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37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
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Air carrier X had less than standard separation from small transport Y. Near midair collision. System error.
| Attributes | |
| ACN | 174740 |
| Time | |
| Date | 199103 |
| Day | Fri |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : tys |
| State Reference | TN |
| Altitude | msl bound lower : 4000 msl bound upper : 4000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | tracon : tys |
| Operator | common carrier : air carrier |
| Make Model Name | Light Transport, Low Wing, 2 Turboprop Eng |
| Flight Phase | descent other |
| Route In Use | enroute : on vectors |
| Flight Plan | IFR |
| Aircraft 2 | |
| Make Model Name | Small Transport, Low Wing, 2 Recip Eng |
| Flight Phase | climbout : intermediate altitude |
| Route In Use | enroute : on vectors |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : approach |
| Qualification | controller : radar |
| Experience | controller military : 3 controller radar : 1 |
| ASRS Report | 174740 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | conflict : nmac non adherence : required legal separation non adherence : published procedure |
| Independent Detector | other controllera |
| Resolutory Action | controller : issued new clearance other |
| Consequence | Other |
| Miss Distance | horizontal : 0 vertical : 500 |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
Air carrier X was on a heading for downwind at 7000' in compliance with the national 'keep 'em high' program. Departure small transport Y climbing to 6000' was assigned 6000' and an east heading for traffic. Using the diverging courses rule, I descended air carrier X early due to continuous complaint of moderate to severe turbulence and pilot request. Looking back I decided air carrier X would not have required sep and assigned him 5000'. At that time, small transport Y was out of 3200' climbing slowly. Air carrier X acknowledged 5000' and continued to 4000' before starting climb back to 5000'. Small transport Y was at 3700' and air carrier X mode C indicated 4000' when small transport Y saw air carrier X. Follow-up with separation requirements should have been made with small transport Y, by assigning a lower altitude after seeing air carrier X had descended below 5000'. Due to traffic and frequency congestion, as well as WX, this was not accomplished in a timely manner. Also, air carrier X was not made aware of necessity to maintain altitude, so he took his time about it!
Original NASA ASRS Text
Title: ACR X HAD LESS THAN STANDARD SEPARATION FROM SMT Y. NMAC. SYSTEM ERROR.
Narrative: ACR X WAS ON A HDG FOR DOWNWIND AT 7000' IN COMPLIANCE WITH THE NATL 'KEEP 'EM HIGH' PROGRAM. DEP SMT Y CLBING TO 6000' WAS ASSIGNED 6000' AND AN E HDG FOR TFC. USING THE DIVERGING COURSES RULE, I DSNDED ACR X EARLY DUE TO CONTINUOUS COMPLAINT OF MODERATE TO SEVERE TURB AND PLT REQUEST. LOOKING BACK I DECIDED ACR X WOULD NOT HAVE REQUIRED SEP AND ASSIGNED HIM 5000'. AT THAT TIME, SMT Y WAS OUT OF 3200' CLBING SLOWLY. ACR X ACKNOWLEDGED 5000' AND CONTINUED TO 4000' BEFORE STARTING CLB BACK TO 5000'. SMT Y WAS AT 3700' AND ACR X MODE C INDICATED 4000' WHEN SMT Y SAW ACR X. FOLLOW-UP WITH SEPARATION REQUIREMENTS SHOULD HAVE BEEN MADE WITH SMT Y, BY ASSIGNING A LOWER ALT AFTER SEEING ACR X HAD DSNDED BELOW 5000'. DUE TO TFC AND FREQ CONGESTION, AS WELL AS WX, THIS WAS NOT ACCOMPLISHED IN A TIMELY MANNER. ALSO, ACR X WAS NOT MADE AWARE OF NECESSITY TO MAINTAIN ALT, SO HE TOOK HIS TIME ABOUT IT!
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.