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Flight crew of medium large transport on approach used TCAS to determine separation from VFR traffic below the overcast.
| Attributes | |
| ACN | 183766 |
| Time | |
| Date | 199107 |
| Day | Wed |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : sjc |
| State Reference | CA |
| Altitude | msl bound lower : 2000 msl bound upper : 2000 |
| Environment | |
| Flight Conditions | Mixed |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tower : sjc |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Navigation In Use | Other Other |
| Flight Phase | descent : approach descent other |
| Route In Use | arrival other |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | other |
| Make Model Name | Small Aircraft, High Wing, 1 Eng, Fixed Gear |
| Flight Phase | descent : approach landing other |
| Flight Plan | None |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : commercial pilot : instrument pilot : cfi pilot : atp |
| Experience | flight time total : 11000 |
| ASRS Report | 183766 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : commercial pilot : instrument pilot : atp |
| Events | |
| Anomaly | conflict : airborne less severe other anomaly other |
| Independent Detector | other flight crewa |
| Resolutory Action | flight crew : took evasive action |
| Consequence | Other |
| Miss Distance | horizontal : 500 vertical : 100 |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | other |
| Situations | |
| ATC Facility | procedure or policy : unspecified |
Narrative:
Flight from ont to sjc was cleared straight in ILS 30L at sjc. WX was 1200 ft overcast, tops about 2500 ft and 10 mi visibility. Prior to the OM and above the overcast we were told there was a light single engine plane on right base for 30R (VFR) and his altitude was 1000 ft. Because we were on top we obviously didn't see him. Our TCAS was in the traffic advisory mode because of our low altitude at a busy airport. Inside the OM and in the overcast we noticed the light plane on our TCAS, 12:30 and 800 below us (approximately). Simultaneously with the TCAS traffic alert we deviated left of localizer and above GS to gain separation. We then broke out of the overcast abeam and to the left of the other aircraft. Too close for comfort. We then landed normally. Had we not had a TCAS and been slightly left of localizer a collision would have occurred. The parallel runways at sjc are too close for these kinds of parallel approachs. Also because of a one runway turbojet operation the airport is always saturated. I think they are pushing the limits. Also why was the VFR aircraft that far out on final approach? A close in base to final well below the overcast might have been more acceptable.
Original NASA ASRS Text
Title: FLC OF MLG ON APCH USED TCAS TO DETERMINE SEPARATION FROM VFR TFC BELOW THE OVERCAST.
Narrative: FLT FROM ONT TO SJC WAS CLRED STRAIGHT IN ILS 30L AT SJC. WX WAS 1200 FT OVERCAST, TOPS ABOUT 2500 FT AND 10 MI VISIBILITY. PRIOR TO THE OM AND ABOVE THE OVERCAST WE WERE TOLD THERE WAS A LIGHT SINGLE ENG PLANE ON R BASE FOR 30R (VFR) AND HIS ALT WAS 1000 FT. BECAUSE WE WERE ON TOP WE OBVIOUSLY DIDN'T SEE HIM. OUR TCAS WAS IN THE TFC ADVISORY MODE BECAUSE OF OUR LOW ALT AT A BUSY ARPT. INSIDE THE OM AND IN THE OVERCAST WE NOTICED THE LIGHT PLANE ON OUR TCAS, 12:30 AND 800 BELOW US (APPROX). SIMULTANEOUSLY WITH THE TCAS TFC ALERT WE DEVIATED L OF LOC AND ABOVE GS TO GAIN SEPARATION. WE THEN BROKE OUT OF THE OVERCAST ABEAM AND TO THE L OF THE OTHER ACFT. TOO CLOSE FOR COMFORT. WE THEN LANDED NORMALLY. HAD WE NOT HAD A TCAS AND BEEN SLIGHTLY L OF LOC A COLLISION WOULD HAVE OCCURRED. THE PARALLEL RWYS AT SJC ARE TOO CLOSE FOR THESE KINDS OF PARALLEL APCHS. ALSO BECAUSE OF A ONE RWY TURBOJET OP THE ARPT IS ALWAYS SATURATED. I THINK THEY ARE PUSHING THE LIMITS. ALSO WHY WAS THE VFR ACFT THAT FAR OUT ON FINAL APCH? A CLOSE IN BASE TO FINAL WELL BELOW THE OVERCAST MIGHT HAVE BEEN MORE ACCEPTABLE.
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.