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B737 captain detailed problems associated with a dca RNAV arrival relative to FMC capabilities and increased workload imposed on flight crews.
| Attributes | |
| ACN | 1411417 |
| Time | |
| Date | 201612 |
| Local Time Of Day | 1801-2400 |
| Place | |
| Locale Reference | DCA.Airport |
| State Reference | DC |
| Aircraft 1 | |
| Make Model Name | B737 Next Generation Undifferentiated |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Initial Approach |
| Route In Use | STAR CAPSS TWO |
| Flight Plan | IFR |
| Person 1 | |
| Function | Captain |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe Deviation - Altitude Crossing Restriction Not Met Deviation - Procedural Published Material / Policy |
Narrative:
Descending on the CAPSS2 RNAV arrival into dca. Airplane crossed hoyas about 400 feet high. This particular STAR gave the FMC a lot of problems. Multiple alerts displayed; unnecessary airspeed changes and finally an impossible descent rate to make the hoyas altitude restriction were all part of the descent from waves. Between hoyas and capss the FMC reverted to VNAV speed and simply left the path. The VNAV path alternated between an add power segment back to a flight idle; speed brakes segment several times. A better solution for the FMC is to simply average the path. Is this RNAV arrival too complex for the FMC brain? The promise of a reduced cockpit workload by using VNAV/FMC RNAV descents is elusive. Cockpit workload in this situation is increased due to crews having to constantly monitor; intervene; and fix VNAV issues.
Original NASA ASRS Text
Title: B737 Captain detailed problems associated with a DCA RNAV arrival relative to FMC capabilities and increased workload imposed on flight crews.
Narrative: Descending on the CAPSS2 RNAV arrival into DCA. Airplane crossed HOYAS about 400 feet high. This particular STAR gave the FMC a lot of problems. Multiple alerts displayed; unnecessary airspeed changes and finally an impossible descent rate to make the HOYAS altitude restriction were all part of the descent from WAVES. Between HOYAS and CAPSS the FMC reverted to VNAV speed and simply left the path. The VNAV path alternated between an add power segment back to a flight idle; speed brakes segment several times. A better solution for the FMC is to simply average the path. Is this RNAV arrival too complex for the FMC brain? The promise of a reduced cockpit workload by using VNAV/FMC RNAV descents is elusive. Cockpit workload in this situation is increased due to crews having to constantly monitor; intervene; and fix VNAV issues.
Data retrieved from NASA's ASRS site 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.