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Approach controller letting small transport overtake another small transport had less than standard separation occur before visual separation applied.
| Attributes | |
| ACN | 164710 |
| Time | |
| Date | 199012 |
| Day | Fri |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : syr |
| State Reference | NY |
| Altitude | msl bound lower : 2800 msl bound upper : 3200 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : syr |
| Operator | general aviation : personal |
| Make Model Name | Small Transport |
| Flight Phase | descent : approach descent other landing other |
| Route In Use | approach : visual |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | general aviation : corporate |
| Make Model Name | Small Transport, Low Wing, 2 Turboprop Eng |
| Flight Phase | descent : approach descent other landing other |
| Route In Use | approach : visual |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : approach |
| Qualification | controller : radar |
| Experience | controller radar : 2 |
| ASRS Report | 164710 |
| Person 2 | |
| Affiliation | Other |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : instrument |
| Events | |
| Anomaly | conflict : nmac non adherence : published procedure non adherence : required legal separation |
| Independent Detector | other controllera |
| Resolutory Action | none taken : detected after the fact |
| Consequence | Other |
| Miss Distance | unspecified : 200 vertical : 0 |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
Small transport X instructed to descend from 3000' to 2000' on localizer with traffic advisory of small transport Y overtaking on localizer at 5000'. Small transport X started out of 3000' by mode C, small transport Y descended to 3000' about 3 mi in trail. At 1-1 1/2 mi apart mode indicated small transport X 2800' and small transport Y 3800'. ARTS IIIA coasted both targets prior to merge. Small transport X reported traffic in sight overhead and cleared visibility approach to follow small transport Y. When small transport Y 1 mi ahead told that small transport X had visibility sep and instructed to descend to 2000'. Targets cleared from coast to show mode C on small transport Y at 3100' and small transport X still at 2800'. Small transport Y reported field and cleared visibility approach. At T/D (small transport Y), small transport X 2 1/2 in trail. If ARTS IIIA had not coasted 1 1/2 mi prior to merge until 1 mi after target sep, the non descent of the small transport X would have been noticed and the small transport Y altitude corrected. While in coast, the controllers must rely on aircraft characteristics for standard descent of like types.
Original NASA ASRS Text
Title: APCH CTLR LETTING SMT OVERTAKE ANOTHER SMT HAD LESS THAN STANDARD SEPARATION OCCUR BEFORE VISUAL SEPARATION APPLIED.
Narrative: SMT X INSTRUCTED TO DSND FROM 3000' TO 2000' ON LOC WITH TFC ADVISORY OF SMT Y OVERTAKING ON LOC AT 5000'. SMT X STARTED OUT OF 3000' BY MODE C, SMT Y DSNDED TO 3000' ABOUT 3 MI IN TRAIL. AT 1-1 1/2 MI APART MODE INDICATED SMT X 2800' AND SMT Y 3800'. ARTS IIIA COASTED BOTH TARGETS PRIOR TO MERGE. SMT X RPTED TFC IN SIGHT OVERHEAD AND CLRED VIS APCH TO FOLLOW SMT Y. WHEN SMT Y 1 MI AHEAD TOLD THAT SMT X HAD VIS SEP AND INSTRUCTED TO DSND TO 2000'. TARGETS CLRED FROM COAST TO SHOW MODE C ON SMT Y AT 3100' AND SMT X STILL AT 2800'. SMT Y RPTED FIELD AND CLRED VIS APCH. AT T/D (SMT Y), SMT X 2 1/2 IN TRAIL. IF ARTS IIIA HAD NOT COASTED 1 1/2 MI PRIOR TO MERGE UNTIL 1 MI AFTER TARGET SEP, THE NON DSNT OF THE SMT X WOULD HAVE BEEN NOTICED AND THE SMT Y ALT CORRECTED. WHILE IN COAST, THE CTLRS MUST RELY ON ACFT CHARACTERISTICS FOR STANDARD DSNT OF LIKE TYPES.
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.