued VNAV and reverted to manual vertical navigation. The FMC had been programmed correctly and wind information input. We had flown this same aircraft on a previous leg that same day and no problems occurred on a previous RNAV arrival. The remainder of the flight was normal.
Data retrieved from NASA's ASRS site as of July 2013 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.