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Medium large transport overshot a radial when FMC was slow to cope with a rapid increase in ground speed.
| Attributes | |
| ACN | 237183 |
| Time | |
| Date | 199303 |
| Day | Sat |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : sgd airport : sfo |
| State Reference | CA |
| Altitude | msl bound lower : 10000 msl bound upper : 10000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zoa |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Navigation In Use | Other |
| Flight Phase | descent other |
| Route In Use | arrival other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 200 flight time total : 16000 flight time type : 4500 |
| ASRS Report | 237183 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 210 flight time total : 20000 flight time type : 3000 |
| ASRS Report | 237292 |
| Events | |
| Anomaly | aircraft equipment problem : less severe non adherence : clearance other spatial deviation |
| Independent Detector | other flight crewa |
| Resolutory Action | flight crew : overcame equipment problem flight crew : returned to intended course or assigned course |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | Pilot Deviation |
Narrative:
Flying the locke 1 arrival into sfo after passing groan intersection, the FMC was very slow to turn to the locke intersection possibly due to a change in winds and a speed increase in the descent from 280 KTS to 320 KTS. Upon recognition of the problem we manually tuned scaggs VOR and idented the station and manually turned the aircraft to intercept the scaggs 107 degree radial. ATC inquired about our position and we advised that we were raw data for the intercept. With a change from headwinds to tailwinds and a substantial increase in airspeed the FMC computer has a difficult time in computing the correct turning rate (as do pilots).
Original NASA ASRS Text
Title: MLG OVERSHOT A RADIAL WHEN FMC WAS SLOW TO COPE WITH A RAPID INCREASE IN GND SPD.
Narrative: FLYING THE LOCKE 1 ARR INTO SFO AFTER PASSING GROAN INTXN, THE FMC WAS VERY SLOW TO TURN TO THE LOCKE INTXN POSSIBLY DUE TO A CHANGE IN WINDS AND A SPD INCREASE IN THE DSCNT FROM 280 KTS TO 320 KTS. UPON RECOGNITION OF THE PROB WE MANUALLY TUNED SCAGGS VOR AND IDENTED THE STATION AND MANUALLY TURNED THE ACFT TO INTERCEPT THE SCAGGS 107 DEG RADIAL. ATC INQUIRED ABOUT OUR POS AND WE ADVISED THAT WE WERE RAW DATA FOR THE INTERCEPT. WITH A CHANGE FROM HEADWINDS TO TAILWINDS AND A SUBSTANTIAL INCREASE IN AIRSPD THE FMC COMPUTER HAS A DIFFICULT TIME IN COMPUTING THE CORRECT TURNING RATE (AS DO PLTS).
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.