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Less than standard separation when approach controller failed to apply visual separation and issue approach clearance before aircraft on converging courses conflicted at same altitude.
| Attributes | |
| ACN | 93408 |
| Time | |
| Date | 198808 |
| Day | Sun |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | airport : slc |
| State Reference | UT |
| Altitude | msl bound lower : 7000 msl bound upper : 7000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Dusk |
| Aircraft 1 | |
| Controlling Facilities | tracon : slc |
| Operator | common carrier : air carrier |
| Make Model Name | Large Transport, Low Wing, 3 Turbojet Eng |
| Flight Phase | descent : approach descent other |
| Route In Use | approach : visual |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | common carrier : air carrier |
| Make Model Name | Large Transport, Low Wing, 2 Turbojet Eng |
| Navigation In Use | Other Other |
| Flight Phase | cruise other descent : approach |
| Route In Use | approach : visual |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : flight engineer pilot : atp |
| Experience | flight time last 90 days : 200 flight time total : 5000 flight time type : 350 |
| ASRS Report | 93408 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | conflict : airborne less severe non adherence : required legal separation |
| Independent Detector | other flight crewa |
| Resolutory Action | controller : issued new clearance flight crew : took evasive action none taken : detected after the fact |
| Consequence | Other |
| Miss Distance | horizontal : 1300 vertical : 0 |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
Our flight, large transport X, was on left parallel downwind to runway 24L at slc. We were cleared from 9000 to 7000', and a left turn from assigned heading of 155 degrees to 070 degrees. In the descent we were cleared to 6500'. All 3 crewmembers noticed an aircraft approaching from the south and made comments as to it possibly being conflicting traffic. We were unable to communication with approach because of frequency congestion. ATC gave us no change of heading or instructions to intercept the localizer. The other aircraft, large transport Y, appeared to be at our altitude as we approached 7000' in our descent to 6500'. It also became apparent that we were on a near perpendicular collision course (no change in relative bearing) with latitude sep decreasing very rapidly. Large transport Y, by this time, had managed to alert approach, who gave them a turn to 020 degrees. We were now below 7000' and continued our turn beyond 070 degrees to assure sep. ATC then cleared us for visual to runway 34L, where we landed west/O incident after correcting back to the west. Large transport Y landed runway 34R after we turned off. Upon talking to large transport Y's captain on the ground, we found that although cleared to 7000', ATC thought he to be at 8000'. At the time of this report, I haven't found why we weren't cleared for something other than 070 degree heading. Although at no time do I feel we were less than 500' horizontal, our convergence rate would have reduced to that in a few seconds. I would estimate 0' horizontal would have occurred in approximately 5 seconds had there been no turns. Slc runway 34's have extended centerlines that converge somewhere around the OM. There is an 05 degree (if memory serves) difference in magnetic runway heading. Perhaps a charted visual to runway 34R with an offset final is needed. This wouldn't have changed our situation (an ATC problem), but may change one in the future.
Original NASA ASRS Text
Title: LESS THAN STANDARD SEPARATION WHEN APCH CTLR FAILED TO APPLY VISUAL SEPARATION AND ISSUE APCH CLRNC BEFORE ACFT ON CONVERGING COURSES CONFLICTED AT SAME ALT.
Narrative: OUR FLT, LGT X, WAS ON LEFT PARALLEL DOWNWIND TO RWY 24L AT SLC. WE WERE CLRED FROM 9000 TO 7000', AND A LEFT TURN FROM ASSIGNED HDG OF 155 DEGS TO 070 DEGS. IN THE DSCNT WE WERE CLRED TO 6500'. ALL 3 CREWMEMBERS NOTICED AN ACFT APCHING FROM THE S AND MADE COMMENTS AS TO IT POSSIBLY BEING CONFLICTING TFC. WE WERE UNABLE TO COM WITH APCH BECAUSE OF FREQ CONGESTION. ATC GAVE US NO CHANGE OF HDG OR INSTRUCTIONS TO INTERCEPT THE LOC. THE OTHER ACFT, LGT Y, APPEARED TO BE AT OUR ALT AS WE APCHED 7000' IN OUR DSCNT TO 6500'. IT ALSO BECAME APPARENT THAT WE WERE ON A NEAR PERPENDICULAR COLLISION COURSE (NO CHANGE IN RELATIVE BEARING) WITH LAT SEP DECREASING VERY RAPIDLY. LGT Y, BY THIS TIME, HAD MANAGED TO ALERT APCH, WHO GAVE THEM A TURN TO 020 DEGS. WE WERE NOW BELOW 7000' AND CONTINUED OUR TURN BEYOND 070 DEGS TO ASSURE SEP. ATC THEN CLRED US FOR VISUAL TO RWY 34L, WHERE WE LANDED W/O INCIDENT AFTER CORRECTING BACK TO THE W. LGT Y LANDED RWY 34R AFTER WE TURNED OFF. UPON TALKING TO LGT Y'S CAPT ON THE GND, WE FOUND THAT ALTHOUGH CLRED TO 7000', ATC THOUGHT HE TO BE AT 8000'. AT THE TIME OF THIS RPT, I HAVEN'T FOUND WHY WE WEREN'T CLRED FOR SOMETHING OTHER THAN 070 DEG HDG. ALTHOUGH AT NO TIME DO I FEEL WE WERE LESS THAN 500' HORIZ, OUR CONVERGENCE RATE WOULD HAVE REDUCED TO THAT IN A FEW SECS. I WOULD ESTIMATE 0' HORIZ WOULD HAVE OCCURRED IN APPROX 5 SECS HAD THERE BEEN NO TURNS. SLC RWY 34'S HAVE EXTENDED CENTERLINES THAT CONVERGE SOMEWHERE AROUND THE OM. THERE IS AN 05 DEG (IF MEMORY SERVES) DIFFERENCE IN MAGNETIC RWY HDG. PERHAPS A CHARTED VISUAL TO RWY 34R WITH AN OFFSET FINAL IS NEEDED. THIS WOULDN'T HAVE CHANGED OUR SITUATION (AN ATC PROB), BUT MAY CHANGE ONE IN THE FUTURE.
Data retrieved from NASA's ASRS site as of August 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.